JPH07249829A - Distributed feedback semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a distributed feedback semiconductor laser which is operated stably over a wide temperature range by a method wherein an active layer is formed of at least two quantum well layers and the quantum-level light-emitting wavelength of the quantum-well layer on one side is made different from the quantum-level light- emitting wavelength of the quantum-well layer on the other side. CONSTITUTION:A p-InP clad layer 2 is grown on a p-InP substrate 1, and a diffraction grating 3 is then formed. After that, a p-InGaAsP light guide layer 4, an InGaAsP-based strain multiple quantum-well active layer 5 and an n-InP clad layer 6 are grown. At this time, the difference in a quantum-level light-emitting wavelength between a maximum-film-thickness quantum-well layer 15a and a minimum-film-thickness quantum-well layer 15e out of strain quantum-well layers 15a to 15e for the InGaASP- based strain multiple quantum-well layer 5 is set at 30nm. Then, when the film thickness, the mixed-crystal composition strain amount or the strain amount of the individual quantum-well layers 15a to 15e is changed, the quantum-level light-emitting wavelength of the individual quantum-well layers 15a to 15e can be changed. Consequently, the distributed feedback semiconductor laser can be operated stably over a wide temperature range, e.g. from -40 to +85 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed feedback semiconductor laser, and particularly to a wide temperature range, for example, -40 ° C to +85.
The present invention relates to a distributed feedback semiconductor laser for optical communication, which operates stably at ℃.

[0002]

2. Description of the Related Art In order to construct a subscriber optical communication system, it is extremely important to reduce the power consumption, size, and price of an optical transmission device. In order to realize this, it is essential to develop a semiconductor laser that does not require temperature control in a wide environmental temperature range, for example, -40 ° C to + 85 ° C. In particular, a wide temperature range operation of a distributed feedback (DFB) laser that oscillates in a single longitudinal mode is desired. On the other hand, the high temperature low current operation of the 1.3 μm band DFB laser in which the compressive strain MQW (multiple quantum well) structure is introduced into the active layer is
Proceedings of the 27th JSAP Academic Lecture Meeting 27p-H-12
(September 1993).

[0003]

However, in the above-mentioned conventional technique, the operation is limited to the range of + 5 ° C to + 80 ° C, which is caused by the following problems.

Generally, the oscillation wavelength λLD of a DFB laser is
It is expressed by the following equation using the refractive index n of the medium and the period Λ of the diffraction grating.

[0005]

ΛLD = 2nΛ (1) On the other hand, the peak wavelength λg of the optical gain of the quantum well active layer is determined by the quantum well structure such as the quantum well film thickness and the quantum well composition. Therefore, a detuning wavelength ΔG represented by the following equation exists between the oscillation wavelength λLD of the DFB laser and the peak wavelength λg of the optical gain.

[0006]

## EQU00002 ## .DELTA.G = .lambda.LD-.lambda.g (2) Therefore, generally, .DELTA.G is set to be substantially zero at the operating temperature. However, 1.3 μm band,
In the long wavelength band semiconductor laser such as 1.55 μm band,
Since the temperature dependence dλLD / dT of the laser oscillation wavelength λLD is about 0.1 nm / ° C and the temperature dependence dλg / dT of the optical gain peak wavelength λg is about 0.4 nm / ° C, the detuning wavelength ΔG depends on the temperature. Property dΔG / dT is about -0.3 nm
Take a finite value with / ° C. Therefore, when considering a wide environmental temperature range, for example, 125 ° C. of −40 ° C. to + 85 ° C., ΔG changes near 40 nm in the operating temperature range.

FIG. 2 is a schematic diagram summarizing the above points by taking a 1.3 μm band DFB laser as an example, and the problems of the prior art will be described using this. First, FIG. 2 (a)
Then, at room temperature (25 ° C.), when ΔG is set to 0, ΔG at 85 ° C. becomes −18 nm, and the laser oscillation wavelength and the optical gain peak wavelength deviate from each other. The threshold current increases significantly. As a result, the efficiency at the time of operation at 85 ° C. is low, and not only the initial characteristics but also the operating current increases, leading to deterioration in the reliability of the element. Therefore, FIG. 2B shows a case in which ΔG is set to 0 at 85 ° C. operation. In this case, there is no deterioration of the threshold current at 85 ° C, while ΔG at -40 ° C is +
38 nm, which is far from the optical gain bandwidth, making DFB operation difficult, so-called FP (Fabr
This results in multi-longitudinal mode oscillation including the y-Perot) mode.

