JP6925249B2 - Light emitting device - Google Patents

Description

The present invention relates to a light emitting device.

Patent Document 1 describes a technique relating to a semiconductor light emitting device. This semiconductor light emitting device includes an active layer, a pair of clad layers sandwiching the active layer, and a phase modulation layer optically coupled to the active layer. The phase modulation layer includes a basic layer and a plurality of different refractive index regions having different refractive indexes from the basic layer. When an XYZ Cartesian coordinate system with the thickness direction of the phase modulation layer as the Z-axis direction is set and a virtual square lattice with a lattice spacing a is set in the XY plane, each different refractive index region is the position of the center of gravity. Is arranged so as to deviate from the grid point position in the virtual square grid by a distance r. The distance r satisfies 0 <r ≦ 0.3a.

International Publication No. 2016/148507

Research is being conducted on a light emitting device that outputs an arbitrary light image by controlling the phase spectrum and intensity spectrum of light emitted from a plurality of light emitting points arranged in a two-dimensional manner. As one of the structures of such a light emitting device, there is a structure including a phase modulation layer provided on the substrate. When the phase modulation layer has a basic layer and a plurality of different refractive index regions having different refractive indexes from the basic layer, and a virtual square lattice is set in a plane perpendicular to the thickness direction of the phase modulation layer. In addition, the position of the center of gravity of each different refractive index region deviates from the position of the lattice point of the virtual square lattice according to the light image. Such a light emitting device is called an S-iPM (Static-integrable Phase Modulating) laser, and outputs an optical image of an arbitrary shape in a direction perpendicular to the main surface of the substrate, a direction inclined with respect to the direction, or both. ..

From such a light emitting device, primary light and -1st order light modulated in the opposite direction to the primary light are output. The primary light forms the desired output light image in the first direction, which is inclined with respect to the direction perpendicular to the main surface of the substrate. The -1st order light forms an optical image that is rotationally symmetric with the output optical image in the second direction that intersects the main surface of the substrate and is symmetrical with the first direction with respect to the axis extending in the direction perpendicular to the main surface. do. However, depending on the application, one of the primary light and the -1st order light may not be required. In such a case, it is desirable to dimm the unnecessary light of the primary light and the -1st order light with respect to the necessary light.

The present invention has been made in view of such problems, and provides a light emitting device capable of dimming one of the primary light and the -1st order light with respect to the other light. The purpose is.

In order to solve the above-mentioned problems, the first light emitting device according to the present invention is a light emitting device that outputs an optical image in a direction perpendicular to the main surface of the substrate, a direction inclined with respect to the direction, or both. A light emitting unit and a phase modulation layer provided on the substrate and optically coupled to the light emitting unit are provided. The phase modulation layer includes a basic layer and a plurality of different refractive index regions having different refractive indexes from the basic layer. When a virtual square grid is set in a plane perpendicular to the thickness direction of the phase modulation layer, the centers of gravity of the plurality of different refractive index regions pass through the grid points of the virtual square grid and are inclined with respect to the square grid. It is arranged on the first straight line, and the distance between the center of gravity of each different refractive index region and the corresponding lattice point is individually set according to the phase defined based on the optical image. When the first region and the second region for dividing the phase modulation layer into two are set, the phase indicated by the position of the center of gravity of each different refractive index region in the first region is the phase of each different refractive index region in the second region. It has a phase difference of π (rad) with respect to the phase indicated by the position of the center of gravity.

The second light emitting device according to the present invention is a light emitting device that outputs an optical image in a direction perpendicular to the main surface of the substrate, a direction inclined with respect to the direction, or both, and is a light emitting unit and a substrate. It includes a phase modulation layer provided above and optically coupled to a light emitting section. The phase modulation layer includes a basic layer and a plurality of different refractive index regions having different refractive indexes from the basic layer. When a virtual square grid is set in a plane perpendicular to the thickness direction of the phase modulation layer, the centers of gravity of a plurality of different refractive index regions pass through the grid points of the virtual square grid and are inclined with respect to the square grid. It is arranged on the first straight line, and the distance between the center of gravity of each different refractive index region and the corresponding lattice point is individually set according to the phase defined based on the optical image. When the first region and the second region for dividing the phase modulation layer into two are set, the direction of movement of the center of gravity corresponding to the phase of each different refractive index region included in the second region is included in the first region. It is opposite to the direction of movement of the center of gravity corresponding to the phase of each different refractive index region.

In the first and second light emitting devices, the first straight line that passes through the grid points of the virtual square grid set in the plane perpendicular to the thickness direction of the phase modulation layer and is inclined with respect to the square grid. The center of gravity of the different refractive index region is arranged in. The distance between the center of gravity of the different refractive index region and the corresponding lattice point is individually set according to the phase defined based on the optical image. According to such a structure, the main surface of the substrate is similar to the conventional structure described in Patent Document 1 (a structure in which the center of gravity of the different refractive index region has a rotation angle corresponding to an optical image around each lattice point). It is possible to output an optical image having an arbitrary shape in a direction perpendicular to the direction and / or a direction inclined with respect to the direction.

Further, in the above-mentioned first light emitting device, when the first region and the second region for dividing the phase modulation layer into two are set, the phase indicated by the position of the center of gravity of each different refractive index region in the second region is determined. , Has a phase difference of π (rad) with respect to the phase indicated by the position of the center of gravity of each different refractive index region in the first region. Further, in the second light emitting device, the direction of movement of the center of gravity corresponding to the phase of each different refractive index region included in the second region is the direction of the center of gravity corresponding to the phase of each different refractive index region included in the first region. It is in the opposite direction to the direction of movement. As will be described later, when the phase modulation layer has any of these configurations, one of the primary light and the -1st order light can be dimmed with respect to the other light.

In the first and second light emitting devices, the boundary line separating the first region and the second region may pass through the center of the phase modulation layer. Further, in that case, the boundary line may be a second straight line. Furthermore, the tilt angle of the first straight line with respect to the square grid is greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °, and the tilt angle of the second straight line with respect to the square grid is greater than 90 ° and less than 180 °. , Or it may be greater than 270 ° and less than 360 °. In that case, the inclination angle of the second straight line with respect to the square lattice may be 135 ° or 315 °. Alternatively, the tilt angle of the first straight line with respect to the square grid is greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °, and the tilt angle of the second straight line with respect to the square grid is greater than 0 ° and less than 90 °. , Or it may be greater than 180 ° and less than 270 °. In that case, the inclination angle of the second straight line with respect to the square lattice may be 45 ° or 225 °.

In the first and second light emitting devices, the inclination angle of the first straight line with respect to the square lattice may be constant. This makes it possible to easily design the arrangement of the center of gravity in the different refractive index region. In that case, the inclination angle of the first straight line with respect to the square lattice may be 45 °, 135 °, 225 ° or 315 °. As a result, four fundamental waves traveling along the square grid (when the X-axis and Y-axis along the square grid are set, the light traveling in the positive direction of the X-axis, the light traveling in the negative direction of the X-axis, and the positive direction of the Y-axis). The traveling light and the light traveling in the negative direction of the Y-axis) can contribute evenly to the optical image. When the inclination angle is 0 °, 90 °, 180 °, or 270 °, the first straight line corresponds to the X-axis or Y-axis of the square lattice. At this time, for example, the inclination angle is 0 ° or When the straight line is along the X-axis at 180 °, two traveling waves facing each other in the Y-axis direction out of the four fundamental waves are not subjected to phase modulation and therefore do not contribute to the signal light. Further, when the inclination angle is 90 ° or 270 ° and the first straight line is along the Y-axis, the two traveling waves facing each other in the X-axis direction do not contribute to the signal light. Therefore, when the inclination angle is 0 °, 90 °, 180 °, or 270 °, the signal light cannot be obtained with high efficiency.

In the first and second light emitting devices, the product κL of the optical coupling coefficient κ and the resonator length L may be smaller than 10. As will be described later, when the phase modulation layer has any of these configurations, one of the primary light and the -1st order light can be dimmed more effectively with respect to the other light. can.

In the first and second light emitting devices, the light emitting portion may be an active layer provided on the substrate. As a result, the light emitting unit and the phase modulation layer can be easily photocoupled.

According to the phase modulation layer design method of the present invention, one of the primary light and the -1st order light can be dimmed with respect to the other light.

It is a perspective view which shows the structure of the semiconductor light emitting element as the light emitting device which concerns on one Embodiment of this invention. It is sectional drawing which shows the laminated structure of the semiconductor light emitting element. It is a figure which shows the laminated structure of the semiconductor light emitting element when the phase modulation layer is provided between the lower clad layer and the active layer. It is a top view of the phase modulation layer. It is a figure which shows the positional relationship of the different refractive index region in a phase modulation layer. It is a top view which shows the phase modulation layer conceptually. It is a top view which shows the phase modulation layer conceptually. It is a top view which shows the phase modulation layer conceptually. It is a top view which shows the phase modulation layer conceptually. It is a top view which shows the phase modulation layer conceptually. It is a top view which shows the phase modulation layer conceptually. It is a top view which shows the phase modulation layer conceptually. (A) It is a top view which shows the unit composition area included in the 1st area. (B) It is a top view which shows the unit composition area included in the 2nd area. It is a top view which shows the example which applied the refractive index substantially periodic structure only in the specific region of a phase modulation layer. It is a top view which shows the example which arranged the different refractive index region only in the specific region of a phase modulation layer. It is a figure for demonstrating the relationship between the optical image obtained by forming an image of the output beam pattern of a semiconductor light emitting element, and the distance distribution in a phase modulation layer. It is a figure for demonstrating the coordinate transformation from the spherical coordinate to the coordinate in the XYZ Cartesian coordinate system. It is a figure explaining (a), (b) the phase angle distribution obtained from the Fourier transform result of an optical image, and the point to keep in mind when deciding the arrangement of the different refractive index region. (A) An example of a beam pattern (optical image) output from a semiconductor light emitting device is shown. (B) It is a graph which shows the light intensity distribution in the cross section which intersects with the light emitting surface of a semiconductor light emitting element and includes the axis perpendicular to the light emitting surface. (A) It is a figure which shows the phase distribution corresponding to the beam pattern shown in (a) of FIG. (B) is a partially enlarged view of (a). It is a top view which conceptually shows the phase modulation layer of a square lattice type S-iPM laser. It is a figure which conceptually shows the example of the beam pattern of the traveling wave in each direction. In this example, the inclination angle of the straight line D with respect to the X-axis and the Y-axis is 45 °. It is a graph which shows the intensity distribution of a traveling wave in the plane of a phase modulation layer. It is a graph which shows the intensity distribution of a traveling wave in the plane of a phase modulation layer. It is a graph which shows the intensity distribution of a traveling wave in the plane of a phase modulation layer. It is a graph which shows the intensity distribution of a traveling wave in the plane of a phase modulation layer. (A) It is a figure which shows the conventional method of rotating a different refractive index region around a grid point. (B) It is a figure which shows the traveling wave. (A) It is a figure which shows the method which the different refractive index region moves on the axis which passes through a lattice point and is inclined with respect to a square lattice. (B) It is a figure which shows the traveling wave. It is a top view which shows the example of the shape in the XY plane of the different refractive index region. It is a top view which shows the example of the shape in the XY plane of the different refractive index region. It is a top view of the phase modulation layer which concerns on the 2nd modification. It is a figure which shows the positional relationship of the different refractive index region in the phase modulation layer of the 2nd modification. It is a top view which shows another example of the shape of the different refractive index region in an XY plane. It is a top view which shows another example of the shape of the different refractive index region in an XY plane. It is a figure which shows the structure of the light emitting device by the 3rd modification. It is a figure which shows the cross-sectional structure of the semiconductor light emitting element which concerns on 2nd Embodiment. It is a figure which shows the laminated structure of the semiconductor light emitting element when the phase modulation layer is provided between the lower clad layer and the active layer. It is a top view which looked at the semiconductor light emitting element from the surface side. It is a chart which shows the layer structure used for calculation in a specific example. The refractive index distribution and mode distribution of the semiconductor light emitting device having the layer structure shown in FIG. 39 are shown. A graph showing the in-plane distribution of the light intensity of the traveling wave AR when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 1 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. A graph showing the in-plane distribution of the light intensity of the traveling wave AU when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 1 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the in-plane distribution of the light intensity of the traveling wave AR when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 4 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. A graph showing the in-plane distribution of the light intensity of the traveling wave AU when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 4 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the in-plane distribution of the light intensity of the traveling wave AR when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 10 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. A graph showing the in-plane distribution of the light intensity of the traveling wave AU when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 10 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the in-plane distribution of the light intensity of the traveling wave AR when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 20 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. A graph showing the in-plane distribution of the light intensity of the traveling wave AU when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 20 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the in-plane distribution of the light intensity of the traveling wave AR when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 50 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. A graph showing the in-plane distribution of the light intensity of the traveling wave AU when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 50 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the in-plane distribution of the light intensity of the traveling wave AR when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 100 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. A graph showing the in-plane distribution of the light intensity of the traveling wave AU when the planar shape of the phase modulation layer is a perfect circle and the resonator length L is 100 μm, and (b) the surface of the light intensity of the traveling wave AD. It is a graph which shows the internal distribution, and (c) is a graph which shows the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. (A) It is a graph which shows the relationship between the ratio of the intensity of -1st order light and the intensity of primary light, and the cavity length when the plane shape of a phase modulation layer is a perfect circle. (B) A graph showing the relationship between the ratio of the intensity of -1st order light and the intensity of primary light and the product of the cavity length and the optical coupling coefficient when the plane shape of the phase modulation layer is a perfect circle. be. A graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL when the planar shape of the phase modulation layer is an isosceles triangle and the resonator length L is 1 μm. And (b) is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL when the planar shape of the phase modulation layer is an isosceles triangle and the resonator length L is 4 μm. And (b) is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL when the planar shape of the phase modulation layer is an isosceles triangle and the resonator length L is 10 μm. And (b) is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL when the planar shape of the phase modulation layer is an isosceles triangle and the resonator length L is 20 μm. And (b) is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL when the planar shape of the phase modulation layer is an isosceles triangle and the resonator length L is 50 μm. And (b) is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. A graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL when the planar shape of the phase modulation layer is an isosceles triangle and the resonator length L is 100 μm. And (b) is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. (A) It is a graph which shows the relationship between the ratio of the intensity of -1st order light and the intensity of primary light, and the cavity length when the plane shape of a phase modulation layer is an isosceles triangle. (B) A graph showing the relationship between the ratio of the intensity of -1st order light and the intensity of primary light and the product of the cavity length and the optical coupling coefficient when the plane shape of the phase modulation layer is an isosceles triangle. Is. It is a table which shows the layer structure when the laser element is made of a GaAs compound semiconductor (emission wavelength 940 nm band). It is the refractive index distribution and mode distribution of the laser element which has the layer structure shown in FIG. 61. It is a table which shows the layer structure when the laser element is made of an InP compound semiconductor (emission wavelength 1300 nm band). It is the refractive index distribution and mode distribution of the laser element which has the layer structure shown in FIG. 63. It is a table which shows the layer structure when the laser element is made of a nitride compound semiconductor (emission wavelength 405 nm band). It is the refractive index distribution and mode distribution of the laser element which has the layer structure shown in FIG. 65. It is a cross-sectional view and the refractive index distribution for demonstrating the case which approximates a waveguide structure by a 6-layer slab type waveguide. It is a cross-sectional view and the refractive index distribution for demonstrating the case of approximating a waveguide structure by a five-layer slab type waveguide. It is a cross-sectional view and refractive index distribution which shows the three-layer slab structure about the optical waveguide layer in the 6-layer slab type waveguide. FIG. 5 is a cross-sectional view and a refractive index distribution showing a three-layer slab structure relating to a contact layer in a six-layer slab-type waveguide. It is a cross-sectional view and refractive index distribution which shows the three-layer slab structure about the optical waveguide layer in the five-layer slab type waveguide. FIG. 5 is a cross-sectional view and a refractive index distribution showing a three-layer slab structure relating to a contact layer in a five-layer slab-type waveguide. It is a cross-sectional view which shows the three-layer slab structure which consists of a lower clad layer, an optical waveguide layer, and an upper clad layer, and its refractive index distribution. It is a table which shows the example of the 5-layer slab structure when the laser element is made of a GaAs-based compound semiconductor. It is a table showing the refractive indexes n ₁ , n ₂ , and n _{3 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer used in the calculation, and a table showing the calculation results of the lower limit value and the upper limit value. It is a graph which shows the relationship between _{the standardized waveguide width V 1 of the} optical waveguide layer represented by the formula (1) and (2), and a standardized propagation coefficient b. It is a table showing the refractive indexes n ₄ , n ₅ , and n _{6 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer used in the calculation, and a table showing the calculation result of the upper limit value. It is a graph which shows the relationship between _{the standardized waveguide width V 2 of the} contact layer represented by the formula (5) and the formula (6), and a standardized propagation coefficient b. It is the refractive index distribution and mode distribution of the laser element which has the layer structure shown in FIG. 74. It is a table which shows the example of the 6-layer slab structure when the laser element is made of an InP compound semiconductor. It is a table showing the refractive indexes n ₁ , n ₂ , and n _{3 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer used in the calculation, and a table showing the calculation results of the lower limit value and the upper limit value. It is a graph which shows the relationship between _{the standardized waveguide width V 1 of the} optical waveguide layer represented by the formula (1) and (2), and a standardized propagation coefficient b. It is a table showing the refractive indexes n ₄ , n ₅ , and n _{6 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer used in the calculation, and a table showing the calculation result of the upper limit value. It is a graph which shows the relationship between _{the standardized waveguide width V 2 of the} contact layer represented by the formula (5) and the formula (6), and a standardized propagation coefficient b. It is the refractive index distribution and mode distribution of the laser element which has the layer structure shown in FIG. It is a table which shows the example of the 6-layer slab structure when the laser element is made of a nitride compound semiconductor. It is a table showing the refractive indexes n ₁ , n ₂ , and n _{3 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer used in the calculation, and a table showing the calculation results of the lower limit value and the upper limit value. It is a graph which shows the relationship between _{the standardized waveguide width V 1 of the} optical waveguide layer represented by the formula (1) and (2), and a standardized propagation coefficient b. It is a table showing the refractive indexes n ₄ , n ₅ , and n _{6 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer used in the calculation, and a table showing the calculation result of the upper limit value. It is a graph which shows the relationship between _{the standardized waveguide width V 2 of the} contact layer represented by the formula (5) and the formula (6), and a standardized propagation coefficient b. It is the refractive index distribution and mode distribution of the laser element which has the layer structure shown in FIG.

