JPH0548198A - Semiconductor second harmonic light emitting device - Google Patents

Abstract

PURPOSE:To form a second harmonic light emitting device. CONSTITUTION:The titled device is provided with horizontal semiconductor laser structure 12, a second optical laminated harmonic generation region 13 and a slanting type reflected plane 10 which leads oscillation laser light to the second harmonic generation region 13. The phase conformity conditions are satisfied by a grating 5 and multilayer film structure. The device is integrated with the laser and enables second harmonics to be effectively generated.

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 has been attempted by generation of an optical second harmonic. The use of a semiconductor as a nonlinear material is highly suitable for using a semiconductor laser as an excitation light source (Journal of Crystal Grouse [Journal]
of Crystal Growth] Volume 101 55
0 page, 1990).

[0003]

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

[0004]

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

(1) It has a horizontal type semiconductor laser structure in which the angular frequency of oscillation light formed on a semiconductor substrate is ω,
An optical second harmonic composed of a semiconductor material having a first inclined reflection surface on one end face of the laser structure and having second-order nonlinear optical characteristics laminated on the semiconductor laser structure and transmitting light with an angular frequency of 2ω. A wave generation region, a second inclined reflection surface in the optical second harmonic generation region on the first inclined reflection surface, and a waveguide structure or a grating structure in the optical second harmonic generation region. And phase-matched to the light of the angular frequencies ω and 2ω, and the light of the angular frequency ω emitted from the laser structure is converted into the optical first by the first inclined reflection surface and the second inclined reflection surface. It is guided to the second harmonic generation region and converted into light with an angular frequency of 2ω, and the angular frequency is 2ω in the external horizontal direction.
A light emitting element characterized by emitting the light of.

(2) It has a horizontal semiconductor laser structure in which the angular frequency of the oscillation light formed on the semiconductor substrate is ω,
An optical second harmonic composed of a semiconductor material having a first inclined reflection surface on one end face of the laser structure and having second-order nonlinear optical characteristics laminated on the semiconductor laser structure and transmitting light with an angular frequency of 2ω. Has a wave generating region, the optical second harmonic generating region has a multi-layer structure made of at least two kinds of semiconductor materials, is phase-matched to angular frequency ω and 2ω light, and radiates 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 the light having the angular frequency 2ω, and the light having the angular frequency 2ω is emitted in the vertical direction. And a light emitting element.

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

(4) A ω light reflection film having a multilayer structure of at least two kinds of semiconductor layers satisfying the Bragg reflection condition for the angular frequency ω light is provided on the upper side of the optical second harmonic generation region. The light emitting device according to (2) above.

[0009]

The light emitting device according to the present invention employs a structure in which the light emitted by the semiconductor laser is reflected by the inclined reflection surface and guided to the optical second harmonic generation region. With this structure, in the second harmonic generation region, crystals can be continuously grown after the semiconductor laser layer is grown. Further, since the semiconductor material is used for the optical second harmonic generation region, a high quality multilayer film and a waveguide can be obtained by matching the lattice constants of the materials.

In order to obtain the optical second harmonic, the phase matching condition must be satisfied, but this condition is easily achieved by using the dispersion relation by the waveguide structure and introducing the periodicity by the multilayer structure or the grating structure. I am satisfied.

The phase matching condition based on the periodic structure is such that the length of one period is d and the angular frequencies ω and 2ω in the optical second harmonic generation region.
When the wave numbers of the light in the substance are k ₁ and k ₂ , respectively, n · 2π / d = k ₂ −k ₁ (n = ± 1, 2, ...) Is satisfied.

Since the 2ω light reflecting film according to claim (3) satisfies the Bragg reflection condition for light having an angular frequency of 2ω, of the 2ω light generated in the optical second harmonic generation region, it advances toward the substrate. The light is reflected by the 2ω light reflection film and is extracted as output light from the upper surface of the substrate to the outside. Since the 2ω light reflection film has a transmission characteristic for the angular frequency ω light, the light of the angular frequency ω generated in the semiconductor laser region passes through the 2ω light reflection film,
It effectively reaches the optical second harmonic generation region. By adding the 2ω light reflecting film, the conversion efficiency to 2ω becomes high.

The ω reflection film according to claim 4 has an angular frequency ω
Since the Bragg reflection condition is satisfied for the light, the light having the angular frequency ω that travels upward in the optical second harmonic generation region is reflected.
Therefore, the intensity of the angular frequency ω light in the optical second harmonic generation region is increased, and the conversion efficiency into the optical second harmonic is increased.
The refractive index of the semiconductor layer changes depending on the frequency, and the Bragg reflection conditions for the light of 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, it is possible to efficiently extract the optical second harmonic.

[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 invention of claim 1.

P is formed on the semiconductor substrate 1 made of p-type GaAs.
N-type cladding consisting form Al _0.4 Ga _0.6 As p-type cladding layer 2 made of (thickness 1 [mu] m), the active layer 3 of GaAs (thickness 0.1 [mu] m), the n-type Al _0.4 Ga _0.6 As (thickness 1 [mu] m) After the layer 4 was formed by the molecular beam epitaxy method, the grating 5 having a period of 1.05 μm was formed by using the interference exposure method. By the molecular beam epitaxy method again,
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. Then, the n electrode 8 and the p electrode 9 were formed by vapor deposition, and then the first inclined reflection surface (angle 45 degrees) 10 and the second inclined reflection surface (angle 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 is composed of the n-type cladding layer 4, and the n-type ZnS _0.2 Se _0.8 layer 6 and the n-type Zn
It is composed of the Se layer 7.

