JPH05145169A - Semiconductor distributed feedback laser apparatus - Google Patents

Abstract

PURPOSE:To implement the light distribution feedback by a gain coupling by providing a cyclic structure for the distribution feedback adjacently to an active layer so that the conductiveness varies periodically in the axial direction of a laser light. CONSTITUTION:Diffraction gratings 7 are formed between a buffer layer 5 and a clad layer 8 in a conductive type which differs from that of these layers. In other words, while the buffer layer 5 and clad layer 8 are formed by an n-type semiconductor, for example, the diffraction gratings 7 are formed by a highly concentrated p-type semiconductor. The fundamental composition of the materials of these semiconductors are the same. Only the impurity doping in them differ from each other. The refractive indexes are also equal. With this structure, the density of the current passing vertically through the plane including the diffraction gratings 7 varies in the axial direction of the laser. Therefore, a carrier density distribution is formed on the active layer 4, and the gain coefficient against the optical wave which is propagated in the laser axial direction is varied in a cycle which agrees with the cycle of the diffraction gratings. Thus, it is possible to implement the distribution feedback by the gain coupling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used as an electro-optical conversion element. INDUSTRIAL APPLICABILITY The present invention is suitable for use as a light source of an optical communication device, an optical information processing device, an optical storage device, an optical measurement device and other optoelectronic devices.

[0002]

2. Description of the Related Art A semiconductor distributed feedback laser device is provided with a diffraction grating in the vicinity of an active layer that generates light by recombination of electrons and holes, and the distributed feedback is applied to the active layer by this diffraction grating to perform stimulated emission. Emits light. By using such a semiconductor distributed feedback laser device, generally, stimulated emission light having an excellent oscillation spectrum characteristic can be obtained with a relatively simple structure.
For this reason, many researches and developments have been made in the past,
Its usefulness is expected as a light source device suitable for use in long-distance large-capacity optical communication, optical information processing, optical recording, optical applied measurement, and the like.

A conventional semiconductor distributed feedback laser device uses a double hetero structure in which an active layer is sandwiched between transparent clad semiconductor layers to efficiently generate and guide stimulated emission light, and is provided in close proximity to the active layer. It is widely known that a diffraction grating having a triangular wave-shaped cross section is formed on the surface of the transparent waveguide layer on the side remote from the active layer. In this structure, the stimulated emission light propagating along the active layer is subjected to distributed light feedback by periodically changing the waveguide refractive index with a diffraction grating.

[0004]

However, in the distributed light distribution by so-called refractive index coupling based on such a periodic change of the refractive index, the Bragg wavelength of the reflection corresponding to the period of the layer thickness change of the optical waveguide layer is performed. The light was not properly fed back as to the optical phase. For this reason, stable laser oscillation cannot be obtained at this wavelength, and there is a high possibility that longitudinal mode oscillations of two wavelengths symmetrically spaced above and below the Bragg wavelength occur simultaneously.

Further, even when only one of these two wavelength longitudinal mode oscillations occurs, it is difficult to select in advance which wavelength of the two wavelengths longitudinal mode oscillation is to be performed. However, the accuracy of the oscillation wavelength setting was significantly impaired.

[0006] Such a problem, that is, a problem of degeneracy of two-wavelength longitudinal mode which is theoretically accompanied when performing distributed optical feedback by refractive index coupling based on periodic perturbation of the refractive index in the optical waveguide layer. In order to solve the problem, various structures have been studied in the past. As an example thereof, a so-called quarter wavelength shift structure is known in which the phase is suddenly changed by 180 ° in the center of the diffraction grating. However, the structure of the laser device becomes complicated, and it is necessary to add a special manufacturing process only to provide the above-mentioned special structure for eliminating degeneracy. Moreover, it is necessary to form an antireflection film on the end face of the laser element.

