JP2763090B2 - Semiconductor laser device, manufacturing method thereof, and crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a semi-conductor laser device and a manufacturing method thereof suitable for long distance and large volume optical communication light source.

[0002]

2. Description of the Related Art Recently, long-distance, large-capacity data transmission and CA
2. Description of the Related Art A distributed feedback semiconductor laser (DFB laser) device has been put to practical use as a light source for transmitting multi-channel video such as a TV. The DFB laser device has a feature of performing laser oscillation at a substantially single wavelength, has excellent high-speed response, and has low noise. Therefore, it is widely used as a light source for optical communication. In this DFB laser, two methods of producing optical distributed feedback have been theoretically shown by Kogelnic et al. ("Coupled-Wave Theory of Distributed Feed").
back Lasers ", Journal of Applied Physics, vol.4
3, p2327, 1972).

The first method is a refractive index coupling method in which a periodic fluctuation of the refractive index is provided in the direction of the cavity of the semiconductor laser, and laser oscillation is obtained at a wavelength (near the Bragg wavelength) corresponding to the period. Many production examples have been reported conventionally because of relatively easy production. However, this method theoretically oscillates in one of the two oscillation modes sandwiching the Bragg wavelength, and has a very high probability of oscillating in both.

The second method is a gain coupling method in which a periodic fluctuation of the gain is provided in the direction of the resonator of the semiconductor laser, and laser oscillation is performed at a wavelength (Bragg wavelength) corresponding to the period. In this method, since the laser oscillates theoretically only at the Bragg wavelength, there is a very high probability that a single-wavelength laser can be obtained. However, since this structure is difficult to manufacture, a laser having good characteristics has not been realized for a long time even after the theory has been shown.

Recently, however, a manufacturing method has been proposed in which an absorption layer is provided periodically in the direction of the cavity of a semiconductor laser to cause a periodic change in gain, thereby realizing a laser having good characteristics ("Long"). -Wavelength InGaAsP
/ InP Distributed Feedback Lasers Incorporating
Gain-Coupled Mechanism ", Photonics Technology Lett
ers, vol 4, p212, 1992). FIG. 18 shows the configuration. The n-type InP layers 21, 24, 25 have n-type InG
An aAsP absorption layer 23 is periodically buried, and an n-type InGaAsP optical waveguide layer 26 and an active layer 2 are formed thereon.
9, a p-type InGaAsP optical waveguide layer 30 and a p-type InP cladding layer 31 are formed. This n-type InGaAs
The band gap energy of the P absorption layer 23 is
Is set to be smaller than the light emission energy from the light source. For this reason, the n-type InGaAsP absorption layer 30 periodically absorbs the light emitted from the active layer 29 to produce a periodic fluctuation of the gain, and a single-wavelength laser oscillation is obtained with high probability.

A method of manufacturing the conventional structure shown in FIG.
Description will be made with reference to (a) to (c). First, FIG.
As shown in FIG. 9A, the n-type In
On the P substrate 21, an n-type InGaAsP absorption layer 23 and an n-type InP protection layer 24 are successively deposited. Then, FIG.
As shown in (b), by etching a predetermined portion of the n-type InGaAsP absorption layer 23, a plurality of n-type
The diffraction grating 22 in which the nGaAsP absorption layers 23 are periodically arranged is formed. Thereafter, as shown in FIG.
The n-type InP cladding layer 25 is crystal-grown, and the absorption layer 23
Embed

[0007]

However, in this method, it is necessary to etch the absorption layer 23 once,
The surface exposed by the etching will be exposed to a heat treatment during regrowth. At this time, a defect may occur in the etched portion of the absorption layer 23, and the optical characteristics of the absorption layer 23 may be impaired. Further, there is a possibility that the long-term reliability of the laser may be impaired.

The "wavelength chirp" generated when directly modulating a semiconductor laser is a major factor limiting long distance and large capacity, and it is desired to lower the light source for further improvement of transmission characteristics. .

The present invention has been made in view of the above circumstances, and it is an object of the present invention to have a high probability of oscillating at a single wavelength and to change the mode even for return light from outside the laser. and to provide a strong yet semiconductors laser device and a manufacturing method thereof also noise without.

[0010]

A semiconductor laser device according to the present invention comprises an InP substrate and a multilayer structure formed on the InP substrate, wherein the multilayer structure has at least a laser. An active layer for emitting light,
A periodic structure for applying light distribution feedback to the laser light, wherein the periodic structure has a cross section perpendicular to the main surface of the InP substrate and parallel to a resonator direction of the semiconductor laser device.
A plurality of semiconductor portion having a triangular shape projecting in the direction of the InP substrate, the band gap energy of the semiconductor portion constituting the said periodic structure is released via the optical distributed feedback from the active layer The energy is set to be equal to or less than the light energy, thereby achieving the above object.

Another semiconductor laser device of the present invention is an InP
A substrate, and a multilayer structure formed on the InP substrate, the multilayer structure comprising at least an active layer for emitting laser light, and a periodic structure for applying light distribution feedback to the laser light. The periodic structure includes a concave portion formed periodically in the multilayer structure and protruding from the InP substrate.
A plurality of irregularities with, and a semiconductor portion which is provided separately within the recess of each of the plurality of irregularities, the band gap energy of the semiconductor portion constituting the said periodic structure, said active The energy is set to be equal to or less than the energy of light emitted from the layer via the light distribution feedback, thereby achieving the above object.

Still another semiconductor laser device of the present invention is a semiconductor laser device comprising:
An InP substrate, comprising a multilayer structure formed on the InP substrate, wherein the multilayer structure has at least an active layer for emitting laser light, and a periodic structure for applying light distribution feedback to the laser light, And the periodic structure comprises the InP
In a cross section parallel to the cavity direction of the semiconductor laser device perpendicular to the main surface of the substrate, a plurality of semiconductor portions having a three <br/> angle shape protruding in the direction of the InP substrate, said periodic structure Is set to be equal to or greater than the energy of light emitted from the active layer via light distribution feedback, and the semiconductor portion is made of InAsP. In doing so, the above object is achieved.

Still another semiconductor laser device according to the present invention is a semiconductor laser device comprising:
An InP substrate, comprising a multilayer structure formed on the InP substrate, wherein the multilayer structure has at least an active layer for emitting laser light, and a periodic structure for applying light distribution feedback to the laser light, And the periodic structure comprises a multilayer structure.
Parts projecting with respect to the InP substrate are periodically formed in the concrete
A plurality of concave and convex portions each having a concave portion, and a semiconductor portion separately provided in the concave portion of each of the plurality of concave and convex portions, wherein the semiconductor portion constituting the periodic structure has The bandgap energy is set to be equal to or greater than the energy of light emitted from the active layer via the light distribution feedback, and the semiconductor portion is InAsP, thereby achieving the above object. Achieved.

In one embodiment, the periodic structure is configured
The semiconductor portion to be formed is InAsP.

The periodic structure includes the InP substrate and the InP substrate.
It can be provided between the active layer.

In one embodiment, the semiconductor portion forming the periodic structure includes a first semiconductor material having a band gap energy smaller than the energy of light emitted from the active layer via light distribution feedback; A second with a bandgap energy greater than the light energy
And the semiconductor material of the is formed from at least two materials.

Alternatively, the half constituting the periodic structure
The conductor portion is emitted from the active layer via light distribution feedback.
Band gap energy smaller than the energy of the light
A first semiconductor material having
At least two of a second semiconductor material for compensating a bending ratio.
Made of a similar material.

In one embodiment, the periodic structure includes
A first semiconductor portion composed of one semiconductor material and a second semiconductor portion;
And a second semiconductor portion made of a semiconductor material of
The first semiconductor portion and the second semiconductor portion
Are arranged alternately along the resonator direction, and the first
Is perpendicular to the main surface of the InP substrate, and
Projecting in the direction of the InP substrate in a section parallel to the device direction.
It is a prominent shape.

Preferably, the first of the periodic structures is
The band gap energy of the semiconductor part is
Energy of light emitted from the conductive layer through the light distribution return
Is set to be smaller than the second semiconductor.
The band gap energy of the body part is
Than the energy of the light emitted through the light distribution return from the
It is set to be large.

The semiconductor portion constituting the periodic structure
Has an average refractive index substantially equal to the refractive index of InP.
obtain.

The first semiconductor material is InAsP.
In some embodiments, the second semiconductor material may be InGaP.

A method for manufacturing a semiconductor laser device according to the present invention
Forming a plurality of periodically arranged grooves on the surface of the InP crystal; and forming at least phosphine and arsine.
Heat treating the InP crystal in a mixed atmosphere to deposit InAsP in each of the plurality of grooves, and forming a multilayer structure including an active layer on the InP crystal. As a result, the above object is achieved.

According to another method of manufacturing a semiconductor laser device of the present invention, a step of forming a multi-layer structure including an active layer and an uppermost layer being an InP layer on a substrate is provided. forming on the surface of the InP layer, at least follower
The multilayer structure is heat-treated in an atmosphere where sphin and arsine are mixed , and InAsP is formed in each of the plurality of grooves.
And a step of depositing the above, whereby the above object is achieved.

According to the crystal growth method of the present invention, irregularities are formed on the surface of an InP crystal, and the irregularly formed InP crystal is heat-treated in an atmosphere in which at least phosphine and arsine are mixed. InAsP is formed in the concave portions of the irregularities, thereby achieving the above object.

[0025]

The band gap of InAsP can be changed by changing the flow rate of arsine with respect to the flow rate of phosphine .

According to still another semiconductor laser device of the present invention,
A light emitting section for generating laser light, a light modulating section optically coupled to the light emitting section to modulate the laser light, a striped multilayer structure including the light emitting section and the light modulating section, and the striped multilayer A substrate that supports the structure,
An active layer, and a portion formed periodically in the striped multilayer structure along the optical axis direction and protruding from the substrate as a concave portion.
A plurality of irregularities, include a semiconductor portion which is provided separately within the recess of each of the plurality of irregularities, the band gap energy of the semiconductor portion is emitted through the light distributed feedback of the active layer The energy is set to be equal to or less than the energy of the light to be emitted, and the light modulation section has a light modulation layer whose optical characteristics change according to the modulation signal, thereby achieving the above object. Preferably, the semiconductor portion provided separately in each of the plurality of concaves and convexes has an absorption type diffraction grating in which the absorptance of light emitted from the active layer periodically changes along the optical axis direction. Configure.

According to still another semiconductor laser device of the present invention,
A light emitting section for generating laser light, a light modulating section optically coupled to the light emitting section to modulate the laser light, a striped multilayer structure including the light emitting section and the light modulating section, and the striped multilayer A substrate that supports the structure,
An active layer, and a portion formed periodically in the striped multilayer structure along the optical axis direction and protruding from the substrate as a concave portion.
A plurality of irregularities, include a semiconductor portion which is provided separately within the recess of each of the plurality of irregularities, the band gap energy of the semiconductor portion is emitted through the light distributed feedback of the active layer The semiconductor portion is InAsP, and the light modulation section has a light modulation layer whose optical characteristics change according to a modulation signal. Thus, the above object is achieved.

In one embodiment, the striped multilayer is
The structure includes a multiple quantum well layer, wherein the active layer comprises:
The photonic modulator formed from a first portion of the multiple quantum well layer;
The tuning layer is formed from a second portion of the multiple quantum well layer.
I have. Preferably, the active layer and the light modulation layer are
Connected by a third portion of the multiple quantum well layer,
The third portion is in front of the first portion of the multiple quantum well layer.
And the second portion. More preferred
Means that the first portion of the multiple quantum well layer is
It is thicker than the second portion of the sub well layer.

[0030] In another embodiment, the semiconductor portion is a semiconductor device.
Can be formed on the periodic irregularities formed on the surface of the substrate.
You.

In still another embodiment, the active layer and the active layer
The semiconductor device further includes an optical waveguide layer provided between the semiconductor portion.
You.

In still another embodiment, the light emitting section is actually
First voltage applying means for applying a qualitatively constant voltage;
Second voltage applying means for applying a modulation voltage to the light modulation unit
And further comprising.

[0033] The semiconductor portion may be InAsP.
You.

According to still another semiconductor laser device of the present invention,
A light emitting portion for generating laser light, an optical waveguide portion optically coupled to the light emitting portion and propagating the laser light, a striped multilayer structure including the light emitting portion and the optical waveguide portion, and the striped multilayer structure A substrate supporting the structure, the light-emitting portion includes an active layer that emits the laser light, and the optical waveguide portion includes a Bragg reflector whose refractive index changes periodically along the optical axis direction. The Bragg reflector has a semiconductor portion formed separately in a concave portion of the periodic uneven structure, and emits light of a selected wavelength among light emitted from the active layer. The light is reflected toward the active layer, thereby achieving the above object.

