JP2008102283A - Optical waveguide, optical module and method of manufacturing optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module with an optical waveguide, which is optically coupled with a surface type optical element with a simple configuration. <P>SOLUTION: The optical module 1A includes: the optical waveguide 2A in which a waveguide part 22A having a core 20 and a clad 21 is supported by a supporting substrate 23A as a unit; a surface emitting type semiconductor laser 3A and a photodiode 4 which are optically connected to the optical waveguide 2A; and a mounting substrate 5 on which the optical waveguide 2A, the surface emitting type semiconductor laser 3A and the photodiode 4 are mounted. The optical waveguide 2A has: a reflection face 24 which is provided by exposing a core end face 20a by tilting an end face of the waveguide part 22A along the extending direction of the core 20 by a predetermined angle; and a recessed mounting part 26A provided by opening the supporting substrate 23A at the position facing to the core end face 20a to accommodate the surface emitting type semiconductor laser 3A and the photodiode 4 mounted on the mounting substrate 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical waveguide having a reflection surface on which light is incident / exited in a direction perpendicular to the core by tilting an end face of a waveguide portion having a core and a clad, and an optical module including the optical waveguide And a method of manufacturing the optical waveguide. Specifically, a support substrate for supporting the waveguide portion is provided, and the support substrate is provided with a mounting recess by opening a position opposite to the core end surface exposed to the reflection surface, so that it optically communicates with the core via the reflection surface. A space for mounting the optical elements to be coupled can be formed on the optical waveguide side.

  Conventionally, information transmission between boards in electronic devices, between chips, etc. has been performed by electrical signals, but optical wiring technology has attracted attention in order to realize ultra high speed, large capacity information transmission, An optical module using an optical waveguide has been proposed.

  A waveguide-type optical module includes a light-emitting element that converts an electrical signal into an optical signal and outputs it, and a light-receiving element that converts a received optical signal into an electrical signal, and the optical waveguide and the optical element are optically coupled. ing.

  Among the optical elements, the surface type optical element is easier to manufacture than the end face type and suitable for surface mounting. This is advantageous. In particular, a surface emitting semiconductor laser element (VCSEL) has a merit of being capable of direct modulation at high speed, and is very promising as a device for a low-cost optical module. Optical modules are demanded.

  Conventionally, as a coupling structure of an optical waveguide and a planar optical element, a planar light emitting element is mounted on a substrate surface, an optical waveguide is mounted on a guide groove of the same substrate, and the light emitting element is substantially perpendicular to the substrate. In order to make the light emitted to the light incident on the optical waveguide that guides the light in the horizontal direction with respect to the substrate, an optical module in which an optical path conversion unit is mounted on the top of the light emitting element has been proposed (for example, Patent Documents) 1).

  In addition, an optical module that does not use an optical path conversion unit by forming a reflection surface of 45 degrees on the end surface of the optical waveguide and performing optical path conversion in the waveguide has been proposed (see, for example, Patent Document 2). .

Japanese Patent Laid-Open No. 2002-031747 (FIG. 1) JP 2003-215371 A (FIG. 1)

  In an optical module in which the optical path conversion unit is a separate component, the number of components that need to be aligned increases, so the coupling efficiency decreases. In addition, the assembly process is complicated due to the large number of parts that need to be aligned.

  On the other hand, by using a light guide that forms a reflection surface of 45 degrees on the end face of the waveguide and performs optical path conversion in the waveguide, an optical path conversion unit as a separate component becomes unnecessary. However, since light enters and exits from a direction substantially perpendicular to the optical waveguide, it is necessary to have a configuration in which an optical element is disposed on the upper surface side or the lower surface side of the optical waveguide.

  In the configuration in which the optical element is disposed on the upper surface side of the optical waveguide, for example, the optical element is mounted on the substrate via solder bumps having a predetermined height. However, in such a mounting form, it is difficult to precisely position the optical element and the optical waveguide, and the coupling efficiency is lowered. Further, heat generated from the optical element is mainly transmitted to the space, and sufficient heat dissipation cannot be performed as compared with a configuration in which heat is transmitted to the substrate.

  On the other hand, in the configuration in which the optical element is arranged on the lower surface of the optical waveguide, the optical element can be mounted on the substrate, which is advantageous in terms of heat dissipation. It is necessary to do this, and a normal electric circuit board cannot be used, which increases the cost.

  If the optical waveguide is supported by a submount that is separate from the optical waveguide, the concave portion is unnecessary on the substrate on which the optical element is mounted, but the number of parts increases, so the error in dimensional accuracy of each part is reduced. Addition reduces the coupling efficiency.

  Furthermore, if the optical waveguide is made thick and the concave portion into which the optical element is inserted is formed integrally, it becomes difficult to control the height dimension of the optical waveguide, and the gap between the optical element and the incident / exit surface is made constant. It cannot be controlled and the coupling efficiency decreases.

  The present invention has been made to solve such a problem, and an optical waveguide that can be optically coupled to a planar optical element with a simple configuration, an optical module including the optical waveguide, and a method of manufacturing the optical waveguide The purpose is to provide.

  In order to solve the above-described problems, an optical waveguide according to the present invention is an optical waveguide that includes a waveguide portion having a core and a cladding, and a support substrate that supports the waveguide portion. In addition, the support substrate is provided with a reflective surface in which one end surface along the surface is inclined at a predetermined angle so as to expose the core end surface of the core, and the support substrate is opened at a position facing the core end surface exposed on the reflective surface. It is provided with.

