JPH08139403A - Semiconductor laser device - Google Patents

Abstract

PURPOSE: To obtain a semiconductor laser device of a distributed feedback type wherein a diffraction grating is easily worked, single mode oscillation is stable, and threshold current is low. CONSTITUTION: An N-type InGaAsP guide layer 2 and a nondoped InGaAs/ InGaAsP multiquantum well active layer 3 are formed in order on an N-type InP substrate 1 by an MOCVD method. A secondary phase shift type diffraction grating 71 is formed on the surface of an active layer 3 by a photomask self- interference method, and turns to a secondary diffraction grating having perturvation of refractive index and gain. Further a P-type InGaAsP guide layer 4, a P-type InP clad layer 5 and a P-type InGaAsP contact layer 6 are grown in order by the MOCVD method. After a mesa structure is formed and buried growth is performed, a P-side electrode 8 and an N-side electrode 9 are formed. After that, a laser resonator of 0.4mm is formed by cleavage.

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, and more particularly to a semiconductor laser device which stably oscillates in a vertical single mode.

[0002]

2. Description of the Related Art Conventionally, as this type of semiconductor laser device, a distributed feedback semiconductor laser operating in a longitudinal single mode is known. A distributed feedback semiconductor laser has a diffraction grating formed along an optical waveguide, and by combining a forward wave and a backward wave in the waveguide to obtain optical feedback, a wavelength selectivity is provided for a threshold gain. It is a semiconductor laser which has a vertical single mode. As a conventional example of oscillating in the visible region of such a semiconductor laser device, for example,
1 between the p-guide layer and the p-cladding layer above the active region
Distributed feedback type AlGaAs / Ga having the following diffraction grating
The structure of the As laser is described in Applied Physics Letter, 51 (2), pp. 63-65, 1987, July 1
3rd (Appl. Phys. Lett. 51 (2), pp.63-65, 13 July 19
87).

[0003]

However, in order to manufacture a distributed feedback semiconductor laser that oscillates in the visible region using the above-described first-order diffraction grating, fine first-order diffraction having a pitch of about 100 nm is required. Although it is necessary to form a grating, it was difficult to directly form a first-order diffraction grating due to the limitation of microfabrication. Therefore, in the conventional example, first, a secondary diffraction grating having a double pitch and easy to manufacture is formed by an interference exposure method, and then a photoresist is further applied,
By developing without exposing this time, only the tip of the secondary diffraction grating is exposed, and the tip is removed by chemical etching using the photoresist left in the recess of the secondary diffraction grating as a mask to remove the primary It was realized by the complicated method of obtaining the diffraction grating of.

On the other hand, if an attempt is made to realize a distributed feedback semiconductor laser that oscillates in the visible region by using not only the first-order diffraction grating but the easily processed second-order and higher-order diffraction gratings.
The second-order diffraction grating has a problem in that the effective coupling coefficient is reduced, and since there is a radiation mode perpendicular to the cavity direction, it is more difficult than the case of using the first-order diffraction grating. There is also a problem that the threshold gain increases and the threshold current increases. The second-order diffraction grating is a diffraction grating in which the perturbation period is second-order with respect to the oscillation wavelength, that is, the relation of effective refractive index × perturbation period is established.

Therefore, an object of the present invention is to make the processing easy.
(EN) Provided is a semiconductor laser device having a low threshold current, in which the coupling coefficient can be made approximately equal to that in the case of using a first-order diffraction grating and stable oscillation in a longitudinal single mode can be achieved by using the following diffraction grating is there.

[0006]

In order to achieve the above object, a semiconductor laser device according to the present invention is a distributed feedback type semiconductor laser device having an active layer and a diffraction grating incorporated therein. A region in which the perturbation of the refractive index and the perturbation of the gain are simultaneously present in the cavity direction, the period of each perturbation is quadratic with respect to the oscillation wavelength, and the phase of the period of each perturbation is discontinuous. That is, as shown in FIG. 1, a region where the phase period of the diffraction grating 71 is inverted in the center of the resonator, or a region where the perturbation period is non-uniform,
That is, it is characterized by including a phase adjustment region having a short period near the center of the resonator of the diffraction grating 72 as shown in FIG.

