JP2757615B2 - Semiconductor optical second harmonic light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to an optical second harmonic light emitting device.

[0002]

2. Description of the Related Art It is difficult to obtain blue light emission from a semiconductor, and blue light emission by generation of second harmonic light has been attempted. Using a semiconductor as a nonlinear material is highly compatible with using a semiconductor laser as an excitation light source (Journal of Crystal Grouse [Journal
of Crystal Growth] Vol. 101, No. 55
0, 1990).

[0003]

However, it is very difficult to form a semiconductor laser and a non-linear element on the same substrate in a plane, and it has not been put to practical use.

[0004]

In order to solve the above-mentioned problems, the present invention provides a light emitting device having the following structure.

(1) It has a horizontal semiconductor laser structure in which the angular frequency of oscillation light formed on a semiconductor substrate is ω,
A second harmonic of a semiconductor material having a first inclined reflection surface on one end surface of the laser structure and having a second-order nonlinear optical characteristic laminated on the semiconductor laser structure and transmitting light at an angular frequency of 2ω. A wave-generating region, a second inclined-type reflecting surface in the optical second-harmonic-generating region on the first inclined-type reflecting surface, and a waveguide structure or a grating structure in the optical-second-harmonic-generating region. And phase-matched to the light having the angular frequencies ω and 2ω, and the light having the angular frequency ω emitted from the laser structure is transmitted through the first inclined reflecting surface and the second inclined reflecting surface. The light is guided to the 2nd harmonic generation region, converted into light having an angular frequency of 2ω, and is converted to an angular frequency of 2ω
A light emitting device characterized by emitting light of the following.

(2) It has a horizontal semiconductor laser structure in which the angular frequency of oscillation light formed on the semiconductor substrate is ω,
A second harmonic of a semiconductor material having a first inclined reflection surface on one end surface of the laser structure and having a second-order nonlinear optical characteristic laminated on the semiconductor laser structure and transmitting light at an angular frequency of 2ω. The second harmonic generation region has a multilayer structure made of at least two kinds of semiconductor materials, is phase-matched with respect to angular frequency ω and 2ω light, and is radiated from the laser structure. The light having the angular frequency ω is guided to the optical second harmonic generation region by the first inclined reflection surface, converted into light having the angular frequency 2ω, and the light having the angular frequency 2ω is emitted in the vertical direction. A light emitting element.

(3) In the above device, a 2ω light reflection film made of a semiconductor multilayer film satisfying the Bragg reflection condition for light having an angular frequency of 2ω is provided between the semiconductor laser structure and the optical second harmonic generation region. The light emitting device according to the above (1) or (2), wherein

(4) A ω-light reflecting film having a multilayer structure of at least two types of semiconductor layers that satisfies the Bragg reflection condition for the angular frequency ω light is provided above the optical second harmonic generation region. The light emitting device according to the above (2).

[0009]

The light emitting device according to the present invention employs a structure in which light emitted by the semiconductor laser is reflected by the inclined reflecting surface and guided to the second harmonic generation region. With this structure, the optical second harmonic generation region can be continuously crystal-grown after the semiconductor laser layer is grown. In addition, since a semiconductor material is used as the optical second harmonic generation region, a high-quality multilayer film and a waveguide can be obtained by matching the lattice constant of the material.

In order to obtain an optical second harmonic, a phase matching condition must be satisfied. The condition can be easily achieved by using a dispersion relation by a waveguide structure and introducing periodicity by a multilayer structure or a grating structure. I can be satisfied.

The phase matching condition based on the periodic structure is such that the length of one cycle is d, and the angular frequencies ω and 2ω in the second harmonic generation region.
Assuming that the wave numbers of the light in the substance are k ₁ and k ₂ , it suffices to satisfy n · 2π / d = k ₂ −k ₁ (n = ± 1,...).

Since the 2ω light reflecting film according to the third aspect satisfies the Bragg reflection condition for the light having an angular frequency of 2ω, of the 2ω light generated in the optical second harmonic generation region, it travels toward the substrate. The light is reflected by the 2ω light reflection film, and is extracted from the upper surface of the substrate to the outside as output light. Since the 2ω light reflection film has a transmission characteristic with respect to the angular frequency ω light, light having an angular frequency ω generated in the semiconductor laser region passes through the 2ω light reflection film,
The light effectively reaches the optical second harmonic generation region. By adding the 2ω light reflection film, the conversion efficiency to 2ω increases.