  In the optical waveguide of the present invention, the light is reflected in a predetermined direction by the reflecting surface with the end face of the core exposed, so that the light path is converted and light enters and exits from a direction substantially perpendicular to the direction in which the core extends.

  As a result, the waveguide portion of the optical waveguide is a light incident / exit surface that faces the reflecting surface, and the mounting recess formed on the support substrate that supports the waveguide portion enters / exits the position facing the core end surface. The surface is exposed.

  Therefore, the optical waveguide and the optical element can be optically coupled by mounting the optical element optically coupled to the core via the reflecting surface for converting the optical path in the mounting recess.

  An optical module of the present invention includes an optical waveguide in which a waveguide portion having a core and a cladding is supported by a support substrate, an optical element coupled to the core, and a mounting substrate on which the optical waveguide and the optical element are mounted, The optical waveguide includes a reflection surface in which one end surface of the waveguide portion along the direction in which the core extends is inclined at a predetermined angle to expose the core end surface of the core, and is opposed to the core end surface exposed on the reflection surface. The mounting substrate is provided with a mounting recess into which an optical element mounted on the mounting substrate is inserted.

  In the optical module of the present invention, the optical waveguide reflects light in a predetermined direction on the reflection surface with the end surface of the core exposed, so that light enters the optical path from a direction substantially perpendicular to the direction in which the core extends. Emitted.

  As a result, the waveguide portion of the optical waveguide is a light incident / exit surface that faces the reflecting surface, and the mounting recess formed on the support substrate that supports the waveguide portion enters / exits the position facing the core end surface. The surface is exposed.

  Therefore, an optical element is mounted in the mounting recess of the optical waveguide by mounting the surface type optical element on the flat mounting substrate, aligning the mounting recess with the optical element, and mounting the optical waveguide on the mounting substrate. Thus, the optical element is optically coupled to the core through a reflecting surface for converting the optical path.

  The optical waveguide manufacturing method of the present invention includes a step of opening a predetermined position of a support substrate by etching to form a mounting recess, and a core layer constituting a core through which light is propagated on one surface of the support substrate; A step of forming a waveguide part integrally with the support substrate by laminating a clad layer that constitutes a clad covering the core, and a core end face of the core is exposed to the waveguide part on the mounting concave part facing the mounting concave part. And a step of forming a reflecting surface inclined at a predetermined angle.

  In the method of manufacturing an optical waveguide according to the present invention, a core layer and a core constituting a core through which light is propagated are formed on one surface of the support substrate after opening a predetermined portion of the support substrate by etching to form a mounting recess. A clad layer constituting a clad covering the substrate is laminated, and a waveguide portion is formed integrally with the support substrate. Alternatively, the waveguide layer is formed integrally with the support substrate by laminating the core layer that constitutes the core through which light is propagated and the clad layer that constitutes the cladding that covers the core on one surface of the support substrate, and then supports A mounting recess is formed by opening a predetermined position on the other surface of the substrate by etching.

  Then, the core end surface of the core is exposed in the waveguide portion supported by the support substrate so as to face the mounting recess, and a reflection surface inclined at a predetermined angle is formed.

  According to the optical waveguide of the present invention, a reflection surface for converting the optical path and a mounting recess for mounting an optical element optically coupled to the core through the reflection surface can be provided. Optical coupling with the optical element can be realized with a simple configuration.

  According to the optical module of the present invention, by providing such an optical waveguide, a planar optical element and an optical waveguide can be mounted on a flat substrate, and the optical element and the optical waveguide can be optically coupled. Accordingly, a general electric circuit board can be used for mounting the optical element and the optical waveguide, and the cost can be reduced.

  According to the optical waveguide manufacturing method of the present invention, the waveguide portion is supported by the support substrate, and the reflection surface for converting the optical path is formed on the waveguide portion, and optically coupled to the core via the reflection surface. A mounting recess for mounting the optical element to be mounted can be formed on the support substrate, and a highly accurate optical waveguide can be provided.

  Therefore, according to the present invention, an optical module with high accuracy and low cost can be realized.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an optical waveguide, an optical module, and an optical waveguide manufacturing method of the present invention will be described with reference to the drawings.

<Configuration Example of Optical Waveguide and Optical Module of First Embodiment>
1 and 2 are configuration diagrams illustrating an example of an optical module including the optical waveguide according to the first embodiment. FIG. 1 is a plan view of the optical module 1A according to the first embodiment, and FIG. a) is an AA cross-sectional view of the optical module 1A shown in FIG. 1, and FIG. 2B is a BB cross-sectional view of the optical module 1A shown in FIG.

  The optical module 1A of the first embodiment includes an optical waveguide 2A of the first embodiment, a surface emitting semiconductor laser 3A and a photodiode 4 optically coupled to the optical waveguide 2A, and an optical waveguide 2A. And a mounting substrate 5 on which the surface emitting semiconductor laser 3A and the photodiode 4 are mounted.

  The optical waveguide 2A includes a waveguide portion 22A having a core 20 and a clad 21 through which light is propagated, and a support substrate 23A that supports the waveguide portion 22A. A manufacturing process of the waveguide portion 22A and the support substrate 23A Thus, the waveguide portion 22A and the support substrate 23A are integrally formed.

