JPH036077A - semiconductor light source - Google Patents

Abstract

PURPOSE:To improve secondary harmonic conversion efficiency by providing optical waveguides having functions of laser emission, secondary harmonic generation, and optical guide formed on the same flat plane, a laser resonator formed of the laser emission optical waveguide and of the secondary harmonic generation optical waveguide, and means for converging a plurality of lights to a single light. CONSTITUTION:Optical waveguides 11, 13, 16, 17 are formed on the same plane on a substrate 10, and a laser resonator is constructed with the optical waveguides 11, 13. The laser resonators 11, 13 induce lasing, and the optical waveguide 13 induces second harmonic generation(SHG) therein. SHG optical energy is emitted from the end surface of optical waveguide 13 and introduced into an optical waveguide 13 and introduced into an optical waveguide 15. The optical waveguide 15 branches corresponding to a laser exit port on the side of the laser resonators 11, 13, while being converged to form an optical waveguide 16 on the opposite side. Accordingly, a plurality of the SHG lights introduced into the optical waveguide 15 are focused to a single one in the course of their propagation and are adjusted in their phases and spreadings by the optical waveguide 16, and are finally emitted from the end surface as a single light. Thus, secondary harmonic conversion efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to the structure and manufacturing method of a device for generating second harmonics of semiconductor laser light, which is characterized by being integrated.

[Conventional technology]

Conventionally, second harmonic generation (hereinafter referred to as SHG) of semiconductor laser light
(abbreviated as ) was attempted, and applied physics
Applied Physics Letts
ers ) Vol, 35. No, 6f19791P,
461-P453 and Nikkei New Material 1987 4
Monthly 20th issue P, 96-P, 105k: As can be seen, a module has been devised that combines a semiconductor laser and a waveguide type SHG element.

For example, a collimating lens for optical pickup (numerical aperture 0.3) and a focusing lens (numerical aperture 0.6) t
', the light is focused and coupled to the waveguide end face of a waveguide-type SHG element formed around a LiNbO5 single crystal, and SHG is generated within the LiNbO3 single crystal waveguide. An example of the dimensions of the entire module is 10X10X10X30'
It is.

[Problems to be Solved by the Invention] However, the following problems remain with the above-mentioned module.

1. Because it is modularized, it is impossible to integrate the brainer as a component of an optoelectronic integrated circuit.

2. Since the SHG element requires a large single crystal of extremely high quality, the manufacturing cost becomes high.

3. Since the optical waveguide is usually a thin film layer with a thickness of 1 μm, strict precision is required for center alignment and parallelism adjustment of the semiconductor laser's leading waveguide and the SHG element's leading waveguide, making it a complex technology. .

Poor workability.

4. The SHG conversion efficiency is low, and the optical output is below the 1 mW level.

5. LxNbOs single crystals are unstable and prone to optical damage in the visible wavelength range.

The present invention is intended to solve this problem, and its purpose is to obtain a brainer integrated device by fully applying semiconductor evitational technology.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the integrated second harmonic generation device of the present invention is characterized by having the following structural requirements as means thereof.

1. Select a 5-compound semiconductor as the crystal material for SHG.

2 The compound semiconductor has an MO on the semiconductor laser substrate surface.
CVD erectile growth is possible.

3. The evitational growth includes selective formation.

4. The SHG function section has an optical waveguide structure.

58 The guide wavepath is constructed on a plane including the active layer of the optical resonator section of the semiconductor laser, and the laser beam is directly directed to the SH
incident on the G crystal.

6. The setting of the semiconductor laser oscillation conditions is based on the assumption that the semiconductor laser is configured to include both the leading waveguide of the semiconductor laser and the optical waveguide of the SHG function section coupled thereto. That is, the SHG crystal is placed within the laser resonator.

7. Form a thin film on the SHG light output end face (5) that reflects the G excitation source laser beam and transmits the SHG tip.

8. Phase matching between the excitation laser beam and the SHG light is set so that the lowest order mode of the excitation wave and the higher order mode of the SHG are matched by using the mode dispersion of the optical waveguide.

9.5) IG light is focused by a light guide consisting of a leading waveguide to reduce the spread of light.

[Implementation example J This example has the following settings.

■ The excitation laser beam is Iny Ga+-y As (y
= 0.5) One oscillation wavelength is 11,000 depending on the active layer configuration.
n light.

2. Select a compound semiconductor superlattice structure as the SHG crystal material.

3 The compound semiconductor has an MO on the semiconductor laser substrate surface.
CVD or MOMBE evixial growth is performed to form a superlattice structure.

4. Phase matching between basic excitation laser light and SHG light.

5) Matching of effective refractive indexes is achieved by controlling the thickness of the IG leading waveguide.

5. The laser beam resonator is of a Fapley bellows type, and is designed to include a laser emitting part and a 5l (G part).

6. Form a light guide waveguide to guide and collect light.

7. The optical guide waveguide forms a Schottky barrier for the purpose of adjusting the optical phase and has a metal thin film electrode that applies a reverse bias voltage.

