JP3391952B2 - Integrated optical semiconductor device in which waveguide filter devices are formed in parallel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type filter device such as a filter for eliminating polarization dependency, which is a problem in optical frequency multiplex communication , formed in parallel.
The present invention relates to a stacked optical semiconductor device .

[0002]

2. Description of the Related Art In recent years, it has been desired to increase transmission capacity in the field of optical communication, and optical frequency division multiplexing (optical FDM) communication in which a plurality of optical frequencies are multiplexed in one optical fiber is developed. Has been. The technique of optical frequency multiplexing (also called wavelength multiplexing, which is used because the wavelength spacing between channels is much smaller) can be roughly classified into two according to the receiving method. Coherent optical communication that takes a beat with a local light source to obtain an intermediate frequency and detects a signal,
This is a method in which only a light of a desired wavelength (frequency) is transmitted and detected by a wavelength tunable filter.

The present invention relates to the latter optical communication system using a wavelength tunable filter. Variable wavelength filters include Mach-Zehnder type, Fiber Fabry-Perot type, A
There are O (acousto-optic) modulator type, semiconductor type, etc., which are under development.

The Mach-Zehnder type and the fiber Fabry-Perot type can be designed so that their transmission bandwidths can be relatively freely set, and those having a narrow bandwidth of several Å can be obtained, so that there is an advantage that the frequency multiplicity can be increased. Further, it is also a great advantage that it is not affected by the polarization of the signal light. Examples of the Mach-Zehnder type include OCS 89-65, K.K. O
da et al. There is “channel selection characteristic of optical FDM filter”, and as an example of the fiber Fabry-Perot type, I. P. Kaminow et al. "FDM
A-FSK Star Network with a
Tunable Optical Filter D
emulplexer "IEEE J. Lig
http://technol.org/. vol. 6, N
o. 9, p. 1406, September, 19
There are 88 etc. However, these types have problems such as loss of light, difficulty in integration with a semiconductor photodetector, and difficulty in downsizing of the device.

In the case of the AO modulator type, since the transmission bandwidth is large and is about several tens of liters, control is easy, but the number of wavelength division multiplexing cannot be increased. Illustratively, OCS 91-
83N. Shimosaka et al. There is a "wavelength division / time division composite multiplex optical network in a broadcasting station using an acousto-optic filter". This type has drawbacks such as loss of light, non-integration, and polarization control of input light.

As a semiconductor type, for example, a DFB (distributed feedback type) filter having a diffraction grating in an optical guide layer can have a narrow transmission band width of about 0.5 Å.
Since it also has a light amplification function (about 20 dB),
This has the advantage that the frequency multiplicity can be increased and the minimum receiving sensitivity can be reduced.

As a known example thereof, OQE 88-65
T. Numai et al. There is a "semiconductor variable wavelength filter" (1988). This has the advantage that it can be integrated and the optical receiver used in an optical communication system can be miniaturized because it can be made of the same material as the semiconductor photodetector and the like. As described above, the semiconductor DFB type is the optical F
An optical filter or optical receiver having characteristics suitable for DM communication. However, in general, it has a polarization dependency that it is affected by the polarization of the signal light.

Further, in Japanese Patent Application Laid-Open No. 6-120906, in order to eliminate the polarization dependence, an optical filter configured so that the tuning wavelength of TE mode and the tuning wavelength of TM mode are the same. There has been proposed an optical receiver or an optical semiconductor device in which a receiver is provided with a pair and a branch path for distributing signal light to these two filters.

This is based on either of the following two methods. 1) A structure in which the effective refractive index n ^TE _eff of the TE mode in one optical filter is equal to the effective refractive index n ^TM _eff of the TM mode in the other optical filter n ^TE _eff = n ^TM _eff 2) A structure in which the ratio of the effective refractive index of the TE mode in the optical filter to the effective refractive index of the TM mode of the other optical filter is equal to the ratio of the reciprocals of the pitches Λ ₁ and Λ ₂ of the respective distributed feedback diffraction gratings n ^TE _eff : n ^TM _eff = 1 / Λ ₁ : 1 / Λ ₂ . As means for realizing the above method, in the method 1), in order to control the effective refractive index, the width of the waveguide is changed, the thickness of the constituent layer of the waveguide is changed, and the composition of the constituent layer of the waveguide is changed. Means such as are presented. Also,
In the method 2), a means of changing the pitch of the grating with two filters is presented.

