JP7741374B2 - laser device - Google Patents

Description

This disclosure relates to a laser device.

Technology has been developed that uses a diffraction grating to combine multiple laser beams with different wavelengths emitted from semiconductor laser elements into a single beam. This technology is known as wavelength beam combining (WBC). Patent Document 1 describes a laser system in which multiple beams emitted from a semiconductor laser element are focused onto a diffraction grating using a combining lens, and then coaxially superimposed to form a single beam.

Special table 2017-539083 publication

The laser system described in Patent Document 1 has a configuration in which multiple beams are focused onto a diffraction grating using a combining lens. Because this configuration uses a combining lens, there is a risk of aberration occurring.

In an exemplary embodiment, the laser device of the present disclosure comprises: a first mirror and a second mirror forming a resonator; a semiconductor laser element disposed between the first mirror and the second mirror and including multiple laser oscillation regions that oscillate at different wavelengths during operation, wherein the multiple laser oscillation regions have a waveguide section that propagates the laser light emitted from each laser oscillation region so that the axes of propagation of the laser light approach each other; a collimator disposed between the semiconductor laser element and the second mirror and converting the laser light emitted from the multiple laser oscillation regions into multiple collimated beams; and a diffraction grating disposed between the collimator and the second mirror at a position where the multiple collimated beams intersect, the diffraction grating diffracting the multiple collimated beams at different angles depending on their wavelengths to form a wavelength-combined beam and emitting the wavelength-combined beam in a first direction. At least a portion of the second mirror is a flat mirror that reflects the wavelength-combined beam emitted from the diffraction grating in a second direction opposite to the first direction, returning the wavelength-combined beam to the diffraction grating.

Embodiments of the present disclosure make it possible to suppress the occurrence of aberrations.

FIG. 1 is a plan view schematically illustrating an example of the configuration of a laser device according to an embodiment of the present disclosure. FIG. 2 is a plan view schematically showing a waveguide portion of a typical semiconductor laser device. FIG. 3 is a plan view schematically illustrating an example of a waveguide portion of a semiconductor laser element included in a laser device according to an embodiment of the present disclosure. FIG. 4 is a cross-sectional view of the semiconductor laser device taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view of the semiconductor laser device taken along line VV in FIG. FIG. 6 is a diagram schematically showing diffraction by a diffraction grating. FIG. 7 is a diagram showing a gain curve in the laser oscillation region and a schematic diagram showing the spectrum of the laser light when oscillating in a single longitudinal mode. FIG. 8 is a plan view schematically illustrating another configuration example of a laser device according to an embodiment of the present disclosure. FIG. 9 is a plan view schematically illustrating another example of a waveguide portion of a semiconductor laser element included in a laser device according to an embodiment of the present disclosure. FIG. 10 is a plan view schematically illustrating yet another example of a waveguide portion of a semiconductor laser element included in a laser device according to an embodiment of the present disclosure. FIG. 11 is a plan view schematically illustrating yet another example of a waveguide portion of a semiconductor laser element included in a laser device according to an embodiment of the present disclosure.

The laser device according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. Parts that appear in multiple drawings with the same reference numerals indicate the same or equivalent parts. The descriptions of the dimensions, materials, shapes, and relative positions of components are intended to be illustrative and not to limit the scope of the present invention. The sizes and positional relationships of components shown in each drawing may be exaggerated to facilitate understanding.

First Embodiment
An embodiment of a laser device according to the present disclosure will be described with reference to the drawings, in which mutually orthogonal X-, Y-, and Z-axes are shown for reference.

First, refer to FIG. 1. The laser device 100 in this embodiment includes a first mirror M1 and a second mirror M2 that form a resonator, and a semiconductor laser element 10 disposed between the first mirror M1 and the second mirror M2. The semiconductor laser element 10 includes multiple laser oscillation regions 10X that oscillate at different wavelengths during operation. In the illustrated example, the semiconductor laser element 10 is a laser bar having four laser oscillation regions 10X. During operation, the four laser oscillation regions 10X oscillate at wavelengths λ1, λ2, λ3, and λ4, respectively, and emit laser light having wavelengths λ1, λ2, λ3, and λ4. The number of laser oscillation regions 10X included in one laser bar is not limited to four and may be three, five or more, for example, ten or more. The semiconductor laser element 10 may have multiple ridges and/or multiple stripe electrodes that define the multiple laser oscillation regions 10X.