  In the waveguide section 22 </ b> A, one or a plurality of cores 20 are arranged in a predetermined pattern on an underclad 21 a constituting the clad 21, and the core 20 on the underclad 21 a constitutes an overclad 21 b constituting the clad 21. It is a buried type waveguide covered with.

  The waveguide portion 22A is made of, for example, a quartz-based material, and is configured so that the refractive index of the core 20 is slightly larger than the refractive indexes of the underclad 21a and the overclad 21b. It is confined to 20 and propagated.

  In this example, the waveguide portion 22 </ b> A includes two linear cores 20 arranged in parallel, and includes a reflecting surface 24 by inclining one end surface along the direction in which the core 20 extends. The reflection surface 24 has an inclination of about 45 degrees with respect to the waveguide portion 22A, and the core end surface 20a of each core 20 is exposed on the same surface.

  Thereby, in the waveguide portion 22A, the lower surface facing the reflection surface 24 becomes the light incident / exit surface 25A, and the light incident on the incident / exit surface 25A from the substantially vertical direction facing the core end surface 20a of the core 20 The light is totally reflected by the reflecting surface 24 serving as a boundary with the air and the optical path is bent by approximately 90 degrees, and enters the core 20. The light propagating through the core 20 toward the reflecting surface 24 is totally reflected by the reflecting surface 24, the optical path is bent by approximately 90 degrees, and is emitted from the incident / exiting surface 25A in a substantially vertical direction.

  For example, an optical fiber (not shown) is connected to the other end surface of the waveguide portion 22A opposite to the reflecting surface 24. The optical fiber may be configured to abut against and connect to the end face of the waveguide portion 22A, or when a fiber guide groove is formed in the waveguide portion 22A and the optical fiber is inserted into the fiber guide groove and bonded and fixed. It may be aligned and optically coupled.

  The support substrate 23A has a size that supports the entire lower surface of the waveguide portion 22A, and includes mounting recesses 26A at positions facing each core end surface 20a exposed on the reflection surface 24 of the waveguide portion 22A. Each mounting recess 26A is formed by opening the end portion of the support substrate 23A in a concave shape, and is located below the reflecting surface 24 at a position facing each core end surface 20a as shown in FIG. 2 (a). Is formed.

  On the other hand, the support substrate 23A includes the waveguide support portions 27 at both ends of the mounting recess 26A. The waveguide support portion 27 is configured by leaving support substrates 23A on both sides of the mounting recess 26A, and the lower side of the reflection surface 24 other than the position where the mounting recess 26A is formed is as shown in FIG. It is supported by the support substrate 23A.

  The support substrate 23A is made of, for example, silicon, and the mounting recess 26A is manufactured by anisotropic etching. Further, the waveguide portion 22A is manufactured on the support substrate 23A in a wafer state by a predetermined process, and the support substrate 23A having the mounting recess 26A and the waveguide portion 22A having the reflection surface 24 are integrally formed. Further, an alignment marker 28 is formed on the upper surface of the support substrate 23A so that it can be seen through the waveguide portion 22A.

  A surface-emitting type semiconductor laser (VCSEL) 3A is an example of an optical element, converts an input electric signal into an optical signal, and emits it in a direction perpendicular to the substrate. The photodiode 4 is an example of an optical element, and converts an input optical signal into an electric signal.

  The mounting substrate 5 includes an electrical wiring 50a having a pad (not shown) on which the surface emitting semiconductor laser 3A is mounted, a bonding pad 30 formed on the upper surface of the surface emitting semiconductor laser 3A, and a conductive wire 52. The electrical wiring 50 b to be connected, the electrical wiring 51 a having a pad (not shown) on which the photodiode 4 is mounted, and the bonding pad 40 formed on the upper surface of the photodiode 4 are connected via the conductive wire 52. Electrical wiring 51b and the like are provided.

  The mounting board 5 is a general electric circuit board made of FR4 (Flame Retardant Type 4: printed circuit board material made of a composite material of glass fiber and epoxy resin), ceramics, etc., and the electric wirings 50a and 50b and the electric wiring 51a. , 51b can be constituted by microstrip lines.

  The mounting substrate 5 is mounted with solder or the like by aligning the surface emitting semiconductor laser 3A with a pad (not shown) of the electric wiring 50a. Further, the photodiode 4 is aligned with a pad (not shown) of the electric wiring 51a and mounted by solder or the like.

  Further, the mounting substrate 5 is aligned with the surface emitting semiconductor laser 3A and the photodiode 4, and the optical waveguide 2A is mounted by adhesion or the like.

  That is, when the optical waveguide 2A is placed at a predetermined position of the mounting substrate 5 on which the surface emitting semiconductor laser 3A and the photodiode 4 are mounted, the surface emitting semiconductor is placed in one mounting recess 26A formed on the support substrate 23A. While the laser 3A enters, the photodiode 4 enters the other mounting recess 26A.

  Then, one core end surface 20a exposed on the reflecting surface 24 of the waveguide portion 22A is aligned with the light emitting portion 31 of the surface emitting semiconductor laser 3A, and the other core end surface 20b exposed on the reflecting surface 24 is It is aligned with the light receiving portion 41 of the photodiode 4.

<Operation Example of Optical Module of First Embodiment>
Next, an operation example of the optical module 1A according to the first embodiment will be described with reference to FIGS.

  In the optical module 1A, an electric signal is input to the surface emitting semiconductor laser 3A through the electric wirings 50a and 50b, and the surface emitting semiconductor laser 3A converts the input electric signal into an optical signal and emits it.