Hereinafter, embodiments of the phase modulation layer design method according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a perspective view showing a configuration of a semiconductor light emitting device 1A as a light emitting device according to an embodiment of the present invention. An XYZ Cartesian coordinate system is defined in which the axis extending in the thickness direction of the semiconductor light emitting device 1A through the center of the semiconductor light emitting element 1A is the Z axis. The semiconductor light emitting element 1A is an S-iPM laser that forms a standing wave in the XY in-plane direction and outputs a phase-controlled plane wave in the Z-axis direction. It outputs a two-dimensional arbitrary-shaped optical image including a direction perpendicular to (that is, a Z-axis direction) and / or a direction inclined with respect to the direction.

FIG. 2 is a diagram schematically showing a laminated structure of the semiconductor light emitting device 1A. As shown in FIGS. 1 and 2, the semiconductor light emitting device 1A has an active layer 12 as a light emitting portion provided on the main surface 10a of the semiconductor substrate 10 and an active layer 12 provided on the main surface 10a. It includes a pair of clad layers 11 and 13 to be sandwiched, and a contact layer 14 provided on the clad layer 13. These semiconductor substrates 10 and each layer 11 to 14 are composed of compound semiconductors such as GaAs-based semiconductors, InP-based semiconductors, and nitride-based semiconductors. The energy bandgap of the clad layer 11 and the energy bandgap of the clad layer 13 are larger than the energy bandgap of the active layer 12. The thickness direction of the semiconductor substrate 10 and the layers 11 to 14 coincides with the Z-axis direction.

The semiconductor light emitting device 1A further includes a phase modulation layer 15 optically coupled to the active layer 12. In this embodiment, the phase modulation layer 15 is provided between the active layer 12 and the clad layer 13. If necessary, an optical guide layer may be provided between the active layer 12 and the clad layer 13 and at least one of the active layer 12 and the clad layer 11. When the optical guide layer is provided between the active layer 12 and the clad layer 13, the phase modulation layer 15 is provided between the clad layer 13 and the optical guide layer. The thickness direction of the phase modulation layer 15 coincides with the Z-axis direction. The optical guide layer may include a carrier barrier layer for efficiently confining carriers in the active layer 12.

As shown in FIG. 3, the phase modulation layer 15 may be provided between the clad layer 11 and the active layer 12. When the optical guide layer is provided between the active layer 12 and the clad layer 11, the phase modulation layer 15 is provided between the clad layer 11 and the optical guide layer.

The phase modulation layer 15 is composed of a basic layer 15a made of a first refractive index medium and a second refractive index medium having a refractive index different from that of the first refractive index medium, and a plurality of different refractive index regions existing in the basic layer 15a. It is configured to include 15b. The plurality of different refractive index regions 15b include a substantially periodic structure. When the effective refractive index of the phase modulation layer 15 is _{n, the wavelength λ 0} (= a × n, a is the lattice spacing) selected by the phase modulation layer 15 is included in the emission wavelength range of the active layer 12. .. _{The phase modulation layer 15 can select the wavelength λ 0} of the emission wavelengths of the active layer 12 and output it to the outside. The laser beam incident on the phase modulation layer 15 forms a predetermined mode according to the arrangement of the different refractive index regions 15b in the phase modulation layer 15, and is external from the semiconductor light emitting device 1A as a laser beam having a desired pattern. Is emitted to.

The semiconductor light emitting device 1A further includes an electrode 16 provided on the contact layer 14 and an electrode 17 provided on the back surface 10b of the semiconductor substrate 10. The electrode 16 is in ohmic contact with the contact layer 14, and the electrode 17 is in ohmic contact with the semiconductor substrate 10. Further, the electrode 17 has an opening 17a. The electrode 16 is provided in the central region of the contact layer 14. The portion of the contact layer 14 other than the electrode 16 is covered with the protective film 18. The contact layer 14 that is not in contact with the electrode 16 may be removed. The portion of the back surface 10b of the semiconductor substrate 10 other than the electrode 17 (including the inside of the opening 17a) is covered with the antireflection film 19. The antireflection film 19 in the region other than the opening 17a may be removed.

When a driving current is supplied between the electrode 16 and the electrode 17, recombination of electrons and holes occurs in the active layer 12, and the active layer 12 emits light. The electrons and holes that contribute to this light emission, as well as the generated light, are efficiently confined between the clad layer 11 and the clad layer 13.

The light emitted from the active layer 12 enters the inside of the phase modulation layer 15 and forms a predetermined mode according to the lattice structure inside the phase modulation layer 15. The laser light emitted from the phase modulation layer 15 is directly output from the back surface 10b through the opening 17a to the outside of the semiconductor light emitting device 1A, or is reflected by the electrode 16 and then passes through the back surface 10b through the opening 17a. Is output to the outside of the semiconductor light emitting device 1A. At this time, the 0th-order light contained in the laser light is emitted in the direction perpendicular to the main surface 10a. On the other hand, the signal light (primary light and -1st order light) included in the laser light is emitted in a two-dimensional arbitrary direction including a direction perpendicular to the main surface 10a and a direction inclined with respect to the main surface 10a. It is the signal light that forms the desired light image.

In one example, the semiconductor substrate 10 is a GaAs substrate, and the clad layer 11, the active layer 12, the clad layer 13, the contact layer 14, and the phase modulation layer 15 are compounds composed of Group III elements and Group V elements, respectively. It is a semiconductor layer. In one embodiment, the clad layer 11 is an AlGaAs layer, the active layer 12 has a multiple quantum well structure (barrier layer: AlGaAs / well layer: InGaAs), and the basic layer 15a of the phase modulation layer 15 is GaAs. The different refractive index region 15b is a hole, the clad layer 13 is an AlGaAs layer, and the contact layer 14 is a GaAs layer.

In AlGaAs, the energy band gap and the refractive index can be easily changed by changing the composition ratio of Al. In Al _x Ga _1-x As, when the composition ratio x of Al having a relatively small atomic radius is decreased (increased), the energy band gap positively correlated with this becomes smaller (larger), and the atomic radius of GaAs becomes smaller (larger). When InGaAs is obtained by mixing a large amount of In, the energy band gap becomes small. That is, the Al composition ratio of the clad layers 11 and 13 is larger than the Al composition ratio of the barrier layer (AlGaAs) of the active layer 12. The Al composition ratio of the clad layers 11 and 13 is set to, for example, 0.2 to 1.0, and is 0.4 in one example. The Al composition ratio of the barrier layer of the active layer 12 is set to, for example, 0 to 0.3, and is 0.15 in one example.

Note that noise light having a mesh-like dark portion may be superimposed on the beam pattern corresponding to the light image emitted from the semiconductor light emitting device 1A. According to the research of the inventor, the noise light having the mesh-like dark portion is caused by the higher-order mode in the stacking direction inside the semiconductor light emitting device 1A. Here, the basic mode in the stacking direction is a mode having an intensity distribution including the active layer 12 and having one peak over the region sandwiched between the clad layer 11 and the clad layer 13, and is a higher-order mode. Is a mode having an intensity distribution in which two or more peaks are present. While the peak of the intensity distribution in the basic mode is formed in the vicinity of the active layer 12, the peak of the intensity distribution in the higher-order mode is also formed in the clad layer 11, the clad layer 13, the contact layer 14, and the like. Further, there are a waveguide mode and a leakage mode as modes in the stacking direction, but since the leakage mode does not exist stably, only the waveguide mode is focused here. Further, the waveguide mode includes a TE mode in which the electric field vector exists in the in-plane direction of the layer and a TM mode in which the electric field vector exists in the vertical direction of the layer surface. Here, only the TE mode is focused on. Such a higher-order mode occurs remarkably when the refractive index of the clad layer 13 between the active layer 12 and the contact layer is larger than the refractive index of the clad layer 11 between the active layer 12 and the semiconductor substrate. .. Usually, the refractive indexes of the active layer 12 and the contact layer 14 are much larger than the refractive indexes of the clad layers 11 and 13. Therefore, when the refractive index of the clad layer 13 is larger than the refractive index of the clad layer 11, light is also confined in the clad layer 13 and a waveguide mode is formed. This results in a higher order mode.

In the semiconductor light emitting device 1A of the present embodiment, the refractive index of the clad layer 13 is equal to or lower than the refractive index of the clad layer 11. As a result, the occurrence of the higher-order mode as described above can be suppressed, and noise light having a mesh-like dark portion superimposed on the beam pattern can be reduced.

ここで、ＴＥモードは層厚方向の伝搬モード、ｎ₁は活性層１２を含む光導波路層の屈折率、ｎ₂は光導波路層に隣接する層のうち屈折率の高い層の屈折率、Ｎ_１はモード次数、ｎ_ｃｌａｄはクラッド層１１の屈折率、ｎ_３は光導波路層に隣接する層のうち屈折率の低い層の屈折率、ｎ_ｅｆｆは３層スラブ導波路構造におけるＴＥモードの等価屈折率である。 Further, the three-layer slab waveguide structure composed of the optical waveguide layer and the two layers adjacent to the optical waveguide layer preferably satisfies the following conditions. Specifically, the optical waveguide layer in the three-layer slab waveguide structure is composed of the active layer 12 when the refractive index of the phase modulation layer 15 is smaller than the refractive index of the clad layer 11. On the other hand, the optical waveguide layer is composed of the phase modulation layer 15 and the active layer 12 when the refractive index of the phase modulation layer 15 is equal to or higher than the refractive index of the clad layer 11. In any case, the optical waveguide layer does not include the clad layers 11 and 13. In such a three-layer slab waveguide structure, the following equation standards influencing for good waveguide width V ₁ of the in TE mode (1) and is defined by (2), below the asymmetry parameter a 'and the normalized propagation coefficients b when a real number satisfying the equation (3) and (4) respectively, so that the solutions of standards influencing for good waveguide width V ₁ is within the range that exists only one standard influencing for good waveguide width V ₁ and the normalized propagation coefficients b Is set.

Here, TE mode is a propagation mode in the layer thickness direction, n ₁ is the refractive index of the optical waveguide layer including the active layer 12, n ₂ is the refractive index of the layer adjacent to the optical waveguide layer and has a high refractive index, N. ₁ is the mode order, n _clad is the refractive index of the clad layer 11, n ₃ is the refractive index of the layer adjacent to the optical waveguide layer and has a low refractive index, and n _eff is the equivalent of TE mode in the three-layer slab waveguide structure. Refractive index.

According to the research by the inventors, it was found that the higher-order mode also occurs in the optical waveguide layer (high refractive index layer) including the active layer 12. Then, they have found that the higher-order mode can be suppressed by appropriately controlling the thickness and the refractive index of the optical waveguide layer. That is, the value of the standard influencing for good waveguide width V ₁ of the optical waveguide layer satisfies the condition described above, generation of higher order modes is further suppressed, and more of the noise light having a net-like dark portion that is superimposed on the beam pattern Further reduction is possible.

ここで、ｎ₄はコンタクト層１４の屈折率、ｎ_５はコンタクト層１４に隣接する層のうち屈折率の高い層の屈折率、ｎ_６はコンタクト層１４に隣接する層のうち屈折率の低い層の屈折率、Ｎ_２はモード次数、ｎ_ｅｆｆは上記別の３層スラブ導波路構造におけるＴＥモードの等価屈折率である。 Further, another three-layer slab waveguide structure composed of the contact layer and the two layers adjacent to the contact layer preferably satisfies the following conditions. Specifically, in such an alternative three-layer slab waveguide structure, and defined by the following equation standards influencing for good waveguide width V ₂ of the contact layer 14 (5) and (6), the asymmetric parameters a 'and normalized when the propagation coefficients b and real number satisfying the following equation (7) and (8), respectively, so as to fall within the scope of the no standard influencing for good waveguide width V ₂ collapsed, standard influencing for good waveguide width V ₂ and normalized The propagation coefficient b is set.

Here, n ₄ is the refractive index of the contact layer 14, n ₅ is the refractive index of the layer adjacent to the contact layer 14 having a high refractive index, and n ₆ is the refractive index of the layer adjacent to the contact layer 14 having a low refractive index. The refractive index of the layer, N ₂ is the mode order, and n _eff is the equivalent refractive index of the TE mode in the above-mentioned other three-layer slab waveguide structure.

By appropriately controlling the thickness of the contact layer 14 in this way, the generation of the waveguide mode caused by the contact layer 14 can be suppressed, and the generation of the higher-order mode generated in the laser element can be further suppressed.

In another example, the semiconductor substrate 10 is an InP substrate, and the clad layer 11, the active layer 12, the phase modulation layer 15, the clad layer 13, and the contact layer 14 are made of, for example, an InP-based compound semiconductor. In one embodiment, the clad layer 11 is an InP layer, the active layer 12 has a multiple quantum well structure (barrier layer: GaInAsP / well layer: GaInAsP), and the basic layer 15a of the phase modulation layer 15 is GaInAsP. The different refractive index region 15b is a pore, the clad layer 13 is an InP layer, and the contact layer 14 is a GaInAsP layer.

In yet another example, the semiconductor substrate 10 is a GaN substrate, and the clad layer 11, the active layer 12, the phase modulation layer 15, the clad layer 13, and the contact layer 14 are made of, for example, a nitride compound semiconductor. In one embodiment, the clad layer 11 is an AlGaN layer, the active layer 12 has a multiple quantum well structure (barrier layer: InGaN / well layer: InGaN), and the basic layer 15a of the phase modulation layer 15 is GaN. The different refractive index region 15b is a pore, the clad layer 13 is an AlGaN layer, and the contact layer 14 is a GaN layer.

The clad layer 11 is provided with the same conductive type as the semiconductor substrate 10, and the clad layer 13 and the contact layer 14 are provided with a conductive type opposite to that of the semiconductor substrate 10. In one example, the semiconductor substrate 10 and the clad layer 11 are n-type, and the clad layer 13 and the contact layer 14 are p-type. The phase modulation layer 15 has the same conductive type as the semiconductor substrate 10 when it is provided between the active layer 12 and the clad layer 11, and is a semiconductor when it is provided between the active layer 12 and the clad layer 13. It has a conductive type opposite to that of the substrate 10. The impurity concentration is, for example, 1 × 10 ¹⁷ to 1 × 10 ²¹ / cm ³ . The active layer 12 is genuine (type i) to which no impurities are intentionally added, and the impurity concentration thereof is 1 × 10 ¹⁵ / cm ³ or less. The impurity concentration of the phase modulation layer 15 may be intrinsic (i type) when it is necessary to suppress the influence of loss due to light absorption via the impurity level.

The thickness of the semiconductor substrate 10 is, for example, 150 μm. The thickness of the clad layer 11 is, for example, 2000 nm. The thickness of the active layer 12 is, for example, 175 nm. The thickness of the phase modulation layer 15 is, for example, 280 nm. The depth of the different refractive index region 15b is, for example, 200 nm. The thickness of the clad layer 13 is, for example, 2000 nm. The thickness of the contact layer 14 is, for example, 150 nm.

In the above structure, the different refractive index region 15b is a pore, but the different refractive index region 15b may be formed by embedding a semiconductor having a refractive index different from that of the basic layer 15a in the pores. In that case, for example, the pores of the basic layer 15a may be formed by etching, and the semiconductor may be embedded in the pores by using an organic metal vapor phase growth method, a sputtering method, or an epitaxial method. For example, when the basic layer 15a is made of GaAs, the different refractive index region 15b may be made of AlGaAs. Further, a semiconductor may be embedded in the pores of the basic layer 15a to form the different refractive index region 15b, and then the same semiconductor as the different refractive index region 15b may be further deposited therein. When the different refractive index region 15b is a vacancy, an inert gas such as argon, nitrogen, or hydrogen or air may be sealed in the vacancy.

