JPH0336506A - Integrated type photodetecting circuit - Google Patents

Abstract

PURPOSE:To demultiplex signal light into a TE-mode and a TM mode light beam without using any external power source and to reduce the size of a device by demultiplexing signal light spatially by a 1st and a 2nd striped optical waveguide in a striped optical demultiplexing area. CONSTITUTION:The striped optical demultiplexing area is provided which is molded integrally so that a clad area on one side of the 1st striped optical waveguide 4 is composed of the core area of the 2nd striped optical waveguide 5 and a clad area on one side of the 2nd striped optical waveguide 5 is composed of the core area of the 1st striped optical waveguide 4. Further, the circuit is provided with an input part 7 which is connected to one end of the optical demultiplexing area and made of the same material with the 1st or 2nd striped optical waveguide 4 or 5, at least one of output parts 8 and 9 connected to the other end of the striped optical demultiplexing area, and photodetectors DT1 and DT2 arranged at the output ends of the output parts 8 and 9. Consequently, the signal light can be demultiplexed into the TE-mode light and TM-mode light in the optical demultiplexing area without using any external power source and they can be detected by the photodetector nearly without coupling loss.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a waveguide type TE used as a key device in the polarization diversity method, which is a method of detection in optical communications, etc. The present invention relates to an integrated photodetection circuit in which a wave splitter and a photodetector, or an optical demultiplexer, a photodetector, and a local light emitting source are integrally formed.

(Prior Art) In coherent optical communication, there is a polarization diversity method as a heterodyne detection method that does not depend on the polarization state of light.

In this method, a signal light is split into two mutually orthogonal polarized waves by an optical demultiplexer, and these two orthogonal polarized waves are separately detected by locally oscillated light whose polarization planes are matched to each other. As devices, an optical demultiplexer, a photodetector, and a local light source are required.

Conventionally, optical demultiplexers that separate linearly polarized light whose polarization planes differ by 90 degrees have used prisms, devices with a structure in which a metal film is loaded on the surface of an optical waveguide, or lithium niobate single crystals. Therefore, devices that have a waveguide structure formed by proton exchange, and directional coupling devices that also use lithium niobate single crystals have been used.

Furthermore, there are almost no examples of integrally forming and integrating an optical demultiplexer, a photodetector, and a local light emitting source, and coupling through spatial propagation, fiber, etc. has been used.

(The problem that the invention attempts to solve?, ¥i) However,
The optical demultiplexer using the above prism has a bulk structure,
Because it is not a waveguide, it has been difficult to use it for optical communications, etc.

Furthermore, according to the device loaded with the above-mentioned metal film, the metal film produces a very large absorption for TM mode propagating light with a polarization plane perpendicular to the substrate surface, while Since it hardly absorbs TE mode propagating light, it acts as a TE mode transmission filter, but it does not act as a TM mode transmission filter, so it is unable to separate TE and 7M mode light. There was a point.

In addition, in the proton exchange waveguide using the above-mentioned lithium niobate single crystal, the proton exchange portion has a high refractive index only for 7M mode light, so it functions as a TM mode transmission filter, but it transmits TE mode light. Since it does not act as a filter, there is a problem in that it is not possible to separate TE and 7M mode light.

In addition, in the above-mentioned directional coupling type device, TM and TE
Mode light can be split, but this splitting method applies an external electric field and uses the electro-optic effect to create TE and 7M waves.
Since the coupling degree for each mode light is controlled independently, there is a problem in that an external power source is required.

Furthermore, when an optical demultiplexer and a photodetector or local light source are coupled together using a fiber without being integrated, there are drawbacks such as loss at the fiber coupling section and an increase in the size of the entire device. there were.

The present invention has been made in view of the above circumstances, and its purpose is to provide a waveguide type optical demultiplexer and an optical demultiplexer capable of spatially demultiplexing TE and 7M mode light without using an external power source. An object of the present invention is to provide an integrated photodetection circuit in which a detector or a local light emitting source is integrated.