[0010]

However, the following points are pointed out in the above-mentioned conventional example (JP-A-6-120906). In the control of the effective refractive index as the first method, it is necessary to control the waveguide width with high precision in order to control the effective refractive index by changing the width of the waveguide.
A relatively complicated process is required, or multiple crystal growths are required to change the composition or thickness of the constituent layers of the waveguide, which makes the growth and process for making integrated devices relatively complicated. There is a point.

In addition, as the second method, in order to change the grating pitch with two filters, it is necessary to finely adjust the alignment of interference exposure, and the photolithography process becomes relatively complicated.

Therefore, an object of the present invention is to reduce the polarization plane dependence of the device with respect to the polarization mode of incident light in an integrated optical semiconductor device of an integrated waveguide type optical filter device formed on the same substrate. To provide the device.

[0013]

[0014]

[0015]

[0016]

[0017]

To achieve the above object SUMMARY OF THE INVENTION, the invention according to this application, on a single substrate, the waveguide type optical device is a plurality of fractional possible waveguide filter device in parallel a formed integrated optical semiconductor device, the waveguide filter of at least two devices rather parallel stacking direction of the waveguide to one another, the input of the waveguide type filter device
A branching device that splits light into each filter device is formed on the shooting end side.
The light from each filter device is detected on the output end side.
It is characterized in that a photodetector is formed.
In addition, a plurality of discriminable waveguide type fibers can be mounted on one substrate.
The optical waveguide device, which is an optical device, was formed in parallel.
An integrated optical semiconductor device, the waveguide type filter device
At least two of the waveguides should not be parallel to each other.
The waveguide type filter device is a vertical directional coupler filter.
It is characterized by being In addition, a single substrate
Waveguide-type light that is a waveguide-type filter device capable of discriminating the number
It is an integrated optical semiconductor device in which devices are formed in parallel.
And at least two of the waveguide type filter devices are waveguides.
The stacking directions of the
The unit is a DFB filter .

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

In the above structure, Si which is an amphoteric impurity
In the III-V group compound semiconductor layer doped with, a p-type layer and an n-type layer are obtained depending on the plane orientation of the substrate. In particular, since it becomes a p-type layer on the normal mesa surface and an n-type layer on the flat surface, this is used as a hole injection path. With this configuration, it is possible to form the current confinement structure by one continuous crystal growth. In the above structure, when Se, which is an n-type dopant, and Zn, which is a p-type dopant, are simultaneously supplied, a p-type layer is formed especially on the mesa surface and an n-type layer is formed on the flat surface. Is the injection route. This technique is known from Japanese Patent Application Laid-Open No. 5-63304. With this configuration, similarly, it is possible to form the current confinement structure with one crystal growth. Further, in the above structure, the flat portion is made to have a high resistance by implanting a front surface, and the slope portion is used as an electron or hole injection path. Inactivation by injection of pront is described in J. C. Dyment et al. Pr
oc. For details, see IEEE, 60, 726 (1972). With this structure, it is possible to increase the number of times of crystal growth for forming the current constriction structure to once.
Further, in the above structure, the use of the GaAs substrate contributes to the realization of a low threshold semiconductor laser.
The use of the {00} substrate and the appearance of the Ga stabilization surface as the forward mesa surface means that amphoteric impurities are utilized or p-type and n-type impurities are simultaneously supplied to confine the current by a single growth. Facilitates the realization of the structure. In the above configuration,
The use of the {111} A plane suppresses the generation of new facet planes in the subsequent growth process because this plane is a low index plane. In addition, in the above configuration, the fact that the forward mesa plane forming the waveguide is two different {001} planes makes the directions of the TE modes in two different semiconductor lasers or the like orthogonal to each other, and thus in an integrated DFB filter device or the like. Reduces polarization plane dependence.