  The output optical signal emitted from the surface emitting semiconductor laser 3A enters the incident / exit surface 25A of the waveguide portion 22A from a substantially vertical direction and is totally reflected by the core end surface 20a exposed to the reflecting surface 24, whereby the optical path is substantially reduced. It bends 90 degrees, enters one core 20, and propagates through the core 20. The light propagated through the core 20 is propagated through, for example, an optical fiber (not shown) and received by the opposing device.

  An input optical signal transmitted from a counter device (not shown) and propagated through the optical fiber is incident on the other core 20 and propagates toward the reflecting surface 24. The light propagating through the core 20 is totally reflected by the core end face 20a exposed on the reflecting surface 24, the optical path is bent by approximately 90 degrees, is emitted from the incident / exiting surface 25A in a substantially vertical direction, and is received by the photodiode 4. . The input optical signal received by the photodiode 4 is converted into an electric signal and output through the electric wirings 51a and 51b.

<Example of Manufacturing Process of Optical Waveguide of First Embodiment>
3 and 4 are process explanatory views showing an example of a method of manufacturing the optical waveguide 2A according to the first embodiment. Next, a manufacturing process of the optical waveguide 2A according to the first embodiment will be described.

  As a material constituting the support substrate 23A, a silicon substrate 60 (crystal orientation <100>) in a wafer state having thermal oxide films 60a on both front and back surfaces is used. First, in step 1 shown in FIG. 3A, a photoresist 61 having a predetermined opening 61a on the surface of the silicon substrate 60 is formed so that the position where the mounting recess 26A described in FIGS. Is patterned.

  Thereafter, the thermal oxide film 60a in the opening portion of the photoresist 61 is removed by ion etching (RIE: Reactive Ion Etching) using a fluorine-based gas. The photoresist 61 used as a mask is removed by ashing with oxygen plasma.

  Next, in step 2 shown in FIG. 3B, the silicon substrate 60 from which the thermal oxide film 60a at the position where the mounting recess is formed is removed from, for example, a KOH (potassium hydroxide) aqueous solution 70 having a temperature of 70 ° C. and a concentration of 20 wt%. Then, the silicon substrate 60 at the position where the mounting recess is formed is etched until the thermal oxide film 60a on the back surface side is exposed to form the mounting recess forming portion 62.

  Next, in step 3 shown in FIG. 3C, the alignment marker 28 is formed at a predetermined position on the surface opposite to the mounting recess forming portion 62 which is the upper surface of the support substrate 23A. In this example, an Al (aluminum) film is used as the alignment marker 28, and the alignment marker 28 having a predetermined shape is formed of a metal film by a lift-off process using a photoresist for pattern formation. As a method for forming the metal film, plating, sputtering, or the like may be used. Also, pattern formation may be performed by etching.

Next, in step 4 shown in FIG. 4A, an under-cladding layer 63 that forms the under-cladding 21a of the waveguide portion 22A is formed. In this example, the under clad layer 63 is formed by forming a SiO ₂ (quartz) film by plasma CVD (chemical vapor deposition).

Next, in step 5 shown in FIG. 4B, a core layer 64 to be the core 20 of the waveguide portion 22A is formed. In this example, the core layer 64 is formed by forming a SiO ₂ film doped with Ge (germanium) and having a refractive index higher than that of the under cladding layer 63 by plasma CVD. Thereafter, a desired core pattern was formed by etching. A metal pattern was used as an etching mask, and etching was performed by fluorine-based RIE.

Next, in step 6 shown in FIG. 4C, an over clad layer 65 to be the over clad 21b of the waveguide portion 22A is formed. In this example, the over clad layer 65 is formed by forming a SiO ₂ film having the same refractive index as that of the under clad layer 63 by plasma CVD.

  Finally, in step 7 shown in FIG. 4D, the center of the mounting recess forming part 62 is diced with a dicing blade 71 having a cutting edge of 45 degrees and a cutting edge of 45 degrees, and the angle is 45 degrees. The mounting recess 26 </ b> A was formed by cutting the formation position of the mounting recess forming portion 62. Furthermore, the optical waveguide 2A in which the support substrate 23A and the waveguide portion 22A are integrally formed is obtained by dicing the sides other than the side forming the reflective surface 24 with a dicing blade (not shown) having a cut surface of 90 degrees. It was made into a chip with the size of the mounting form.

<Example of Manufacturing Process of Optical Module of First Embodiment>
Next, a manufacturing process of the optical module 1A according to the first embodiment including the optical waveguide 2A described above will be described with reference to each drawing.

  First, the position of an alignment marker (not shown) formed on the mounting substrate 5 and the position of an alignment marker (not shown) formed on the upper surface of the surface emitting semiconductor laser 3A and the upper surface of the photodiode 4 are specified by image recognition. The positions of the surface-emitting type semiconductor laser 3A and the photodiode 4 are adjusted so that the relative position of the alignment marker becomes a predetermined value.

  Then, the aligned surface emitting semiconductor laser 3A is bonded to a pad (not shown) of the electric wiring 50a on the mounting substrate 5, and the aligned photodiode 4 is bonded to the electric wiring 51a on the mounting substrate 5. Bonding is performed on a pad (not shown).

  Next, the bonding pads 30 of the surface-emitting type semiconductor laser 3A and the electrical wiring 50b of the mounting substrate 5 are connected by wire bonding using the conductive wires 52, and the bonding pads 40 of the photodiode 4 and the mounting substrate 5 are connected. The electrical wiring 51 b is connected by conducting wire bonding with the conductive wire 52.