(Means for Solving the Problem) In order to achieve the above object, claim (1) provides a first striped optical waveguide on a semiconductor substrate, the core region of which confines light is made of a semiconductor crystal having a superlattice structure. , a second striped optical waveguide whose core region is made of a semiconductor crystal mixed with the superlattice, and a cladding region on one side of the first striped optical waveguide is the second striped optical waveguide. a striped light converging unit formed integrally with a core region of the first striped optical waveguide, and a cladding region on one side of the second striped optical waveguide formed of the core region of the first striped optical waveguide. a demultiplexing region, an input section made of the same material as the first or second striped optical waveguide connected to one end of the striped converging and demultiplexing region, and an input section connected to the other end of the striped converging and demultiplexing region. It included at least one output section made of the same material as the first or second striped optical waveguide, and a photodetector disposed at the output end of the output section.

Further, in claim (2), the absorption region of the photodetector is constituted by a semiconductor crystal having a superlattice structure, and the superlattice in the core region of the first striped optical waveguide is formed in the core region of the second striped optical waveguide. Consisting of a partially mixed superlattice with a lower degree of mixed crystallization than the mixed crystallized superlattice that constitutes the region,
and a mixed crystal superlattice constituting the core region of the second striped optical waveguide, a mixed crystal superlattice constituting the core region of the first striped optical waveguide, and a mixed crystal superlattice constituting the absorption region of the photodetector. The superlattices were constructed so that each band gap had a smaller value in the order listed.

Further, in claim (3), the emission wavelength is the same as the wavelength of the signal light detected by the photodetector, and the polarization plane is parallel to the semiconductor substrate surface or the light is perpendicular to the semiconductor substrate surface. at least one local light emitting source that emits one of the lights having a polarized plane, and the emitted light of the local light emitting source is made to enter the output section so as to be combined with the signal light propagating through the output section. An optical waveguide was provided.

(Function) According to claim (1), the TE mode light (light having a polarization plane parallel to the semiconductor substrate surface) incident on the input section and the 7M
The signal light containing a mixture of mode light (light with a polarization plane perpendicular to the semiconductor substrate surface) is separated into TE mode light and 7M mode light in the first and second striped optical waveguides of the stripe converging and splitting region. It is divided into two waves. Next, the split light is
After being guided to the output section and propagating through the output section, it enters a photodetector, where it is converted into a photocurrent and detected.

Further, according to claim (2), the light propagated through the output section is
incident on the absorption layer of the photodetector. Since the absorption layer has a smaller band gap than other waveguide regions, incident light is absorbed, converted into photocurrent, and detected.

According to claim (3), the signal light split into the TE mode light and the 7M mode light by the first and second striped optical waveguides in the stripe converging and splitting region is directed to the output section. guided.

On the other hand, for example, TE momo oscillation light having the same wavelength as the signal light emitted from the local light source is guided to the optical waveguide and enters the output section. In the output section, the T of this TE momo oscillation light and the signal light guided to the demultiplexing detection power section is
Combined with E mode light. The combined TE mode light is
The signal becomes a so-called beat signal and enters the absorption layer of the photodetector, where it is converted into a photocurrent and detected.

Furthermore, even when the oscillation light from the local light source is 7M mode light, it is detected by the photodetector under the same effect as described above.

(Embodiment) FIGS. 1 and 2 show a first embodiment of an integrated photodetection circuit according to the present invention, and FIG. 1 is a perspective view thereof, and FIG.
Each figure shows a plan view of the optical waveguide portion in FIG. 1, and is an example of a configuration in which an optical demultiplexer and a photodetector are integrated.

In FIG. 1, reference numeral 1 denotes a substrate, which is made of, for example, an n-type GaAs single crystal. 2 is an n-type cladding layer formed over the entire upper surface of the substrate 1;
Al x Ga 1-x A with lower refractive index
s (e.g. x-0,3),
St is 10”/cs’ to make it an n-type semiconductor.
It is mixed at a certain concentration.

3-1.3-2 is an absorption layer made of GaAs and Al y G
It is composed of a superlattice layer with a repeating structure of thin layers of about 80λ of a+-yAs (for example, ymo, a).

Reference numeral 4 denotes a first striped optical waveguide (hereinafter referred to as the first optical waveguide), which is made of a material in which the superlattice layer constituting the absorption layer 3-1.3-2 is partially mixed crystal by a method described later. (hereinafter referred to as the first substance). Note that the term "partial mixed crystallization" as used herein refers to a state in which the degree of mixed crystallization does not reach a complete mixed crystal state but remains at an intermediate stage.

