JP3154244B2 - Semiconductor laser device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high performance semiconductor laser device required for optical fiber communication and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art The loss of a single mode optical fiber is 1.55μ.
m for light of m. However, the single-mode optical fiber for the 1.55 μm band has chromatic dispersion, and when the LD of the light source has a spectrum spread, the transmission band is significantly limited. For this reason, in a conventional semiconductor laser device, a dynamic single mode laser (DSM-LD) that maintains a single longitudinal mode operation even during high-speed direct modulation.
Has been proposed. In order to stably control the longitudinal mode, a distributed feedback (DFB) laser (for example, Nakamura et al., I.I.I.J. of Quantum)
Electronics IEEE J. Quantum Electron. QE-11,43
6 (1975)) and distributed reflection (DBR) lasers (for example,
Rainheart et al., Applied Physics Letter,
Appl. Phys. Lett., 27, 45 (1975)) and compound-cavity lasers (for example, Suematsu et al., Electronics Letter
Electron. Lett., 17,954 (1981)) and the like have attempted a single mode. Among them, DFB lasers have been studied more vigorously than ever since DFB lasers can stably provide high light output.

FIG. 6 shows the structure of a conventional DFB laser.
In FIG. 6, 1 is an n-InP substrate, 2 is a distributed feedback grating, 5 is an InGaAsP (λ = 1.3 μm) waveguide layer, 6 is an InGaAsP (λ = 1.55 μm) active layer,
7 is a pn-pInP buried layer, 8 is p-InGaAs
sP (λ = 1.3 μm) cap layer, 9 is Au / Zn p
A side electrode, 10 is an Au-Sn n-side electrode, 11 is a silicon oxide / amorphous silicon multilayer reflective film, and 12 is a silicon nitride non-reflective film. However, when there is no reflection at both ends of the diffraction grating, the DFB laser has two longitudinal modes symmetrically with respect to the Bragg wavelength determined from the period of the diffraction grating. Therefore, even if the Fabry-Perot oscillation can be suppressed, single-mode oscillation cannot be obtained because of oscillation at two wavelengths. To improve this, a DFB laser usually employs a structure in which one end uses a cleavage surface as a reflection surface to extract light, and the other end suppresses end surface reflectance in order to suppress Fabry-Perot mode oscillation. The mirror loss characteristic of a DFB laser having an asymmetric structure with end face reflection is asymmetric with respect to the Bragg wavelength, resulting in a difference in intensity ratio between the two longitudinal modes.

[0004]

However, in the above-mentioned conventional structure, firstly, at the end face of the reflector of the laser waveguide layer, the light density rapidly increases, so that the electron density decreases and the refractive index decreases. It has been reported that due to the axial hole burning, it is difficult to obtain single mode characteristics at high output (Koda et al., IEICE Technical Report, OQE-86-7, 49, 1986).
FIG. 7 shows the distribution of light intensity, electron density, and refractive index inside the laser resonator. The laser resonator has a reflection film 11 on the reflection end face,
An anti-reflection film 12 is coated on the emission end face. Since the light inside the resonator is reflected by the reflection film 11, the reflection film 1
The light intensity near 1 locally increases. At the position where the light intensity increases, the recombination of the electrons and the neutrons is promoted, and the electrons are depleted. Since the refractive index decreases due to the depletion of electrons, the gain and the oscillation wavelength fluctuate, and it becomes difficult to obtain stable single mode oscillation.

[0005] Second, since the reflection loss characteristic varies significantly depending on the position of the end face mirror on the grating, the intensity ratio between the two longitudinal modes depends on the period of the diffraction grating at the end face. FIG. 8 shows the relationship between the mode loss difference ΔA between the main mode having the lowest loss and the next submode and the phase θ at the end face reflection mirror of the end face diffraction grating. Thus, when the phase θ = π, the loss difference ΔA between the modes becomes 0 as in the case where there is no reflection at both end faces, and two longitudinal mode oscillations having the same output are generated. Since it is impossible to control the phase θ of the diffraction grating with a normal DFB laser, DFB oscillation in which two longitudinal modes exist at a fixed ratio is obtained, and the yield is significantly reduced.