In the semiconductor laser device, it is preferable that the oscillation longitudinal mode selected by the perturbation of the refractive index and the oscillation longitudinal mode selected by the perturbation of the gain match. In this case, the perturbation of the refractive index and the perturbation of the gain may be configured by periodically changing the thickness of the active layer in the cavity direction.

The semiconductor laser device according to the present invention is
In a distributed feedback semiconductor laser device having an active layer and a diffraction grating incorporated therein, the diffraction grating has a periodic gain perturbation in the cavity direction, and the period of the gain perturbation is relative to an oscillation wavelength. The loss layer 7 is a second-order region in which the phase of the gain perturbation is discontinuous, that is, near the center of the resonator of the diffraction grating 73 as shown in FIG.
A structure including a region in which the cycle of 0 is inverted can be employed. In this case, the gain perturbation may be configured by periodically changing the loss layer provided in the resonator direction.

Further, in any of the above semiconductor laser devices, it is preferable that the active layer is composed of a multiple quantum well layer. Further, in any of the semiconductor laser devices described above, the diffraction grating may be formed on the upper surface of the active layer or may be formed on the lower surface of the active layer. Furthermore, it is preferable that both end faces of the resonator be coated with a non-reflective coating.

[0010]

According to the semiconductor laser device of the present invention, in a distributed feedback semiconductor laser device having a diffraction grating in the cavity direction, a periodic gain perturbation and a refractive index perturbation are simultaneously provided, and the perturbation period is Stable vertical single-mode oscillation and low threshold by including a region that is quadratic with respect to the oscillation wavelength and in which the phase of the perturbation period is discontinuous or the period is non-uniform The current can be realized at the same time.

The operating principle of such a semiconductor laser device according to the present invention will be described with reference to FIG. FIG. 8 is a diagram schematically showing the characteristics of a standing wave (solid line), gain (oblique line), and refractive index (dashed line) in the cavity direction of the semiconductor laser device. The semiconductor laser device according to the present invention is configured such that both the refractive index diffraction grating and the gain diffraction grating are simultaneously present in the active layer sandwiched by the optical guide layers, and the phases of the respective diffraction gratings are inverted at the same position A. Has been done. In the case where such a refractive index diffraction grating and a gain diffraction grating are present at the same time, the standing wave shown by the solid line is selected by the secondary refractive index diffraction grating. The antinodes of this standing wave alternate between the high-gain area (hatched area) and the low-gain area (area between the hatched areas)
Therefore, the longitudinal mode corresponding to this standing wave is stably oscillated by the gain diffraction grating, and the threshold gain is reduced.
Therefore, the semiconductor laser device according to the present invention has the same coupling coefficient as that of the distributed feedback semiconductor laser using the first-order diffraction grating, and therefore the threshold value can be the same or lower. is there.

According to the semiconductor laser device of the present invention, the distributed feedback semiconductor laser device having the diffraction grating in the cavity direction has only periodic gain perturbation,
This gain perturbation period is the second order with respect to the oscillation wavelength, and the phase shift type diffraction grating in which the phase of the perturbation period is inverted in the center of the resonator is used to obtain only the first-order refractive index diffraction grating. It is possible to obtain a longitudinal single mode oscillation and a low threshold current that are stable to the same extent as in the case of using, and the processing becomes easy because of the second-order diffraction grating.

The active layer is composed of multiple quantum well layers, and the thickness of the active layer on the upper or lower surface of the active layer is periodically changed in the resonator direction, or the resonator near the upper or lower surface of the active layer. By providing a periodic loss layer in the direction, a diffraction grating having gain perturbation can be formed.

Furthermore, by applying antireflection coating to both end faces of the resonator, the influence of the end face reflection is eliminated, the yield in the single mode is increased, and the reflected light from the outside is also strong.

