JP2002107559A - Substrate for optical integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an optical integrated circuit substrate and shorten the height of it while optically coupling an optical waveguide with a semiconductor photodetector with high light receiving efficiency. SOLUTION: The optical integrated circuit substrate is provided with a surface light receiving type semiconductor photodetector 2 which is disposed on a substrate 1 and an optical waveguide which is formed on the semiconductor light photodetector 2 and has at least a lower clad part 3 and a core part 4. The core part 4 is bent in a nearly V shape over the semiconductor photodetector 2 and its bottom part is abutted on the light receiving surface of the semiconductor light photodetector 2. Since light propagating through the core part 4 is directly inputted into the light receiving surface from the bottom part abutted on the light receiving surface, the efficiency of the optical coupling between the optical waveguide and the semiconductor photodetector 2 is high, and optical coupling is efficiently performed with a small light receiving area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical integrated circuit board in which an optical waveguide and a semiconductor light receiving element are integrated on the same substrate, for example, a WDM (Wavelength Division Multiplex: WDM).
It is suitably used when a plurality of semiconductor light-receiving elements and other devices are mounted on the same substrate, such as a light-receiving circuit substrate for wavelength division multiplex transmission, and the optical waveguide and the semiconductor light-receiving element are integrated on the same substrate. In addition, the present invention relates to an optical integrated circuit substrate capable of realizing a reduction in substrate size and an increase in light receiving efficiency.

[0002]

2. Description of the Related Art Conventionally, the connection between a semiconductor light receiving element and an optical waveguide in an optical integrated circuit board such as a light receiving circuit board for WDM is performed by mounting the semiconductor light receiving element above the optical waveguide layer.
In general, light from an optical waveguide is input to a light receiving section of a semiconductor light receiving element by changing an optical path through a mirror or a grating formed in the optical waveguide.

In this method, a semiconductor light receiving element is integrated on an optical waveguide layer, and the size of the entire substrate is large. In addition, when mounting the semiconductor light receiving element, it is necessary to perform image recognition by applying infrared light from the back side to perform alignment, and a substrate for manufacturing an optical integrated circuit must be a substrate that transmits infrared light. Therefore, there is also a limitation on the type of substrate material. Further, the process of manufacturing mirrors and gratings to be formed in the optical waveguide is complicated.

Therefore, an example of an optical integrated circuit board having a reduced board size has been proposed in Japanese Patent Application Laid-Open No. 3-191572. FIG. 4 is a cross-sectional view showing an example thereof. In FIG.
Is an Si substrate, 22 is an insulating or conductive bonding member, 23 is an n-type part of the light-receiving element chip, 24 is a p-type part of the light-receiving element chip, 25 is a high refractive index layer corresponding to a core part of the optical waveguide, 26 is a low-refractive-index layer corresponding to the clad part of the optical waveguide, 27 is a p-type part of the light-emitting element chip, and 28 is an n-type part of the light-emitting element. The n-type part 23 and the p-type part 24 of the light-receiving element chip form a light-receiving part, and the p-type part 27 and the n-type part 28 of the light-emitting element chip form a light emitting part.

According to this, a light receiving element chip and a light emitting element chip are formed in a V-groove formed in the Si substrate 21 with a planarizing material.
Since the groove is filled with 29, the entire height of the optical integrated circuit substrate is determined by the height of the Si substrate 21, the core portion 25 and the clad portion 26 of the optical waveguide, and the optical waveguide and the semiconductor light receiving element Is realized compactly.

FIG. 5 is a sectional view showing an example of an optical integrated circuit board proposed in Japanese Patent Application Laid-Open No. Hei 7-128531. The core part 35 of the optical waveguide formed in the clad part 36 is bent so as to ride on the upper surface of the semiconductor light receiving element composed of the semiconductor layer 33 and the light absorbing layer 34, and is formed between the end face of the semiconductor light receiving element and the core part 35. Is embedded in the lower clad portion 36, and the light emitted from the bent portion of the core portion 35 is taken into the light absorbing layer 34 of the semiconductor light receiving element, thereby coupling efficiency between the optical waveguide and the semiconductor light receiving element. Is higher.

