JPH0846296A - Second harmonic generator and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a compact second harmonic generator with high efficiency and high output at low cost by a method wherein a phase matched layer comprising a compound semiconductor having a periodic structure in periodically changing reflection index is formed on the beam emitting end face of a semiconductor laser. CONSTITUTION:For example, a crystal of a phase matching layer 16 is grown on the cleavage surface of an AlGaAs base semiconductor laser 15 by MOVPE or MBE. At this time, AlxGa1-xAs and AlyGa1-yAs is supposed to have larger band gap than the energy of the basic wave emitted from the AlGaAs base semiconductor laser 15. When the fundamental wave emitted from this AlGaAs base semiconductor laser 15 passes through the phase matching layers 16, a part of the fundamental wave is converted to the second harmonic. Therefore, a compact second harmonic generator with high efficiency and high output can be provided at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a second harmonic wave generator for generating a second harmonic wave (particularly, violet, blue and green monochromatic light) emitted from a compound semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, a nonlinear optical crystal (LiTa
Many methods using O ₃ , LiNbO ₃ etc.) have been proposed (eg, K. Yamamoto, K. Mizuuchi, Y. Kitaoka and M. Kato: A
ppl. Phys. Lett. 62 (1993) 2599). FIG. 14 shows an example of such a second harmonic generation device. In the figure, 1 is a semiconductor laser, 2 is a lens, 3 is a half-wave plate for preventing interference between an emission wave emitted from the semiconductor laser 1 and a feedback wave returned to the semiconductor laser 1, and 4 is a semiconductor laser 1 A quasi phase matching type phase matching layer 5 for converting a part of the emitted compound semiconductor laser light, which is the fundamental wave, into a second harmonic wave is a surface for the second harmonic wave output from the quasi phase matching type phase matching layer 4. A wavelength selection mirror which reflects in the direction, and 6 is a grating which scans the oscillation wavelength of the semiconductor laser 1.

The quasi phase matching type phase matching layer 4 is formed by forming an optical waveguide 4b on a nonlinear optical crystal 4a and further forming polarization inversion layers 4c inside the optical waveguide 4b at intervals of several μm to several tens of μm. The compound semiconductor laser light emitted from the semiconductor laser 1 is incident on the optical waveguide 4b to generate the second harmonic. Further, in the system shown in FIG. 14, the fundamental wave emitted from the optical waveguide 4b is reflected by the grating 6 provided outside the laser oscillation portion.
Returned to. Thereby, the light is returned to the semiconductor laser 1 through the original optical path. Since the oscillation wavelength of the semiconductor laser 1 can be scanned by changing the angle of the grating 6, the oscillation wavelength of the semiconductor laser 1 can be locked to a wavelength that is phase-matched with the second harmonic, and high output and stable A second harmonic can be generated.

A second harmonic generation device applied to a surface-emitting type semiconductor laser has also been proposed by taking advantage of the large nonlinear coefficient of GaAs / AlGaAs compound semiconductors. An example of this type of second harmonic generation device is shown in FIG. FIG.
7 is a semiconductor laser in which the active layer 7a is sandwiched between the cladding layers 7b and 7c, 8 is an insulating film formed on the lower surface of the cladding layer 7c, and 9a is an opening in the center of the insulating film 8.
The reflection film 10 formed on the lower surface of c is a clad layer 7c at the peripheral portion of the reflection film 9a in the opening in the central portion of the insulating film 8.
The electrode that contacts the. A substrate 11 is formed on the upper surface of the clad layer 7b. A horn-shaped hole is provided in the center of the substrate 11 so as to reach the cladding layer 7b, and the electrode 12 extends from the inner wall of the hole to the surface of the substrate 11.
Are formed. 13 is an electrode 12 on the surface of the substrate 11.
Is an insulating film formed between the substrate 11 and the substrate 11. Further, the phase matching layer 14 is formed on the bottom of the opening of the substrate 11,
A reflective film 9b is formed on the phase matching layer 14. In the example shown in FIG. 15, the phase matching layer 14 is provided inside the vertical resonator composed of the reflective films 9a and 9b, which are dielectric multilayer films, sandwiching the semiconductor laser 7 to achieve a high efficiency It can generate harmonics.

[0005]

However, as shown in FIG.
In a conventional example using a non-linear optical crystal (LiTaO ₃ , LiNbO ₃ etc.) as shown in (1), the size of the device becomes large and the cost is high because it is composed of multiple parts. There is a problem in that the manufacturing cost is further increased because extremely complicated adjustment is required for optical axis alignment, grating angle alignment, and the like.