In order to remove the instability of the single mode oscillation, the period of the diffraction grating at the center of the DFB laser is set to λ /
There are a method of making the Bragg wavelength and the longitudinal mode coincide with each other by four shifts (λ / 4 shift DFB-LD), and a method of giving an equivalent refractive index distribution symmetrical in the axial direction of the resonator. However, in either case, it is necessary to apply an anti-reflection coating to both end faces in order to eliminate the influence of the reflection on the end faces. Therefore, variations in device characteristics due to an increase in the number of processes and variations in coating conditions, and high reflection on one end face. There is a problem in that the output is reduced due to the light emission from both end faces with respect to the light emission from one end face provided with the film.

Further, there have been reported many techniques for changing the phase of the grating by λ / 4 inside the laser.
No attempt has been made to form a grating only partially in the state of θ = π / 2 inside the laser or to gradually reduce the amplitude of the grating in order to smoothly realize the state of θ = π / 2. SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a semiconductor laser device capable of obtaining stable single mode oscillation and obtaining a high optical output, and a method of manufacturing the same.

[0008]

According to a first aspect of the present invention, there is provided a semiconductor laser device comprising a laser resonator comprising an active layer and a waveguide layer formed on a semiconductor single crystal substrate and having a reflection end face and an emission end face. A device, comprising: a laser cavity having a laser cavity formed on a surface of the entire waveguide layer except for a reflection end surface of the laser cavity and a region having a length of about 50 μm in the vicinity thereof.
The amplitude gradually decreases from the launch end to the reflection end.
It provided with a diffraction grating so that, in the region of the reflecting end face and 50μm approximately the length of the vicinity of the waveguide layer surface is characterized in that not be provided a diffraction grating.

According to a second aspect of the present invention, there is provided a semiconductor laser device comprising a laser resonator comprising an active layer and a waveguide layer formed on a semiconductor single crystal substrate and having a reflection end face and an emission end face. On the surface of the waveguide layer except for the reflection end face of the resonator and the vicinity of a region having a length of about 30 μm , the reflection end face from the emission end face of the laser resonator is provided.
Provided with a diffraction grating so that the amplitude gradually decreases toward a surface direction, the area of the reflective facet and 30μm approximately the length of the neighborhood of the waveguide layer surface and characterized in that so as not provided diffraction grating I do. The semiconductor laser device according to claim 3, comprising a laser resonator comprising an active layer and a waveguide layer formed on a semiconductor single crystal substrate and having a reflection end face and an emission end face,
Laser resonance is applied to the entire surface of the waveguide layer excluding the reflection end face of the laser resonator and the area of about 10 μm in the vicinity thereof.
The amplitude gradually decreases from the exit end face of the device to the reflection end face.
Provided with a diffraction grating so that fence, the areas of the reflective facet and 10μm approximately the length of the proximity of the waveguide layer surface is characterized in that not be provided a diffraction grating.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor laser device, comprising: a first crystal growing step of growing a crystal having a composition different from that of a substrate on a semiconductor single crystal substrate; An etching step of etching away portions that constitute the stripes, and applying a resist over the entire surface of the substrate and the crystals left in a stripe shape so that the thickness gradually increases from the emission end face to the reflection end face direction of the laser resonator. Then, a diffraction grating is drawn on the resist by a two-interference exposure method, and a diffraction grating forming step of transferring the diffraction grating to the substrate and the crystal by etching, and a second crystal growth step of growing the crystal again on the diffraction grating are performed. Contains.