The ω reflection film according to claim (4) has an angular frequency ω
In order to satisfy the Bragg reflection condition with respect to light, light having an angular frequency ω traveling upward in the optical second harmonic generation region is reflected.
For this reason, the intensity of the angular frequency ω light in the optical second harmonic generation region increases, and the conversion efficiency to the optical second harmonic increases.
The refractive index of the semiconductor layer changes depending on the frequency, and the Bragg reflection conditions for the light having the angular frequencies ω and 2ω are different.
The ω reflection film transmits light having an angular frequency of 2ω. By adding the ω reflection film, the optical second harmonic can be efficiently extracted.

[0014]

(Embodiment 1) Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention.

On a semiconductor substrate 1 made of p-type GaAs,
A p-type cladding layer 2 of Al _0.4 Ga _0.6 As (1 μm thick), an active layer 3 of GaAs (0.1 μm thickness), an n-type cladding of n-type Al _0.4 Ga _0.6 As (1 μm thick) After forming the layer 4 by a molecular beam epitaxy method, a grating 5 having a period of 1.05 μm was formed by an interference exposure method. Again by molecular beam epitaxy,
n-type ZnS _0.2 Se _{0. 8} layers (thickness 0.2 [mu] m) 6, n-type ZnSe layer was formed (thickness 1 [mu] m) 7. Subsequently, after the n-electrode 8 and the p-electrode 9 were formed by vapor deposition, the first inclined reflection surface (at an angle of 45 degrees) 10 and the second inclined reflection surface (at an angle of 45 degrees) 11 were formed by dry etching.
The semiconductor laser structure 12 includes a p-type cladding layer 2, an active layer 3,
The optical second harmonic generation region 13 includes an n-type ZnS _0.2 Se _0.8 layer 6 and an n-type Zn
It is composed of the Se layer 7.

When current is injected from the electrodes 8 and 9 and the wavelength in vacuum of the light of the angular frequency ω radiated from the semiconductor laser structure 12 is λ ₁ , λ ₁ = 860 nm. The light having a wavelength of 860 nm is reflected by the first inclined reflecting surface 10 and the second inclined reflecting surface 11, travels through the optical second harmonic generation region 13, and has an angular frequency of 2ω and a wavelength of λ ₂ = 430.
nm light is generated.

The angular frequency ω and phase matching conditions for 2ω light may the period of the grating d, is satisfied 2π / d = k ₂ -2k ₁ wavenumbers as k ₁ and k _2, respectively, d = 1 in ZnSe. The thickness may be set to 05 μm.

Since the optical second harmonic generation region 13 is a part of the laser oscillation resonator for the light having the angular frequency ω, the electric field intensity is strong and the wavelength is converted under the favorable condition that the wavelength conversion efficiency is 5%. 430 nm blue light was obtained.

ZnSe has almost the same lattice as GaAs.
Good crystals are easily obtained. Also, since the SHG structure is made by crystal growth, the handling of the device is easy and mass production is possible.

In the above-described embodiment, a grating structure is used as a method for achieving phase matching. However, the present invention is not limited to this, and a waveguide structure may be used.

(Embodiment 2) FIG. 2 is a sectional view showing an embodiment in which the invention of claim 3 is applied to the invention of claim 2.

On the semiconductor laser structure 14, a 2ω reflection film 15 composed of 10 periods of layers of ZnSe and ZnS _0.2 Se each having a thickness of 36 nm, ZnSe (0.525 μm thick)
After forming the optical second harmonic generation region 16 consisting of 10 periods of ZnS _0.1 Se _0.9 (thickness 0.525 μm) by molecular beam epitaxy, the first inclined reflection surface (45 degrees) 17 is formed by dry etching. did.

Light having an angular frequency ω and a vacuum wavelength λ ₁ = 860 nm emitted in the region of the semiconductor laser structure 14 is reflected by the first inclined reflecting surface 17. 2ω reflection film 15 has a wavelength of 860 n
The transmittance of the light of m is high, and the light enters the light second harmonic generation region 16.

The optical second harmonic generation region 16 has a periodic structure, and satisfies the phase matching condition. For this reason, light having an angular frequency ω and a wavelength of 860 nm is converted to an angular frequency 2ω.
Was emitted in the vertical direction. Z
The nonlinear coefficient of nSSe was large, and 430 nm light of 2 mW was obtained. Since the 2ω reflection film 15 reflects light of 430 nm, all the converted light was emitted from the upper side, and the efficiency was increased.

The 2ω reflection film 15 is for improving the efficiency, and the optical second harmonic can be obtained without this structure.

In the first and second embodiments, the nonlinear material is Zn.
Although the SSe layer is used, the invention is not limited thereto, and a ZnSSe strained superlattice or another semiconductor material may be used.

In the above embodiments, a semiconductor laser having a DH structure is used. However, the present invention is not limited to this, and a quantum well structure laser may be used.

(Embodiment 3) FIG. 3 is a sectional view of an embodiment of the fourth aspect of the present invention.