As described above, in the conventional DFB laser,
Even if the strained quantum well structure is used to reduce the threshold, the operation in a wide environmental temperature range of −40 ° C. to + 85 ° C. cannot be realized.

The object of the present invention is to provide a wide temperature range, for example:
An object of the present invention is to provide a distributed feedback semiconductor laser for optical communication, which operates stably at 40 ° C to + 85 ° C.

[0010]

In order to achieve the above object, according to the present invention, the quantum level emission wavelength of at least one quantum well layer of a multiple quantum well active layer is the quantum level emission of another quantum well layer. Different from the wavelength, the quantum well film thickness of at least one quantum well layer is different from the quantum well film thickness of other quantum well layers, and the mixed crystal composition forming at least one quantum well layer is different from that of other quantum well layers. That the strain amount of at least one strain quantum well layer of the multiple quantum well structure formed from the strain quantum well layer is different from that of another strain quantum well layer. It is achieved by either. In particular, the difference between the maximum value and the minimum value of the quantum level emission wavelength of the quantum well layer and the strained quantum well layer is 15 to 45 nm,
The difference between the maximum quantum well thickness and the minimum quantum well thickness of the quantum well layer and the strained quantum well layer is 1.0 to 3.5 nm, and the maximum quantum well thickness of the quantum well layer and the strained quantum well layer is 6 nm,
The minimum quantum well film thickness is 4 nm, the quantum level emission wavelength is longer on the hole injection side than on the electron injection side, the number of wells is 4 to 8, and the semiconductor substrate is p-type. I
In the nP substrate, the active layer is formed in a mesa stripe shape, and the side surface of the mesa stripe active region is p / n /
Embedded with a p-type current blocking layer, the detuning wavelength ΔG at room temperature has a value of −10 to +10 nm, and κL
The value of (κ: the coupling constant of light due to the perturbation of the refractive index in the axial direction of the resonator, κ, L: the resonator length) is 0.8 to 1.5, the quantum well layer, and the strained quantum well layer. Is the InGaAsP layer,
Alternatively, it is achieved by using an InGaAlAs layer.

[0011]

The operation of the present invention will be described below with reference to FIG. FIG. 10A shows an example in which the quantum well film thickness of each quantum well layer is changed in order to change the quantum level emission wavelength between the quantum well layers. The quantum well film thickness increases in the order of quantum well →→, and accordingly, the quantum level emission wavelength becomes a long wavelength in the order of quantum well →→ as shown in FIG. At 25 ° C., the emission intensity from the quantum well is strongest as shown in FIG. on the other hand,
At 85 ° C., the light emission from the quantum well shifts to the long wavelength, but at high temperature, the Fermi-Dirac distribution is blurred, so the light emission from the quantum well on the high energy side, that is, the short wavelength side increases, The light emitted from the well is the strongest. As a result, as shown in FIG. 3B, the temperature dependence of the emission peak wavelength, that is, the optical gain peak wavelength λg when the temperature is raised from 25 ° C. to 85 ° C. becomes extremely small. At this time, the temperature dependence dλg / dT of the optical gain peak wavelength λg is as small as about 0.1 to 0.2 nm / ° C (conventional: 0.4 nm / ° C), and as a result, the temperature dependence of the detuning wavelength ΔG. dΔG / dT is about 0.0 to −0.
It could be suppressed to 1 nm / ° C., which is 1/3 or less of the conventional value. As a result, as shown in FIG. 3C, for example, even when ΔG is set to 0 at room temperature (25 ° C.), ΔG at 85 ° C. and −40 ° C. is −6 nm and +6 nm, respectively. Becomes extremely small, and the detuning wavelength Δ
The deterioration of the characteristics of the DFB laser due to the temperature dependence of G can be suppressed to a small level, and as a result, a wide temperature range, for example, −
It was possible to realize a distributed feedback semiconductor laser for optical communication, which operates stably at 40 ° C to + 85 ° C. Even if the quantum level emission wavelength of each quantum well layer is changed by changing the mixed crystal composition strain amount of each quantum well layer and changing the strain amount, the temperature dependence dΔG / dT of the detuning wavelength ΔG is exactly the same. Can be suppressed small.

