JPH07335977A - Semiconductor laser, optical integrated device, and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Objective] The extinction ratio is reduced and the insertion loss is increased by making the bandgap of the multiple quantum well layer in the boundary region such as the boundary between the modulator region and the LD region sharply change. And deterioration of the band gap change Δ
It is an object of the present invention to provide a structure and a manufacturing method thereof which can increase the Eg and can be applied to various optical integrated devices and can easily obtain an optical integrated device including a so-called chirped diffraction grating or pitch modulation diffraction grating. A multi-quantum well layer 4 is crystal-grown on a substrate 1 on which a ridge 31 whose ridge width and / or ridge spacing changes along the waveguide direction is formed in advance, and a band gap LD region and a modulator region (separation). The region) forms a waveguide that changes abruptly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, an optical integrated device and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional modulator integrated laser diode (LD). FIG. 9 (a) is a perspective view and FIG. 9 (b) is a sectional view. For example, ELECTRONICS LETTERS 7th Novenber V
ol.27, P2138-P2140. In the figure, 1 is an n-InP substrate, 2 is a diffraction grating formed on the n-InP substrate 1, 3 is an optical guide layer made of InGaAsP, and 41 is InG.
Multiple quantum well layer (MQW) made of aAs / InGaAsP, 5 is p-In
Clad layer made of p, 6 is a cap layer made of p-InGaAsP, 33 is a current block layer made of Fe-doped InP, 7
Is a P electrode of the modulator, 8 is a P electrode of the LD, 9 is a common electrode that works in common with the P electrode 7 of the modulator and the P electrode 8 of the LD,
The optical guide layer 3, the multiple quantum well layer (MQW) 41, and the cladding layer 5 are sequentially stacked on the flat substrate 1 to form a mesa stripe, and then a current block layer 33 is grown on both sides of the mesa stripe. .

Next, a method of manufacturing the modulator integrated LD having the above structure will be described. First, the diffraction grating 2 is formed in the region on the substrate 1 where the LD is to be formed. Next, as shown in FIG. 10, a mask made of, for example, a rectangular SiO ₂ film of about 200 μm × 400 μm is formed so as to sandwich a region of about 200 μm width where an LD is to be formed. Subsequently, metal organic chemical vapor deposition (MOC
VD) optical guide layer 3 made of InGaAsP, InGaAs /
An MQW layer 41 made of InGaAsP, a clad layer 5 made of P-InP, and a cap layer 6 made of P-InGaAsP are sequentially grown selectively to form a growth layer.

At this time, in the LD region sandwiched by the SiO ₂ films, the raw material species are diffused on the SiO ₂ mask and are additionally supplied, so that the LD 2 region is not affected by the SiO ₂ mask. Also, the growth rate becomes faster, and as a result, the layer thickness of each layer becomes 1.5 to 2 times thicker than the modulator region.

Next, to form a waveguide, the growth layer is set to L.
A predetermined width is formed from the area D to the area of the modulator. After that, the p-electrode 7 in the modulator region, the p-electrode 8 in the LD region, and the common electrode 9 made of metal such as aluminum are formed on the modulator region, the LD region, and the surface facing them.

Next, the operation of the modulator integrated LD constructed and manufactured as described above will be described. InGaAs / InG
The MQW layer 41 made of aAsP operates as an active layer in the LD region and as an absorption layer in the modulator region.
When a forward bias voltage is applied between the p electrode 8 and the common electrode 9 in the LD region, carriers are injected into the MQW layer 41 made of InGaAs / InGaAsP, and laser oscillation occurs at a wavelength determined by the effective band gap of this layer and the diffraction grating 2. Happens.

Since the effective bandgap of the MQW layer 41 depends on the layer thickness of the well layer in the MQW layer 41, the thinner the well layer thickness, the wider the bandgap. As described above, the layer thickness of the well layer becomes thicker in the LD region than in the modulator region during the selective growth by the MOCVD method. Therefore, the bandgap (Eg ₁ ) in the LD region is narrower than the bandgap (Eg ₂ ) in the modulator region (Eg ₂
> Eg ₁ ). LD oscillation light (wavelength λ _{1 =} 1.24 / Eg ₁ )
Since Eg ₂ > Eg _{1 in the} modulator region, it is taken out from the end face without being absorbed. When a reverse bias is applied to the P electrode in the modulator region, the quantum confined Stark effect of the MQW layer 41 shifts the absorption edge by excitons to the longer wavelength side, and the effective band gap Eg ₂ ′ is Eg ₂ ′ <Eg. _{On the} contrary to ₁ , the value in the modulator region is smaller than the value in the LD region, so the laser light is absorbed by the modulator and extinguished. Therefore, the laser light is turned on / off by modulating the voltage applied to the modulator.
can do.