[0025]

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment A first embodiment according to the present invention will be described with reference to FIG. FIG. 1A is a perspective view of the integrated optical filter device.
In the figure, 101 is an n-GaAs (001) substrate having a step portion 100 formed along the [1-10] direction, and a {111} A plane appears on the slope of the step portion 100. Three-electrode DFB filters 102 and 103 are formed on the inclined surface of the step portion 100. Further, 104 is a branching device including a ridge type waveguide section (shown by 104a) and a branching section (shown by 104b) integrated on the same substrate, and 105 and 106 are photo integrated on the same substrate. It is a detector (PD).

The currents passed through the three-electrode DFB filters 102 and 103 are short-circuited at both ends 102a and 102c;
I _FS flowing to 03a and 103c and the center part 1 independently of this
02b; flow to 103b are two of I _FC, by controlling the ratio of these currents, while maintaining the amplification factor and the transmission bandwidth constant can change the transmission wavelength. This characteristic is shown in Figure 2.
Is shown in. Both filters 102 and 103 have the same characteristics with the inclined surface on which they are formed as the TE mode electric field amplitude direction. The diffraction gratings of the DFB filters 102 and 103 are second-order.

As shown in FIG. 1B, the DFB filters 102 and 103 have a layer structure of Sn-doped n-Al _0.6 Ga _0.4 As lower cladding layer 110 having a thickness of 1.5 μm.
0.1 μm thick Sn-doped n-Al _0.3 Ga _0.7 As lower optical confinement layer 111, _0.3 μm thick GaAs active layer 112, 0.1 μm Be-doped p-Al _0.3 Ga
_0.7 As upper optical confinement layer 113, 0.2 μm thick Be
Doped p-Al _0.5 Ga _0.5 As carrier confinement layer 11
4, 0.5 μm thick Si-doped Al _0.3 Ga _0.7 As optical guide layer 115, 1.4 μm Be-doped Al _0.6 Ga _0.4
As upper cladding layer 116, _0.3 μm thick Si-doped Al _0.3 Ga _0.7 As current confinement layer 117, _0.3 μm B
The e-doped GaAs contact layer 118. Depth 0.
The 2 μm diffraction grating 108 is formed on the light guide layer 115. Ohmic electrodes 121, 12 on the upper and lower surfaces
2 is formed.

The above structure is produced by double growth by the MBE method. First, the step portion 100 is masked and the substrate 1 is etched. This allows the mask to
The forward mesa surface as shown in (a) is formed. After that, the optical guide layer 115 is laminated by the MBE method, and the portion other than the inclined surface of the step portion 100 is masked to form the diffraction grating 108 here by the photolithography method. The diffraction gratings 108 on both sides may be formed at once by interference exposure from directly above the substrate, or the diffraction gratings 108 on both sides may be formed separately in two steps by interference exposure from directly above each inclined surface. May be. Next, the contact layer 118 is grown for the second time by the MBE method, and finally the ohmic electrodes 121 and 122 are formed.

Photodetector (PD) 105, 106
Is also formed with the DFB filters 102, 103. However, no diffraction grating is formed on the PDs 105 and 106, and a reverse voltage is applied to the electrodes. The branching device 104 is formed on the substrate 101 in a process different from the above process. The layer structure is basically the same as that of FIG. 1B, but a composition having a large band gap is used so that light absorption does not occur, and it is laminated in parallel with the surface of the substrate 101 to form the inclined surface. The DFB filters 102 and 103 are in contact with each other at an angle with the laminated portion. The splitter may be formed entirely separately and finally combined with the DFB filters 102, 103. Further, it may be configured by a two-branch optical fiber or the like.

Regarding a semiconductor laser in which amphoteric impurities are used for growth by the MBE method used in this embodiment and an active region is on a slope due to current constriction, US Pat. No. 4,785,457 by Peter M. Asbeck et al. As disclosed in the specification.

