JPH11223739A - Integrated optical circuit element and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture plural optical element parts such as a semiconductor laser or an optical waveguide in the same crystal growth process, and to prevent any layer interrupting optical connection from being present among the optical element parts. SOLUTION: An integrated optical circuit element is provided with a first optical element part (semiconductor laser part) 10 including first and second element areas 310 and 320 layered in a layer thickness direction, second optical element part (optical waveguide part) 30 formed at a position separated from the first optical element part 10, and multi-mode interfering area 20 having an embedded part 114 formed in the propagating direction of a light positioned between the first optical element part 10 and the second optical element 30. In this case, the first optical element part 10 is optically connected through the multi-mode interfering area 20 with the second optical element part 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated optical circuit device and a method of manufacturing the same, and more particularly to an optical coupling method between a plurality of optical circuit devices. More specifically, the present invention relates to an integrated optical circuit element in which a semiconductor laser section and an optical waveguide section having different near fields are integrated, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in manufacturing an integrated optical circuit device in which a semiconductor laser device (also referred to as a "semiconductor laser portion") having different near fields and an optical waveguide device (also referred to as an "optical waveguide portion") are integrated. In general, a hybrid method in which a semiconductor laser device and an optical waveguide device are separately manufactured and then combined with each other is generally used. However, in practice, since the positioning accuracy is severe, it is difficult to use the hybrid system industrially.

To solve this difficulty, there has been proposed a method of integrally integrating a semiconductor laser device and an optical waveguide device on the same substrate.

For example, Japanese Patent Application Laid-Open No. 63-182882 discloses that an active layer 2 and a cladding layer 3 are deposited on an InP substrate 1 and then the active layer 2 and the cladding layer 3 are schematically shown in FIG. There is disclosed a structure in which a part of the layer 3 is removed by etching, and a buffer layer 5, an optical waveguide layer 6, and a protective layer 7 are deposited on the removed portion to form an optical waveguide portion. Further, an electrode 8 is formed on the remaining portion of the active layer 2 and the cladding layer 3, and functions as a semiconductor laser unit.

On the other hand, IEEE PHOTONICS T
In ECHNOLOGY LETTERS, Vol. 2, No. 2, page 88 (February 1990), the light distribution between the semiconductor laser section 13 and the optical waveguide section 11 is stepwise, as schematically shown in FIG. The tapered portion 12 that changes to
A configuration in which the semiconductor laser unit 13 and the optical waveguide unit 11 are integrated integrally has been proposed.

[0006]

However, in the configuration of FIG. 14, in the region 9 between the active layer 2 and the optical waveguide layer 6,
There is no structure that traps light in the vertical direction. For this reason, radiation of light that does not go to the optical waveguide layer 6 is generated in this region 9, and the coupling efficiency to the optical waveguide layer 6 is degraded.

Further, in order to form the active layer 2 and the optical waveguide layer 6 by separate growth processes, the heights of the active layer 2 and the optical waveguide layer 6 are made to be within the controllability of the crystal growth technique. It is difficult. For example, when the optical waveguide layer 6 is formed by using the usual metal organic chemical vapor deposition (MOCVD) technique, the formation position in the layer thickness and the height direction is generally shifted from the set value by about 5 to 10%. Generally, it is desirable that the optical waveguide layer is formed so that its thickness is about several μm in consideration of connection with an external element (for example, an optical fiber).
At this time, the thickness of the buffer layer provided below the optical waveguide layer is generally several μm. In such a case, a displacement of about 0.1 to 0.5 μm occurs in the height direction, and the thickness of the region 9 between the active layer 2 and the optical waveguide layer 6 reaches several μm. The coupling loss due to causes other than the mode mismatch is about 1 dB. In particular, in the case of an optical element having a small light distribution width such as a semiconductor laser, the above-described positional shift and light emission in a region having no light confinement structure are significantly generated.

On the other hand, in the example shown in FIG. 15, since the semiconductor laser section 13 and the optical waveguide section 11 are connected by the tapered section 12 having a gradually changing light distribution, the light emission between them is small. Highly efficient optical coupling is expected. However, in order to form the tapered portion 12, it is necessary to perform a plurality of (three or more in the illustrated configuration) etching and regrowth processes, which complicates the manufacturing process and reduces the taper accompanying the regrowth process. It is difficult to obtain the expected operating characteristics due to the deterioration of the crystal quality of the portion 12 and the optical waveguide portion 11. For this reason, no examples have been reported in which the configuration of FIG. 15 has been practically used in industry up to the present.

[0009] In the structure of FIG.
Since the optical waveguide layer and the active layer of the semiconductor laser section 13 are formed of the same material, a waveguide loss due to free carrier loss occurs in the optical waveguide section 11 and the optical waveguide section 1
No good characteristics can be expected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has the following objects. (1) A plurality of optical element sections such as a semiconductor laser and an optical waveguide are manufactured by the same crystal growth process, and Providing an integrated optical circuit element having a configuration in which there is no layer between the element sections that prevents optical coupling therebetween, and (2) providing a method of manufacturing such an integrated optical circuit element. It is.

[0011]

According to the present invention, there is provided an integrated optical circuit device comprising: a first optical device portion including first and second device regions stacked in a layer thickness direction; A second optical element portion formed at a position distant from the portion, and an embedded portion formed between the first optical element portion and the second optical element portion and formed in the light propagation direction. A multi-mode interference region having the first optical element section and the second optical element section optically coupled to each other via the multi-mode interference area. Is achieved.

In the buried portion of the multimode interference region, the light emitted from the first optical element moves in parallel while maintaining the light distribution shape at the time of emission from the first optical element. The length may be set to reach the second optical element.

The width of the buried portion of the multimode interference region in the direction perpendicular to the light propagation direction may change continuously or stepwise.

[0014] A thin boundary layer may be formed between the first optical element section and the multi-mode interference region.

According to another integrated optical circuit device of the present invention, there are provided first and second integrated optical circuit devices having different light distribution widths stacked in a layer thickness direction.
And a first optical element portion including a second element region and an in-plane direction formed in a propagation direction of light emitted from the first optical element portion and perpendicular to the layer thickness direction and the layer thickness direction. A multimode interference region having a buried portion having a multimode waveguide structure in each of the first and second optical devices formed at a position separated from the first optical device portion via the multimode interference region And the light emitted from the first optical element portion propagates through the multi-mode interference region to the second optical element portion, so that the first optical element portion and the The second optical element part is optically coupled, thereby achieving the above-described object.

In the configuration of the integrated optical circuit device described above,
The second optical element section may have a mesa structure that is aligned with the first optical element section and the buried section of the multimode interference region.

Further, the buried portion of the multi-mode interference region may be formed by stacking two or more sub-regions.

The method for manufacturing an integrated optical circuit device according to the present invention comprises:
At the same time, a first optical element unit having first and second element regions stacked in the layer thickness direction and a second optical element unit arranged at a position distant from the first optical element unit Forming, a first etching step of etching an area between the first optical element portion and the second optical element portion to form an etching groove, and multi-mode interference in the etching groove. Embedding the region to form a buried portion, thereby achieving the aforementioned object.

In one embodiment, in the first etching step, the entirety of the formation portion of the multi-mode interference region is etched to form the etching groove, and the embedding step includes: A step of forming a first buried layer by embedding with a constituent material of the buried portion of the mode interference region, and removing a predetermined portion of the first buried layer by etching to correspond to the buried portion of the multimode interference region. A second etching step for leaving a portion to be formed, and a thin film or a second film for covering a side portion of the buried portion of the remaining multimode interference region.
Forming a buried layer.