[0007]

However, with respect to the optical integrated circuit board proposed in Japanese Patent Application Laid-Open No. 3-191572, it is necessary to form a V-groove in order to embed a light-receiving element and a light-emitting element. There has been a problem that the optical waveguide and the semiconductor light receiving element can be integrated only on the Si substrate on which can be formed.

Further, in the structure shown in FIG. 4, when estimated by simulation, only about 10% of the light propagating through the optical waveguide is coupled to the light receiving portion of the semiconductor light receiving element, and the light receiving efficiency is low. .

Further, regarding the optical integrated circuit board proposed in Japanese Patent Application Laid-Open No. Hei 7-128531, the optical waveguide and the semiconductor light receiving element are regarded as two parallel optical waveguides, respectively, and the principle of coupling of the optical waveguides is used. Although light coupling is considered, light is emitted at the bent portion of the core portion 35 of the optical waveguide to increase the optical coupling efficiency between the optical waveguide and the semiconductor light receiving element.

However, in this example, according to the principle of optical coupling, since the difference in the refractive index between the optical waveguide and the light receiving portion of the semiconductor light receiving element is large, the light propagating through the optical waveguide propagates through the semiconductor light receiving element. Requires very long bond lengths. FIG. 6 is a diagram showing an example of the coupling efficiency with respect to the coupling length (Waveguide length) when the optical waveguide and the semiconductor light receiving element are considered as two parallel optical waveguides. In FIG. 6, the horizontal axis represents the coupling length Waveguide length (unit: μm), the vertical axis represents the coupling coefficient Coupling efficient, and the black square points and the characteristic curves show how the coupling coefficient changes with the coupling length. As you can see,
Even when inputting 10% of the light propagating through the optical waveguide, a very long distance of about 1500 μm is required, and it is difficult to reduce the size of the substrate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to integrate a semiconductor light receiving element for light propagating through an optical waveguide, which can be integrated on various substrates other than a Si substrate. An object of the present invention is to provide an optical integrated circuit substrate having high light receiving efficiency.

[0012]

An optical integrated circuit board according to the present invention comprises: a surface light receiving type semiconductor light receiving element disposed on a substrate;
An optical waveguide having at least a lower cladding part and a core part formed on the semiconductor light receiving element, wherein the core part is bent substantially in a V shape above the semiconductor light receiving element and has a bottom part. Are in contact with the light receiving surface of the semiconductor light receiving element.

Further, in the optical integrated circuit board according to the present invention, in the above-described configuration, the bottom portion of the core portion bent in a substantially V-shape is a light propagating through the core portion between its upper surface and the light receiving surface. Has a region parallel to the light receiving surface so that the light is reflected a plurality of times.

In the optical integrated circuit board according to the present invention, in each of the above structures, the bottom portion of the core portion bent in a substantially V-shape may be a dielectric or metal whose upper surface has a lower refractive index than the core portion. It is characterized by being covered with.

[0015]

According to the optical integrated circuit substrate of the present invention, an optical waveguide is laminated on a surface light receiving type semiconductor light receiving element mounted or formed on a substrate, for example. As a result, the semiconductor light receiving element and the optical waveguide can be efficiently integrated on the same substrate, and the semiconductor light receiving element is mounted after forming the optical waveguide on the substrate as in the related art. Since it is possible to reduce the size and height as compared with the integrated circuit substrate and to mount and mount another optoelectronic device or the like on this optical waveguide,
In particular, even for an optical integrated circuit substrate in which a plurality of semiconductor light receiving elements and a plurality of optoelectronic devices are mounted on the substrate, the size of the optical integrated circuit substrate can be reduced.