[0008]

The modulator integrated L described above is used.
D and its manufacturing method have the following problems.
The thickness of the MQW layer 41 in the LD region is set to the MQ in the modulator region.
As a means for making the W layer 41 thicker than the layer thickness, the raw material species supplied on the mask are diffused and supplied to the LD region sandwiched between the masks, and the growth rate of the LD region becomes faster than that of the modulator region. We are utilizing the phenomenon. However, according to this method, a transition region in which the layer thickness gradually changes over a width of about 100 μm is formed at the boundary between the LD region affected by the mask and the modulator region not affected by the mask. This is because the distance that the raw material species diffuse from the mask is ~ 50.
This is because it reaches over μm.

In the above-mentioned transition region, the effective bandgap of the MQW layer 41 (waveguide layer) gradually changes as the layer thickness changes, and while light propagates through the transition region. Is absorbed by and attenuates. As a result, the modulator-integrated LD suffers deterioration such as a decrease in extinction ratio and an increase in insertion loss.

Further, according to the above manufacturing method, there is a limit to the amount of change in bandgap. The appropriate amount of change ΔEg of the bandgap is about 30 meV in the LD integrated with the modulator, but other optical integrated devices, for example, a waveguide integrated laser or optical such as a distributed reflection laser diode (DBR-LD). In the case of an integrated circuit or the like, it is necessary to set ΔEg to about 100 meV or more in order to reduce the absorption loss in the waveguide. However, the method of utilizing the diffusion phenomenon of the raw material species from the mask like the above manufacturing method has a limit in the value of ΔEg, and it is difficult to realize various optical integrated devices other than the modulator integrated LD. .

Further, for example, in a wavelength tunable DBR-LD provided with a so-called chirped diffraction grating or a pitch modulation diffraction grating in which the pitch of the diffraction grating is partially changed or gradually changed, for example, a diffraction grating with a changed pitch. Is difficult to manufacture, and it is necessary to use a method such as electron beam exposure in which diffraction gratings are drawn one by one,
Very long and poor throughput.

FIG. 11 is a cross-sectional view showing the structure of a conventional / 4 shift DBR laser. In order to further ensure the characteristic that the DFB laser emits at a single wavelength, the phase of the pitch of the diffraction grating is set to the resonator. Although it is shifted by a quarter wavelength in the central part, the light density distribution becomes stronger at the center of the resonator as shown in FIG. 12 (due to a phenomenon called spatial spatial hole burning in the axial direction) and is non-uniform. As a result, the laser characteristic is deteriorated such that the wavelength spectrum line width is widened or the linearity of the optical output-current characteristic is deteriorated.

FIG. 12 is a sectional view of the wavelength tunable DBR-LD in the waveguide direction. The DBR region is not electrically excited and the light generated in the LD region is absorbed and attenuated in the DBR region. Waveguide layer 12 to reduce attenuation
It is necessary to make the band gap of 3 larger in the DBR region than in the LD region. Further, although a variable width of about 10 nm is required in the wavelength division multiplexing optical switching / optical communication system, it cannot be realized with a diffraction grating having a constant pitch.

The present invention solves the above problems and reduces the layer thickness transition region where the layer thickness of the quantum well layer changes in the boundary region such as the boundary between the modulator region and the LD region, thereby reducing the boundary region. The bandgap changes sharply and suppresses deterioration such as a decrease in extinction ratio and increase in insertion loss, and can be applied to various optical integrated devices by increasing the change in bandgap ΔEg. It is an object of the present invention to provide a structure and a manufacturing method for easily obtaining an optical integrated device including a grating or a pitch modulation diffraction grating.

[0015]

The invention according to claim 1 is
The multiple quantum well layer is grown according to the ridge width and / or the ridge spacing by crystal-growing a multiple quantum well layer on a substrate on which a ridge whose ridge width and / or ridge spacing changes along the waveguide direction is formed. A semiconductor laser or an optical integrated device in which a waveguide whose bandgap is changed by changing the layer composition and / or the layer thickness is formed.