[0015]

Embodiments of the semiconductor laser device according to the present invention will be described in detail below with reference to the accompanying drawings. <Embodiment 1> FIG. 1 is a schematic view of a main part showing an embodiment of a semiconductor laser device according to the present invention, which is a sectional view of a laser resonator in an axial direction. In FIG. 1, reference numeral 1 indicates an n-type InP substrate, and n is formed on the surface of the n-type InP substrate 1.
Type InGaAsP guide layer 2 (thickness 200 nm, photoluminescence wavelength 1250 nm), non-doped InG
aAs / InGaAsP multiple quantum well active layer 3 (InG
aAs well layer 6 nm, InGaAsP barrier layer 10 nm,
Number of wells 5, photoluminescence wavelength 1550 nm)
Are sequentially grown by a metal organic chemical vapor deposition (MOCVD) method. Next, a second-order phase shift diffraction grating 71 having a period of 480 nm is formed on the surface of the multiple quantum well active layer 3 by the photomask self-interference method. The phase of the diffraction grating 71 is inverted at the center of the laser resonator. The depth of the diffraction grating 71 is 200 nm. With this structure, the refractive index and the gain perturbation are simultaneously formed in the cavity direction. That is, the structure is such that the second-order refractive index diffraction grating and the second-order gain diffraction grating simultaneously exist.

Next, again by the metal organic chemical vapor deposition method, p
A type InGaAsP guide layer 4 (thickness 400 nm, photoluminescence wavelength 1250 nm), a p-type InP clad layer 5 (thickness 1500 nm), and a p-type InGaAsP contact layer 6 (thickness 200 nm, photoluminescence wavelength 1250 nm) are sequentially grown in multiple layers.

Next, the surface is etched using SiO ₂ as a mask to form a mesa structure (not shown), and the portion removed by the above-mentioned etching is embedded and grown by selective growth. The side electrode 8 and the n-side electrode 9 were formed and cleaved to form a 0.4 mm laser resonator.

The characteristics of the semiconductor laser device of the present embodiment thus formed are as follows: oscillation wavelength is 1550 nm, threshold current is 10 mA, and slope efficiency, which represents the slope of current-optical output characteristics in an oscillating state, is 0.25 W. Was / A. Also,
It was possible to stably oscillate in the vertical single mode not only when the DC bias was applied, but also when the high speed modulation was performed. The threshold current in the case of a semiconductor laser device having a conventional structure formed by using a first-order or second-order diffraction grating is about 10 mA (first-order diffraction grating) or 20 mA (second-order diffraction grating). The value of the threshold current of 10 mA obtained by the semiconductor laser device of the present embodiment is smaller than that of the semiconductor laser device of the conventional structure using the second-order diffraction grating, which is smaller than that of the conventional structure using the first-order diffraction grating. The same level as in the case of the semiconductor laser device.

<Embodiment 2> FIG. 2 is a schematic view of a main part showing another embodiment of the semiconductor laser device according to the present invention, and is a sectional view in the axial direction of the laser resonator. In FIG. 2, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted for convenience of description. That is, in the present embodiment, the structure of the secondary diffraction grating 72 is different from that of the diffraction grating 71 of FIG. 1, and a phase adjustment region in which the period of the diffraction grating is short is provided in a region having a length of 0.1 mm near the center of the resonator. Is provided. The period of the diffraction grating in the phase adjustment region is 478.85 nm, and the period in the regions at both ends of the resonator is 480 nm. By providing such a phase adjustment region, effective phase inversion is realized.
Of course, the diffraction grating 72 of the present embodiment also has the same structure as that of the first embodiment.
It goes without saying that the structure is such that the next refractive index diffraction grating and the second-order gain diffraction grating exist at the same time. The oscillation wavelength of the semiconductor laser device of this example is 1550 nm, the threshold current is 10 mA, and the slope efficiency is 0.25 W / A, and it is stable in the vertical single mode both during DC bias and high speed modulation. It was possible to obtain a good oscillation.