The antireflection film 19 is made of, for example, a dielectric single layer film such as silicon nitride (for example, SiN) or a silicon oxide (for example, SiO ₂ ), or a dielectric multilayer film. Examples of the dielectric multilayer film include titanium oxide (TiO ₂ ), silicon dioxide (SiO ₂ ), silicon monoxide (SiO), niobium oxide (Nb ₂ O ₅ ), tantalum pentoxide (Ta ₂ O ₅ ), and foot. Dielectric layers such as magnesium _{oxide (MgF 2} ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), cerium oxide (CeO ₂ ), indium oxide (In ₂ O ₃ ), zirconium oxide (ZrO ₂₎ A film in which two or more types of dielectric layers selected from the group are laminated can be used. For example, a film having a thickness of λ / 4 is laminated with an optical film thickness for light having a wavelength of λ. The protective film 18 is, for example, an insulating film such as silicon nitride (for example, SiN) or silicon oxide (for example, SiO _2). When the semiconductor substrate 10 and the contact layer 14 are made of a GaAs-based semiconductor, the electrode 16 can be made of a material containing at least one of Cr, Ti, and Pt and Au, for example, a Cr layer and an Au layer. Has a laminated structure of. The electrode 17 can be made of a material containing at least one of AuGe and Ni and Au, and has, for example, a laminated structure of an AuGe layer and an Au layer. The materials of the electrodes 16 and 17 are not limited to these ranges as long as ohmic contact can be realized.

In the above-mentioned structure, if the structure includes the active layer 12 and the phase modulation layer 15, the material system, the film thickness, and the layer structure can be changed in various ways. Here, the scaling law holds for the so-called square lattice photonic crystal laser when the perturbation from the virtual square lattice is 0. That is, when the wavelength becomes a constant α times, the same standing wave state can be obtained by multiplying the entire cubic lattice structure by α. Similarly, in the present embodiment as well, the structure of the phase modulation layer 15 can be determined by the scaling law according to the wavelength. Therefore, it is also possible to realize the semiconductor light emitting device 1A that outputs visible light by using the active layer 12 that emits light such as blue, green, and red and applying the scaling law according to the wavelength.

When manufacturing the semiconductor light emitting device 1A, the organic metal vapor phase growth (MOCVD) method or the molecular beam epitaxy (MBE) method is used for the growth of each compound semiconductor layer. In the production of the semiconductor light emitting element 1A using AlGaAs, the growth temperature of AlGaAs was 500 ° C. to 850 ° C., and 550 to 700 ° C. was adopted in the experiment. gallium material as TMG (trimethyl gallium) and TEG (triethyl gallium), AsH ₃ as as raw material (arsine), Si ₂ H ₆ (disilane) as a raw material for the n-type impurity, DEZn (diethyl as a raw material for the p-type impurity Zinc) is used. In the growth of GaAs, TMG and arsine are used, but TMA is not used. InGaAs is manufactured using TMG, TMI (trimethylindium) and arsine. The insulating film may be formed by sputtering a target using the constituent material as a raw material or by a PCVD (plasma CVD) method.

That is, when manufacturing the semiconductor light emitting device 1A, first, an AlGaAs layer as an n-type clad layer 11 and an InGaAs / AlGaAs multiple quantum well as an active layer 12 are placed on a GaAs substrate as an n-type semiconductor substrate 10. The GaAs layer as the basic layer 15a of the structure and phase modulation layer 15 is sequentially epitaxially grown by using the MOCVD method or the MBE method.

Next, another resist is applied to the basic layer 15a, a two-dimensional fine pattern is drawn on the resist with an electron beam drawing apparatus based on the alignment mark, and the two-dimensional fine pattern is formed on the resist by developing the resist. .. Then, using the resist as a mask, the two-dimensional fine pattern is transferred onto the basic layer 15a by dry etching to form holes, and then the resist is removed. Before forming the resist, a SiN layer or a SiO ₂ layer is formed on the basic layer 15a by the PCVD method, a resist mask is formed on the basic layer 15a, and reactive ion etching (RIE) is used to form the SiN layer or the SiO ₂ layer. The fine pattern may be transferred, the resist may be removed, and then dry etching may be performed. In this case, the resistance to dry etching can be increased. The depth of the pores is, for example, 100 nm. These holes are set to the different refractive index region 15b, or the compound semiconductor (AlGaAs) to be the different refractive index region 15b is re-grown in these holes to the depth of the holes or more. When the pores have a different refractive index region 15b, a gas such as air, nitrogen, or argon may be sealed in the pores. In this way, the phase modulation layer 15 is formed. When the phase modulation layer 15 is provided between the active layer 12 and the clad layer 11, the phase modulation layer 15 may be formed on the clad layer 11 before the active layer 12 is formed.

Subsequently, the AlGaAs layer as the clad layer 13 and the GaAs layer as the contact layer 14 are sequentially formed by the MOCVD method or the MBE method, and the electrodes 16 and 17 are formed by the vapor deposition method or the sputtering method. Further, if necessary, the protective film 18 and the antireflection film 19 are formed by sputtering, a PCVD method, or the like. Through the above steps, the semiconductor light emitting device 1A of the present embodiment is manufactured.

FIG. 4 is a plan view of the phase modulation layer 15. As described above, the phase modulation layer 15 includes a basic layer 15a made of a first refractive index medium and a different refractive index region 15b made of a second refractive index medium having a refractive index different from that of the first refractive index medium. Here, a virtual square lattice in the XY plane is set in the phase modulation layer 15. It is assumed that one side of the square lattice is parallel to the X axis and the other side is parallel to the Y axis. At this time, the square-shaped unit constituent region R centered on the lattice point O of the square lattice can be set two-dimensionally over a plurality of columns along the X-axis and a plurality of rows along the Y-axis. Assuming that the XY coordinates of each unit constituent region R are given at the center of gravity position of each unit constituent region R, this center of gravity position coincides with the grid point O of the virtual square lattice. The plurality of different refractive index regions 15b are provided one by one in each unit constituent region R. The planar shape of the different refractive index region 15b is, for example, a circular shape. The lattice point O may be located outside the different refractive index region 15b, or may be included inside the different refractive index region 15b.

The ratio of the area S of the different refractive index region 15b to the one unit constituent region R is referred to as a filling factor (FF). Assuming that the lattice spacing of the square lattice is a, the filling factor FF of the different refractive index region 15b is given as ^{S / a 2.} S is the area of the different refractive index region 15b in the XY plane. For example, in the case of a perfect circle shape, S is given as ^{S = π (d / 2) 2 using the diameter d of the perfect circle.} Further, in the case of a square shape, it is given as ^{S = LA 2 using the length LA of one side of the square.}

FIG. 5 is a diagram showing the positional relationship of the different refractive index region 15b in the phase modulation layer 15. As shown in FIG. 5, the center of gravity G of each different refractive index region 15b is arranged on a straight line D1 (first straight line). The straight line D1 passes through the corresponding grid points O of each unit constituent region R and is inclined with respect to each side of the square grid. In other words, the straight line D1 is inclined with respect to both the X-axis and the Y-axis. The inclination angle of the straight line D1 with respect to one side (X-axis) of the square lattice is θ ₁ . The inclination angle θ ₁ is constant in the phase modulation layer 15. The inclination angle θ ₁ satisfies 0 ° <θ ₁ <90 °, and in one example, θ ₁ = 45 °. Alternatively, the inclination angle θ ₁ satisfies 180 ° <θ ₁ <270 °, and in one example, θ ₁ = 225 °. If the tilt angle θ ₁ satisfies 0 ° <θ ₁ <90 ° or 180 ° <θ ₁ <270 °, the straight line D1 extends from the first quadrant to the third quadrant of the coordinate plane defined by the X and Y axes. Extend. Alternatively, the inclination angle θ ₁ satisfies 90 ° <θ ₁ <180 °, and in one example, θ ₁ = 135 °. Alternatively, the inclination angle θ ₁ satisfies 270 ° <θ ₁ <360 °, and in one example, θ ₁ = 315 °. If the tilt angle θ ₁ satisfies 90 ° <θ ₁ <180 ° or 270 ° <θ ₁ <360 °, the straight line D1 extends from the second quadrant to the fourth quadrant of the coordinate plane defined by the X and Y axes. Extend. As described above, the inclination angle θ ₁ is an angle excluding 0 °, 90 °, 180 °, and 270 °. Here, the distance between the grid point O and the center of gravity G is r (x, y). x indicates the position of the x-th grid point on the X-axis, and y indicates the position of the y-th grid point on the Y-axis. When the distance r (x, y) is a positive value, the center of gravity G is located in the first quadrant (or the second quadrant). When the distance r (x, y) is a negative value, the center of gravity G is located in the third quadrant (or the fourth quadrant). When the distance r (x, y) is 0, the grid point O and the center of gravity G coincide with each other.

の範囲内である。なお、所望の光像から複素振幅分布を求める際には、ホログラム生成の計算時に一般的に用いられるGerchberg-Saxton（ＧＳ）法のような繰り返しアルゴリズムを適用することによって、ビームパターンの再現性が向上する。 The distance r (x, y) between the center of gravity G of each different refractive index region 15b and the corresponding lattice point O of each unit constituent region R shown in FIG. 5 is a phase set based on a desired optical image. It is set individually for each different refractive index region 15b according to the above. The distribution of the distance r (x, y) has a specific value for each position determined by the value of x, y, but is not always represented by a specific function. The distribution of the distance r (x, y) is determined from the extracted phase distribution of the complex amplitude distribution obtained by Fourier transforming the desired optical image. The maximum value of the distance r (x, y) is R ₀ , and the minimum value is −R ₀ . Assuming that the grid spacing of the square grid is a, the maximum value R ₀ of r (x, y) is, for example.

Is within the range of. When obtaining the complex amplitude distribution from the desired optical image, the reproducibility of the beam pattern can be improved by applying a repeating algorithm such as the Gerchberg-Saxton (GS) method, which is generally used when calculating hologram generation. improves.

6 to 12 are plan views conceptually showing the phase modulation layer 15. In this embodiment, as shown in any of FIGS. 6 to 12, two regions Fa and Fb that divide the phase modulation layer 15 are set. The region Fa is the first region in the present embodiment, and the region Fb is the second region in the present embodiment. The regions Fa and Fb are provided side by side in an arbitrary direction along a plane perpendicular to the thickness direction of the phase modulation layer 15. In the examples shown in FIGS. 6 to 11, the regions Fa and Fb are arranged so as to sandwich the center point Q of the phase modulation layer 15. Further, in the example shown in FIG. 12, one region Fb includes the center point Q of the phase modulation layer 15. The regions Fa and Fb are partitioned by the boundary line D2. The boundary line D2 may be a straight line (second straight line) as shown in FIGS. 6 to 11, or may be a curved line as shown in FIG. Further, the boundary line D2 may pass on the center point Q of the phase modulation layer 15 as shown in FIGS. 6 to 11, or may avoid the center point Q as shown in FIG.

Hereinafter, the forms of the regions Fa and Fb shown in FIGS. 6 to 11 will be described individually. In the following description, when the origin of the XY Cartesian coordinate system coincides with the center point Q, the first quadrant F1 is the quadrant in which both the X coordinate and the Y coordinate are positive, and the third quadrant F3 is the X coordinate and the Y coordinate. It is a quadrant in which both coordinates are negative. Further, the second quadrant F2 is a quadrant in which the X coordinate is negative and the Y coordinate is positive, and the fourth quadrant F4 is a quadrant in which the X coordinate is positive and the Y coordinate is negative.

In the example shown in FIGS. 6 and 7, the regions Fa and Fb are aligned in the direction along the straight line D1 (see FIG. 5). Specifically, when the inclination angle θ ₁ of the straight line D1 satisfies 0 ° <θ ₁ <90 ° or 180 ° <θ ₁ <270 °, the region Fa is arranged on the first quadrant F1 side with respect to the coordinate origin. , The region Fb is arranged on the third quadrant F3 side with respect to the coordinate origin. In this case, the boundary line D2 extends from the second quadrant F2 to the fourth quadrant F4 on the XY coordinate plane. _{When the boundary line D2 is a straight line, the inclination angle θ 2} of the boundary line D2 with respect to the X axis of the square lattice is greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °. In the example shown in FIG. 6, the inclination angle θ ₂ is 135 ° or 315 °, and the boundary line D2 constitutes the diagonal line of the square phase modulation layer 15. In the example shown in FIG. 7, the tilt angle θ ₂ is 150 ° or 330 °. Further, when the inclination angle θ ₁ of the straight line D1 satisfies 90 ° <θ ₁ <180 ° or 270 ° <θ ₁ <360 °, the region Fa is arranged on the second quadrant F2 side with respect to the coordinate origin, and the region Fb Is arranged on the F4 side of the fourth quadrant with respect to the coordinate origin. Further, in this case, the boundary line D2 extends from the first quadrant F1 to the third quadrant F3 on the XY coordinate plane. In other words, when the boundary line D2 is a straight line, the inclination angle θ ₂ of the boundary line D2 with respect to the X axis of the square lattice is greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °. In one example, the boundary line D2 is orthogonal to the straight line D1.

In the examples shown in FIGS. 8 and 9, the regions Fa and Fb are aligned in a direction intersecting the straight line D1 (see FIG. 5). Specifically, when the inclination angle θ ₁ of the straight line D1 satisfies 0 ° <θ ₁ <90 ° or 180 ° <θ ₁ <270 °, the region Fa is arranged on the second quadrant F2 side with respect to the coordinate origin. , The region Fb is arranged on the fourth quadrant F4 side with respect to the coordinate origin. In this case, the boundary line D2 extends from the first quadrant F1 to the third quadrant F3 on the XY coordinate plane. _{When the boundary line D2 is a straight line, the inclination angle θ 2} of the boundary line D2 with respect to the X axis of the square lattice is greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °. In the example shown in FIG. 8, the inclination angle θ ₂ is 45 ° or 225 °, and the boundary line D2 constitutes the diagonal line of the square phase modulation layer 15. In the example shown in FIG. 9, the tilt angle θ ₂ is 30 ° or 210 °. Further, when the inclination angle θ ₁ of the straight line D1 satisfies 90 ° <θ ₁ <180 ° or 270 ° <θ ₁ <360 °, the region Fa is arranged on the first quadrant F1 side with respect to the coordinate origin, and the region Fb Is arranged on the F3 side of the third quadrant with respect to the coordinate origin. Further, in this case, the boundary line D2 extends from the second quadrant F2 of the XY coordinate plane to the fourth quadrant F4. In other words, when the boundary line D2 is a straight line, the inclination angle θ ₂ of the boundary line D2 with respect to the X axis of the square lattice is greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °. In one example, the boundary line D2 is parallel to the straight line D1.

In the example shown in FIG. 10, the regions Fa and Fb are arranged in the direction along the Y axis. In this case, the boundary line D2 is parallel to the X-axis and, in one example, coincides with the X-axis. The tilt angle θ ₂ is 0 ° or 180 °. Further, in the example shown in FIG. 11, the regions Fa and Fb are arranged in the direction along the X axis. In this case, the boundary line D2 is parallel to the Y-axis and, in one example, coincides with the Y-axis. The tilt angle θ ₂ is 90 ° or 270 °. As described above, the boundary line D2 may be parallel to the X-axis or the Y-axis (that is, the arrangement direction of the virtual square lattice).

FIG. 13A is a plan view showing a unit constituent area R included in the area Fa. FIG. 13B is a plan view showing a unit constituent area R included in the area Fb. As shown in FIG. 13 (a), in the region Fa, when the phase P (x, y) at a certain coordinate (x, y) is P ₀ , the distance r (x, y) is set to 0. If the phase P (x, y) is π + P ₀ , the distance r (x, y) is set to the maximum value R 0, and if the phase P (x, y) is −π + P ₀ , the _{distance r (x, y) is set to the maximum value R 0.} Set the distance r (x, y) to the minimum value −R _0. Then, for the intermediate phase P (x, y), the distance r (x, y) is r (x, y) = {P (x, y) −P ₀ } × R _{0 / π.} ). On the other hand, in the region Fb, when the phase P (x, y) at a certain coordinate (x, y) is P ₀ , the distance r (x, y) is set to 0, and the phase P (x, y). When is π + P ₀ , the distance r (x, y) is _{set to the minimum value −R 0} , and when the phase P (x, y) is −π + P ₀ , the distance r (x, y) is maximized. Set to the value -R _0. Then, for the intermediate phase P (x, y), the distance r (x, _{y) = − {P (x, y) −P 0} } × R _{0 / π.} Take y). That is, the phase P (x, y) indicated by the position of the center of gravity G of each different refractive index region 15b in the region Fb is the phase P (x, y) indicated by the position of the center of gravity G of each different refractive index region 15b in the region Fa. It has a phase difference of π (rad) with respect to y) and is inverted. In other words, the direction of movement of the center of gravity G corresponding to the phase P (x, y) of each different refractive index region 15b included in the region Fb is the phase P (x, y) of each different refractive index region 15b included in the region Fa. It is opposite to the direction of movement of the center of gravity G corresponding to y). The initial phase P ₀ can be set arbitrarily.

FIG. 14 is a plan view showing an example in which the substantially periodic structure of the refractive index of FIG. 4 is applied only within a specific region of the phase modulation layer. In the example shown in FIG. 14, a substantially periodic structure (example: the structure of FIG. 4) for emitting a target beam pattern is formed inside the square inner region RIN1. On the other hand, in the outer region ROUT1 surrounding the inner region RIN1, a perfect circular different refractive index region where the grid point position and the center of gravity position of the square lattice coincide with each other is arranged. In the inner region RIN1 and the outer region ROUT1, the lattice spacings of the square lattices virtually set are the same (= a). In the case of this structure, since the light is also distributed in the outer region ROUT1, it is possible to suppress the generation of high frequency noise (so-called window function noise) generated by the sudden change in light intensity in the peripheral portion of the inner region RIN1. can. In addition, light leakage in the in-plane direction can be suppressed, and a reduction in the threshold current can be expected.