The current constriction structure will be described below in accordance with this embodiment. Si-doped optical guide layer 115, current confinement layer 1
The conductivity type of 17 takes both pn depending on the plane orientation of the base substrate 101. That is, Si which is an amphoteric impurity
The layer doped with is n− on the (001) plane of the flat part.
It becomes AlGaAs, and p− on the {111} A plane of the slope.
It becomes AlGaAs. Since the Be-doped layer becomes a p-type layer regardless of the crystal orientation, most of the holes injected into the active layer 112 through the three-layer structure of the optical guide layer 115, the upper cladding layer 116, and the current constriction layer 117 are Light guide layer 11
5. In the current confinement layer 117, it passes on the {111} A plane (in other places, holes are blocked by the pnp structure),
It is injected into the active layer 112 portion on the {111} A plane. Most of the holes, which have a lower mobility than electrons, are on the sloped active layer 11.
Since it is injected into the laser beam 2, laser oscillation light occurs here, and an optical output is obtained.

In the DFB filter device of the present embodiment, the current is confined in the active layer 112 on the inclined surface by the current confinement structure, thereby providing the gain waveguide type lateral confinement. In the DFB filters 102 and 103, current is injected and tuned with a bias below the threshold value,
It is used as a filter device.

The DFB filters 102 and 103 are stacked on the (-1-11) and (111) planes, respectively, and the stacking direction forms an angle of about 70 degrees. That is, D
The TE mode electric field amplitude directions of the FB filters 102 and 103 (directions along the slope) form an angle of about 70 degrees. The signal light guided through the ridge type waveguide section 104a is branched by the branching section 104b, one of which is made incident on the DFB filter 102 and the other is made incident on the DFB filter 103. For example, when light having a transmission wavelength in the TE mode of the DFB filter is incident (see FIG. 2), the DFB filter 10
TE mode light for 2 (the direction of the electric field amplitude is DFB
About 80% of TM mode light to the DFB filter 102 (the direction of the electric field amplitude is perpendicular to the slope of the DFB filter 102) is transmitted by the DFB filter 102. ,
Since it is coupled to the TE mode of the DFB filter 103, this is transmitted. The light after passing through both filters is PD105, 10
By taking the sum of the outputs after the OE conversion, which is received in 6, it is possible to suppress the fluctuation of the output even if the polarization plane of the input signal light changes. In an ideal state where the branching device 104 has no polarization plane dependency and distributes the incident light at a ratio of 50% -50%, the sum of the outputs from the PDs 105 and 106 caused by the variation of the polarization plane of the input light. Of about 3 dB.

Second Embodiment A second embodiment according to the present invention will be described with reference to FIG. FIG. 3B is a perspective view of the integrated optical filter device. Reference numeral 201 shown in FIG. 3A is an n-GaAa (001) substrate in which a step portion 200 is formed along the [1-10] direction, and a {111} A plane appears on the slope. The DFB filter 20 having three electrodes is provided on the inclined surface of the step portion 200.
2 and 203 are formed in the same manner as in the first embodiment, but different from the first embodiment is that the portion between the two filters 202 and 203 is not a ridge but a groove is formed. That is what is being done. In addition, reference numeral 204 denotes a branching device, 20
Reference numerals 5 and 206 are integrated PDs. Switch 204
Has a buried structure in which the high resistance layer 210 is buried around. The layer structure of each part, the effect of suppressing the output fluctuation with respect to the fluctuation of the polarization plane of the incident light, and the like are the same as those in the first embodiment.

The above structure is produced by double growth by the MBE method. First, the substrate 201 is etched by masking other than the step portion 200. After that, the optical guide layer 115 is laminated by the MBE method, and the diffraction grating 108 is formed here by the photolithography method by masking other than the inclined surface of the step portion 200. Next, 2 up to the contact layer 118 by MBE method
After the second growth, finally ohmic electrodes 121, 1
22 is formed. As for the branching device 204, a laminated structure is separately formed, the periphery of the branching device 204 is etched, and the low refractive index portion 210 is embedded therein.