Further, in the present invention, particularly, the difference between the maximum and minimum quantum level emission wavelengths of the quantum well layer and the strained quantum well layer is set to 15 to 45 nm. The difference between the maximum quantum well film thickness and the minimum quantum well film thickness is set to 1.0 to 3.5 nm, the quantum well layer,
By setting the maximum quantum well film thickness of the strained quantum well layer to 6 nm and the minimum quantum well film thickness to 4 nm, the temperature dependence dΔG / dT of the detuning wavelength ΔG is suppressed within the range of 0 to -0.2 nm / ° C. be able to. Further, if the quantum level emission wavelength of the quantum well layer on the side where holes are injected is set to be longer than that on the side where electrons are injected, the effect of injecting holes into the quantum well on the high energy side at high temperature is improved. Since it is accelerated, the temperature dependence dΔG / dT suppressing effect of the detuning wavelength ΔG becomes large.
Further, if the number of wells is set to 4 to 8, oscillation at high temperature becomes easy, and therefore the effect of suppressing dΔG / dT is large. or,
When the semiconductor substrate is a p-type InP substrate and is embedded with a p / n / p-type current block layer, the current constriction effect is large, and oscillation at high temperature is facilitated, so that the dΔG / dT suppression effect is large. Furthermore, the detuning wavelength ΔG at room temperature is -10 to +
If the value of κL is set to 0.8 to 1.5 and oscillation at high temperature is easily maintained by setting to 10 nm, ΔG at + 85 ° C. is −15 n.
Since it becomes m or more, deterioration of characteristics does not occur.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

Example 1 FIG. 1 shows the present invention applied to a 1.3 μm band distributed feedback semiconductor laser on a p-type substrate. As shown in FIGS. 3A and 3B, the p-InP clad layer 2 (carrier concentration ~ 1 × 10 ¹⁸ cm ^-3 , thickness ~) is formed on the p-InP substrate 1 by metalorganic vapor phase epitaxy. 2 μm)
After growing, the diffraction grating 3 was formed. Then, the p-InGaAsP optical guide layer 4, the InGaAsP strained multiple quantum well active layer 5, and the n-InP are formed by metal organic chemical vapor deposition.
Cladding layer 6 (carrier concentration ~1 × 10 ¹⁸ cm- ^3, thickness ～0.4Myuemu) is grown. At this time, the strain quantity of the strained quantum well layers 15a to 15e of the InGaAsP-based strained multiple quantum well active layer 5 is set to about 1.0%, and as shown in the conduction band diagram of FIG. The number of well layers is 5, and the strained quantum well film thickness is p-InGaAsP optical guide layer 4.
From the side closer to 6.0 nm, 5.5 nm,
5.0 nm, 4.5 nm, 4.0 nm, InGa
The film thickness of the AsP barrier layer 16 is 7 nm. At this time, the difference in quantum level emission wavelength from the maximum film thickness quantum well layer 15a and the minimum film thickness quantum well layer 15e is 30 nm. Diffraction grating 3
Has a depth of 15-3.
It was set to 0 nm. Also, the detuning wavelength ΔG is −
The period of the diffraction grating 3 was set to about 202 nm so as to be 10 to +10 nm.

After that, a SiO ₂ film is deposited by the CVD method, and a photolithography process is performed. Then, by using the SiO ₂ film as a mask, wet etching is performed to form a mesa stripe having smooth side surfaces without inflection points. To do. The active layer width is 1.3 to 1.8 μm, and the mesa depth is 2.5 to 3.
It is 7 μm. Next, the side surface of the mesa stripe is p-InP grown by metalorganic vapor phase epitaxy with the SiO ₂ film deposited.
Buried layer 7 (carrier concentration ˜1 × 10 ¹⁸ cm ⁻³ , thickness 0.5)
˜1 μm), n-InP burying layer 8 (carrier concentration ˜2 × 10
¹⁸ cm- ³ , thickness 0.5-1 µm), p-InP buried layer 9 (carrier concentration ~ 2 x 10 ¹⁸ cm- ³ , thickness 1-3 µm), n-
InP layer 10 (carrier concentration: 2 × 10 ¹⁸ cm ⁻³ , thickness:
Embedded at 0.5 μm). The structure embedded as described above has an ideal block layer structure without the nn connection which is a factor of the leak current. Next, after removing the SiO ₂ film, an n-InP flattening layer 11 (carrier concentration: 1.5 × 10 ¹⁸ cm ⁻³ , thickness: 2 μm) and n-InGaAs (P ) A cap layer 12 (carrier concentration> 5 × 10 ¹⁸ cm ⁻³ , thickness ˜0.3 μm) was embedded flatly. In the above metal organic chemical vapor deposition method, n
The type impurities are Si (however, only the cap layer 12 is Se), p
Zn was used as the type impurity. After that, the n-electrode 14 was formed after current confinement was performed with the SiO ₂ film 13, the substrate side was further polished to a total film thickness of about 100 μm, and the p-electrode 17 was formed by vapor deposition to form a device. Then, the resonator length 15
Cleavage to 0 to 400 μm was performed, and a low reflectance film 20 having a reflectance of 1% was applied to the front end face and a high reflectance film 21 having a reflectance of 80% was applied to the rear end face.