FIG. 15 is a plan view showing an example in which the different refractive index region 15b is arranged only in a specific region of the phase modulation layer. In the example shown in FIG. 15, a plurality of different refractive index regions 15b for emitting a target beam pattern are formed inside the square inner region RIN2. On the other hand, the outer region ROUT2 surrounding the inner region RIN2 does not include the different refractive index region 15b and is composed of only the basic layer 15a. Further, FIG. 15 shows a square electrode 16. The area of the electrode 16 in the cross section perpendicular to the thickness direction of the electrode 16 is larger than the area of the inner region RIN2 in the cross section perpendicular to the thickness direction of the phase modulation layer. Further, the inner region RIN2 when viewed from the same direction is included in the electrode 16.

FIG. 16 is a diagram for explaining the relationship between the optical image obtained as the output beam pattern of the semiconductor light emitting device 1A and the phase distribution P (x, y) in the phase modulation layer 15. The center point Q of the output beam pattern is located on an axis perpendicular to the main surface 10a of the semiconductor substrate 10, and FIG. 16 shows four quadrants with the center point Q as the origin. .. Although FIG. 16 shows a case where an optical image is obtained in the first quadrant and the third quadrant as an example, it is also possible to obtain an image in the second quadrant and the fourth quadrant or all quadrants. In this embodiment, as shown in FIG. 16, a point-symmetrical optical image with respect to the origin is obtained. FIG. 16 shows, as an example, a case where the character “A” is obtained as the +1st-order diffracted light in the third quadrant, and the pattern obtained by rotating the character “A” by 180 degrees in the first quadrant is obtained as the -1st-order diffracted light. .. In the case of a rotationally symmetric optical image having the center Q as the origin (for example, a cross, a circle, a double circle, etc.), they are observed as one optical image overlapping.

The optical image obtained by forming the output beam pattern of the semiconductor light emitting device 1A is a spot, a straight line, a cross, a line drawing, a lattice pattern, a photograph, a striped pattern, CG (computer graphics), and at least one of characters. Includes. Here, in order to obtain a desired optical image, the distribution of the distance r (x, y) in the different refractive index region 15b of the phase modulation layer 15 is determined by the following procedure.

First, as a first precondition, in the XYZ Cartesian coordinate system, it is composed of M1 (integer of 1 or more) × N1 (integer of 1 or more) unit constituent regions R each having a square shape on the XY plane. A virtual square grid is set. Next, as a second precondition, the coordinates (x, y, z) in the XYZ Cartesian coordinate system are the length r of the moving diameter and the inclination angle θ _{1 tilt from the Z axis, as shown in FIG. , The spherical coordinates (r, θ 1 tilt} , θ 1 _{rot ) defined by the rotation angle θ 1 rot} from the X axis specified on the XY plane and the spherical coordinates (r, θ 1 tilt, θ 1 rot) are shown by the following equations (10) to (12). It is assumed that the relationship is satisfied. Note that FIG. 17 is a diagram _{for explaining coordinate conversion from spherical coordinates (r, θ 1tilt} , θ _1rot ) to coordinates (x, y, z) in the XYZ Cartesian coordinate system, and is a diagram for explaining coordinates (x, y, z) represents a design optical image on a predetermined plane set in the XYZ Cartesian coordinate system which is the real space. When a set of bright points towards a beam pattern corresponding to a light image emitted by the semiconductor light emitting device in the direction defined by the angle theta _1Tilt and theta _1Rot, the angle theta _1Tilt and theta _1Rot has the following formula (13) The standardized wave number specified in the above and the coordinate value k _x on the Kx axis corresponding to the X axis, and the standardized wave number specified by the following equation (14) corresponding to the Y axis and the Kx axis. shall be converted into coordinate values k _y on Ky axis orthogonal. The standardized wavenumber means the wavenumber standardized with the wavenumber corresponding to the grid spacing of the virtual square lattice as 1.0. At this time, in the wavenumber space defined by the Kx axis and the Ky axis, the specific wavenumber range including the beam pattern corresponding to the light image is square M2 (integer of 1 or more) × N2 (integer of 1 or more), respectively. ) Consists of image area FR. The integer M2 does not have to match the integer M1. Similarly, the integer N2 need not match the integer N1. Equations (13) and (14) also include, for example, Y. Kurosaka et al., "Effects of non-lasing band in two-dimensional photonic-crystal lasers clarified using omnidirectional band structure," Opt. Express 20, 21773-21783. It is disclosed in (2012).

As a third precondition, in Fourier space, Kx axis direction of the coordinate component k _{x (1} or M2 an integer) and Ky-axis direction of the coordinate component k _{y (1} or N2 an integer) and de image specified area _{FR (k} x, _{k y),} respectively, X-axis direction of the coordinate component x (1 or more M1 an integer) and Y-axis direction of the coordinate component y (1 or more than N1 integer) de XY plane identified The complex amplitude F (x, y) obtained by performing the two-dimensional inverse Fourier transformation on the above unit constituent region R (x, y) is given by the following equation (15) with j as an imaginary unit. Further, this complex amplitude F (x, y) is defined by the following equation (16) when the amplitude term is A (x, y) and the phase term is P (x, y). Further, as a fourth precondition, the unit constituent region R (x, y) is parallel to the X-axis and the Y-axis, respectively, and is the center of the unit constituent region R (x, y). It is defined by the s-axis and the t-axis that are orthogonal to each other in y).

Under the first to fourth preconditions, the region Fa of the phase modulation layer 15 is configured to satisfy the following conditions. That is, the distance r (x, y) from the lattice point O (x, y) to the center of gravity G of the corresponding different refractive index region 15b is
r (x, y) = C × {P (x, y) -P ₀ }
C: Proportional constant, for example R ₀ / π
P ₀ : An arbitrary constant, for example, 0
The corresponding different refractive index region 15b is arranged in the unit constituent region R (x, y) so as to satisfy the above relationship. That is, the distance r (x, y) is set to 0 when the phase P (x, y) at a certain coordinate (x, y) is P ₀ , and the phase P (x, y) is π + P _0. If, the maximum value _{is set to R 0} , and if the phase P (x, y) is −π + P ₀ , the minimum value is set to _{−R 0.}

Further, the region Fb of the phase modulation layer 15 is configured to satisfy the following conditions. That is, the distance r (x, y) from the lattice point O (x, y) to the center of gravity G of the corresponding different refractive index region 15b is
r (x, y) = -C x P (x, y) + P ₀
The corresponding different refractive index region 15b is arranged in the unit constituent region R (x, y) so as to satisfy the above relationship. That is, the distance r (x, y) is set to 0 when the phase P (x, y) at a certain coordinate (x, y) is P ₀ , and the phase P (x, y) is π + P _0. If, the minimum value _{is set to −R 0} , and if the phase P (x, y) is −π + P ₀ , the maximum value is set to _{R 0.}

When a desired optical image is desired, the optical image is subjected to inverse Fourier transform, and the distribution of the distance r (x, y) corresponding to the phase P (x, y) of the complex amplitude is obtained in each of the regions Fa and Fb. It is preferable to give it to a plurality of different refractive index regions 15b. The phase P (x, y) and the distance r (x, y) may be proportional to each other.

The far-field image after Fourier transform of the laser beam has various shapes such as a single spot shape, a ring shape, a linear shape, a character shape, a double ring shape, or a Laguerre Gaussian beam shape. Can be taken. Since the beam direction can also be controlled, a laser processing machine that electrically performs high-speed scanning, for example, can be realized by arranging the semiconductor light emitting elements 1A one-dimensionally or two-dimensionally. Since the beam pattern is represented by angle information in the distant field, if the target beam pattern is a bitmap image represented by two-dimensional position information, it is temporarily converted into angle information. Then, it is advisable to perform the reciprocal Fourier transform after converting to the wave number space.

As a method of obtaining the intensity distribution and the phase distribution from the complex amplitude distribution obtained by the inverse Fourier transform, for example, the intensity distribution I (x, y) is calculated by using the abs function of the numerical analysis software "MATLAB" of MathWorks. The phase distribution P (x, y) can be calculated by using the MATLAB angle function.

Here, when the phase distribution P (x, y) is obtained from the inverse Fourier transform result of the optical image and the distance r (x, y) of each different refractive index region 15b is determined, a general discrete Fourier transform (or high speed) is used. Here are some points to keep in mind when calculating using the Fourier transform). The output beam pattern calculated from the complex amplitude distribution obtained by the inverse Fourier transform of FIG. 18 (a), which is a desired optical image, is as shown in FIG. 18 (b). When divided into four quadrants such as A1, A2, A3 and A4 as shown in FIGS. 18 (a) and 18 (b), the first quadrant of the output beam pattern shown in FIG. 18 (b) is shown in FIG. A pattern in which the first quadrant of 18 (a) is rotated 180 degrees and the third quadrant of FIG. 18 (a) are superimposed appears, and the second quadrant of FIG. 18 (a) is 180 in the second quadrant of the beam pattern. A pattern in which the fourth quadrant of FIG. 18 (a) is superimposed on the rotated degree appears, and the third quadrant of FIG. 18 (a) is rotated 180 degrees in the third quadrant of the beam pattern and that of FIG. 18 (a). A pattern in which the first quadrant of FIG. 18 (a) is superimposed appears, and a pattern in which the fourth quadrant of FIG. 18 (a) is rotated by 180 degrees and the pattern in which the second quadrant of FIG. 18 (a) is superimposed appear in the fourth quadrant of the beam pattern. .. At this time, the pattern rotated by 180 degrees is due to the -1st order light component.

Here, FIG. 19A shows an example of a beam pattern (optical image) output from the semiconductor light emitting device 1A. The center of the figure corresponds to an axis that intersects the light emitting surface of the semiconductor light emitting device 1A and is perpendicular to the light emitting surface. Further, FIG. 19B is a graph showing the light intensity distribution in the cross section including the axis. FIG. 19B is a far-field image acquired using an FFP optical system (A3267-12 manufactured by Hamamatsu Photonics), a camera (ORCA-05G manufactured by Hamamatsu Photonics), and a beam profiler (Lepas-12 manufactured by Hamamatsu Photonics). The vertical counts of the image data of dots × 1024 dots are integrated and plotted. The maximum count number in FIG. 19A is standardized at 255, and the central 0th-order light B0 is saturated in order to clearly indicate the intensity ratio of ± 1st-order light. From FIG. 19B, the difference in intensity between the primary light and the -1st light can be easily understood. Further, FIG. 20A is a diagram showing a phase distribution corresponding to the beam pattern shown in FIG. 19A. FIG. 20B is a partially enlarged view of FIG. 20A. In FIGS. 20 (a) and 20 (b), the phase at each location in the phase modulation layer 15 is indicated by shading, and the dark part approaches the phase angle of 0 ° and the bright part approaches the phase angle of 360 °. However, since the center value of the phase angle can be set arbitrarily, the phase angle does not necessarily have to be set within the range of 0 ° to 360 °. As shown in FIGS. 19A and 19B, the semiconductor light emitting device 1A includes primary light including a first light image portion B1 output in a first direction inclined with respect to the axis. It is output in the second direction that is symmetric with respect to the first direction with respect to the axis, and outputs -1st order light including the first light image portion B1 and the second light image portion B2 that is rotationally symmetric with respect to the axis. Typically, the first light image portion B1 appears in the first quadrant in the XY plane and the second light image portion B2 appears in the third quadrant in the XY plane. Depending on the application, only one of the primary light and the -1st light may be used, and the other may not be used. In such a case, it is desirable that the amount of light of the other light is suppressed to be smaller than that of the one light. Therefore, in the present embodiment, as shown in FIG. 19B, the intensity difference is given to the primary light and the -1st light.

FIG. 21 is a plan view conceptually showing the phase modulation layer 15. Now, the first region T1 and the second region T2 lined up in one lattice point arrangement direction (X-axis direction) with the center point Q of the phase modulation layer 15 in between, and the other region with the center point Q of the phase modulation layer 15 in between. A third region T3 and a fourth region T4 arranged in the grid point arrangement direction (Y-axis direction) of the above are defined. That is, when the origin of the XY Cartesian coordinate system is matched with the center point Q, the first region T1 is a region where the X coordinate is positive, the second region T2 is a region where the X coordinate is negative, and the third region T3. Is a region where the Y coordinate is positive, and the fourth region T4 is a region where the Y coordinate is negative. Therefore, the first region T1 and the third region T3 overlap each other in the first quadrant F1. The first region T1 and the fourth region T4 overlap each other in the second quadrant F2. The second region T2 and the fourth region T4 overlap each other in the third quadrant F3. The second region T2 and the third region T3 overlap each other in the fourth quadrant F4.

In the phase modulation layer 15, which is the phase modulation layer of the square lattice type S-iPM laser, basic traveling waves AU, AD, AR, and AL along the XY plane are generated as shown in FIG. The traveling wave AR is a first traveling wave traveling in the direction (X-axis positive direction) from the second region T2 to the first region T1. The traveling wave AL is a second traveling wave traveling in the direction (X-axis negative direction) from the first region T1 to the second region T2. The traveling wave AU is a third traveling wave that travels in the direction from the fourth region T4 to the third region T3 (Y-axis positive direction). The traveling wave AD is a fourth traveling wave traveling in the direction (Y-axis negative direction) from the third region T3 to the fourth region T4.

As shown in FIG. 22, beam patterns that are 180 ° rotationally symmetric can be obtained from the traveling waves that travel in opposite directions. For example, a beam pattern BU containing only the second light image portion B2 can be obtained from the traveling wave AU, and a beam pattern BD containing only the first light image portion B1 can be obtained from the traveling wave AD. Similarly, the traveling wave AR gives a beam pattern BR containing only the second light image portion B2, and the traveling wave AL gives a beam pattern BL containing only the first light image portion B1. In other words, traveling waves traveling in opposite directions can obtain images that are 180 ° rotationally symmetric with each other when the phases P (x, y) are aligned with respect to the same phase distribution. This is the same as the relationship between primary light and -1st light. The beam pattern output from the semiconductor light emitting device 1A is a combination of these beam patterns BU, BD, BR, and BL.

Here, FIGS. 23 to 26 are graphs showing an example of the intensity distribution of the traveling waves AU, AD, AR, and AL in the plane of the phase modulation layer 15. FIG. 23 shows the intensity distribution of the traveling wave AU, FIG. 24 shows the intensity distribution of the traveling wave AD, FIG. 25 shows the intensity distribution of the traveling wave AR, and FIG. 26 shows the intensity distribution of the traveling wave AL. Further, in FIGS. 23 to 26, (a) represents the intensity distributions of the traveling waves AU, AD, AR, and AL by equal intensity lines, the horizontal axis represents the position in the X-axis direction, and the vertical axis represents the position. Represents the position in the Y-axis direction. (B) is a three-dimensional representation of the intensity distribution of the traveling waves AU, AD, AR, and AL, and in addition to the X-axis direction position and the Y-axis direction position, the axis representing the intensity of the traveling wave is It is shown. As shown in these figures, the intensities of the traveling waves AU, AD, AR, and AL are unevenly distributed in the plane of the phase modulation layer 15.

Specifically, the intensity of the traveling wave AU traveling in the positive direction of the Y-axis becomes stronger as the Y coordinate becomes larger, and becomes weaker as the Y coordinate becomes smaller. Further, the intensity of the traveling wave AD traveling in the negative direction of the Y-axis becomes stronger as the Y coordinate becomes smaller, and becomes weaker as the Y coordinate becomes larger. Similarly, the intensity of the traveling wave AR traveling in the positive direction of the X-axis becomes stronger as the X-coordinate becomes larger, and becomes weaker as the X-coordinate becomes smaller. Further, the intensity of the traveling wave AL traveling in the negative direction of the X-axis becomes stronger as the X coordinate becomes smaller, and becomes weaker as the X coordinate becomes larger. In other words, the traveling waves AU and AR are strong in the first quadrant F1, the traveling waves AD and AR are strong in the second quadrant F2, the traveling waves AD and AL are strong in the third quadrant F3, and the traveling waves AD and AL are strong in the fourth quadrant F4. Has strong traveling waves AU and AL. When the inclination angle θ ₁ of the straight line D1 is 45 °, 135 °, 225 °, or 315 °, the maximum intensities of the traveling waves AU, AD, AR, and AL are equal to each other. When the inclination angle θ ₁ of the straight line D1 is 0 ° <θ ₁ <45 °, 135 ° <θ ₁ <225 °, or 315 ° <θ ₁ <360 °, the maximum traveling waves AR and AL are obtained. When the intensity is greater than the maximum intensity of the traveling waves AU and AD and the inclination angle θ ₁ of the straight line D1 is 45 ° <θ ₁ <135 ° or 225 ° <θ ₁ <315 °, the traveling wave AU, The maximum intensity of AD becomes larger than the maximum intensity of traveling waves AR and AL.