Further, by utilizing the large nonlinear coefficient of GaAs / AlGaAs type compound semiconductor, in the second harmonic generation device applied to the surface emitting type semiconductor laser as shown in FIG. Since the phase matching layer is provided in addition to the active layer in the vertical resonator formed of a film, if the thickness of the phase matching layer is increased, the absorption loss in the phase matching layer increases and the laser oscillation cannot be sustained. Moreover, the current surface-emitting type semiconductor laser has an optical output of about several mW, and the optical output of the edge-emitting type high-power semiconductor laser (several 100 mW to several W).
Is much smaller than For this reason, there is a drawback in that the generated second harmonic wave cannot output enough power.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a structure of a second harmonic generating device which can be miniaturized, has high efficiency, high output and low manufacturing cost, and a manufacturing method thereof. To provide.

[0008]

In order to achieve the above object, a second harmonic generator according to claim 1 is formed on a semiconductor laser and a light emitting end face of the semiconductor laser, and has a periodic refractive index. And a phase-matching layer made of a compound semiconductor having a periodic structure that changes into

A second harmonic generation device according to a second aspect is the second harmonic generation device according to the first aspect, wherein a first reflecting mirror formed of a multilayer film is formed between the semiconductor laser and the phase matching layer. A second reflecting mirror made of a multilayer film for transmitting the second harmonic is formed on the second harmonic emitting surface of the phase matching layer.

A second harmonic generation device according to a third aspect is the second harmonic generation device according to the first aspect, wherein the second harmonic generation device comprises a multilayer film on a surface opposite to the light emitting end surface of the semiconductor laser. A third reflecting mirror is formed, and a fourth reflecting mirror made of a multilayer film and transmitting the second harmonic is formed on the second harmonic emitting surface of the phase matching layer.

A second harmonic generation device according to a fourth aspect is the second harmonic generation device according to any one of the first to third aspects,
The semiconductor laser is divided into a plurality of semiconductor laser structures by grooves parallel to the light emitting end face.

A second harmonic generation device according to a fifth aspect is the second harmonic generation device according to the fourth aspect, wherein a part of the separated semiconductor laser structure is a distributed Bragg reflection type laser structure. It is characterized by.

According to a sixth aspect of the present invention, there is provided a second harmonic wave generating device, wherein the second harmonic wave generating device according to any one of the first to fifth aspects is formed on a substrate and the phase matching layer emits the second harmonic wave. On the surface side, a light extraction reflecting mirror is formed on the substrate so that the reflecting surface faces the second harmonic wave emitting surface at an angle of about 45 degrees. .

A second harmonic generation device according to a seventh aspect is the second harmonic generation device according to the sixth aspect, characterized in that a predetermined refractive index distribution structure is formed on the reflecting surface. Is.

A second harmonic generation device according to claim 8 is the second harmonic generation device according to claim 7, characterized in that electrodes are formed above and below the light extraction reflecting mirror. Is.

A method of manufacturing the second harmonic generation device according to claim 9 is the method of manufacturing the second harmonic generation device according to any one of claims 1 to 8, wherein: The phase matching layer is formed by a process including a crystal growth process.

According to a tenth aspect of the present invention, there is provided a method of manufacturing a second harmonic wave generating device according to any one of the first to eighth aspects of the present invention, wherein an ion or focused ion beam is implanted. The phase matching layer is formed by a process including a heat treatment process after the implantation process.

A method for manufacturing a second harmonic generation device according to claim 11 is the method for manufacturing a second harmonic generation device according to any one of claims 1 to 8, wherein the second harmonic generation device is parallel to the light emitting end face of the semiconductor laser. The phase matching layer is formed by a step including an etching step of forming a groove by etching.

A method for manufacturing a second harmonic generation device according to a twelfth aspect is the method for manufacturing a second harmonic generation device according to the eleventh aspect, which includes a step of burying an insulating film or a compound semiconductor in the groove. The phase matching layer is formed by.

[0020]

A second harmonic generation device according to claim 1 is a second harmonic generation device for obtaining a light output of a second harmonic with respect to a semiconductor laser beam, wherein a periodic refractive index is provided on a light emitting end face of the semiconductor laser. It is characterized in that a phase matching layer made of a compound semiconductor having a structure is formed. With such a structure, the power of the semiconductor laser light incident on the phase matching layer can be increased.

The second harmonic wave generating device according to the second and third aspects is the second harmonic wave generating device according to the first aspect, in which reflecting mirrors made of a multilayer film are formed on both sides of the phase matching layer, It is characterized in that the reflecting mirror on the output side of the second harmonic is configured so that the second harmonic can pass therethrough. With such a configuration, the power of the semiconductor laser light incident on the phase matching layer is significantly increased. can do.

A second harmonic generation device according to claim 4 is the second harmonic generation device according to any one of claims 1 to 3, wherein the semiconductor laser has a plurality of semiconductor laser structures formed by grooves parallel to the light emitting end face. In this way, by using a part of the separated semiconductor laser structure as a wavelength tunable part, it is possible to provide a wavelength tunable function with the wavelength of the phase matching layer. The wavelength allowable range for matching can be widened.