According to a second aspect of the present invention, in the semiconductor laser or the optical integrated device according to the first aspect, a layer thickness control mask for sandwiching a ridge is provided on a substrate, and a multiple quantum well layer is crystal-grown. is there.

The invention according to claim 3 is the ridge width and //
Alternatively, the optical guide layer is crystal-grown on a substrate on which a ridge whose ridge spacing changes along the resonator direction is formed in advance to change the layer thickness and / or composition of the optical guide layer in the resonator direction. This is a semiconductor laser or an optical integrated device in which a diffraction grating having a constant pitch is formed on the upper surface or the lower surface of the guide layer and the effective pitch of the diffraction grating is changed in the cavity direction.

According to a fourth aspect of the present invention, in the semiconductor laser or the optical integrated device according to the third aspect, a region where the layer thickness and / or composition of the optical guide layer gradually changes in the waveguide direction is formed, and A diffraction grating having a constant pitch is formed.

According to a fifth aspect of the present invention, in the semiconductor laser or the optical integrated device according to the third aspect, a phase adjusting region in which the layer thickness and / or composition of the optical guide layer is different in a part in the waveguide direction is formed, In addition, a diffraction grating having a constant pitch is formed.

According to a sixth aspect of the present invention, a semiconductor laser or an optical integrated device is provided in which a ridge having a ridge width and / or a ridge spacing varying in the waveguide direction is previously formed on a substrate, and a multiple quantum well layer is crystal-grown on the ridge. It is a device manufacturing method.

The invention according to claim 7 is the method for manufacturing a semiconductor laser or an optical integrated device according to claim 6,
A layer thickness control mask sandwiching the ridge is provided to control the layer thickness of the multiple quantum well layer.

According to an eighth aspect of the present invention, a ridge whose ridge width and / or ridge spacing changes in the resonator direction is formed in advance on the substrate, and the optical guide layer is crystal-grown on the ridge and the optical guide layer is formed. It is a method for manufacturing a semiconductor laser or an optical integrated device, in which a diffraction grating having a constant pitch is formed.

[0023]

According to the first and sixth aspects of the present invention, a ridge whose ridge width and / or ridge spacing varies in the waveguide direction is formed in advance on the substrate, and a multiple quantum well layer is crystal-grown on the ridge. Changes the composition and / or the layer thickness of the quantum well layer depending on the ridge width and / or the ridge spacing, so that the transition region of the quantum well layer in the boundary region such as the boundary between the modulator region and the LD region is reduced, The band gap in the boundary region can be changed sharply, and deterioration such as a decrease in extinction ratio and an increase in insertion loss can be suppressed.

According to the second and seventh aspects of the present invention, since the layer thickness control mask sandwiching the ridge can be provided to increase the difference in the layer thickness between the regions, the change ΔEg in the band gap can be increased. It is possible to deal with various optical integrated devices.

According to the inventions of claims 3 and 8, the optical guide layer is crystal-grown on the substrate on which the ridge whose ridge width and / or ridge spacing changes along the cavity direction is formed in advance. Since the layer thickness and / or composition of the optical guide layer in the cavity direction can be changed, a so-called chirped diffraction grating or pitch modulation can be achieved by forming a diffraction grating with a constant pitch on the upper surface or the lower surface of the optical guide layer. Easily obtain semiconductor laser and integrated optical device with diffraction grating equivalent to diffraction grating

According to the invention of claim 4, the pitch of the diffraction grating is gradually changed by gradually changing the layer thickness and / or the composition of the light guide layer even if the pitch of the diffraction grating is constant. Is equivalent to
A wavelength tunable semiconductor laser and an optical integrated device can be easily obtained.

According to the fifth aspect of the present invention, even if the pitch of the diffraction grating is constant, the pitch of the diffraction grating can be changed by forming the phase adjustment regions where the layer thickness and / or the composition of the light guide layer are partially different. Since a different one and an equivalent one are formed in some regions, a semiconductor laser and an optical integrated device with uniform light density can be easily obtained.