In the first and second embodiments, the MBE method is given as an example of the crystal growth method, but the MOVPE method and the GS method are used.
Even a vapor phase crystal growth method such as MBE method, MOMBE method, CBE method or the like can be used for manufacturing a similar device as long as it exhibits the plane orientation dependence of the incorporation of the dopant.

Third Embodiment A third embodiment according to the present invention will be described with reference to FIG. FIG. 4A is a perspective view of the integrated optical filter device. Thirty
1 is n in which the step portion 300 is formed along the [100] direction.
It is a GaAs (011) substrate, and the (001) plane and the (010) plane are exposed on the slope of the step portion 300. On the slope of the step portion 300, the DFB filter 30 with three electrodes is provided.
2, 303 are formed.

By controlling the ratio of the current I _FS flowing through the both ends of the three-electrode DFB filters 302 and 303 and the current I _FC flowing through the center independently of this, the amplification factor and the transmission bandwidth are kept constant. It is the same as the first embodiment that the transmission wavelength can be changed while maintaining the above.

The diffraction grating 304 of the DFB filters 301 and 303 is of the second order. This DFB filter 301, 30
3 has a layer structure of Si-doped n-Al _{0.6 with a} thickness of 1.5 μm.
Ga _0.4 As lower clad layer 305, 0.1 μm thick S
i-doped n-Al _0.3 Ga _0.7 As lower optical confinement layer 30
6, 0.3 μm thick GaAs active layer 307, 0.1 μm
Thick Be-doped p-Al _0.3 Ga _0.7 As upper optical confinement layer 308, 0.2 μm thick Be-doped p-Al _0.5 Ga
_0.5 As carrier confinement layer 309, _0.5 μm thick B
e-doped Al _0.3 Ga _0.7 As optical guide layer 310, 1.4
A Be-doped Al _0.6 Ga _0.4 As upper cladding layer 311 having a thickness of μm and a Be-doped GaAs contact layer 312 having a thickness of 0.3 μm. The diffraction grating 304 having a depth of 0.2 μm is formed on the carrier confinement layer 309. Ohmic electrodes 320 and 321 are formed on the upper and lower surfaces.

The above structure is produced by double growth by the MBE method. The resistance of the flat portion is increased by the implantation of protons to form a current constriction structure. Also in the present embodiment, the gain waveguide type lateral confinement is adopted.

The DFB filters 302 and 303 are laminated on the (001) plane and the (010) plane, respectively, and the laminating direction forms an angle of 90 degrees. That is, DFB
The TE mode electric field amplitude directions of the filters 302 and 303 form an angle of 90 degrees. The signal light is split by a beam splitter (not shown), and one of them is split by the DFB filter 30.
2, the other is incident on the DFB filter 303. D
When light with a transmission wavelength in the TE mode of the FB filter is incident, the TE mode light with respect to the DFB filter 302 is D
The FB filter 302 transmits the light, and the DFB filter 302
The TM mode light with respect to is coupled to the TE mode of the DFB filter 303 and is transmitted therethrough. The PD (not shown) receives the light after passing through both filters, and by taking the sum of the obtained outputs after OE conversion, it is possible to suppress the output fluctuation even if the polarization plane of the input signal light changes. Become.

Fourth Embodiment A fourth embodiment according to the present invention will be described with reference to FIG. FIG. 5A is a perspective view of the integrated optical filter device. Four
01 is an n-GaAs (001) substrate in which the step portion 400 is formed along the [1-10] direction.
The {111} A plane is exposed on the slope. The vertical directional coupler filters (VDF) 402 and 403 are provided on the inclined surface of the step portion 400 of the step portion 400 and the photodiode 4
04 and 405 are integrated with each other. Also, 40
Reference numeral 6 is an integrated branching device.