A second harmonic generation device according to a fifth aspect is the second harmonic generation device according to the fourth aspect, wherein a part of the separated semiconductor laser structure is a distributed Bragg reflection type laser structure. With such a configuration, since the wavelength tunable width of the semiconductor laser is increased, the wavelength allowable range for the phase matching layer can be further widened.

According to a sixth aspect of the present invention, the second harmonic wave generating device has the second harmonic wave generating device according to any one of the first to fifth aspects formed on a substrate, and the phase matching layer has a second harmonic wave emitting surface side. In addition, the light extraction reflecting mirror is formed on the same substrate so that the reflecting surface forms an angle of about 45 degrees with respect to the second harmonic wave emitting surface. That is, the semiconductor laser portion, the second harmonic generating portion, and the grating are monolithically formed on the same substrate.
With such a configuration, it is possible to obtain a surface-emitting type second harmonic generation device that can be downsized and does not require adjustment such as optical axis alignment and has a low manufacturing cost.

A second harmonic generation device according to a seventh aspect is the second harmonic generation device according to the sixth aspect, wherein a predetermined refractive index distribution structure, a so-called grating structure, is separated from the semiconductor laser on the reflecting surface. It is characterized in that it is formed as an external resonator structure. With this structure, the oscillation wavelength of the semiconductor laser can be stabilized. Further, since it is not necessary to adjust the adjustment of the grating angle, it is possible to obtain a surface-emitting type second harmonic generation device with low manufacturing cost.

A second harmonic generation device according to claim 8 is the second harmonic generation device according to claim 7, characterized in that electrodes are formed on the upper and lower portions of the light extraction reflecting mirror, By thus configured and by injecting a current or applying an electric field to the light extraction reflecting mirror, it is possible to change the refractive index distribution of the reflecting surface of the light extraction reflecting mirror, and it becomes possible to select the wavelength in the grating structure.

Here, a III-V group compound semiconductor or I
As a method of generating the second harmonic of the phase matching layer made of the I-VI group compound semiconductor, a method of modulating the magnitude of the non-linear coefficient, a method of inverting the sign of the non-linear coefficient, and the like can be considered. For example, when modulating the magnitude of the nonlinear coefficient, the phase matching layer should be a III-V group compound semiconductor with a different composition or system (for example, AlGaAs, InGaAs, AlGaInP, InGaAsP).
Etc.) or II-VI group compound semiconductors (eg ZnSS)
e system, ZnCdSSe system, etc.) are alternately laminated. When the period is Λ, the wavelength of the fundamental wave is λ, and the refractive indices for the fundamental wave and the second harmonic are n (ω) and n (2ω), respectively, the period Λ is as follows. Λ = (λ / 2) / (n (2ω) -n (ω)) In the multilayer structure with this period Λ, the fundamental wave and the second harmonic wave are phase-matched and the fundamental wave wave is effectively the second harmonic wave. Is converted to.

[0028]

EXAMPLE The second harmonic generation of the present invention will be described below with reference to FIG.
An example of the raw device will be described. Figure 1 is the second harmonic
It is a perspective view of a generator. In the figure, 15 is a semiconductor laser
In an AlGaAs semiconductor laser, the active layer 15a and its active
And the cladding layers 15b and 15c sandwiching the elastic layer 15a.
Have been. Reference numeral 16 is a light emitting end of the AlGaAs semiconductor laser 15.
Al on the surface_xGa_1-xAs film 16a and Al_yGa_1-yAs film 16b
By alternately stacking Al _xGa_1-xAs / Al_yGa_1-yAs periodic structure
Is a phase matching layer formed with.

In the embodiment shown in FIG. 1, for example, the phase matching layer 16 is formed on the cleaved surface of the AlGaAs semiconductor laser 15 by crystal growth with MOVPE or MBE. Where Al _x Ga
_1-x As and Al _y Ga _1-y As are AlGaAs semiconductor lasers 1
It is assumed that the band gap is larger than the energy of the fundamental wave emitted from No. 5. The film thickness of the Al _x Ga _1-x As film 16a is set to t _1, and the refractive index for the fundamental wave and the second harmonic wave is n.
₁ (ω), n ₁ (2 ω), and the film thickness of the Al _y Ga _1-y As film 16b is t _2, and the refractive indices for the fundamental wave and the second harmonic are respectively
If n ₂ (ω) and n ₂ (2ω) and the wavelengths of the fundamental wave and the second harmonic wave are λ ₁ and λ ₂ , the film thickness t _{1 of} the Al _x Ga _1-x As film 16a is
The film thickness t ₂ of the Al _y Ga _1-y As film 16b is as follows. t ₁ = (n ₁ (2ω) / λ ₂ -2n ₁ (ω) / λ ₁ ) ^-1 / 2 t ₂ = (n ₂ (2ω) / λ ₂ -2n ₂ (ω) / λ ₁ ) ^-1 / 2 The film thickness t _{1 of} the Al _x Ga _1-x As film 16a and the Al _y Ga _1-y As film 1
The film thickness t ₂ of 6b is also applied to the embodiments described below, and when the fundamental wave emitted from the AlGaAs semiconductor laser 15 passes through the phase matching layer 16, a part of the fundamental wave is the second harmonic wave. Will be converted to.