[0028]

【Example】

Example 1. FIG. 1 is a modulator integrated LD showing an embodiment of a semiconductor laser and an optical integrated device according to the present invention.
(A) is a perspective view, (b) is a II sectional view. In the figure, 1 is a substrate made of n-InP, 2 is a diffraction grating formed in the LD region of the substrate 1, 31 is a ridge made of the same member as the substrate 1, 3 is an optical guide layer made of n-InGaAsP, 4 is a InGa
Multiple quantum well layer (MQW) made of As / InGaAsP, 5 is p-InP
Clad layer composed of 6; cap layer composed of p-InGaAsP; 33 current blocking layer; 7 P electrode of modulator; 8 L
The D p electrode, 9 is an n electrode that works in common with the modulator p electrode 7 and the LD p electrode 8, and the MQW layer 4 is an LD.
The region and the modulator region differ in composition and / or layer thickness.

Next, the modulator integrated LD shown in FIG.
The manufacturing method of will be described with reference to FIG. 2A is a plan view, and FIGS. 2B to 2F are sectional views. First, n-InP
The diffraction grating 2 is formed on the surface of the LD region on the substrate 1. Next, in the modulator area as shown in FIG.
A mask 30 made of SiO ₂ having a width changed in the direction of the narrow waveguide in the region D is formed by film formation and photolithography.

Subsequently, etching is performed to form a ridge 31 under the mask 30, as shown in FIG.
Similar to the width of the mask 30, the width of the ridge 31 is wide in the modulator region, narrow in the LD region, and varies in the waveguide direction. For example, the width of the ridge 31 in the modulator region. But
6 μm, the width of the groove between the ridges 31 is 6 μm, the width of the ridge 31 is 3 μm in the LD region, and the width of the groove between the ridges 31 is 3 μm.
Has become.

Next, after all the mask 30 is removed, as shown in FIG. 2C, InGa is sequentially formed by MOCVD.
An optical guide layer 3 made of As, an MQW layer 4 made of InGaAs or InGaAsP, a P-In clad layer 5 and a cap layer 6 made of P-InGaAsP are grown to form a growth layer. At this time, the effective band gap of the MQW layer 4 formed on the ridge 31 becomes narrower as the width of the ridge 31 and the width of the groove between the ridges 31 become narrower. This phenomenon has been confirmed experimentally, and is reported in Proceedings of the Joint Lecture of Applied Physics (Spring 1993) No. 1 p265, Lecture No. 30a-ZR-10. As described above, the principle that the bandgap (wavelength) of the MQW layer 4 changes depending on the width or the interval of the ridge 31 is not sufficiently clear, but the composition and / or the layer thickness of the MQW layer 4 changes depending on the width or the interval of the ridge 31. Therefore, since there is no influence of a long diffusion length on the mask as in the conventional case, the width of the transition region where the band gap between the LD region and the modulator region gradually changes can be significantly reduced, and the ridge 31 The band gap can be abruptly changed at the portion where the width of the band changes, that is, at the boundary between the LD region and the modulator region.

After the growth layer is formed on the ridge 31, the following manufacturing steps are further performed to form a waveguide, narrow the current in the LD portion to the active layer, and reduce the capacitance of the modulator.

As shown in FIG. 2 (d), a stripe-shaped mask ₂ of SiO _{2 having} a width of about 2 μm is formed at the center of the growth layer of the ridge by film formation and photolithography.
As shown in (e), portions other than the mask 32 are removed by a method such as dry etching to form a mesa stripe.

Next, as shown in FIG. 2 (f), MOCV
Fe doping using the mask 32 as a selective mask by the D method
A current blocking layer 33 made of InP is grown on both sides of the mesa stripe. In this way, the MQW layer 4 has a width of 2 μm.
A continuous buried waveguide is formed, and
Since the doped InP has a high resistance, the current concentrates in the active layer in the mesa stripe portion in the LD region. Further, since the current block layer 33 made of Fe-doped InP does not include a pn junction, it is possible to reduce the parasitic capacitance of the modulator and enable high speed modulation.

Finally, the mask 32 is removed and, as shown in FIG. 1, the p electrode 7 in the modulator region and the p electrode 8 in the LD region.
Then, the n-electrode 9 that works in common with the p-electrode 7 in the modulator region and the p-electrode 8 in the LD region is formed and completed.

