JP3875799B2 - Semiconductor laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a distributed feedback semiconductor laser device.
[0002]
[Prior art]
Conventionally, semiconductor lasers have been widely used as light sources for optical recording devices, solid laser excitation, and optical communication. Among them, a distributed feedback (DFB) semiconductor laser forms a diffraction grating by providing periodic irregularities in the optical waveguide in the semiconductor laser, and uses the light feedback effect of the diffraction grating to stabilize the wavelength. We are trying to make it. Since such a DFB laser oscillates in a stable single mode, a longitudinal mode hopping phenomenon caused by a temperature change does not occur, and a mode hopping noise found in a normal Fabry-Perot semiconductor laser does not occur. It is excellent as a light source that requires a noise level. In addition, DFB lasers have excellent characteristics such as a small change in the temperature of the oscillation wavelength and the ability to select the oscillation wavelength by changing the period of the diffraction grating. Is preferred.
[0003]
FIG. 6 shows an example of a conventional DFB laser, FIG. 6A is an overall perspective view, and FIG. 6B is a partial perspective view showing the shape of a diffraction grating. This DFB laser is described in Japanese Patent Application Laid-Open No. 60-66484, and is sequentially formed on an n-type (hereinafter referred to as n-) GaAs substrate 102._0.40Ga_0.60As cladding layer 103, non-doped Al_0.10Ga_0.90As active layer 104, p-type (hereinafter referred to as p-) Al_0.25Ga_0.75As light guide layer 105, n-GaAs current blocking layer 106 having a striped window, p-Al_0.40Ga_0.60As cladding layer 107 and p-GaAs contact layer 108 are formed, and electrodes 101 and 109 are formed on the lower surface of substrate 102 and the upper surface of contact layer 108.
[0004]
As shown in FIG. 6B, diffraction gratings 112 and 113 having periodic unevenness are respectively formed on the upper surface of the light guide layer 105 and the portion 111 which becomes the bottom of the stripe-shaped window and on the upper surface of the current blocking layer 106. Is formed. A cladding layer 107 is formed on these diffraction gratings 112 and 113 so as to fill the stripe-shaped window.
[0005]
[Problems to be solved by the invention]
In the conventional DFB laser shown in FIG. 6, current is injected into the active layer 104 through the stripe window of the current blocking layer 106. Therefore, a diffraction grating is also formed in the portion 111 which becomes the bottom of the striped window of the light guide layer 105, that is, the current injection region.
[0006]
However, since the surface of the substrate is oxidized in the process of etching or the like during the production of the diffraction grating, the substrate surface is oxidized and a large number of crystal defects are generated. Therefore, in the structure of FIG. Crystal defects are concentrated in the vicinity, and there are portions having poor crystallinity.
[0007]
In such a semiconductor laser, the existing crystal defects are triggered during operation, and the crystal defects tend to increase further, and the lifetime is extremely shortened. In addition, the internal loss in the laser resonator increases, causing problems such as an increase in the oscillation threshold and a decrease in efficiency.
[0008]
An object of the present invention is to provide a semiconductor laser device having a low oscillation threshold, high oscillation efficiency, high reliability, long life, and stable oscillation wavelength.
[0018]
[Means for Solving the Problems]
  BookThe invention is provided with a pair of optical waveguide layers each having a forbidden band width equal to or larger than the forbidden band width of the active layer on both sides of the active layer,
  A pair of clad layers having a forbidden band width equal to or larger than the forbidden band width of the optical waveguide layer are provided to sandwich the active layer and the optical waveguide layer, respectively.
  Between the active layer and the optical waveguide layer, a carrier block layer having a forbidden band width equal to or larger than each forbidden band width of the active layer and the optical waveguide layer is provided.
  In a self-aligned semiconductor laser device in which a current blocking layer having a stripe-shaped window is embedded in at least one of the optical waveguide layers,
  The area of the current blocking layer on the active layer side, or between the active layer side interface and the active layer, excluding stripe-shaped windowsonlyFurther, the semiconductor laser device is characterized in that a diffraction grating for controlling the oscillation wavelength is formed.