Next, the function and structure will be described.

In FIG. 1, on a substrate 10, optical guides 11, 13.
16 and 17 are formed on the same plane, 11 is a part that causes emission excitation, and the laser resonator is a Fabry-Perot type including 11 and 13. That is, the free end surface of 11 and the free end surface of 13 constitute a parallel reflecting mirror 6.
Laser oscillation occurs within the laser resonator, and at the same time, SHG is generated within the guide waveguide 13. 5) For the purpose of increasing the efficiency of IG generation, as will be described later, the leading waveguide 13 is formed by repeatedly laminating ultrathin films of TI-Vl group 2 materials, such as ZnS/Zn5e. This is to increase the thickness of the nonlinear optical effect.Furthermore, in order to achieve phase matching between the laser beam and the SHG light, by adjusting the thickness of the entire stack, for example, the zero-order mode of the laser beam and the S[(G light It is sufficient to make the effective refractive index of the next mode equal.There is a degree of SHG optical energy content that can be generated by a single laser resonator.Therefore, in order to increase the SHG optical energy content, the laser resonator structure is , as shown in Fig. 1, are arranged and formed in parallel.This can be realized by a single process, for example, N
If they are arranged in parallel, the amount of SHG light energy will be N times larger. At this time, for lateral optical confinement of the laser resonator, a thin film layer made of the material 13 is left in the portion 12, and the material 13 is etched away in the portion 14 to form an air layer. The S
[(G optical energy is emitted from the end face of the optical waveguide 13 and introduced into another leading waveguide 15.
5 are formed coplanar and made of the same material, and the exit port 5 and the entrance port 5 match extremely accurately, allowing effective light entry. The optical waveguide 15 is branched on the laser resonator side, corresponding to the laser resonator exit, and is converged on the opposite side to form a single linear leading waveguide 16. Therefore, the plurality of SHG lights introduced into the waveguide section 15 are condensed into a single light beam while traveling, and finally
6, one phase and spread are adjusted, and the light is emitted as a single light from the end face. Since the lengths of the branching leading wavepath sections are different, there is a drawback that an optical path difference between the respective SHG lights occurs. For this purpose, a thin metal film 17 is deposited on each branch portion to form a Schottky barrier, and the depletion layer of the barrier is formed to be thicker than the branch leading waveguide. By using the metal vapor deposited film as an electrode and applying a reverse bias voltage through the lead wire 18, the electric field strength of the depletion layer can be individually increased or decreased. In this way, due to the electro-optic effect of each branched optical waveguide,
The phase of each SHG light can be increased or decreased. By this increase/decrease, the 5 optical phases are made to coincide with each other.3 Furthermore, the laser beam resonators are formed with an interval of about microns between adjacent laser beam resonators, and by optically coupling the adjacent laser beam resonators, the N laser beam resonators are optically coupled. All the laser beams are made to have the same phase (6), that is, a directional coupler is formed.

As described above, by condensing a plurality of SHG lights, it is possible to extract extremely high-intensity SHG light, and the light source has a single phase.

Although the guide waveguide section 15 is of a branched type, it is relatively easy to form a Fresnel lens thereon, and a method of condensing light using the lens effect has also been realized.

Next, a manufacturing method for the structure of the present invention will be described.

FIG. 2 is a diagram showing the structure of a semiconductor laser section, ie, a cross section taken along line AA' in FIG. 1, showing an embodiment of the present invention. 20 is an n-GaAs substrate, and 21 is an n-GaAs buffer layer.

22 is n-AlxGa+-xAs (x = O, l l.

23 is n-InyGat-yAsf y=0.0
51°24 is low AlxGa+-xAs (x = 0.
11 and 25 are P −AlxGa r −xAsfx=
0.11, 26 is the n-GaAs gap calendar. 27 is a 5iOz film, 28 is a znK dispersion region, and n-AlxG
It diffuses to a depth up to the boundary between the aAs layer 22 and the n-GaAs buffer layer 21. As a result, n-In
yGat-yAs('/=0.051) Zn is diffused into a portion 2'' of the layer 23 and the portion becomes P-type, forming an active layer.

Each of the aforementioned layers is epitaxially grown on the substrate 20 by MOCVD. The MOCVD conditions are as follows.

Substrate temperature +760”~820°C pressure
Power + 760Torr V group/III group ratio = 50
~100 Growth rate, 007 μm/min MOCVD source gases are trimethylgallium, trimethylaluminum, trimethylindium, and arsine. The Zn diffusion region is formed by a well-known diffusion method. A 2μX 150u window was opened in the 5iOz film 27, and 6
Diffuses between 00°C and 650°C. Zn concentration is 1. x l
O1@/cm”.

Next, in order to form the SHG tel function part shown in FIG. 1, the right side of FIG. 1 B-B' is removed by etching up to the n-GaAs buffer layer 21 shown in FIG.