<Embodiment 3> FIG. 3 is a schematic view of a main portion showing still another embodiment of the semiconductor laser device according to the present invention, which is an axial sectional view of a laser resonator. In FIG. 3, reference numeral 1 indicates an n-type InP substrate.
On the surface of the P substrate 1, the n-type InGaAsP guide layer 2 (thickness 200 nm, photoluminescence wavelength 1250 n
m) is grown by metalorganic vapor phase epitaxy. Next, a second-order phase shift diffraction grating 71a having a period of 480 nm is formed on the surface of the n-type InGaAsP guide layer 2 by the photomask self-interference method. The phase of the diffraction grating 71a is inverted at the center of the laser resonator. In addition, the diffraction grating 71
The depth of a is 200 nm.

Next, the non-doped InGaAsP active layer 3
a (thickness 200 nm, photoluminescence wavelength 155
0 nm), p-type InGaAsP guide layer 4a (thickness 20
0 nm, photoluminescence wavelength 1250 nm), p
Type InP clad layer 5 (thickness 1500 nm), p type In
The GaAsP contact layer 6 (thickness: 200 nm, photoluminescence wavelength: 1250 nm) is sequentially grown in multiple layers by a metal organic chemical vapor deposition method.

Next, the surface is etched by using SiO ₂ as a mask to form a mesa structure (not shown), and the portion removed by the above-mentioned etching is embedded and grown by selective growth. The side electrode 8 and the n-side electrode 9 were formed and cleaved to form a 0.4 mm laser resonator.

In this embodiment, the non-doped InGaA is used.
When the sP active layer 3a is formed, a structure in which a perturbation of the refractive index and the gain is formed in the cavity direction, that is, a structure in which a second-order refractive index diffraction grating and a second-order gain diffraction grating exist simultaneously.

The characteristics of the semiconductor laser device of this embodiment formed in this manner were that the oscillation wavelength was 1550 nm, the threshold current was 10 mA, and the slope efficiency was 0.25 W / A. Further, it was possible to stably oscillate in the vertical single mode not only during DC bias but also during high-speed modulation.

<Embodiment 4> FIG. 4 is a schematic view of a main part showing still another embodiment of the semiconductor laser device according to the present invention, which is an axial sectional view of the laser resonator. In FIG. 4, the same components as those of the third embodiment shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted for convenience of description. That is, in the present embodiment, the structure of the secondary diffraction grating 72a is different from that of the diffraction grating 71a of FIG. 3, and in the region of 0.1 mm length near the center of the resonator, the phase adjustment region where the period of the diffraction grating is short. Is provided. The period of the diffraction grating in the phase adjustment region is 478.85 nm, and the period in the regions at both ends of the resonator is 480 nm. By providing such a phase adjustment region, effective phase inversion is realized.

Needless to say, the diffraction grating 72a of this embodiment has a structure in which a second-order refractive index diffraction grating and a second-order gain diffraction grating are present at the same time as in the third embodiment.
The oscillation wavelength of the semiconductor laser device of this embodiment is 155
0 nm, threshold current 10 mA, slope efficiency 0.
It was 25 W / A, and stable oscillation in a single longitudinal mode could be obtained at both DC bias and high speed modulation.

<Embodiment 5> FIG. 5 is a schematic view of a main portion showing still another embodiment of the semiconductor laser device according to the present invention, which is an axial sectional view of a laser resonator. In FIG. 5, reference numeral 1 indicates an n-type InP substrate.
The n-type InGaAsP guide layer 2a is formed on the surface of the P substrate 1.
(Thickness 200 nm, photoluminescence wavelength 1250
nm), p-type InGaAsP loss layer 70 (thickness 200 n
m, photoluminescence wavelength 1650 nm) are sequentially grown by a metal organic chemical vapor deposition method.

Next, a second-order phase shift diffraction grating 73 having a period of 480 nm is formed on the surface of the p-type InGaAsP loss layer 70 by the photomask self-interference method. The phase of the diffraction grating 73 is inverted at the center of the laser resonator (the position shown by arrow B). By forming the diffraction grating 73 in this manner, a structure in which a second-order gain diffraction grating exists in the resonator direction is obtained.