Figure 2 is a plan view schematically showing the shape of the laser oscillation region 10X of a typical semiconductor laser element 10Q. The propagation axes of the laser light L emitted from the laser oscillation region 10X are parallel to each other. In other words, in the semiconductor laser element 10Q, each waveguide portion that propagates the laser light extends linearly along the Z-axis direction.

In contrast, in the laser device 100 of this embodiment, as shown in FIG. 1, the multiple laser oscillation regions 10X have waveguide sections that propagate the laser light so that the propagation axes of the laser light L emitted from each laser oscillation region 10X approach each other and intersect. This point will be explained in detail below.

Figure 3 is a plan view schematically showing the waveguide portion 18 of the semiconductor laser element 10 included in the laser device 100 of this embodiment. The cross-sectional configuration of the semiconductor laser element 10 will be described later. The laser bar constituting the semiconductor laser element 10 has a light-emitting surface 10F where one ends of the multiple laser oscillation regions 10X are aligned, and a light-reflecting surface 10R where the other ends of the multiple laser oscillation regions 10X are aligned. As shown in Figure 1, the light-reflecting surface 10R is provided with a reflective film that forms the first mirror M1. Furthermore, the light-emitting surface 10F is provided with an anti-reflection film. An example of such a reflective film and anti-reflection film is a dielectric multilayer film. The resonator formed by the first mirror M1 and the second mirror M2 is called an "external resonator."

In the example of Figure 3, the waveguide section 18 includes a first portion 18a that extends linearly along the Z-axis direction and a second portion 18b that curves with a curvature greater than zero. In the example of Figure 3, the first portion 18a is located to the left of line O-O (dotted line), and the second portion 18b is located to the right of line O-O. In this example, line O-O is a straight line parallel to the X-axis. However, the boundary between the first portion 18a and the second portion 18b does not need to be located at the same position in the Z-axis direction. In other words, the length of the first portion 18a in the Z-axis direction may vary for each waveguide section 18. Note that the entire second portion 18b does not need to have a curvature, and the second portion 18b may include a linear portion. The important point is that the second portion 18b is inclined (not perpendicular) to the light emission surface 10F so that the propagation direction of the laser light emitted from the end of the second portion 18b forms a predetermined angle with the Z-axis. The size of this "predetermined angle" will be explained later.

Next, an example configuration of the semiconductor laser element 10 will be described with reference to Figures 4 and 5. Figure 4 is a cross-sectional view of the semiconductor laser element 10 taken along line IV-IV in Figure 3, and Figure 5 is a cross-sectional view of the semiconductor laser element 10 taken along line V-V in Figure 3.

The illustrated semiconductor laser device 10 comprises a first conductivity type semiconductor substrate 11a, a first conductivity type semiconductor layer 11b, an active layer 11c, and a second conductivity type semiconductor layer 11d. Here, "first conductivity type" refers to one of p-type and n-type, and "second conductivity type" refers to the other of p-type and n-type. Each of the first conductivity type semiconductor layer 11b and the second conductivity type semiconductor layer 11d may have a multilayer structure including multiple layers such as cladding layers and guide layers. Furthermore, the active layer 11c may have a single quantum well structure or a multiple quantum well structure.

A ridge 13 is provided on the top of the second conductivity type semiconductor layer 11d. A second conductivity side electrode (stripe electrode) 15 is formed on the upper surface of each ridge 13. A first conductivity side electrode 14 is provided on the lower surface of the first conductivity type semiconductor substrate 11a. Adjacent second conductivity side electrodes 15 are electrically isolated from each other by an insulating layer 17 formed on the second conductivity type semiconductor layer 11d. A pad electrode 16 is provided on the second conductivity side electrode 15.