On the other hand, in the distributed feedback laser device, in general,
As described above, when distributed optical feedback is performed by refractive index coupling, an oscillation stop band occurs in the Bragg wavelength region. However, if distributed optical feedback by so-called gain coupling based on periodic perturbation of gain coefficient is performed, such an oscillation stop band is generated. Should be suppressed, and a single-mode longitudinal mode oscillation should be obtained. This theory is based on "Coupled-Wave Theory of Distribut," by Kogelnik et al.
ed Feedback Lasers ", J.Appl.Phys. Vol.43, 1972, pp.
2327-2335). As an example in which this is realized by a semiconductor laser device, a patent application by the inventors of the present application is Japanese Patent Application No. Sho 63-189593, filed on July 30, 1988, Japanese Patent Application Laid-Open No. 3-34489 (Japanese Patent Application No. 1-168729, Heisei 1). Application filed on June 30) Japanese Patent Application Laid-Open No. 3-49283 to 49287 (Japanese Patent Application No. 1-185)
No. 001-185005, filed on July 18, 1991), but the theory of Kogelnik et al. Is fundamental and is not so much studied as an actual structure.

The present invention is realized by applying gain coupling to a semiconductor laser device without complicating the structure of the device.
It is an object of the present invention to provide a new semiconductor distributed feedback laser device in which oscillation of a completely single longitudinal mode is obtained on the Bragg wavelength.

[0009]

SUMMARY OF THE INVENTION A semiconductor distributed feedback laser device of the present invention is for distributed feedback in which the conductivity is periodically changed along the laser optical axis direction in the vicinity of at least one surface of an active layer. It is characterized by having a periodic structure of.

A semiconductor laser device generally includes two sets of semiconductor layers having different conductivity types with an active layer interposed therebetween. Therefore, as one embodiment of the present invention, a diffraction grating is formed in a semiconductor layer adjacent to one side of the active layer with a semiconductor material having a conductivity type or conductivity different from that of the layer. As the material of the diffraction grating, it is desirable to use a material having the same refractive index as that of the semiconductor layer on the side where the diffraction grating is provided but having the same conductivity type or conductivity. It is desirable that the diffraction grating has a shape in which the layers of the semiconductor material forming the diffraction grating are periodically cut.

In order to manufacture a semiconductor distributed feedback laser device having such a structure, 0.1 μm is formed on one surface of the active layer.
An extremely thin buffer layer is provided, and a semiconductor layer having the same composition as the buffer layer and different conductivity type or conductivity is provided on the surface of the buffer layer opposite to the active layer. To form a diffraction grating, and the diffraction grating is filled with a semiconductor material having the same refractive index and the same conductivity as the buffer layer.

In addition to this method, after forming the diffraction grating, the active layer may be grown on the diffraction grating via a buffer layer.

When the active layer is grown after forming the diffraction grating, the periodic uneven shape of the diffraction grating may affect the shape of the active layer, particularly the thickness distribution. The present invention can also positively utilize this. That is, the diffraction grating may be formed as a periodic uneven shape along the laser optical axis direction, and a structure in which the thickness distribution of the active layer is changed corresponding to the uneven shape may be adopted. This structure is disclosed in the above-mentioned patent applications, especially Japanese Patent Application No. 63-189593 and Japanese Patent Laid-Open No.
-44489, 3-49283, 3-49284, and the structures shown in the drawings and drawings, respectively, are combined with the conductive periodic distribution which is a feature of the present invention.

In any case, it is most desirable that the diffraction grating has a shape in which layers having different conductivity are periodically cut.

The diffraction grating can also be formed by ion implantation or diffusion. That is, a material that changes the conductivity type or conductivity of the semiconductor layer is ion-implanted or diffused into the semiconductor layer adjacent to one side of the active layer at the period of the diffraction grating.

[0016]

When a layer whose conductivity changes periodically is provided close to the active layer (away from the active layer by about 0.1 μm), a current density distribution occurs in the active layer, which results in a periodic distribution of carrier density. Is generated. Further, the periodic distribution induces a periodic perturbation of the gain coefficient, and the optical distributed feedback is performed based on the periodic perturbation.