Next, a different embodiment of the second harmonic generation circuit will be described with reference to the perspective view of FIG. While the second harmonic generation device shown in FIG. 1 has a phase matching layer formed on the interface of the semiconductor laser, the embodiment shown in FIG.
An AlGaAs semiconductor laser 18 similar to that of the embodiment shown in FIG. 1 is formed on the As substrate 17, and the AlGaAs semiconductor laser 18 is formed.
At least one of the end faces of the light emitting device was formed by etching (wet etching, RIE, RIBE, etc.), and the phase matching layer 19 was formed on the light emitting end face by crystal growth using MOVEPE or MBE as in the example shown in FIG. It is a thing. In this embodiment, since the light emitting end face of the AlGaAs semiconductor laser 18 is formed by etching, when the end face is formed by the boundary shown in FIG. There is an advantage that the position of the end face is not restricted (the position where the end face is formed can be freely set).

A further different embodiment of the second harmonic generation device of the present invention will be described with reference to the perspective view of FIG. In the figure, 20 is an AlGaAs semiconductor laser, 21 is a phase matching layer (second harmonic generation part: SHG layer), and 22 is AlGaAs.
A distributed Bragg reflector (DBR layer) 23, which is a first reflecting mirror and is sandwiched between the semiconductor laser 20 and the phase matching layer 21, is a second reflecting mirror formed on the light emitting end face of the phase matching layer 21. Is a distributed Bragg reflector. FIG.
1 has a structure in which a phase matching layer 21 similar to that of the embodiment shown in FIG. 1 is sandwiched between distributed Bragg reflectors 22 and 23, and the power of the fundamental wave output from the AlGaAs semiconductor laser 20 is It is confined between the two distributed Bragg reflectors 22 and 23, and is configured to be very large in the phase matching layer 21. Since the generation of the second harmonic is effective as the square of the fundamental wave, a high-output second harmonic generator can be realized by the configuration of this embodiment.

AlGaAs semiconductor laser 20 and phase matching layer 2
As the distributed Bragg reflector 22 sandwiched between 1, for example,
For example, Al_zGa_1-zAs / Al_vGa_1-vAs compound semiconductor multilayer film
And the distribution formed on the light emitting surface of the phase matching layer 21.
The Bragg reflector 23 does not absorb the second harmonic,
Dielectric multilayer film that can reflect only waves (for example, TiO 2₂/ SiO ₂
Etc.). Dielectric multilayer film is sputtered or
It can be easily formed by the electron beam evaporation method.

A further different embodiment of the second harmonic generator of the present invention will be described with reference to FIG. In the figure, 24
Is an AlGaAs semiconductor laser, 25 is a phase matching layer, 26 is a distributed Bragg reflector which is a third reflecting mirror, and 27 is a distributed Bragg reflector which is a fourth reflecting mirror. The embodiment shown in FIG. 4 is different from the embodiment shown in FIG. 1 in that the distribution Bragg is formed on the end face of the AlGaAs semiconductor laser 24 opposite to the light emission end face and on the second harmonic emission face of the phase matching layer 25. Reflector 2
6 and 27 are formed. In this embodiment, the two distributed Bragg reflectors 26 and 27 are both formed of a dielectric multi-layer film (for example, TiO ₂ / SiO ₂ etc.), and the dielectric multi-layer film has a relatively high number of layers. There is an advantage that the reflectance can be realized. Further, between the AlGaAs-based semiconductor laser 24 and the phase matching layer 25 of the embodiment shown in FIG. 4, further, Al _z Ga
_1-z As / Al _v Ga _1-v As A distributed Bragg reflector composed of compound semiconductor multilayer film is introduced, and the fundamental wave is reflected between the distributed Bragg reflector and the distributed Bragg reflector 26 to achieve more phase matching. It may be configured to increase the power of the fundamental wave in the layer 25.

A further different embodiment of the second harmonic generation device of the present invention will be described with reference to FIG. In the figure, 28
Is a GaAs substrate, 29 is AlGaAs formed on the GaAs substrate 28
System semiconductor laser, 30 is a phase matching layer formed on the light emitting end face of the AlGaAs system semiconductor laser 29, 31 is a wavelength tunable portion having a semiconductor laser structure similar to that of the AlGaAs system semiconductor laser 15, and 32 is the AlGaAs system semiconductor laser 29. Is a front surface side electrode, 33 is a front surface side electrode of the phase matching layer 30, and 34 is a substrate electrode formed on the back surface of the GaAs substrate 28. In the embodiment shown in FIG. 5, two semiconductor laser structures of the AlGaAs semiconductor laser 29 and the wavelength variable portion 31 are thus formed, and one of the semiconductor laser structures (AlGaAs semiconductor laser 29) is used for laser driving. A current required for laser oscillation is passed, and the other (wavelength tuning unit 31) is operated for wavelength tuning. This is because the phase matching layer 30 is composed of a multi-layered film, and if the film thickness deviates from the design value, the efficiency of second harmonic generation decreases, so that the semiconductor laser structure is separated by a groove, C ³ (Cleaved This is because the oscillation wavelength of the laser is scanned by the Coupled Cavity type laser structure to increase the coupling strength of light with the phase matching layer 30 and generate a highly efficient second harmonic.