Further, according to the optical integrated circuit board of the present invention,
Various substrates can be used as long as the substrate can form a semiconductor light receiving element or a substrate on which a semiconductor light receiving element can be mounted and mounted. Need to form a V-groove
Not only i-substrate but also ceramic substrate with good electrical characteristics,
Suitable substrates can be used for high-speed signal processing and high integration of optoelectronic devices.

According to the optical integrated circuit board of the present invention,
An optical waveguide having at least a lower cladding part and a core part is formed on a surface light receiving type semiconductor light receiving element, and this core part is bent in a substantially V shape above the semiconductor light receiving element so that the bottom part is formed. Since the light receiving surface of the semiconductor light receiving element is in contact with the light receiving surface, light propagating through the core portion is brought into contact with the light receiving surface as compared with the conventional coupling using the coupling theory of two optical waveguides. An optical integrated circuit that can directly input light from the bottom of the core part to the light receiving surface, so that the optical coupling between the optical waveguide and the semiconductor light receiving element is high and the optical coupling can be efficiently performed with a small light receiving area It becomes a substrate.

According to the optical integrated circuit substrate of the present invention,
A substantially V-shaped bent bottom of the core portion of the optical waveguide forms an area parallel to the light receiving surface between the upper surface and the light receiving surface of the semiconductor light receiving element so that light propagating through the core portion is reflected multiple times. When light is directly input to the light receiving surface from the substantially V-shaped bottom portion of the core portion, the light receiving surface of the semiconductor light receiving element has the bottom surface of the core portion having a large refractive index difference and the light receiving surface of the semiconductor light receiving element. The light reflected at the interface is reflected on the upper surface of the region parallel to the light receiving surface and is input to the light receiving surface again. By repeating this plural times, the optical integrated circuit can further increase the light receiving efficiency. It becomes a substrate.

Further, according to the optical integrated circuit board of the present invention, is the bottom portion of the core portion of the optical waveguide bent in a substantially V shape covered with a dielectric material having a lower refractive index than that of the core portion? Or when covered with metal, when light is directly input to the light receiving surface from the substantially V-shaped bent bottom of the core, the bottom surface of the core having a large refractive index difference and the semiconductor light receiving element The light reflected at the interface with the light receiving surface of the optical integrated circuit substrate that can be reliably reflected on the upper surface covered with the dielectric or metal and is input to the light receiving surface again, thereby further improving the light receiving efficiency Becomes When used in combination with the above-described one having a region parallel to the light receiving surface, light incident on the upper surface of the bottom of the core portion can be reliably and efficiently reflected and input to the light receiving surface again. And a high-efficiency optical integrated circuit substrate that can further enhance the optical integrated circuit substrate.

Hereinafter, an optical integrated circuit substrate according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an optical integrated circuit board showing an example of an embodiment of the optical integrated circuit board of the present invention.

As shown in FIG. 1, an optical integrated circuit board of the present invention is formed on a surface light receiving type semiconductor light receiving element 2 provided on a substrate 1 and on the semiconductor light receiving element 2 on the substrate 1. Further, an optical waveguide including a lower clad part 3, a core part 4, and an upper clad part 5 is provided. Note that the upper clad portion 5 is not always necessary, and that the upper clad portion 5 is not formed, and the upper portion of the core portion 4 is made of air (having a relative dielectric constant of about 1). Good transmission and good optical connection to the semiconductor light receiving element 2 can be performed.

In the example shown in FIG. 1, the core portion 4 of the optical waveguide formed on the semiconductor light receiving element 2 is bent in a substantially V shape above the semiconductor light receiving element 2 and the bottom thereof is
Abut on the light receiving surface. As a result, light propagating through the optical waveguide comes into contact with the core portion 4 from the bottom at the bent portion, as compared with the coupling using the coupling theory of two optical waveguides as in the conventional optical integrated circuit board. Since the light is directly input to the light receiving surface of the semiconductor light receiving element 2, optical coupling can be efficiently performed with a small light receiving area.