On the semiconductor laser structure 18, ZnSe (thickness 0.525 μm) and ZnS _0.1 Se _0.9 (thickness 0.5)
25 μm) Optical second harmonic generation region 1 consisting of 10 periods
9, ZnSe (84 nm thick) and ZnS _0.1 Se _0.9
After forming the ω reflection film 20 having 10 periods (thickness: 84 nm) by molecular beam epitaxy, the first inclined reflection surface (45 degrees) 21 was formed by dry etching.
Furthermore, after the optical second harmonic generation region 19 and a part of the ω reflection film 20 were removed by dry etching, the n-electrode 22 and the p-electrode 23 were formed by vapor deposition.

The light having an angular frequency ω and a vacuum wavelength λ ₁ = 860 nm emitted from the semiconductor laser structure 18 is reflected by the first inclined reflection surface 21 and proceeds to the second optical harmonic generation region 19 and the ω reflection film 20. Second harmonic generation region 1 due to nonlinear effect
At 9, light having an angular frequency of 2ω and a vacuum wavelength of λ ₂ = 430 nm is generated, transmitted through the ω reflection film 20, and emitted to the outside. The second optical harmonic generation region 19 has a periodic structure of ZnSe and ZnS _0.2 Se, and satisfies the phase matching condition for light of ω and 2ω.

Since the ω reflection film 20 satisfies the Bragg reflection condition for the light of ω due to the multilayer structure, it is all reflected, and the semiconductor laser structure is fed back to 18 and contributes to the laser oscillation. Since the semiconductor material has a different refractive index depending on the frequency of the light, the ω reflection film 20 does not satisfy the Bragg reflection condition with respect to the light having an angular frequency of 2ω and transmits the light of 2ω. Since the conversion efficiency to the optical second harmonic increases as the intensity of the light having the angular frequency ω increases, the light having the angular frequency 2ω can be efficiently obtained by introducing the ω reflection film.

In the third embodiment described above, the invention of claim 4 is applied to the invention of claim 2, but the invention of claim 3 may be further combined.

[0034]

As described above, according to the present invention, an optical second harmonic light emitting device having excellent characteristics and integrated with a semiconductor laser can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 semiconductor substrate 2 p-type cladding layer 3 active layer 4 n-type cladding layer 5 grating 6 n-type ZnS _0.2 Se _0.8 layer 7 n-type ZnSe layer 8, 22 n-electrode 9, 23 p-electrode 10, 17, Reference Signs List 21 first inclined reflecting surface 11 second inclined reflecting surface 12, 14, 18 semiconductor laser structure 13, 16, 19 second optical harmonic generation region 15 2ω reflection film 20ω reflection film

Claims (4)

(57) [Claims] 1. A semiconductor laser structure having a horizontal semiconductor laser structure in which the angular frequency of oscillation light formed on a semiconductor substrate is ω, a first inclined reflection surface on one end surface of the laser structure, A second harmonic generation region made of a semiconductor material that transmits light having an angular frequency of 2ω and has a second-order nonlinear optical characteristic stacked on a laser structure; and the second light generation region on the first inclined reflection surface. The second harmonic generation region has a second inclined reflection surface, the optical second harmonic generation region has a waveguide structure or a grating structure, and is phase-matched to light having angular frequencies ω and 2ω. The light of the angular frequency ω emitted from the laser structure is guided to the optical second harmonic generation region by the first inclined reflection surface and the second inclined reflection surface, and is converted into light of the angular frequency 2ω. It emits light with an angular frequency of 2ω in the horizontal direction. The light-emitting element. 2. A semiconductor laser having a horizontal semiconductor laser structure in which an angular frequency of oscillation light formed on a semiconductor substrate is ω, a first inclined reflection surface on one end surface of the laser structure, An optical second harmonic generation region made of a semiconductor material having a second-order nonlinear optical characteristic and transmitting light at an angular frequency of 2ω laminated on the laser structure, wherein at least two types of the optical second harmonic generation regions are provided; It has a multilayer structure made of the above semiconductor material, is phase-matched with respect to the angular frequencies ω and 2ω light, and emits the light having the angular frequency ω emitted from the laser A light-emitting element which is guided to a harmonic generation region, converted into light having an angular frequency of 2ω, and emits light having an angular frequency of 2ω in a vertical direction. 3. A 2ω light reflection film comprising a semiconductor multilayer film satisfying a Bragg reflection condition for light having an angular frequency of 2ω between the semiconductor laser structure and the optical second harmonic generation region. Item 3. The light emitting device according to item 1 or 2. 4. An ω light reflection film having a multilayer structure of at least two types of semiconductor layers that satisfies the Bragg reflection condition for angular frequency ω light above the optical second harmonic generation region. The light emitting device according to claim 2.