That is, when the carrier density distribution is formed in the active layer, the gain coefficient for the light wave propagating in the optical axis direction of the laser changes in a cycle that coincides with the cycle of the diffraction grating. Is realized.

It has been proved that the distributed optical feedback by gain coupling is also advantageous for realizing generation of short optical pulses, high-speed direct modulation, low chirp operation and the like.

[0019]

1 shows a semiconductor distributed feedback laser device according to a first embodiment of the present invention.

This embodiment is a laser device having a double hetero structure, which is provided with an active layer 4 for generating stimulated emission light, and is arranged along this active layer 4 to distribute light to the stimulated emission light generated by this active layer 4. A diffraction grating 7 is provided as a periodic structure for feedback.

More specifically, the buffer layer 2, the cladding layer 3, the active layer 4, the buffer layer 5, the diffraction grating 7, the cladding layer 8 and the contact layer 9 are laminated on the substrate 1,
The electrode layer 11 is connected to the contact layer 9 through a striped window of the insulating layer 10, and the electrode layer 1 is formed on the back surface of the substrate 1.
Two are provided. The two semiconductor layers sandwiching the active layer 4 have different conductivity types from each other. For example, when the substrate 1, the buffer layer 2 and the cladding layer 3 are p-type, the buffer layer 5, the cladding layer 8 and the contact layer 9 are n-type. And

Examples of the conductivity type, composition and thickness of each layer are shown below.

Substrate 1 p ⁺ -GaAs buffer layer 2 p ⁺ -GaAs 0.5 μm cladding layer 3 p-Al _0.45 Ga _0.55 As 1 μm active layer 4 low impurity concentration GaAs 0.1 μm buffer layer 5 n-Al _0.45 Ga _0.55 As 0.1 μm Diffraction grating 7 p ⁺ -Al _0.45 Ga _0.55 As 0.1 μm Cladding layer 8 n-Al _0.45 Ga _0.55 As 1 μm Contact layer 9 n ⁺ -GaAs 0.5 μm Insulation layer 10 SiO ₂ electrode layer 11 Au / Au- Ge electrode layer 12 Au / Cr

Although the thickness of the diffraction grating 7 changes periodically, the thickness of the thickest portion is shown here. The thinnest part is completely removed in this example. The period of the diffraction grating 7 is 255 nm, for example, and the oscillation light wavelength at that time is 880 nm. The width of the stripe-shaped window provided in the insulating layer 10 is, eg, 10 μm.

The feature of this embodiment is that the diffraction grating 7 is formed between the buffer layer 5 and the cladding layer 8 with a conductivity type different from those of the buffer layer 5 and the cladding layer 8. That is, the buffer layer 5 and the cladding layer 8 are formed of an n-type semiconductor, while the diffraction grating 7 is formed of a high-concentration p-type semiconductor. However, they differ from each other only in impurity doping, have the same basic composition of materials, and have the same refractive index.

With this structure, the density of the current passing vertically through the plane including the diffraction grating 7 changes periodically along the laser optical axis direction. Therefore, a carrier density distribution is formed in the active layer 4, and the gain coefficient for the light wave propagating in the laser optical axis direction changes in a cycle that matches the cycle of the diffraction grating 7. Therefore, distributed feedback is realized by gain coupling.

The buffer layer 5 is for preventing various crystal defects generated when the diffraction grating 7 is imprinted from propagating to the active layer 4.

A method of manufacturing this semiconductor distributed feedback laser device will be described. In this method, each layer forming the double hetero structure is formed on the substrate 1 by a two-step epitaxial growth process.

In the first stage epitaxial growth process,
The buffer layer 2, the cladding layer 3, the active layer 4, the buffer layer 5 and the current blocking layer 6 are continuously grown on the substrate 1 by the metal organic vapor phase epitaxial growth method.

Subsequently, the uppermost current blocking layer 6 formed in this growth step is subjected to interference exposure and chemical etching or dry etching to imprint a periodic pattern. At this time, the thickness of the selectively removed portion is equal to or larger than the thickness of the current blocking layer 6, and the portion left unremoved is the diffraction grating 7.