[0019]
According to the present invention, when a voltage is applied to the semiconductor laser, carriers (electrons and holes) are injected and blocked by the current blocking layer when passing through the optical waveguide layer. Therefore, the carriers pass only through the portion where the current blocking layer does not exist, that is, the stripe-shaped groove portion. The carriers injected into the active layer recombine to emit light, and when the injection current level is increased, stimulated emission starts and eventually laser oscillation occurs. A part of the laser light penetrates to the lower part of the current blocking layer and is guided. On the other hand, since the carriers in the active layer are confined in the active layer due to the presence of the carrier block layer, the recombination efficiency is improved.
[0020]
  Below the current blocking layerOnlyA diffraction grating is formed to stabilize the oscillation wavelength. As a diffraction grating, a) a periodic unevenness formed on the active layer side interface of the current blocking layer, or b) the active layer sideofFor example, a grating layer formed between the interface and the active layer can be used. Here, the period Λ of the periodic unevenness or the period Λ in which the width of the grating layer changes isNextBy setting so as to satisfy the equation (1), single mode oscillation is obtained.
      Λ = m · λ o /(2.nr)                                        ... (1)
However, m is an integer greater than or equal to 1 (1, 2, 3, ...), n r Is the refractive index of the optical waveguide, λ o Is the oscillation wavelength.
[0021]
Further, in the present invention, the diffraction grating is formed only in the region excluding the stripe-shaped window, and there is no diffraction grating in the current injection region through which the current passes. Therefore, no crystal defect occurs in this region. Therefore, the possibility of problems such as an increase in oscillation threshold and a decrease in oscillation efficiency is extremely reduced. In addition, a decrease in reliability due to growth of crystal defects can be suppressed.
[0022]
By providing the carrier block layer between the active layer and the optical waveguide layer in this manner, the waveguide mechanism in the element can be freely designed independently of carrier confinement in the active layer. By adopting a wide optical waveguide layer, the waveguide mode can be made closer to an ideal Gaussian type. As a result, the refractive index and thickness of the diffraction grating can be selected in a wide range, so that the degree of freedom in design is increased, the manufacturing margin is widened, and the manufacturing yield of the semiconductor laser is improved. On the other hand, when the carrier block layer is not provided between the active layer and the optical waveguide layer, the waveguide mode is a Mt. Fuji type having a steep peak. On the other hand, when a carrier block layer is provided between the active layer and the optical waveguide layer, the waveguide mode is a Gaussian type with a protruding shoulder compared to the Mt. Fuji type. Becomes more gradual. Therefore, in a semiconductor laser having a Gaussian waveguide mode, even when the diffraction grating for controlling the wavelength is formed at a position away from the active layer, the diffraction grating functions sufficiently and the electric field intensity changes. Due to the mildness, even if the distance between the active layer and the diffraction grating and the refractive index distribution slightly change in the manufacturing process, the influence can be reduced, and the manufacturing yield of the element can be improved. .
[0023]
Further, the present invention is characterized in that the semiconductor material forming the optical waveguide layer is GaAs or AlGaAs having an Al composition of 0.3 or less, or InGaP or InGaAsP.
[0024]
According to the present invention, in a process for forming a diffraction grating that stabilizes the oscillation wavelength, an optical waveguide layer that is exposed to the atmosphere is made of a material having a low oxidative degradation, that is, a material having a low Al composition ratio or a material not containing Al. It is formed with. Therefore, the oxidation of the surface exposed to the atmosphere in the region where the diffraction grating is formed or the stripe portion is suppressed, the crystallinity of each layer to be regrown is improved, and a highly reliable semiconductor laser can be obtained. Here, the composition ratio of each element of InGaP and InGaAsP may be any as long as lattice matching with the substrate can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
In all of the following embodiments, the diffraction grating is manufactured by etching a layer forming the diffraction grating using a resist in which a grating is formed by a well-known interference exposure method as a mask. That is, when the layer that forms the diffraction grating is grown, a resist is applied, the resist is exposed in a grating shape by interference exposure of laser light, and then developed, and the lower layer is etched to a predetermined depth using the resist as a mask. Then, after removing the resist of the mask, the upper layer was continuously grown. In this step, the layer forming the diffraction grating is exposed to the atmosphere.