Next, the n-type InGaAsP guide layer 2b
(Thickness 200 nm, photoluminescence wavelength 1250
nm), non-doped InGaAs / InGaAsP multiple quantum well active layer 3 (InGaAs well layer 6 nm, InG)
aAsP barrier layer 10 nm, number of wells 5, photoluminescence wavelength 1550 nm), p-type InGaAsP guide layer 4a (thickness 200 nm, photoluminescence wavelength 12)
50 nm), p-type InP clad layer 5 (thickness 1500 n
m), p-type InGaAsP contact layer 6 (thickness 200
nm, photoluminescence wavelength 1250 nm) is sequentially grown in multiple layers.

Next, the surface is etched using SiO ₂ as a mask to form a mesa structure (not shown), and the portion removed by the above-mentioned etching is embedded and grown by selective growth. The side electrode 8 and the n-side electrode 9 were formed and cleaved to form a 0.4 mm laser resonator.

The semiconductor laser device of the present embodiment thus formed has the characteristics of an oscillation wavelength of 1550 nm, a threshold current of 10 mA, and a slope efficiency of 0.25 W / A, and has characteristics of DC bias and high speed modulation. Both of them oscillated stably in the vertical single mode.

<Embodiment 6> FIG. 6 is a schematic view of a main portion showing still another embodiment of the semiconductor laser device according to the present invention, which is an axial sectional view of a laser resonator. In FIG. 6, reference numeral 1 indicates an n-type InP substrate.
On the surface of the P substrate 1, the n-type InGaAsP guide layer 2 (thickness 200 nm, photoluminescence wavelength 1250 n
m), non-doped InGaAs / InGaAsP multiple quantum well active layer 3 (InGaAs well layer 6 nm, InGa
AsP barrier layer 10 nm, number of wells 5, photoluminescence wavelength 1550 nm), p-type InGaAsP guide layer 4
a (thickness 200 nm, photoluminescence wavelength 125
0 nm), n-type InGaAsP loss layer 70a (thickness: 20 nm)
0 nm, photoluminescence wavelength 1650 nm),
Sequential growth is performed by the metal organic chemical vapor deposition method.

Next, a period of 480 nm is formed on the surface of the n-type InGaAsP loss layer 70a by the photomask self-interference method.
The second-order phase shift diffraction grating 73a is formed. The phase of the diffraction grating 73a is inverted at the center of the laser resonator (the position shown by arrow B). In this way, the diffraction grating 73a
Is formed, a structure in which a second-order gain diffraction grating exists in the resonator direction is formed.

Next, the p-type InGaAsP guide layer 4b (thickness 400 nm, photoluminescence wavelength 1250 nm), the p-type InP clad layer 5 (thickness 1500 nm), and the p-type InGaAsP contact layer 6 ( A thickness of 200 nm and a photoluminescence wavelength of 1250 nm) are sequentially grown in multiple layers.

Next, the surface is etched using SiO ₂ as a mask to form a mesa structure (not shown), and the portion removed by the above-mentioned etching is embedded and grown by selective growth. The side electrode 8 and the n-side electrode 9 were formed and cleaved to form a 0.4 mm laser resonator.

The characteristics of the semiconductor laser device of this embodiment having the above-mentioned structure were as follows: the oscillation wavelength was 1550 nm, the threshold current was 10 mA, and the slope efficiency was 0.25 W / A. Further, it was possible to stably oscillate in the vertical single mode not only during DC bias but also during high-speed modulation. Further, in the present embodiment, the flat p-type In which the active layer 3 is not processed is formed.
Since the active layer 3 is formed on the GaAsP guide layer 4a, the crystallinity of the active layer 3 is better than that in the fifth embodiment, and the optical loss is small. Therefore, it is possible to obtain more stable vertical single-mode oscillation. There is.