[0011]

According to the first to third aspects of the present invention, since no diffraction grating is formed near the reflection end face, it is possible to prevent an increase in light density due to distributed feedback in addition to an increase in light density at end face reflection. In the case of the DFB laser, the influence of the end face reflection and the feedback of the diffraction grating on the light intensity inside the resonator can be considered as the sum of the respective effects. Near the reflection end face in the resonator, the light intensity increases due to the reflection of light on the end face. Therefore, by forming no diffraction grating in this portion, the feedback effect is eliminated and the concentration of light intensity is reduced. Further, by considering the phase of the diffraction grating, a more stable single mode oscillation can be realized. That is, since no diffraction grating is present in the laser reflecting mirror, the phase of the diffraction grating in the reflecting mirror is approximated to zero. On the other hand, the phase of the diffraction grating at the end surface coated with anti-reflection, which is the light emission surface, has a value very close to 0 because it has no meaning. As a result, the phase difference at the end face becomes zero, and a stable and constant inter-mode loss difference is obtained. in this case,
Side mode is not the most suppressed state,
By optimizing the reflection efficiency on the reflection surface, the set value of the side mode suppression ratio of 30 dB or more can be cleared. In this case, the suppression ratio of 30 dB or more is similarly stably obtained in all the laser chips, so that the yield is dramatically improved.

[0012] Note that, by reducing gradually toward the reflecting end face direction the amplitude of the diffraction grating from the emission end face of the laser resonator, it is possible to gradually decrease the change in refractive index by the diffraction grating, greatly improves the loss difference between the modes be able to. If there is no diffraction grating at the position of the reflector, the relationship with the phase of the electromagnetic field at the position of the reflector becomes important. If the distance between the end of the diffraction grating and the reflecting mirror is extremely short, the phase of the electromagnetic field at the interface is obtained by extrapolating the phase of the diffraction grating to the position of the reflecting mirror. However, the phase of the electromagnetic field shifts from the phase induced by the diffraction grating to the phase that improves the gain at the end face as the end of the reflection mirror and the diffraction grating are separated. The effect of this shift increases when the amplitude of the diffraction grating gradually changes to enable coupling. As a result, the phase of the electromagnetic field at the position of the reflector is λ
As in the case of the / 4 shift, the loss difference between the modes gradually approaches 0, and stably increases.

[0013]

According to a fourth aspect of the present invention, a stripe-shaped crystal having the same composition as that of the waveguide layer is formed, and the thickness of the crystal is gradually changed by using the stripe. By applying a resist and forming a diffraction grating, it is possible to continuously form a region where the amplitude of the diffraction grating decreases as approaching the reflection end face and disappears when the phase θ = 0. As a result, the electromagnetic field is easily recombined with the diffraction grating in the state of the phase θ = 0, so that a high inter-mode loss difference is obtained.

[0015]

FIG. 1 is a block diagram showing a semiconductor laser device according to a first embodiment of the present invention. In FIG. 1, 1 is an n-InP substrate (semiconductor single crystal substrate), 2 is a distributed feedback grating (diffraction grating),
4 is a flat surface on which no grating exists, 5 is InGa
AsP (λ = 1.3 μm) waveguide layer, 6 is InGaAsP
(Λ = 1.55 μm) active layer, 7 is a pn-pInP buried layer, 8 is a p-InGaAsP (λ = 1.3 μm) cap layer, 9 is a p-side electrode of Au / Zn, and 10 is n of Au-Sn. The side electrode, 11 is a silicon oxide / amorphous silicon multilayer reflection film, and 12 is a silicon nitride anti-reflection film having a film thickness of λ / 4.

The operation of the semiconductor laser device according to this embodiment having the above-described structure will be described below. The current is supplied from the Au / Zn p-side electrode 9 and the buried layer 7
After that, it is injected into the active layer 6. Active layer 6
The light generated in step (1) seeps into the waveguide layer 5, and light having a wavelength determined by the period of the grating 2 oscillates. Since no grating exists near the end face where the reflection film 11 is formed on the waveguide layer, there is no feedback of light due to the grating, so that the optical gain is reduced and the increase in light intensity due to reflection on the end face can be canceled.