In the DFB laser according to this embodiment, the threshold current at room temperature is 5-1 at an oscillation wavelength of 1.30 μm.
0 mA, slop efficiency of 0.45 to 0.60 mW / mA is obtained, and ΔG at room temperature is typically from −10 nm to +
It was in the range of 10 nm. Also, the threshold current at 85 ° C is 15 to 25 mA, and the slop efficiency is 0.35 to 0.45 mW / m.
The element A was obtained with a high yield, and modulation of 600 Mbit / s was sufficiently possible. Further, the DFB oscillation was stable even at -40 ° C, and the sub mode suppression ratio was maintained at 35 to 45 dB in the temperature range of -40 ° C to + 85 ° C.
The amount of change in ΔG in the temperature range of −40 ° C. to + 85 ° C. was about 10 nm, which was extremely small. (Embodiment 2) FIG. 4 shows the present invention applied to a 1.55 μm band distributed feedback semiconductor laser on a p-type substrate. As shown in FIGS. 3A and 3B, the p-InP clad layer 2 (carrier concentration ~ 1 × 10 ¹⁸ cm ^-3 , thickness ~) is formed on the p-InP substrate 1 by metalorganic vapor phase epitaxy. 2 μm), and then an undoped InGaAsP-based strained multiple quantum well active layer 18 and n-InGaAsP optical guide layer 19 (carrier concentration ˜1 × 10 ¹⁸ cm ⁻³ , thickness ˜0.2 μm) are grown.
After that, the diffraction grating 3 is formed, and the n-InP clad layer 6 (carrier concentration: 1 × 10 ¹⁸ c) is formed by a metal organic chemical vapor deposition method.
m ⁻³ , thickness ˜0.4 μm). At this time, the quantum well film thickness of the strained quantum well layers 22a to 22d of the undoped InGaAsP-based strained multiple quantum well active layer 18 was set to 5 nm.
Further, as shown in the band diagram of the conduction band in FIG. 4C, the number of strain quantum well layers is 4, and the strain amount of the strain quantum well layers is from the side close to the p-InP clad layer 2 + 1.5%, + 1.43%, + 1.36%, +1.
It is 29%, and the energy in the conduction band changes with the change of the strain amount. The thickness of the InGaAsP barrier layer 23 is 1
It is 0 nm. At this time, the difference in quantum level emission wavelength from the maximum film thickness quantum well layer 22a and the minimum film thickness quantum well layer 22d is 25 nm. The depth was set to 15 to 30 nm so that κL of the diffraction grating 3 was 0.8 to 1.5. The period of the diffraction grating 3 was set to about 201 nm so that the detuning wavelength ΔG would be −10 to +10 nm at room temperature.

Thereafter, after forming a mesa stripe similar to that in Example 1, the side surface of the mesa stripe is formed on the p-InP burying layer 7 (carrier concentration ˜1 × 1) by a metal organic chemical vapor deposition method.
0 ¹⁸ cm ⁻³ , thickness 0.5 to 1 μm), n-InP buried layer 8
(Carrier concentration ^{~2.5 × 10 1 8 cm- 3,} 0.5~1 thickness
μm), p-InP buried layer 9 (carrier concentration up to 2 × 10 ¹⁸ c
m ⁻³ , thickness 1 to ³ μm), and n-InP layer 10 (carrier concentration to 2 × 10 ¹⁸ cm ⁻³ , thickness to 0.3 μm).
Next, after removing the SiO ₂ film, the n-InP flattening layer 11 (carrier concentration of up to 2.0 × 10 6) is formed by metal organic chemical vapor deposition.
¹⁸ cm- ³ , thickness-2 μm), n-InGaAs (P) cap layer 12 (carrier concentration> 7 × 10 ¹⁸ cm- ³ , thickness-
It was embedded flat with 0.3 μm). After that, the SiO ₂ film 13
Then, the n-electrode 14 is formed, and the substrate side is further polished to a total film thickness of about 100 μm, and then the p-electrode 1 is formed.
7 was formed by vapor deposition to form a device. Then, the resonator is cleaved to a length of 150 to 350 μm, the front facet has a low reflectance film 20 with a reflectance of 1%, and the rear facet has a high reflectance film 2 with a reflectance of 90%.
1 was given.