<Embodiment 7> FIG. 7 is a schematic view of a main portion showing still another embodiment of the semiconductor laser device according to the present invention, which is an axial sectional view of a laser resonator. In FIG. 7, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted for convenience of description. That is, this embodiment is different in that the antireflection coating 10 is applied to both end faces of the laser resonator.
In a phase shift type distributed feedback semiconductor laser, ideally, there is no end face reflection, but in the structures of Examples 1 to 6, reflection of about 30% may actually occur. On the other hand, in the semiconductor laser device of the present embodiment, the end facet reflection is eliminated by applying the antireflection coating 10 on both end faces, so that the laser oscillation is not affected by the end facet reflection, the single mode yield is increased, and the external There is an effect that it becomes strong against the reflected return light from.

The oscillation wavelength of the semiconductor laser device of this example was 1550 nm, the threshold current was 10 mA, and the slope efficiency was 0.25 W / A. Further, stable oscillation was achieved in the vertical single mode not only during DC bias but also during high speed modulation. Needless to say, the antireflection coating 10 of this embodiment may be applied to both end faces of the structure shown in FIGS.

<Embodiment 8> FIG. 9 is a schematic view of a main part showing still another embodiment of the semiconductor laser device according to the present invention, which is a sectional view in the axial direction of the laser resonator. In FIG. 9, reference numeral 21 indicates an n-type GaAs substrate, and an n-type AlGaAs guide layer 22 (thickness 200 nm, photoluminescence wavelength 65) is formed on the surface of the n-type GaAs substrate 21.
0 nm) and a non-doped AlGaAs active layer 23 are sequentially grown by a metal organic chemical vapor deposition (MOCVD) method. Next, on the surface of the active layer 23 by photomask self-interference method,
A secondary phase shift diffraction grating 74 having a period of 200 nm is formed. The phase of the diffraction grating 74 is inverted at the center of the laser resonator. The depth of the diffraction grating 74 is 20
It is 0 nm. With this structure, the refractive index and the gain perturbation are simultaneously formed in the cavity direction. That is, the structure is such that the second-order refractive index diffraction grating and the second-order gain diffraction grating simultaneously exist.

Next, again by the metal organic chemical vapor deposition method, p
-Type AlGaAs guide layer 24 (thickness 400 nm, photoluminescence wavelength 650 nm), p-type AlGaAs clad layer 25 (thickness 1500 nm), p-type AlGaAs
The contact layer 26 (thickness 200 nm, photoluminescence wavelength 650 nm) is sequentially grown in multiple layers.

Next, the surface is etched by using SiO ₂ as a mask to form a mesa structure (not shown), and the portion removed by the above-mentioned etching is embedded and grown by selective growth. The side electrode 8 and the n-side electrode 9 were formed and cleaved to form a 0.4 mm laser resonator.

The characteristics of the semiconductor laser device of the present embodiment formed in this way are those of laser light in the visible light region with an oscillation wavelength of 750 nm, a threshold current of 10 mA, and current-light output characteristics in an oscillation state. The slope efficiency representing the slope is 0.
It was 25 W / A. Further, it was possible to stably oscillate in the vertical single mode not only during DC bias but also during high-speed modulation.

The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and for example, a semiconductor laser device formed of a material system including a GaAs or GaN system or an embedded semiconductor device. The present invention can be applied to a semiconductor laser device having an embedded structure or a case where the lattice constant of the multilayer growth film is different from the lattice constant of the substrate, and various design changes can be made without departing from the spirit of the present invention. Of course.

[0044]

As is apparent from the above-described embodiments, according to the present invention, in a distributed feedback semiconductor laser device having a diffraction grating incorporated therein, the diffraction grating has periodic gain perturbations. , Or the periodic perturbation of the refractive index and the periodic perturbation of the gain exist at the same time, and the phase of the perturbation period is discontinuous or the region of the perturbation period is nonuniform. As a result, even if a second-order diffraction grating, which is easier to process than the first-order diffraction grating, is used, a reduction in the coupling coefficient is suppressed, stable vertical single-mode oscillation is possible, and a semiconductor with a low threshold current is used. A laser device can be realized. Therefore, even if a first-order diffraction grating, such as a semiconductor laser in the visible light region, is difficult to make due to the limitation of fine processing, a stable oscillation can be obtained with a low threshold current by the second-order diffraction grating. it can.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a semiconductor laser device according to the present invention.