The light intensity inside the laser resonator of this embodiment,
FIG. 2 shows the distribution of the electron density and the refractive index. This indicates that the light intensity distribution inside the resonator is extremely flattened and the change in the refractive index is small. As a result of measuring the injection current dependency of the laser oscillation wavelength, the conventional 0.1 nm / mA was reduced to 0.045 nm / mA or less, and the chirping amount was increased from 3 MHz to 900 KH.
z. On the other hand, since no grating exists on the end face of the reflecting mirror, the phase of the grating is approximated to 0. On the other hand, the phase of the grating on the non-reflection coated end surface, which is the light emission surface, has a value very close to 0 because it has no meaning. As a result, the phase difference at the end face becomes zero, and a stable and constant inter-mode loss difference is obtained.

In this embodiment, the side mode is not in the state of being suppressed to the maximum, but by optimizing the reflection efficiency on the reflecting surface, the conventional side mode suppression ratio becomes 30%.
The characteristic was suppressed to about 40 dB, which is about 1.3 times that of the dB. In this case, since the phase difference of the reflection end face is constant for all the laser chips, the suppression of the side mode is similarly stabilized in all the laser chips, and the suppression ratio of 40 dB or more is obtained, thereby improving the yield.

[Second Embodiment] FIG. 3 shows a configuration diagram of a semiconductor laser device according to a second embodiment of the present invention. In FIG. 3, 1 is an n-InP substrate, 2 is a distributed feedback grating, 3 is a region where the amplitude of the grating 2 is gradually reduced, 4 is a flat surface having no grating,
5 is an InGaAsP (λ = 1.3 μm) waveguide layer, 6 is I
nGaAsP (λ = 1.55 μm) active layer, 7 is pnp
InP buried layer 8 is p-InGaAsP (λ = 1.3
μm) cap layer, 9 is an Au / Zn p-side electrode, 10 is an Au-Sn n-side electrode, 11 is a silicon oxide / amorphous silicon multilayer reflective film, and 12 is a λ / 4 silicon nitride non-reflective film. It is.

The operation of the semiconductor laser device according to this embodiment having the above-described configuration will be described below. The current is supplied from the Au / Zn p-side electrode 9 and the buried layer 7
After that, it is injected into the active layer 6. Active layer 6
The light generated in step (1) seeps into the waveguide layer 5, and light having a wavelength determined by the period of the grating 2 oscillates. Inside the resonator, a change in the thickness of the waveguide layer 5 due to the diffraction grating induces a change in the refractive index of the entire waveguide mode, and the effective refractive index inside the active layer 6 is distributed according to the shape of the grating 2. Since light having a wavelength corresponding to the period of change in the effective refractive index inside the active layer 6 is fed back and amplified, light having a specific wavelength oscillates selectively.

However, in the case of the distributed feedback type, since the phase of the grating 2 does not match the phases of the traveling wave and the backward wave, two modes sandwiching the Bragg wavelength may oscillate simultaneously. This probability is reflected on the laser end face-
Although it is reduced by applying the anti-reflection coating, the possibility of simultaneous oscillation of the two modes remains depending on the state of the phase of the grating on the reflection end face.

The semiconductor laser of this embodiment has a region 3 in which the amplitude of the grating 2 gradually decreases over 20 μm at the reflection end face, and a flat surface 4 of 50 μm (length of about 32 wavelengths) . In the case where no grating exists at the position of the reflecting mirror and the distance between the end of the grating 2 and the reflecting mirror is extremely short, the phase of the electromagnetic field at the interface is obtained by extrapolating the phase of the grating 2 to the position of the reflecting mirror. . However, the end of the reflector and the grating 2 is 50 μm.
m, and when the amplitude of the grating 2 gradually increases and coupling becomes possible, the phase of the electromagnetic field may shift from the phase induced by the grating 2 to the phase that improves the gain at the end face. It becomes possible.
As a result, the phase of the electromagnetic field at the position of the reflecting mirror asymptotically approaches θ = 0 as in the case of the λ / 4 shift, the loss difference between the modes increases steadily, and is caused by the period at the reflecting end face of the grating 2. It was possible to eliminate the instability of the oscillation mode.