The semiconductor portion may be InAsP.
You. Preferably, the InAsP absorbs the laser light.
Has a band gap energy that is too large to fit
You.

The optical waveguide section controls the wavelength of the laser light.
A wavelength tuning unit for adjusting may be included. Preferred
In other words, the optical waveguide unit adjusts the phase of the laser light.
And a phase tuning unit for the operation.

According to still another semiconductor laser device of the present invention,
A light emitting unit for generating laser light, and optically coupled to the light emitting unit
A light modulating unit for modulating the laser light, the light emitting unit,
A striped multilayer structure including the light modulating section;
And a substrate supporting a pump-shaped multilayer structure,
An active layer, and the optical modulator has an optical characteristic according to a modulation signal.
A light modulating layer having a variable property, the light emitting portion and the light
The modulator has an absorption array periodically arranged along the optical axis direction.
Type diffraction grating is formed, and the laser from the light emitting portion is formed.
Light is almost diffracted by the absorption type diffraction grating of the light modulation section.
Without doing so, the above objective is achieved.

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a perspective view showing an embodiment of a DFB laser device according to the present invention.

The DFB laser 100 has an n-type InP cladding layer (200 nm thick) on an n-type InP substrate 1.
4. n-type InGaAsP waveguide layer (50 nm thick, λg =
1.05 μm) 5, multiple quantum well active layer 6, p-type InG
aAsP waveguide layer (thickness 30 nm, λg = 1.05 μm)
7, and p-type InP cladding layer (thickness: 400 nm) 15
Is provided.

The mesa structure is provided on the ridge formed on the upper surface of the n-type InP substrate 1. Further, both sides of the mesa structure are buried with a p-type InP current block layer 8 and an n-type InP current block layer 9. On these semiconductor layers, 10 p-type InP buried layers and p-type InGaAs
An sP contact layer (λg = 1.3 μm) 11 is laminated.

On the back surface of the n-type InP substrate 1, Au / Sn
An n-side electrode 14 made of an alloy is formed, and p-type InGaAs
An SiO ₂ insulating film 12 having a stripe-shaped window is formed on the sP contact layer 11, and a p-side electrode 13 made of an Au / Zn alloy formed on the
p-type In through the stripe-shaped window of the iO ₂ insulating film 12
It is in contact with the GaAsP contact layer 11.

A plurality of InAsP absorption layers 3 are arranged between the n-type InP substrate 1 and the n-type InP cladding layer 4 at a pitch of 203 nm along the laser cavity direction. I
The substrate 1 of the nAsP absorption layer 3 is parallel to the laser cavity direction.
Has a triangular cross section perpendicular to the main surface, and its vertex is n
It protrudes toward the mold InP substrate 1 side. InAsP absorption layer 3
However, since it has such a shape, etching of the absorption layer becomes unnecessary. It is very difficult to form an absorption layer having a small size of about several tens of nm by etching as in this structure. Variations in size also increase. Since etching is not required, a small absorbing layer having a size of about several tens of nm can be easily formed uniformly.
As a result, variations in characteristics between the elements are extremely reduced.

The multiple quantum well active layer 6 includes a 6-nm-thick InGaAsP well layer in which a compressive strain is introduced, and a 10-nm-thick InGaAsP barrier layer (λg = 1.05 μm) in which no strain is intentionally introduced. Quantum well (10
Pair).

In this embodiment, the photoluminescence wavelength of the InAsP absorption layer 3 formed periodically in the laser resonator direction is set to 1.4 μm, while the oscillation wavelength from the active layer is set to 1.3 μm. Is set. For this reason, the InAsP absorption layer 3 causes a periodic fluctuation of the gain in the direction of the laser cavity. As a result, laser oscillation of a single wavelength can be obtained with a higher probability than in the case of periodic fluctuations of only the refractive index.

A method for manufacturing the DFB laser 100 shown in FIG. 1 will be described with reference to FIGS.

First, as shown in FIG.
The pitch is 203 nm and the depth is about 100 nm on the P substrate 1
Is formed by the two-beam interference exposure method.

Next, 100% phosphine (PH ₃ ) 100 cc / min and 10% arsine (AsH ₃ ) 10 c
c / min, and the n-type InP substrate 1 was heated to 600 ° C.
Heat treatment. As a result, as shown in FIG. 2B, an InAsP absorption layer 3 having a thickness of about 50 nm is formed in the concave portion of the diffraction grating 2. Thereafter, as shown in FIG. 2C, the n-type InP cladding layer (thickness: 200 nm) 4 and the n-type InGaAsP waveguide layer (thickness: 50 nm, λg = 1.05 μm) are successively formed by metal organic chemical vapor deposition. 5, a 6-nm-thick InGaAsP well layer to which a compressive strain is introduced and a 10-nm-thick InGaAsP barrier layer (λg
= 1.05 μm), a multiple quantum well active layer 6 composed of 10 pairs, a p-type InGaAsP waveguide layer (thickness: 30 n).
m, λg = 1.05 μm) 7, p-type InP cladding layer (400 nm thick) 15, p-type InGaAsP cap layer
(λg = 1.3 μm) 16 are sequentially deposited.

Thereafter, as shown in FIG. 2D, a stripe-shaped mesa is formed by etching. Next, the p-type InP current blocking layer 8 and the n-type InP
Current block layer 9, p-type InP buried layer 10, p-type I
After sequentially depositing nGaAsP contact layers (λg = 1.3 μm) 11, an SiO ₂ insulating film 12 is deposited, windows are opened in a stripe shape, and an Au / Zn electrode 13 is deposited. Further, an Au / Sn electrode 14 is deposited on the back surface of the n-type InP substrate 11. After cleavage, the DFB as shown in FIG.
The laser device 100 is manufactured.

In this embodiment, since the absorbing layer is not formed by etching, atoms are less likely to escape from the surface of the absorbing layer even when the temperature is increased in the growth of the semiconductor film after etching.

After the formation of the diffraction grating, almost all elements can be formed only by the growth of the semiconductor layer, so that the manufacture is very easy.

The important steps of the above manufacturing method are shown in FIG.
This will be described in detail with reference to FIGS.

FIG. 3A shows a cross section of the n-type InP substrate 1 on which the diffraction grating 2 is formed by etching.
When the n-type InP substrate 1 on which the diffraction grating 2 is formed is heat-treated in an atmosphere in which phosphine (PH ₃ ) and arsine (AsH ₃ ) are mixed, as shown in FIG. Due to the transport phenomenon, the InAsP layer 3 is deposited in the concave portion of the diffraction grating 2. Thereafter, the n-type InP
When the cladding layer 4 is continuously grown, as shown in FIG. 3C, it is possible to form an inverted triangular InAsP layer 3 periodically arranged in n-type InP. In addition, from the viewpoint of light absorption, the thickness of the InAsP layer 3 is 10 n
m or more.

FIG. 4 shows the InAs fabricated in this manner.
The result of measuring the photoluminescence spectrum from the P layer 3 at room temperature is shown. A unimodal spectrum having a peak around 1.5 μm is observed. At the same time, in the case where the same processing was performed on the n-type InP substrate on which no diffraction grating was formed, no light emission other than the light emission of InP was observed.

FIG. 5 shows that 100% phosphine is
The photoluminescence wavelength with respect to the flow rate of arsine at a temperature of 600 ° C. at c / min is shown. As shown in FIG. 5, when the flow rate of arsine (AsH ₃ ) is changed while the flow rate of phosphine (PH ₃ ) is kept constant, I
The photoluminescence wavelength from the nAsP layer 3 changes continuously. This indicates that by the This changing the flow rate of arsine (AsH _3), it is possible to vary the bandgap energy of the InAsP layer 3. Further, when the band gap energy is set to be larger than the light energy emitted from the active layer of the laser via the light distribution feedback, that is, the InAsP layer 3
When the photoluminescence wavelength is set to be shorter than the laser oscillation wavelength, the InAsP layer 3 becomes transparent to light emitted from the active layer. As a result, InAs
Since the P layer 3 has a higher refractive index than the surrounding InP,
A periodic change in the refractive index occurs, and a refractive index-coupled DFB laser can be manufactured.

On the other hand, when the band gap energy of the InAsP layer is set smaller than the light energy emitted from the active layer of the laser via the light distribution feedback, that is,
When the photoluminescence wavelength of the InAsP layer is set to a longer wavelength side than the oscillation wavelength of the laser, the InAsP layer absorbs light emitted from the active layer, so that the gain periodically changes and a gain-coupled DFB laser is used. Can be made. The DFB laser of FIG. 1 is a gain-coupling type.

When the InAsP layer 3 is deposited and a periodic change in the gain is caused by the deposition, the refractive index of the InAsP layer 3 is larger than that of InP. FIG. 6 shows that InAsP
After depositing layer 3, InG has a lower refractive index than InP.
The structure in which the aP layer refractive index compensation layer 18 is deposited is shown.
According to this structure, the InAsP layer 3 and the InGaP layer 18
By adjusting the film thickness, the average refractive index of the InAsP layer 3 and the InGaP layer 18 formed in the concave portion of the diffraction grating 2 can be adjusted, and the degree of freedom in laser design can be increased. Become. This will be described in detail in a third embodiment.

[0081] Figure 7 is a current of the DFB laser device of Figure 1 -
The result of having measured the light output characteristic is shown. The threshold current is 16 mA, the slope efficiency is 0.25 mW / mA,
It shows excellent properties. FIG. 8 shows the result of measuring the oscillation spectrum of the DFB laser device. The side mode suppression ratio representing the ratio between the oscillation main mode and sub mode is 40d
B or more, stable laser oscillation of a single wavelength is obtained. Since the side mode suppression ratio of the index-coupling type DFB laser is about 30 dB, it can be seen that the advantage of the gain-coupling type appears in the DFB laser device of this embodiment.

In this embodiment, the n-type InP cladding layer 4 is replaced with an n-type InGaAsP optical waveguide layer.
The n-type InP cladding layer and the n-type InGaAsP optical waveguide layer may be integrated to form an n-type InGaAsP optical waveguide layer.

By using the gain-coupling type as described above, the probability of oscillating at a single wavelength is high, and the mode is stable even for return light from outside the laser.

(Embodiment 2) FIG. 9 shows a DFB according to the present invention.
FIG. 10 is a perspective view showing another embodiment of the laser device, with a part cut away to show the internal structure.

The DFB laser 200 of the present embodiment has an n-type I
An n-type InP cladding layer (thickness: 200 n) is formed on the nP substrate 1.
m) 4, n-type InGaAsP waveguide layer (50 nm thick,
λg = 1.05 μm) 5, multiple quantum well active layer 6, p-type I
nGaAsP waveguide layer (thickness 30 nm, λg = 1.05 μm)
m) 7, the first p-type InP cladding layer (average thickness 100
nm) 15, the second p-type InP cladding layer (average thickness 3
(00 nm) 17. The p-type InP current blocking layer 8 and the n-type I
It is buried with an nP current blocking layer 9, on which a p-type InP burying layer 10 and a p-type InGaAsP contact layer (λg = 1.3 μm) 11 are formed.

On the back surface of the n-type InP substrate 1, an n-side electrode 14 made of an Au / Sn alloy is formed.
An SiO ₂ insulating film 12 having a striped window is formed on the P contact layer 11, and a p-side electrode 13 made of an Au / Zn alloy formed on the SiO ₂ insulating film 12 is formed of SiO _2.
(2) p-type InGaAs through a striped window of insulating film
It is in contact with P contact layer 11.

Further, the p-type InP cladding layer 15 and the second p-type
The InAsP absorption layers 3 are formed between the InP cladding layers 17 at a pitch of 203 nm in the direction of the laser cavity, and have an apex on the n-type InP substrate 1 side in a cross section parallel to the direction of the laser cavity. It has a triangular shape.

The multiple quantum well active layer 6 is composed of a 6-nm-thick InGaAsP well layer in which a compressive strain is introduced and a 10-nm-thick InGaAsP barrier layer (λg = 1.05 μm) in which no strain is intentionally introduced. It consists of 10 pairs.

In this embodiment, the photoluminescence wavelength of the InAsP absorption layer 3 formed periodically in the laser resonator direction is set to 1.4 μm, while the oscillation wavelength from the active layer is set to 1.3 μm. Is set. For this reason, the InAsP absorption layer 3 causes a periodic fluctuation of the gain in the direction of the laser cavity. Thus, for the above-described reason, laser oscillation of a single wavelength can be obtained with a higher probability than in the case of the periodic fluctuation of only the refractive index.