[0026]
(First embodiment)
1A and 1B show a first embodiment of the present invention, FIG. 1A is an overall perspective view, and FIG. 1B is a partial perspective view showing the shape of a diffraction grating. This semiconductor laser device is configured as a DFB laser, and sequentially, on a substrate 1 made of n-GaAs, a buffer layer 2 made of n-GaAs (thickness t = 0.5 μm), n-AlGaAs (Al composition ratio x = 0.4, t = 1.5 μm), clad layer 3, non-doped GaAs well layer (t = 0.008 μm) / non-doped AlGaAs barrier layer (x = 0.2, t = 0.005 μm) The subwell active layer 4, the cladding layer 6 made of p-AlGaAs (x = 0.4, t = 1.6 μm), and the contact layer 7 made of p-GaAs (t = 1.0 μm) are formed by MOCVD (organometallic chemical vapor). A current blocking layer 5 made of n-AlGaAs (x = 0.5, t = 0.1 μm) having a stripe-like window is embedded in the cladding layer 6. It has been. Electrodes 9 and 8 are formed on the lower surface of the substrate 1 and the upper surface of the contact layer 7, respectively.
[0027]
AlGaAs-based materials tend to increase the forbidden band width as the Al composition increases. In the present embodiment, the forbidden band width of the cladding layer is larger than the forbidden band width of the active layer 4.
[0028]
As shown in FIG. 1B, a diffraction grating 10 having a periodic concavo-convex shape is formed at the active layer side interface of the current blocking layer 5, and a striped window portion in which the current blocking layer 5 does not exist. 11, that is, there is no diffraction grating in the current injection region. A current blocking layer 5 is formed on the diffraction grating 10, and a cladding layer 6 is further formed so as to fill the window portion 11.
[0029]
Next, the operation will be described. When a positive bias voltage is applied to the electrode 8 of the contact layer 7 and a negative bias voltage is applied to the electrode 9 of the substrate 1, a current flows from the contact layer 7 toward the substrate 1, and a region where the current blocking layer 5 does not exist, that is, a striped window By passing only through the part 11, the current density increases.
[0030]
Current is injected into the active layer 4 as carriers, and light is radiated by carrier recombination. Furthermore, when the amount of injected current is increased, stimulated emission starts and eventually laser oscillation is reached. The laser light penetrates into the cladding layers 3 and 6 on both sides of the active layer 4 and also penetrates under the current blocking layer 5 to be guided.
[0031]
Here, by setting the period Λ of the diffraction grating 10 to satisfy the equation (1), only the wavelength λo is selectively oscillated, and as a result, single mode oscillation is obtained. At this time, since there is no deterioration of crystallinity in the window portion 11 which is a current injection region, a DFB semiconductor laser having a low oscillation threshold, high efficiency and long life can be realized.
[0032]
(Second Embodiment)
FIG. 2 is a perspective view showing a second embodiment of the present invention. This semiconductor laser device is configured as a DFB laser, and sequentially, on a substrate 21 made of n-GaAs, a buffer layer 22 made of n-GaAs (thickness t = 0.5 μm), n-AlGaAs (Al composition ratio x = 0.45, t = 1.5 μm), a non-doped AlGaAs well layer (x = 0.1, t = 0.006 μm) / AlGaAs barrier layer (x = 0.3, t = 0.005 μm) ) Double quantum well active layer 24, p-AlGaAs (x = 0.3, t = 0.15 μm) first cladding layer 25, p-AlGaAs (x = 0.55, t = 1.0 μm) ) And a contact layer 28 made of p-GaAs are formed using MOCVD (metal organic chemical vapor deposition) or the like, and the first cladding layer 25 and the second cladding layer 2 are further formed. And between, n-AlGaAs (x = 0.58, t = 0.1μm) current blocking layer 26 made of having a stripe-shaped window is embedded. Electrodes 30 and 29 are formed on the lower surface of the substrate 21 and the upper surface of the contact layer 28, respectively.