In this embodiment, the characteristic is 53 dB, which is about 1.7 dB, compared to the conventional side mode suppression ratio of about 30 dB.
It was suppressed twice. In this case, θ = 0 was realized for all the laser chips, and a suppression ratio of 50 dB or more was obtained stably, thereby significantly improving the yield. One
Next, a semiconductor laser device similar to that of the second embodiment is manufactured.
An example of the method of manufacturing will be described with reference to FIG.
I will tell. FIG. 4 shows an example of a method for manufacturing a semiconductor laser device similar to that of the second embodiment .

In FIG. 4, first, in the first epitaxial growth, n-InGaAsP is formed on the n-InP substrate 1.
(Crystal) The grating stop layer 13 has a thickness of 50 nm and n
After growing the InGaAs selective etching layer 16 to a thickness of 20 nm, surface treatment is performed with a solution of sulfuric acid: aqueous hydrogen peroxide: water = 1: 1: 500. Thereafter, a 10 μm striped oxide film 17 is formed from the position to be the laser end face, and the selective etching layer 16 and the grating stop layer 13 are partially etched away with a sulfuric acid-based etching solution so as to leave the striped portion. 4 (a) is obtained. Here, the sulfuric acid-based etching solution is sulfuric acid: hydrogen peroxide solution: water =
By setting the ratio to 1: 1: 300, InGaAs / InGa
AsP etching rate ratio = 100,
An etching region having a gradient of about 1/100 can be formed at 20 μm.

Next, after the oxide film 17 is entirely removed, the whole is etched with a solution of sulfuric acid: hydrogen peroxide solution: water = 1: 1: 200 to remove the n-InGaAs selective etching layer 16. Thereafter, a grating 2 is formed on the entire surface by holographic exposure to obtain the structure shown in FIG. Next, an n-InGaAsP (crystal) waveguide layer 5 is formed on the entire surface to a thickness of 0.1 mm.
15 μm, 0.1 μm of InGaAsP active layer 6, p-In
The structure of FIG. 4C is obtained by growing the P cladding layer 14 by 0.5 μm. Here, since the grating stop layer 13 is integrated with the optical waveguide layer 5, the grating stop layer 13 has a grating region 3 where the amplitude is gradually reduced and a flat surface 4 where no grating is present below. Since the flat surface 4 is not etched, the phase becomes θ = π / 2.

Next, the cladding layer 14, the active layer 6, the optical waveguide layer 5, and a part of the substrate 1 are spread over a width of 1 μm.
After forming the stripe 15 by etching in the direction,
p-InP layer, n-InP layer, p-InP layer 7 and p
-Grow an InGaAsP cap layer 8 and then Au
/ Zn p-side electrode 9 and Au-Sn n-side electrode 10 are formed by vapor deposition and have a film thickness of λ / 4 as an anti-reflection coating.
The silicon nitride non-reflective film 12 and the multilayer reflective film 11 of a silicon oxide film and an amorphous silicon film as a reflective coating are deposited to obtain the structure shown in FIG.

In this embodiment, in order to obtain a grating transition region 3 in which the amplitude gradually decreases, the grating stop layer 13 having the same composition as the waveguide layer 5 and the n-In
By utilizing the difference in the etching rate ratio of the GaAs selective etching layer 16, 1 /
It is characterized in that it is only necessary to form an inclined plane of 100 μm 20 μm and a flat plane 30 μm partially, and to form the grating 2 over the entire crystal surface. In this case, unlike the case where the light distribution is modulated by a hologram or the like to produce a flat surface, the grating 2 which does not affect the phase and has a gradually decreasing amplitude over a wide range using the conventional technique is easily formed. It becomes possible. In this case,
The flat surface 4 without the ring 2 is 30 μm (about 19 waves).
Length).