The second conductivity type semiconductor layer 11d may include a contact layer in the ridge 13 at a portion that contacts the second conductivity side electrode 15. The ridge 13 determines the shape and size of the waveguide portion 18 in FIG. 3. Therefore, the planar layout of the first portion 18a and second portion 18b of the waveguide portion 18 in FIG. 3 is determined by the planar layout of the ridge 13. The planar layout of the ridge 13 can be determined to the desired shape by the shape of the etching mask used in the step of etching the upper portion of the second conductivity type semiconductor layer 11d (e.g., the upper portion of the cladding layer).

The first conductive side electrode 14 and the second conductive side electrode 15 are each connected to a drive circuit. When a predetermined voltage is applied between the first conductive side electrode 14 and the second conductive side electrode 15 by the drive circuit, a current flows in the Y-axis direction within each ridge 13. When the current flowing through the laser oscillation region 10X of the active layer 11c exceeds a threshold value, a charge population inversion is formed in the laser oscillation region 10X, making it possible to amplify light within a predetermined wavelength range and generate laser oscillation. The width of each laser oscillation region 10X is determined by the width of the ridge 13 or stripe electrode 15. Each laser oscillation region 10X is the portion of the semiconductor laser element 10 that forms the optical path until light is emitted, and includes a waveguide portion.

In the example shown in Figure 3, the linearly extending first portion 18a of the waveguide 18 is perpendicular to the light-reflecting surface 10R in a planar view. Therefore, laser light incident on the light-reflecting surface 10R from the linearly extending first portion 18a is specularly reflected back into the linearly extending first portion 18a. This reduces reflection loss compared to when the first portion 18a is inclined relative to the light-reflecting surface 10R. According to the configuration example shown in Figure 3, the parallel second portions 18b of the waveguide 18 curve in a predetermined direction, and the first portions 18a are perpendicular to the light-reflecting surface 10R. This allows the propagation axes of the laser light L emitted from the multiple laser oscillation regions 10X to approach each other and intersect, thereby suppressing an increase in reflection loss due to the light-reflecting surface 10R. Furthermore, since the propagation axes of the laser light L are brought closer to each other and intersect, a focusing lens is not required. When multiple laser beams are incident on a single focusing lens, aberration may occur due to the laser beams that enter the center of the focusing lens and the laser beams that enter the peripheral portion. By not using a focusing lens, the number of parts can be reduced while suppressing the occurrence of aberration.

At the light emitting surface 10F, not only is laser light L emitted from the semiconductor laser element 10, but laser light reflected by the second mirror M2 (described below) returns to the semiconductor laser element 10. As shown in FIG. 3, in a plan view, the second portion 18b of the waveguide portion 18 is inclined with respect to the light emitting surface 10F. When the laser light L passes through the light emitting surface 10F, refraction occurs. The angle between the second portion 18b of the waveguide portion 18 and the light emitting surface 10F can be determined taking into account the effect of this refraction.

As described above, the planar layout of the waveguide section 18 is determined by the planar layout of the ridges 13 and the second conductive side electrodes (stripe electrodes) 15. Therefore, in this embodiment, the multiple ridges 13 and/or multiple stripe electrodes 15 each have portions that form different angles with respect to the light emitting surface 10F in a planar view, and also have portions that extend in a direction perpendicular to the light reflecting surface 10R.

The semiconductor laser element 10 may be, for example, a semiconductor laser element that emits blue light, a semiconductor laser element that emits green light, or a semiconductor laser element that emits red light. Semiconductor laser elements that emit light other than blue, green, or red, such as ultraviolet or infrared, may also be used. In this specification, blue light is light with a peak emission wavelength in the range of 420 nm to 494 nm. Green light is light with a peak emission wavelength in the range of 495 nm to 570 nm. Red light is light with a peak emission wavelength in the range of 605 nm to 750 nm. Examples of semiconductor laser elements that emit blue or green light include nitride semiconductors. Examples of nitride semiconductors that can be used include GaN, InGaN, and AlGaN. Examples of semiconductor laser elements that emit red light include InAlGaP-based, GaInP-based, GaAs-based, and AlGaAs-based semiconductors. When using the laser device 100 to process metal materials, for example, it is desirable to use a semiconductor laser element 10 that oscillates at a wavelength that is highly absorbed by the metal material to be processed.

Refer to Figure 1 again.