In order to form the structure of the embodiment shown in FIG. 5, for example, after providing a front surface side electrode in one semiconductor laser structure, a groove 35 is formed by etching to form a plurality of semiconductor laser structures. Just divide it. In the embodiment shown in FIG. 5, one semiconductor laser structure is divided into
The system semiconductor laser 29 and the wavelength variable portion 31 are formed.

Further, as shown in FIG. 6, one semiconductor laser structure is further added to the embodiment shown in FIG.
The semiconductor laser structure is a distributed Bragg reflection type laser structure, and the distributed Bragg reflection type laser structure 36, the wavelength tunable portion 31, and the AlGaAs semiconductor laser 29 are provided in the groove 3 respectively.
They may be formed so as to be adjacent to each other via 7, 35. With such a configuration, the oscillation wavelength of the laser can be adjusted by the distributed Bragg reflection type laser structure 36, and the oscillation wavelength of the laser can be finely adjusted by the wavelength tunable unit 31, thus increasing the tunable range of the oscillation wavelength. Therefore, the manufacturing accuracy of the phase matching layer 30 can be relaxed.

A further different embodiment of the second harmonic generator of the present invention will be described with reference to FIG. The embodiment shown in FIG. 7 is different from the embodiment shown in FIG. 2 in that a light extraction reflecting mirror is formed by a 45 degree etching at a position apart from the phase matching layer by a predetermined distance to produce a surface-emitting second harmonic wave. The wave layer device is configured. In the figure, 38 is a GaAs substrate, 39 is Al
GaAs semiconductor laser, 40 is a phase matching layer, and 41 is a light extraction reflector. The light extraction reflecting mirror 41 is formed on the GaAs substrate 38 at a position facing the second harmonic emission surface 40a of the phase matching layer 40, and faces the second harmonic emission surface 40a of the phase matching layer 40. The surface (reflection surface 41a) is
It is formed so as to form an angle of about 45 degrees with respect to the second harmonic emission surface 40a. With this configuration, the light output from the second harmonic wave emitting surface 40a of the phase matching layer 40 can be reflected in the surface direction by the reflecting surface 41a. The reflective surface 41a is formed by RIE from an oblique direction of 45 degrees or
It can be easily formed by RIBE.

A further different embodiment of the second harmonic generator of the present invention will be described with reference to FIG. In the figure, 42
Is a GaAs substrate, 43 is an AlGaAs semiconductor laser, 44 is a phase matching layer, 45 is a light extraction reflecting mirror, 45a is a reflecting surface, 4
5b is an AlGaAs liquid crystal layer. The embodiment shown in FIG. 8 differs from the embodiment shown in FIG. 7 in that AlAs / GaA or Al _z Ga _1-z As / Al _{v is used} as a guide layer sandwiching an active layer of a semiconductor laser.
Points using Ga _1-v As superlattice structure and reflective surface 45a formed by 45 degree oblique etching (45 degree etching mirror)
The point is that silicon ions are locally and periodically implanted by a focused ion beam at a predetermined position on the upper portion and heat treatment is performed to form a periodic structure of the AlGaAs liquid crystal layer 45b.
By thus periodically forming the AlGaAs liquid crystal layer 45b, a grating structure can be formed on the reflecting surface 45a, and a so-called external resonator structure (structure in which the grating structure is provided outside the laser oscillation portion) is formed. be able to. Forming the external resonator structure in this way and providing a distance between the laser oscillation portion and the grating structure has the effect of stabilizing the oscillation wavelength. Furthermore, by separating the laser oscillation part and the grating structure, mutual thermal influences can be reduced,
It is possible to stabilize the oscillation wavelength of the semiconductor laser.

In the case of the embodiment shown in FIG. 8, when the AlGaAs semiconductor laser 43 is formed by, for example, epitaxial growth, a portion to be a light extraction reflection mirror is also formed at the same time, and the reflection surface 45a (45) is formed by 45 ° oblique etching. Then, the AlGaAs liquid crystal layer 45b may be formed by further forming an etching mirror) and then implanting silicon on the reflecting surface 45a with a focused ion beam to perform heat treatment. The thickness of each layer of the superlattice structure may be about several nm to several tens of nm. Since the grating structure has wavelength selectivity, the wavelength width of the fundamental wave incident on the phase matching layer 44 is limited before being converted into the second harmonic by the phase matching layer 44. The phase matching layer 44 can greatly improve the conversion efficiency of converting the fundamental wave into the second harmonic.
Furthermore, an external resonator structure is used, and the grating structure is AlGa
The temperature dependence of the second harmonic can be reduced by arranging the semiconductor laser 43 separately from the As semiconductor laser 43 so as to reduce mutual thermal influences and generate a more stable second harmonic. be able to.