In this embodiment, the InAsP absorption layer 3 is formed on the active layer 6. In the configuration of the first embodiment, In which is located between the InAsP absorption layer 3 and the active layer 6 is used.
The properties of the P cladding layer 4 and the InGaAsP waveguide layer 5 are better if they are relatively thick to recover crystallinity. However, by adopting the configuration as in the present embodiment,
P-type In located between the active layer 6 and the InAsP absorption layer 3
The thicknesses of the GaAsP waveguide layer 7 and the p-type InP cladding layer 15 can be set relatively freely. In Example 1, the light intensity distribution and the degree of coupling between the InAsP absorption layer 3 were measured.
It is possible to set it more freely than it is.

In the second embodiment, the p-type InP cladding layer 15 is replaced with a p-type InGaAsP optical waveguide layer, and the p-type InP cladding layer and the p-type InGaAsP optical waveguide layer are integrated to form a p-type InGaAsP optical waveguide layer. It may be.

Referring to FIGS. 10A to 10F,
A method for manufacturing the DFB laser 200 of FIG. 9 will be described.

First, as shown in FIG.
An n-type InP cladding layer (thickness: 200 nm) 4, an n-type InGaAsP waveguide layer (thickness: 50 nm, λg = 1.05 μm) 5, and a thickness in which a compressive strain is introduced on the nP substrate 1 by a metal organic chemical vapor deposition method. A 6-nm InGaAsP well layer and a 10-nm thick InGaAs
A multiple quantum well active layer 6 composed of 10 pairs of P barrier layers (λg = 1.05 μm), a p-type InGaAsP waveguide layer (thickness 30 nm, λg = 1.05 μm) 7, a p-type InP cladding layer ( (Thickness 200 nm) 15 are sequentially deposited. Thereafter, as shown in FIG. 10B, a diffraction grating 2 having a pitch of 203 nm and a depth of about 100 nm is formed by a two-beam interference exposure method.

Next, 100% phosphine (PH ₃ ) 100 cc / min and 10% arsine (AsH ₃ ) 10 c
c / min was introduced, and the substrate 1 was subjected to a heat treatment at 600 ° C., thereby forming the diffraction grating 2 as shown in FIG.
The InAsP absorption layer 3 of about 50 nm is formed in the concave portion.
Thereafter, as shown in FIG. 10D, a second p-type InP cladding layer (with an average thickness of 300
nm) 17, p-type InGaAsP cap layer (λg = 1.3
μm) 16 are sequentially deposited.

Thereafter, as shown in FIG. 10E, a stripe-shaped mesa is formed by etching. Next, the p-type InP current blocking layer 8 and the n-type In
After sequentially depositing a P-current block layer 9, a p-type InP buried layer 10, and a p-type InGaAsP contact layer (λg = 1.3 μm) 11, an SiO ₂ insulating film 12 is deposited, a window is opened in a stripe shape, and Au / A Zn electrode 13 is deposited. Further, an Au / Sn electrode 14 is deposited on the back surface of the n-type InP substrate 1. After cleavage, the DFB as shown in FIG.
Obtain a laser device.

(Embodiment 3) FIG. 11 shows a DF according to the present invention.
FIG. 13 is a perspective view showing still another embodiment of the B laser device, with a portion cut away to show the internal structure.

The DFB laser 300 of this embodiment has an n-type I
An n-type InP cladding layer (thickness: 200 n) is formed on the nP substrate 1.
m) 4, n-type InGaAsP waveguide layer (50 nm thick,
λg = 1.05 μm) 5, multiple quantum well active layer 6, p-type I
nGaAsP waveguide layer (thickness 30 nm, λg = 1.05 μm)
m) 7, p-type InP cladding layer (thickness: 400 nm) 15
And a mesa-like structure. Both sides of the mesa-like structure are buried with a p-type InP current block layer 8 and an n-type InP current block layer 9, and a p-type InP buried layer 15 and a p-type InGaAsP contact layer (λg = 1.
3 μm) 11 are formed.

On the back surface of the n-type InP substrate 1, an n-side electrode 14 made of an Au / Sn alloy is formed.
An SiO ₂ insulating film 12 having a striped window is formed on the P contact layer 11, and a p-side electrode 13 made of an Au / Zn alloy formed on the SiO ₂ insulating film 12 is formed of SiO _2.
(2) p-type InGa through a striped window of the insulating film 12
It is in contact with the AsP contact layer 11.

Further, an InAsP absorption layer 3 and an InGaP refractive index compensation layer 18 are formed between the n-type InP substrate 1 and the n-type InP cladding layer 4 at a pitch of 203 nm in the direction of the laser cavity. It has a triangular shape having its apex on the n-type InP substrate 1 side in a cross section parallel to the container direction. Further, the InAsP absorption layer 3 and I
The average refractive index of the nGaP refractive index compensation layer 18 is almost equal to that of InP.

The multiple quantum well active layer 6 is composed of a 6-nm-thick InGaAsP well layer in which a compressive strain is introduced and a 10-nm-thick InGaAsP barrier layer (λg = 1.05 μm) in which no strain is intentionally introduced. It consists of 10 pairs.

In this embodiment, the photoluminescence wavelength of the InAsP absorption layer 3 formed periodically in the laser resonator direction is set to 1.4 μm, while the oscillation wavelength from the active layer 6 is 1.3 μm. Is set to For this reason, the InAsP absorption layer 3 causes a periodic fluctuation of the gain in the direction of the laser cavity. Further, the InAsP absorption layer 3 and the InGaP refractive index compensation layer 18 are formed by the InGaP refractive index compensation layer 18 formed on the InAsP absorption layer 3.
Is almost equal to that of InP, there is no periodic fluctuation of the refractive index, and only the periodic fluctuation of the gain exists. As a result, for the above-described reason, laser oscillation of a single wavelength can be obtained with a higher probability than in the case where the periodic fluctuations of the gain and the refractive index are simultaneously present.

In this embodiment, the n-type InP cladding layer 4 is replaced with an n-type InGaAsP optical waveguide layer.
The n-type InP cladding layer and the n-type InGaAsP optical waveguide layer may be integrated to form an n-type InGaAsP optical waveguide layer.

Next, a method of manufacturing the DFB laser 300 shown in FIG. 11 will be described with reference to FIGS.

As shown in FIG. 12A, a diffraction grating 2 having a pitch of 203 nm and a depth of about 100 nm is formed on an n-type InP substrate 1 by a two-beam interference exposure method.

Next, this was placed in a hydrogen atmosphere in 100% phosphine (PH ₃ ) at 100 cc / min and 10% arsine (AsH ₃ ).
At a rate of 10 cc / min and heat treatment at 600 ° C., as shown in FIG.
The InAsP absorption layer 3 of nm is formed. Then, FIG.
Subsequently, as shown in FIG. 3C, an n-type InGaP refractive index compensation layer 18 is deposited by metal organic chemical vapor deposition. afterwards,
As shown in FIG. 12D, the n-type InP cladding layer (thickness: 200 nm) 4, the n-type InGaAsP waveguide layer (thickness: 50 nm, λg = 1.05 μm) 5, and the thickness at which compressive strain was introduced A multiple quantum well active layer 6 comprising 10 pairs of a 6 nm thick InGaAsP well layer and a 10 nm thick InGaAsP barrier layer (λg = 1.05 μm) into which no strain is intentionally introduced, a p-type InGaAsP waveguide A layer (thickness 30 nm, λg = 1.05 μm) 7, a p-type InP cladding layer (thickness 400 nm) 15, and a p-type InGaAsP cap layer (λg = 1.3 μm) 16 are sequentially deposited.

Thereafter, as shown in FIG. 12E, a stripe-shaped mesa is formed by etching.

Next, the p-type InP current blocking layer 8, the n-type InP current blocking layer 9, the p-type InP
The buried layer 10 and the p-type InGaAsP contact layer (λg
= 1.3 μm) 11 are sequentially deposited, and then SiO ₂ insulating film 12 is deposited.
Is deposited, a window is opened in a stripe shape, and an Au / Zn electrode 1 is formed.
3 is deposited. In addition, Au /
An Sn electrode 14 is deposited. After the cleavage, a DFB laser device 300 as shown in FIG.

(Embodiment 4) FIG. 13 shows a DF according to the present invention.
FIG. 13 is a perspective view showing still another embodiment of the B laser device, with a portion cut away to show the internal structure.

The DFB laser 400 of the present invention has an n-type In
N-type InP cladding layer (200 nm thick) on P substrate 1
4. n-type InGaAsP waveguide layer (50 nm thick, λg =
1.05 μm) 5, multiple quantum well active layer 6, p-type InG
aAsP waveguide layer (thickness 30 nm, λg = 1.05 μm)
7. First p-type InP cladding layer (average thickness 100 n
m) 15, the second p-type InP cladding layer (thickness: 300 n)
m) a mesa-like structure of 17; Both sides of the mesa structure are buried with a p-type InP current block layer 8 and an n-type InP current block layer 9, and a p-type I
nP buried layer 10, p-type InGaAsP contact layer
(λg = 1.3 μm) 11 is formed.

On the back surface of the n-type InP substrate 1, an n-side electrode 14 made of an Au / Sn alloy is formed, and p-type InGaAs is formed.
An SiO ₂ insulating film 12 having a striped window is formed on the P contact layer 11, and a p-side electrode 13 made of an Au / Zn alloy formed on the SiO ₂ insulating film 12 is formed of SiO _2.
(2) p-type InGa through a striped window of the insulating film 12
It is in contact with the AsP contact layer 11 .

Further, the p-type InP cladding layer 15 and the second
The InAsP absorption layer 3 and the InGaP refractive index compensating layer 18 are formed between the InP cladding layers 17 at a pitch of 203 nm in the direction of the laser cavity, and their shapes are n-type InP substrates in a cross section parallel to the laser cavity direction. It has a triangular shape with its vertex on one side.

The multiple quantum well active layer 6 is composed of a 6-nm-thick InGaAsP well layer in which a compressive strain is introduced and a 10-nm-thick InGaAsP barrier layer (λg = 1.05 μm) in which no strain is intentionally introduced. It consists of 10 pairs.

In the present embodiment, the photoluminescence wavelength of the InAsP absorption layer 3 formed periodically in the laser resonator direction is set to 1.4 μm, while the oscillation wavelength from the active layer is set to 1.3 μm. Is set. For this reason, the InAsP absorption layer 3 causes a periodic fluctuation of the gain in the direction of the laser cavity. Further, the InGaP refractive index compensation layer formed on the InAsP absorption layer 3 allows
Since the average refractive indices of the nAsP absorption layer and the InGaP refractive index compensation layer are almost equal to those of InP, there is no periodic fluctuation of the refractive index, but only the periodic fluctuation of the gain.
As a result, for a reason as described above, laser oscillation of a single wavelength can be obtained with a higher probability than in the case of periodic fluctuation of gain and refractive index.

Further, in this embodiment, the InAsP absorption layer 3 is formed on the active layer 6. In the configuration of the third embodiment, In which is located between the InAsP absorption layer 3 and the active layer 6 is used.
The thicknesses of the P cladding layer 4 and the InGaAsP waveguide layer 5 need to be relatively large in order to recover crystallinity. However, with the configuration as in the present embodiment, the p-type InGaAs located between the active layer 6 and the InAsP absorption layer 3 is formed.
The thicknesses of the sP waveguide layer 7 and the p-type InP cladding layer 15 can be set relatively freely. This indicates that the degree of coupling between the light intensity distribution and the InAsP absorption layer 3 can be set more freely than in the third embodiment.

In the fourth embodiment, the p-type InP cladding layer 15 may be replaced with a p-type InGaAsP optical waveguide layer.

A method for manufacturing the DFB laser 400 shown in FIG. 13 will be described with reference to FIGS.

As shown in FIG. 14A, an n-type InP cladding layer (thickness: 200 nm) 4 and an n-type InGaAsP waveguide layer (thickness: 50 nm) were formed on an n-type InP substrate 1 by metal organic chemical vapor deposition. λg = 1.05 μm) 5, composed of 10 pairs of a 6-nm-thick InGaAsP well layer in which a compressive strain is introduced and a 10-nm-thick InGaAsP barrier layer (λg = 1.05 μm) in which no strain is intentionally introduced. A multi-quantum well active layer 6, a p-type InGaAsP waveguide layer (thickness 30 nm, λg = 1.05 μm) 7 and a p-type InP clad layer (thickness 200 nm) 15 are sequentially deposited, and the pitch is 203 nm on the surface thereof. Diffraction grating 2 having a depth of about 100 nm
It is formed by a light beam interference exposure method.