In one embodiment, in the first etching step, a mesa structure for lateral confinement in the second optical element portion is simultaneously formed.

According to another method of manufacturing an integrated optical circuit device of the present invention, a multi-mode interference region having a buried portion is formed, and a predetermined region around the multi-mode interference region is etched to form at least two regions. Forming one removal region at a position sandwiching the buried portion of the multi-mode interference region; and first and second element regions stacked in one of the at least two removal regions in a layer thickness direction. Simultaneously forming the first optical element portion and the second optical element portion on the other side, thereby achieving the above object.

In one embodiment, an etching step for forming the multi-mode interference region and an etching step for forming a mesa structure for lateral confinement in the second optical element portion are simultaneously performed. I do.

In the above manufacturing method, the formation hole of the upper electrode of the first optical element portion and the ridge of the second optical element portion may be formed simultaneously by the same etching process.

In the integrated optical circuit device of the present invention having the above-described features, an optical waveguide layer and an active layer of a semiconductor laser portion are sequentially laminated on a semiconductor substrate, and then a part of the active layer is etched. It is removed to a level below the optical waveguide layer and the active layer. Next, the buried portion of the multi-mode interference region is buried in the removed region as a layer having a refractive index that becomes a multi-mode waveguide in the vertical direction. This buried portion is a narrowly defined multi-mode interference region.

The multimode interference region (more precisely, the buried portion) acts to guide the light emitted from the semiconductor laser portion to the optical waveguide portion distant from the semiconductor laser portion, whereby the high efficiency coupling is achieved. An integrated optical circuit device is obtained. Further, since the semiconductor laser section and the optical waveguide layer of the optical waveguide section are separated in the vertical direction (layer thickness direction), the optical waveguide section can be manufactured non-doped, and an optical waveguide section with less light absorption can be obtained. realizable.

By optimizing the length of the multimode interference zone,
The coupling efficiency between optical elements having different light distribution widths in the layer thickness direction can be further improved.

When a semiconductor laser element (semiconductor laser section) and an optical waveguide element (optical waveguide section) are used as the optical element section, the effect of the present invention is more remarkable since the light distribution widths are largely different between them. can get.

Furthermore, if the multi-mode interference region is formed in multiple stages using the optical buffer layer, further high-efficiency coupling is realized.

If the width of the buried portion of the multimode interference region is changed continuously or stepwise, optical coupling between optical elements having different light distribution widths in the lateral direction can be performed more efficiently. Further, by reducing the rate of change of the light distribution width in the horizontal direction in a narrower region, a greater effect can be obtained.

Furthermore, if a multi-mode interference region functioning as a multi-mode waveguide is provided in both the layer thickness direction and the lateral direction, it is possible to obtain an optical coupling efficiency that is not affected by the manufacturing accuracy of the multi-mode interference region. If the bidirectional multi-mode interference regions are formed in multiple stages using optical buffer layers, high efficiency can be achieved without being affected by fabrication accuracy.

When a semiconductor laser device (semiconductor laser portion) is used as the optical device portion, an insulating layer is provided between the semiconductor laser device (semiconductor laser portion) and the multimode interference region in order to prevent current injection into the multimode interference region. By providing
An integrated optical circuit device that achieves a low threshold operation can be obtained.

Further, in the present invention, since all the optical element portions are manufactured by the same process, the positioning between the optical elements can be easily performed, the height does not shift, and the coupling efficiency is reduced. Does not deteriorate in accordance with

In the fabrication of the integrated optical circuit device of the present invention, the formation of the lower electrode of the semiconductor laser portion and the formation of the ridge of the optical waveguide portion can be performed by the same process, and the manufacturing process is simplified. . Also, the embedding of the mesa side for lateral light confinement and the embedding of the multi-mode interference region in the optical waveguide can be performed by the same process, which also simplifies the manufacturing process.

If the multi-mode interference region is formed by the step of embedding in the trench instead of embedding the hole, the multi-mode interference region having high flatness is obtained, and the characteristics are improved.

More preferably, a layer forming a multi-mode interference region is laminated on a flat substrate, and a part of the layer is left to function as a multi-mode interference region while the remaining portion is removed by etching. Thereafter, when a plurality of optical elements are formed, a multimode interference region having substantially flat upper and lower surfaces is formed.

The constituent material of the multimode interference region (eg, Ga
In AlAs), if the mixed crystal ratio of aluminum is 0.3 or less, good selective embedding can be achieved without causing precipitation of aluminum on the mask,
It can function well as a multimode interference region.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of an integrated optical circuit device according to the present invention will be described in detail with reference to FIG. Specifically, the integrated optical conversion device of the present embodiment is a mode conversion laser device that includes an AlGaAs semiconductor laser device and converts the emission mode. In the following, first, a manufacturing method will be described, and then its function will be described.

Specifically, first, an n-type GaAs substrate 10
An optical waveguide is formed on 0 using a normal MOCVD method
N-type Al_0.22Ga_0.78As first light guide layer 1
01, 2 μm thick n-type Al_0.20Ga_0.80As optical waveguide layer
102, n-type Al_0.22Ga_{0. 78}As second light guide layer 10
3, n-type Al_0.8Ga_0.2As etching stop layer 104,
And n-type Al_0.22Ga_0.78As third light guide layer 105
Are sequentially laminated. Thereby, the semiconductor laser unit 10
An optical waveguide is formed in both the optical waveguide section 30 and the optical waveguide section 30.

Further thereon, a light emitting section of the semiconductor laser device
To form n-type Al_0.7Ga_{0 .3}As 1st clad
Layer 107, i-type GaAs active layer 10 having a thickness of 0.1 μm
8, p-type Al_0.7Ga_0.3As second cladding layer 109, p
Type GaAs etching stop layer 110 and p-type third
The pad layers 111 are sequentially stacked. As a result, the semiconductor laser
A first element mainly having an optical waveguide function is provided in the
Region 310 and a second element region mainly having a light emitting action
Region 320 is included in a state of being stacked in the layer thickness direction.
And

Although the thickness of each layer can be changed in the element design, the configuration of this embodiment is different from the first embodiment in that the center of the optical waveguide layer 102 is at a distance of 1.45 μm from the upper surface of the GaAs substrate 100, Layer 108 is GaAs substrate 1
It is designed to be located at a distance of 3.55 μm from the upper surface of the 00.

Next, a method of manufacturing the multimode interference region 20, specifically, the buried portion 114 will be described.
The buried portion 114 of the multi-mode interference region 20 is a narrowly-defined multi-mode interference region.
A multi-mode waveguide 114 having a width of 2 μm and a length of 670 μm is formed between the waveguide and the optical waveguide unit 30.

First, the layers 101 to 111 formed by the above-described process are formed in regions other than the region where the buried portion 114 is formed.
An SiO ₂ film (not shown) is patterned on the surface of the multilayer structure including Next, in a portion where the SiO ₂ film is not formed, vertical etching with a depth of 5 μm is performed using reactive ion beam etching (RIBE). This vertical etching is performed by controlling the etching time so that n-type Ga
The process is performed until the As substrate 100 is reached. More preferably, the remaining film thickness is monitored during the etching.

Thereafter, a second MOCVD growth is performed to form a buried portion 114 of AlGaAs in the multi-mode interference region 20. At this time, as shown in FIG. 2, a portion having a thickness of 0.25 μm at the lowermost portion of the buried portion 114 and a portion having a thickness of 0.25 μm at the uppermost portion are formed of Al _0.20 G
a _0.80 As layers 21 and 23 are buried respectively, and the remaining portion having a thickness of 4.5 μm is Al _0.195 Ga _0.805 As layer 22.
Embed with Thereby, the buried portion 114 functions as a single-mode waveguide having a width of 2 μm in the horizontal direction and as a multi-mode waveguide having a thickness of 4.5 μm in the vertical direction. Further, if the mixed crystal ratio of aluminum in the material for embedding the embedding portion 114 is set to 0.3 or less, the precipitation of crystals on the SiO ₂ mask hardly occurs.