After that, the second-stage epitaxial growth is performed to continuously grow the cladding layer 8 and the contact layer 9 on the buffer layer 5 and the current blocking layer 6, and the diffraction grating 7 is embedded. This growth is also performed by the metal organic vapor phase epitaxial growth method. This completes the double heterostructure.

Next, the insulating layer 10 is formed on the upper surface of the contact layer 9.
After forming a stripe-shaped window on the insulating layer 10, an electrode layer 11 is vapor-deposited on the entire surface. Further, the electrode layer 12 is deposited on the back surface of the substrate 1.

Through the above steps, a semiconductor block having a laser structure is formed on the semiconductor wafer. This semiconductor block is cleaved to complete individual semiconductor laser devices.

In this embodiment, a material having a conductivity type of p ⁺ is used as the diffraction grating 7. This is because the cladding layer 8 is n-type, and p ⁺ -type materials having different conductivity types are most effective for making the conductivity significantly different from that. However, for the n-type cladding layer 8, the diffraction grating 7
As p-type, intrinsic type (i-type) or weak n-type (n
^The present invention can also be carried out by using -type. Further, a high resistance material or a low resistance material may be used in some cases.

Further, the present invention can be implemented in the same manner even if the conductivity type of pn is reversed. Examples of the conductivity type, composition and thickness of each layer in that case are shown below. The diffraction grating 7 in this case
It is most effective to set the conductivity type to n ⁺ type so that the conductivity is largely different from that of the cladding layer 8 (p type in this case), but n type, i type or p ⁻ type can also be used. It is also possible to use a high resistance material or a low resistance material in some cases.

Substrate 1 n ⁺ -GaAs buffer layer 2 n ⁺ -GaAs 0.5 μm cladding layer 3 n-Al _0.45 Ga _0.55 As 1 μm active layer 4 low impurity concentration GaAs 0.1 μm buffer layer 5 p-Al _0.45 Ga _0.55 As 0.1 μm Diffraction grating 7 n ⁺ -Al _0.45 Ga _0.55 As 0.1 μm Cladding layer 8 p-Al _0.45 Ga _0.55 As 1 μm Contact layer 9 p ⁺ -GaAs 0.5 μm Insulating layer 10 SiO ₂ electrode layer 11 Au / Cr electrode Layer 12 Au / Au-Ge

FIG. 2 shows a semiconductor distributed feedback laser device according to the second embodiment of the present invention.

The difference of this embodiment from the first embodiment is that a diffraction grating for periodically changing the conductivity is provided between the substrate and the active layer and corresponds to the periodic uneven shape of this diffraction grating. Therefore, the thickness of the active layer is also periodically changed.

A buffer layer 22, a clad layer 23, a diffraction grating 27, a buffer layer 25, an active layer 24, a clad layer 28 and a contact layer 29 are laminated on the substrate 21, and the contact layer 29 has a stripe shape of an insulating layer 30. The electrode layer 31 is connected through the window of the
Two are provided. The two sets of semiconductor layers sandwiching the active layer 24, that is, the semiconductor layer including the substrate 21, the buffer layer 22, the cladding layer 23, and the buffer layer 25, and the semiconductor layer including the cladding layer 28 and the contact layer 29 have conductivity types with each other. different.

The diffraction grating 27 is made of a material having a conductivity type or conductivity different from those of the cladding layer 23 and the buffer layer 25, and is formed into an uneven shape which is periodically cut along the laser optical axis direction.

The diffraction grating 27 is filled with a buffer layer 25. The buffer layer 25 is formed so that the defects of the semiconductor crystal structure do not reach the active layer 24, and the diffraction grating 27 has an uneven shape. ..

The active layer 24 is formed so as to fill the concave and convex portions of the buffer layer 25.

This embodiment is formed by a manufacturing method including a two-step epitaxial growth process.

In the first stage epitaxial growth process,
The buffer layer 22, the cladding layer 23, and the current blocking layer are continuously grown on the substrate 21 by the metal organic vapor phase epitaxial growth method.