Next, this was put in a hydrogen atmosphere at 100 cc / min of 100% phosphine (PH ₃ ) and 10% arsine (AsH ₃ ).
By introducing a heat treatment at 600 ° C. at a rate of 10 cc / min, as shown in FIG.
The InAsP absorption layer 3 of nm is formed. Subsequently, as shown in FIG. 14 (c), n
A type InGaP refractive index compensation layer 18 is deposited. Subsequently, as shown in FIG. 14D, a second p-type InP cladding layer (average thickness 300 nm) 1 is formed by metal organic chemical vapor deposition.
7, p-type InGaAsP cap layer (λg = 1.3 μm) 1
6 are sequentially deposited.

Thereafter, as shown in FIG. 14E, a stripe-shaped mesa is formed by etching. Next, the p-type InP current blocking layer 8 and the n-type In
After sequentially depositing a P current block layer 9, a p-type InP buried layer 10, and a p-type InGaAsP contact layer (λg = 1.3 μm) 11, an SiO ₂ insulating film 12 is deposited, a window is opened in a stripe shape, and Au / A Zn electrode 13 is deposited.

Further, Au / S is applied to the back surface of the n-type InP substrate 1.
An n-electrode 14 is deposited. After the cleavage, a DFB laser device 400 as shown in FIG.

The above embodiments are the DFB laser device of 1.3 μm band and the manufacturing method thereof. However, the present invention can be applied to other wavelength bands such as 1.55 μm band by changing the constituent materials. It is. Although the above embodiment has a buried structure, the effect of the present invention is the same even with a ridge structure.

In the above embodiments, the buried structure is formed by the liquid phase epitaxy, but the metal organic vapor phase epitaxy may be used.

[0123] (Embodiment 5) FIG. 15 is a further Ru good in the present invention is a perspective view showing another DFB laser device, it is partially cut away as can be seen the internal structure.

The present DFB laser 500 includes an n-type InP cladding layer (200 nm thick) 4
Type InGaAsP waveguide layer (thickness: 50 nm, λg = 1.0)
5 μm) 5, multiple quantum well active layer 6, p-type InGaAs
It has a mesa multilayer structure in which a P waveguide layer (thickness 30 nm, λg = 1.05 μm) 7 and a p-type InP cladding layer (thickness 400 nm) 15 are formed. On both sides of the mesa-like multilayer structure, a p-type InP current blocking layer 8 and an n-type InP current blocking layer 9 are buried.
The buried layer 10 and the p-type InGaAsP contact layer (λg
= 1.3 μm) 11. An n-side electrode 14 made of an Au / Sn alloy is formed on the back surface of the n-type InP substrate 1, and an SiO ₂ insulating film 12 having a striped window is formed on the p-type InGaAsP contact layer 11. The p-side electrode 13 made of an Au / Zn alloy formed thereon is in contact with the p-type InGaAsP contact layer 11 through a striped window of the SiO ₂ insulating film 12. Further, an InAsP absorption layer 3 is formed between the n-type InP substrate 1 and the n-type InP cladding layer 4 in the laser cavity direction.
It is formed at a pitch of 3 nm, and has a triangular shape having its vertex on the n-type InP substrate 1 side in a cross section parallel to the laser cavity direction. Also, InAs
N-type InGaAsP refractive index compensation layer on both sides of P absorption layer 3
(Thickness: 50 nm, λg = 1.2 μm) 32 are formed.
The multiple quantum well active layer 6 has a 6-nm-thick InGaAsP well layer in which compressive strain is introduced and a 10-nm-thick InGaAsP barrier layer in which no strain is intentionally introduced (λg = 1.
05 μm).

In this embodiment, the photoluminescence wavelength of the InAsP absorption layer 3 formed periodically in the laser cavity direction is set to 1.4 μm, while the oscillation wavelength from the active layer 6 is 1.3 μm. Is set to For this reason, the InAsP absorption layer 3 causes a periodic fluctuation of the gain in the direction of the laser cavity. Further, the InAsP absorption layer 3
The InGaAsP refractive index compensation layer 32 formed on both sides of the substrate makes periodic fluctuation of the refractive index extremely small.
It is close to a state where only the periodic fluctuation of the gain exists. As a result, for the above-described reason, laser oscillation of a single wavelength can be obtained with a higher probability than in the case where the periodic fluctuations of the gain and the refractive index are simultaneously present.

In this embodiment, the n-type InP cladding layer 4 may be replaced with an n-type InGaAsP optical waveguide layer. Further, the InAsP absorption layer 3 and the InGaAsP refractive index compensation layer 32 may be formed in the P-type InP cladding layer 15.

A method for manufacturing the DFB laser 500 shown in FIG. 15 will be described with reference to FIGS. 16 (a) to 16 (f) and 17 (a) to 17 (c).

First, as shown in FIGS. 16 (a) and 17 (a), an n-type InGaAsP refractive index compensation layer (50 nm thick, λg) was formed on the n-type InP substrate 1 by metal organic chemical vapor deposition.
= 1.2 μm) 32 and an n-type InP layer (thickness: 20 nm) 33 are deposited. Next, as shown in FIG. 16B and FIG.
The pitch is 203 nm and the depth is about 100 nm with respect to the n-type InGaAsP refractive index compensation layer 32 and the n-type InP layer 33.
Is formed by the two-beam interference exposure method. Next, this is put in a hydrogen atmosphere with 100% phosphine (PH ₃ ) 10
After introducing 0 cc / min and 10 cc / min of 10% arsine (AsH ₃ ) and performing a heat treatment at 600 ° C., as shown in FIGS.
The InAsP absorption layer 3 of nm is formed. Then, FIG.
17 (d) and FIG. 17 (d), the n-type In
P cladding layer (thickness: 200 nm) 4, n-type InGaAs
P waveguide layer (thickness: 50 nm, λg = 1.05 μm) 5, InGaAsP well layer having a thickness of 6 nm in which compressive strain is introduced, and InGaAs having a thickness of 10 nm in which no strain is intentionally introduced.
A multiple quantum well active layer 6 composed of 10 pairs of sP barrier layers (λg = 1.05 μm), a p-type InGaAsP waveguide layer (thickness 30 nm, λg = 1.05 μm) 7, a p-type InP cladding layer ( A 400 nm thick layer 15 and a p-type InGaAsP cap layer (λg = 1.3 μm) 16 are sequentially deposited. After this,
As shown in FIG. 16E, a stripe-shaped mesa is formed by etching. Next, p-type I
nP current block layer 8, n-type InP current block layer 9,
After sequentially depositing a p-type InP buried layer 10 and a p-type InGaAsP contact layer (λg = 1.3 μm) 11, SiO ₂
An insulating film 12 is deposited, a window is opened in a stripe shape, and Au /
A Zn electrode 13 is deposited. Further, an Au / Sn electrode 14 is deposited on the back surface of the n-type InP substrate 1. After cleavage, Figure 1
A DFB laser device 500 as shown in FIG.

(Embodiment 6) A DFB laser in which an external modulator is integrally integrated is expected as an ultra-low chirp light source, but the conventional structure has a problem in its yield, and a gain-coupled DFB laser Although high single mode oscillation yield was confirmed, there was a problem that there was a limit to lowering the chirp.

The present invention provides a method of periodically forming an absorption layer without performing etching and regrowth of the absorption layer, and a gain-coupled DFB laser manufactured by the method.

An embodiment of the distributed feedback semiconductor laser device according to the present invention will be described below.

FIG. 20 shows the DFB laser device 6 of this embodiment.
10 shows a cross section along the resonator direction of 00. The DFB laser device 600 includes a light emitting unit 71 that generates laser light and a light modulating unit 72 that modulates laser light, which are integrated on one n-InP substrate 51. These light emitting units 7
1 and the light modulating section 72 are integrally contained in a striped multilayer structure having a width of about 1 to 2 μm.

More specifically, the light emitting section 71 is composed of n-InP
N periodically arranged at a pitch of 243 nm on the substrate 51
-InGaAs absorption diffraction grating (bandgap wavelength λ
_g = 1.68 μm, layer thickness d = 30 nm) 52, n−I
nGaAsP optical waveguide layer (λ _g = 1.05 μm, d = 15
0 nm) 55, an undoped InGaAs PMQW active layer 56, a p-InP cladding layer 58A, and a p-InG
The aAsP contact layer 59 and the p-type electrode 60 have a multilayer structure in which the n-InP substrate 51 is stacked in this order.

On the other hand, the light modulating section 72 includes the n-InP substrate 5
An undoped InGaAsP light modulating layer (λ _g = 1.48 μm, d = 300 nm) 57 formed on
The InP clad layer 58B and the p-type electrode 61 have a multilayer structure in which the n-InP substrate 51 is stacked in this order.

The p-type electrode 60 and the p-type electrode 61 are electrically separated from each other and arranged so as to be given different potentials. In contrast, the n-type electrode 62 has n-In
The light emitting portion 71 is formed on the entire back surface of the P substrate 51.
And a common n-side electrode for the light modulator 72. A p-type electrode 60 and n-type
A substantially constant voltage is applied between the mold electrode 62 and
As a result of the drive current flowing through the light emitting section 71, stable laser oscillation is caused. On the other hand, the p-type electrode 61 and the n-type electrode 6
2, a modulated voltage is applied in a reverse bias state, and the optical characteristics of the undoped light modulation layer 57 are modulated according to the applied voltage.

[0136] Note that the device end face on the side where the light modulation unit 72 is provided (exit end face), the reflectance are 0.1% low reflection film 64 is coated, and the light emitting portion 71 is provided The element end face on the side where the light is reflected is coated with a high reflection film 63 having a reflectance of 90%. As a result, a high light output is obtained from the emission end face of the device.

The MQW active layer 56 of the light emitting section 71 is made of InG
aAsP strain well layer (layer thickness 6 nm, compressive strain 1%) and λ _g
It has a multiple quantum well structure in which barrier layers (layer thickness: 10 nm) of 1.3 μm are alternately arranged. In this embodiment,
The number of quantum wells is seven. The photoluminescence from the MQW active layer 56 at room temperature was measured.
The effective bandgap wavelength (λ _PL ) of the QW active layer 6 is 1.
It was 56 μm.

The n-InGaAs absorption type diffraction grating 5
2 is formed of a plurality of light absorbing layers (thickness: 30 nm) regularly arranged in the resonator direction (optical axis direction). The width (W) of each light absorbing layer measured along the cavity direction is 50
In nm, the pitch of the array (配 列) is 243 nm. As described above, the absorption coefficient (that is, gain) for the light obtained from the MQW active layer 56 changes periodically along the resonator direction, forming a gain-coupled resonator. Thus,
At the time of current injection into the light emitting section 71, single mode oscillation (oscillation wavelength 1.55 μm) is obtained near the Bragg wavelength.

The light modulating unit 72 of this embodiment modulates the laser light emitted from the light emitting unit 71 due to the electric field absorption effect caused by the application of the reverse bias voltage. In this embodiment, the oscillation threshold current of the light emitting unit 71 is 20 mA, and the light output from the end face of the optical modulator when no bias is applied to the optical modulation unit is 10 mW.
The extinction ratio of 20 dB was obtained by applying a reverse bias of 2 V.

The DFB laser device 600 shown in FIG.
Will be described.

First, the n-InP is formed on the n-InP substrate 51 by the first metal organic chemical vapor deposition (hereinafter referred to as MOVPE).
A GaAs film is grown. Next, the n-InGaAs film is patterned by a two-beam interference exposure method and etching, and an absorption type diffraction grating 52 having a pitch of 243 nm is selectively formed only in the light emitting section 71.

Thereafter, the n-InGaAsP optical waveguide layer 55 and the undoped MQ
W active layer 56, p-InP cladding layer 58A and p-
The InGaAsP contact layer 59 is formed on the n-InP substrate 51.
Grow over the entire surface. Thereafter, each semiconductor layer grown on the region where the light modulation section 72 is to be formed is selectively removed. More specifically, first, the p-In
After masking the surface of the GaAsP contact layer 59 with SiO ₂ , the p-
The InGaAsP contact layer is formed of H ₂ SO ₄ : H ₂ O ₂ : H ₂
It is selectively etched with a mixed solution of O = 5: 1: 1.
Next, the p-InP cladding layer 58A is made of HCl + H ₃ PO ₄
= 1: 2, and the MQW active layer 56 and the optical waveguide layer 55 made of InGaAsP are further formed of H ₂ SO ₄ : H ₂ O ₂ :
It is selectively removed by etching with a mixed solution of H ₂ O = 5: 1: 1.