The buried portion 114 thus prepared has its center line in the height direction positioned almost at the center between the active layer 108 and the optical waveguide layer 102.

Next, the subsequent manufacturing process of the semiconductor laser unit 10 and the optical waveguide unit 30 will be described.

First, the previously formed SiO ₂ mask is removed using buffered hydrofluoric acid, and then a new Si ₂ O ₃ mask is used to selectively etch only the optical waveguide section 30.
An O ₂ mask (not shown) is patterned. Using this mask, in the optical waveguide section 30, the first cladding layer 107 is etched flatly in the middle of the first cladding layer 107 with a sulfuric acid-based etchant, and then etched right above the third light guide layer 105 with a hydrofluoric acid-based etchant. Next, a ridge 131 having a width of 2 μm is formed in the extension direction of the semiconductor laser unit 10 and the multi-mode interference region 20 by etching with an ammonia-based etchant using an appropriate mask pattern. This etching automatically stops at the etching stop layer 104. Further, the semiconductor laser unit 1
In order to form a ridge 111 having a width of 2 μm at 0, etching is performed with a hydrofluoric acid-based etchant using a new mask pattern, and etching is performed up to the etching stop layer 110. Through these series of etching processes, the ridge 111 of the semiconductor laser unit 10 and the ridge 131 of the optical waveguide unit 30 are formed in a straight line. The ridge 131 in this case is constituted by the third light guide layer 105.

Finally, the ridge 11 of the semiconductor laser unit 10
An upper electrode 112 and a lower electrode 113 are formed on the upper surface of the substrate 1 and the back surface of the substrate 100, respectively.

A method of designing the buried portion 114 of the multimode interference region 20 formed as described above will be described below.

For the sake of simplicity, considering only the TE mode of the laser light, the laser oscillation wavelength λ, the thickness W and the refractive index n _{r of} the buried portion 114, and the refractive indices n and _{For c} , the length L of the embedded portion 114 is given by the following equation 1,

[0050]

(Equation 1)

Is represented by

At this time, the active layer 1 of the semiconductor laser unit 10
08 and the optical waveguide layer 102 of the optical waveguide unit 30 are installed such that the center line of the gap between them coincides with the center line of the buried portion 114 in the height direction from the surface of the substrate 100. The distance T between the active layer 108 and the optical waveguide layer 102 is expressed by the following equation (2).

[0053]

(Equation 2)

Is designed to be represented by

With such a structure, the multimode interference region 20 (more precisely, the buried portion 114 thereof)
Light travels in parallel from the semiconductor laser unit 10 to the optical waveguide unit 30 as described below.

In the configuration of the present embodiment described above, current is injected between the electrodes 112 and 113, so that the semiconductor laser unit 10 causes laser oscillation. The oscillation wavelength at this time is about 850 nm. Light emitted from the active layer 108 of the semiconductor laser unit 10 enters the multimode interference region 20. At the time of propagation in the multimode interference region 20,
Although the transverse mode substantially maintains the light distribution at the time of incidence, since the multimode interference region 20 (more precisely, the buried portion 114) has a multimode waveguide structure in the vertical direction, the multimode interference region 20 has a multimode waveguide structure in the vertical direction. Mode.

FIG. 2 schematically shows the light distribution in the AA ′ section of FIG. In FIG. 2, the same components as those in FIG. 1 are indicated by the same reference numerals, and a description thereof will be omitted.

The distribution of light in the vertical direction emitted from the semiconductor laser unit 10 is about 0.9 μm in the entire width. In the multimode interference region 20, the incident light is given as the sum of the eigenmodes of the multimode waveguide. However, since a difference occurs in the propagation speed of each eigenmode, a multimode interference region having a certain distance is formed. In other words, splitting or parallel movement of incident light occurs according to the distance. In the integrated optical coupling device according to the present embodiment, the length L of the multimode interference region 20 is set to about 6
By forming the light emitting layer to have a thickness of 70 μm, the light distribution when the light emitted from the active layer 108 enters the multimode interference region is maintained up to the optical waveguide layer 102. Therefore, in the configuration of the present embodiment, the light distribution of the light emitted from the semiconductor laser unit 10 enters the optical waveguide layer 102 of the optical waveguide unit 30 as it is. In the optical waveguide section 30, the ridge 131 formed thereon provides the optical waveguide section 30 with a refractive index distribution, which makes the optical waveguide characteristics advantageous.

The light distribution in the optical waveguide section 30 has a total width of 2.8 μm, and there is a radiation loss due to mode mismatch. The optical waveguide section 30 is carrier-doped and absorbs light. However, if the length of the optical waveguide section 30 is made sufficiently short, it can be suppressed to an acceptable level.

As described above, in the present embodiment, by forming the optical waveguide layer 102 of the optical waveguide section 30 and the optical waveguide layer 102 of the semiconductor laser section 10 by the same crystal growth process, both optical waveguide layers are formed. A good mode conversion laser element free from loss due to misalignment between them can be obtained. Further, by forming the buried portion 114 of the multi-mode interference region 20 from AlGaAs having an aluminum mixed crystal ratio of 0.3 or less, no crystal is deposited on the mask,
Good device fabrication is realized.

It is to be noted that the semiconductor material is not limited to the above-mentioned AlGaAs-based material, but other semiconductor materials can be used.

(Second Embodiment) A second embodiment of the integrated optical circuit device of the present invention will be described in detail with reference to FIG. Specifically, the integrated optical conversion device of the present embodiment is a mode conversion laser device, and has a configuration suitable for integration of an optical circuit device that realizes optical coupling with low loss.

In FIG. 3, the same components as those in FIG. 1 are indicated by the same reference numerals.

First, the manufacturing method will be described.
As in the embodiment, the GaAs substrate 100 is usually
In order to form an optical waveguide by using the MOCVD method of
l_{0. twenty two}Ga_0.78As first light guide layer 101, thickness 2 μm
Al_0.20Ga_0.80As optical waveguide layer 102, Al_0.22Ga
_0.78As second light guide layer 103, Al_0.8Ga_0.2Ase
Etching stop layer 104 and Al_0.22Ga_0.78As 3rd
The light guide layers 105 are sequentially stacked. These layers are
It is formed as an doped layer. This allows semiconductor lasers
Optical waveguides are formed on both the optical waveguide 10 and the optical waveguide 30.
Is done.

Next, after the n-type GaAs electrode layer 106 is formed, the n-type Al _0.7 Ga _0.3 As first cladding layer 10 is formed thereon to form the light emitting portion of the semiconductor laser device.
7. i-type GaAs active layer 108 having a thickness of 0.1 μm, p-type Al _0.7 Ga _0.3 As second cladding layer 109, p-type GaAs
s etching stop layer 110 and p-type third cladding layer 1
11 are sequentially laminated. As a result, the semiconductor laser unit 10
The first element region 31 mainly having an optical waveguide action
0 and the second element region 320 mainly having a light emitting action
Are included in a state of being stacked in the layer thickness direction.

Next, the multi-mode interference region 20 is formed by the same manufacturing method as in the first embodiment (the description is omitted here). However, in the present embodiment, the length of the multi-mode interference region 20 is set to 658 μm.