Reference numeral 5 denotes a second striped optical waveguide (hereinafter referred to as the second optical waveguide), which is a partial optical waveguide with a higher degree of mixed crystallization than the mixed crystal superlattice that constitutes the first optical waveguide 4. It is composed of a mixed crystal superlattice (hereinafter referred to as the second substance).

These first and second optical waveguides 4 and 5 are such that the first optical waveguide 4 is a cladding area on one side of the second optical waveguide 5, and the second optical waveguide 5 is a cladding area on one side of the first optical waveguide 4. A stripe light converging/splitting region 6 (hereinafter referred to as the optical demultiplexing region) is formed integrally with the side cladding region and serves as an optical demultiplexer.
It consists of

Reference numeral 7 denotes a signal light input section, which is composed of a striped optical waveguide made of a first material, and is connected to one end of the optical demultiplexing head region 6 (one end of the first and second optical waveguides 4 and 5). There is.

Reference numeral 8 denotes a first output section, which is composed of a striped optical waveguide made of a first material, and its input end is connected to the first optical waveguide 4.
It is connected to the other end, and the absorption layer 3-1 is connected to the output end.

Reference numeral 9 denotes a second output section, which is composed of a striped optical waveguide made of a second material, and its input end is connected to the second optical waveguide 5.
It is connected to the other end, and the absorption layer 3-2 is connected to the output end.

These first and second output sections 8 and 9 form a so-called Y-shaped branch and are spatially separated. Also,
The absorption layer 3 - 1 , 3 - 2 , the optical wavefront region 6 , the input section 7 , and the first and second output sections 8 9 are integrally formed on the upper surface of the cladding layer 2 .

10 is a p-type cladding layer, and A D x Ga 1-A s having the same composition as the n-type cladding layer 2 is placed in the manual section 7 and the optical demultiplexing region 6 (first and second optical waveguides 4° 5
), the first and second output parts 8.9, and the absorption layer 3-1.
3-2, and Be is mixed at a concentration of about 10''/cm3 to make it a p-type semiconductor.

11 is a cap layer, which is made of p-type GaAs and is a cap layer 10
It is constructed by stacking layers on top.

12-1.12-2 is a p-type ohmic electrode (hereinafter referred to as p
The electrode is made of CrAu and has a diameter of 1S.

The p-type electrode 12-1 is formed on the cap layer 11 so as to face the absorption layer 3-1. Similarly, p-type electrode 1
2-2 is a cap layer 1 facing the absorbent layer 3-2.
1.

13 is an n-type ohmic electrode (hereinafter referred to as n-type electrode)
It is made of AuGeNi and is formed in a region facing the p-type electrode 12-1, 12-2 on the lower surface of the substrate 1.

In such a configuration, the first photodetector DT
l is configured. Similarly, the n-type electrode 13, the substrate 1,
Cladding layer 2, absorption layer 3-2, cladding layer 10. A second photodetector D is formed by the cap layer 11 and the p-type electrode 12-2.
T2 is configured.

Next, a method for manufacturing the integrated photodetection circuit having the above configuration will be explained step by step with reference to FIG. 3 for some steps.

First, an n-type cladding layer 2 of 2 μm is continuously formed over the entire surface of a substrate 1 using a crystal method that allows film thickness control at the atomic layer level, such as molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD). The superlattice layer, which will become the absorption layer of the photodetector, is epitaxially grown to a thickness of 1 μm. Then p
2 p m sp type cladding layer 10
/ layer 11 is epitaxially grown to a thickness of 0.2 μm.

The wafer grown in this manner is subjected to the following processing as shown in FIG.

First, the entire surface of the wafer is coated with S by plasma CVD method or the like.
About 2000λ of i02 is deposited. Thereafter, only the 5tO2 above the region that will become the photodetector is removed by photolithography and reactive ion etching. Next, the SiO2-patterned superlattice side of this wafer and another GaAs wafer were stacked together in a hydrogen atmosphere at a heating rate of 30°C/sec, a heat treatment temperature of 950°C, and a heat treatment time of 30 seconds. Heat treatment. By this heat treatment, SiO
□The superlattice at the bottom of the film is mixed and becomes a mixed crystal superlattice. As a result, the first material constituting the input section 7, the optical waveguide 4 of trSl, and the first output section 8 is formed (the third
(See figure (a)).

Next, the 5in2 film is patterned again by photolithography and reactive ion etching so that only the upper portions of the second optical waveguide 5 and the second output section 9 remain.