A further different embodiment of the second harmonic generator of the present invention will be described with reference to FIG. The embodiment shown in FIG. 9 corresponds to the embodiment shown in FIG. 8 in which electrodes are formed on the upper and lower parts of the light extraction reflecting mirror. In the figure, 46 is a GaAs substrate, 47 is an AlGaAs semiconductor laser, 4
8 is a phase matching layer, 49 is a light extraction reflecting mirror, 49a is a reflecting surface, 49b is an AlGaAs liquid crystal layer, 50 is a surface side electrode of the AlGaAs semiconductor laser 47, 51 is an electrode formed on the light extraction reflecting mirror 49, Reference numeral 52 is a substrate electrode (an electrode on the lower side of the light extraction reflecting mirror 49) formed on the back surface of the GaAs substrate 46. With this configuration, the electrode 51 and the substrate electrode 5
By applying a voltage between the two, a current is injected or an electric field is applied inside the light extraction reflecting mirror 49, and the refractive index of the grating structure is changed to scan the wavelength selectivity of the grating structure. . Thereby, the wavelength coupling between the AlGaAs semiconductor laser 47 and the phase matching layer 48 can be performed more easily.

An embodiment of the method for manufacturing the second harmonic generation device of the present invention will be described with reference to FIGS. FIG. 10 is a perspective view showing a second harmonic generation device formed by the method, and FIG. 11 is a sectional view showing a manufacturing process. In the embodiment shown in FIG. 1, the phase matching layer is described as being formed by crystal growth by MOVPE or MBE. However, the manufacturing method shown in FIG. 11 does not use the phase matching layer as an epitaxial layer but a semiconductor laser structure. Is formed by an ion implantation process or a focused ion beam implantation process and a heat treatment process. That is, a semiconductor laser structure similar to the semiconductor laser structure shown in FIG. 8 is formed,
At the position where the phase matching layer of this semiconductor laser structure is to be formed, silicon ions are locally and periodically implanted in a direction parallel to the light emitting end face of the semiconductor laser by ion implantation or a focused ion beam, and heat treatment is applied. AlGaAs
Is locally mixed to form a phase-matching layer, and the second harmonic generation device is constituted by a boundary as in the embodiment shown in FIG.

First, the structure of the second harmonic generation device will be described with reference to FIG. In the figure, 53 is a GaAs substrate and 54 is Ga.
The AlGaAs semiconductor laser 55 formed on the As substrate 53,
This is a phase matching layer formed on the light emitting end face of the AlGaAs semiconductor laser 54.

Next, the manufacturing method will be described in detail with reference to FIG.
explain. In the figure, first, as shown in (a), GaAs substrate
MOVPE or MBE on GaAs / AlGaAs semiconductor layer
An epitaxial film 54 for the z is grown. At this time,
As the semiconductor laser structure, the cladding layer 54 is formed from the substrate side.
a, the guide layer 54b, the active layer 54c, the guide layer 54d,
The clad layer 54e is sequentially grown. Where the guide layer
54b and 54d are replaced with Al_zGa_1-zAs / Al_vGa_1-vAs super lattice
Structure (each layer thickness is several nm to several tens nm) or GaAs / AlAs superlattice
The structure (each layer thickness is several nm) is set. After that, shown in (b)
As shown in FIG.
Locally and periodically at the point where the phase matching layer of
By implanting silicon and applying heat treatment, Al_zGa_1-z
As / Al_vGa _1-vAs superlattice or GaAs / AlAs superlattice
Al at the place where the recon was driven_zGa _1-zAs / Al_vGa_1-v
The superlattice structure collapses with As or GaAs / AlAs, resulting in mixed crystals, and AlGa
It will be formed as As. As a result, as shown in (c)
The mixed crystal AlGaAs layer 55a and the laser structure layer 5
5b is an epitaxy for GaAs / AlGaAs semiconductor laser
Structure in which layers are alternately formed on the light emitting end surface of the film 54.
Becomes This allows the semiconductor laser to be positioned on the light emitting end face.
A structure having a phase matching layer can be formed.