According to the configuration and manufacturing method of this embodiment,
As described above, the width of the transition region in which the band gap gradually changes between the LD region and the modulator region of the MQW layer 4 can be significantly reduced, and as a result, the propagation loss due to absorption of light in the transition region can be reduced. It is possible to greatly reduce, improve the extinction ratio and reduce the insertion loss of the modulator integrated LD.

In this embodiment, the ridge 31 is
The method of forming the substrate 1 by etching has been described.
The present invention is not limited to this, and the ridge 31 may be previously formed on the substrate 1 before the growth layer is formed.

Example 2. In the case of modulator integrated LD,
When a reverse bias is applied to the modulator, the band gap in the modulator region is smaller than that in the LD region (E
Since it is necessary that g ₂ ′ <Eg ₁ ), the bandgap variation ΔEg is appropriate to be about 30 meV. However, when simply integrating the LD and the waveguide, increasing ΔEg as much as possible reduces the absorption loss. It's good because you can.

This embodiment relates to a wavelength tunable DBR-LD in which an LD active region and a waveguide are integrated. Figure 3
FIG. 4 is a cross-sectional view of the wavelength tunable DBR-LD of this embodiment in the waveguide direction. In the figure, 1 is a substrate made of n-InP and has a ridge shape, 2 is a diffraction grating formed in the DBR region of the substrate 1, 3 is an optical guide layer made of InGaAsP, and 4 is InGaAs.
Multiple quantum well layer (MQW) made of / InGaAsP, 5 is a clad layer made of P-InP, 6 is a cap layer made of P-InGaAsP,
17 is a P electrode for wavelength tuning in the DBR region, 8 is an LD
P electrode of 9 and P electrode 7 for wavelength tuning and P of LD
The MQW layer 4 is an n-electrode that works in common with the electrode 8
The R region and the LD region differ in composition and / or layer thickness.

A method of manufacturing the wavelength tunable DBR-LD of this embodiment will be described. First, the diffraction grating 2 is formed on the surface of the DBR region on the n-InP substrate 1. Next, D as shown in FIG.
A mask 30 made of SiO ₂ having a wide width in the BR region and a narrow width in the LD region in the waveguide direction and a layer thickness control mask 61 sandwiching the LD region are formed by film formation and photolithography.

Then, as in the first embodiment, etching, growth layer formation, mesa stripe formation, current block layer formation, and formation of the n-electrode common to the p-electrode in each region are completed.

According to the structure and the manufacturing method of this embodiment,
In addition to the narrow band gap of the LD region due to the narrow width or spacing of the ridges 31, the LD region is sandwiched by the layer thickness control mask 61, so that the layer of the raw material species used for forming the growth layer is formed. Due to the diffusion phenomenon from the thickness control mask 61, the layer thickness of the LD region becomes thicker and the bandgap becomes narrower, so that the bandgap variation ΔEg can be increased, and the loss due to the absorption of light in the DBR waveguide region. Can be extremely small.

Example 3. In the first and second embodiments, the diffraction grating is formed by the concavo-convex pattern having a constant pitch. However, a diffraction grating whose pitch is partially changed or gradually changed is a chirped diffraction grating or a pitch modulation diffraction. It is called a lattice. These diffraction gratings have a larger variable wavelength width in the wavelength tunable LD and a uniform light density distribution in the resonator in the distributed feedback LD (DFB-LD), as compared with a diffraction grating with a constant pitch, to obtain a spectrum. This is effective for narrowing the line width.

Diffraction gratings with changed pitches are formed by a method in which diffraction grating patterns are drawn one by one by electron beam exposure, and it takes a very long time and throughput is poor. This embodiment provides a structure having substantially the same effect as a chirped diffraction grating and a manufacturing method thereof, using a pattern with a constant pitch that can be easily manufactured by an interference exposure method or the like.

FIG. 5 is a cross-sectional view showing the structure of this embodiment. In order to make the light density distribution in the resonator such as λ / 4 shift-DBR-LD uniform, the diffraction grating is formed in the central region of the resonator. It has a configuration equivalent to that having a phase adjustment region (PAR) having a long pitch. In the figure, a buffer layer 91 made of n-InP and InGaA are formed on a substrate 1 made of n-InP.
An MQW active layer 92 made of s / InGaAsP and a barrier layer 93 made of n-InP are sequentially grown and formed, and a diffraction grating 94 having a constant pitch is formed on the barrier layer 93 by an interference exposure method or the like, and then on the barrier layer 93. A pattern 62 made of a SiO ₂ film as shown in FIG. 6 is formed on the surface of the ridge and is etched to form a ridge having the same shape as the pattern 62 having a narrow width and a narrow space at the center. Optical guide layer 95 made of InGaAsP and clad layer 96 made of p-InP
Are grown and formed.