  Next, the positions of the alignment marker 28 of the optical waveguide 2A and the alignment marker (not shown) formed on the upper surface of the surface emitting semiconductor laser 3A are specified by image recognition, and the relative positions of the alignment markers are determined. The position of the optical waveguide 2A is adjusted such that the optical waveguide 2A is adhered and fixed on the mounting substrate 5 so as to have the above value.

  In the optical module 1A, in order to best align the positions of the surface emitting semiconductor laser 3A and the optical waveguide 2A, the position of the surface emitting semiconductor laser 3A is used as a reference. The alignment marker is used when mounting the optical waveguide 2A. On the other hand, an alignment marker (not shown) formed on the photodiode 4 or an alignment marker (not shown) formed on the mounting substrate 5 may be used for the alignment of the optical waveguide 2A.

  In this example, the marker is used for the alignment of the optical waveguide 2A. However, the pattern of the light emitting portion 31 of the surface emitting semiconductor laser 3A can be used instead of the alignment marker on the mounting substrate 5 side, The core end surface 20a of the core 20 exposed at 24 and the edge portion of the reflecting surface 24 may be used as an alignment marker on the optical waveguide 2A side.

  Furthermore, the surface emitting semiconductor laser 3A and the photodiode 4 may be actually operated, and alignment may be performed by active alignment.

<Configuration example of optical waveguide and optical module according to second embodiment>
5 and 6 are configuration diagrams showing an example of an optical module including the optical waveguide according to the second embodiment. FIG. 5 is a plan view of the optical module 1B according to the second embodiment, and FIG. FIG. 6A is a cross-sectional view of the optical module 1B shown in FIG. 5 taken along the line CC, and FIG. 6B is a cross-sectional view of the optical module 1B shown in FIG.

  The optical module 1B according to the second embodiment includes an optical waveguide 2B according to the second embodiment, a surface emitting semiconductor laser array 3B optically coupled to the optical waveguide 2B, an optical waveguide 2B, and a surface emitting type. And a mounting substrate 5 on which the semiconductor laser array 3B is mounted.

  The optical waveguide 2B includes a waveguide portion 22B having a core 20 and a clad 21 through which light is propagated, and a support substrate 23B that supports the waveguide portion 22B, and a manufacturing process of the waveguide portion 22B and the support substrate 23B. Thus, the waveguide portion 22B and the support substrate 23B are integrally formed.

  In this example, in the waveguide portion 22B, four linear cores 20 are arranged in a parallel pattern on the underclad 21a constituting the clad 21, and the core 20 on the underclad 21a constitutes the clad 21. It is a buried waveguide covered with an overclad 21b.

  The waveguide portion 22B is made of, for example, a polymer waveguide material. The waveguide portion 22B is configured so that the refractive index of the core 20 is slightly higher than the refractive indexes of the underclad 21a and the overclad 21b. , It is confined in the core 20 and propagated.

  The waveguide portion 22B includes a reflecting surface 24 by inclining one end surface along the direction in which the core 20 extends. The reflecting surface 24 has an inclination of about 45 degrees with respect to the waveguide portion 22B, and the core end surface 20a of each core 20 is exposed on the same surface.

  As a result, in the waveguide portion 22B, the lower surface facing the reflecting surface 24 becomes the light incident surface 25B, and the light incident on the incident surface 25B from the substantially vertical direction facing the core end surface 20a of the core 20 is air and The light is totally reflected by the reflecting surface 24 serving as the boundary of the light and the optical path is bent by approximately 90 degrees and enters the core 20.

  The waveguide portion 22B includes an antireflection film 29 on the incident surface 25B. The antireflection film 29 prevents reflection of light incident on the waveguide portion 22B from the incident surface 25B on the incident surface 25B and reduces crosstalk.

  For example, an optical fiber (not shown) is connected to the other end surface of the waveguide portion 22B opposite to the reflecting surface 24. The optical fiber may be configured to abut against and connect to the end face of the waveguide portion 22B, or when a fiber guide groove is formed in the waveguide portion 22B and the optical fiber is inserted into the fiber guide groove and bonded and fixed. It may be aligned and optically coupled.

  The support substrate 23B has a size that supports the entire lower surface of the waveguide portion 22B, and includes a mounting recess 26B at the entire position facing each core end surface 20a exposed on the reflection surface 24 of the waveguide portion 22B. The mounting recess 26B is configured by opening the end of the support substrate 23B in a concave shape, and a space is provided below the reflecting surface 24 at a position facing each core end surface 20a as shown in FIG. 6A. It is formed.

  On the other hand, the support substrate 23B includes the waveguide support portions 27 at both ends of the mounting recess 26B. The waveguide support portion 27 is configured by leaving support substrates 23B on both sides of the mounting recess 26B, and the lower side of the reflection surface 24 other than the position where the mounting recess 26B is formed is as shown in FIG. 6B. It is supported by the support substrate 23B.

  The support substrate 23B is made of, for example, silicon, and the mounting recess 26B is manufactured by anisotropic etching. The waveguide portion 22B is manufactured on the support substrate 23B in a wafer state by a predetermined process, and the support substrate 23B having the mounting recess 26B and the waveguide portion 22B having the reflection surface 24 and the antireflection film 29 are integrated. Configured.