In this embodiment, the intensity distributions of the traveling waves AU, AD, AR, and AL described above are used to give a difference in the amount of light of the primary light and the -1st order light, and one of them is reduced with respect to the other. do. In the region Fa located on the first quadrant F1 side with respect to the boundary line D2 shown in FIG. 6, the light intensities of the traveling waves AU and AR are relatively large with respect to the light intensities of the traveling waves AD and AL. .. On the other hand, in the region Fb located on the third quadrant F3 side with respect to the boundary line D2, the light intensities of the traveling waves AD and AL are relatively large with respect to the light intensities of the traveling waves AU and AR. Further, when the straight line D1 extends from the first quadrant F1 to the third quadrant F3 as shown in FIG. 6, assuming that the phases P (x, y) are aligned, the traveling waves AU and AR are first-order. It becomes light, and the traveling waves AD and AL become -1st order light.

However, in the present embodiment, as described above, the phase modulation layer 15 is divided into a region Fa and a region Fb, and the phase P (x, y) indicated by the position of the center of gravity G of each different refractive index region 15b in the region Fb. Has a phase difference of π (rad) with respect to the phase P (x, y) indicated by the position of the center of gravity G of each different refractive index region 15b in the region Fa, and is inverted. That is, the direction of movement of the center of gravity G corresponding to the phase P (x, y) of each different refractive index region 15b included in the region Fb is set to the phase P (x, y) of each different refractive index region 15b included in the region Fa. ) Corresponds to the direction of movement of the center of gravity G. When the phase π (rad) is added to a certain phase distribution as a whole, the output optical image is rotated by 180 °. Therefore, the primary light of each traveling wave in the region Fb changes to the -1st order light, and the -1st order light changes to the primary light. That is, the traveling waves AU and AR become the -1st order light, and the traveling waves AD and AL become the primary light. As described above, since the light intensities of the traveling waves AD and AL are relatively high in the region Fb, as a result, the intensity of the primary light increases and the intensity of the -1st order light decreases in the region Fb. On the other hand, in the region Fa, since the light intensities of the traveling waves AU and AR are relatively high, the intensity of the primary light is larger than the intensity of the -1st order light. Therefore, the intensity of the primary light increases as a whole of the phase modulation layer 15, and the intensity of the -1st order light decreases. It should be noted that the above description holds even if the primary light and the -1st order light are interchanged with each other. From the above, according to the semiconductor light emitting device 1A of the present embodiment, one of the primary light and the -1st order light can be dimmed with respect to the other light.

In a square lattice with a lattice spacing a, if the unit vectors of Cartesian coordinates are x and y, the basic translation vectors a ₁ = ax and a ₂ = ay, and the basic reciprocal lattice vectors b with respect to the _{translation vectors a 1} and a _{2. 1} = (2π / a) x, b ₂ = (2π / a) y. When the wave vector of the wave existing in the lattice is k = nb ₁ + mb ₂ (n and m are arbitrary integers), the wave number k exists at the Γ point, but the magnitude of the wave vector is basically the reverse. When it is equal to the magnitude of the lattice vector, a resonance mode (standing wave in the XY plane) in which the lattice spacing a is equal to the wavelength λ is obtained. In this embodiment, oscillation in such a resonance mode (standing wave state) can be obtained. At this time, considering the TE mode in which the electric field exists in the plane parallel to the square lattice, there are four modes in the standing wave state in which the lattice spacing and the wavelength are equal in this way due to the symmetry of the square lattice. In the present embodiment, a desired beam pattern can be obtained in the same manner when oscillating in any of the four standing wave modes.

In the semiconductor light emitting device 1A, the standing wave in the phase modulation layer 15 is scattered by the different refractive index region 15b, and the wave surface obtained in the vertical direction is phase-modulated to obtain a desired beam pattern. Therefore, a desired beam pattern can be obtained without a polarizing plate. This beam pattern is not only a pair of single-peak beams (spots), but as described above, a character shape, two or more spots having the same shape, or a vector in which the phase and intensity distribution are spatially non-uniform. It can also be a beam or the like.

The refractive index of the basic layer 15a is preferably 3.0 to 3.5, and the refractive index of the different refractive index region 15b is preferably 1.0 to 3.4. The average radius of each different refractive index region 15b is, for example, 20 nm to 120 nm in the case of the 940 nm band. The diffraction intensity in the Z-axis direction changes as the size of each different refractive index region 15b changes. This diffraction efficiency is proportional to the optical coupling coefficient κ1 represented by the first-order coefficient when the shape of the different refractive index region 15b is Fourier transformed. The photocoupling coefficient is described, for example, in K. Sakai et al., “Coupled-WaveTheory for Square-Lattice Photonic Crystal Lasers With TE Polarization, IEEE J.Q. E. 46, 788-795 (2010)”.

The effect obtained by the method for designing the phase modulation layer 15 according to the present embodiment described above will be described. In the present embodiment, the phase modulation layer 15 optically coupled to the active layer 12 has a basic layer 15a and a plurality of different refractive index regions 15b having different refractive indexes from the basic layer 15a, and is virtually square. The center of gravity G of each Cartesian index region 15b is arranged on a straight line D1 that passes through the lattice point O of the lattice and is inclined with respect to the X-axis and the Y-axis of the square lattice. The distance r (x, y) between the center of gravity G of each different refractive index region 15b and the corresponding lattice point O is individually determined according to the phase P (x, y) defined based on the desired optical image. Is set to. In such a case, the phase of the beam changes according to the distance r (x, y) between the grid point O and the center of gravity G. Therefore, the phase of the beam emitted from each different refractive index region 15b can be controlled only by changing the distance r (x, y), and the beam pattern formed as a whole can be made into a desired shape. can. That is, the semiconductor light emitting device 1A is an S-iPM laser, and according to such a structure, the center of gravity G of each different refractive index region 15b has a rotation angle corresponding to the light image around each lattice point O. Similar to the structure, an optical image having an arbitrary shape can be output in a direction perpendicular to the main surface 10a of the semiconductor substrate 10, a direction inclined with respect to the direction, or both.

Further, in the present embodiment, when the regions Fa and the regions Fb arranged in the direction along the straight line D1 with the center point Q of the phase modulation layer 15 interposed therebetween are set, the position of the center of gravity G of each different refractive index region 15b in the region Fb is set. The phase P (x, y) indicated by has a phase difference of π (rad) with respect to the phase P (x, y) indicated by the position of the center of gravity G of each different refractive index region 15b in the region Fa. It is inverted. In other words, the direction of movement of the center of gravity G corresponding to the phase P (x, y) of each different refractive index region 15b included in the region Fb is the phase P (x, y) of each different refractive index region 15b included in the region Fa. It is opposite to the direction of movement of the center of gravity G corresponding to y). As a result, as described above, one of the primary light and the -1st order light can be dimmed with respect to the other light.

According to the study of the present inventor, in the conventional semiconductor light emitting device that rotates the different refractive index region around the lattice point, both traveling waves traveling in opposite directions due to the nature of the arrangement of the different refractive index region. Is always included. That is, in the conventional method, the same amount of primary light and -1st-order light appear in all of the four traveling waves AU, AD, AR, and AL that form a standing wave, and the radius of the rotating circle ( Depending on the distance between the center of gravity of the different refractive index region and the lattice points), 0th-order light is generated. Therefore, it is difficult in principle to give a difference in the amount of each of the primary light and the -1st order light, and it is difficult to selectively reduce one of them. Therefore, it is difficult to reduce the amount of -1st order light relative to the amount of primary light.

を用いると、位相分布Φ（ｘ，ｙ）を級数展開することができ、０次光及び±１次光の各光量を説明することができる。このとき、位相分布Φ（ｘ，ｙ）の０次光成分はＪ₀（２πｒ／ａ）、１次光成分はＪ₁（２πｒ／ａ）、−１次光成分はＪ_-1（２πｒ／ａ）と表される。ところで、±１次のベッセル関数に関しては、Ｊ₁（ｘ）＝−Ｊ_-1（ｘ）の関係があるため、±１次光成分の大きさは等しくなる。ここでは、４つの進行波の１例としてＹ軸正方向の進行波ＡＵについて考えたが、他の３波（進行波ＡＤ，ＡＲ，ＡＬ）についても同様の関係が成立し、±１次光成分の大きさが等しくなる。以上の議論から、異屈折率領域１５ｂを格子点Ｏの周りで回転させる従来の方式では、±１次光成分の光量に差を与えることが原理的に困難となる。 Here, in the conventional method of rotating the different refractive index region 15b around the lattice point O shown in FIG. 27 (a), either the primary light or the -1st order light can be selectively reduced. Explain why it is difficult. Consider the traveling wave AU in the positive direction of the Y axis shown in FIG. 27 (b) as an example of the four traveling waves with respect to the design phase φ (x, y) at a certain position. At this time, due to the geometrical relationship, the deviation from the lattice point O is r · sinφ (x, y) for the traveling wave AU, so the phase difference is (2π / a) r · sinφ (x). , Y). As a result, the phase distribution Φ (x, y) with respect to the traveling wave AU has a small influence of the size of the different refractive index region 15b, and if the influence can be ignored, Φ (x, y) = exp {j ( It is given by 2π / a) r · sinφ (x, y)}. The contribution of this phase distribution Φ (x, y) to the 0th-order light and the ± 1st-order light is n = 0 and n = ± when expanded by exp {jnΦ (x, y)} (n: integer). It is given by one component. By the way, a mathematical formula for the first-class Bessel function Jn (z) of degree n

With, the phase distribution Φ (x, y) can be expanded in series, and the amount of each of the 0th-order light and the ± 1st-order light can be explained. At this time, the 0th-order light component of the phase distribution Φ (x, y) is J ₀ (2πr / a), the primary light component is J ₁ (2πr / a), and the _-1st- order light component is J -1 (2πr / a). It is expressed as a). By the way, with respect to the ± 1st order Bessel function, since there is a relationship of J ₁ (x) = −J _-1 (x), the magnitudes of the ± 1st order light components are equal. Here, the traveling wave AU in the positive direction of the Y-axis was considered as an example of the four traveling waves, but the same relationship is established for the other three waves (traveling waves AD, AR, AL), and ± primary light The size of the components is equal. From the above discussion, in the conventional method of rotating the different refractive index region 15b around the lattice point O, it is difficult in principle to give a difference in the amount of light of the ± primary light component.

On the other hand, according to the phase modulation layer 15 of the present embodiment, there is a difference in the amount of light of the primary light and the -1st light for a single traveling wave, for example, the inclination angle θ ₁ is 45 °. , 135 °, 225 ° or 315 °, the _{closer the shift amount R 0} is to the upper limit of the above-mentioned equation (9), the more an ideal phase distribution can be obtained. As a result, the 0th-order light is reduced, and in each of the traveling waves AU, AD, AR, and AL, one of the primary light and the -1st-order light is selectively reduced. Therefore, the amount of light of the primary light and the -1st order light is changed by changing the primary light to the -1st order light and changing the -1st order light to the 1st order light in one of the traveling waves traveling in opposite directions. It is possible in principle to give a difference to.

で与えられる。この位相分布Φ（ｘ，ｙ）の０次光および±１次光への寄与は、ｅｘｐ｛ｎΦ（ｘ，ｙ）｝（ｎ：整数）で展開した場合の、ｎ＝０およびｎ＝±１の成分で与えられる。ところで、下記の数式（２１）によって表される関数ｆ（ｚ）

但し、

をＬａｕｒｅｎｔ級数展開すると、

なる数学公式が成り立つ。ここで、ｓｉｎｃ（ｘ）＝ｘ／ｓｉｎ（ｘ）である。この数学公式を用いると、位相分布Φ（ｘ，ｙ）を級数展開することができ、０次光及び±１次光の各光量を説明することができる。このとき、数学公式（２１）の指数項ｅｘｐ｛ｊπ（ｃ−ｎ）｝の絶対値が１である点に注意すると、位相分布Φ（ｘ，ｙ）の０次光成分の大きさは

と表され、１次光成分の大きさは

と表され、−１次光成分の大きさは

と表される。そして、数式（２２）〜（２４）においては、

の場合を除いて、１次光成分以外に０次光および−１次光成分が現れる。しかしながら、±１次光成分の大きさは互いに等しくならない。 Here, in the method of the present embodiment in which the different refractive index region 15b moves on the straight line D1 which passes through the lattice point O and is inclined with respect to the square lattice, which is shown in FIG. 28A, the primary light and the -1st order are used. The reason why it is possible to selectively reduce any of the lights will be explained. As an example of the four traveling waves with respect to the design phase φ (x, y) at a certain position, consider the traveling wave AU in the positive direction of the Y axis shown in FIG. 28 (b). At this time, due to the geometrical relationship, the deviation from the lattice point O is r · sin θ ₁ · {φ (x, y) −φ ₀ } / π for the traveling wave AU, so the phase difference is The relationship is (2π / a) r · sinθ ₁ · {φ (x, y) −φ ₀ } / π. Here, for the sake of simplicity, the inclination angle θ ₁ = 45 ° and the phase angle φ ₀ = 0 °. At this time, the phase distribution Φ (x, y) with respect to the traveling wave AU has a small influence on the size of the different refractive index region 15b, and if the influence can be ignored, the influence can be ignored.

Given in. The contribution of this phase distribution Φ (x, y) to the 0th-order light and the ± 1st-order light is n = 0 and n = ± when expanded by exp {nΦ (x, y)} (n: integer). It is given by one component. By the way, the function f (z) represented by the following mathematical formula (21)

However,

When the Laurent series is expanded,

Mathematical formula holds. Here, sinc (x) = x / sin (x). Using this mathematical formula, the phase distribution Φ (x, y) can be expanded in series, and the light quantities of 0th-order light and ± 1st-order light can be explained. At this time, paying attention to the fact that the absolute value of the exponential term exp {jπ (cn)} of the mathematical formula (21) is 1, the magnitude of the 0th-order optical component of the phase distribution Φ (x, y) is

The size of the primary light component is

The size of the -1st order light component is

It is expressed as. Then, in the mathematical formulas (22) to (24),

Except for the case of, 0th-order light and -1st-order light components appear in addition to the primary light component. However, the magnitudes of the ± primary light components are not equal to each other.

In the above explanation, the traveling wave AU in the positive direction of the Y axis is considered as an example of the four traveling waves, but the same relationship is established for the other three waves (traveling waves AD, AR, AL), and the ± 1st order is established. There is a difference in the size of the light component. From the above discussion, according to the method of the present embodiment in which the different refractive index region 15b moves on the straight line D1 that passes through the lattice point O and is inclined from the square lattice, it is a principle that the amount of light of the ± primary light component is different. Is possible. Therefore, in principle, it is possible to selectively extract only a desired light image (first light image portion B1 or second light image portion B2) by reducing the -1st order light or the primary light.

Further, as in the present embodiment, the inclination angle θ ₁ of the straight line D1 with respect to the square lattice may be constant in the phase modulation layer 15. This makes it possible to easily design the arrangement of the center of gravity G in the different refractive index region 15b. Further, in this case, the inclination angle may be 45 °, 135 °, 225 ° or 315 °. As a result, the four fundamental waves (traveling waves AD, AR, AL) traveling along the square lattice can contribute evenly to the optical image. Further, when the inclination angle θ ₁ is 45 °, 135 °, 225 ° or 315 °, the direction of the electromagnetic field on the straight line D1 is aligned in one direction by selecting an appropriate band end mode, so that linearly polarized light is applied. Can be obtained. As an example of such a mode, Non-Patent Document C. Peng, et al., “Coupled-wave analysis for photonic-crystal surface-emitting laserson air holes with arbitrary crystals,” Optics Express Vol. 19, No. 24, pp. There are modes A and B shown in Fig. 3 of 24672-24686 (2011). When the inclination angle θ ₁ is 0 °, 90 °, 180 ° or 270 °, a pair of traveling waves traveling in the Y direction or the X direction among the four traveling waves AU, AD, AR, and AL. Does not contribute to the primary light (signal light), so it is difficult to improve the efficiency of the signal light.

Further, as in the present embodiment, the region Fa and the region Fb may be partitioned by a boundary line D2 intersecting the straight line D1, or may be partitioned by a boundary line D2 orthogonal to the boundary line D1 and parallel to the straight line D1. good. As described above, assuming that the phases P (x, y) are aligned, the intensity of the primary light is high on one side of the boundary line D2 intersecting the straight line D1, and the intensity of the -1st order light is high on the other side. Is big. Therefore, by partitioning the region Fa and the region Fb by the boundary line D2 intersecting the straight line D1, one of the primary light and the -1st order light is effectively dimmed with respect to the other light. Can be done.

Further, in this case, the boundary line D may pass through the center point Q of the phase modulation layer 15. As described above, assuming that the phases P (x, y) are aligned, the intensity of the primary light is high on one side of the center point Q, and the intensity of the -1st order light is high on the other side. Therefore, when the boundary line D passes through the center point Q, one of the primary light and the -1st order light can be effectively dimmed with respect to the other light.

Further, as in the present embodiment, when the boundary line D2 is a straight line and the inclination angle θ ₁ of the straight line D1 with respect to the square lattice is greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °, the square lattice _{The inclination angle θ 2} of the boundary line D2 with respect to the relative line D2 may be greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °. Thereby, one of the primary light and the -1st order light can be effectively dimmed with respect to the other light. In particular, when the light intensities of the four traveling waves AU, AD, AR, and AL are substantially equal, the inclination angle θ ₂ of the boundary line D2 with respect to the square lattice is 135 ° or 315 °, so that it is primary. One of the light and the -1st order light can be dimmed more effectively with respect to the other light.