Subsequently, an interference exposure method and chemical etching or dry etching are applied to the uppermost current blocking layer formed in this growth step to print a diffraction grating pattern. At this time, the thickness of the selectively cut portion is equal to or larger than the thickness of the current blocking layer, and the remaining portion is used as the diffraction grating 27.

After that, the second-stage epitaxial growth is carried out, and the buffer layer 25 and the active layer 2 are formed on the diffraction grating 27.
4. Clad layer 28 and contact layer 29 are continuously grown. This growth is also performed by the metal organic vapor phase epitaxial growth method. This completes the double heterostructure. At this time, for the buffer layer 25, the diffraction grating 27
The growth is performed so that the uneven shape is preserved and the active layer 24 is not affected by the defects of the semiconductor crystal structure generated by the imprinting. Further, the active layer 24 is grown so as to fill the concave and convex portions.

Next, the insulating layer 3 is formed on the upper surface of the contact layer 29.
After depositing 0 and forming a stripe-shaped window in the insulating layer 30, an electrode layer 31 is vapor-deposited on the entire surface. Also, the substrate 2
The electrode layer 32 is vapor-deposited on the back surface of 1.

Through the above steps, a semiconductor block having a laser structure is formed on the semiconductor wafer. This semiconductor block is cleaved to complete individual semiconductor laser devices.

The first diffraction grating 27 has a rectangular cross section, the buffer layer 25 is grown so that its surface has a triangular wave shape, and the active layer 24 is grown so that its surface becomes a flat surface. You can also

Substrate 21, buffer layer 22, clad layer 2
An example of the composition of each layer when the conductivity type of 3 and the buffer layer 25 is p-type and the cladding layer 28 and the contact layer 29 are n-type, and the composition of each layer when they are the opposite conductivity type is shown below.

Substrate 21 p ⁺ -GaAs buffer layer 22 p ⁺ -GaAs cladding layer 23 p -Al _0.45 Ga _0.55 As diffraction grating 27 n ⁺ -Al _0.25 Ga _0.75 As buffer layer 25 p-Al _0.4 Ga _0.6 As active layer 24 Low impurity concentration GaAs clad layer 28 n-Al _0.45 Ga _0.55 As contact layer 29 n ⁺ -GaAs insulating layer 30 SiO ₂ electrode layer 31 Au-Ge electrode layer 32 Au-Zn

Substrate 21 n ⁺ -GaAs buffer layer 22 n ⁺ -GaAs clad layer 23 n-Al _0.45 Ga _0.55 As diffraction grating 27 p ⁺ -Al _0.25 Ga _0.75 As buffer layer 25 n-Al _0.4 Ga _0.6 As active layer 24 Low impurity concentration GaAs clad layer 28 p-Al _0.45 Ga _0.55 As contact layer 29 p ⁺ -GaAs insulating layer 30 SiO ₂ electrode layer 31 Au-Zn electrode layer 32 Au-Ge

Also in the case of this embodiment, it is effective to use the diffraction grating 27 having a conductivity type different from that of the surrounding layer, but if the conductivity is different, the diffraction grating 27 having the same conductivity type is used. Alternatively, a high resistance material can be used.

In the above embodiments, an example in which a bulk crystal is used as the active layer has been described, but the present invention can be similarly implemented by using a single quantum well or multiple quantum wells.

The material of the substrate, the clad layer and the active layer is GaAs-Al _0.45 Ga _0.55 As described above.
-GaAs in addition to GaAs-Al _x Ga
_{1-x As-Al y Ga} 1-y As, InP-InP-In
_The present invention can be similarly applied to a combination of materials of currently used semiconductor laser devices such as _x Ga _1-x As _y P _1-y . Further, the present invention can be applied to the case of using other materials. it can. Lattice-matched to InP below to 1.6
An example of the composition when oscillating at 5 μm is shown. The first example is a composition example when the structure of the first embodiment is used, and the second example is a composition example when the structure of the second embodiment shown in FIG. 2 is used.