Next, FIG. 2 shows another embodiment of the optical integrated circuit board according to the present invention in a sectional view similar to FIG. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals. Also in this example, the upper clad part 5 of the optical waveguide is not always necessary.

In the example shown in FIG. 2, the core portion 4 of the optical waveguide formed on the semiconductor light receiving element 2 is bent in a substantially V shape above the semiconductor light receiving element 2 and the bottom thereof is
The light reflected at the interface between the bottom surface of the core portion 4 and the light receiving surface of the semiconductor light receiving element 2 propagates through the core portion 4 while the bottom surface is in contact with the light receiving surface of the semiconductor light receiving element 2.
Has a region parallel to the light receiving surface so as to be reflected a plurality of times with the light receiving surface. Thereby, as shown by arrows in the drawing, the light propagating in the core portion 4 is reflected on the upper surface of the region parallel to the light receiving surface at the bottom and is input to the light receiving surface again, and The light reflected on the surface is further reflected on the upper surface and input to the light receiving surface, and this can be repeated a plurality of times, so that the optical integrated circuit substrate can further improve the light receiving efficiency.

In the example shown in FIGS. 1 and 2,
Numeral 6 denotes a dielectric or metal having a lower refractive index than the core 4 and covers the upper surface of the bottom of the core 4 which is bent in a substantially V shape. The dielectric or metal 6 replaces a part of the upper clad part 5 located above the core part 4 of the optical waveguide which is bent in a substantially V-shape as shown in FIG. The upper clad portion 5 may be removed, the upper clad portion 5 may be removed, and the upper clad portion 5 may be applied as a film covering the exposed upper surface of the core portion 4. Then, the upper surface of the core portion 4 is exposed to air, and air having a low refractive index is covered with a dielectric material 6 covering the upper surface of the core portion 4.
May be used. When the refractive index of the upper clad 5 is sufficiently lower than that of the core 4, the upper clad 5 may be used as it is as the dielectric 6.

By covering the upper surface of the bottom portion of the core portion 4 bent in a substantially V-shape with the dielectric or metal 6 having a lower refractive index than the core portion 4 in this manner, the bottom surface of the core portion 4 and the semiconductor light receiving element 2 are covered. The light reflected at the interface with the light receiving surface is surely reflected on the upper surface of the core portion 4 covered with the dielectric or metal 6, and is input to the light receiving surface again, so that the light receiving efficiency can be further improved. it can. When the bottom of the core 4 has a region parallel to the light receiving surface, the core 4
The light incident on the upper surface of the bottom can be efficiently and reliably reflected a plurality of times, and can be input again to the light receiving surface, thereby providing a highly efficient optical integrated circuit substrate that can further increase the light receiving efficiency. .

In the optical integrated circuit board of the present invention, the semiconductor light receiving element 2 is provided, and the optical waveguide is formed thereon. Various substrates used, for example, a silicon substrate, an alumina substrate, a glass ceramic substrate, a multilayer ceramic substrate, and the like can be used.

The surface light receiving type semiconductor light receiving element 2 disposed on the substrate 1 includes, for example, a photodiode (PN photodiode / PIN photodiode or avalanche photodiode / MSM (Metal-Semiconductor-
Metal) photodiodes, etc. are used, and these are mounted or mounted or formed and disposed. The light receiving surface of the semiconductor light receiving element 2 is basically located above the element 2 substantially in parallel with the upper surface of the substrate 1, but is not limited to such a position. May be located anywhere. However, depending on the position of the light receiving surface, it is necessary to carry out an optimal design for obtaining the maximum light receiving efficiency and to form an optical waveguide corresponding to the optimal design.