Alternatively, if the boundary line D2 is a straight line and the inclination angle θ ₁ of the straight line D1 with respect to the square grid is greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °, the inclination angle of the boundary line D2 with respect to the square grid. θ ₂ may be greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °. Thereby, one of the primary light and the -1st order light can be effectively dimmed with respect to the other light. In particular, when the light intensities of the four traveling waves AU, AD, AR, and AL are substantially equal, the inclination angle θ ₂ of the boundary line D2 with respect to the square lattice is 45 ° or 225 °, so that it is primary. One of the light and the -1st order light can be dimmed more effectively with respect to the other light.

Further, as in the present embodiment, the light emitting portion may be an active layer 12 provided on the semiconductor substrate 10. As a result, the light emitting unit and the phase modulation layer 15 can be easily photocoupled.

Further, as illustrated in FIG. 9, a plurality of different refractive index regions 15b are formed inside the inner region RIN2, and the outer region ROUT2 surrounding the inner region RIN2 does not include the different refractive index region 15b and the basic layer 15a. May consist only of. Then, the inner region RIN2 may be included in the electrode 16 when viewed from the thickness direction of the phase modulation layer 15. As shown in FIGS. 23 to 26, the light intensities of the four traveling waves AU, AD, AR, and AL increase toward the end of the periodic structure with the plurality of different refractive index regions 15b. Therefore, a high electric field strength exists in the vicinity of the end face of the phase modulation layer 15, and the in-plane loss becomes large. On the other hand, in the structure illustrated in FIG. 9, the gain region through which the current flows is larger than that of the inner region RIN2 including the plurality of different refractive index regions 15b. Therefore, the in-plane loss in the vicinity of the end face of the phase modulation layer 15 can be reduced.

(First modification)
29 and 30 are plan views showing an example of the shape of the different refractive index region 15b in the XY plane. In the above embodiment, an example is shown in which the shape of the different refractive index region 15b in the XY plane is circular. However, the different refractive index region 15b may have a shape other than a circle. For example, the shape of the different refractive index region 15b in the XY plane may have mirror image symmetry (line symmetry). Here, the mirror image symmetry (line symmetry) refers to the planar shape of the different refractive index region 15b located on one side of the straight line and the other side of the straight line with a straight line along the XY plane in between. It means that the planar shape of the located different refractive index region 15b can be mirror image symmetric (line symmetric) with each other. Examples of the shape having mirror image symmetry (line symmetry) include a perfect circle shown in FIG. 29 (a), a square shown in FIG. 29 (b), and a regular hexadecagon shown in FIG. 29 (c). The regular octagon shown in FIG. 29 (d), the regular hexadecagon shown in FIG. 29 (e), the rectangle shown in FIG. 29 (f), the ellipse shown in FIG. 29 (g), and the like. Can be mentioned. As described above, the shape of the different refractive index region 15b in the XY plane has mirror image symmetry (line symmetry). In this case, since each of the unit constituent regions R of the virtual square lattice of the phase modulation layer 15 has a simple shape, the direction and position of the center of gravity G of the corresponding different refractive index region 15b from the lattice point O can be accurately determined. Since it can be determined, patterning with high accuracy becomes possible.

Further, the shape of the different refractive index region 15b in the XY plane may be a shape that does not have rotational symmetry of 180 °. Such shapes include, for example, a regular triangle shown in FIG. 30 (a), a right-angled isosceles triangle shown in FIG. 30 (b), and a part of two circles or an ellipse shown in FIG. 30 (c). The shape is deformed so that the dimension in the minor axis direction near one end along the long axis of the rectangle shown in FIG. 30 (d) is smaller than the dimension in the minor axis direction near the other end. Shape (oval), one end along the long axis of the rectangle shown in FIG. 30 (e) deformed into a pointed end protruding along the long axis (tear shape), FIG. 30 The isosceles triangle shown in (f), one side of the rectangle shown in FIG. 30 (g) is recessed in a triangular shape, and the opposite side is pointed in a triangular shape (arrow shape), as shown in FIG. 30 (h). The trapezoid shown, the pentagon shown in FIG. 30 (i), the shape in which parts of the two rectangles shown in FIG. 30 (j) overlap each other, and the two rectangles shown in FIG. 30 (k). Examples thereof include a shape in which parts overlap each other and do not have mirror image symmetry. As described above, since the shape of the different refractive index region 15b in the XY plane does not have rotational symmetry of 180 °, a higher light output can be obtained.

(Second modification)
FIG. 31 is a plan view of the phase modulation layer 15A according to the second modification of the above embodiment. The phase modulation layer 15A of this modification further has a plurality of different refractive index regions 15c different from the plurality of different refractive index regions 15b in addition to the configuration of the phase modulation layer 15 of the above embodiment (FIG. 4). Each different refractive index region 15c is composed of a second refractive index medium having a refractive index different from that of the first refractive index medium of the basic layer 15a. The different refractive index region 15c may be a pore, or may be configured by embedding a compound semiconductor in the pore, similarly to the different refractive index region 15b. As shown in FIG. 32, in this modification, the center of gravity G, which is a combination of the center of gravity of each different refractive index region 15b and the center of gravity of each different refractive index region 15c, is arranged on the straight line D1. Both the different refractive index regions 15b and 15c are included in the range of the unit constituent region R constituting the virtual square lattice. The unit constituent area R is an area surrounded by a straight line that divides the lattice points of the virtual square lattice into two equal parts. The distance r (x, y) between the center of gravity G and the corresponding lattice point O of each unit constituent region R is differently refracted according to the phase P (x, y) defined based on the desired optical image. It is set individually for each rate region 15b. The distribution of the distance r (x, y) is determined from the extracted phase distribution of the complex amplitude distribution obtained by Fourier transforming the desired optical image. That is, in the region Fa (see FIG. 6) of the phase modulation layer 15, when the phase P (x, y) at a certain coordinate (x, y) is P ₀ , the distance r (x, y) is set to 0. When the phase P (x, y) is π + P ₀ , the distance r (x, y) is _{set to the maximum value R 0} , and when the phase P (x, y) is −π + P _0. Sets the distance r (x, y) to the minimum value −R _0. Then, for the intermediate phase P (x, y), the distance r (x, y) is r (x, y) = {P (x, y) −P ₀ } × R _{0 / π.} ). Further, in the region Fb (see FIG. 6) of the phase modulation layer 15, when the phase P (x, y) at a certain coordinate (x, y) is P ₀ , the distance r (x, y) is set to 0. When the phase P (x, y) is π + P ₀ , the distance r (x, y) is _{set to the minimum value −R 0} , and when the phase P (x, y) is −π + P _0. The distance r (x, y) is set to the _{maximum value R 0.} Then, for the intermediate phase P (x, y), the distance r (x, _{y) = − {P (x, y) −P 0} } × R _{0 / π.} Take y). The initial phase P ₀ can be set arbitrarily.

The different refractive index regions 15c are provided in a one-to-one correspondence with the different refractive index regions 15b, respectively. The planar shape of the different refractive index region 15c is, for example, circular, but it can have various shapes like the different refractive index region 15b. 33 (a) to 33 (k) show examples of the shapes and relative relationships of the different refractive index regions 15b and 15c in the XY plane. 33 (a) and 33 (b) show a form in which the different refractive index regions 15b and 15c have the same shape. 33 (c) and 33 (d) show a form in which the different refractive index regions 15b and 15c have the same shape and a part of each overlaps with each other. FIG. 33 (e) shows a form in which the different refractive index regions 15b and 15c have the same shape, and the distance between the centers of gravity of the different refractive index regions 15b and 15c is arbitrarily set for each lattice point. FIG. 33 (f) shows a form in which the different refractive index regions 15b and 15c have figures having different shapes from each other. FIG. 33 (g) shows a form in which the different refractive index regions 15b and 15c have different shapes, and the distance between the centers of gravity of the different refractive index regions 15b and 15c is arbitrarily set for each lattice point.

Further, as shown in FIGS. 33 (h) to 33 (k), the different refractive index region 15b may be configured to include two regions 15b1 and 15b2 that are separated from each other. Then, the distance between the center of gravity of the regions 15b1 and 15b2 (corresponding to the center of gravity of a single different refractive index region 15b) and the center of gravity of the different refractive index region 15c may be arbitrarily set for each lattice point. Further, in this case, as shown in FIG. 33 (h), the regions 15b1 and 15b2 and the different refractive index regions 15c may have shapes having the same shape as each other. Alternatively, as shown in FIG. 33 (i), two of the regions 15b1, 15b2 and the different refractive index region 15c may be different from the others. Further, as shown in FIG. 33 (j), in addition to the angle of the straight line connecting the regions 15b1 and 15b2 with respect to the X-axis, the angle of the Cartesian index region 15c with respect to the X-axis is arbitrarily set for each lattice point. May be good. Further, as shown in FIG. 33 (k), the angles of the straight lines connecting the regions 15b1, 15b2 with respect to the X axis are set for each grid point while the regions 15b1, 15b2 and the Cartesian index regions 15c maintain the same relative angles. It may be set arbitrarily.

The shapes of the different refractive index regions in the XY plane may be the same among the lattice points. That is, the different refractive index regions may have the same figure at all the lattice points, and the lattice points may be superposed on each other by a translation operation, or a translation operation and a rotation operation. In that case, it is possible to suppress the generation of noise light and 0th-order light that becomes noise in the beam pattern. Alternatively, the shape of the different refractive index region in the XY plane does not necessarily have to be the same between the lattice points, and the shapes may differ from each other between adjacent lattice points, for example, as shown in FIG. 34. In any of FIGS. 29 to 34, the center of the straight line D1 passing through each grid point may be set so as to coincide with the grid point O.

For example, even with the configuration of the phase modulation layer as in this modification, the effects of the above-described embodiment can be suitably exhibited.

(Third modification example)
FIG. 35 is a diagram showing a configuration of a light emitting device 1B according to a third modification. The light emitting device 1B comprises a support substrate 6, a plurality of semiconductor light emitting elements 1A arranged one-dimensionally or two-dimensionally on the support substrate 6, and a drive circuit 4 for individually driving the plurality of semiconductor light emitting elements 1A. I have. The configuration of each semiconductor light emitting device 1A is the same as that of the above embodiment. However, the plurality of semiconductor light emitting elements 1A include a laser element that outputs an optical image in the red wavelength region, a laser element that outputs an optical image in the blue wavelength region, and a laser element that outputs an optical image in the green wavelength region. May be included. The laser element that outputs an optical image in the red wavelength region is composed of, for example, a GaAs-based semiconductor. A laser element that outputs an optical image in the blue wavelength region and a laser element that outputs an optical image in the green wavelength region are composed of, for example, a nitride semiconductor. The drive circuit 4 is provided on the back surface or the inside of the support substrate 6, and drives each semiconductor light emitting element 1A individually. The drive circuit 4 supplies a drive current to each semiconductor light emitting element 1A according to an instruction from the control circuit 7.

As in this modification, a module in which a plurality of semiconductor light emitting elements 1A individually driven are provided and a desired light image is extracted from each semiconductor light emitting element 1A, so that semiconductor light emitting elements corresponding to a plurality of patterns are arranged in advance. A head-up display or the like can be suitably realized by appropriately driving necessary elements. Further, the plurality of semiconductor light emitting elements 1A include a laser element that outputs an optical image in the red wavelength region, a laser element that outputs an optical image in the blue wavelength region, and a laser element that outputs an optical image in the green wavelength region. Therefore, a color head-up display or the like can be preferably realized.

(Second Embodiment)
FIG. 36 is a diagram showing a cross-sectional structure of the semiconductor light emitting device 1C according to the second embodiment. The semiconductor light emitting element 1C is a laser light source that forms a standing wave in the XY in-plane direction and outputs a phase-controlled plane wave in the Z direction, and is the main surface of the semiconductor substrate 10 as in the first embodiment. A two-dimensional arbitrary-shaped optical image including a direction perpendicular to 10a and a direction inclined with respect to the direction is output. However, the semiconductor light emitting device 1A of the first embodiment outputs a light image transmitted through the semiconductor substrate 10 from the back surface, whereas the semiconductor light emitting device 1C of the present embodiment outputs the light image transmitted through the semiconductor substrate 10 from the front surface on the clad layer 13 side with respect to the active layer 12. Output an optical image.

The semiconductor light emitting device 1C includes a clad layer 11, an active layer 12, a clad layer 13, a contact layer 14, a phase modulation layer 15, a light reflection layer 20, and a current constriction layer 21. The clad layer 11 is provided on the semiconductor substrate 10. The active layer 12 is provided on the clad layer 11. The clad layer 13 is provided on the active layer 12. The contact layer 14 is provided on the clad layer 13. The phase modulation layer 15 is provided between the active layer 12 and the clad layer 13. The light reflecting layer 20 is provided between the active layer 12 and the clad layer 11. The current constriction layer 21 is provided in the clad layer 13. The configuration of each layer 11 to 15 (suitable material, band gap, refractive index, etc.) is the same as that of the first embodiment. The light reflecting layer 20 may be omitted if light absorption by the semiconductor substrate 10 is not a problem.

The structure of the phase modulation layer 15 is the same as the structure of the phase modulation layer 15 described in the first embodiment (see FIGS. 4 and 5). If necessary, an optical guide layer may be provided between the active layer 12 and the clad layer 13 and at least one of the active layer 12 and the clad layer 11. As shown in FIG. 37, the phase modulation layer 15 may be provided between the clad layer 11 and the active layer 12. The optical guide layer may include a carrier barrier layer for efficiently confining carriers in the active layer 12.

The semiconductor light emitting device 1C further includes an electrode 23 provided on the contact layer 14 and an electrode 22 provided on the back surface 10b of the semiconductor substrate 10. The electrode 23 is in ohmic contact with the contact layer 14, and the electrode 22 is in ohmic contact with the semiconductor substrate 10. FIG. 38 is a plan view of the semiconductor light emitting device 1C as viewed from the electrode 23 side (surface side). As shown in FIG. 38, the electrode 23 has a planar shape such as a frame shape (annular shape) and has an opening 23a. Although the square frame-shaped electrode 23 is illustrated in FIG. 38, the planar shape of the electrode 23 can be various shapes such as an annular shape. Further, the shape of the electrode 22 shown by the hidden line in FIG. 38 is similar to the shape of the opening 23a of the electrode 23, and is, for example, a square or a circle. The inner diameter of the opening 23a of the electrode 23 (the length of one side when the shape of the opening 23a is square) is, for example, 20 μm to 50 μm.

See FIG. 36 again. The contact layer 14 of the present embodiment has a planar shape similar to that of the electrode 23. That is, the central portion of the contact layer 14 is removed by etching to form an opening 14a, and the contact layer 14 has a planar shape such as a frame shape (annular shape). The light emitted from the semiconductor light emitting device 1C passes through the opening 14a of the contact layer 14 and the opening 23a of the electrode 23. By allowing light to pass through the opening 14a of the contact layer 14, it is possible to avoid light absorption in the contact layer 14 and improve the light emission efficiency. However, if the light absorption in the contact layer 14 is acceptable, the contact layer 14 may cover the entire surface on the clad layer 13 without having the opening 14a. By passing the light through the opening 23a of the electrode 23, the light can be suitably emitted from the surface side of the semiconductor light emitting device 1C without being blocked by the electrode 23.

The surface of the clad layer 13 exposed from the opening 14a of the contact layer 14 (or the surface of the contact layer 14 when the opening 14a is not provided) is covered with the antireflection film 25. An antireflection film 25 may be provided on the outside of the contact layer 14. Further, the portion other than the electrode 22 on the back surface 10b of the semiconductor substrate 10 is covered with the protective film 24. The material of the protective film 24 is the same as that of the protective film 18 of the first embodiment. The material of the antireflection film 25 is the same as that of the antireflection film 19 of the first embodiment.

The light reflecting layer 20 reflects the light generated in the active layer 12 toward the surface side of the semiconductor light emitting device 1C. The light reflecting layer 20 is composed of, for example, a DBR (Disrtibuted Bragg Reflector) layer in which a plurality of layers having different refractive indexes are alternately laminated. Although the light reflecting layer 20 of the present embodiment is provided between the active layer 12 and the clad layer 11, the light reflecting layer 20 may be provided between the clad layer 11 and the semiconductor substrate 10. Alternatively, the light reflecting layer 20 may be provided inside the clad layer 11.

The clad layer 11 and the light reflecting layer 20 are provided with the same conductive type as the semiconductor substrate 10, and the clad layer 13 and the contact layer 14 are provided with the same conductive type as the semiconductor substrate 10. In one example, the semiconductor substrate 10, the clad layer 11 and the light reflecting layer 20 are n-type, and the clad layer 13 and the contact layer 14 are p-type. The phase modulation layer 15 has the same conductive type as the semiconductor substrate 10 when it is provided between the active layer 12 and the clad layer 11, and is a semiconductor when it is provided between the active layer 12 and the clad layer 13. It has a conductive type opposite to that of the substrate 10. The impurity concentration is, for example, 1 × 10 ¹⁷ to 1 × 10 ²¹ / cm ³ . The active layer 12 is genuine (type i) to which no impurities are intentionally added, and the impurity concentration thereof is 1 × 10 ¹⁵ / cm ³ or less. The impurity concentration of the phase modulation layer 15 may be intrinsic (i type) when it is necessary to suppress the influence of loss due to light absorption via the impurity level.