In this embodiment, the laser device 100 includes a collimator 20 disposed between the semiconductor laser element 10 and the second mirror M2. The collimator 20 is configured to convert the laser light L emitted from the multiple laser oscillation regions 10X into multiple collimated beams 12. The propagation axes of the multiple collimated beams 12 approach each other and intersect. The collimator 20 is a collection of collimator lenses. The collimator 20 may be a lens array formed from a single plastic material with a number of lenses equal to the number of laser oscillation regions 10X, or an optical component assembly with multiple lenses arranged in an array. In one embodiment, the collimator 20 may include multiple collimating lenses, each with an optical axis parallel to the propagation axis of the corresponding laser light L. Because the collimator 20 is a collection of collimator lenses, the multiple laser light beams L emitted from the semiconductor laser element 10 are incident on different collimator lenses. This allows the distance between the semiconductor laser element 10 and the collimator 20 to be shorter than when multiple laser light beams L are incident on a single lens. Furthermore, since multiple laser beams L can be incident on the centers of different collimator lenses, distortion of the laser waveform can be suppressed.

In FIG. 1 , the laser light L and collimated beam 12 emitted from the semiconductor laser element 10 are shown as simple straight lines. The actual laser light L and collimated beam 12 are light beams having an intensity distribution in a plane perpendicular to the propagation direction of the light beam. This intensity distribution can be approximated by a distribution function, such as a Gaussian distribution, in the plane perpendicular to the propagation direction of the light beam. In this disclosure, the diameter of the beam is referred to as the "beam diameter." The beam diameter is defined as the size of a region having an optical intensity equal to or greater than 1/ ^e2 relative to the optical intensity at the beam center. Here, "e" is Napier's constant. The intensity distribution of the light beam does not necessarily need to be axially symmetric. When light emitted from the semiconductor laser element 10 propagates in the Z-axis direction, it diverges in the Y-axis and X-axis directions. In this example, the angle of divergence in the Y-axis direction is larger than the angle of divergence in the X-axis direction. Therefore, the Y-axis direction and the X-axis direction of the semiconductor laser element 10 can be called the "fast axis" and "slow axis," respectively. The laser light L emitted from the semiconductor laser element 10 has an elliptical intensity distribution (near-field pattern) with its major axis in the X-axis (slow-axis) direction immediately after emission, but as it travels in the Z-axis direction, it acquires an elliptical intensity distribution (far-field pattern) with its major axis in the Y-axis (fast-axis) direction. The collimator 20 acts to reduce the divergence angles of such laser light L in the fast-axis direction and the slow-axis direction. In this case, the collimator 20 may be a combination of, for example, four cylindrical lenses (fast-axis collimating lenses) whose generatrix directions (directions of zero curvature) of the lens surfaces are parallel to a direction perpendicular to the traveling direction of the laser light L in the XZ plane, and four cylindrical lenses (slow-axis collimating lenses) whose generatrix directions of the lens surfaces are parallel to the Y-axis direction.

The collimated beam, which has a smaller divergence angle after passing through the collimator 20, is not strictly parallel light, but is approximated as a Gaussian beam, in which the product of the divergence angle and the beam diameter is a finite value. In the drawings, the central axes of such light beams are represented by straight lines to schematically show the direction of travel of these light beams. These straight lines can be thought of as representing the rays of light passing through the center of each light beam.

The beam diameter of each collimated beam 12 is equal to or less than the center-to-center distance between the multiple laser oscillation regions 10X. The width of each laser oscillation region 10X may be, for example, 1 μm or more and 200 μm or less. This width may be 20 to 80% of the center-to-center distance between adjacent laser oscillation regions 10X.

The laser device 100 shown in FIG. 1 includes a diffraction grating G positioned at a predetermined angle between the collimator 20 and the second mirror M2 at a position where the propagation axes of the laser light L emitted from the multiple laser oscillation regions 10X intersect. The multiple collimated beams 12 emitted from the collimator 20 are each incident on the same region 64 of the diffraction grating G at different angles. The diffraction grating G diffracts the multiple collimated beams 12 at the region 64. The multiple collimated beams 12 diffracted by the diffraction grating G are combined to form a wavelength-combined beam 40, which is emitted in the first direction 50.

In this embodiment, the direction in which the diffraction grooves of the diffraction grating G extend is parallel to the Y-axis direction.