An undoped InGaAsP light modulation layer 57 and a p-InP cladding layer 58B are formed by third MOVPE growth on the region from which each semiconductor has been removed by the above etching. Thus, as shown in FIG. 20, the respective semiconductor layers constituting the light modulation section 72 are grown.

Next, each of the above semiconductor layers is patterned in a stripe shape for lateral confinement of current and light. Specifically, after forming a SiO ₂ stripe mask pattern having a width of about 1 to ₂ μm extending in the resonator direction, p
-Remove portions of the InP cladding layers 58A and 58B that are not covered by the mask. Next, after loading cladding is formed on each of the light emitting section 71 and the light modulating section 72, an SiO ₂ film (not shown) for passivation is deposited on the entire surface. Next, an opening is provided in the contact region of the SiO ₂ film, and p-type electrodes 60 and 61 are deposited. Further, the substrate 51
An n-type electrode 62 is formed on the back surface of the substrate. Hereinafter, the DF of FIG.
Describing the characteristics of the B-les-over The 600.

In the case of the conventional example in which the light emitting portion is formed by a refractive index-coupled DFB laser, the yield of single mode oscillation is only about 30% due to variations in end face phase, taking into account variations in the fabrication of diffraction gratings. However, in this embodiment, a single mode oscillation is obtained by gain coupling,
% Higher single wavelength yields were obtained.

[0146] Also, D of the refractive index coupling in this embodiment
Since the hole hole burning in the axial direction is smaller than that of the FB laser and the phase fluctuation due to the refractive index fluctuation is smaller, the change in the oscillation wavelength due to the return light reflected from the end face on the light modulator side is smaller.
In the case where the light emitting portion is a DFB laser with a refractive index coupling, even if the end face reflectivity is 0.1% or less, the yield of obtaining a wavelength chirp of 0.2 angstroms or less in digital modulation is 10%.
On the other hand, in the device of this example, the yield was more than doubled at the same end face reflectance.

Even when the end face reflectivity is 0.2%, the same yield as that of the conventional case where the reflectivity is 0.1% or less is obtained. This can increase the allowable value of the thickness control of the reflective film in the actual process, and can increase the easiness of element fabrication. It goes without saying that further improvement in characteristics can be obtained by adopting a window structure on the emission end face or introducing a semi-insulating layer between both regions to increase the resistance between elements.

Further, the present structure has a feature that the structure of the active layer and the light modulation layer can be set to, for example, a bulk active layer or an MQW layer, and the layer structure of the MQW can be set independently. In the case of analog modulation, etc., the spectral line width and chirp are deeply involved in the increase in noise and modulation distortion due to multiple reflection in the optical transmission line,
For this suppression, a low chirp and a wide spectral line width are effective. Normally, when directly modulating a laser, the two are dependent on each other via a line width increase coefficient, and when the chirp is reduced, the line width is also reduced. However, in the structure of this embodiment, the line width is increased by adopting a bulk active layer, for example. An ultra-low chirp characteristic can be obtained with a line width, and application to a wider transmission line is possible.

In the structure of this embodiment, the light emitting section 71 and the light modulating section
The coupling efficiency of the light with the light 72 is about 90%. This is because the light modulation layer 57 and the active layer 56 can be formed on the same optical axis with relatively high accuracy because the selective etching is used in the manufacturing method of this embodiment. Although the absorption type diffraction grating 52 is formed below the active layer 56 in the semiconductor laser shown in FIG. 20, similar characteristics can be obtained when it is formed above the active layer 56.

In the lateral confinement, a loaded clad is used, but it is also possible to make a buried type by adding crystal growth once.

(Embodiment 7) Next, another embodiment of the DFB laser device according to the present invention will be described with reference to FIG. FIG. 21 shows a cross section of the DFB laser device 700 of the present embodiment along the cavity direction.

The DFB laser device 700 shown in FIG. 21 includes a light emitting section 71 for generating laser light and a light modulating section 72 for modulating laser light, which are integrated on one n-InP substrate 51. The light emitting section 71 and the light modulating section 72 are integrally included in a striped multilayer structure having a width of about 1 to 2 μm. Further, the light emitting section 71 and the light modulating section 72
Have different thicknesses but substantially the same layer configuration.

More specifically, the light emitting section 71 is composed of n-InP
NI periodically arranged on a substrate at a pitch of 243 nm
nGaAs absorption diffraction grating (bandgap wavelength λ _g =
1.68 μm, layer thickness d = 10 nm) 52 and n-InG
aAsP optical waveguide layer (λ _g = 1.05 μm, d = 150 n
m) 55 and undoped InGaAs PMQW active layer 5
6, p-InP cladding layer 58, and p-InGaAs
A P contact layer 59 and a p-type electrode 60 have a multilayer structure in which the n-InP substrate 51 is stacked in this order.

On the other hand, the light modulating section 72 includes the n-InP substrate 5
N-InGaAsP optical waveguide layer (λ _g =
1.05 μm, d = 75 nm) 55 and undoped In
GaAsP light modulation layer 57 and p-InP cladding layer 58
And the p-type electrode 61 in this order.
Has a multilayer structure laminated from the side.

In this embodiment, the light absorbing layer forming the n-InGaAs absorption type diffraction grating 52 is formed not only in the light emitting section 71 but also in the light modulating section 72. However, in the light modulation section 72, the thickness of the light absorption layer is about 5 μm, and the light absorption layer of the light modulation section 72 has
It does not function substantially as an absorption type diffraction grating.

Undoped InGaAsPM of the light emitting section 71
The QW active layer 56 is formed from the first portion of the multiple quantum well layer formed in the stripe-shaped multilayer structure, and the undoped InGaAsP light modulation layer 57 is formed from the second portion of the multiple quantum well layer. Have been. This multiple quantum well layer is composed of an InGaAsP well layer (λg =
1.62 μm) and an InGaAsP barrier layer (λg = 1.3
0 μm) are alternately laminated (10 pairs).
The thickness of the multiple quantum well layer is
It is 80 nm, and 90 nm in the light modulation section. In the transition region located between the light emitting section 71 and the light modulation section 72, the thickness of the multiple quantum well layer is from 180 nm to 90 nm.
up to nm.

The p-type electrode 60 and the p-type electrode 61 are electrically separated from each other and arranged so as to be given different potentials. In contrast, the n-type electrode 62 has n-In
The light emitting portion 71 is formed on the entire back surface of the P substrate 51.
And a common n-side electrode for the light modulator 72. A p-type electrode 60 and n-type
A substantially constant voltage is applied between the mold electrode 62 and
As a result of the drive current flowing through the light emitting section 71, stable laser oscillation is caused. On the other hand, the p-type electrode 61 and the n-type electrode 6
2, a modulated voltage is applied in a reverse bias state, and the optical characteristics of the undoped light modulation layer 57 are modulated according to the applied voltage.

[0158] Note that the device end face on the side where the light modulation unit 72 is provided (exit end face), the reflectance are 0.1% low reflection film 64 is coated, and the light emitting portion 71 is provided The element end face on the side where the light is reflected is coated with a high reflection film 63 having a reflectance of 90%. As a result, a high light output is obtained from the emission end face of the device.

The n-InGaAs absorption type diffraction grating 5
2 is formed of a plurality of light absorbing layers (thickness: 10 nm) regularly arranged in the resonator direction (optical axis direction). The width (W) of each light absorbing layer measured along the cavity direction is 50
In nm, the pitch of the array (配 列) is 243 nm. As described above, the absorption coefficient (that is, gain) for the light obtained from the MQW active layer 56 changes periodically along the resonator direction, forming a gain-coupled resonator. Thus,
At the time of current injection into the light emitting section 71, single mode oscillation (oscillation wavelength 1.55 μm) is obtained near the Bragg wavelength.

The light modulating section 72 of this embodiment modulates the laser light emitted from the light emitting section 71 due to the electric field absorption effect caused by the application of the reverse bias voltage. In this embodiment, the oscillation threshold current of the light emitting unit 71 is 20 mA, and the light output from the end face of the optical modulator when no bias is applied to the optical modulation unit is 10 mW.
The extinction ratio of 20 dB was obtained by applying a reverse bias of 2 V.

In this embodiment, the thickness of the light absorption layer and the MQW layers (56 and 57) forming the absorption type diffraction grating 52 is large in the light emitting section 71 and thin in the light modulating section 72. In the case of the present embodiment, the layer thickness of the light modulating section 72 is about half that of the light emitting section. As a result, the quantum shift amounts of the light absorption layers and the like differ depending on their thicknesses. Light emitting unit 7
The effective bandgap wavelength of the MQW active layer 56 at 1 is
1.56 μm (the thickness of the well layer is 8 nm).
In this case, the effective band gap wavelength of the light modulation layer 57 is 1.49.
μm (well layer thickness 4 nm). The effective band gap wavelength of the light absorbing layer of the n-InGaAs absorption type diffraction grating 52 in the light emitting section 71 is 1.58 μm (well layer thickness 1).
0 nm), and the effective band gap wavelength of the light absorption layer in the light modulation section 72 is 1.48 μm (layer thickness 4 nm). The wavelength shift amount of the light absorbing layer is large because the light absorbing layer is surrounded by a layer having a high barrier formed of the InP substrate 51 and the InGaAsP optical waveguide layer (λ _g = 1.05 μm) 55. It is because it has.

The width (W) of the absorption type diffraction grating 52 measured along the resonator length direction is 50 nm, and the pitch is 243 nm. Since the gain coupling is achieved by the periodic change of the absorption coefficient, that is, the gain in the resonator direction, a single mode oscillation near the Bragg wavelength is obtained when the current is injected into the light emitting section 71.

When a forward bias is applied to the light emitting section 71 to inject a current, a single-axis mode oscillation with a wavelength of 1.55 μm is obtained by gain coupling, and the laser light reaching the light modulating layer 22 is optically modulated by applying a reverse bias. You. In this structure, since both regions are connected by the same growth layer, an optical coupling efficiency close to 100% can be obtained. In addition, despite the same growth layer, the bandgap energy of the optical waveguide layer 57 and the light absorbing layer in the light modulation section 72 is sufficiently higher than the energy of the laser light, so that the laser light The part 72 can be propagated. As a result, when a driving current of 100 mA flows to the light emitting unit 71, high output light of 10 mW or more can be obtained from the end face (output end face) of the light modulating section 72. As for the wavelength chirp, good characteristics equivalent to those of the sixth embodiment are obtained. In this embodiment, the light modulating unit 72 also has a plurality of light absorbing layers arranged, but the effective refractive index of the light modulating unit 72 is smaller than the effective refractive index of the light emitting unit 71, and The Bragg wavelength at 72 is much shorter than the wavelength of the laser light. Therefore, laser light is hardly diffracted I by the light-absorbing layer of the optical modulation unit 72.

Hereinafter, a method of manufacturing the DFB laser 700 shown in FIG. 21 will be described.

First, the upper surface of the n-InP substrate 51 is covered with _two stripe-shaped SiO ₂ masks extending along the resonator length direction. FIG. 2 shows an example of this striped SiO ₂ mask.
This is shown in FIG. Two striped SiO ₂ mask is Hedatare through the opening of 10 [mu] m, the width of each stripe-shaped SiO ₂ mask, in the region where the light emitting portion 71 is formed, for example, is set to 30 [mu] m, the light modulation In the region where the portion 72 is formed, the thickness is set to 10 μm. As a result, the width of the exposed portion (opening) of the upper surface of the n-InP substrate differs between the light emitting section 71 and the light modulating section 72.
As a result, the crystal growth rate of the crystal growth step after the light-emitting section 7
1 and the light modulator 72. In a region having a large exposed area, the growth rate is lower than in a region where the exposed area is not large. To cause such a change in growth rate,
The shape of the stripe-shaped SiO ₂ mask is not limited to that illustrated in FIG. Also, the material of the mask,
The material is not limited to SiO ₂ and may be a specific semiconductor material or an amorphous insulating material such as silicon nitride.

Next, metal organic chemical vapor deposition (hereinafter referred to as MOVP)
According to E), n-InGaAs is selectively formed on a region of the upper surface of the substrate 51 which is not covered with the SiO ₂ mask.
Layer 52 is grown epitaxially. InGaAs layer 5
The thickness of 2 differs depending on the width of the opening of the mask. In this embodiment, InGaAs is formed in a region where the light emitting section 71 is formed.
The thickness of the s layer 2 was 10 nm, and the thickness of the InGaAs layer 2 in the region where the light modulation section 72 was formed was 5 nm.