[0017] When the current from the electrodes 8 and 9 has been injected, and the wavelength in vacuum of optical angular frequency ω emitted from the semiconductor laser structure 12 to lambda _1, was lambda ₁ = 860 nm. Light having a wavelength of 860 nm is reflected by the first inclined reflection surface 10 and the second inclined reflection surface 11, travels through the second optical harmonic generation region 13, and has an angular frequency of 2ω and a wavelength of λ ₂ = 430.
nm light is generated.

The phase matching condition for the angular frequency ω and 2ω light may be 2π / d = k ₂ -2k ₁ with the grating period d and the wave numbers k ₁ and k ₂ , respectively, and for ZnSe d = 1. It may be set to 05 μm.

For the light of the angular frequency ω, the optical second harmonic generation region 13 is a part of the resonator of the laser oscillation, so that the electric field strength is strong and the wavelength conversion efficiency is 5% under a good condition. 430 nm blue light was obtained.

ZnSe has almost the same lattice as GaAs,
Good crystals are easily obtained. Further, since the SHG structure is formed by crystal growth, the device can be easily handled and mass production is possible.

In the above-mentioned embodiments, the grating structure is used as a method for achieving phase matching, but the method is not limited to this, and a waveguide structure may be used.

(Embodiment 2) Next, FIG. 2 shows a sectional view of 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 consisting of 10 layers of ZnSe and ZnS _0.2 Se, both having a thickness of 36 nm, ZnSe (thickness 0.525 μm).
And ZnS _0.1 Se _0.9 (thickness 0.525 μm), an optical second harmonic generation region 16 having 10 cycles is formed by a molecular beam epitaxy method, and then a 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 reflection surface 17. The 2ω reflective film 15 has a wavelength of 860n.
The light of m has a high transmission rate, and the light enters the optical second harmonic generation region 16.

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

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

In Examples 1 and 2 described above, Zn was used as the nonlinear material.
Although the SSe layer is used, the present invention is not limited to this, and a ZnSSe strained superlattice or another semiconductor material may be used.

Further, although the DH structure semiconductor laser is used in the above-mentioned embodiments, the quantum well structure laser may be used without being limited to this.

(Embodiment 3) Next, FIG. 3 shows a sectional view of an embodiment 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 (thickness 84 nm) and ZnS _0.1 Se _0.9
After forming the ω reflection film 20 having a thickness of 84 nm and 10 cycles by the molecular beam epitaxy method, the first inclined reflection surface (45 degrees) 21 was formed by the dry etching method.
Further, a part of the second harmonic generation region 19 and the ω reflection film 20 was removed by dry etching, and then the n electrode 22 and the p electrode 23 were formed by vapor deposition.

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. Optical 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, passes through the ω reflection film 20, and is emitted to the outside. The second optical harmonic generation region 19 has a periodic structure of ZnSe and ZnS _0.2 Se, and the phase matching condition is satisfied for the lights of ω and 2ω.

Since the ω reflection film 20 satisfies the Bragg reflection condition for the ω light due to the multilayer film 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 light, the ω reflection film 20 does not satisfy the Bragg reflection condition for light having an angular frequency of 2ω, and transmits 2ω of light. The conversion efficiency to the second harmonic wave of light becomes higher as the intensity of the light of the angular frequency ω becomes stronger. Therefore, by introducing the ω reflection film, the light of the angular frequency 2ω could be efficiently obtained.

In the above-mentioned third embodiment, 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 integrated with a semiconductor laser can be easily obtained.

[Brief description of drawings]

FIG. 1 is a cross-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.

[Explanation of symbols]

1 semiconductor substrate 2 p-type clad layer 3 active layer 4 n-type clad 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, 21 first graded type Reflection surface 11 Second inclined reflection surface 12, 14, 18 Semiconductor laser structure 13, 16, 19 Optical second harmonic generation region 15 2 ω reflection film 20 ω reflection film

Claims (4)

[Claims] 1. A semiconductor laser structure of a horizontal type having an angular frequency of ω of oscillated light, which is formed on a semiconductor substrate, and has a first inclined reflection surface on one end face of the laser structure, An optical second harmonic generation region, which is laminated on a laser structure and has a second-order nonlinear optical characteristic, and which is made of a semiconductor material that transmits light having an angular frequency of 2ω, is provided. 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 with light of angular frequencies ω and 2ω; Light having an 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 converted into light having an angular frequency 2ω, Characterized by emitting light with an angular frequency of 2ω in the horizontal direction The light-emitting element. 2. A semiconductor laser structure of a horizontal type having an angular frequency of ω of oscillating light formed on a semiconductor substrate, wherein a first inclined reflection surface is provided on one end face of the laser structure, An optical second harmonic generation region having a second-order nonlinear optical characteristic laminated on a laser structure and made of a semiconductor material that transmits light having an angular frequency of 2ω, and the optical second harmonic generation region is at least two types. It has a multi-layered structure made of the above semiconductor material, is phase-matched to the angular frequency ω and 2ω light, and emits the light of the angular frequency ω emitted from the laser structure by the first inclined reflection surface to the optical second A light emitting element, which is characterized in that it is guided to a harmonic generation region, converted into light with an angular frequency of 2ω, and emits light with an angular frequency of 2ω in the vertical direction. 3. A 2ω light reflecting film made of a semiconductor multilayer film satisfying a Bragg reflection condition for light having an angular frequency of 2ω is provided between the semiconductor laser structure and the second optical harmonic generation region. Item 3. The light emitting device according to item 1 or 2. 4. An ω light reflection film having a multi-layered structure of at least two kinds of semiconductor layers satisfying a Bragg reflection condition for an angular frequency ω light is provided above the optical second harmonic generation region. The light emitting device according to claim 2.