[0033]
Here, the first cladding layer 25 functions as an optical waveguide layer that guides light generated in the active layer 24. In addition, AlGaAs-based materials tend to increase the forbidden band width as the Al composition increases. In the present embodiment, the forbidden band width of the first cladding layer 25 is larger than the forbidden band width of the active layer 24, and further, the lower cladding layer 23 and the upper second cladding layer 27 below the first cladding layer 25. The forbidden bandwidth is larger.
[0034]
A diffraction grating 31 having a periodic concavo-convex shape is formed at the active layer side interface of the current blocking layer 26, and the diffraction grating is formed in the striped window portion 11 where the current blocking layer 26 does not exist, that is, in the current injection region. Does not exist.
[0035]
Next, the operation will be described. When a positive bias voltage is applied to the electrode 29 of the contact layer 28 and a negative bias voltage is applied to the electrode 30 of the substrate 21, a current flows from the contact layer 28 toward the substrate 21, and a region where the current blocking layer 26 does not exist, that is, a striped window By passing only through the part 11, the current density increases.
[0036]
Current is injected into the active layer 24 as carriers, and light is radiated by carrier recombination. Furthermore, when the amount of injected current is increased, stimulated emission starts and eventually laser oscillation is reached. The laser light penetrates into the cladding layer 23 and the first cladding layer 25 on both sides of the active layer 24 and also penetrates under the current blocking layer 26 to be guided.
[0037]
Here, by setting the period Λ of the diffraction grating 31 to satisfy the expression (1), only the wavelength λo is selectively oscillated, and as a result, single mode oscillation is obtained. At this time, since there is no deterioration of crystallinity in the window portion 11 which is a current injection region, a DFB semiconductor laser having a low oscillation threshold, high efficiency and long life can be realized.
[0038]
(Third embodiment)
FIG. 3 is a perspective view showing a third embodiment of the present invention. This semiconductor laser device is configured as a DFB laser, and sequentially, on a substrate 41 made of n-GaAs, a buffer layer 42 made of n-GaAs (thickness t = 0.5 μm), n-AlGaAs (Al composition ratio x = 0.24, t = 1.1 μm), clad layer 43, n-AlGaAs (x = 0.2, t = 0.88 μm) optical waveguide layer 44, n-AlGaAs (x = 0.5, carrier block layer 45 composed of t = 0.02 μm, non-doped InGaAs well layer (In composition ratio y = 0.2, t = 0.008 μm) / non-doped AlGaAs barrier layer (Al composition ratio x = 0.2, t = 0.006 μm) double quantum well active layer 46, p-AlGaAs (x = 0.5, t = 0.02 μm) carrier block layer 47, p-AlGaAs (x = 0.2) An optical waveguide layer 48 composed of t = 0.88 μm, a cladding layer 50 composed of p-AlGaAs (Al composition = 0.24, t = 1.1 μm), and a contact layer 51 composed of p-GaAs are formed by MOCVD (metal organic chemistry). A current blocking layer made of n-AlGaAs (Al composition ratio x = 0.33, t = 0.1 μm), which is formed by vapor phase epitaxy) or the like and has a striped window in the optical waveguide layer 48. 49 is embedded. Electrodes 53 and 52 are formed on the lower surface of the substrate 41 and the upper surface of the contact layer 51, respectively.
[0039]
AlGaAs-based materials have a larger forbidden band width than InGaAs-based materials, and the forbidden band width tends to increase as the Al composition increases. In the present embodiment, the forbidden band width of the optical waveguide layers 44 and 48 is larger than the forbidden band width of the active layer 46, and each of the forbidden band widths of the cladding layers 43 and 50 is larger than that of the optical waveguide layers 44 and 48. In addition, the forbidden band widths of the carrier block layers 45 and 47 are larger than those of the optical waveguide layers 44 and 48.