During the growth of the light guide layer 95, the thickness of the light guide layer 95 becomes thicker, the composition becomes longer wavelength, or the layer thickness becomes thicker at the central portion where the ridge width and spacing are narrow. It becomes a long wavelength. That is, it corresponds to an increase in the refractive index. The wavelength (Bragg wavelength) λ of the light reflected by the diffraction grating 94 is λ = (2n _r , where Λ is the pitch of the diffraction grating 94 and n _r is the refractive index.
/ M) Λ (m is an integer), the larger the refractive index n _r , the substantially same effect as the pitch of the diffraction grating 94 is obtained. FIG. 7 shows this, and the pitch is small in the portion where the width of the ridge is wide, and the pitch is large in the portion where the width of the ridge is narrow.

As a result, even if the pitch of the irregularities of the diffraction grating 94 is constant, the equivalent pitch of the diffraction grating 94 is larger in the central portion than on both sides thereof, and λ / 4 shift-DFB-
In the LD, the light density distribution in the resonator can be made uniform and the spectral line width can be narrowed. PAR12 of FIG.
The curves of 0 μm, 360 μm, and 600 μm show how the light density distribution becomes smaller when such a phase adjustment region is added.

Example 4. In the same manner as in Example 3, n-InP
N-InP buffer layer, InGaAs /
An MQW active layer made of InGaAsP and a P-InP barrier layer are sequentially grown and formed, and a diffraction grating having a constant pitch is formed on the P-InP barrier layer by an interference exposure method or the like. A pattern 63 made of such a SiO ₂ film is formed and etched to form a ridge having the same shape as the pattern 63 in which the ridge width gradually changes periodically in the DBR region. Similarly, an optical guide layer made of p-InGaAsP and a clad layer made of p-InP are grown by MOCVD.

During the growth of the light guide layer, the layer thickness of the light guide layer gradually changes in the LDB region where the ridge width and the interval gradually change, or the composition has a long wavelength to a short wavelength (from a large refractive index). Small) or the layer thickness changes and the composition also changes.

As a result, even if the pitch of the irregularities of the diffraction grating is constant, the equivalent pitch of the diffraction grating is such that the pitch gradually and periodically changes in the LD region, and the emission wavelength can be changed over a wide range. Variable wavelength DBR
-LD is obtained.

In Examples 3 and 4, the diffraction grating was formed on the substrate before growing the light guide layer, but the light guide layer was grown and the diffraction grating was formed on this light guide layer. Good.

The first to fourth embodiments are other optical integrated devices, for example, a device in which an LD and a waveguide are integrated, and further, LD + waveguide + photodiode, optical switch, coupler, optical amplifier or optical modulator, etc. It can be applied to all kinds of optical integrated devices.

[0053]

According to the inventions of claims 1 and 6,
By forming a ridge whose ridge width and / or ridge spacing varies in the waveguide direction in advance on the substrate and crystal-growing a multiple quantum well layer on the ridge, the quantum well layer of the quantum well layer is formed according to the ridge width and / or the ridge spacing. Since the composition and / or the layer thickness changes, the transition region of the quantum well layer in the boundary region such as the boundary between the modulator region and the LD region is made small, the bandgap of the boundary region is rapidly changed, and the extinction ratio It is possible to suppress deterioration such as a decrease and an increase in insertion loss.

According to the second and seventh aspects of the present invention, since the layer thickness control mask sandwiching the ridge is provided to increase the difference in the layer thickness between the regions, the change ΔEg in the band gap can be increased. It is possible to deal with various optical integrated devices.

According to the third and eighth aspects of the present invention, the optical guide layer is crystal-grown on the substrate on which the ridge whose ridge width and / or ridge spacing changes along the cavity direction is formed in advance. Since the layer thickness and / or composition of the optical guide layer in the cavity direction can be changed, a so-called chirped diffraction grating or pitch modulation can be achieved by forming a diffraction grating with a constant pitch on the upper surface or the lower surface of the optical guide layer. Easily obtain semiconductor laser and integrated optical device with diffraction grating equivalent to diffraction grating

According to the invention of claim 4, even if the pitch of the diffraction grating is constant, the pitch of the diffraction grating is gradually changed by gradually changing the layer thickness and / or composition of the light guide layer. Is equivalent to
A wavelength tunable semiconductor laser and an optical integrated device can be easily obtained.