Furthermore, heat treatment is performed using the same heating time, heat treatment temperature, and heat treatment time as above. Through this process, a second material forming the second optical waveguide 5 and the second output section 9 is formed (see (b) in FIG. 3).

Next, the input section 7, the first optical waveguide 4 and the first output section 8
, the second optical waveguide 5 and the second output section 9 are patterned and coated using a photolithography technique so that the resist remains on them. After that, by ion milling, the cap layer 11 other than the waveguide portion was reduced to 0.2 μm, 1 cladding layer 1
0 by 2 μm and 1 superlattice by 1 μm (Figure 3 (c))
reference).

Next, the resist and SiO2 on the waveguide are removed by acetone and reactive ion etching, respectively. Thereafter, using photolithography technology, only the upper part of the region that will become a photodetector is made of p-type electrode 12-1.12 made of CrAu.
-2 (see FIG. 3(d)). Finally, the n-type electrode 13 made of AuGeNi is deposited on the lower surface of the substrate 1 to complete the fabrication.

FIG. 4 shows a signal light section 7 made of a first substance, a first
The energy band of the optical waveguide 4, the first output part 8, the first optical waveguide 5 made of a second material, the second output part 9, and the absorption layer 3-1, 3-2 made of a superlattice. FIG. 3 is a diagram for explaining gaps.

In FIG. 4, ■ indicates a region made of the second substance, ■ indicates a region made of the first substance, and ■ indicates a region made of a superlattice.

As can be seen from FIG. 4, the energy band gap increases stepwise as the degree of liquid crystallization of the superlattice increases from region (1) to region (2) to region (3). in particular,
The energy band gap Ea of region ■ is 1.69
eV, the energy band gap Eb in region ■ is 1
．． 58 eV, energy band gap E in region ■
c is 1.47 eV.

FIG. 5 is a diagram showing the lateral refractive index distribution in the optical demultiplexing region 6, that is, the first optical waveguide 4 and the second optical waveguide 5. In FIG. 5, the actual ill is the refractive index of TE mode light whose polarization direction is parallel to the first surface of the substrate, and the broken line ■ is the refractive index of 7M mode light whose polarization direction is perpendicular to the first surface of the substrate. A and D are air regions, B is a region of the second optical waveguide 5,
C indicates the area of the first optical waveguide 4, respectively.

Here, the refractive index for each mode light of TE and TM of the optical waveguide 4 of Jliil is Ns (TE) and Ns (TM
), and the refractive indexes of the second optical waveguide 5 for TE and TM mode light are Na (TE) and Na (TM), and the following relationship exists between these refractive indices.

Ns (TE) > Na (TE) > Na
(T M ) > N s (T M ) Difference in refractive index Δn (TE)−N,s (TE
)-Na (TE) and Δn (TM)-Na (TM
)-Ns (TM)) is approximately 4×10−3.

Therefore, in the horizontal refractive index distribution of the optical demultiplexing region 6 in FIG. 5, the peak value of the refractive index is in the region C of the first optical waveguide 4 for the TE mode light J, and It can be seen that the deviation value of the refractive index for the second optical waveguide 5 is in the region B of the second optical waveguide 5.

- In an optical waveguide in which a core portion made of a material with a high refractive index is surrounded by a cladding made of a material with a low refractive index within the film, light has the characteristic of propagating through the core region with a high refractive index, so as shown in Figure 5 above. As is clear from the above, the TE mode light propagates along the first optical waveguide 4, while the 7M mode light propagates along the second optical waveguide 5, and these TE mode light and 7M mode light It will be spatially separated.

Next, the operation of this embodiment will be explained step by step.

The signal light mixed with TE and 7M mode light incident on the human power section 7 is transmitted to the first part of the light distribution area 6 according to the principle of FIG.
After being split into TE mode light and 7M mode light in the second optical waveguides 4 and 5, the light is propagated through the first and second output sections 8 and 9 forming a Y-shaped branch, respectively, and the first and second
The light is incident on each absorption layer 3-1.3-2 of the photodetectors DTl and DT2.

In the absorption layer 3-1 and 3-2, the band gap is smaller than that of other waveguide regions (see Figure 4), so the incident light is absorbed and converted into photocurrent as in a normal detector. transformed and detected.