  The surface emitting semiconductor laser array 3B is an example of an optical element. In this example, the surface emitting semiconductor laser array 3B is a four-channel VCSEL array in which, for example, four surface emitting semiconductor laser elements are arranged at equal intervals at a predetermined pitch. The signal is converted into an optical signal and emitted in a direction perpendicular to the substrate.

  The mounting board 5 is a general electric circuit board made of FR4, ceramic, or the like, and is connected via bonding pads 30 and conductive wires 52 of each laser element formed on the upper surface of the surface emitting semiconductor laser array 3B. Electrical wiring 53 to be connected is provided.

  The surface-emitting type semiconductor laser array 3B is mounted on the mounting substrate 5 in a predetermined position. The mounting substrate 5 is aligned with the surface emitting semiconductor laser array 3B, and the optical waveguide 2B is mounted by bonding or the like.

  That is, when the optical waveguide 2B is placed at a predetermined position of the mounting substrate 5 on which the surface emitting semiconductor laser array 3B is mounted, the surface emitting semiconductor laser array 3B enters the mounting recess 26B formed in the support substrate 23B. .

  Then, each core end surface 20a exposed on the reflection surface 24 of the waveguide portion 22B is aligned with each light emitting portion 31 of the surface emitting semiconductor laser array 3B.

<Operation Example of Optical Module of Second Embodiment>
Next, an operation example of the optical module 1B according to the second embodiment will be described with reference to FIGS.

  In the optical module 1B, an electrical signal is input to each laser element of the surface emitting semiconductor laser array 3B through the electrical wiring 53, and the surface emitting semiconductor laser array 3B converts the input electrical signal into an optical signal. Exit.

  The output optical signal emitted from the surface emitting semiconductor laser array 3B is incident on the incident surface 25B of the waveguide portion 22B from a substantially vertical direction, and is totally reflected by the core end surface 20a exposed on the reflecting surface 24, whereby the optical path is substantially reduced. It bends 90 degrees, enters the core 20, and propagates through the core 20. The light propagated through the core 20 is propagated through, for example, an optical fiber (not shown) and received by the opposing device.

  Since an antireflection film 29 is formed on the incident surface 25B of the optical waveguide 2B on which the light emitted from the surface emitting semiconductor laser array 3B is incident, return light to the surface emitting semiconductor laser array 3B is suppressed. The output is very stable.

<Example of Manufacturing Process of Optical Waveguide of Second Embodiment>
7 and 8 are process explanatory views showing an example of a method of manufacturing the optical waveguide 2B according to the second embodiment. Next, a manufacturing process of the optical waveguide 2B according to the second embodiment will be described.

  As a material constituting the support substrate 23B, a silicon substrate 60 (crystal orientation <100>) in a wafer state having thermal oxide films 60a on both front and back surfaces is used. First, in step 1 shown in FIG. 7A, an under clad layer 63 to be the under clad 21 a of the waveguide portion 22 </ b> B described with reference to FIGS. 5 and 6 is formed on one surface of the silicon substrate 60. In this example, an acrylic polymer resin material is applied onto the silicon substrate 60 by spin coating, and then cured (fired) on a hot plate to form the underclad layer 63.

  Next, in step 2 shown in FIG. 7B, a core layer 64 to be the core 20 of the waveguide portion 22B is formed. In this example, an acrylic polymer resin material having photosensitivity and a higher refractive index than the acrylic resin material used for forming the under cladding layer 63 is formed on the under cladding layer 63 formed on the silicon substrate 60 by spin coating. Filmed. Thereafter, pre-baking was performed, and UV (ultraviolet) exposure and development were performed through a photomask on which the pattern of the core 20 was formed, thereby forming a desired core pattern as shown in FIG. Finally, post-baking was performed, and the core layer 64 was completely cured to form the core 20.

  Next, in step 3 shown in FIG. 7C, an over clad layer 65 to be the over clad 21b of the waveguide portion 22B is formed. In this example, the same acrylic resin material used for the formation of the under cladding layer 63 is applied by spin coating on the under cladding layer 63 and the core layer 64 formed on the silicon substrate 60, and then cured on a hot plate. Thus, the over clad layer 65 was formed, and the waveguide portion 22B in which the under clad layer 63, the core layer 64, and the over clad layer 65 were laminated on the silicon substrate 60 was formed.

  Next, in step 4 shown in FIG. 7D, an alkali resistant film 66 is formed on the surface of the waveguide portion 22B. In this example, a polyimide resin having high alkali resistance was formed on the over clad layer 65 by spin coating. As the alkali resistant film 66, a metal film having alkali resistance may be formed by vapor deposition or the like.

  Next, in step 5 shown in FIG. 8A, a predetermined opening 61a is formed on the surface opposite to the surface on which the waveguide portion 22B of the silicon substrate 60 is manufactured so that the position for manufacturing the mounting recess 26B is opened. A photoresist 61 having a pattern is patterned.

  Thereafter, the thermal oxide film 60a in the opening portion of the photoresist 61 is removed by ion etching (RIE) using a fluorine-based gas. The photoresist 61 used as a mask is removed by ashing with oxygen plasma.