According to the fifth aspect of the present invention, even if the pitch of the diffraction grating is constant, the pitch of the diffraction grating can be changed by forming the phase adjustment regions where the layer thickness and / or the composition of the light guide layer are partially different. Since a different one and an equivalent one are formed in some regions, a semiconductor laser and an optical integrated device with uniform light density can be easily obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a modulator integrated LD according to an embodiment of the present invention.

2A and 2B are a plan view and a cross-sectional view illustrating a method of manufacturing a modulator integrated LD according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a wavelength tunable DBR-LD according to another embodiment of the present invention.

FIG. 4 is a plan view illustrating a method of manufacturing a wavelength tunable DBR-LD according to another embodiment of the present invention.

FIG. 5 is a sectional view showing a chirped diffraction grating of the present invention.

FIG. 6 is a plan view illustrating a method for manufacturing a chirped diffraction grating of the present invention.

FIG. 7 is a plan view illustrating the principle of the chirped diffraction grating of the present invention.

FIG. 8 is a plan view illustrating a method of manufacturing a wavelength tunable DBR-LD using the chirped diffraction grating of the present invention.

FIG. 9 is a sectional view of a conventional modulator integrated LD.

FIG. 10 is a plan view illustrating a method for manufacturing a conventional modulator integrated LD.

FIG. 11 is a sectional view showing a structure of a conventional λ / 4 shift-DFB laser.

FIG. 12 is a light density distribution in a resonator of λ / 4-DFB.

[Explanation of symbols]

1 substrate, 2 and 94 diffraction grating, 3 and 95 optical guide layer, 4, 41 and 92 multiple quantum well layer (MQ
W) 5 and 96 clad layers, 6 cap layers,
7, 8 and 17 p electrodes, 9 n electrodes, 30, 32,
62 and 63 masks, 31 ridges, 33 current blocking layers, 61 layer thickness control masks, 91 buffer layers, 9
3 barrier layers

Claims (8)

[Claims] 1. A multi-quantum well layer is crystal-grown on a substrate on which a ridge whose ridge width and / or ridge spacing changes along the waveguide direction is preliminarily formed. Therefore, the semiconductor laser or the optical integrated device is characterized in that the composition and / or the layer thickness of the multiple quantum well layer is changed to form a waveguide whose band gap is changed. 2. A semiconductor laser or an optical integrated device according to claim 1, wherein a layer thickness control mask for sandwiching a ridge is provided on the substrate, and the multiple quantum well layer is crystal-grown. 3. A layer thickness of the optical guide layer in the cavity direction by crystal-growing the optical guide layer on a substrate on which a ridge whose ridge width and / or ridge spacing changes along the cavity direction is formed in advance. And / or a composition, a diffraction grating having a constant pitch is formed on the upper surface or the lower surface of the optical guide layer, and the effective pitch of the diffraction grating is changed in the direction of the resonator. device. 4. A diffraction grating having a constant pitch is formed in which a region where the layer thickness and / or composition of the light guide layer gradually changes in the waveguide direction is formed. Semiconductor laser or optical integrated device. 5. A phase adjusting region in which the layer thickness and / or composition of the optical guide layer is different in a part of the waveguide direction, and a diffraction grating having a constant pitch is formed. The semiconductor laser or the optical integrated device described. 6. A ridge width and / or /
Alternatively, a method of manufacturing a semiconductor laser or an optical integrated device, characterized in that a ridge having a variable ridge spacing is formed and a multiple quantum well layer is crystal-grown on the ridge. 7. The method of manufacturing a semiconductor laser or an optical integrated device according to claim 6, wherein a layer thickness control mask sandwiching the ridge is provided to control the layer thickness of the multiple quantum well layer. 8. A ridge width and /
Alternatively, manufacturing of a semiconductor laser or an optical integrated device characterized in that a ridge having a variable ridge spacing is formed, an optical guide layer is crystal-grown on the ridge, and a diffraction grating having a constant pitch is formed in the optical guide layer. Method.