In the DFB laser according to this embodiment, the threshold current at room temperature is 5 to 9 m at the oscillation wavelength of 1.55 μm.
A, the slop efficiency was 0.38 to 0.55 mW / mA, and ΔG at room temperature was typically -10 nm to +1.
It was in the range of 0 nm. The threshold current at 85 ° C is 1
3-25mA, Slope efficiency 0.33-0.40mW / mA
Was obtained with a high yield, and modulation of 600 Mbit / s was sufficiently possible. Furthermore, the DFB oscillation was stable even at −40 ° C., and the secondary mode suppression ratio was maintained at 38 to 45 dB in the temperature range of −40 ° C. to + 85 ° C.
The amount of change in ΔG in the temperature range of −40 ° C. to + 85 ° C. was 10 nm or less, which was extremely small.

Although the application to the semiconductor laser has been described in the above embodiments, it is obvious that the present invention can be applied to the semiconductor laser of other wavelength bands. Also, n
Type DFB laser formed on a semiconductor substrate and an active layer of In
It goes without saying that the present invention is also applicable to a DFB laser formed with a GaAlAs-based quantum well structure and a DFB laser having another stripe structure such as a ridge type. Further, the strain amount of the strained quantum well layer is + 0.5% to +1.
DF within the range of 8% or -2.0% to -0.7%
Almost the same effect was obtained with the B laser and the DFB laser having 4 to 8 wells. Furthermore, although the present embodiment has been described by applying it to a single semiconductor laser device, it goes without saying that the present invention can also be applied to a semiconductor laser array used for optical interconnect, wavelength division multiplexing communication and the like.

[0020]

According to the present invention, the quantum level emission wavelength from each quantum well layer is changed by changing the quantum well layer thickness, mixed crystal composition strain amount, or strain amount of each quantum well layer. Temperature dependence of detuning wavelength ΔG dΔG
It is possible to provide a DFB laser having an extremely small / dT. Therefore, it is effective for stable operation of the distributed feedback semiconductor laser for optical communication in a wide temperature range, for example, -40 ° C to + 85 ° C. Further, by appropriately setting the structure such as the number of wells, the amount of strain, and the quantum well film thickness, the degree of reduction in the temperature dependence dΔG / dT of the detuning wavelength ΔG is large, and further D
It is effective for wide temperature operation of the FB laser.

[Brief description of drawings]

FIG. 1 (a) is a structural diagram showing an embodiment of the present invention, and (b) is (a).
Is a cross-sectional view taken along the line AA 'in the optical axis, and (c) is a band diagram of the conduction band of the quantum well active layer.

FIG. 2 is a diagram showing temperature dependence of a detuning wavelength of a DFB laser according to a conventional technique.

FIG. 3 is a diagram showing means and actions of the present invention.

FIG. 4 (a) is a structural diagram showing an embodiment of the present invention, and FIG. 4 (b) is (a).
Is a cross-sectional view taken along the line AA 'in the optical axis, and (c) is a band diagram of the conduction band of the quantum well active layer.

[Explanation of symbols]

1 ... p-InP substrate, 2 ... p-InP cladding layer, 3 ... Diffraction grating, 4, 19 ... Optical guide layer, 5, 18 ... Strained quantum well active layer, 6 ... n-InP cladding layer, 7 ... p- InP buried layer,
8 ... n-InP buried layer, 9 ... p-InP layer, 11 ... n-InP
Flattening layer, 12 ... n-InGaAsP cap layer, 13 ... S
iO ₂ film, 14 ... N electrode, 17 ... P electrode, 16, 23 ... Barrier layer, 15a-15e, 22a-22d ... Strained quantum well layer.