Third Embodiment FIG. 5 shows a method of manufacturing a semiconductor laser device according to a third embodiment of the present invention. In FIG. 5, first, n is grown on the n-InP substrate 1 in the first epitaxy growth.
1 μm of the InGaAsP grating stop layer 13
After the growth of the grating stop layer 13 with a sulfuric acid-based etching solution, leaving a 10 μm stripe from the end face.
Is partially removed by etching. Next, resist 1 on the entire surface
By coating 8 of about 3 μm, a resist structure whose thickness gradually changes in the vicinity of the stripe is obtained, and FIG. 5A is obtained.

Next, by forming the grating 2 on the entire surface by the holographic exposure method, the grating 2 is formed on the substrate 1 in a portion where the film thickness of the resist 18 is small, but the resist 18 becomes gradually thick near the stripe. The depth of the grating 2 becomes shallower in accordance with the thickness of the resist 18, and the structure shown in FIG. Next, n-In
The GaAsP optical waveguide layer 5 is 0.15 μm, the InGaAsP active layer 6 is 0.1 μm, and the p-InP cladding layer 14 is 0.5 μm.
As a result, a region 3 where the amplitude of the grating is gradually reduced and a flat surface 4 where no grating is present are obtained.
The structure of (c) is obtained. Here, the grating stop layer 13 has a lower portion of about 10 μm (about
Flat surface 4 without grating having length of 6 wavelengths)
Will be provided. Since the flat surface 4 is not etched, the phase becomes θ = π / 2.

Next, the cladding layer 14, the active layer 6, the optical waveguide layer 5 and a part of the substrate 1 are spread over a width of 1 μm.
After forming the stripe 15 by etching in the direction,
p-InP layer, n-InP layer, p-InP layer 7, nI
An nGaAs layer 8 is grown, and then a Au / Zn p-side electrode 9 and an Au-Sn n-side electrode 10 are formed by vapor deposition.
A silicon nitride antireflection film 12 having a film thickness of λ / 4 is deposited as a nonreflection coating, and a multilayer reflection film 11 of a silicon oxide film and an amorphous silicon film is deposited as a reflection coating to obtain a structure shown in FIG.

In this embodiment, in order to obtain a flat surface 4 having a phase of θ = π / 2, a grating stop layer 13 having the same composition as the waveguide layer 5 is formed partially.
The feature is that only the grating 2 needs to be formed on the entire surface of the crystal. In this case, unlike the case where the light distribution is modulated by a hologram or the like to produce a flat surface, the phase is not affected, and the grating 2 can be formed over a wide range using the conventional technology.

In the first to third embodiments,
Although the position of the grating 2 is below the active layer 6, it may be formed above the active layer 6. Further, the multilayer reflective film 11
Although the silicon oxide / amorphous silicon multilayer film and the antireflection film 12 are silicon nitride films, the multilayer reflection film 11 and the antireflection film 12 are not limited to this material. Further, although the InP substrate 1 is used as the semiconductor crystal substrate, another semiconductor crystal substrate such as GaAs may be used.

In the embodiment, the waveguide layer 5 and the active layer 6 are adjacent to each other, but this is not a limitation. In the third embodiment, the etching solution is a sulfuric acid-based solution, but another selective etching solution may be used. In the third embodiment, the thickness of the resist 18 is 3 μm. However, the thickness is not limited as long as the thickness of the resist 18 can be changed.

[0034]

As described above, according to the present invention, a large single mode suppression ratio can be obtained, a stable single mode oscillation can be obtained, and a high output can be achieved by applying a one-side reflection coating. In particular, by gradually changing the depth in the coupling region of the diffraction grating, it is possible to realize a semiconductor laser device having an improved side mode suppression ratio due to the λ / 4 shift effect. Have.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a distribution diagram of light intensity, electron density, and refractive index in the example.