Substrate 1 p ⁺ or n ⁺ -InP buffer layer 2 p ⁺ or n ⁺ -InP clad layer 3 p or n -InP active layer 4 low impurity concentration In _0.53 Ga _0.47 As buffer layer 5 n or p -In _0.82 Ga _0.18 As _0.40 P _0.60 Grating 7 p ⁺ or n ⁺ -In _0.72 Ga _0.28 As _0.61 P _0.39 Cladding layer 8 n or p -InP contact layer 9 n ⁺ or p ⁺ -In _0.53 Ga _0.47 As

Substrate 21 p ⁺ or n ⁺ -InP buffer layer 22 p ⁺ or n ⁺ -InP cladding layer 23 p or n -InP diffraction grating 27 n ⁺ or p ⁺ -In _0.72 Ga _0.28 As _0.61 P _0.39 (λ _g = 1.3 μm) buffer layer 25 p or n-In _0.82 Ga _0.18 As _0.40 P _0.60 (λ _g = 1.15 μm) active layer 24 low impurity concentration In _0.53 Ga _0.47 As clad layer 28 n or p-InP contact layer 29 n ⁺ or p ⁺ -In _0.53 Ga _0.47 As

In the above embodiments, the diffraction grating provided with the periodic unevenness as the periodic structure is used, but it is also possible to provide the periodical conductivity change by ion implantation or diffusion.
As such an example, an embodiment using ion implantation will be described below.

FIG. 3 shows a semiconductor distributed feedback laser device according to the third embodiment of the present invention.

This example differs greatly from the first example in that a semiconductor layer adjacent to the active layer is periodically ion-implanted with a material that changes conductivity. That is, on the substrate 1, the buffer layer 2, the cladding layer 3, the semiconductor layer 36,
A buffer layer 5, an active layer 4, a clad layer 8, and a contact layer 9 are laminated, an electrode layer 11 is connected to the contact layer 9 through a stripe-shaped window of an insulating layer 10, and an electrode layer is formed on the back surface of the substrate 1. Twelve are provided. Ion implantation regions 37 are periodically provided from the semiconductor layer 36 to the cladding layer 3.

To manufacture this laser device, first, the buffer layer 2, the cladding layer 3 and the semiconductor layer 36 are formed on the substrate 1.
Are grown, and an ion implantation mask layer is further grown. Subsequently, an interference exposure method and anisotropic etching such as reactive ion etching are used to form irregularities on the surface of the ion implantation mask layer. When this is ion-implanted, the convex portions of the ion-implantation mask layer serve as a mask, and ion-implanted regions 37 are periodically formed in the semiconductor layer 36.
After that, the ion implantation mask layer is removed by selective etching, and the buffer layer 5 or the contact layer 9 is crystal-grown.

An example of InP composition is shown below.

Substrate 1 p ⁺ or n ⁺ -InP buffer layer 2 p ⁺ or n ⁺ -InP clad layer 3 p or n -InP semiconductor layer 36 p or n-In _0.72 Ga _0.28 As _0.61 P _0.39 (λ _g = 1 Buffer layer 5 p or n-InP active layer 4 low impurity concentration In _0.53 Ga _0.47 As and InGaAsP (λ _g = 1.3 μm) multiple quantum well (equivalent λ _g = 1.55 μm) cladding layer 8 n or p − InP contact layer 9 n ⁺ or p ⁺ −In _0.53 Ga _0.47 As

As the active layer 4, in addition to the multiple quantum well,
A single quantum well or bulk can also be used.

To increase the resistance of the ion implantation region 37,
In the case of InP system, oxygen is ion-implanted. Alternatively, iron may be ion-implanted. In the case of GaAs, oxygen or hydrogen is ion-implanted. Further, a material that changes the conductivity type of the semiconductor layer 36 may be ion-implanted. For example, in the case of a GaAs system, the S
i can be ion-implanted to make it n-type.

In this example, the semiconductor layer is used as the ion implantation mask layer, but other materials can be used. Also, thermal diffusion may be used instead of ion implantation.