FIG. 6 is a diagram showing the output characteristics of the first and second photodetectors DTI and DT2. In Figure 6, the horizontal axis is the substrate 1
represents the polarization angle with respect to a plane parallel to
E mode light and 7M mode light coexist at the same intensity.

On the other hand, the vertical axis represents the photocurrent output from the photodetectors DTI and DT2. In addition, the solid line indicates the first line that detects TE mode light.
The broken line shows the output characteristic of the second photodetector DT1 that detects 7M mode light, and the broken line shows the output characteristic of the second photodetector DT2 that detects 7M mode light.

As can be seen from FIG. 6, the output of each photodetector DTl and DT2 changes as the polarization angle of the incident light changes. Also, when only TE mode light or only 7M mode light is input, the output ratio (
The extinction ratio (extinction ratio) is about 20 dB, the TE and TM mode lights are well separated, and the separated lights are detected by the integrated optical injectors DTI and DT2.

As described above, according to this embodiment, TE mode light and 7
Light distribution area 6 using M mode light without using an external power source
The first and second output sections 8.9 can spatially demultiplex the signals, and the demultiplexed signals can be demultiplexed by the integrated first and second photodetectors DTI and DT2. It is possible to realize an integrated photodetection circuit that can detect the output direction without causing coupling loss. Further, as a manufacturing method, a very simple process of loading 5in2 using a semiconductor crystal having a superlattice structure and then performing an annealing treatment can be applied, which has the advantage of being easy to manufacture.

FIG. 7 is a configuration diagram showing a second embodiment of the integrated photodetection circuit according to the present invention, and shows an example of the configuration in which an optical demultiplexer, a photodetector, and a local light source are integrated. Specifically, TE mode optical oscillation and TM mode optical oscillation lasers having the same wavelength as the signal light mixed with TE and 7M mode light input to the input section 7 are integrated, and each laser light is combined with the signal light. By doing so, an integrated device that performs polarization diversity detection is formed.

Note that a distributed reflection laser is used as the laser.

In FIG. 7, 21 is an optical waveguide that guides only TE mode light, and is composed of a core region made of a first material and a cladding region made of a second material. Reference numeral 22 denotes a diffraction grating, which is formed in the core region of the optical waveguide 21 made of the first material. 23 is a gain medium, one end of which is connected to one end of the core region of the optical waveguide 21. A mirror 24 is formed at the other end of the gain medium 23 by etching. These optical waveguides 21
1 diffraction grating 22. The gain medium 23 and the mirror 24 constitute a first local light source 2o that functions as a distributed reflection type TE all-mode oscillation laser.

Reference numeral 25 denotes an optical waveguide for TE mode light, which is made of a first material, one end of which is connected to the other end of the core region of the optical waveguide 21, and the other end connected to the output end of the first output section 8. It is connected. 26 is a coupling region for TE mode light, which is made of a first material, and one end of which is connected to the first output section 8.
and the optical waveguide 25, and the absorption layer 3-1 is connected to the other end of the optical waveguide 25.
The TE mode light demultiplexed by the TE laser oscillation light from the first local light source 20 is combined.

Reference numeral 31 denotes an optical waveguide that guides only 7M mode light, and is composed of a core region made of a second material and a cladding region made of the first material. A diffraction grating 32 is formed in the core region of the optical waveguide 31 made of a second material.

33 is a gain medium, one end of which is connected to one end of the core region of the optical waveguide 31. A mirror 34 is formed at the other end of the gain medium 33 by etching. The optical waveguide 311, the diffraction grating 2-in medium 33, and the mirror 34 constitute a second local light source 30 that functions as a TM mode optical oscillation laser of an opposite distribution type.

Reference numeral 35 denotes an optical waveguide for 7M mode light, which is made of a second material, one end of which is connected to the other end of the core region of the optical waveguide 31, and the other end connected to the output end of the second output section 9. It is connected. 36 is a coupling region for TM mode light, which is made of a second material, and one end of which is connected to the second output section 9.
and the optical waveguide 35, and the absorption layer 3-2 is connected to the other end of the optical waveguide 35.
The 7M mode light demultiplexed by the 7M mode light and the TM laser oscillation light from the second local light source 30 are combined.

The other parts are the same as those in the first embodiment.