FIG. 3 is a structural view of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 4 is a process chart showing an example of a method for manufacturing a semiconductor laser device according to a second embodiment of the present invention.

FIG. 5 is a process chart showing a method for manufacturing a semiconductor laser device according to a third embodiment of the present invention.

FIG. 6 is a structural diagram of a conventional DFB laser.

FIG. 7 is a distribution diagram of light intensity, electron density, and refractive index inside a laser resonator of a conventional DFB laser.

FIG. 8 is a diagram illustrating a relationship between a loss difference between modes and a phase.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 n-InP substrate (single crystal semiconductor substrate) 2 distributed feedback grating (diffraction grating) 3 region where the amplitude of grating is gradually reduced 4 flat surface where no grating exists 5 n-InGaAsP (crystal) waveguide layer 6 InGaAsP active layer 13 n-InGaAsP (crystal) grating stop layer 18 resist

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Yasushi Matsui 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-287187 (JP, A) JP-A-2-2 280394 (JP, A) JP-A-62-219684 (JP, A) Japanese Translation of PCT International Publication No. 4-505687 (JP, A) WO 90/12436 (WO, A1)

Claims (4)

(57) [Claims] 1. A semiconductor laser device comprising a laser resonator comprising an active layer and a waveguide layer formed on a semiconductor single crystal substrate and having a reflection end face and an emission end face, wherein the reflection end face of the laser resonator and the reflection end face thereof are provided. Near 50 μm
Said waveguide layer all surfaces except the region of the extent of the length, before
The oscillation from the emission end face to the reflection end face of the laser cavity
A diffraction grating is provided so that the width is gradually reduced, and no diffraction grating is provided on the reflection end face and the vicinity of the area having a length of about 50 μm on the waveguide layer surface.
A semiconductor laser device characterized by doing so . 2. A semiconductor laser device comprising: a laser resonator comprising an active layer and a waveguide layer formed on a semiconductor single crystal substrate and having a reflection end face and an emission end face, wherein the reflection end face of the laser resonator and the reflection end face thereof are provided. Nearby 30μm
Said waveguide layer all surfaces except the region of the extent of the length, before
The oscillation from the emission end face to the reflection end face of the laser cavity
A diffraction grating is provided so that the width becomes gradually smaller, and no diffraction grating is provided on the reflection end face and the vicinity of the area having a length of about 30 μm on the surface of the waveguide layer.
A semiconductor laser device characterized by doing so . 3. A semiconductor laser device comprising a laser resonator comprising an active layer and a waveguide layer formed on a semiconductor single crystal substrate and having a reflection end face and an emission end face, wherein the reflection end face of the laser resonator and the reflection end face thereof are provided. Nearby 10 μm
Said waveguide layer all surfaces except the region of the extent of the length, before
The oscillation from the emission end face to the reflection end face of the laser cavity
A diffraction grating is provided so that the width is gradually reduced, and no diffraction grating is provided on the reflection end face and a region of about 10 μm in the vicinity thereof on the waveguide layer surface.
A semiconductor laser device characterized by doing so . 4. A first crystal growth step of growing a crystal having a composition different from that of the substrate on a semiconductor single crystal substrate, and leaving a portion of the crystal forming a reflection end face of a laser resonator and its vicinity in a stripe shape. An etching step of removing the etching so as to apply a resist over the entire surface of the crystal remaining in the substrate and the stripe so that the thickness gradually increases from the emission end face to the reflection end face direction of the laser resonator, and on the resist. 2. A semiconductor, comprising: a diffraction grating forming step of drawing a diffraction grating by an interference exposure method and transferring the diffraction grating to the substrate and the crystal by etching; and a second crystal growth step of growing the crystal again on the diffraction grating. A method for manufacturing a laser device.