The current constriction layer 21 has a structure that makes it difficult (or does not allow) the current to pass through, and has an opening 21a at the center. As shown in FIG. 38, the planar shape of the opening 21a is similar to the shape of the opening 23a of the electrode 23, and is, for example, square or circular. The current constriction layer 21 is, for example, an Al oxide layer obtained by oxidizing a layer containing Al at a high concentration. Alternatively, the current constriction layer 21 may be a layer formed by injecting a ^{proton (H +) into the clad layer 13.} Alternatively, the current constriction layer 21 may have an inverted pn junction structure in which a conductive semiconductor layer opposite to the semiconductor substrate 10 and a conductive semiconductor layer same as the semiconductor substrate 10 are laminated in this order.

A dimensional example of the semiconductor light emitting device 1C of this embodiment will be described. The inner diameter of the opening 23a of the electrode 23 (the length of one side when the shape of the opening 23a is square) La is in the range of 5 μm to 100 μm, for example, 50 μm. The thickness ta of the phase modulation layer 15 is, for example, in the range of 100 nm to 400 nm, for example, 200 nm. The distance tb between the current constriction layer 21 and the contact layer 14 is in the range of 2 μm to 50 μm. In other words, the interval tb is in the range of 0.02La-10La (eg 0.1La) and in the range 5.0ta-500ta (eg 25ta). Further, the thickness tc of the clad layer 13 is larger than the interval tb and is in the range of 2 μm to 50 μm. In other words, the thickness tc is in the range of 0.02La to 10La (for example, 0.1La) and in the range of 5.0ta to 500ta (for example, 25ta). The thickness td of the clad layer 11 is in the range of 1.0 μm to 3.0 μm (for example, 2.0 μm).

When a drive current is supplied between the electrode 22 and the electrode 23, the drive current reaches the active layer 12. At this time, the current flowing between the electrode 23 and the active layer 12 is sufficiently diffused in the thick clad layer 13 and passes through the opening 21a of the current constriction layer 21 so as to be uniform near the central portion of the active layer 12. Can spread to. Then, recombination of electrons and holes occurs in the active layer 12, and the active layer 12 emits light. The electrons and holes that contribute to this light emission, as well as the generated light, are efficiently confined between the clad layer 11 and the clad layer 13. The laser beam emitted from the active layer 12 enters the inside of the phase modulation layer 15 and forms a predetermined mode according to the lattice structure inside the phase modulation layer 15. The laser light emitted from the phase modulation layer 15 is reflected by the light reflection layer 20, and is emitted from the clad layer 13 to the outside through the openings 14a and 23a.

但し、ｋ₀＝２π／λ₀、λ₀は発振波長、β₀＝２π／ａ、ａは格子定数、ξ_±2,0は孔形状のフーリエ係数のうち次数（±２，０）に対応するもの、θ₀（ｚ）は積層方向の電界分布であり、積分全体では層方向の電界強度分布のうち位相変調層１５に存在する割合を表す。 (Specific Example 1 of the First Embodiment)
Here, with respect to the above-described first embodiment, the effect of suppressing unnecessary light among the primary light and the -1st order light is estimated, and the shape range in which a particularly large effect can be obtained is examined. For the sake of simplicity, the distribution of the in-plane traveling wave is assumed to be the same as that of the square lattice, and the intensity distribution of the four fundamental waves (traveling wave AU, AD, AR, and AL) is calculated using the three-dimensional coupled wave theory. rice field. The three-dimensional coupled wave theory is described in the literature "Y. Liang et al.," Three-dimensional coupled-wave model forsquare-lattice photonic crystal lasers with transverse electric polarization: Ageneral approach ", Phys. Rev. B84, 195119 (2011). ). ”And the literature“ Y. Liang et al., “Three-dimensional coupled-wave analysis for square-lattice photonic crystal surface emitting lasers with transverse-electric polarization: finite-size effects”, Opt. Express20, 15945-15961 (2012) ."It is described in. The optical coupling coefficient κ corresponding to 180 ° diffraction, that is, coupling to a wave traveling in the opposite direction, was calculated using the following mathematical formula (26).

However, k ₀ = 2π / λ ₀ , λ ₀ corresponds to the oscillation wavelength, β ₀ = 2π / a, a corresponds to the lattice constant, and ξ _{± 2,0} corresponds to the order (± 2,0) of the hole-shaped Fourier coefficients. Θ ₀ (z) is the electric field distribution in the stacking direction, and represents the ratio of the electric field strength distribution in the layer direction existing in the phase modulation layer 15 in the entire integration.

Further, FIG. 39 is a chart showing the layer structure used in the calculation in this example. Layer numbers 1 and 2 indicate the upper clad layer 13, layer number 3 indicates the phase modulation layer 15, layer number 4 indicates the optical guide layer, layer numbers 5 to 13 indicate the active layer 12, and layer number 14 indicates the lower clad layer 11. FIG. 40 shows the refractive index distribution G11a and the mode distribution G11b of the semiconductor light emitting device 1A having the layer structure shown in FIG. 39. The horizontal axis represents the position in the stacking direction.

41 to 52 show calculation results when the planar shape of the phase modulation layer 15 is a perfect circle. The calculation was performed assuming that FF was 15% and R ₀ = 0, that is, a cubic lattice structure for simplicity. 41 and 42 show the case where the cavity length L = 1 μm (κL = 0.097). 43 and 44 show the case where the cavity length L = 4 μm (κL = 0.389). 45 and 46 show the case where the cavity length L = 10 μm (κL = 0.973). 47 and 48 show the case where the cavity length L = 20 μm (κL = 1.945). 49 and 50 show the case where the cavity length L = 50 μm (κL = 4.864). 51 and 52 show the case where the cavity length L = 100 μm (κL = 9.727). In addition, FIG. 41, FIG. 43, FIG. 45, FIG. 47, FIG. 49, and FIG. 51 (a) are graphs showing the in-plane distribution of the light intensity of the traveling wave AR. 41, 43, 45, 47, 49, and 51 (b) are graphs showing the in-plane distribution of the light intensity of the traveling wave AL. 42, 44, 46, 48, 50, and 52 (a) are graphs showing the in-plane distribution of the light intensity of the traveling wave AU. 42, 44, 46, 48, 50, and 52 (b) are graphs showing the in-plane distribution of the light intensity of the traveling wave AD. In these figures, the intensity distribution of the traveling wave is represented by an isointensity line, the horizontal axis represents the position in the X-axis direction, and the vertical axis represents the position in the Y-axis direction. In addition, FIG. 41, FIG. 43, FIG. 45, FIG. 47, FIG. 49, and FIG. 51 (c) are graphs showing the results of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. be. 42, 44, 46, 48, 50, and 52 (c) are graphs showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. In these figures, the horizontal axis represents the position in the X-axis direction, and the vertical axis represents the difference value.

With reference to FIGS. 41 to 52, the smaller the resonator length L and the smaller the product κL of the optical coupling coefficient κ and the resonator length L, the more the light intensities of the traveling waves AU, AD, AR, and AL. It can be seen that the in-plane distribution is highly biased. In particular, it can be seen that in the range where the resonator length L is smaller than 100 μm and κL is smaller than 10, the distribution of the light intensity of each traveling wave is largely biased, and the difference between the traveling waves traveling in the opposite directions is largely biased.

Figure 53 (a), the ratio of the case the planar shape of the phase modulation layer 15 is a perfect circle, -1 order light intensity J _-1 and intensity J ₁ of the primary light (J _-1 / J ₁ ) And the resonator length L. The horizontal axis represents the cavity length L (μm), and the vertical axis represents the intensity ratio (J _-1 / J ₁ ). Graph G12a in the figure shows the result of this embodiment. The graph G12b in the figure shows the result when the regions Fa and Fb are not divided (the phase difference of π (rad) is not given) for comparison. _{Further, FIG. 53 (b) shows the product κL of the intensity ratio (J -1} / J ₁ ), the cavity length L, and the optical coupling coefficient κ when the planar shape of the phase modulation layer 15 is a perfect circle. It is a graph which shows the relationship of. The horizontal axis represents κL and the vertical axis represents the intensity ratio (J _-1 / J ₁ ). Graph G13a in the figure shows the result of this embodiment. The graph G13b in the figure shows the result when the regions Fa and Fb are not divided (the phase difference of π (rad) is not given) for comparison.

With reference to (a) and (b) of FIG. 53, it can be seen that the shorter the cavity length L and the smaller the kappa L, the smaller the intensity ratio (J _-1 / J _1). Further, as the cavity length L is shorter and κL is smaller, the difference in the intensity ratio (J _-1 / J ₁ ) with respect to the case where the phase difference of π (rad) is not given is widened (that is, in the above embodiment). It can be seen that the effect has been obtained). In particular, when the cavity length L is shorter than 100 μm and κL is smaller than 10, the intensity ratio (J _-1 / J ₁ ) becomes significantly smaller, and the intensity when no phase difference of π (rad) is given. The difference in ratio (J _-1 / J ₁ ) is significantly widened. Therefore, in the above embodiment, it is desirable that the cavity length L is shorter than 100 μm or κL is smaller than 10.

54 to 59 show calculation results when the planar shape of the phase modulation layer 15 is an isosceles triangle. _{The maximum value R 0} of FF and the distance r (x, y) is the same as when the plane shape of the phase modulation layer 15 is a perfect circle. FIG. 54 shows the case where the cavity length L = 1 μm (κL = 0.083). FIG. 55 shows the case where the cavity length L = 4 μm (κL = 0.333). FIG. 56 shows the case where the cavity length L = 10 μm (κL = 0.834). FIG. 57 shows the case where the cavity length L = 20 μm (κL = 1.667). FIG. 58 shows the case where the cavity length L = 50 μm (κL = 4.168). FIG. 59 shows the case where the cavity length L = 100 μm (κL = 8.337). (A) of FIGS. 54 to 59 is a graph showing the result of integrating the difference between the light intensity of the traveling wave AR and the light intensity of the traveling wave AL. (B) of FIGS. 54 to 59 is a graph showing the result of integrating the difference between the light intensity of the traveling wave AU and the light intensity of the traveling wave AD. In these figures, the horizontal axis represents the position in the X-axis direction, and the vertical axis represents the difference value.

With reference to FIGS. 54 to 59, even when the planar shape of the phase modulation layer 15 is an isosceles triangle, the smaller the resonator length L, the larger the product κL of the optical coupling coefficient κ and the resonator length L. It can be seen that the smaller the value, the greater the deviation of the in-plane distribution of the light intensities of the traveling waves AU, AD, AR, and AL. In particular, in the range where the resonator length L is smaller than 100 μm and κL is smaller than 10, the distribution of the light intensity of each traveling wave is largely biased, and the difference between the traveling waves traveling in the opposite directions is large. That is, such a tendency can be considered to be irrelevant to the planar shape of the phase modulation layer 15.

FIG. 60A is a graph showing the relationship between _{the cavity length L and the intensity ratio (J -1} / J ₁ ) when the plane shape of the phase modulation layer 15 is an isosceles triangle. The horizontal axis represents the cavity length L (μm), and the vertical axis represents the intensity ratio (J _-1 / J ₁ ). Graph G14a in the figure shows the result of this embodiment. The graph G14b in the figure shows the result when the regions Fa and Fb are not divided (the phase difference of π (rad) is not given) for comparison. Further, FIG. 60B is a graph showing the relationship between _{κL and the intensity ratio (J -1} / J ₁ ) when the planar shape of the phase modulation layer 15 is an isosceles triangle. The horizontal axis represents κL and the vertical axis represents the intensity ratio (J _-1 / J ₁ ). Graph G15a in the figure shows the result of this embodiment. The graph G15b in the figure shows the result when the regions Fa and Fb are not divided (the phase difference of π (rad) is not given) for comparison.

With reference to FIGS. 60A and 60B, even when the plane shape of the phase modulation layer 15 is an isosceles triangle, the shorter the cavity length L and the smaller the kappaL, the stronger the intensity ratio (J _-1 /). It can be seen that _{J 1) is small.} Further, as the cavity length L is shorter and κL is smaller, the difference in the intensity ratio (J _-1 / J ₁ ) with respect to the case where the phase difference of π (rad) is not given is widened (that is, in the above embodiment). It can be seen that the effect has been obtained). In particular, when the cavity length L is shorter than 100 μm and κL is smaller than 10, the intensity ratio (J _-1 / J ₁ ) becomes significantly smaller, and the intensity when no phase difference of π (rad) is given. The difference in ratio (J _-1 / J ₁ ) is significantly widened. Therefore, it is desirable that the resonator length L is shorter than 100 μm or κL is smaller than 10 regardless of the planar shape of the phase modulation layer 15.

(Specific Example 2 of the First Embodiment)
The inventors examined the conditions under which the higher-order mode does not occur with respect to the thickness and refractive index of the optical waveguide layer including the active layer and the thickness and refractive index of the contact layer. The examination process and results will be described below.

First, the specific structure of the semiconductor light emitting device 1A to be examined in this specific example will be described. FIG. 61 is a table showing a layer structure when the semiconductor light emitting device 1A is made of a GaAs-based compound semiconductor (emission wavelength 940 nm band). The table of FIG. 61 shows the conductivity type, composition, layer thickness, and refractive index of each layer. The layer number 1 is the contact layer 14, the layer number 2 is the upper clad layer 13, the layer number 3 is the phase modulation layer 15, the layer number 4 is the optical guide layer and the active layer 12, and the layer number 5 is the lower clad layer 11. .. FIG. 62 shows the refractive index distribution G21a and the mode distribution G21b of the semiconductor light emitting device 1A having the layer structure shown in FIG. The horizontal axis represents the stacking direction position (range is 2.5 μm). At this time, it can be seen that only the basic mode is generated and the higher-order mode is suppressed.

FIG. 63 is a table showing a layer structure when the semiconductor light emitting device 1A is made of an InP-based compound semiconductor (emission wavelength 1300 nm band). Layer number 1 is the contact layer 14, layer number 2 is the upper clad layer 13, layer number 3 is the phase modulation layer 15, layer number 4 is the optical guide layer and the active layer 12, and layer number 5 is the lower clad layer 11. FIG. 64 shows the refractive index distribution G22a and the mode distribution G22b of the semiconductor light emitting device 1A having the layer structure shown in FIG. The horizontal axis represents the stacking direction position (range is 2.5 μm). At this time, it can be seen that only the basic mode is generated and the higher-order mode is suppressed.

FIG. 65 is a table showing a layer structure when the semiconductor light emitting device 1A is made of a nitride compound semiconductor (emission wavelength 405 nm band). Layer number 1 is the contact layer 14, layer number 2 is the upper clad layer 13, layer number 3 is the carrier barrier layer, layer number 4 is the active layer 12, layer number 5 is the optical guide layer, and layer number 6 is the phase modulation layer 15. Layer number 7 indicates the lower clad layer 11. FIG. 66 shows the refractive index distribution G23a and the mode distribution G23b of the semiconductor light emitting device 1A having the layer structure shown in FIG. 65. The horizontal axis represents the stacking direction position (range is 2.5 μm). At this time, it can be seen that only the basic mode is generated and the higher-order mode is suppressed.

In each of the above structures, the filling factor (FF) of the phase modulation layer 15 is 15%. The filling factor is the ratio of the area of the different refractive index region 15b to one unit constituent region R.

Next, the preconditions for the study will be described. In the following examination, TE mode was assumed. That is, the leak mode and the TM mode are not considered. Further, the lower clad layer 11 is sufficiently thick, and the influence of the semiconductor substrate 10 can be ignored. Further, the refractive index of the upper clad layer 13 is equal to or less than the refractive index of the lower clad layer 11. The active layer 12 (MQW layer) and the optical guide layer are regarded as one optical waveguide layer (core layer) having an average dielectric constant and a total film thickness unless otherwise specified. Further, the dielectric constant of the phase modulation layer 15 is an average dielectric constant based on the filling factor.

The formulas for calculating the average refractive index and film thickness of the optical waveguide layer composed of the active layer 12 and the optical guide layer are as follows. That is, ε _core is the average dielectric constant of the optical waveguide layer, and is defined by the following equation (27). ε _i is the permittivity of each layer, d _i is the thickness of each layer, and n _i is the refractive index of each layer. n _core is the average refractive index of the optical waveguide layer and is defined by the following equation (28). The d _core is the film thickness of the optical waveguide layer and is defined by the following formula (29).

The formula for calculating the average refractive index of the phase modulation layer 15 is as follows. That is, n _PM is the average refractive index of the phase modulation layer 15, and is defined by the following equation (30). ε _PM is the dielectric constant of the phase modulation layer 15, n ₁ is the refractive index of the first refractive index medium, n ₂ is the refractive index of the second refractive index medium, and FF is the filling factor.

In the following studies, the waveguide structure was approximated by a 5-layer or 6-layer slab-type waveguide. FIGS. 67 (a) and 67 (b) are a cross-sectional view and a refractive index distribution for explaining a case where the waveguide structure is approximated by a six-layer slab type waveguide. FIGS. 68 (a) and 68 (b) are a cross-sectional view and a refractive index distribution for explaining a case where the waveguide structure is approximated by a five-layer slab type waveguide. As shown in FIGS. 67 (a) and 67 (b), when the refractive index of the phase modulation layer 15 is smaller than the refractive index of the lower clad layer 11, the phase modulation layer 15 does not have a waveguide function. An approximation was made for the 6-layer slab-type waveguide. That is, the optical waveguide layer has a structure that includes the active layer 12 and the optical guide layer, but does not include the lower clad layer 11, the upper clad layer 13, and the phase modulation layer 15. Such an approximation can be applied to, for example, the structures shown in FIGS. 63 and 65 (in P-based compound semiconductors or nitride-based compound semiconductors in this embodiment).