[0067]

As described above, the semiconductor distributed feedback laser device of the present invention is different from the conventional refractive index coupled semiconductor distributed feedback laser device in that it can perform longitudinal mode oscillation of a single wavelength. In principle, the uncertainty of the oscillation wavelength as in the conventional device does not occur. Moreover, the structure of the device does not become complicated as in the case of realizing a complete single longitudinal mode in the conventional semiconductor distributed feedback laser device, an antireflection film is not required, and the complete single longitudinal mode can be easily performed. Can be realized.

Further, in the semiconductor distributed feedback laser device of the present invention, optical distributed feedback is achieved by gain coupling, so that coherent noise induced by reflected return light from the near end or far end is Even if it occurs, it is expected to be significantly smaller than that in the case of the conventional refractive index coupling.

Further, in the semiconductor distributed feedback laser device of the present invention, since the optical resonator is constructed only after the periodically distributed current is injected, it is possible to generate an ultrashort optical pulse in high speed current modulation. Furthermore, the chirping of the oscillation wavelength is expected to be small.

Therefore, the semiconductor distributed feedback laser device of the present invention is not only promising as a high-performance light source required for long-distance optical communication, wavelength-multiplexed optical communication, etc., but also optical information processing and recording and optical applications. In the field of measurement, light source of high-speed optical phenomenon, etc., it is highly possible to be used as a high-performance small light source that can replace the conventionally used gas laser device or solid-state laser device.

[Brief description of drawings]

FIG. 1 is a perspective view showing a semiconductor distributed feedback laser device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a semiconductor distributed feedback laser device according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a semiconductor distributed feedback laser device according to a third embodiment of the present invention.

[Explanation of symbols]

 1, 21 Substrate 2, 22 Buffer layer 3, 8, 23, 28 Cladding layer 4, 24 Active layer 5, 25 Buffer layer 6 Current blocking layer 7, 27 Diffraction grating 9, 29 Contact layer 10, 30 Insulating layer 11, 12 , 31, 32 Electrode layer 36 Semiconductor layer 37 Ion implantation region

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Rao 2-11-13 Nakamachi, Musashino City, Tokyo Inside photometer measurement technology development corporation (72) Inventor Takeshi Inoue 2-11-13 Nakamachi, Musashino City, Tokyo Photometer Measurement Technology Development Co., Ltd. (72) Inventor Haruo Hosomatsu 2-11-13 Nakamachi, Musashino-shi, Tokyo Photometer Measurement Technology Development Co., Ltd. (72) Hideto Iwaoka 2 Nakamachi, Musashino-shi, Tokyo 11th-13th Optical Meter Measurement Technology Development Co., Ltd.

Claims (5)

[Claims] 1. A semiconductor distributed feedback laser device comprising an active layer for generating stimulated emission light, and a periodic structure arranged along the active layer for performing distributed light feedback on the stimulated emission light generated by the active layer. 2. The semiconductor distributed feedback laser device according to claim 1, wherein the periodic structure is a structure whose conductivity periodically changes along a laser optical axis direction parallel to the active layer. 2. A semiconductor device having two sets of semiconductor layers different in conductivity from each other with an active layer sandwiched therebetween, and the periodic structure having a conductivity different from that of the semiconductor layer embedded in at least one semiconductor layer of the two sets of semiconductor layers. 2. The semiconductor distributed feedback laser device according to claim 1, which includes the diffraction grating. 3. The diffraction grating according to claim 2, wherein the diffraction grating is formed in a periodic uneven shape along the laser optical axis direction, and the thickness of the active layer is also periodically changed corresponding to the uneven shape. Semiconductor distributed feedback laser device. 4. The semiconductor distributed feedback laser device according to claim 2, wherein the diffraction grating has a shape in which layers having different conductivity are periodically cut. 5. The semiconductor distributed feedback laser device according to claim 2, wherein the conductivity type of the diffraction grating is different from the conductivity type of the semiconductor layer in which the diffraction grating is embedded.