Next, a description will be given of a manufacturing process of the semiconductor laser unit 10 and the optical waveguide unit 30 which is performed subsequently.
A new SiO ₂ mask (not shown) is patterned, and using this mask, the optical waveguide section 30 is etched to a point in the first cladding layer 107 with a sulfuric acid-based etchant, and then etched with a hydrofluoric acid-based etchant. I do. This etching automatically stops at the n-type GaAs electrode formation layer 106. At this time, by using an appropriate mask pattern, in addition to etching the optical waveguide section 30, the lower electrode 113 of the semiconductor laser section 10 can be used.
The etching hole is formed at the same time at the formation position of.

Thereafter, the ridge 111 of the semiconductor laser section 10 and the ridge 131 of the optical waveguide section 30 are formed by the same process as in the first embodiment. Ridge 1 in this case
Reference numeral 31 includes an electrode forming layer 106 and a third light guide layer 105. Finally, an upper electrode 112 and a lower electrode 113 are formed on the upper surface of the ridge 111 of the semiconductor laser unit 10 and the hole formed by the previous etching process.

The function of the integrated optical circuit device of this embodiment is as follows.
This will be described below.

In this device, the refractive index, dimensions, and the like of the semiconductor laser section 10 and the optical waveguide section 30 are the same as in the first embodiment. In the configuration of this embodiment, current can be injected from the electrode formation layer 106, so that laser oscillation can be performed with a reduced current loss. Light emitted from the semiconductor laser unit 10 enters the multi-mode interference region 20 and is emitted from the optical waveguide unit 30.
Leads to.

The multimode interference region 20 is 670 μm from the interface with the semiconductor laser unit 10 as in the first embodiment.
At the position, the same light distribution as that at the laser emission end face is reproduced, but in this embodiment, the length (L = 658 μm) of the multimode interference region 20 does not match the above value.
This point will be further described with reference to FIGS. FIG. 4A shows the device configuration of the above-described first embodiment, and FIG. 4B shows the device configuration of the present embodiment. However, the reference numbers of the individual layers are omitted.

In the configuration of the first embodiment shown in FIG. 4A, the length of the multimode interference region 20 is changed by the interface between the multimode interference region 20 and the optical waveguide unit 30.
And the length at which the same light distribution as that of the emission end face of the active layer 108 can be obtained. On the other hand, in the configuration of the present embodiment shown in FIG. 4B, instead of setting such a length, the coupling efficiency between the multimode interference region 20 and the optical waveguide unit 30 is maximized. The length is set to be as follows. As a result, as shown in FIG.
The vertical width of the light distribution at the interface between the optical waveguide portion 30 and
The width of the light distribution in the optical waveguide layer 102 of the optical waveguide unit 30 is made equal to the vertical width. As a result, the radiation mode can be reduced due to the mode mismatch.

The inventors of the present invention have manufactured several devices in which the length L of the multi-mode interference region 20 is variously changed to obtain a coupling efficiency between the multi-mode interference region 20 and the optical waveguide 30. Was measured. FIG. 5 shows the measurement results. Accordingly, in order to obtain a coupling efficiency of 0.60 or more, the length L of the multimode interference region 20 has an optimum value in a range of about 651 to 663 μm. This is a method that is effective only when the width of light distribution in the vertical direction differs between the semiconductor laser unit 10 and the optical waveguide unit 30, and is a unique effect unique to the present invention.

Further, in the device of the present embodiment, light absorption in the optical waveguide portion 30 can be eliminated by making the optical waveguide portion 30 non-doped.

By providing the electrode forming layer 106, the distance from the electrode 113 to the active layer 108 is shortened, and the current loss can be reduced. Although the electrode forming layer 106 extends to the upper surface of the ridge 131 of the optical waveguide section 30, the light propagating through the optical waveguide layer 102 does not spread to the electrode forming layer 106, and thus does not cause a large loss. .

As described above, in the integrated optical circuit device of this embodiment, the length of the multimode interference region 20 is adjusted in consideration of the relationship between the actual light distribution and the eigenmode of the optical waveguide layer 102. By doing so, good optical coupling in which the radiation mode is suppressed is realized. Further, by making the optical waveguide portion 30 non-doped, light absorption in the optical waveguide portion 30 can be eliminated, and the length can be increased. This makes it possible to manufacture a Y-branch optical circuit or the like in the optical waveguide section 30.

(Third Embodiment) A third embodiment of the integrated optical circuit device of the present invention will be described in detail with reference to FIG. Specifically, the integrated light conversion device of the present embodiment is a mode conversion laser device, and in addition to the vertical light distribution conversion in the first and second embodiments, the light distribution conversion in the horizontal direction. Is also realized.

In FIG. 6, the same components as those in FIG. 3 are denoted by the same reference numerals, and a detailed description thereof will be omitted here. The manufacturing process of the device of the present embodiment is as follows.
This is basically the same as the process in the second embodiment.

In the configuration of the present embodiment, the multimode interference region 20 has a depth of 4.75 μm and a length of 200 μm, the width of the buried portion 114 is 2 μm at the end face near the semiconductor laser portion 10, and the optical waveguide portion 30 0.5μm at end face close to
, And continuously changed between them.

As shown in FIG. 6, a thin boundary layer 116 is formed at the boundary between the semiconductor laser section 10 and the multimode interference region 20 in a direction perpendicular to the traveling direction of the oscillation laser light. The formation of the thin boundary layer 116 is performed simultaneously by the etching and the burying process for forming the buried portion 114 of the multimode interference region 20.

Specifically, in this etching, the n-type
One light guide layer 101 is left with a thickness of 0.25 μm.
To do. Then, by the second MOCVD process,
Embedded portion of thin boundary layer 116 and multimode interference region 20
114 and i-type Al _0.15Ga_0.85Embed with As
No. In the first and second embodiments, the multimode interference region 2
Thickness of the lowermost and uppermost portions of the buried portion 114 of 0.2
5 μm part is Al_{0. 20}Ga_0.80Embedded in As
However, in the present embodiment, as described above,_0.15Ga_0.85A
The whole is uniformly embedded with s.

The width of the ridge 131 of the optical waveguide section 30 is 2 μm in the first and second embodiments, but is set to 4 μm in this embodiment. The thickness of the third light guide layer 105 is set to be a single mode waveguide with a width of 4 μm. In the case of the present embodiment, since the buried portion 114 of the multimode interference region 20 has an asymmetric confinement structure, the length L of the buried portion 114, the active layer 108 and the optical waveguide layer 1
The interval T with 02 is not represented by the above-described equations 1 and 2.
The applicants of the present application have studied the optimum structure by computer simulation or the like based on Expressions 1 and 2, and confirmed the effectiveness of the device by actually manufacturing the device.

The function of the integrated optical circuit device of this embodiment will be described.

The light emitted from the semiconductor laser unit 10 enters the multi-mode interference region 20. Multimode interference region 20
In the figure, the light guide layer 101 having an aluminum mixed crystal ratio of 0.20 is formed only on the lower side, and the upper side is in direct contact with air without forming a special layer. Therefore, a multi-mode waveguide structure in which the refractive index distribution in the vertical direction is asymmetric is obtained. If the length of the multi-mode interference region 20 is optimally designed, the light distribution moves in the vertical direction in the same manner as in the first and second embodiments, and the light emitted from the semiconductor laser unit 10 is transmitted to the optical waveguide unit. The light is guided to 30 optical waveguide layers 102. On the other hand, the light distribution in the horizontal direction depends on the buried portion 1 of the multimode interference region 20.
As the width of the portion 14 continuously narrows, the light is buried in the embedded portion 1.
At the end of the multimode interference region 20, the entire width of the light distribution expands to 5.5 μm, and coincides with the lateral light distribution in the optical waveguide unit 30.