  Next, in step 6 shown in FIG. 8B, the silicon substrate 60 from which the thermal oxide film 60a at the mounting recess formation position has been removed is placed in, for example, a KOH aqueous solution 70 having a temperature of 70 ° C. and a concentration of 20 wt% for mounting. Etching is performed on the silicon substrate 60 at the position where the recess is formed until the thermal oxide film 60a on the back surface side is exposed, and a mounting recess forming portion 62 is formed. Here, the surface of the waveguide portion 22B manufactured on the silicon substrate 60 is covered with the alkali-resistant film 66, thereby preventing the waveguide portion 22B from being eroded during the etching process.

  Next, in step 7 shown in FIG. 8C, the antireflection film 29 is formed on the waveguide portion 22 </ b> B exposed to the mounting recess forming portion 62. In this example, a multilayer film is formed on the surface of the silicon substrate 60 opposite to the surface on which the waveguide 22B is manufactured, thereby forming the antireflection film 29.

  Finally, in step 8 shown in FIG. 8D, the center of the mounting recess forming part 62 is diced with a dicing blade 71 having a cutting edge of 45 degrees with a cutting edge of 45 degrees and an angle of 45 degrees. The mounting recess 26 </ b> B was formed by cutting the formation position of the mounting recess forming portion 62. Further, the optical waveguide 2B in which the support substrate 23B and the waveguide portion 22B are integrally formed is obtained by dicing the sides other than the side forming the reflection surface 24 with a dicing blade (not shown) having a cut surface of 90 degrees. It was made into a chip with the size of the mounting form.

<Example of Manufacturing Process of Optical Module of Second Embodiment>
Next, the manufacturing process of the optical module 1B according to the second embodiment including the optical waveguide 2B described above will be described with reference to each drawing.

  First, an alignment marker (not shown) formed on the mounting substrate 5 and the light emitting portion 31 of the surface emitting semiconductor laser array 3B are specified by image recognition, and the relative position of each is determined to be a predetermined value. The position of the light emitting semiconductor laser array 3B is adjusted, and the aligned surface emitting semiconductor laser array 3B is bonded onto the mounting substrate 5.

  Next, the bonding pads 30 of the surface emitting semiconductor laser array 3 </ b> B and the electrical wiring 53 of the mounting substrate 5 are connected by conducting wire bonding with the conductive wires 52.

  Next, the core end surface 20a of the core 20 exposed on the reflection surface 24 of the optical waveguide 2B, the edge portion of the reflection surface 24, and the light emitting portion 31 of the surface emitting semiconductor laser array 3B are specified by image recognition, and the relative The position of the optical waveguide 2B is adjusted so that the position becomes the determined value, and the optical waveguide 2B is bonded and fixed on the mounting substrate 5.

<Examples of effects of each embodiment>
The optical module of each embodiment couples a light emitting element or a light receiving element, an optical fiber, a lens, or the like via an optical waveguide. The optical waveguide includes a 45-degree reflective surface with the core end face exposed, and is configured so that light enters and exits from a substantially vertical direction, so that a surface-emitting semiconductor laser, It can be combined with a surface optical device such as a surface emitting semiconductor laser array.

  In order to directly mount the optical element on the substrate, a space for the optical element needs to be formed on the lower surface side facing the reflecting surface of the optical waveguide. Therefore, the optical waveguide supports the film-like waveguide portion with a support substrate having a predetermined height, and forms a mounting recess in the support substrate, so that the space necessary for mounting the optical element can be reduced. Secured on the waveguide side.

  As a result, the optical element may be mounted on a flat substrate, and a general electric circuit substrate can be used as the mounting substrate without using a substrate having a concave configuration or a submount. Therefore, it is advantageous for cost reduction.

  Further, since a general electric circuit board can be used, a microstrip line can be formed as an electric wiring, and high-frequency characteristics can be improved.

  Furthermore, in the optical module having such a configuration, if the gap between the light incident / exit surface constituted by the lower surface of the waveguide portion exposed in the mounting recess and the optical element is wide, the light coupling efficiency decreases. It is necessary to strictly control the gap with the waveguide portion.

  For this reason, by supporting the waveguide portion with a support substrate such as a silicon substrate, it becomes easy to control the height of the waveguide portion, and the gap between the optical element and the waveguide portion is precisely controlled to achieve good light. Bonds can be obtained.

  In addition, the optical waveguide of this embodiment can be manufactured in a batch by the wafer process, and the waveguide portion is formed by film formation on the support substrate. Therefore, the accuracy of the core shape and the angle of the reflection surface and the waveguide portion The height accuracy is improved, and a high-precision optical waveguide can be manufactured at low cost. Furthermore, since the film-like waveguide portion is always supported by the support substrate in the manufacturing process and the mounting process, handling is improved and manufacturing yield is improved.

  Further, since the light incident / exit surface is the lower surface of the waveguide portion, as described in the second embodiment, an antireflection film and a wavelength filter can be easily formed on the waveguide portion by a wafer process, and a desired Functions can be added at low cost.

  Furthermore, by using a silicon substrate for the support substrate that supports the waveguide portion, a highly accurate mounting recess can be easily formed by anisotropic etching, so that the mounting recess remains with the formation of the waveguide support portion. The waveguide support portion can be formed between adjacent mounting recesses. Note that the supporting substrate may be a substrate made of another material that can be easily etched instead of silicon.

  Then, by providing a waveguide support part on both sides of the mounting recess formed in the optical waveguide for mounting the optical element so that the waveguide part can be supported, in the waveguide part, the light with the optical element can be supported. Both sides of the portion that is free for coupling are supported by the support substrate.