Next, the InGaAs layer 2 is patterned by the two-beam interference exposure method and etching,
A 3 nm absorption diffraction grating 52 is formed. Next, the SiO
_{The second} MOVPE growth with the n-InGaAsP optical waveguide layer 55 and the undoped MQ
W active layer 56, p-InP cladding layer 58 and p-I
An nGaAsP contact layer 59 is selectively grown. Also by this growth, the thickness of each layer differs depending on the width of the opening of the SiO ₂ mask, and a desired film thickness difference is obtained between the light emitting portion and the light modulating portion.

Next, as in the case where the semiconductor laser 600 shown in FIG. 20 is manufactured, loaded claddings are formed in the direction of the resonator for lateral confinement of current and light, respectively. After depositing an SiO ₂ film for passivation on the entire surface, an opening is provided in a contact region of the SiO ₂ film, and p-type electrodes 60 and 61 are deposited. On the back surface of the substrate 51, an n-type electrode 62 is formed.

According to the present manufacturing method, the plane layout of the stripe-shaped laminated structure is defined in one mask forming step. Further, the necessary semiconductor layer growth can be completed only by performing two crystal growth steps with the grating forming step interposed therebetween. In particular, by using a mask in which the width of the opening is changed between the region where the light emitting portion 71 is formed and the region where the light modulating portion 72 is formed, a multilayer structure self-aligned with the opening can be easily formed. There is a big effect on what you can do.

In this embodiment, the film thickness is controlled by SiO 2
₂₎ Adjusting the opening width of the mask
Another opening may be provided in the mask portion located on both sides of the opening, and the width of the opening may be changed. Alternatively, a stripe-shaped mesa whose width changes in the middle may be formed on the upper surface of the substrate 51, and a laminated structure may be selectively formed on the mesa.

(Embodiment 8) Next, a further embodiment of the DFB laser device according to the present invention will be described with reference to FIG. FIG. 22 shows a DFB laser device 80 of the present embodiment.
0 shows a cross section along the direction of the resonator.

The DFB laser device 800 shown in FIG. 22 includes a light emitting section 71 for generating laser light and a light modulating section 72 for modulating laser light, which are integrated on one n-InP substrate 51. The light emitting section 71 and the light modulating section 72 are integrally included in a striped multilayer structure having a width of about 1 to 2 μm. Further, the light emitting section 71 and the light modulating section 72
Have different thicknesses but substantially the same layer configuration.

More specifically, the light emitting section 71 is made of n-InP
NI periodically arranged on a substrate at a pitch of 243 nm
nGaAs absorption diffraction grating (bandgap wavelength λ _g =
1.68 μm) 52, n-InGaAsP optical waveguide layer (λ _g = 1.05 μm, d = 150 nm) 55, undoped InGaAs PMQW active layer 56 and p-InP
Cladding layer 58 and p-InGaAsP contact layer 5
9 and the p-type electrode 60 are arranged in this order in the n-InP substrate 5.
It has a multilayer structure laminated from one side.

On the other hand, the light modulating section 72 includes the n-InP substrate 5
N-InGaAsP optical waveguide layer (λ _g =
1.05 μm, d = 70 nm) 55 and undoped In
GaAsP light modulation layer 57 and p-InP cladding layer 58
And the p-type electrode 61 in this order.
Has a multilayer structure laminated from the side.

Except for the n-InGaAs absorption type diffraction grating 52 described below, the semiconductor laser of this embodiment is different from that of FIG.
It has the same configuration as the first semiconductor laser. InGa
In the present embodiment, the light absorption layer constituting the As absorption type diffraction grating 52 is formed on a plurality of stripe-shaped irregularities arranged on the upper surface of the substrate 51. Each unevenness extends in a direction perpendicular to the resonator length direction, and is selectively formed in a region where the light emitting section 71 is formed. The light absorbing layer has 20
nm (effective λ _g = 1.6 μm),
It has a thickness of only a few nm or less (PL wavelength> 1.3 μm) on the protrusion. As described above, the thickness of the light absorbing layer of this embodiment is periodically changed in accordance with the unevenness of the base. As a result, the absorption type diffraction grating 52 is formed due to the change in the location of the band gap. In this embodiment, the thickness of the light absorbing layer may be changed periodically along the resonator length direction, and the light absorbing layer does not need to be divided into a plurality. However, the light absorbing layer may not be grown on the convex portion, and may be separated into a plurality of light absorbing layers. In the light modulation section 72, the thickness of the n-InGaAs light absorption layer is 4 nm.

The thickness of the well layer of the MQW active layer 56 is 8 nm.
In the effective band gap wavelength λ _g is 1.56μm. A thickness 4nm of the well layer of the MQW light modulation layer 57, the effective bandgap wavelength lambda _g is 1.48 .mu.m.

A method for manufacturing the DFB laser 800 shown in FIG. 22 will be described below.

First, a diffraction grating is selectively formed in a region of the n-InP substrate 51 where the light emitting section 71 is to be formed. More specifically, by two-beam interference exposure method and etching,
Concave portions arranged at a pitch of 243 nm are formed in the region of the n-InP substrate 51. Etching is performed so that the concave portion has a depth of about 50 to 100 nm at the deepest point.

Next, a pair of stripe-shaped SiO ₂ masks extending along the resonator direction are formed on the upper surface of the n-InP substrate 51. In the region where the light-emitting portion is formed, each of the stripe-shaped SiO ₂ masks has a width of 30 μm, and is arranged with an opening having a width of 10 μm. On the other hand, in the region where the light modulation section is formed, the width of each of the stripe-shaped SiO ₂ masks is 10 μm, and the stripe-shaped SiO ₂ masks are arranged with an opening having a width of 10 μm. The width of each of the stripe-shaped SiO ₂ masks is wide in the region where the light emitting unit is formed, and narrow in the region where the light modulation unit 72 is formed.

Next, n-InGaAs is formed on the n-InP substrate 51 by metal organic chemical vapor deposition (hereinafter referred to as MOVPE).
s layers 52 and 4, n-InGaAsP optical waveguide layer 55,
The undoped MQW layers 56 and 57, the p-InP cladding layer 58 and the p-InGaAsP contact layer 59 are grown. These semiconductor layers are made of striped SiO
₂ Selectively grow on areas not covered by the mask. The thickness of each semiconductor layer is varied depending on the mask width, the light emitting portion 7
1 and the light modulator 72 . The base is n-InP
Since the growth rate varies depending on whether concave or convex portion of the substrate 51, as shown in FIG. 22, the thickness of the light absorbing layer is periodically changed by the irregular portion.

Next, loading cladding is formed in the direction of the resonator for lateral confinement of current and light. Then, after depositing an SiO ₂ film for passivation on the entire surface, an opening is provided in a contact region of the SiO ₂ film, and p-type electrodes 60 and 61 are deposited. On the back surface of the substrate 51, an n-type electrode 62 is formed.

According to this manufacturing method, the plane layout of the stripe-shaped laminated structure is defined in one mask forming step. In addition, the necessary semiconductor layer can be completely grown only by performing one crystal growth step after the grating formation step. By changing the width of the mask opening between the region where the light emitting unit 71 is formed and the region where the light modulating unit 72 is formed, a multilayer structure that is self-aligned with the opening can be easily formed. Further, according to the present manufacturing method, the crystal growth with the largest load in the manufacturing process can be performed in one continuous step, and as a result, a complicated integrated structure can be formed by a very simple process.

According to the semiconductor laser 800 of FIG. 22, the same excellent characteristics as those of the seventh embodiment have been confirmed. Further, one of the advantageous effects is that unevenness for forming a diffraction grating can be formed by processing InP whose shape can be relatively easily controlled by etching. Another feature is that the absorption type diffraction grating is formed by simply epitaxially growing the light absorbing layer without depositing / etching the light absorbing layer. Because of this feature,
The periodic structure of the absorption coefficient can be reliably obtained even if the shape of the underlayer of the light absorbing layer is slightly varied. Therefore, the substrate 51 is formed by wet etching, which has relatively poor controllability.
The device characteristics can be stably obtained even if the uneven portion is formed on the surface of the device.

(Embodiment 9) Next, still another embodiment of the semiconductor laser according to the present invention will be described with reference to FIG. FIG. 23 shows a cross section of the DFB laser device 900 of the present embodiment along the cavity direction. This DFB laser device 900 is integrated on one n-InP substrate 51,
A light emitting unit 71 that generates laser light and a light modulating unit 72 that modulates laser light are provided. The light emitting section 71 and the light modulating section 72 are integrally included in a striped multilayer structure having a width of about 1 to 2 μm.

More specifically, the light emitting section 71 is made of n-InP
An undoped InGaAsP optical waveguide layer (λ _g = 1.48 μm, d = 0.5 μm) 55 formed on a substrate, an undoped InP spacer layer (d = 0.1 μm) 81, and an undoped InGaAsP active layer (λ _g = 1.55 μm,
d = 0.1 μm) 56 and a p-InP cladding layer 58
And a p-InGaAsP contact layer 59 and a p-type electrode 60. Further, the p-InP cladding layer 58
Inside, at a position away from the active layer 56 by a predetermined distance,
An n-InGaAs absorption diffraction grating 52 is provided. The light absorbing layers constituting the n-InGaAs absorption type diffraction grating 52 are periodically arranged at a pitch of 230 nm along the resonator length direction.

The light modulating section 72 includes an undoped InGaAsP light modulating layer 57 (composition wavelength: 1.48 μm) formed on the n-InP substrate 51, an undoped InP spacer layer 81, a p-InP cladding layer 58, and a p-InP cladding layer 58. And a mold electrode 61.

On the entire back surface of the substrate 51, an n-type electrode 62
Are formed.

[0188] Note that the device end face on the side where the light modulation unit 72 is provided (exit end face), the reflectance are 0.1% low reflection film 64 is coated, and the light emitting portion 71 is provided The element end face on the side where the light is reflected is coated with a high reflection film 63 having a reflectance of 90%. As a result, a high light output is obtained from the emission end face of the device.

In this embodiment, the light guide layer 55 of the light emitting section 71 is provided.
And the light modulation layer 57 of the light modulation section 72 are formed from the same semiconductor layer. The spacer layer 81 of the light emitting section 71 and the light modulating section 72 is also formed of the same semiconductor layer.

The DFB laser device 900 shown in FIG.
The method for manufacturing the will be described.

First, the MOVP is placed on the n-InP substrate 51.
By E, undoped InGaAsP optical waveguide layer 55,
Undoped InP spacer layer 81, undoped InGa
AsP active layer 56, p-InP clad layer and nI
An nGaAs layer is sequentially grown. Thereafter, the n-InGaAs layer is patterned by two-beam interference exposure and etching to form a plurality of light absorption layers arranged at a pitch of 230 nm along the cavity length direction.

Next, the region where the light emitting section 71 is formed is
After masking with O ₂ , the n-InGaAs contact layer located in the region where the light modulation section 72 is formed is H ₂ SO ₄ + H
Etching is selectively performed with a mixed solution of ₂ O ₂ + H ₂ O = 5: 1: 1. Subsequently, the p-InP cladding layer is formed with HCl: H
₃ PO ₄ = 1: 2 mixed solution, an InGaAsP active layer 56 to further _{H 2 SO 4: H 2 O} 2: H 2 O = 5: 1: a mixed solution of 1, respectively, selectively etched .

Next, by the second MOVPE growth, p
-Forming an InP cladding layer and a p-InGaAsP contact layer;

After forming a SiO ₂ stripe mask pattern in the resonator direction for lateral confinement of current and light, the layers up to the p-InP cladding layer 58 are removed, and the light emitting portion 71 and the light modulating portion 72 are respectively loaded with cladding. To form After depositing passivation SiO ₂ on the entire surface, an opening is provided in the contact region to form the p-type electrode 60 and
61 is deposited. Further , the n-type electrode 6
By forming 2 , the structure of FIG. 23 can be manufactured.

According to the present manufacturing method, the plane layout of the stripe-shaped laminated structure is defined in one mask forming step. Further, the necessary semiconductor layer growth can be completed only by performing two crystal growth steps with the grating forming step interposed therebetween. Further, the configuration of the active layer and the configuration of the light modulation layer can be selected as long as the characteristics of the laser of the light emitting section and the coupling of light between regions are not deteriorated. That is, both layers can be bulk or MQW layers. In particular, the application of the bulk active layer can reduce the chirp without reducing the spectral line width of the light source, and is effective in suppressing the generation of additional distortion and noise in an analog optical transmission line having multiple reflection.
As described above, according to the present embodiment, the setting of the spectrum width in a wide range can be obtained by a simple process.