Although the thin boundary layer 116 is formed sufficiently thin, it does not contribute to the spread of light in the lateral direction, but the current injected from the electrode 112 causes the end of the buried portion 114 of the multimode interference region 20 From the part, the active layer 108 and the first
And a function as an electrically insulating layer for preventing leakage from the semiconductor laser unit 10 via the second cladding layers 107 and 109. The thinner the boundary layer 116 is, the better the thickness is so long as it does not affect the spread of light and can block current. Typically, it is set to 0.1 to 10 μm, preferably 5 μm or less, more preferably 2 μm or less.
μm or less.

In the device of this embodiment, light coupling in the horizontal direction can be realized with high efficiency only by changing the mask pattern. In the above description, the width of the buried portion 114 of the multimode interference region 20 is changed so as to be continuously reduced in the traveling direction of the laser light. However, the same effect can be obtained by changing the width stepwise. Can be Further, the change may be linear or curved. In addition, the multimode interference region 20
The same effect as described above can be obtained by increasing the thickness of the embedded portion 114 continuously or stepwise in the direction of travel of the laser beam.

Further, by forming the i-type thin boundary layer 116 between the semiconductor laser section 10 and the multi-mode interference region 20, efficient current injection is realized, and the laser oscillation threshold is lowered. Is done.

(Fourth Embodiment) A fourth embodiment of the integrated optical circuit device of the present invention will be described in detail with reference to FIG.

In FIG. 7, the same components as those in FIG. 3 are denoted by the same reference numerals, and a detailed description thereof will be omitted here. The manufacturing process of the device of the present embodiment is as follows.
This is basically the same as the process in the second embodiment. However, in the configuration of the present embodiment, the multimode interference region 2
The width of the embedded portion 114 of 0 is formed as large as 15 μm. Also, the center line of the ridge 111 of the semiconductor laser unit 10 and the center line of the ridge 131 of the optical waveguide unit 30 are provided with a shift of 6.3 μm in the width direction, and the center of the buried portion 114 of the multimode interference region 20 in the lateral direction is provided. It is designed to be located symmetrically with respect to.

The function of the integrated optical circuit device of this embodiment will be described.

In the first to third embodiments, since the width of the buried portion 114 of the multimode interference region 20 is as narrow as 0.5 to 2 μm, as shown schematically in FIG. On the surface, a concave or convex shape may occur at the boundary between the buried portion 114 and the non-buried portion, and the surface may not be flat. In such a case, the distribution of the eigenmode in the buried portion 114 of the multi-mode interference region 20 slightly changes, and the coupling efficiency deteriorates. On the other hand, in the configuration of the present embodiment, by providing the buried portion 114 extending in the vertical and horizontal directions, a region where light is effectively distributed is buried flat.

FIG. 9 shows the multimode interference region 20 (more precisely, the embedded portion 114) in the configuration of the present embodiment.
Is shown from the top.

Immediately after the light exits from the semiconductor laser unit 10 or immediately before the light enters the optical waveguide unit 30, the boundary region between the semiconductor laser unit 10 and the multimode interference region 20.
And a non-flat buried region 31 existing in a boundary region between the multimode interference region 20 and the optical waveguide portion 30
Pass through. However, since the distance of this area 31 is short,
Light distribution is not affected. Also, as compared with the case of FIG.
The light in the multi-mode interference region 20 is not distributed immediately below the region 31 that is not buried flat, but is distributed only in the region 32 that is buried flat, so that there is no undesirable effect on the light distribution.

As described above, in the present embodiment, the problem that the upper surface of the buried portion 114 is not flattened during the crystal growth for forming the buried portion 114 of the multimode interference region 20 is avoided. In addition to preventing a decrease in coupling efficiency, a process for flattening the buried portion 114 can be omitted.

In the above description, the semiconductor laser unit 1
0 and the width of the light distribution in the horizontal direction between the optical waveguide section 30 and the optical waveguide section 30 are almost equal.
By optimally setting the length, good optical coupling is realized.

(Fifth Embodiment) A fifth embodiment of the integrated optical circuit device of the present invention will be described in detail with reference to FIG. Specifically, the integrated light conversion element of the present embodiment is:
It is a mode conversion type laser element.

In FIG. 10, the same components as those in the previous embodiments are denoted by the same reference numerals.

First, the manufacturing method will be described.
As in the embodiment, the GaAs substrate 100 is usually
In order to form an optical waveguide by using the MOCVD method of
l_{0. twenty two}Ga_0.78As first light guide layer 101, thickness 2 μm
Al_0.20Ga_0.80As optical waveguide layer 102 and Al_0.22
Ga_0.78As second light guide layers 103 are sequentially laminated.
These layers are formed as non-doped layers. This
Thus, both the semiconductor laser section 10 and the optical waveguide section 30
Then, an optical waveguide is formed.

Next, after the n-type GaAs electrode layer 106 is formed, the n-type Al _0.7 Ga _0.3 As first cladding layer 10 is formed thereon to form the light emitting portion of the semiconductor laser device.
7. i-type GaAs active layer 108 having a thickness of 0.1 μm, p-type Al _0.7 Ga _0.3 As second cladding layer 109, p-type GaAs
s etching stop layer 110 and p-type third cladding layer 1
11 are sequentially laminated. As a result, the semiconductor laser unit 10
The first element region 31 mainly having an optical waveguide action
0 and the second element region 320 mainly having a light emitting action
Are included in a state of being stacked in the layer thickness direction.

Next, RIBE etching for forming the multi-mode interference region 20 is performed. The etching mask pattern at this time also etches both end portions 121 of the optical waveguide portion 30 and, in a subsequent step, the semiconductor laser portion. Embedding part 1 of ten ridges 111 and multimode interference region 20
It is set so that a mesa structure aligned with the line 14 is formed. Also, preferably, as in the second embodiment,
An etching hole for forming the lower electrode 113 is formed in the semiconductor laser unit 10 at the same time.

The RIBE etching is performed until reaching the GaAs substrate 100 as in the first embodiment. After that, the obtained etching groove is buried with AlGaAs to form a buried portion 114. The embedding unit 1
14, the lowermost and uppermost parts each have a thickness of 0.2
At the 5 μm portion, the Al mixed crystal ratio of AlGaAs is 0.29.
In the remaining part, the Al mixed crystal ratio of AlGaAs is set to 0.24. End 12 of Mesa Structure of Optical Waveguide 30
1 is also embedded in the same process as the embedding section 114.

Embedding section 114 of multimode interference area 20
As shown in FIG. 10, the width was set so as to change continuously, and the change in the width was gradual particularly in a narrow region. Thereby, the embedding unit 11
The mode conversion efficiency is improved even when the lengths of the multi-mode interference regions 20 are the same as compared with the case where the width of the line 4 changes linearly.

Embedding part 114 of multimode interference area 20
Is set higher than the Al mixed crystal ratio of the optical waveguide layer 102. For this reason, the light confinement in the lateral direction becomes an anti-guide, and there is a loss due to the leaked light wave in this territory. However, this loss amount is about 0.1 dB / 100 μm, which is not a problem. In the optical waveguide section 30, a single mode waveguide is formed in both the vertical and horizontal directions with a guide structure.