The structure and manufacturing method of this device are shown below. On the n-GaAs (001) substrate 401 on which the step portion 400 is formed, Sn-doped n-GaAs having a thickness of 0.5 μm is formed.
Buffer layer 410, 1.5 μm thick Sn-doped n-Al
_0.6 Ga _0.4 As clad layer 411, 0.1 μm thick Sn
Doped n-Al _0.6 Ga _0.4 As / GaAs MQW (multiple quantum well) lower waveguide layer 412, 0.3 μm thick Sn
A doped n-Al _0.6 Ga _0.4 As clad layer 413 is laminated, and a diffraction grating 430 is formed therein. No diffraction grating is formed in the photodetector portions 404 and 405.

An n-light guide layer 414, an n-Al _0.3 Ga _0.7 As / GaAs MQW upper waveguide layer 415, an undoped absorption layer 416, a p-clad layer 417, and a p-contact layer 418 are formed on the clad layer 413. It is stacked in the second growth (FIG. 5C). This laminated structure is for the photodiodes 404 and 405, and the electrodes 42
The reverse voltage is applied to 1, 422, and the light guided through the upper waveguide layer 415 is absorbed by the absorption layer 416.

In the forward couplers 402 and 403, etching is performed up to the upper waveguide layer 415 to remove the absorption layer 416, and the p-cladding layer 419 and the p-contact layer 420 are selectively grown for the third time. Stack with (Fig. 5
(B)). The waveguide is a refractive index waveguide due to a difference in refractive index generated because the width of the well in the quantum well layer portion is larger on the slope than on the flat portion. Next, the p-side electrodes 421, n
The mold electrode 422 is formed, and the p-side electrode 421, the n-side electrode 422, and the contact layer 4 are formed between the forward coupler portion and the photodetector portion.
Remove 18,420. Now, the forward coupler unit 40
2, 403 are formed.

In this configuration, the forward coupler section 40
Light is incident on the lower waveguide layers 412 of the optical waveguides 2 and 403, and only light of a part of the wavelength is coupled to the upper waveguide layer 415 and propagated, and can be received by the photodetectors 404 and 405. The TM light propagates through the lower waveguide 412 as it is and is emitted to the outside. The forward couplers 402 and 403 can change the center wavelength of filtering by applying an electric field.

Also in this embodiment, the two filters 40 are used.
Since the reference numerals 2 and 403 are formed on the inclined surfaces inclined with respect to each other, the electric field amplitude direction of the TE mode in each of the filters 402 and 403 forms an angle of about 70 degrees. That is, when the signal light is split by the beam splitter 406 and one of them is incident on the VDF 402 and the other is incident on the VDF 403, the light incident on the first VDF 402 in the TE mode is filtered by the VDF 402, and the first VDF 402 is filtered.
About 80% of the light that enters the 402 in the TM mode is the second
It is possible to perform filtering with the VDF 403. By taking the sum of the outputs after the OE conversion obtained by the photodetectors 404 and 405, it is possible to suppress the fluctuation of the output even if the polarization plane of the input signal light changes.

To this end, the tuning wavelength is set to each filter 40.
It suffices to tune to the same wavelength as the wavelength in the TE mode at 2, 403, and the tuning operation of the device is significantly easier than that conventionally proposed. That is, if the crystal growth on the two inclined surfaces and the uniformity of the process are high, the electrodes for applying the electric field to VDF 402 and VDF 403 may be common. This also applies to the above embodiment. Further, the beam splitter 406 is formed similarly to the branching part of the first embodiment.