Embodiment 10 Next, still another embodiment of the DFB laser device according to the present invention will be described with reference to FIG. FIG. 24 shows the DFB laser device 10 of the present embodiment.
14 shows a cross section along the resonator direction of 00.

The DFB laser apparatus 1000 shown in FIG. 24 has a light emitting section 71 for generating laser light and a light modulating section 72 for modulating laser light, which are integrated on one n-InP substrate 51.
And The light emitting section 71 and the light modulating section 72 are integrally included in a striped multilayer structure having a width of about 1 to 2 μm. Further, the light emitting section 71 and the light modulating section 72
Have different thicknesses but substantially the same layer configuration.

More specifically, the light emitting section 71 is made of n-InP
NI periodically arranged on the substrate at a pitch of 201 nm
nAsP absorption diffraction grating (bandgap wavelength λ _g =
1.4 μm) 52 and an n-InGaAsP optical waveguide layer (λ
_g = 1.05 μm, d = 150 nm) 55, an undoped InGaAs MQW active layer 56, a p-InP cladding layer 58, a p-InGaAsP contact layer 59,
The p-type electrode 60 has a multilayer structure in which the layers are stacked in this order from the n-InP substrate 51 side. n-InAsP
The light absorption layer of the absorption type diffraction grating 52 absorbs light emitted from the active layer 56.

On the other hand, the light modulating section 72 includes the n-InP substrate 5
N-InGaAsP optical waveguide layer (λ _g =
1.05 μm, d = 70 nm) 55 and undoped In
GaAs light modulation layer 57 and p-InP cladding layer 58
And the p-type electrode 61 in this order.
Has a multilayer structure laminated from the side.

Undoped InGaAs MQW Active Layer 56
The well layer has a thickness of 8 nm and a PL wavelength of 1.31 μm, and the well layer has a thickness of 4 nm and a PL wavelength of 1.0 nm.
25 μm.

Except for the n-InAsP absorption type diffraction grating 52 described below, the semiconductor laser of this embodiment is similar to that of FIG.
Has the same configuration as the semiconductor laser. InGaAs
In the present embodiment, the light absorption layer constituting the s-absorption diffraction grating 52 is formed on a plurality of stripe-shaped irregularities arranged on the upper surface of the substrate 51. Each unevenness extends in a direction perpendicular to the resonator length direction, and is selectively formed in a region where the light emitting section 71 is formed. The light absorbing layer has a thickness of 20 n in the recess.
has a thickness of m (effective lambda _g = 1.6 [mu] m), but only has a thickness of several nm or less (PL wavelength> 1.3 .mu.m) is on the convex portion. Thus, the light absorbing layer of the present embodiment is
The thickness periodically changes according to the uneven shape of the base. As a result, the absorption type diffraction grating 52 is formed due to the change in the location of the band gap. In this embodiment, the thickness of the light absorbing layer may be changed periodically along the resonator length direction, and the light absorbing layer does not need to be divided into a plurality. However, the light absorbing layer may not be grown on the convex portion, and may be separated into a plurality of light absorbing layers. In addition,
In the light modulation section 72, the thickness of the n-InGaAs light absorption layer is 4 nm.

Hereinafter, a method of manufacturing the semiconductor laser 1000 of FIG. 24 will be described with reference to FIGS.

First, as shown in FIG.
A diffraction grating is selectively formed in a region of the nP substrate 51 where the light emitting section 71 is formed. More specifically, concave portions arranged at a pitch of 230 nm are formed in the region of the n-InP substrate 51 by two-beam interference exposure and etching.
Etching is performed so that the concave portion has a depth of about 50 to 100 nm at the deepest point.

Next, as shown in FIG.
A pair of striped SiO ₂ masks extending along the resonator direction are formed on the upper surface of the nP substrate 51. In the region where the light-emitting portion is formed, each of the stripe-shaped SiO ₂ masks has a width of 30 μm, and is arranged with an opening having a width of 10 μm. On the other hand, in the region where the light modulation section is formed, the width of each of the stripe-shaped SiO ₂ masks is 10 μm, and the stripe-shaped SiO ₂ masks are arranged with an opening having a width of 10 μm. The width of each of the stripe-shaped SiO ₂ masks is wide in a region where a light emitting portion is formed, and narrow in a region where a light modulation portion is formed.

Next, 100% phosphine (PH ₃ ) 100 cc / min and 10% arsine (AsH ₃ ) 10 c
At a rate of c / min, the n-InP substrate is heat-treated at 600 ° C. therein. As a result, as shown in FIG. 25C, an InAsP absorption layer of about 50 nm is formed in the concave portion of the diffraction grating 52. After that, metal organic chemical vapor deposition (hereinafter MOVPE)
Thus, the n-InGaAsP optical waveguide layer 55, the undoped MQW layers 56 and 57 , and the p-InP cladding layer 58
Then, a p-InGaAsP contact layer 59 is grown. These semiconductor layers are selectively grown on regions not covered by the stripe-shaped SiO ₂ mask. The thickness of each semiconductor layer changes according to the mask width, and differs between the light emitting section 71 and the light modulating section 72 .

Next, loaded claddings are formed in the direction of the resonator for lateral confinement of current and light, respectively. Then, after depositing an SiO ₂ film for passivation on the entire surface, an opening is provided in a contact region of the SiO ₂ film, and p-type electrodes 60 and 61 are deposited. On the back surface of the substrate 51, an n-type electrode 62 is formed.

According to the present manufacturing method, the plane layout of the striped laminated structure is defined in two mask forming steps. In addition, the necessary semiconductor layer can be completely grown only by performing one crystal growth step after the grating formation step. By changing the width of the mask opening between the region where the light emitting unit 71 is formed and the region where the light modulating unit 72 is formed, a multilayer structure that is self-aligned with the opening can be easily formed. Further, according to the present manufacturing method, the crystal growth with the largest load in the manufacturing process can be performed in one continuous step, and as a result, a complicated integrated structure can be formed by a very simple process.

(Embodiment 11) Next, referring to FIG. 26, a distributed Bragg reflection laser device (DB) according to the present invention will be described.
R laser device) will be described. FIG. 26 shows a cross section along the cavity direction of the DBR laser device of the present embodiment.

[0209] The DBR laser device of FIG.
It has a configuration similar to the FB laser device. The difference is that the n-InAsP layer 152 of the present embodiment forms a diffraction grating (DBR) for distributed black reflection instead of a diffraction grating for distributed feedback. n-InGa
The P layers 152 are periodically arranged at a pitch of 243 nm ,
It is surrounded in the circumferential Rio InP. The DBR diffraction grating is provided in the waveguide unit 70. Of the light formed by the light emitting section 71, light having a selected wavelength is reflected by the reflector of the waveguide section 70, and oscillates at a single wavelength.

Undoped InGaAs MQW Active Layer 56
Has a structure similar to that of the active layer 56 of FIG. 21 and generates laser light having a wavelength of 1.55 μm. In the present embodiment,
The band gap of the AsP layer 152 is adjusted so as not to absorb laser light. Therefore, a structure (Bragg reflector) in which the refractive index changes periodically is formed in the waveguide unit 70 by the plurality of InAsP layers 152. No electrode is required on the waveguide section 70. However, if an electrode is provided on the waveguide section 70, a forward bias is applied, and a current flows, the refractive index difference of the diffraction grating changes according to the amount of current, so that the wavelength of the laser light can be tuned. It is.

(Embodiment 12) Next, another embodiment of the DBR laser device according to the present invention will be described with reference to FIG. FIG. 27 shows a cross section along the cavity direction of the DBR laser device of the present embodiment.

The DBR laser device shown in FIG.
It has a configuration similar to a BR laser device. The difference is that the phase control electrode 70a
And lies in the wavelength tuning electrode 70b are al provided. The phase control electrode 70a is arranged on a region of the waveguide unit 70 where no diffraction grating is provided.

When the forward voltage applied between the wavelength tuning electrode 70b and the electrode 62 is increased, suddenly,
The oscillation wavelength may change discontinuously. The phase control electrode 70a functions to prevent this. If a forward voltage is applied between the phase control electrode 70a and the electrode 62, a discontinuous change in the oscillation wavelength is prevented.

In the above embodiment, InGaAsP /
Although the description has been given of the semiconductor laser having an oscillation wavelength of 1.30 μm using an InP-based material, the present invention can be applied to a semiconductor laser of another wavelength such as a wavelength of 1.55 μm. Also,
The InAsP layer does not necessarily have to be an absorption layer for the emission wavelength, and may be used for a refractive index type diffraction grating. The band gap, the layer thickness and the like of each semiconductor layer are not limited to the numerical values of the embodiments as long as they are in accordance with the gist of the present invention. Al
The present invention can be applied to other material systems such as GaAs / GaAs.

[0215]

In the semiconductor laser of the present invention, and small semiconductor portion size with a triangular shape projecting toward the substrate,
Since the small-sized semiconductor portions provided separately in the concave and convex portions are uniform, variations between the elements are extremely small. When the semiconductor laser of the present invention is a gain-coupled distributed feedback semiconductor laser device, the probability of oscillating at a single wavelength is high, and even for return light from outside the laser, the mode does not change and noise does not change. strong. According to the method for manufacturing a semiconductor laser device of the present invention, the periodic absorption layer is formed without relying on etching, so that the semiconductor layer grown thereafter can be of high quality and the reliability is excellent for a long time. ing. Further, since the light absorption layer is formed by growth, not by etching, the control of the absorption layer can be performed with high accuracy. The manufacturing process is also very easy and a versatile process.

The semiconductor laser of the present invention is
In the case of a body laser device, a low chirp light source having a high degree of freedom in designing the spectral line width can be obtained with a high yield. A single-wavelength light source with ultra-low chirp characteristics can be provided with a very simple manufacturing process or high applicability, and its practical value is great.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a DFB laser device according to the present invention, with a part being cut away so that an internal structure can be seen.

FIGS. 2A to 2E are process cross-sectional views illustrating a method for manufacturing the DFB laser of FIG. 1;

FIGS. 3A to 3C are cross-sectional views showing details of main steps used in a method of manufacturing a DFB laser according to the present invention.

FIG. 4 is a photoluminescence spectrum from an InAsP absorption layer formed by the method of the present invention.

FIG. 5 is a diagram illustrating a method for controlling the band gap energy of an InAsP absorption layer.

FIG. 6 is a diagram illustrating a diffraction grating in which an InGaP layer refractive index compensation layer is inserted.

FIG. 7 is a diagram illustrating current-light output characteristics of a DFB laser device according to the present invention.

FIG. 8 is a diagram illustrating spectral characteristics of a DFB laser device according to the present invention.

FIG. 9 is a perspective view showing another embodiment of the DFB laser device according to the present invention, with a part cut away so that the internal structure can be seen.

FIGS. 10A to 10F are process cross-sectional views illustrating a method of manufacturing the DFB laser of FIG. 9;

FIG. 11 is a perspective view showing still another embodiment of the DFB laser device according to the present invention, with a part being cut away so that the internal structure can be seen.

12A to 12F are process cross-sectional views illustrating a method for manufacturing the DFB laser of FIG. 11;

FIG. 13 is a perspective view showing still another embodiment of the DFB laser device according to the present invention, with a part being cut away so that an internal structure can be seen.

14A to 14F are process cross-sectional views illustrating a method for manufacturing the DFB laser of FIG. 13;

FIG. 15 is a perspective view showing still another embodiment of the DFB laser device according to the present invention, with a part cut away so that the internal structure can be seen.

16A to 16F are process cross-sectional views illustrating a method for manufacturing the DFB laser of FIG. 15;

FIGS. 17A to 17D are process cross-sectional views illustrating an invention in which a refractive index compensation layer is formed on both sides of an InAsP absorption layer.

FIG. 18 is a cross-sectional view illustrating a conventional DFB laser device.

19A to 19C are process cross-sectional views illustrating a conventional method for manufacturing a diffraction grating.

FIG. 20 is a sectional view showing still another embodiment of the DFB laser device according to the present invention.

FIG. 21 is a sectional view showing still another embodiment of the DFB laser device according to the present invention.

FIG. 22 is a sectional view showing still another embodiment of the DFB laser device according to the present invention.

FIG. 23 is a sectional view showing still another embodiment of the DFB laser device according to the present invention.