[0040]
A diffraction grating 61 having a periodic concavo-convex shape is formed at the active layer side interface of the current blocking layer 49, and the diffraction grating is formed in the striped window portion 11 where the current blocking layer 49 does not exist, that is, in the current injection region. Does not exist.
[0041]
Next, the operation will be described. When a positive bias voltage is applied to the electrode 52 of the contact layer 51 and a negative bias voltage is applied to the electrode 53 of the substrate 41, a current flows from the contact layer 51 toward the substrate 41, and a region where the current blocking layer 49 does not exist, that is, a striped window By passing only through the part 11, the current density increases.
[0042]
The current is injected as carriers into the active layer 46 and radiates light by carrier recombination. Furthermore, when the amount of injected current is increased, stimulated emission starts and eventually laser oscillation is reached. The laser light penetrates into the optical waveguide layers 44 and 48 on both sides of the active layer 46 and also penetrates under the current blocking layer 49 to be guided. On the other hand, the carriers in the active layer 46 are confined in the active layer due to the presence of the carrier block layers 45 and 47, so that the recombination efficiency is improved.
[0043]
Here, by setting the period Λ of the diffraction grating 61 to satisfy the equation (1), only the wavelength λo is selectively oscillated, and as a result, single mode oscillation is obtained. At this time, since there is no deterioration of crystallinity in the window portion 11 which is a current injection region, a DFB semiconductor laser having a low oscillation threshold, high efficiency and long life can be realized.
[0044]
In the present embodiment, the case where the diffraction grating 61 is formed at the active layer side interface of the current blocking layer 49 has been described. However, a similar diffraction grating may be formed at the contact layer side interface of the current blocking layer 49.
[0045]
(Fourth embodiment)
FIG. 4 shows a fourth embodiment of the present invention, FIG. 4 (a) is an overall perspective view, and FIG. 4 (b) is a partial perspective view showing the shape of a diffraction grating. This semiconductor laser device is configured as a DFB laser, and sequentially, on a substrate 71 made of n-GaAs, a buffer layer 72 made of n-GaAs (thickness t = 0.5 μm), n-AlGaAs (Al composition ratio x = 0.24, t = 1.1 μm) clad layer 73, n-AlGaAs (x = 0.2, t = 0.83 μm) optical waveguide layer 74, n-AlGaAs (x = 0.5, carrier block layer 75 comprising t = 0.02 μm, non-doped InGaAs well layer (In composition ratio y = 0.2, t = 0.008 μm) / non-doped AlGaAs barrier layer (Al composition ratio x = 0.2, t = 0.006 μm) double quantum well active layer 76, p-AlGaAs (x = 0.5, t = 0.02 μm) carrier block layer 77, p-AlGaAs (x = 0.2) An optical waveguide layer 78 composed of t = 0.83 μm, a cladding layer 80 composed of p-AlGaAs (Al composition = 0.24, t = 1.1 μm), and a contact layer 81 composed of p-GaAs are formed by MOCVD (organometallic chemistry). A current blocking layer made of n-AlGaAs (Al composition ratio x = 0.24, t = 0.1 μm) having a stripe-shaped window in the optical waveguide layer 78. 79 is embedded. Electrodes 83 and 82 are formed on the lower surface of the substrate 71 and the upper surface of the contact layer 81, respectively.
[0046]
AlGaAs-based materials have a larger forbidden band width than InGaAs-based materials, and the forbidden band width tends to increase as the Al composition increases. In this embodiment, the forbidden band width of the optical waveguide layers 74 and 78 is larger than the forbidden band width of the active layer 76, and each of the forbidden band widths of the cladding layers 73 and 80 is further larger than the optical waveguide layers 74 and 78. The forbidden band widths of the carrier block layers 75 and 77 are larger than those of the optical waveguide layers 74 and 78.
