JP2009008766A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module in which optical axis deviation hardly occurs and which has high adhesion strength. <P>SOLUTION: The optical module includes mount substrates 1, 3 including waveguides at a light emission side and a light reception side and an external waveguide substrate 2 including an external waveguide. The waveguides of the mount substrates 1, 3 include a core part 17 having a first abutment face 17a. The external waveguide of the external waveguide substrate 2 includes a core part 21 including a second abutment face 21a. By the abutment between the first abutment face 17a and the second abutment face 21a, the waveguide of the mount substrates 1, 3 and the external waveguide of the external waveguide substrate 2 are optically coupled. Further, a connection piece 5 is overlaid on the mount substrate 1, and a part thereof is bonded by an adhesive. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical module that transmits or receives an optical signal.

As an optical module for transmitting or receiving optical signals, for example, a polymer optical waveguide film (external waveguide substrate) on which a waveguide having a core (optical waveguide) is formed, and holding an optical element (light emitting element, light receiving element) A submount (mount substrate) is disposed on the upper side of the optical element and bonded with an adhesive so that light emitted from the optical element is coupled to the incident end face of the optical waveguide. (See Patent Document 1).
JP 2006-243467 A

  However, when the polymer optical waveguide film is adhered to the submount as described above, the outer dimensions of the polymer optical waveguide film are accurately formed so that the polymer optical waveguide film and the submount are not displaced from each other. It is necessary to make it difficult to manufacture.

  In addition, the position of the optical waveguide may be shifted with respect to the outer shape of the polymer optical waveguide film. In this case, the position of the optical waveguide is not changed even if the polymer optical waveguide film is disposed at a predetermined position of the submount. As a result, the optical axis shift occurs and the optical coupling efficiency is likely to decrease.

  In addition, since the polymer optical waveguide film is disposed on the optical element, there is a risk of damaging the optical element when disposed or bonded, and there is a risk of contaminating the surface of the optical element.

  Furthermore, since an adhesive is inserted between the polymer optical waveguide film provided with the optical waveguide and the submount holding the optical element, the distance between the optical waveguide and the optical element increases, and the optical coupling efficiency decreases. There is a high risk.

  It is an object of the present invention to provide an optical module that is less likely to cause an optical axis shift and has a high adhesive strength.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical module with little risk of damaging an optical element or fouling the surface during bonding.

  In order to solve the above problems, the present invention provides an optical module comprising a mount substrate on which an optical element is provided, and an external waveguide substrate that is optically coupled to the mount substrate, the mount substrate being Is provided with a waveguide having a core portion that is optically coupled to the optical element, the core portion of the waveguide having a first abutting surface, and the external waveguide substrate being guided by the mount substrate. An external waveguide having a core portion that can be optically coupled to the waveguide is provided, and the core portion of the external waveguide includes a second abutting surface, and the second abutting surface and the first abutting surface abut each other. By being combined, the waveguide and the external waveguide are optically coupled, and a connection piece is provided on either one of the mount substrate and the external waveguide substrate. The above When the first butted surface and the second butted surface are butted, the other one of the mount substrate and the external waveguide substrate is overlapped, and the overlapped part or the whole is adhered by an adhesive. An optical module is provided.

  The connection piece is overlapped in the thickness direction on a part of the other external waveguide substrate or the mount substrate, and one of the first butted surface and the second butted surface that are butted against each other, It is preferably formed on an inclined surface inclined in the thickness direction.

  An end of the other external waveguide substrate or the mount substrate is provided with a receiving recess for receiving a part of the end of the one mount substrate or the external waveguide substrate and bonding it with an adhesive. preferable.

  It is preferable that the receiving recess is provided with a groove formed at a predetermined depth from the inner surface of the receiving recess.

  According to the first aspect of the present invention, the first butted surface of the core portion of the waveguide and the second butted surface of the core portion of the external waveguide are butted against each other, thereby optically connecting the waveguide and the external waveguide. Since it couple | bonds, it can carry out, aligning core parts, and can suppress an optical axis shift.

  Further, since the connecting piece is overlapped with a part of the external waveguide substrate or the mount substrate at the time of the butting, and a part or the whole thereof is adhered with an adhesive, it is possible to have an adhesive strength.

  According to the second aspect of the present invention, when the mount substrate and the external waveguide substrate are bonded with an adhesive, an adhesive layer is formed between the mount substrate and the external waveguide substrate, and the core portions of both are thick. Even when the position is displaced in the vertical direction, the light is refracted by the inclined surface of the core portion, and light can be efficiently incident from one core portion to the other core portion, and optical coupling loss can be suppressed.

  According to the third aspect of the present invention, since one end portion is received and bonded by the receiving concave portion provided at the other end portion of the mount substrate and the external waveguide substrate, the bonding area is widened and bonded. Strength can be increased. In addition, for example, when the external waveguide substrate is bent, stress is hardly applied in the vicinity of the end portions of the mount substrate and the external waveguide substrate, and it is difficult to break from the boundary portion between the end portions.

  According to invention of Claim 4, while being able to make an adhesive agent go around to a receiving recessed part easily with a groove | channel, adhesive strength can be raised by an anchor effect.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view of an optical module according to the first embodiment of the present invention. This optical module includes a light-emitting side mount substrate 1, a light-receiving side mount substrate 3, and an external waveguide substrate 2 in which these mount substrates 1 and 3 are coupled so as to be optically connectable. In the following description, the up and down direction in FIG. 1 is referred to as the up and down direction, the direction orthogonal to the paper surface is referred to as the left and right direction, the left side in FIG.