Fifth Embodiment A fifth embodiment according to the present invention will be described with reference to FIG. FIG. 6A is a perspective view of the integrated semiconductor optical amplifier. 5
Reference numeral 01 is an n-GaAs (001) substrate in which a step portion 500 is formed along the [1-10] direction, and a {1
11} Side A appears. Semiconductor optical amplifiers 502 and 503 are formed on the inclined surface of the step portion 500. The layer structure of the semiconductor optical amplifiers 502 and 503 is as follows: Sn-doped n-Al _0.6 Ga _0.4 As lower clad layer 5 having a thickness of 1.5 μm.
10, 0.1 μm thick Sn-doped n-Al _0.3 Ga _0.7 A
s lower confinement layer 511, 0.1 μm thick undoped n
-Al _0.3 Ga _0.7 As / GaAs MQW active layer 51
2, 0.1 μm thick Be-doped p-Al _0.3 Ga _0.7 As
Upper optical confinement layer 513, 0.2 μm thick Si-doped A
l _0.6 Ga _0.4 As carrier confinement layer 514, 1.0 μ
m-thick Be-doped p-Al _0.6 Ga _0.4 As upper cladding layer 515, 0.2 μm-thick Si-doped Al _0.6 Ga _0.4 A
An s carrier confinement layer 516 and a 0.3 μm Be-doped p-GaAs contact layer 517. Ohmic electrodes 521 and 522 are formed on the upper and lower surfaces.

The above structure is manufactured by the GSMBE method. It may be formed by another method described above. The characteristics of the two optical amplifiers 502 and 503 formed on the slope are almost the same as those of the above-described embodiment. Optical amplifiers 502, 5
A ridge type branching device 504 is provided in the front stage of 03, and a confluencer 505 is provided in the rear stage. These have the same configuration and are formed similarly to the branching portion of the first embodiment. The semiconductor optical amplifiers 502 and 503 using the quantum well layer as the active layer 512 have a polarization plane dependence of gain, and polarization control is required for independent use. In the present embodiment, the electric field amplitude direction of the TE mode light of the first optical amplifier 502 or 503 that amplifies half of the light split by the branching device 504 and the second optical amplifier that amplifies the other half of the light. TE of 503 or 502
Since the electric field amplitude direction of the mode light forms an angle of about 70 degrees, the polarization plane dependency is greatly improved as compared with the case of being configured by a single optical amplifier. Two optical amplifiers 502, 5
The lights amplified in 03 are merged again in the merger 505.

Also in this embodiment, the current confinement structure (Si-doped carrier confinement layer 51) using the amphoteric impurity Si is used.
4, a Be-doped upper clad layer 515, a Si-doped carrier confinement layer 516, etc.) has been described, but a current confinement structure by proton implantation (see the third embodiment), p-type and n-type impurities are used. It may be a current confinement structure including layers supplied simultaneously (see the sixth embodiment below).

Sixth Embodiment As a sixth embodiment of the present invention, an optical amplifier including a current confinement structure with layers grown by simultaneously supplying n-type and p-type dopants will be described.

In FIG. 7A, AlGaInP based semiconductor optical amplifiers 602 and 6 formed on an n-GaAs substrate 601.
03 is shown. Reference numeral 604 is a branching device, and 605 is a joining device.
These are formed similarly to the fifth embodiment. Board 601
Uses an n-GaAs (001) substrate and forms the step portion 600 by photolithography and wet etching. The resonator direction is the [1-10] direction, and the {112} A plane is exposed as a slope. 612 in FIG.
Is n-AlGaInP lower clad layer, 616 is AlGa
The InP current confinement layer 617 is a p-GaAs contact layer.

Se-doped n-A by the well-known MOCVD method
lGaInP lower cladding layer 612, undoped GaIn
The P active layer 613 is laminated. As it is, Zn
While simultaneously supplying Se and Se, the AlGaInP current confinement layer 614 is laminated. N-AlGaInP is formed in the flat portion growing on the (001) plane, and p-AlGaInP is formed in the slope portion growing on the {112} A plane. Furthermore S
The supply of e is stopped, the flow rate of Zn is increased, and p-AlGa
An InP upper clad layer 615 is formed, and an AlGaInP current confinement layer 616 is laminated while supplying Zn and Se again at the same time. Further, while supplying only Zn, p-GaA
The s contact layer 617 is formed. Electrodes are formed and electrodes are separated therefrom, and a ridge type branching device 604 and a confluence device 60 are formed.
Accumulate with 5.