On the exposed n-GaAs 21 surface, a Zn5xSe1-y cladding layer and a waveguide layer constituting the SHG function guiding waveguide are epitaxially grown. The etching is performed by the RIBE method using an ECR type plasma apparatus. CC1 was used as the etching gas. Compared to the chemical etching process, the RIBE process results in an extremely smooth etched surface 9 with some corners formed at right angles, resulting in a favorable shape.6 Therefore, a good epitaxial growth surface is obtained. can get. Using this surface as a substrate, S
Form the HG functional section. Figure 1 B-B' cross section right 151
The epitaxial growth method of the 1S HG functional section will be explained with reference to FIG. First, thermal CV is applied on the GaAs substrate 34.
SiO□ of the mask 34 is deposited by the D method or the like.

In this state, patterning 5102 is performed using the zero-order photolithography technique as shown in FIG. 3(a). At this time, the SiO□ in the portion where the waveguide layer will be formed is removed by etching. This state is shown in FIG. 3(b). Zn5xSe+-x32 of the cladding layer was formed by selective epitaxial growth using the patterned 5iOz as a mask.
Furthermore, a waveguide layer 33 is continuously formed thereon in the same growth furnace. At this time, there is no deposit on the mask SiO□, resulting in a state as shown in FIG. 3(C). The selective epitaxial growth can be achieved by the following method. 2n as a raw material,
Using organic compounds of S and Se, the growth pressure is 1oOTo
rr or less, growth temperature is 400°C or more and 700°C or less, Vl
Reduced pressure M under conditions where the molar ratio of group raw material and group 111 raw material is 6 or less
It is carried out by OCV D method or MOMBE method.

The ZnS/Zn5e superlattice evixial film is made from the raw material S
By alternately supplying organic compound vapors of and Se according to a sea fence for a preset time, films each having a thickness of 10 to 100 angstroms are laminated one after another. After forming the laminated layers, the SiO□ is removed using a hydrofluoric acid etchant, and a leading waveguide is completed as shown in FIG. 3(d). In the above example, SiO□ was used as the mask material, but other dielectric thin films such as 5idL or metal thin films such as W may be used in the same manner. Furthermore, ZnS/Z
Although an n5e superlattice epitaxial film was used, CdS/C
dSe superlattice, 2nTe/znSe superlattice, CdSe/
Zn5a superlattice, CdS/ZnS Ml lattice are also applicable.

In addition, an interference filter is formed by vapor deposition on the output end face of the leading waveguide 16, so that 100% of the laser beam is reflected, and the SH
Let us take out only the G destination.

As a result of the above, it was possible to generate SHG light with a wavelength of 500 nm, and achieve an optical output of 30 m W SHG light.

[Effect of the invention] As explained above, the present invention has the following effects.

1. Extremely compact and can be handled in the same way as conventional IC chips.

2. Brainer integration is possible as a constituent element of an optoelectronic integrated circuit.

3. No need for high-quality large single crystals.

4.30mW class semiconductor laser can be realized, and 100mW class semiconductor laser can be realized.
We can also expect mW class.

5. Can be manufactured by applying conventional IC technology.

6. Therefore, mass production is possible and manufacturing costs can be reduced.

7. By MOCVD epitaxial growth of the SHG crystal, high quality integrity can be ensured and high conversion efficiency can be obtained.

8. Due to the superlattice evixial film layer, extremely high nonlinear optical constants can be obtained, and high conversion efficiency can be achieved.

9. The design of the leading waveguide of the light guide corresponding portion can be easily changed according to the purpose, and the degree of freedom is extremely high.

As mentioned above, it can be expected to bring about a very wide range of useful effects, and is particularly useful as a light source for magneto-optical distribution systems and laser printers.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic planar structure of an embodiment of a semiconductor light source of the present invention. FIG. 2 is a diagram showing a transparent structure of a semiconductor laser section in an embodiment of the semiconductor light source of the present invention. FIGS. 3(a) to 3(d) are diagrams illustrating a process for manufacturing an SHG functional light guide waveguide in an embodiment of the semiconductor light source of the present invention. IO... Substrate 11... Laser emission optical waveguide 12... Optical confinement layer 13... Second harmonic generation optical waveguide 14... Optical confinement layer 15... Optical guide waveguide for focusing light 16... Guide wave path 17... Schottky thin bar electrode 18... Lead wire 20... n-GaAs substrate 21-- - n-GaAs buffer layer 22--
n-AlxGa+, ++As23 ・--InyG
a+-, As (including active layer) 24- ・-n-Al
xGa+-xAs25--- P-A1xGa+-x
As-GaAs/SiO□n/Zn diffusion region GaAs substrate Zn5xSe+-x cladding layer...Superlattice structure optical waveguide...5iOz mask 26 7 28 1 32 33 4

Claims (1)

[Claims] In a semiconductor light source configured monolithically, a plurality of three types of optical waveguides each having the functions of a laser emission function, a second harmonic generation function, and a light guide function are formed on the same plane, and the laser emission optical waveguide and A semiconductor characterized in that the second harmonic generation optical waveguide forms a laser resonator, optically couples adjacent laser resonators, and forms means for converging a plurality of lights into a single light. light source.