The structure and function of the diffraction grating G will be explained below with reference to Figure 6.

Figure 6 is a schematic diagram showing how multiple collimated beams 12 enter the same region of the diffraction grating G and are diffracted there. In this example, the collimated beams 12 entering region 64 are diffracted by the diffraction grating G and coaxially superimposed to form the wavelength-combined beam 40.

The angles of incidence α of the four collimated beams 12 incident on the diffraction grating G are α1, α2, α3, and α4, respectively. The angle of incidence α is the angle formed by the central axis of the collimated beam 12 with respect to the normal direction 66 of the diffraction grating G.

When the diffraction angle of the transmitted diffracted light formed when the collimated beam 12 is incident on the diffraction grating G is β, the relationship of the following equation 1 holds.
sin α + sin β = N・m・λ (Formula 1)
Here, N is the number of grooves per unit length of the diffraction grating G, m is the diffraction order, and λ is the wavelength of light.

If the diffraction order m is 1, for example, when N = 2220, the wavelength λ is 410.0 nm, and the incident angle α is 45.0 degrees, the diffraction angle β is equal to 11.77 degrees. In Example 6, of the four collimated beams 12, the collimated beam 12 with wavelength λ = λ4 = 410.0 nm is incident on region 64 of diffraction grating G at an incident angle α = α4 = 45.00 degrees, diffracted, and emitted in first direction 50. In this example, the collimated beams 12 incident on diffraction grating G at incident angles α1, α2, and α3 all form coaxial first-order diffracted light along first direction 50 when their respective diffraction angles β are equal to 11.77 degrees. The magnitudes of the incident angles α1, α2, and α3 are determined depending on the configuration of the waveguide section 18 in the semiconductor laser device 10 and the orientation of the diffraction grating G. The wavelength λ is then determined by the incident angle α. For example, if α1 = 46.26 degrees, α2 = 45.84 degrees, and α3 = 45.42 degrees, then the relationship in Equation 1 is satisfied when λ1 = 416.92 nm, λ2 = 414.63 nm, and λ3 = 412.32 nm. In this way, once the incident angles α1, α2, α3, and α4 and the diffraction angle β are determined, the wavelengths λ1, λ2, λ3, and λ4 can be determined from Equation 1. Table 1 shows some examples of wavelengths λ, incident angles α, and diffraction angles β that satisfy the relationship in Equation 1.

The multiple laser oscillation regions 10X of the semiconductor laser element 10 are capable of laser oscillation within a predetermined wavelength range that includes, for example, the wavelength λ shown in Table 1. According to the laser device 100 of this embodiment, collimated beams 12 having wavelengths λ that satisfy the relationship in Equation 1 are selectively superimposed coaxially to form a wavelength-combined beam 40. This wavelength-combined beam 40 is partially reflected by the second mirror M2 and fed back to the laser oscillation region 10X, as described below. As a result, each laser oscillation region 10X can selectively and sharply oscillate at specific wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1 within the wavelength range in which laser oscillation is possible.

Figure 7 is a diagram schematically showing the gain curve of a laser oscillation region 10X and the spectrum of laser light oscillating in a single longitudinal mode at wavelength λ that satisfies Equation 1. Multiple laser oscillation regions 10X in a single semiconductor laser element 10 may have the same gain curve. However, as shown in Table 1, the magnitudes of the wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1 vary depending on the incident angles α1, α2, α3, and α4. Therefore, in each laser oscillation region 10X, light of different wavelengths λ1, λ2, λ3, and λ4 is selectively amplified and emitted as laser light. In the example shown in Table 1, the wavelengths λ1, λ2, λ3, and λ4 are in the range from 410.00 nm to 413.92 nm. Therefore, each laser oscillation region 10X of the semiconductor laser element 10 is required to have gain characteristics that enable oscillation over a wider range than this range.