In the present embodiment, the layer thickness on the inclined surface is thicker than the layer thickness at the flat portion, and the refractive index guiding for light is performed as in the fourth embodiment.

In the above embodiments, the filter device and the optical amplifier device are taken as an example, but in an optical semiconductor device in which a plurality of separable waveguide type optical devices need to be formed in parallel on one substrate. The present invention can be applied to any one as long as it is present. Further, the above embodiment is merely an example of a method of manufacturing a waveguide in which the stacking directions of the waveguides of the waveguide type optical device are not parallel to each other.

[0057]

As described above, according to the invention of the present application, for example, the equally-divided input light is incident on the waveguide type optical filter device whose TE modes are not parallel to each other. Thus, the polarization plane dependence of the filter with respect to the polarization mode of the incident light can be reduced .

[0058]

[0059]

[0060]

[Brief description of drawings]

FIG. 1 (a) is a perspective view showing an integrated optical filter according to a first embodiment of the present invention, and FIG. 1 (b) is a cross-sectional view of two filters.

FIG. 2 shows the characteristics of the DFB filter shown in FIG. 1 (FIG. 1A shows the relationship between the injection current ratio and the transmission center wavelength (TE mode).
(B) is a diagram showing a transmission center wavelength (TE mode), a gain, and a transmission width when an injection current ratio is 0.23.

FIG. 3 (a) shows GaAs (00
1) A substrate is shown, and FIG. 3B is a perspective view showing an integrated optical filter according to a second embodiment of the present invention.

FIG. 4 (a) is a perspective view showing an integrated optical filter according to a third embodiment of the present invention, and FIG. 4 (b) is a sectional view of this filter.

5A is a perspective view of an integrated optical filter according to a fourth embodiment of the present invention, and FIG. 5B is a cross-sectional view of a vertical directional coupler portion. 5C is a sectional view of the PD portion.

FIG. 6 (a) is a perspective view of an integrated optical amplifier according to a fifth embodiment of the present invention, and FIG. 6 (b) is a sectional view of this optical amplifier.

7A is a perspective view of an integrated optical amplifier according to a sixth embodiment of the present invention, and FIG. 7B is a sectional view of the optical amplifier.

[Explanation of symbols]

100, 200, 300, 400, 500, 600
Step portion 101, 201, 401, 501, 601 n-Ga
As (001) substrates 102, 103, 202, 203, 302, 303
3-electrode DFB filter 104, 204, 406, 504, 604 Divider 105, 106, 205, 206, 404, 405
PD 108, 304, 430 Diffraction grating 112, 307, 512 Active layer 115, 514 Si-doped optical guide layer 117, 516 Si-doped current confinement layer 210 Low refractive index portion 301 n-GaAs (011) substrate 402, 403 Vertical direction Coupler filter 412 Lower waveguide layer 415 Upper waveguide layer 416 Absorption layer 502, 503, 602, 603 Semiconductor optical amplifier 505, 605 Combiner 614, 616 Current constriction layer

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Claims (3)

(57) [Claims] 1. An integrated optical semiconductor device in which a plurality of discriminable waveguide type optical devices, which are waveguide type optical filter devices, are formed in parallel on one substrate. At least two of the waveguides are not laminated in parallel with each other, a branching device for branching light to each filter device is formed on the incident end side of the waveguide type filter device, and a branching device for branching light from each filter device is formed on the exit end side. Integrated photo-semiconductor device characterized in that a photodetector for detecting the light is formed. 2. An integrated optical semiconductor device in which a plurality of discriminable waveguide type optical devices, which are waveguide type optical filter devices, are formed in parallel on one substrate. An integrated optical semiconductor device in which at least two of the waveguides are not parallel to each other in lamination direction and the waveguide type filter device is a vertical directional coupler filter. 3. An integrated-type optical semiconductor device in which a plurality of discriminable waveguide type filter devices, which are waveguide type optical devices, are formed in parallel on one substrate. An integrated optical semiconductor device in which at least two waveguide layers are not parallel to each other and the waveguide type filter device is a DFB filter.