[0047]
In this embodiment, a grating layer 91 having an equivalent function is provided instead of the wavelength controlling diffraction grating 61 shown in FIG.
[0048]
The grating layer 91 is formed by forming p-GaAs (thickness t = 0.05 μm) in the optical waveguide layer 78 so as to have a periodic pattern, and the active layer side interface of the current blocking layer 79 and the active layer side. Located between the layers 76, the window portion 11 is formed to have a uniform thickness, and the both sides of the window portion 11 are formed to have a periodic uneven shape, thereby functioning as a diffraction grating having a period Λ. By setting the period Λ so as to satisfy the equation (1), only the wavelength λo is selectively oscillated, and as a result, single mode oscillation is obtained. At this time, since the window portion 11 which is a current injection region is protected by the grating layer 91, the crystallinity is not deteriorated, and a DFB semiconductor laser having a low oscillation threshold, high efficiency and long life can be realized.
[0049]
(Fifth embodiment)
FIG. 5 shows a fifth embodiment of the present invention, FIG. 5 (a) is an overall perspective view, and FIG. 5 (b) is a partial perspective view showing the shape of a diffraction grating. This semiconductor laser device is configured as a DFB laser, and sequentially, on a substrate 71 made of n-GaAs, a buffer layer 72 made of n-GaAs (thickness t = 0.5 μm), n-AlGaAs (Al composition ratio x = 0.24, t = 1.1 μm) clad layer 73, n-AlGaAs (x = 0.2, t = 0.83 μm) optical waveguide layer 74, n-AlGaAs (x = 0.5, carrier block layer 75 comprising t = 0.02 μm, non-doped InGaAs well layer (In composition ratio y = 0.2, t = 0.008 μm) / non-doped AlGaAs barrier layer (Al composition ratio x = 0.2, t = 0.006 μm) double quantum well active layer 76, p-AlGaAs (x = 0.5, t = 0.02 μm) carrier block layer 77, p-AlGaAs (x = 0.2) An optical waveguide layer 78 composed of t = 0.83 μm, a cladding layer 80 composed of p-AlGaAs (Al composition = 0.24, t = 1.1 μm), and a contact layer 81 composed of p-GaAs are formed by MOCVD (organometallic chemistry). A current blocking layer made of n-AlGaAs (Al composition ratio x = 0.24, t = 0.1 μm) having a stripe-shaped window in the optical waveguide layer 78. 79 is embedded. Electrodes 53 and 52 are formed on the lower surface of the substrate 71 and the upper surface of the contact layer 81, respectively.
[0050]
AlGaAs-based materials have a larger forbidden band width than InGaAs-based materials, and the forbidden band width tends to increase as the Al composition increases. In this embodiment, the forbidden band width of the optical waveguide layers 74 and 78 is larger than the forbidden band width of the active layer 76, and each of the forbidden band widths of the cladding layers 73 and 80 is further larger than the optical waveguide layers 74 and 78. The forbidden band widths of the carrier block layers 75 and 77 are larger than those of the optical waveguide layers 74 and 78.
[0051]
In this embodiment, a grating layer 91 having an equivalent function is provided instead of the wavelength controlling diffraction grating 61 shown in FIG.
[0052]
The grating layer 91 is formed by forming p-GaAs (thickness t = 0.05 μm) in the optical waveguide layer 78 so as to have a periodic pattern, and the active layer side interface of the current blocking layer 79 and the active layer side. It is located between the layers 76 and is formed in a periodic uneven shape on both sides of the window portion 11 and functions as a diffraction grating having a period Λ. The grating layer 91 is not formed in the window portion 11. As a method of forming the grating layer on both sides of the window portion, there are a method using selective growth of the grating layer, a method of removing the grating layer grown including the window portion by etching only the window portion, and the like.