Note that the manufacturing method of the second embodiment is different from the manufacturing method of the first embodiment because the first and second local light emitting sources 20.30 are integrated. The details will be explained below (see FIG. 8).

When growing a wafer, the p-type rad layer 1 of the first embodiment is
In the portion corresponding to 0, a non-doped cladding layer 10a into which no p-type impurity is introduced is grown. In FIG. 7, partial mixed crystal formation using SiO2 is performed twice to create a waveguide section excluding the photodetector section (formation region of the photodetector) and the gain medium section, and a diffraction grating section (formation region of the diffraction grating). ) After the superlattice of (see FIG. 8(a)) is mixed crystal, the photodetecting section and the gain medium section are fabricated by the process shown in FIG. 8(b) and (c).

After removing 5in2 used for partial mixed crystal formation by reactive ion etching (RIE) or the like, 5i02 is newly deposited on the surface of the portion other than the gain medium section and the photodetector section. Next, this wafer was placed with ZnAs2 at 51
02 sealed in an ampoule and heated at a heat treatment temperature of 575°C.
Heat treat for 4 hours.

As a result, as shown in FIG. 8(b), Zn is diffused in the region not covered with 5i02. The Zn diffusion front exists in the middle of the superlattice layer that constitutes the gain medium section and the photodetector section. Mixed crystal formation occurs in the region where Zn is diffused within the superlattice layer. Further, the region where Zn is diffused becomes a p-type head region with a carrier concentration of about 4×10I97c115.

As a result, the mixed crystal region in the active layer becomes a cladding layer, and accordingly, the thickness of the active layer in the gain medium section becomes thinner, and the laser oscillation threshold can be lowered. Furthermore, since the active layer and the waveguide portion are connected without regrowth, the coupling loss between the two is reduced.

Next, a diffraction grating is manufactured by a method for manufacturing a diffraction grating in a normal distributed reflection laser (see (c) in FIG. 8). At that time, the periods At, A of the diffraction gratings 22 and 32 in the first local light emitting source 20 (TE MOMO oscillation laser) and the second local light emitting source 30 (TM MOMO oscillation laser)
2 is formed to have the same wavelength as the signal light S.

Incidentally, these periods AI and A2 are expressed as Ne f f (T
E), Ne f f (TM), and the signal light S
When the wavelength of is λB, Al-λB/2Ne f f (TE)A2-'AB/
2Ne f f (T, M).

Finally, electrodes (not shown in FIG. 7) are formed on the local light emitting source section and the photodetecting section to complete the manufacturing process.

Next, the operation of the second embodiment will be explained in order.

The signal light S incident on the input section 7 is demultiplexed into TE mode light and 7M mode light by the first and second optical waveguides 4 and 5 of the optical demultiplexing region 6 according to the principle shown in FIG. It is then guided to first and second outputs 8 and 9 forming a Y-shaped branch.

On the other hand, the TE laser beam having the same wavelength as the signal light emitted from the first local light emitting IWf 20 and the TM laser light having the same wavelength as the signal light emitted from the second local light emitting source 30 are connected to the optical waveguide. 25 and 35 respectively, and in coupling regions 26 and 36 the first and second outputs 8
TE mode light and 7M guided by 9 and 9, respectively.
They are combined with the mode light respectively. The combined TE mode light and 7M mode light are transmitted to the first and second photodetectors DT1. The light is detected by each absorption layer 3-1.3-2 of DT2.

In this way, polarization diversity type detection is realized.

As described above, in the second embodiment, in addition to the configuration of the first embodiment, the first and second local light sources 20, 30
By further connecting and integrating the detector, it is possible to significantly reduce the overall size of the detector, making it possible to realize a compact polarization diversity type integrated detector with low coupling loss.

In each of the above embodiments, a 5in2 film was used to create a superlattice mixed crystal, but it can also be achieved by depositing St, N, Ill and annealing.

(Effect of the invention) As explained above, according to claim (1), TE mode light and 7M mode light can be spatially demultiplexed in the optical demultiplexing head region without using an external power source. It is advantageous to provide an integrated photodetection circuit that can detect the demultiplexed output by a photodetector via the output section without causing any coupling loss. Furthermore, the overall size of the device has the advantage of being smaller than conventional devices due to integration. Further, as a manufacturing method, a very simple process of loading 5i02 and then annealing can be applied using a semiconductor crystal having a superlattice structure, so there is an advantage that manufacturing is easy.