Further, as shown in FIGS. 68 (a) and 68 (b), when the refractive index of the phase modulation layer 15 is equal to or higher than the refractive index of the lower clad layer 11, the phase modulation layer 15 has a waveguide function. Therefore, an approximation was made for the five-layer slab-type waveguide. That is, the optical waveguide layer has a structure that includes the phase modulation layer 15 and the active layer 12, but does not include the lower clad layer 11 and the upper clad layer 13. Such an approximation can be applied, for example, to the structure shown in FIG. 25 (GaAs-based compound semiconductor in this embodiment).

Further, in order to further simplify the calculation, the calculation range is limited to the peripheral portions of the optical waveguide layer and the contact layer, which have a refractive index higher than the equivalent refractive index of the semiconductor light emitting device 1A. That is, the optical waveguide layer and the upper and lower layers adjacent to the optical waveguide layer define a three-layer slab structure for the optical waveguide layer, and the contact layer 14 and the adjacent upper and lower layers form a three-layer slab structure for the contact layer 14. Is regulated.

69 (a) and 69 (b) are cross sections for explaining a three-layer slab structure relating to an optical waveguide layer in a six-layer slab-type waveguide (see FIGS. 67 (a) and 67 (b)). The figure and the refractive index distribution. In this case, the waveguide mode of the optical waveguide layer is calculated based on the refractive index distribution shown by the solid line in the refractive index distribution of FIG. 69 (b). Further, FIGS. 70 (a) and 70 (b) are for explaining a three-layer slab structure relating to the contact layer 14 in the six-layer slab type waveguide (see FIGS. 67 (a) and 67 (b)). It is a cross-sectional view and a refractive index distribution of. In this case, the waveguide mode of the contact layer 14 is calculated based on the refractive index distribution shown by the solid line in FIG. 70 (b).

71 (a) and 71 (b) are a cross-sectional view and a refractive index distribution for explaining a three-layer slab structure relating to an optical waveguide layer in a five-layer slab-type waveguide (see FIG. 68). In this case, the waveguide mode of the optical waveguide layer is calculated based on the refractive index distribution shown by the solid line in FIG. 71 (b). Further, FIGS. 72 (a) and 72 (b) are a cross-sectional view and a refractive index distribution for explaining a three-layer slab structure relating to the contact layer 14 in the five-layer slab type waveguide (see FIG. 68). .. In this case, the waveguide mode of the contact layer 14 is calculated based on the refractive index distribution shown by the solid line in FIG. 72 (b).

In addition, in the above-mentioned approximation by the three-layer slab structure, the refractive index of the lower clad layer 11 is the equivalent refraction of the semiconductor light emitting device 1A in order to prevent the waveguide mode from leaking to the semiconductor substrate 10 through the lower clad layer 11. Must be below the rate.

Here, the analysis formula of the three-layer slab structure will be described. 73 (a) and 73 (b) show a three-layer slab structure 30 composed of a lower clad layer 11, an optical waveguide layer 31, and an upper clad layer 13, and a refractive index distribution thereof. Here, the refractive index of the lower clad layer 11 is n ₂ , the refractive index of the optical waveguide layer 31 is n _1, and the refractive index of the upper clad layer 13 is n ₃ . When the standard influencing for good waveguide width V ₁ of the optical waveguide layer 31 is defined by the above formula (1), as long as it is within the range of solutions of standard influencing for good waveguide width V ₁ is the only one guided mode Is in basic mode only. However, when examining the waveguide mode of the above-mentioned 5-layer slab structure and 6-layer slab structure in the analysis formula of the 3-layer slab structure, it is necessary that the waveguide mode does not leak to the lower clad layer 11, so the above formula (2) ) Must also be met at the same time.

Regarding the contact layer 14, in FIGS. 73 (a) and 73 (b), the lower clad layer 11 is replaced with the upper clad layer 13, the optical waveguide layer 31 is replaced with the contact layer 14, and the upper clad layer 13 is replaced with the air layer. It is good. Then, assuming that the refractive index of the contact layer 14 is n ₄ and the refractive index of the air layer is n ₅ , the above equation (5) relating to the normalized waveguide width V _{2 of the contact layer 14 is obtained.} Then, as long as there is no solution for the normalized waveguide width V ₂ , there is no waveguide mode in the contact layer 14. However, when examining the waveguide mode of the above-mentioned 5-layer slab structure and 6-layer slab structure in the analysis formula of the 3-layer slab structure, it is necessary that the waveguide mode does not leak to the lower clad layer 11, so the above formula (6) ) Must also be met at the same time.

By analyzing the waveguide mode generated by changing the film thickness of the upper clad layer 13, it was confirmed that the film thickness of the upper clad layer 13 does not affect the waveguide mode.

(When the semiconductor light emitting device 1A is made of a GaAs compound semiconductor)
FIG. 74 is a table showing an example of a five-layer slab structure when the semiconductor light emitting device 1A is made of a GaAs-based compound semiconductor. The range of film thicknesses of the optical waveguide layer (layer number 4) and the contact layer (layer number 2) in this five-layer slab structure can be obtained by the following calculation.

FIG. 75 (a) is a table showing _{the refractive indexes n 1} , n ₂ , and n _{3 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer 11 used in the calculation. In this case, the equation standards influencing for good waveguide width V ₁ of the optical waveguide layer, indicated by (1) and (2), the relationship between the normalized propagation coefficients b, is shown in Figure 76. In FIG. 76, graphs G31a to G31f show the case where the mode order N = 0 to 5, respectively. In this graph, the waveguide mode is only the basic mode (that is, N = 0) in the range where the solution of the _{normalized waveguide width V 1} is one, and is inside _{the range H 1.} In the range H _{1 , the lower limit value is the value of the normalized waveguide width V 1} corresponding to N = 0 when the normalized propagation coefficient b is 0, and N = 1 when the normalized propagation coefficient b is 0. The upper limit is the value of the normalized waveguide width V _{1 corresponding to.} FIG. 75B is a table showing the calculation results of such a lower limit value and an upper limit value.

In addition, FIG. 77 (a) is a table showing _{the refractive indexes n 4} , n ₅ , and n ₆ , the asymmetric parameter a', and the refractive index n _{clad of the lower clad layer 11 used in the calculation.} In this case, the above equation (5) and standards influencing for good waveguide width V ₂ of the contact layer 14 as indicated by the equation (6), the relationship between the normalized propagation coefficients b, is shown in Figure 78. In FIG. 78, graphs G32a to G32f show the case where the mode order N = 0 to 5, respectively. In this graph, the guided mode due to the contact layer 14 does not occur, the waveguide mode of the semiconductor light emitting device 1A is only the fundamental mode of the optical waveguide layer is no solution standards influencing for good waveguide width V ₂ range a is a inner range H _2. In the range H ₂ , the lower limit value is 0, and the value of the normalized _{waveguide width V 2} corresponding to N = 0 when the _{normalized propagation coefficient b is the value b 1} corresponding to the refractive index of the lower clad layer 11 is set. This is the upper limit range. FIG. 77 (b) is a table showing the calculation result of such an upper limit value.

FIG. 79 shows the refractive index distribution G24a and the mode distribution G24b of the semiconductor light emitting device 1A having the layer structure shown in FIG. 74. It can be seen that only the basic mode is remarkably generated, and the higher-order mode is suppressed.

(When the semiconductor light emitting device 1A is made of an InP compound semiconductor)
FIG. 80 is a table showing an example of a 6-layer slab structure when the semiconductor light emitting device 1A is made of an InP-based compound semiconductor. The range of film thicknesses of the optical waveguide layer (layer number 5) and the contact layer (layer number 2) in this 6-layer slab structure can be obtained by the following calculation.

FIG. 81 (a) is a table showing _{the refractive indexes n 1} , n ₂ , and n _{3 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer 11 used in the calculation. In this case, the equation standards influencing for good waveguide width V ₁ of the optical waveguide layer, indicated by (1) and (2), the relationship between the normalized propagation coefficients b, is shown in Figure 82. In FIG. 82, graphs G33a to G33f show the case where the mode order N = 0 to 5, respectively. In this graph, the waveguide mode is only the basic mode (that is, N = 0) in the range where the solution of the _{normalized waveguide width V 1} is one, and is inside _{the range H 1.} The definition of the range H ₁ is the same as that for the GaAs-based compound semiconductor described above. FIG. 81B is a table showing the calculation results of the lower limit value and the upper limit value.

Further, FIG. 83 (a) is a table showing _{the refractive indexes n 4} , n ₅ , and n ₆ , the asymmetric parameter a', and the refractive index n _{clad of the lower clad layer 11 used in the calculation. In this case, the relationship between the normalized waveguide width V 2 of the} contact layer 14 represented by the above equations (5) and (6) and the normalized propagation coefficient b is as shown in the graph shown in FIG. 84. In FIG. 84, graphs G34a to G34f show the case where the mode order N = 0 to 5, respectively. In this graph, the waveguide mode caused by the contact layer 14 does not occur, and the waveguide mode of the semiconductor light emitting device 1A is only the basic mode of the optical waveguide layer in the range where there is no solution of the _{normalized waveguide width V 2.} And is inside the range H _2. The definition of the range H ₂ is the same as in the case of the GaAs-based compound semiconductor described above. FIG. 83 (b) is a table showing the calculation result of such an upper limit value.

FIG. 85 shows the refractive index distribution G25a and the mode distribution G25b of the semiconductor light emitting device 1A having the layer structure shown in FIG. 80. It can be seen that only the basic mode occurs remarkably, and the higher-order mode is suppressed.

(When the semiconductor light emitting device 1A is made of a nitride compound semiconductor)
FIG. 86 is a table showing an example of a 6-layer slab structure when the semiconductor light emitting device 1A is made of a nitride compound semiconductor. The range of film thicknesses of the optical waveguide layer (layer number 4) and the contact layer (layer number 2) in this 6-layer slab structure can be obtained by the following calculation.

FIG. 87 (a) is a table showing _{the refractive indexes n 1} , n ₂ , and n _{3 , the asymmetric parameter a'and} the refractive index n clad of the lower clad layer 11 used in the calculation. _{In this case, the relationship between the normalized waveguide width V 1 of the} optical waveguide layer represented by the above equations (1) and (2) and the normalized propagation coefficient b is shown in FIG. 88. In FIG. 88, graphs G35a to G35f show the case where the mode order N = 0 to 5, respectively. In this graph, the waveguide mode is only the basic mode (that is, N = 0) in the range where the solution of the _{normalized waveguide width V 1} is one, and is inside _{the range H 1.} The range H _{1 is when the value of the normalized waveguide width V 1} corresponding to N = 0 when the normalized propagation coefficient b is the value b ₁ is set as the lower limit value and the normalized propagation coefficient b is the value b _1. The upper limit is the value of the normalized _{waveguide width V 1} corresponding to N = 1. FIG. 87B is a table showing the calculation results of the lower limit value and the upper limit value.

In addition, FIG. 89 (a) is a table showing _{the refractive indexes n 4} , n ₅ , and n ₆ , the asymmetric parameter a', and the refractive index n _{clad of the lower clad layer 11 used in the calculation. In this case, the relationship between the normalized waveguide width V 2 of the} contact layer 14 represented by the above equations (5) and (6) and the normalized propagation coefficient b is shown in FIG. 90. In FIG. 90, graphs G36a to G36f show the case where the mode order N = 0 to 5, respectively. In this graph, the waveguide mode caused by the contact layer 14 does not occur, and the waveguide mode of the semiconductor light emitting device 1A is only the basic mode of the optical waveguide layer in the range where there is no solution of the _{normalized waveguide width V 2.} And is inside the range H _2. The definition of the range H ₂ is the same as in the case of the GaAs-based compound semiconductor described above. FIG. 89B is a table showing the calculation results of such an upper limit value.

FIG. 91 shows the refractive index distribution G26a and the mode distribution G26b of the semiconductor light emitting device 1A having the layer structure shown in FIG. It can be seen that only the basic mode occurs remarkably, and the higher-order mode is suppressed.

The light emitting device according to the present invention is not limited to the above-described embodiment, and various other modifications are possible. For example, in the above embodiment, a laser device made of a GaAs-based, InP-based, and nitride-based (particularly GaN-based) compound semiconductor has been exemplified, but the present invention is applied to a laser device made of various semiconductor materials other than these. can.

Further, in the above embodiment, an example in which the active layer 12 provided on the semiconductor substrate 10 common to the phase modulation layer 15 is used as the light emitting portion has been described, but in the present invention, the light emitting portion is separated from the semiconductor substrate 10. It may be provided. As long as the light emitting unit is optically coupled to the phase modulation layer and supplies light to the phase modulation layer, the same effect as that of the above embodiment can be suitably exhibited even with such a configuration.

1A, 1C ... semiconductor light emitting element, 1B ... light emitting device, 4 ... drive circuit, 6 ... support substrate, 7 ... control circuit, 10 ... semiconductor substrate, 10a ... main surface, 10b ... back surface, 11, 13 ... clad layer, 12 ... Active layer, 14 ... Contact layer, 14a ... Aperture, 15, 15A ... Phase modulation layer, 15a ... Basic layer, 15b, 15c ... Different refractive index region, 16, 17, 22, 23 ... Electrode, 17a, 23a ... Aperture , 18, 24 ... Protective film, 19, 25 ... Antireflection film, 20 ... Light reflection layer, 21 ... Current constriction layer, 21a ... Aperture, a ... Lattice spacing, AD, AL, AR, AU ... Travel wave, B1 ... 1st light image part, B2 ... 2nd light image part, BD, BL, BR, BU ... beam pattern, D1 ... straight line, D2 ... boundary line, Fa ... 1st region, Fb ... 2nd region, G ... center of gravity, O ... lattice point, R ... unit constituent area, RIN1, RIN2 ... inner area, ROUT1, ROUT2 ... outer area.

Claims (12)

A light emitting device that outputs an optical image in a direction perpendicular to the main surface of the substrate, a direction inclined with respect to the main surface, or both.
Light emitting part and
A phase modulation layer provided on the substrate and optically coupled to the light emitting portion is provided.
The phase modulation layer includes a basic layer and a plurality of different refractive index regions having different refractive indexes from the basic layer.
When a virtual square lattice is set in a plane perpendicular to the thickness direction of the phase modulation layer, the center of gravity of the plurality of different refractive index regions passes through the lattice points of the virtual square lattice and the square lattice. Arranged on a first straight line that is inclined with respect to the light image, the distance between the center of gravity of each different refractive index region and the corresponding lattice point is individually set according to the phase defined based on the optical image. Lattice,
When the first region and the second region for dividing the phase modulation layer into two are set, the phase indicated by the position of the center of gravity of each different refractive index region in the second region is the different refractive index in the first region. A light emitting device having a phase difference of π (rad) with respect to the phase indicated by the position of the center of gravity of the rate region. A light emitting device that outputs an optical image in a direction perpendicular to the main surface of the substrate, a direction inclined with respect to the main surface, or both.
Light emitting part and
A phase modulation layer provided on the substrate and optically coupled to the light emitting portion is provided.
The phase modulation layer includes a basic layer and a plurality of different refractive index regions having different refractive indexes from the basic layer.
When a virtual square lattice is set in a plane perpendicular to the thickness direction of the phase modulation layer, the center of gravity of the plurality of different refractive index regions passes through the lattice points of the virtual square lattice and the square lattice. Arranged on a first straight line that is inclined with respect to the light image, the distance between the center of gravity of each different refractive index region and the corresponding lattice point is individually set according to the phase defined based on the optical image. Lattice,
When the first region and the second region that divide the phase modulation layer into two are set, the direction of movement of the center of gravity corresponding to the phase of each different refractive index region included in the second region is the first. A light emitting device that is opposite to the direction of movement of the center of gravity corresponding to the phase of each different refractive index region included in one region. The light emitting device according to claim 1 or 2, wherein the boundary line separating the first region and the second region passes through the center of the phase modulation layer. The light emitting device according to claim 3, wherein the boundary line is a second straight line. The angle of inclination of the first straight line with respect to the square grid is greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °.
The light emitting device according to claim 4, wherein the inclination angle of the second straight line with respect to the square lattice is greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °. The light emitting device according to claim 5, wherein the inclination angle of the second straight line with respect to the square lattice is 135 ° or 315 °. The angle of inclination of the first straight line with respect to the square grid is greater than 90 ° and less than 180 °, or greater than 270 ° and less than 360 °.
The light emitting device according to claim 4, wherein the inclination angle of the second straight line with respect to the square lattice is greater than 0 ° and less than 90 °, or greater than 180 ° and less than 270 °. The light emitting device according to claim 7, wherein the inclination angle of the second straight line with respect to the square lattice is 45 ° or 225 °. The light emitting device according to any one of claims 1 to 8, wherein the inclination angle of the first straight line with respect to the square lattice is constant. The light emitting device according to claim 9, wherein the inclination angle of the first straight line with respect to the square lattice is 45 °, 135 °, 225 ° or 315 °. The light emitting device according to any one of claims 1 to 10, wherein the product κL of the optical coupling coefficient κ and the resonator length L is smaller than 10. The light emitting device according to any one of claims 1 to 11, wherein the light emitting unit is an active layer provided on the substrate.

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