As described above, in this embodiment, highly efficient optical coupling from the semiconductor laser unit 10 to the optical waveguide unit 30 is achieved, and an element that does not require ridge formation in the optical waveguide unit 30 is realized. When the length of the optical waveguide section 30 is sufficiently short, the buried section 114 of the multimode interference region 20 is used.
By setting the Al mixed crystal ratio of the optical waveguide layer 102 to be lower than the Al mixed crystal ratio of the optical waveguide layer 102, the optical waveguide portion 30 can be used as an anti-ideide. Also in this case, the waveguide loss due to the leaked light wave is about 0.1 dB / 100 μm, which is not a problem.

Further, the buried portion 114 of the multi-mode interference region 20 and both ends 12 of the mesa structure in the optical waveguide portion 30 are formed.
1 is embedded with a semiconductor material having a different Al mixed crystal ratio from each other, a guide structure can be realized in both the multimode interference region 20 and the optical waveguide region 30, and low loss and other An integrated semiconductor laser device that can be integrated with the optical device described above is obtained. The invention is not limited to lateral light confinement methods, and such structures are also within the scope of the invention.

(Sixth Embodiment) Hereinafter, a sixth embodiment of the integrated optical circuit device according to the present invention will be described. Specifically, the integrated light conversion device of the present embodiment is a mode conversion laser device.

FIG. 11A is a cross-sectional view (corresponding to the line AA ′ in FIG. 1) of the integrated optical circuit device of the present embodiment, which passes through the buried portion 114 of the multimode interference region 20. It is. The device of this embodiment can be formed by using a process according to a conventional technique or a process described in the first to fifth embodiments of the present invention. However, in this embodiment,
An optical buffer section 40 is further provided between the semiconductor laser section 10 and the optical waveguide section 30. A multimode interference region 201 is provided between the optical buffer unit 40 and the semiconductor laser unit 10 and between the optical buffer unit 40 and the optical waveguide unit 30.
And 202. In the connection using the multi-mode interference regions 201 and 202, there is no displacement between the waveguide layers and the existence of unnecessary layers as in the related art, and the coupling efficiency does not deteriorate due to the multi-stage connection.

The effect of the configuration of the present embodiment will be described.

Assuming that the light distribution widths in the semiconductor laser section 10 and the optical waveguide section 30 are w ₁ and w ₃ , respectively, the coupling efficiency η ₁ when the optical buffer section 40 is not provided is
Equation 3 below,

[0110]

(Equation 3)

Is represented by

On the other hand, the coupling efficiency η _{2 in the} case where the optical buffer unit 40 is provided as in the present embodiment is given by the following formula (4), where the light distribution width in the optical buffer unit 40 is w ₂ .

[0113]

(Equation 4)

Is represented by

When the light distribution widths of the semiconductor laser section 10 and the optical waveguide section 30 are largely different (w ₃ ≫w ₁ ), the value of w ₂ is calculated by the following equation (5).

[0116]

(Equation 5)

By setting according to the equation (4), the coupling efficiency η ₂ in the present embodiment represented by the equation (4) is changed to the coupling efficiency η when the optical buffer layer 40 represented by the equation (3) is not provided.
It can be improved to about twice as large as _one .

By providing the optical buffer section 40 as in the present embodiment, in the configuration having the semiconductor laser section 10 and the optical waveguide section 30 having the same light distribution width as in the first embodiment, the coupling efficiency is reduced by the optical buffer section. This is about 1.4 times higher than the case without the part 40. Thereby, the optical waveguide section 30 can be formed in the same process as the semiconductor laser section 10, and good optical coupling can be realized without lowering the crystal quality due to regrowth. The effect of the multistage connection is obtained by the taper connection, and an integrated optical circuit element having higher reliability than in the prior art is realized.

FIG. 11B shows a modified device configuration of the present embodiment, in which two multimode interference regions 201 and 2 are provided.
02 are made at the same depth. Also in this case, 2
By optimizing the lengths of the two multi-mode interference regions 201 and 202, the same effect as described above can be obtained. The configuration of FIG. 11B has an advantage that the etching process and the embedding process of the two multimode interference regions 201 and 202 can be performed simultaneously.

In the above description, the configuration in which the semiconductor laser section 10 and the optical waveguide section 30 are connected in multiple stages using the optical buffer section 40 has been described. However, the application of the configuration of the present embodiment is limited to the above. It is not something that can be done. For example, the present invention is applicable to coupling between optical waveguides having different thicknesses, and such a structure is also included in the present invention.

(Seventh Embodiment) The embodiment of the present invention
This will be described below. Specifically, the present embodiment describes a different method of manufacturing the integrated optical conversion device in the first embodiment described above, and the obtained device is improved compared to the case of the first embodiment. It has the following characteristics.

In the following description, the same components as those in the previous embodiments are denoted by the same reference numerals.

First, a manufacturing method will be described. As in the first embodiment, a layer 101 for forming an optical waveguide is formed on a GaAs substrate 100 by using a normal MOCVD method.
To 105 are sequentially laminated. Thus, an optical waveguide is formed in both the semiconductor laser unit 10 and the optical waveguide unit 30. Next, layers 107 to 111 forming a light emitting portion of the semiconductor laser device are sequentially laminated on the laminated structure obtained above.

Subsequently, as shown in FIG. 12A, a SiO ₂ mask 117 is patterned on the layer 111, and RIBE etching for forming the multi-mode interference region 20 is performed using the SiO ₂ mask 117 until the GaAs substrate 100 is reached. . R
After the IBE etching, the bottom surface of the etching groove obtained by the RIBE etching may be further flattened by further performing wet etching or the like. Then,
By performing selective growth by MOCVD, three AlGaAs growth layers for forming the buried portion 114 (see FIG. 12B) of the multi-mode interference region 20 are buried in the etching groove obtained by the RIBE etching. 12
B does not show the layers separately.) Embedding part 11
The thickness and composition of each of the three AlGaAs layers constituting the fourth embodiment are the same as those of the first embodiment.

Further, referring to FIG. 12B, an SiO ₂ film pattern 11 is formed on the buried AlGaAs layer so as to connect the semiconductor laser section 10 and the optical waveguide section 30.
8 is formed. Then, using the previously formed SiO ₂ mask 117 and this SiO ₂ film pattern 118, the embedded AlGaAs is formed so that only the portion corresponding to the embedded portion 114 of the multi-mode interference region 20 remains.
Perform RIBE etching on the s layer. Thereby, a lateral light confinement structure in the multimode interference region 20 is formed as shown in FIG. 12B.

Thereafter, ridges 111 and 131 are formed in the semiconductor laser section 10 and the optical waveguide section 30, respectively, by the same process as in the first embodiment. In addition, by wet etching at the time of this ridge formation,
In order to avoid side etching of the buried portion 114 of the multi-mode interference region 20, the exposed side surface 119 of the semiconductor laser portion 10, and the optical waveguide portion 30, the exposed surface 119 should be covered before the etching. Forming a protective film (for example, a SiO ₂ film) or an appropriate material such as a semiconductor material or polyimide.
14 may be embedded in the side 128 (see FIG. 12C). However, when such embedding is performed, embedding is performed according to the type of material used for embedding the side portion 128 of the embedding portion 114 in order to stabilize the lateral mode in the multimode interference region 20. The width of the portion 114 needs to be appropriately designed. In this embodiment, the buried portion 1 is made of a semiconductor material, specifically, Al _0.18 Ga _0.82 As.
Fourteen side portions 128 are embedded.

Finally, the ridge 11 of the semiconductor laser unit 10
An upper electrode 112 is formed on the upper surface of the substrate 1 and a lower electrode (not shown) is formed on the lower surface of the substrate to obtain the configuration shown in FIG. 12C.