FIG. 2 is a cross-sectional view of a main part showing another embodiment of the semiconductor laser device according to the present invention.

FIG. 3 is a cross-sectional view of a main part showing another embodiment of the semiconductor laser device according to the present invention.

FIG. 4 is a cross-sectional view of a main part showing still another embodiment of the semiconductor laser device according to the present invention.

FIG. 5 is a cross-sectional view of an essential part showing still another embodiment of the semiconductor laser device according to the present invention.

FIG. 6 is a cross-sectional view of a main part showing another embodiment of the semiconductor laser device according to the present invention.

FIG. 7 is a cross-sectional view of an essential part showing still another embodiment of the semiconductor laser device according to the present invention.

FIG. 8 is a diagram illustrating the principle of a semiconductor laser device according to the present invention.

FIG. 9 is a cross-sectional view of a main part showing another embodiment of the semiconductor laser device according to the present invention.

[Explanation of symbols]

1 ... n-type InP substrate, 2, 2a, 2b ... n-type InGaAsP guide layer, 3 ... non-doped InGaAs / InGaAsP multiple quantum well active layer, 3a ... non-doped InGaAsP active layer, 4, 4a, 4b ... p-type InGaAsP guide layer, 5 ... p-type InP clad layer, 6 ... p-type InGaAsP contact layer, 8 ... p-side electrode, 9 ... n-side electrode, 10 ... non-reflective coating, 21 ... n-type GaAs substrate, 22 ... n-type AlGaAs guide layer, 23 ... non-doped AlGaAs active layer, 24 ... p-type AlGaAs guide layer, 25 ... p-type AlGaAs cladding layer, 26 ... p-type AlGaAs contact layer, 70 ... p-type InGaAsP loss layer, 70a ... n-type InGaAsP loss layer, 71, 71a ... Diffraction grating, 72, 72a ... Diffraction grating, 73, 73a ... Diffraction grating, 7 ... diffraction grating.

Claims (10)

[Claims] 1. A distributed feedback semiconductor laser device having an active layer and a diffraction grating incorporated therein, wherein the diffraction grating comprises:
At the same time, a perturbation of the refractive index and a perturbation of the gain that are periodic in the resonator direction are provided, and the period of each perturbation is 2 with respect to the oscillation wavelength.
A semiconductor laser device including the following region including a discontinuous phase of the cycle of each perturbation. 2. A distributed feedback semiconductor laser device having an active layer and a diffraction grating incorporated therein, wherein the diffraction grating comprises:
At the same time, a perturbation of the refractive index and a perturbation of the gain that are periodic in the resonator direction are provided, and the period of each perturbation is 2 with respect to the oscillation wavelength.
A semiconductor laser device including the following region including a non-uniform period of each perturbation. 3. The semiconductor laser device according to claim 1, wherein an oscillation longitudinal mode selected by the perturbation of the refractive index and an oscillation longitudinal mode selected by the perturbation of the gain coincide with each other. 4. The semiconductor laser device according to claim 1, wherein the perturbation of the refractive index and the perturbation of the gain are formed by periodically changing the thickness of the active layer in the cavity direction. 5. A distributed feedback type semiconductor laser device having an active layer and a diffraction grating incorporated therein, wherein the diffraction grating comprises:
A region having a periodic gain perturbation in the resonator direction, the period of the gain perturbation being quadratic with respect to the oscillation wavelength, and the phase of the period of the gain perturbation being discontinuous; A semiconductor laser device. 6. The semiconductor laser device according to claim 5, wherein the gain perturbation is formed by periodically changing a loss layer provided in a cavity direction. 7. The semiconductor laser device according to claim 4, wherein the active layer is a multiple quantum well layer. 8. The semiconductor laser device according to claim 4, wherein the diffraction grating is provided on an upper surface of an active layer. 9. The semiconductor laser device according to claim 4, wherein the diffraction grating is provided on the lower surface of the active layer. 10. The semiconductor laser device according to claim 1, wherein both end faces of the resonator are provided with antireflection coating.