In the above explanation, it was stated that the angles of incidence α1, α2, α3, and α4 of the collimated beam 12 incident on region 64 of the diffraction grating G are determined by the configuration of the waveguide section 18 in the semiconductor laser element 10 and the orientation of the diffraction grating G. However, before laser oscillation occurs, light having a broad wavelength range can be emitted from the semiconductor laser element 10, as shown by the gain curve in Figure 7. As a result, the diffraction angle β of a light beam incident on a specific region 64 of the diffraction grating G can have a finite width. However, because the second mirror M2 specularly reflects the collimated beam diffracted coaxially, light having the wavelength of the light diffracted in a predetermined direction is returned to each laser oscillation region 10X, enabling oscillation at that wavelength.

At least a portion of the second mirror M2 is a plane mirror 70. The plane mirror 70 is configured to reflect the wavelength-combined beam 40 emitted from the diffraction grating G in a second direction 52 opposite to the first direction 50, returning the beam to the diffraction grating G. The second mirror M2 is also a partially reflective mirror that transmits a portion of the wavelength-combined beam 40. The wavelength-combined beam 40 that has transmitted through the second mirror M2 is extracted from the laser device 100 and used.

Each laser oscillation region 10X receives a light beam of a predetermined wavelength contained in multiple light beams (diffracted beams) formed when the wavelength-combined beam 40 reflected by the second mirror M2 is diffracted by the diffraction grating G. Each of the multiple laser oscillation regions 10X oscillates at the peak wavelength of the incident light beam.

In the above embodiment, the diffraction grating G is a transmissive diffraction grating, but the diffraction grating G may also be a reflective diffraction grating. Figure 8 is a schematic diagram showing a modified example in which the diffraction grating G in the laser device 100 shown in Figure 1 is replaced with a reflective diffraction grating.

In the illustrated example, diffraction is described as occurring on the light-incident surface of the diffraction grating G. However, diffraction may also occur on the back surface of the diffraction grating G, which is located opposite the light-incident surface, or may occur within the diffraction grating.

Next, with reference to Figures 9 to 11, other configuration examples of the waveguide section 18 provided in the semiconductor laser element 10 of this embodiment will be described.

In the example of Figure 3 described above, the second portions 18b of all waveguide portions 18 are curved in a planar view, but the configuration of the waveguide portions 18 is not limited to this example. Some waveguide portions 18 may have second portions 18b that extend linearly. For example, in the example shown in Figure 9, of the odd number of waveguide portions 18, the central waveguide portion 18 has both the first portion 18a and the second portion 18b that extend linearly. This configuration also allows the propagation axes of the laser light L emitted from each laser oscillation region 10X to approach each other and intersect.

The position of the linearly extending waveguide portion 18 is not limited to the center of the semiconductor laser element 10. In the example of Figure 10, the waveguide portion 18 located at the bottom in Figure 10 extends linearly. Note that in the examples of Figures 3 and 9, in a plan view, multiple waveguide portions 18 are arranged symmetrically with respect to a line that passes through the center of the semiconductor laser element 10 and extends parallel to the Z-axis direction. However, as shown in Figure 10, multiple waveguide portions 18 do not need to be arranged symmetrically. Furthermore, as shown in Figure 11, the second portions 18b of all waveguide portions 18 may be inclined toward the negative side of the X-axis with respect to the Z-axis direction. Conversely, the second portions 18b of all waveguide portions 18 may be inclined toward the positive side of the X-axis with respect to the Z-axis direction. It is also possible to use a combination of a first semiconductor laser element 10 in which the second portions 18b of all waveguide portions 18 are inclined toward the negative X-axis with respect to the Z-axis direction, and a second semiconductor laser element 10 in which the second portions 18b of all waveguide portions 18 are inclined toward the negative X-axis with respect to the Z-axis direction.

In the laser device according to each of the above embodiments, the waveguide of a semiconductor laser element having multiple laser oscillation regions propagates the laser light emitted from each laser oscillation region so that the propagation axes of the laser light approach each other and intersect. Because a diffraction grating is placed at the position where the propagation axes of the laser light intersect, a wavelength-combined beam can be formed using a single diffraction grating, eliminating the need for a focusing lens or the like, and reducing the number of parts while suppressing the occurrence of aberrations. Reducing the number of parts also makes it possible to suppress power reduction due to optical loss. Furthermore, because the center-to-center distance of the ridges can be made wider than the distance between the laser light emission points, the heat-generating laser oscillation regions can be sparsely arranged, enabling improved heat dissipation performance. Furthermore, because a wavelength-combined beam is obtained in which laser beams with different wavelengths are superimposed on the same axis, it is possible to achieve a high optical intensity that cannot be achieved with a single-wavelength laser beam.