Further, according to claim (2), the photodetector can be integrally formed with the human power section, the sufficient wave region, and the output section, and in addition to the effect of claim (1), there is no coupling loss. It has the advantage that it is possible to realize highly accurate photodetection, to reduce the size of the layer, and to be easy to manufacture.

Further, according to claim (3), since the optical demultiplexing head area as an optical demultiplexer, the photodetector, and the local light source that oscillates TE mode light (7M mode light) are integrated, coupling loss is small.
This has the advantage of realizing a compact integrated optical detector using the polarization diversity method.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of the integrated photodetection circuit according to the present invention, FIG. 2 is a plan view of the optical waveguide portion in FIG. 1, and FIG. 3 is the integrated photodetection circuit in FIG. 1. An explanatory diagram of the circuit fabrication method, Fig. 4 shows the energy band in Fig. 1.
An explanatory diagram of the gap, FIG. 5 is a diagram showing the lateral refractive index distribution in the optical splitting front region according to the present invention, FIG. 6 is an output characteristic diagram of the photodetector according to the present invention, and FIG. 7 is a diagram showing the present invention. FIG. 8 is an explanatory diagram of a method of manufacturing the integrated photodetection circuit of FIG. 7. 1... N-type substrate, 2... N-type cladding layer, 3-
1.3-2... Absorption layer, 4... First striped optical waveguide, 5... Second striped optical waveguide, 6.
...Stripe emission splitting area, 7...Human power department, 8...
・First output section, 9...Second output section, 1o...p
Cladding layer of mold, 11... Cap layer, 12-1.1
2-2...p-type obic electrode (p-type electrode), 13
...N-type obic electrode (n-type electrode), DTl...
・First photodetector, DT2...Second photodetector, 2o
...first local light emitting source, 21...optical waveguide that guides only TE mode light, 22.32...diffraction grating, 23
゜33...Gain medium, 24.34...Mirror 2
5... Optical waveguide for TE mode light, 26... Coupling region for TE mode light, 30... Second local light source, 31.
...Optical waveguide that guides only 7M mode light, 35...
Optical waveguide for TM mode light, 36...Coupling region for TM mode light. EZ22Z! 117) wI [=: ko Second substance Diagram i02 Diagram Explanatory diagram of the energy lid gear and p of each part in FIG. Fig. 6 Gain medium section □□□Grating section 1 Wavepath section

Claims (3)

[Claims] (1) A first stripe-shaped optical waveguide on a semiconductor substrate, the core region of which confines light is made of a semiconductor crystal with a superlattice structure, and the second stripe whose core region is made of a semiconductor crystal mixed with the superlattice. a shaped optical waveguide, the first
A cladding region on one side of the striped optical waveguide is constituted by the core region of the second striped optical waveguide, and a cladding region on one side of the second striped optical waveguide is constituted by the core region of the second striped optical waveguide. A striped sufficient wave region formed integrally with the core region of the striped optical waveguide, and the same material as the first or second striped optical waveguide connected to one end of the striped optical demultiplexing region. an input section connected to the other end of the striped optical demultiplexing region;
Alternatively, an integrated photodetection circuit comprising at least one output section made of the same material as the second striped optical waveguide, and a photodetector disposed at the output end of the output section. (2) The absorption region of the photodetector is constituted by a semiconductor crystal having a superlattice structure, and the superlattice of the core region of the first striped optical waveguide constitutes the core region of the second striped optical waveguide. composed of a partially mixed superlattice whose degree of mixing is lower than that of a mixed crystal superlattice, and
A mixed crystal superlattice constituting the core region of the second striped optical waveguide, a mixed crystal superlattice constituting the core region of the first striped optical waveguide, and an absorption region of the photodetector. 2. The integrated photodetection circuit according to claim 1, wherein the bandgaps of the constituent superlattices have smaller values in the order listed. (3) Light whose emission wavelength is the same as the wavelength of the signal light detected by the photodetector and whose polarization plane is parallel to the semiconductor substrate surface or whose polarization plane is perpendicular to the semiconductor substrate surface. At least one local light emitting source that emits one of the lights, and an optical waveguide that makes the emitted light of the local light emitting source enter the output section so as to combine with the signal light propagating through the output section. An integrated photodetection circuit according to claim (1) or claim (2).