The optical waveguide formed on the substrate 1 and the semiconductor light receiving element 2 has at least a lower clad part 3 and a core part 4, preferably an upper clad part 5.
Is a three-dimensional waveguide shape optical waveguide composed of three layers having the following. It is desirable to use, for example, a siloxane-based polymer as the forming material. If the optical waveguide is made of a siloxane-based polymer, the lower and upper clad portions 3 and 5 are made of a siloxane-based polymer, and the core portion 4 is made of a siloxane-based polymer containing a metal, for example, titanium (Ti). Thereby, an optical waveguide having a desired refractive index difference can be easily manufactured by controlling the titanium content, and it becomes easy to design a structure having the maximum light receiving efficiency with the semiconductor light receiving element 2.

As such a siloxane-based polymer,
Any resin may be used as long as it has a siloxane bond in the polymer skeleton. Examples thereof include polyphenylsilsesquioxane, polymethylphenylsilsesquioxane, and polydiphenylsilsesquioxane.

The metal contained in the core portion 4 and the cladding portions 3 and 5 is not limited to titanium, but may be germanium (Ge), aluminum (Al), erbium (Er), or the like. In order to form the core portion 4 containing these metals, a siloxane-based polymer layer to which the metal alkoxide is added may be formed and processed into desired shapes and dimensions.

The siloxane-based polymer used for the cladding portions 3 and 5 may contain the same metal as described above.
In that case, a difference in refractive index may be provided depending on a difference in content from the core portion 4.

In addition, as a material of the optical waveguide, there is a combination of a core member and a clad member having transparency that can transmit light with low loss and that can obtain a desired refractive index difference. Various materials can be used as long as they are present. In addition to the siloxane-based polymer, for example, fluorinated polyimide / polymethyl methacrylate (PMMA)
-An optical material such as polycarbonate (PC) that can be applied in a solution state is suitably used.

The thickness of the lower cladding 3, that is, the substrate 1
The thickness from the material to the core portion 4 formed substantially parallel to the substrate 1 is determined by experimentation in advance so that the material does not cause radiation loss due to the interaction with the substrate 1, and is formed to be equal to or greater than the thickness.

The core portion 4 which is bent in a substantially V-shape, and whose bottom portion is in contact with the light receiving surface of the semiconductor light receiving element 2, determines the length of the bottom portion in contact with the light receiving surface by the sensitivity of the semiconductor light receiving element 2. And the size of the light receiving area, and are designed to obtain the maximum coupling efficiency by calculation with a simulator or the like. In order to realize such a designed structure, first, a siloxane-based polymer serving as a material of the lower cladding part 3 is dropped on the substrate 1 on which the semiconductor light receiving element 2 is disposed,
The lower clad portion 3 is formed using a device capable of applying an optical material such as a spin coater or a bar coater on the substrate 1, and thereafter, the film on the light receiving surface of the semiconductor light receiving element 2 is processed by etching. I do. As an apparatus used for etching, for example, ECR, RIE, laser, or the like can be adopted. By optimizing the respective etching conditions, it is possible to process a shape according to the design. Then, a core portion 4 is formed thereon, and processed into a desired shape by etching in the same manner to form an optical waveguide.

The upper surface of the bottom of the core portion 4 which is bent in a substantially V-shape, in addition to the formation of the upper clad portion 5 as it is, is capable of reliably reflecting propagating light on the upper surface of the bottom. Therefore, it is preferable to cover with a dielectric or metal 6 having a lower refractive index than the core 4 and the upper clad 5. The material of such a low-refractive-index dielectric or metal 6 includes the core 4 and the upper clad 5
The smaller the refractive index is, the better the refractive index difference from the core portion 4 is. For example, an air layer may be used as described above, and a transparent dielectric such as magnesium fluoride (MgF ₂ ) / lithium fluoride (LiF) or gold (Au) / aluminum (Al) / silver (Ag) may be used. And the like.