Next, one embodiment of a method of manufacturing the second harmonic generation device of the embodiment shown in FIG. 9 will be described with reference to FIG. However, the same components as those shown in FIG. 9 are designated by the same reference numerals. First, as shown in (a),
An epitaxial film 56 for the AlGaAs semiconductor laser 47 is grown on the GaAs substrate 46 by MOVPE or MBE. Next, as shown in (b), a portion to be the phase matching layer 48 and a portion to be the light extraction reflecting mirror 49 are separated by etching on the GaAs substrate 46, and at the same time, the light extraction reflecting mirror 4 is formed.
The reflecting surface 49a of 9 is formed.

Next, as shown in (c), silicon ions are locally and periodically generated by a focused ion beam at the position where the phase matching layer of the epitaxial film 56 is to be formed, from below the surface of the epitaxial film 56. By implanting in the area that reaches the cladding layer and performing heat treatment, Al _z Ga _1-z As / Al _v
A Ga _1-v As superlattice or a GaAs / AlAs superlattice is used to form a periodically mixed AlGaAs layer 48a, and as shown in FIG.
It is possible to form a structure (phase matching layer 48) in which 8b and 8b are alternately formed on the light emitting end face of the epitaxial film 56 in layers. Further, as shown in (c), a portion of the reflection surface 49a (45-degree etching mirror) of the light extraction reflecting mirror 49 is locally and periodically implanted with silicon ions by a focused ion beam to perform heat treatment, (D)
As shown in, the AlGaAs liquid crystal layer 49b is formed on the reflection surface 49a. Further, as shown in (e), the upper surface of the AlGaAs semiconductor laser 47, the upper surface of the light extraction reflecting mirror 49, the Ga
The front surface side electrode 50 and the electrode 5 are provided on the rear surface of the As substrate 46, respectively.
1. Form the substrate electrode 52.

A further different embodiment of the method for manufacturing the second harmonic generation device of the present invention will be described with reference to FIG.
The manufacturing method shown in FIG. 13 is a method of forming a phase matching layer by locally and periodically etching the position where the phase matching layer is formed to periodically form grooves parallel to the light emitting end face of the semiconductor laser. Is. First, the semiconductor laser structure 58 is formed on the GaAs substrate 57 by epitaxial growth, and then, in order to periodically form the grooves 59a parallel to the light emitting end face of the semiconductor laser at predetermined positions of the phase matching layer 59, a photo mask is formed. By carrying out a step or an electron beam exposure step, an etching pattern is formed on the upper surface of the portion to be the phase matching layer. Next, by RIE or RIBE, the cladding layer 5 on the substrate side of the semiconductor laser structure 58 from the upper surface of the portion to be the phase matching layer.
The phase matching layer 59 is formed by etching up to around 8a and forming a groove 59a. Although phase matching is possible even in the state shown in FIG. 13, in order to prevent the film from being oxidized, an insulating film or a semiconductor film may be embedded in the groove 59a thereafter.

In the above, the embodiments have been described using III-V group compound semiconductors, particularly AlGaAs semiconductors, but the present invention is not particularly limited to materials, and InGa
It is also applicable to other III-V group compound semiconductors such as AsP and AlGaInP, or II-VI group compound semiconductors such as ZnSSe or ZnCdSSe.

[0048]

According to the second harmonic generation device of the first to eighth aspects, the phase matching layer is provided on the light emitting end face of the semiconductor laser by using the conventional semiconductor technology, so that it is small and high. It is possible to provide a low-cost second harmonic generation device with high efficiency and high output.

According to the second and third harmonic generators of the second and third aspects, a high output second harmonic generator is realized by having a structure in which the phase matching layer is sandwiched by distributed Bragg reflectors. can do.

According to the second harmonic generation device of the fourth and fifth aspects, a plurality of semiconductor laser structures are formed by etching or cleavage, and a part of the semiconductor laser structures is used as a wavelength tunable portion to form a semiconductor. Scan the oscillation wavelength of the laser to increase the coupling strength of light with the phase matching layer,
It is possible to generate a highly efficient second harmonic.

According to the second harmonic generation device of the sixth aspect, since the semiconductor laser, the phase matching layer and the light extraction reflecting mirror are formed on the same substrate, very complicated adjustment such as optical axis alignment is performed. Since it is unnecessary, it is possible to realize a surface emitting type second harmonic generation device that can further reduce the manufacturing cost.

According to the second harmonic generation device of the seventh aspect, in the second harmonic generation device of the sixth aspect, a predetermined refractive index distribution structure, a so-called grating structure, is formed on the reflecting surface to external resonance. Since the container structure is formed, the oscillation wavelength of the semiconductor laser can be stabilized. Further, since it is not necessary to adjust the angle adjustment of the grating structure, it is possible to further reduce the manufacturing cost.

The second harmonic generation device according to claim 8 is the second harmonic generation device according to claim 7, wherein the refractive index distribution of the reflecting surface of the light extraction reflecting mirror can be changed.
The wavelength can be selected in the grating structure, and the efficiency of second harmonic generation in the phase matching layer can be greatly improved.