When the selective growth as described above is used,
As schematically shown in FIG. 12C or 12D,
It is known that flat growth is not realized near the boundary between the growth region and the non-growth region (masked region) and the growth layer becomes thick. However, in the above-described manufacturing process of the present embodiment, the buried portion 1 of the multimode interference region 20 is used.
12C or FIG. 12D, a region where flat embedding is not realized is formed between the semiconductor laser unit 10 or the optical waveguide unit 30 and the multi-mode interference region 20 because the embedding width in the lateral direction is sufficiently large when forming the semiconductor laser unit 14. The buried portion 11 of the multimode interference region 20 is limited to the vicinity of the interface.
No substantial change in the lateral thickness of 4 occurs.

In this case, as shown in FIG. 12D, the light emitted from the semiconductor laser unit 10
And then reflected by the upper and lower layers.
Actually, it occurs at the center of the multimode interference region 20. In the configuration of the present embodiment, since the central portion of the multi-mode interference region 20 is substantially buried flat, a desired reflection state is realized, and light emitted from the semiconductor laser unit 10 efficiently emits light from the optical waveguide unit. 30.

(Eighth Embodiment) An eighth embodiment of the present invention will be described below. Specifically, the present embodiment describes a different method of manufacturing the integrated optical conversion device in the first embodiment described above, and the obtained device is improved compared to the case of the first embodiment. It has the following characteristics. In the following description, the same components as those in the embodiments described above are indicated by the same reference numerals.

As described in connection with the seventh embodiment, if the buried portion 114 of the multi-mode interference region 20 is made flat, the element characteristics are improved. In the present embodiment, a process that can obtain a buried portion 114 that is further flattened will be described.

First, an ordinary M is placed on a GaAs substrate 100.
The three AlGaAs layers 21 to 23 are formed by using the OCVD method.
Are sequentially laminated. These three AlGaAs layers 21 and 2
The thickness and composition of each of No. 3 are the same as in the first embodiment. At this point, the upper and lower surfaces of the buried portion 114 of the multimode interference region 20 are flat surfaces.

Next, the length of the multimode interference region 20 (FIG. 1)
The length of the in-plane direction of 3A) is 658 μm, which is the same as the element configuration in the second embodiment.
An O ₂ mask 117 is patterned on the uppermost AlGaAs layer 23. Then, this SiO ₂ mask 11
7, the portion other than the multi-mode interference region 20 is
The RIBE etching is performed almost vertically until the s substrate 100 is reached.

Next, in order to carry out a process for forming the semiconductor laser section 10 and the optical waveguide section 30, an SiO ₂ film 117a surrounding the side surface of the multi-mode interference region 20 is formed by bias sputtering. Optimal bias voltage for substrate 1
By the bias sputtering method performed with the voltage applied to 00, on the bottom surface of the etched region, desorption and formation of the SiO ₂ film by ion irradiation compete with each other, and the SiO ₂ film is not substantially formed. Therefore, the multimode interference region 2
The SiO ₂ film 117a is formed only on the 0 side surface.

In the bias sputtering process, a similar competition between desorption and formation occurs with respect to the remaining SiO ₂ mask 117 used in the previous RIBE etching. Since it tends to decrease rather, it is preferable to form it thicker in advance in consideration of this point.

Next, on the surface of the substrate 100 exposed as described above, the layers 101 to 10 for forming the same optical waveguide as in the first embodiment are formed by using the MOCVD selective growth method.
5 are sequentially laminated. Thereby, the semiconductor laser unit 10
An optical waveguide is formed in both the optical waveguide section 30 and the optical waveguide section 30.
Next, layers 107 to 111 forming a light emitting portion of the semiconductor laser device are sequentially laminated on the laminated structure obtained above. As a result, as in the previous embodiments,
The semiconductor laser unit 10 includes a first element region 310 mainly having an optical waveguide function and a second element region 320 mainly having a light emitting function, which are stacked in a layer thickness direction.

In the above selective growth, SiO 2
Crystal growth does not occur on the _two layers 117, and as a result, as shown in FIG. 13A, each of the layers 101 to 105 and 107 to 1
11 is formed substantially horizontally.

Thereafter, as described in the seventh embodiment, a part of the laminated structure including the three AlGaAs layers 21 to 23 is etched to confine light in the lateral direction in the multimode interference region 20. , And then the removed portion is embedded with a suitable material such as polyimide. Thereafter, the ridge forming process described above is performed to form the final structures of the semiconductor laser unit 10 and the optical waveguide unit 30.

According to the manufacturing process of this embodiment, each Al forming the buried layer 114 of the multimode interference region 20 is formed.
The GaAs layers 21 to 23 are formed flat on the surface of the flat GaAs substrate 100. Thereby, the characteristics of the multi-mode interference region 20 are improved.

In the above description, in order to form a semiconductor laser device as an integrated optical device, substantially parallel growth layers 107 to 111 are obtained by using a selective growth method. However, when high coupling efficiency is not required in the coupling between the multimode interference region 20 and the integrated optical element, the growth required by another growth process such as a bias sputtering method instead of the selective growth method is used. A layer may be formed.

In the above description, the side portion of the buried portion 114 of the multi-mode interference region 20 is buried with polyimide, but may be buried with a semiconductor material instead. In this case, after the formation of the laminated structure of the three AlGaAs layers 21 to 23, the portion around the portion corresponding to the buried portion 114 of the multi-mode interference region 20 is illustrated by using a mask 117 having an appropriate pattern. It is removed by etching as shown in FIG. 13B. Then, an SiO ₂ film 117a is formed on the exposed side surface of the embedded portion 114 by a bias sputtering method. Thereafter, as shown in FIG. 13C, the semiconductor laser unit 10 and the optical waveguide unit 3
A final structure of 0 is formed.

In this manner, the formation of the semiconductor laser section 10 and the optical waveguide section 30 and the burying of the side of the buried section 114 of the multimode interference region 20 can be performed by the same process.

[0143]

According to the present invention, an integrated optical circuit element capable of realizing high-efficiency optical coupling between a plurality of optical elements having different light distribution widths in the layer thickness direction and capable of body integration. Can be obtained.

By setting the length and width of the multi-mode interference region optimally, it is possible to reduce the radiation loss related to the inconsistency of the longitudinal mode caused when coupling from one optical element to another optical element, and to reduce the transverse mode. And a reduction in coupling loss due to incomplete embedding (incomplete planarization) during fabrication of the multimode interference region. In addition, by forming the buried portion of the multimode interference region with a material having an aluminum mixed crystal ratio of 0.3 or less, a good device can be manufactured without deposition of the buried material on the mask.

Further, the integrated optical circuit device according to the present invention comprises:
It can be formed by a process simplified compared to the conventional element structure. Specifically, it can be manufactured by two MOCVD growths, and the second MOCVD growth only forms a buried portion in the multi-mode interference region. No deterioration in crystal quality due to regrowth occurs.

When a semiconductor laser device (semiconductor laser portion) and an optical waveguide device (optical waveguide portion) are used as integrated optical devices (optical device portions), a thin boundary layer is provided between the multimode interference region and the semiconductor laser portion. Embedded in an i-type material, an integrated optical circuit element having no leakage current from the semiconductor laser portion can be obtained. Further, according to the present invention, it is possible to simultaneously perform the ridge forming process in the optical waveguide portion when forming the lower electrode of the semiconductor laser portion. Further, the formation of the mesa structure of the optical waveguide portion and the etching of the multi-mode interference region are simultaneously performed, or the formation of the buried portion in the multi-mode interference region and the burying of both ends of the mesa structure of the optical waveguide portion are simultaneously performed. It is also possible. With these, the manufacturing process can be simplified and efficiency can be improved.