The optical integrated circuit board of the present invention as shown in FIGS. 1 and 2 has a large number of semiconductor light receiving elements 14 disposed on a substrate 11 as shown in, for example, a perspective view in FIG. An optical waveguide 13 is formed thereon, and is used for an optical integrated circuit module or the like in which a large number of optoelectronic devices such as an optical amplifier 15 are mounted. It is possible to reduce the size of the module while optically coupling the element 14 with high light receiving efficiency.

In FIG. 3, reference numeral 12 denotes an optical fiber for exchanging optical signals with the outside, and reference numeral 16 denotes an electrode portion formed on the substrate 11 for driving the optical amplifier 15.

[0040]

Next, a specific example of the optical integrated circuit board of the present invention will be described.

[Example 1] First, a surface light receiving type semiconductor light receiving element 2 is mounted on an alumina substrate 1, and lower and upper cladding portions 3.5 are made of a siloxane-based polymer, and a core portion 4 is made of a titanium-containing siloxane-based polymer. An optical integrated circuit substrate having the same configuration as the example shown in FIG. At this time, the refractive index of the core 4 and the claddings 3 and 5 is 1.450 and 1.445, respectively, the width of the core 4 is 6 μm, the height is 6 μm, and the thickness of the lower cladding 3 (from the substrate 1 to the substrate 1 in parallel). The thickness up to the formed core 4) is 10 μm, and the upper clad 5
Was 10 μm in thickness. The semiconductor light receiving element 2 had a thickness of 2 μm and a light receiving area of 200 μm in diameter.

The upper surface of the semiconductor light-receiving element 2 is in contact with the lower surface of the bottom of the core portion 4 bent substantially in a V-shape thereon. The angle between the part 4 and the semiconductor light receiving element 2 is about 10 degrees.
The length of the parallel region at the bottom of the core portion 4 on the light receiving surface was 6 μm.

Further, on the upper surface of the bottom of the core portion 4 located above the semiconductor light receiving element 2, after forming an upper clad portion 5, a mask pattern for etching is formed thereon.
The upper clad portion 5 was removed by dry etching by RIE, so that the upper clad portion 5 was covered with an air layer.

When the coupling efficiency between the optical waveguide and the semiconductor light receiving element 2 of the optical integrated circuit board of the present invention thus manufactured was measured, it was about 30%, which is about three times that of the optical integrated circuit board according to the prior art. It was confirmed that the coupling efficiency was as follows.

In the above embodiment, an alumina substrate was used as the substrate 1. However, even when an aluminum nitride substrate, a silicon substrate, a glass ceramic substrate, or the like was used, good coupling efficiency was similarly obtained. .

Also, as in the example shown in FIG.
A structure in which a region parallel to the light-receiving surface of the semiconductor light-receiving element 2 is not formed at the bent bottom of the semiconductor light-receiving element 2 and the semiconductor light-receiving element 2 is coupled to the light-receiving surface of the semiconductor light-receiving element 2 only at the bottom that contacts the light-receiving surface at a predetermined angle. Had good coupling efficiency. Such a structure in which the region parallel to the light receiving surface is not provided at the bottom of the core portion 4 is effective particularly when the light receiving area of the semiconductor light receiving element 2 is small.

It should be noted that the above is only an example of the embodiment of the present invention, and the present invention is not limited to the embodiment. Various changes and improvements can be made without departing from the gist of the present invention. No problem.

[0048]

As described above, according to the optical integrated circuit substrate of the present invention, an optical waveguide is formed so as to be stacked on a surface light receiving type semiconductor light receiving element provided on the substrate. As a result, the semiconductor light receiving element and the optical waveguide can be efficiently integrated on the same substrate, and an integrated circuit substrate on which the semiconductor light receiving element is mounted after forming the optical waveguide on the substrate as in the related art. Compared to miniaturization and height reduction,
Since further opto-electronic devices can be mounted and mounted on this optical waveguide, miniaturization is realized especially by using an optical module in which a plurality of semiconductor light receiving elements and opto-electronic devices are respectively mounted on a substrate. can do.