  As a result, the optical waveguide has fewer free portions at the end on the side where the reflecting surface is formed in the waveguide portion. Therefore, the waveguide portion expands and contracts due to heat and the waveguide portion warps due to long-term use. The increase in coupling loss due to such deformation can be reduced, and long-term reliability can be improved.

  From the above, by using an optical waveguide in which the waveguide portion on which the reflecting surface is formed and the support substrate are integrally formed, and the mounting recess serving as a relief portion when mounting the optical element is formed on the support substrate, 45 is used. It is possible to easily realize a configuration for optically coupling an optical waveguide having a reflective surface with a planar optical element such as a VCSEL, and to realize a low-cost, high-functional and highly reliable optical module. .

  The present invention is applied to an optical communication module between boards or chips of an electronic device, a connector of a communication cable using an optical fiber, and the like.

It is a block diagram which shows an example of the optical module provided with the optical waveguide of 1st Embodiment. It is a block diagram which shows an example of the optical module provided with the optical waveguide of 1st Embodiment. It is process explanatory drawing which shows an example of the manufacturing method of the optical waveguide of 1st Embodiment. It is process explanatory drawing which shows an example of the manufacturing method of the optical waveguide of 1st Embodiment. It is a block diagram which shows an example of the optical module provided with the optical waveguide of 2nd Embodiment. It is a block diagram which shows an example of the optical module provided with the optical waveguide of 2nd Embodiment. It is process explanatory drawing which shows an example of the manufacturing method of the optical waveguide of 2nd Embodiment. It is process explanatory drawing which shows an example of the manufacturing method of the optical waveguide of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A, 1B ... Optical module, 2A, 2B ... Optical waveguide, 20 ... Core, 20a ... Core end surface, 21 ... Cladding, 22A, 22B ... Waveguide part, 23A, 23B ... support substrate, 24 ... reflective surface, 25A ... incident / exit surface, 25B ... incident surface, 26A, 26B ... mounting recess, 27 ... waveguide support, 28 ... Alignment marker, 29 ... Antireflection film, 3A ... Surface emitting semiconductor laser, 3B ... Surface emitting semiconductor laser array, 4 ... Photodiode, 5 ... Mounting substrate

Claims (13)

In an optical waveguide comprising a waveguide portion having a core and a cladding, and a support substrate for supporting the waveguide portion,
The waveguide portion includes a reflective surface that exposes the core end surface of the core by inclining one end surface along a direction in which the core extends to a predetermined angle.
The optical waveguide, wherein the support substrate includes a mounting recess that opens at a position facing the core end surface exposed on the reflection surface. The optical waveguide according to claim 1, wherein the waveguide portion is formed integrally with the support substrate. The optical waveguide according to claim 1, wherein the core and the clad of the waveguide portion are formed of a polymer material having a predetermined refractive index difference. The optical waveguide according to claim 1, wherein the support substrate is made of silicon, and the mounting recess is manufactured by anisotropic etching. An optical waveguide in which a waveguide portion having a core and a clad is supported by a support substrate;
An optical element coupled to the core;
A mounting substrate on which the optical waveguide and the optical element are mounted;
The optical waveguide includes a reflective surface that exposes the core end surface of the core by inclining one end surface of the waveguide portion along a direction in which the core extends at a predetermined angle,
An optical module, comprising: a mounting recess that opens the support substrate at a position facing the core end surface exposed on the reflection surface and into which the optical element mounted on the mounting substrate is placed. 6. The optical module according to claim 5, wherein the optical waveguide includes a waveguide support portion that disposes the support substrate on both sides of the mounting recess and supports the reflection surface of the waveguide portion. The optical module according to claim 5, further comprising an antireflection film or a wavelength filter on a lower surface of the waveguide portion exposed in the mounting recess. Forming a mounting recess by opening a predetermined position of the support substrate by etching;
Laminating a core layer constituting a core through which light is propagated and a clad layer constituting a clad covering the core on one surface of the support substrate, and forming a waveguide portion integrally with the support substrate;
A step of forming a reflection surface inclined at a predetermined angle, wherein the core end surface of the core is exposed to face the mounting recess, and the waveguide portion on the mounting recess is formed. Production method. After the step of opening a predetermined position of the support substrate by etching and forming a mounting recess,
A core layer that constitutes a core through which light is propagated and a clad layer that constitutes a clad that covers the core are laminated on one surface of the support substrate on which the mounting recess is formed, and is guided integrally with the support substrate. The method for manufacturing an optical waveguide according to claim 8, wherein a step of forming a waveguide portion is performed. After the step of laminating the core layer constituting the core through which light is propagated and the clad layer constituting the clad covering the core on one surface of the support substrate to form the waveguide portion integrally with the support substrate ,
9. The method of manufacturing an optical waveguide according to claim 8, wherein a step of forming a mounting recess by opening a predetermined position on the other surface of the support substrate on which the waveguide portion is formed by etching. While forming the mounting recess and the waveguide portion on the support substrate in a wafer state,
9. The method of manufacturing an optical waveguide according to claim 8, wherein the reflecting surface is formed by dicing that cuts the support substrate and the waveguide portion that are integrally formed into a predetermined size. The method of manufacturing an optical waveguide according to claim 8, wherein the waveguide portion is made of a polymer material, and an alkali-resistant film is formed on an upper surface of the waveguide portion. The method of manufacturing an optical waveguide according to claim 8, further comprising a step of forming an antireflection film or a wavelength filter on the lower surface of the waveguide portion exposed in the mounting recess.

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