If the groove shape is formed by etching at the time of forming the multi-mode interference region, the filling in the groove is made almost flat in the longitudinal direction of the groove, so that the characteristics of the multi-mode interference region are improved.

More preferably, the lamination of the multi-mode interference region is formed by forming a layer functioning as a light-emitting portion of a semiconductor laser device (semiconductor laser portion) or an optical waveguide of a semiconductor laser device (semiconductor laser portion) and an optical waveguide device (optical waveguide portion). Prior to lamination of the layer functioning as a wave layer, the semiconductor laser element (semiconductor laser section) and the optical waveguide element (optical waveguide section) are formed after securing the fabrication area of these elements by etching. To obtain a shaped optical circuit element. As a result, a multimode interference region with even higher flatness is obtained, and the device characteristics are improved.

Further, if a multi-stage connection structure is provided in which a multi-mode interference region for multiple teachings and an optical buffer layer are provided, the coupling efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a configuration of a mode conversion type semiconductor laser device as an integrated optical circuit device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the operation of the device according to the first embodiment of FIG.

FIG. 3 is a perspective view schematically showing a configuration of a mode conversion type semiconductor laser device as an integrated optical circuit device according to a second embodiment of the present invention.

4A is a cross-sectional view illustrating the operation of the device according to the first embodiment illustrated in FIG. 1, and FIG. 4B is a diagram illustrating the operation of the device according to the second embodiment illustrated in FIG. FIG.

FIG. 5 is a diagram illustrating the effect of the second embodiment shown in FIG.

FIG. 6 is a perspective view schematically showing a configuration of a mode conversion type semiconductor laser device as an integrated optical circuit device according to a third embodiment of the present invention.

FIG. 7 is a perspective view schematically showing a configuration of a mode conversion type semiconductor laser device as an integrated optical circuit device according to a fourth embodiment of the present invention.

FIG. 8 is a diagram for explaining a problem related to the configuration of the fourth embodiment shown in FIG. 7;

9 is a cross-sectional view illustrating the operation of the device according to the fourth embodiment shown in FIG.

FIG. 10 is a perspective view schematically showing a configuration of a mode conversion type semiconductor laser device as an integrated optical circuit device according to a fifth embodiment of the present invention.

FIG. 11A is a cross-sectional view schematically showing a configuration of a mode conversion type semiconductor laser device as an integrated optical circuit device according to a sixth embodiment of the present invention, and FIG.
It is sectional drawing which shows the modified structure typically.

FIG. 12A is a schematic perspective view illustrating a step in a method for manufacturing an integrated optical circuit device according to a seventh embodiment of the present invention.

FIG. 12B is a schematic perspective view for explaining another step of the method for manufacturing the integrated optical circuit element in the seventh embodiment of the present invention.

FIG. 12C is a schematic perspective view for explaining still another step of the method for manufacturing the integrated optical circuit element according to the seventh embodiment of the present invention.

FIG. 12D is a sectional view illustrating the operation of the device formed according to the seventh embodiment of the present invention.

FIG. 13A is a schematic perspective view for explaining a step in a method for manufacturing an integrated optical circuit device according to an eighth embodiment of the present invention.

FIG. 13B is a schematic perspective view for explaining one step of another manufacturing method of the integrated optical circuit device according to the eighth embodiment of the present invention.

FIG. 13C is a schematic perspective view for explaining a manufacturing step following FIG. 13B.

FIG. 14 is a cross-sectional view schematically showing a configuration of a certain integrated optical circuit element in the related art.

FIG. 15 is a cross-sectional view schematically illustrating a configuration of another integrated optical circuit element according to the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 semiconductor laser unit 20 multimode interference region 30 optical waveguide unit 40 optical buffer unit 100 GaAs substrate 101 first optical guide layer 102 optical waveguide layer 103 second optical guide layer 104 etching stop layer 105 third optical guide layer 106 electrode formation layer 107 First cladding layer 108 Active layer 109 Second cladding layer 110 Etch stop layer 111 Third cladding layer 112 Electrode 113 Electrode 114 Embedding part 115 Buffer waveguide layer 116 Thin boundary layer 201, 202 Multimode interference region

Claims (13)

[Claims] 1. A first optical element section including first and second element regions stacked in a layer thickness direction, and a second optical element formed at a position distant from the first optical element section. And a multi-mode interference region having a buried portion formed in the light propagation direction, located between the first optical element portion and the second optical element portion, An integrated optical circuit device, wherein the first optical device portion and the second optical device portion are optically coupled via the multimode interference region. 2. The buried portion of the multimode interference region moves parallel to the light emitted from the first optical element while maintaining the light distribution shape at the time of emission from the first optical element. The integrated optical circuit element according to claim 1, wherein the length is set to reach the second optical element section. 3. The integrated optical circuit device according to claim 1, wherein a width of the buried portion of the multimode interference region in a direction perpendicular to a light propagation direction changes continuously or stepwise. 4. The integrated optical circuit device according to claim 1, wherein a thin boundary layer is formed between said first optical device section and said multimode interference region. 5. A first optical element unit including first and second element regions stacked in a layer thickness direction and having different light distribution widths, and light emitted from the first optical element unit. A multimode interference region having a buried portion having a multimode waveguide structure in each of the layer thickness direction and an in-plane direction perpendicular to the layer thickness direction, formed in the propagation direction of the first light; A second optical element portion formed at a position distant from the element portion via the multimode interference region, wherein the light emitted from the first optical element portion is provided in the multimode interference region. Is propagated to the second optical element section, whereby the first optical element section and the second optical element section are optically coupled to each other. 6. The mesa structure according to claim 1, wherein the second optical element unit has a mesa structure aligned with the first optical element unit and the buried part of the multi-mode interference region. 6. The integrated optical circuit device according to any one of items 1 to 5, 7. The buried portion of the multi-mode interference region is configured by stacking two or more sub-regions.
An integrated optical circuit device according to claim 1. 8. A first optical element portion having first and second element regions stacked in a layer thickness direction, and a second optical element disposed at a position separated from the first optical element portion Simultaneously forming a portion, a first etching step of etching an area between the first optical element portion and the second optical element portion to form an etching groove, A burying step of forming a buried portion of the multi-mode interference region therein. 9. In the first etching step, the entirety of the formation portion of the multi-mode interference region is etched to form the etching groove, and in the embedding step, the entirety of the etching groove is formed in the multi-mode interference region. Forming a first buried layer by burying with a constituent material of the buried portion, and removing a predetermined portion of the first buried layer by etching;
A second etching step of leaving a portion corresponding to the buried portion of the multi-mode interference region; The method for manufacturing an integrated optical circuit device according to claim 8, further comprising: forming. 10. The method according to claim 8, wherein in the first etching step, a mesa structure for lateral confinement in the second optical element portion is formed at the same time. 11. A step of forming a multi-mode interference region having a buried portion, and etching a predetermined region around the multi-mode interference region to remove at least two removed regions from the buried region of the multi-mode interference region. Forming a first optical element portion in which the first and second element regions are stacked in the layer thickness direction on one of the at least two removed regions, and Forming an integrated optical circuit element at the same time. 12. An etching step for forming the multi-mode interference region and an etching step for forming a mesa structure for lateral confinement in the second optical element portion are simultaneously performed. Item 12. The method for manufacturing an integrated optical circuit device according to item 11. 13. The method according to claim 8, wherein the formation hole of the upper electrode of the first optical element portion and the ridge of the second optical element portion are simultaneously formed by the same etching process. A manufacturing method of the integrated optical circuit element described in the above.