According to the optical integrated circuit board of the present invention,
Various substrates can be used as long as a substrate on which a surface light receiving type semiconductor light receiving element can be provided, and a substrate suitable for high-speed signal processing and high integration of an optoelectronic device can be used.

According to the optical integrated circuit board of the present invention,
An optical waveguide having at least a lower cladding part and a core part is formed on a surface light receiving type semiconductor light receiving element, and this core part is bent in a substantially V shape above the semiconductor light receiving element so that the bottom part is formed. Since the light receiving surface of the semiconductor light receiving element is in contact with the light receiving surface, light propagating through the core can be directly input to the light receiving surface from the bottom of the core in contact with the light receiving surface. The coupling efficiency of the optical coupling with the light receiving element is high, and the optical coupling can be efficiently performed with a small light receiving area.

According to the optical integrated circuit board of the present invention,
A substantially V-shaped bent bottom of the core portion of the optical waveguide forms an area parallel to the light receiving surface between the upper surface and the light receiving surface of the semiconductor light receiving element so that light propagating through the core portion is reflected multiple times. If it has, the light reflected at the interface between the bottom surface of the core portion and the light receiving surface of the semiconductor light receiving element is reflected on the upper surface of a region parallel to the light receiving surface and is input to the light receiving surface a plurality of times again. As a result, the light receiving efficiency can be further increased.

Further, according to the optical integrated circuit board of the present invention, the substantially V-shaped bottom of the core portion of the optical waveguide is covered with a dielectric or metal whose refractive index is lower than that of the core portion. In this case, the light reflected at the interface between the bottom surface of the core and the light receiving surface of the semiconductor light receiving element is surely reflected by the upper surface covered with the dielectric or metal and is input to the light receiving surface again. And the light receiving efficiency can be further increased. When used together with a semiconductor light receiving element having a region parallel to the light receiving surface of the semiconductor light receiving element at the bottom of the core, light incident on the upper surface of the bottom of the core is reliably reflected efficiently and input to the light receiving surface again. Thus, a highly efficient optical integrated circuit substrate that can further increase the light receiving efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an embodiment of an optical integrated circuit substrate according to the present invention.

FIG. 2 is a sectional view showing another example of the embodiment of the optical integrated circuit substrate of the present invention.

FIG. 3 is a perspective view showing an example of an optical integrated circuit module using the optical integrated circuit of the present invention.

FIG. 4 is a cross-sectional view illustrating an example of a conventional optical integrated circuit substrate.

FIG. 5 is a sectional view showing another example of a conventional optical integrated circuit substrate.

FIG. 6 is a diagram illustrating a change in coupling efficiency with respect to a coupling length when an optical waveguide and a semiconductor light receiving element are considered as two parallel waveguides.

[Explanation of symbols]

1, 11 ... substrate 2, 14 ... semiconductor light receiving element 3 ... lower cladding part of optical waveguide 4 ... core part of optical waveguide 5 ... upper cladding of optical waveguide Portion 6: Dielectric or metal having lower refractive index than core portion 4

Claims (3)

[Claims] A semiconductor light receiving element of a surface light receiving type disposed on a substrate; and an optical waveguide formed on the semiconductor light receiving element and having at least a lower cladding part and a core part. An optical integrated circuit board, wherein the core portion is bent in a substantially V-shape above the semiconductor light receiving element, and a bottom portion thereof is in contact with a light receiving surface of the semiconductor light receiving element. 2. The bottom portion of the core portion, which is bent in a substantially V shape, is parallel to the light receiving surface so that light propagating through the core portion between the upper surface and the light receiving surface is reflected a plurality of times. 2. The optical integrated circuit substrate according to claim 1, wherein the substrate has an area. 3. The bottom portion of the core portion, which is bent in a substantially V-shape, has an upper surface covered with a dielectric or a metal having a lower refractive index than the core portion. The optical integrated circuit board according to claim 2.