Front page continuation (72) Inventor Atsushi Nakamura 5-20-1 Kamisuihonmachi, Kodaira-shi, Tokyo Hitachi, Ltd. Semiconductor Business Division

Claims (13)

[Claims] 1. A distributed feedback semiconductor laser having at least an active layer for generating light, a clad layer for confining light, and a refractive index perturbation in the axial direction of a resonator on a semiconductor substrate, wherein at least two active layers are provided. Having a quantum well layer of
A distributed feedback semiconductor laser, wherein the quantum level emission wavelength of at least one quantum well layer is different from the quantum level emission wavelengths of other quantum well layers. 2. A distributed feedback semiconductor laser having at least an active layer for generating light, a clad layer for confining light, and a refractive index perturbation in the axial direction of a resonator on a semiconductor substrate, wherein at least two active layers are provided. Having a quantum well layer of
A distributed feedback semiconductor laser, wherein the quantum well film thickness of at least one quantum well layer is different from the quantum well film thickness of other quantum well layers. 3. A distributed feedback semiconductor laser having at least an active layer for generating light, a clad layer for confining light, and a refractive index perturbation in the axial direction of a resonator on a semiconductor substrate, wherein at least two active layers are provided. Having a quantum well layer of
A distributed feedback semiconductor laser, wherein a mixed crystal composition forming at least one quantum well layer is different from a mixed crystal composition forming another quantum well layer. 4. The distributed feedback semiconductor laser according to claim 1, further comprising a strained quantum well layer in which the lattice constant of the quantum well layer is different from the lattice constant of the semiconductor substrate. A distributed feedback semiconductor laser having a layer strain amount of + 0.5% to + 1.8% or -2.0% to -0.7%. 5. A distributed feedback semiconductor laser having at least an active layer for generating light, a clad layer for confining light, and a perturbation of a refractive index in the axial direction of a resonator on a semiconductor substrate, wherein at least two active layers are provided. A distributed feedback semiconductor laser, characterized in that the strain amount of at least one strain quantum well layer is different from the strain amount of another strain quantum well layer. 6. The distributed feedback semiconductor laser according to claim 1, wherein the difference between the maximum value and the minimum value of the quantum level emission wavelengths of the quantum well layer and the strained quantum well layer is 15 to 4.
A distributed feedback semiconductor laser having a thickness of 5 nm. 7. The distributed feedback semiconductor laser according to claim 1, 2 or 4, wherein the difference between the maximum quantum well film thickness and the minimum quantum well film thickness of the quantum well layer and the strained quantum well layer is 1.0. ~
A distributed feedback semiconductor laser having a wavelength of 3.5 nm. 8. The distributed feedback semiconductor laser according to claim 1, 2 or 4, wherein the quantum well layer and the strained quantum well layer have a maximum quantum well film thickness of 6 nm and a minimum quantum well film thickness of 4 nm.
A distributed feedback semiconductor laser characterized by: 9. The distributed feedback semiconductor laser according to claim 1, wherein the quantum level emission wavelengths of the quantum well layer and the strained quantum well layer are such that the hole injection side is closer to the electron injection side. A distributed feedback semiconductor laser characterized by having a long wavelength. 10. The distributed feedback semiconductor laser according to claim 1, wherein the quantum well layer and the strained quantum well layer have 4 to 8 wells. laser. 11. The distributed feedback semiconductor laser according to claim 1, wherein the semiconductor substrate is p-type I.
In the nP substrate, the active layer is formed in a mesa stripe shape, and the side surface of the mesa stripe active region is p / n /
A distributed feedback semiconductor laser, which is embedded with a p-type current blocking layer. 12. The distributed feedback semiconductor laser according to claim 1, wherein the laser oscillation wavelength is λL.
D, where λg is the optical gain peak wavelength at an injection current 0.9 times the threshold current, κ is the coupling constant of light due to perturbation of the refractive index in the axial direction of the resonator, and L is the resonator length. In addition, a distributed feedback semiconductor laser having a (λLD-λg) value of -10 to +10 nm and a κL value of 0.8 to 1.5 at room temperature. 13. The distributed feedback semiconductor laser according to claim 1, wherein the quantum well layer and the strained quantum well layer are InGaAsP layers or InGaAlAs.
Layer and laser oscillation wavelength is 1.25 to 1.60 μ
A distributed feedback semiconductor laser having a thickness of m.