According to the manufacturing method of the second harmonic generation device of the ninth to twelfth aspects, the phase matching layer of the second harmonic generation device of the first to eighth aspects can be easily formed. It is possible to provide a small-sized, high-efficiency, high-output, low-cost second harmonic generation device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a second harmonic generation device of the present invention.

FIG. 2 is a perspective view showing another embodiment of the second harmonic generation device of the present invention.

FIG. 3 is a perspective view showing still another embodiment of the second harmonic generation device of the present invention.

FIG. 4 is a perspective view showing a further different embodiment of the second harmonic generation device of the present invention.

FIG. 5 is a perspective view showing still another embodiment of the second harmonic generation device of the present invention.

FIG. 6 is a perspective view showing still another embodiment of the second harmonic generation device of the present invention.

FIG. 7 is a perspective view showing a further different embodiment of the second harmonic generation device of the present invention.

FIG. 8 is a perspective view showing still another embodiment of the second harmonic generation device of the present invention.

FIG. 9 is a perspective view showing still another embodiment of the second harmonic generation device of the present invention.

FIG. 10 is a perspective view showing a different embodiment of the method for manufacturing the second harmonic generation device of the present invention.

FIG. 11 is a cross-sectional view showing still another embodiment of the method of manufacturing the second harmonic generation device of the present invention.

FIG. 12 is a cross-sectional view showing still another embodiment of the method for manufacturing the second harmonic generation device of the present invention.

FIG. 13 is a perspective view showing still another embodiment of the method for manufacturing the second harmonic generation device of the present invention.

FIG. 14 is a configuration diagram showing an example of a conventional second harmonic generation device.

FIG. 15 is a sectional view showing a different example of a conventional second harmonic generation device.

[Explanation of symbols]

15, 18, 20, 24, 29 AlGaAs semiconductor laser (semiconductor laser) 39, 43, 47, 54 AlGaAs semiconductor laser (semiconductor laser) 16, 19, 21, 25, 30 Phase matching layer 40, 44, 48, 55, 59 Phase matching layer 17, 28, 38, 42, 46 GaAs substrate (substrate) 53, 57 GaAs substrate (substrate) 22 Distributed Bragg reflector (first reflecting mirror) 23 Distributed Bragg reflector (second reflecting mirror) 26 distributed Bragg reflector (third reflective mirror) 27 distributed Bragg reflector (fourth reflective mirror) 35, 37, 59a groove 41, 45, 49 light extraction reflective mirror 41a, 45a, 49a reflective surface 51 electrode 52 substrate electrode ( electrode)

Claims (12)

[Claims] 1. A semiconductor laser, and a phase matching layer made of a compound semiconductor, which is formed on a light emitting end face of the semiconductor laser and has a periodic structure in which a refractive index changes periodically. Second harmonic generator. 2. A first reflecting mirror made of a multilayer film is formed between the semiconductor laser and the phase matching layer, and a second harmonic wave made of the multilayer film is transmitted on the second harmonic wave emission surface of the phase matching layer. The second harmonic generation device according to claim 1, wherein a second reflecting mirror is formed. 3. A third reflecting mirror formed of a multilayer film is formed on a surface of the semiconductor laser opposite to the light emitting end surface, and the third reflecting mirror is formed on the second harmonic emission surface of the phase matching layer. The second harmonic generation device according to claim 1, wherein a fourth reflecting mirror that transmits the second harmonic is formed. 4. The second harmonic generation device according to claim 1, wherein the semiconductor laser is separated into a plurality of semiconductor laser structures by grooves parallel to the light emitting end face. 5. The second harmonic generation device according to claim 4, wherein a part of the separated semiconductor laser structure has a distributed Bragg reflection type laser structure. 6. The second harmonic generation device according to claim 1 is formed on a substrate, and the reflection surface of the second harmonic generation surface of the phase matching layer is the second harmonic emission surface side. A surface emitting type second harmonic generation device, wherein a light extraction reflecting mirror is formed on the substrate so as to face the harmonic emission surface at an angle of about 45 degrees. 7. The second harmonic generation device according to claim 6, wherein a predetermined refractive index distribution structure is formed on the reflecting surface. 8. The second harmonic generation device according to claim 7, wherein electrodes are formed on an upper part and a lower part of the light extraction reflecting mirror. 9. The second harmonic generation device according to claim 1, wherein the phase matching layer is formed by a step including a crystal growth step on a light emitting surface of the semiconductor laser. Production method. 10. The second phase matching layer according to claim 1, wherein the phase matching layer is formed by a step including an ion or focused ion beam implantation step and a heat treatment step after the implantation step. Manufacturing method of harmonic generator. 11. The phase matching layer is formed by a step including an etching step of forming a groove by etching in parallel with the light emitting end surface of the semiconductor laser. Second harmonic generator manufacturing method. 12. The method of manufacturing a second harmonic generation device according to claim 11, wherein the phase matching layer is formed by a step including a step of burying an insulating film or a compound semiconductor in the groove.