[0053]
By setting the period Λ so as to satisfy the equation (1), only the wavelength λo is selectively oscillated, and as a result, single mode oscillation is obtained. At this time, the window portion 11 which is a current injection region does not have the grating layer 91, and no layer having a different refractive index exists in the stripe-shaped window portion 11, so that there is an advantage that the mode of the oscillating laser beam is not disturbed. .
[0054]
In the above embodiments, the waveguide layer is made of AlGaAs. However, in these structures, the waveguide layer has little Al or contains Al, such as InGaP, InGaAsP, or AlGaAs (Al composition x is 0 ≦ x ≦ 0.3). No composition is preferred. By making the waveguide layer have such a composition, the effect of suppressing damage due to oxidation when forming the diffraction grating is further enhanced, and higher reliability can be obtained.
[0055]
【The invention's effect】
  As described in detail above, according to the present invention, the interface of the current blocking layer or between the interface and the active layer is used.onlyBy forming a diffraction grating to control the oscillation wavelength, wavelength selectivity based on the periodic structure is given, and only the wavelength that satisfies the diffraction condition oscillates selectively, and stable single mode oscillation Is obtained.
  Furthermore, since such a diffraction grating is not formed in the current injection region, crystal defects in this region are remarkably reduced. As a result, a semiconductor laser device having high oscillation efficiency, high reliability, and long life with a low oscillation threshold. Can be realized.
[0056]
Furthermore, since such a diffraction grating is not formed in the current injection region, crystal defects in this region are remarkably reduced. As a result, a semiconductor laser device having high oscillation efficiency, high reliability, and long life with a low oscillation threshold. Can be realized.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of the present invention, FIG. 1 (a) is an overall perspective view, and FIG. 1 (b) is a partial perspective view showing the shape of a diffraction grating.
FIG. 2 is a perspective view showing a second embodiment of the present invention.
FIG. 3 is a perspective view showing a third embodiment of the present invention.
4A and 4B show a fourth embodiment of the present invention, in which FIG. 4A is an overall perspective view, and FIG. 4B is a partial perspective view showing the shape of a diffraction grating.
5A and 5B show a fifth embodiment of the present invention, in which FIG. 5A is an overall perspective view, and FIG. 5B is a partial perspective view showing the shape of a diffraction grating.
6A and 6B show an example of a conventional DFB laser. FIG. 6A is an overall perspective view, and FIG. 6B is a partial perspective view showing the shape of a diffraction grating.
[Explanation of symbols]
1, 21, 41, 71 substrate
2, 22, 42, 72 Buffer layer
3, 6, 23, 43, 50, 73, 80 Clad layer
4, 24, 46, 76 Active layer
5, 26, 49, 79 Current blocking layer
7, 28, 51, 81 Contact layer
8, 9, 29, 30, 52, 53, 82, 83 electrodes
10, 31, 61 Diffraction grating
11 Window
25 First cladding layer
27 Second cladding layer
44, 48, 74, 78 Optical waveguide layer
45, 47, 75, 77 Carrier block layer
91 grating layer

Claims (2)

A pair of optical waveguide layers having a forbidden band width equal to or larger than the forbidden band width of the active layer are provided on both sides of the active layer, respectively.
A pair of clad layers having a forbidden band width equal to or larger than the forbidden band width of the optical waveguide layer are provided so as to sandwich the active layer and the optical waveguide layer,
Between the active layer and the optical waveguide layer, a carrier block layer having a forbidden band width greater than or equal to each forbidden band width of the active layer and the optical waveguide layer is provided.
In a self-aligned semiconductor laser device in which a current blocking layer having a stripe-shaped window is embedded in at least one of the optical waveguide layers,
A diffraction grating for controlling the oscillation wavelength is formed only at the interface of the current blocking layer on the active layer side or between the active layer side interface and the active layer except for the stripe-shaped window. A semiconductor laser device. The semiconductor material forming the optical waveguide layer, GaAs or Al composition 0.3 following AlGaAs or InGaP, a semiconductor laser device according to claim 1, wherein that you with any of InGaAsP,.

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