The laser device disclosed herein can be used in industrial fields requiring high-power laser light sources, such as cutting various materials, drilling holes, localized heat treatment, surface treatment, metal welding, and 3D printing.

The laser device disclosed herein can be used as an excitation light source for a fiber laser device, or as a laser light source for a direct diode laser device that processes materials by directly irradiating them.

10: Semiconductor laser element, 10F: Light emission surface of semiconductor laser element, 10R: Light reflection surface of semiconductor laser element, 10X: Laser oscillation region, 12: Collimated beam, 20: Collimator, 40: Wavelength combined beam, 50: First direction, 52: Second direction, 70: Plane mirror, 100: Laser device, G: Diffraction grating, M1: First mirror, M2: Second mirror

Claims (8)

a first mirror and a second mirror forming a resonator;
a semiconductor laser element disposed between the first mirror and the second mirror, the semiconductor laser element including a plurality of laser oscillation regions that oscillate at different wavelengths during operation, the plurality of laser oscillation regions having waveguide portions that propagate the laser light so that the axes of travel of the laser light emitted from the respective laser oscillation regions approach each other;
a collimator disposed between the semiconductor laser element and the second mirror, the collimator converting the laser beams emitted from the plurality of laser oscillation regions into a plurality of collimated beams;
a diffraction grating disposed at a position where the plurality of collimated beams intersect between the collimator and the second mirror, the diffraction grating diffracting the plurality of collimated beams at different angles depending on their wavelengths to form a wavelength-combined beam, and emitting the wavelength-combined beam in a first direction;
Equipped with
At least a portion of the second mirror is a flat mirror, and reflects the wavelength-combined beam output from the diffraction grating in a second direction opposite to the first direction, and returns the beam to the diffraction grating;
The semiconductor laser element is
the plurality of laser oscillation regions;
a light emitting surface on which one ends of the plurality of laser oscillation regions are aligned;
a light reflecting surface on which the other ends of the plurality of laser oscillation regions are aligned;
a plurality of ridge and/or stripe electrodes defining the waveguide portion;
It has
the plurality of ridge and/or stripe electrodes have portions that form different angles with respect to the light emitting surface in a plan view, and
A laser device, wherein the plurality of ridge and/or stripe electrodes are arranged asymmetrically with respect to a line that passes through the center of the semiconductor laser element and extends in a direction perpendicular to the light emitting surface. The laser device according to claim 1 , wherein the portion forming a different angle with respect to the light emitting surface is inclined toward one of both ends of the light emitting surface in the plan view. one of the plurality of ridge and/or plurality of stripe electrodes defines a waveguide portion extending linearly;
2. The laser device according to claim 1, wherein, in the planar view, a position of the linearly extending waveguide portion is shifted from a straight line that passes through a center of the semiconductor laser element and extends in a direction perpendicular to the light emitting surface to one of both ends of the light emitting surface. 4. The laser device according to claim 3, wherein, in the planar view, the position of the linearly extending waveguide portion is determined by a ridge or stripe electrode, among the plurality of ridge and/or stripe electrodes, that is closest to one of both ends of the light emitting surface. the semiconductor laser element is a laser bar having the plurality of laser oscillation regions ,
The laser device according to claim 1 , wherein the light reflecting surface is provided with a reflective film that forms the first mirror, and the light emitting surface is provided with an anti-reflection film. The laser device according to claim 1 , wherein the plurality of ridge and/or stripe electrodes have portions that extend in a direction perpendicular to the light emitting surface in the plan view. each of the plurality of laser oscillation regions receives a light beam of a predetermined wavelength included in a plurality of light beams formed by the wavelength-combined beam reflected by the second mirror being diffracted by the diffraction grating;
The laser device according to claim 1 , wherein each of the plurality of laser oscillation regions oscillates at a peak wavelength of the incident light beam. 8. The laser device according to claim 1 , wherein the collimator includes a plurality of collimating lenses each having an optical axis parallel to the propagation axis of the corresponding laser beam.