FIG. 24 is a sectional view showing still another embodiment of the DFB laser device according to the present invention.

FIG. 25A is a cross-sectional view showing a semiconductor substrate having projections and depressions, FIG. 25B is a plan view showing a layout of a stripe mask, and FIG. 25C shows a state in which an InAsP layer is formed. Sectional view.

FIG. 26 is a sectional view showing an embodiment of a DBR laser device according to the present invention.

FIG. 27 is a sectional view showing another embodiment of the DBR laser device according to the present invention.

[Explanation of symbols]

Reference Signs List 1 n-type InP substrate 2 diffraction grating 3 InAsP absorption layer 4 n-type InP cladding layer 5 n-type InGaAsP (λg = 1.05 μm) optical waveguide layer 6 strained multiple quantum well active layer 7 p-type InGaAsP (λg = 1.05 μm) Optical waveguide layer 8 p-type InP current blocking layer 9 n-type InP current blocking layer 10 p-type InP buried layer 11 p-type InGaAsP (λg = 1.3 μm) contact layer 12 SiO2 insulating film 13 Au / Zn electrode 14 Au / Sn electrode Reference Signs List 15 p-type InP cladding layer 16 p-type InGaAsP (λg = 1.3 μm) cap layer 17 second p-type InP cladding layer 18 InGaP refractive index compensation layer 21 n-type InP substrate 22 diffraction grating 23 n-type InGaAsP absorption layer 24 n -Type InP protective layer 25 n-type InP clad layer 26 n-type InGaAsP optical waveguide layer 27 InGaAs well layer 28 In aAsP barrier layer 29 active layer 30 p-type InGaAsP optical waveguide layer 31 p-type InP cladding layer 32 n-type InGaAsP refractive index compensation layer (thickness 50n
m, λg = 1.2 μm) 33 n-type InP cap layer (20 nm thick) 51 n-InP substrate 52 absorption type diffraction grating 55 optical waveguide layer 56 active layer 57 light modulation layer 58 p-InP cladding layer 59 p-InGaAsP Contact layer 60, 61 P-type electrode 62 N-type electrode 71 Light emitting section 72 Light modulating section

Continuing on the front page (72) Inventor Masato Ishino 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. References JP-A-4-155986 (JP, A) JP-A-2-143586 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 3/18

Claims (32)

(57) [Claims] 1. A semiconductor laser device comprising: an InP substrate; and a multilayer structure formed on the InP substrate, wherein the multilayer structure includes at least an active layer for emitting laser light, and the laser. A periodic structure for applying light distribution feedback to light,
Wherein the periodic structure has a cross section perpendicular to the main surface of the InP substrate and parallel to the resonator direction of the semiconductor laser device.
A plurality of semiconductor portion having a triangular shape projecting in the direction of the P substrate, the band gap energy of the semiconductor portion constituting the said periodic structure, the light emitted through the light distributed feedback of the active layer The semiconductor laser device is set to be equal to or less than the energy of the semiconductor laser. 2. A semiconductor laser device comprising: an InP substrate; and a multilayer structure formed on the InP substrate, wherein the multilayer structure has at least an active layer for emitting laser light, and the laser. A periodic structure for applying light distribution feedback to light,
Wherein the periodic structure is formed in the multilayer structure periodically and the In
Comprising a plurality of irregularities and the recess of the projecting portion relative to the P substrate, a semiconductor portion which is provided separately within the recess of each of the plurality of irregularities, and the semiconductor constituting the said periodic structure The semiconductor laser device, wherein a band gap energy of the portion is set to be equal to or less than an energy of light emitted from the active layer via light distribution feedback. 3. A semiconductor laser device comprising: an InP substrate; and a multilayer structure formed on the InP substrate, wherein the multilayer structure includes at least an active layer for emitting laser light, and the laser. A periodic structure for applying light distribution feedback to light,
Wherein the periodic structure has a cross section perpendicular to the main surface of the InP substrate and parallel to the resonator direction of the semiconductor laser device.
A plurality of semiconductor portion having a triangular shape projecting in the direction of the P substrate, the band gap energy of the semiconductor portion constituting the said periodic structure, the light emitted through the light distributed feedback of the active layer The semiconductor laser device, wherein the semiconductor portion is set to be equal to or larger than the energy of the semiconductor laser, and the semiconductor portion is InAsP. 4. A semiconductor laser device comprising: an InP substrate; and a multilayer structure formed on the InP substrate, wherein the multilayer structure includes at least an active layer for emitting laser light, and the laser. A periodic structure for applying light distribution feedback to light,
Wherein the periodic structure is formed in the multilayer structure periodically and the In
Comprising a plurality of irregularities and the recess of the projecting portion relative to the P substrate, a semiconductor portion which is provided separately within the recess of each of the plurality of irregularities, and the semiconductor constituting the said periodic structure A semiconductor laser device, wherein the bandgap energy of the portion is set to be equal to or larger than the energy of light emitted from the active layer via the light distribution feedback, and the semiconductor portion is InAsP. . 5. The semiconductor laser device according to claim 1, wherein the semiconductor portion forming the periodic structure is InAsP. 6. The semiconductor laser device according to claim 1, wherein said periodic structure is provided between said InP substrate and said active layer. 7. The semiconductor portion forming the periodic structure, the first semiconductor material having a band gap energy smaller than the energy of light emitted from the active layer via light distribution feedback; A second semiconductor material having a bandgap energy greater than the energy;
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is formed from at least two types of materials. 8. The first semiconductor material having a band gap energy smaller than the energy of light emitted from the active layer via light distribution feedback, wherein the semiconductor portion forming the periodic structure includes: The semiconductor laser device according to claim 1, wherein the semiconductor laser device is formed of at least two types of materials: a second semiconductor material that compensates for a refractive index of the semiconductor material. 9. The periodic structure includes a first semiconductor portion made of a first semiconductor material and a second semiconductor portion made of a second semiconductor material. And the second semiconductor portion are alternately arranged along the resonator direction, and the first semiconductor portion is
3. The semiconductor laser device according to claim 1, wherein the semiconductor laser device has a cross section perpendicular to the main surface of the InP substrate and parallel to the resonator direction, the shape protruding in the direction of the InP substrate. 4. 10. The semiconductor device according to claim 1, wherein a band gap energy of the first semiconductor portion of the periodic structure is set to be smaller than an energy of light emitted from the active layer via light distribution feedback. 10. The semiconductor laser device according to claim 9, wherein the band gap energy of the second semiconductor portion is set to be larger than the energy of the light emitted from the active layer via the light distribution feedback. 11. The semiconductor laser device according to claim 7, wherein an average refractive index of said semiconductor portion constituting said periodic structure is substantially equal to a refractive index of InP. 12. The semiconductor laser device according to claim 7, wherein said first semiconductor material is InAsP, and said second semiconductor material is InGaP. 13. A step of forming a plurality of grooves arranged periodically on the surface of an InP crystal, and heat-treating the InP crystal in an atmosphere in which at least phosphine and arsine are mixed. A step of depositing InAsP in each of the plurality of grooves, and a step of forming a multilayer structure including an active layer on the InP crystal. 14. A step of forming, on a substrate, a multilayer structure including an active layer and an uppermost layer being an InP layer; and a step of forming a plurality of periodically arranged grooves on a surface of the InP layer. Heat-treating the multilayer structure in an atmosphere in which phosphine and arsine are mixed , and depositing InAsP in each of the plurality of grooves, a method for manufacturing a semiconductor laser device. 15. An unevenness is formed on the surface of an InP crystal, and the InP crystal having the unevenness is formed at least by phosphine.
A heat treatment in an atmosphere in which is mixed with arsine to form InAsP in the concave and convex portions of the irregularities. 16. The crystal growth method according to claim 15, wherein the band gap of said InAsP is changed by changing the flow rate of arsine with respect to the flow rate of phosphine . 17. A light emitting section for generating laser light, a light modulating section optically coupled to the light emitting section and modulating the laser light, and a striped multilayer structure including the light emitting section and the light modulating section. A semiconductor laser device comprising: a substrate supporting the stripe-shaped multilayer structure; wherein the light-emitting portion includes an active layer and the stripe along an optical axis direction.
Periodically formed in the shape of a multi-layered structure and protruded from the substrate
A plurality of irregularities portions and recesses, each of the plurality of irregularities
The anda semiconductor portion which is provided separately in the recess, the band gap energy of the semiconductor portion is preset from the active layer below the energy of the light emitted through the light distributed feedback, the The semiconductor laser device, wherein the light modulation unit has a light modulation layer whose optical characteristics change according to a modulation signal. 18. A light emitting unit for generating a laser beam, a light modulating unit optically coupled to the light emitting unit and modulating the laser beam, and a striped multilayer structure including the light emitting unit and the light modulating unit. A substrate supporting the stripe-shaped multilayer structure, wherein the light-emitting portion comprises: an active layer; and a stripe extending along an optical axis direction.
Periodically formed in the shape of a multi-layered structure and protruded from the substrate
A plurality of irregularities portions and recesses, each of the plurality of irregularities
Anda semiconductor portion which is provided separately in the recess, the band gap energy of the semiconductor portion is larger same or than the energy of the light emitted through the light distributed feedback of the active layer Wherein the semiconductor portion is InAsP, and the light modulation section has a light modulation layer whose optical characteristics change according to a modulation signal. 19. The semiconductor device according to claim 1, wherein the semiconductor portion provided separately in each of the plurality of concave and convex portions has an absorption type in which an absorptivity of light emitted from the active layer changes periodically along an optical axis direction. The semiconductor laser device according to claim 17 , wherein the semiconductor laser device forms a grating. 20. The striped multilayer structure includes a multiple quantum well layer; the active layer is formed from a first portion of the multiple quantum well layer; and the light modulation layer is a multiple quantum well layer. is formed from the second portion of the layer, the semiconductor laser device according to claim 17 or 18. 21. The active layer and the light modulation layer are connected by a third portion of the multiple quantum well layer,
21. The semiconductor laser device according to claim 20 , wherein said third portion is located between said first portion and said second portion of said multiple quantum well layer. 22. The semiconductor laser device according to claim 21 , wherein said first portion of said multiple quantum well layer is thicker than said second portion of said multiple quantum well layer. 23. The semiconductor device according to claim 17 , wherein the semiconductor portion is formed on periodic irregularities formed on a surface of the substrate.
19. A semiconductor laser device according to item 18 . 24. A comprises further optical waveguide layer provided between the semiconductor portion and the active layer, a semiconductor laser device according to claim 17 or <br/> others 18. 25. The image display device further comprising: first voltage applying means for applying a substantially constant voltage to the light emitting unit; and second voltage applying means for applying a modulation voltage to the light modulation unit. the semiconductor laser device according to claim 17 or 18. 26. The semiconductor part is InAsP.
The semiconductor laser device according to claim 17 . 27. A light-emitting portion for generating a laser beam, an optical waveguide portion optically coupled to the light-emitting portion, and through which the laser beam propagates, and a striped multilayer structure including the light-emitting portion and the optical waveguide portion. A substrate that supports the striped multilayer structure, wherein the light emitting unit includes an active layer that emits the laser light, and the optical waveguide unit has a refractive index in an optical axis direction. A Bragg reflector that varies periodically along the surface thereof, wherein the Bragg reflector separates into recesses of the periodic relief structure.
A semiconductor laser device having a semiconductor portion formed by reflecting light of a selected wavelength out of light emitted from the active layer toward the active layer. 28. The semiconductor part is InAsP,
A semiconductor laser device according to claim 27 . 29. The semiconductor laser device according to claim 28 , wherein said InAsP has a band gap energy large enough not to absorb said laser light. 30. The optical waveguide unit includes a wavelength tuning unit for adjusting a wavelength of the laser light.
A semiconductor laser device according to claim 27 . 31. The optical waveguide unit includes a phase tuning unit for adjusting a phase of the laser light.
The semiconductor laser device according to claim 30 . 32. A light emitting section for generating laser light, a light modulating section optically coupled to the light emitting section and modulating the laser light, and a striped multilayer structure including the light emitting section and the light modulating section. A semiconductor laser device comprising: a substrate supporting the stripe-shaped multilayer structure; wherein the light-emitting portion has an active layer, and the light modulation portion has light whose optical characteristics change according to a modulation signal. An absorption type diffraction grating that is periodically arranged along the optical axis direction is formed in the light emitting portion and the light modulating portion, and the laser light from the light emitting portion is A semiconductor laser device that hardly diffracts by the absorption type diffraction grating of the light modulation unit.