  The light emitting side mount substrate 1 has a rectangular shape extending in the front-rear direction and has a thickness of about 200 μm to 2 mm. The overall size of the mount substrate 1 varies depending on the elements and components to be mounted.

  The mount substrate 1 needs to be rigid in order to avoid the influence of heat during mounting and the influence of stress due to the use environment. In the case of optical transmission, since light transmission efficiency from the light emitting element to the light receiving element is required, it is necessary to mount the optical element with high accuracy and to suppress position fluctuation during use as much as possible. For this reason, a silicon substrate is employed as the mount substrate 1.

  In addition, the mount substrate 1 is preferably made of a material having a linear expansion coefficient close to that of a light emitting element 12a described later. In addition to silicon, the mount substrate 1 is made of a compound semiconductor such as GaAs of the same system as the VCSEL material described later. May be. Alternatively, a resin substrate may be used depending on the ceramic substrate and the usage environment.

  On one surface 11 in the thickness direction, which is the upper surface of the mount substrate 1, an IC in which a light emitting element 12a for converting an electric signal into an optical signal and an IC circuit for transmitting the electric signal to the light emitting element 12a are formed. A substrate 13a is mounted.

  In this embodiment, a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting Laser)) that is a semiconductor laser is employed as the light emitting element 12a. The light emitting element 12a may be an LED or the like in addition to the semiconductor laser. However, since there is no directivity, the ratio of light that is optically coupled to the waveguide through a 45 ° mirror surface, which will be described later, is small. In this case, it is advantageous in terms of low price.

  The light emitting element 12a is mounted on the mount substrate 1 by flip chip bonding. In flip chip bonding, the mounting accuracy is higher than that in the case of performing die bonding or wire bonding, and the mounting accuracy of 1 μm or less can be realized by recognizing the alignment mark formed on the chip.

  The IC substrate 13a is a driver IC that drives the VCSEL, and is disposed in the vicinity of the light emitting element 12a. The light emitting element 12a and the IC substrate 13a are connected to a wiring pattern formed on the one surface 11 of the mount substrate 1 with gold bumps (not shown). The IC substrate 13a is mounted on the mount substrate 1 simultaneously with the light emitting element 12a.

  Although not shown, an underfill material is filled between the light emitting element 12a and the mount substrate 1 and between the IC substrate 13a and the mount substrate 1. The underfill material to be filled between the light emitting element 12a and the mount substrate 1 is required to be transparent with respect to the light emission wavelength of the light emitting element 12a, and the VCSEL is required to have a certain degree of elasticity because its characteristics change due to stress. Therefore, for example, a silicone resin or an epoxy resin is preferable. In addition, as an underfill material filled between the IC substrate 13a and the mount substrate 1, for example, an epoxy-based material can be employed from the viewpoint of mounting strength.

  In addition, a mirror portion 15 for bending the optical path by 90 ° is formed on the mount substrate 1 at a position directly below the light emitting element 12a. The mirror portion 15 can be formed by evaporating gold or aluminum on a 45 ° inclined surface formed by etching the mount substrate 1. The 45 ° inclined surface can be formed, for example, by anisotropic etching with a potassium hydroxide solution.

  The mount substrate 1 is provided with a waveguide 16 that is optically coupled to the light emitting element 12a. The waveguide 16 extends rearward from the mirror portion 15 and extends to the rear end face 10 of the mount substrate 1 as shown in FIGS. 2 (b), 3 (a), and 3 (b). It is being done.

  The waveguide 16 includes a core portion 17 having a substantially square cross section with a high refractive index through which light propagates, and a clad portion 18 having a lower refractive index than that. A waveguide formed on the mount substrate 1 is formed. It is disposed in the groove 16a.

  The left and right surfaces and the lower surface of the core portion 17 are covered with the clad portion 18. The upper surface, which is one surface in the thickness direction of the core portion 17, is formed substantially flush with the upper surface 11 of the mount substrate 1 and is exposed without being covered by the cladding portion 18. In this embodiment, the rear end surface of the core portion 17 in the longitudinal direction is exposed to be substantially flush with the rear end surface 10 of the mount substrate 1. And the rear end surface of this core part 17 comprises the 1st abutting surface 17a abutted with the 2nd abutting surface 21a of the core part 21 of the external waveguide board | substrate 2 mentioned later.

  The sizes of the core portion 17 and the clad portion 18 are determined by giving priority to light efficiency from the distance from the light emitting element 12a to the waveguide 16, the divergence angle of the light emitting element 12a, and the size of the light receiving element described later.

  For example, in a general VCSEL or PD (photodiode) which is a light receiving element used for high-speed transmission of 5 to 10 Gbps or more, the VCSEL has a light emission diameter of 5 to 10 μm and a divergence angle of about 20 °. Since the diameter is about 60 μm, it is preferable that the size of the core portion 17 is 40 μm and the thickness of the cladding portion 18 is 2 to 10 μm.

  In the case of short-distance intra-device data transmission, since the influence of dispersion is small, optical transmission does not require single-mode transmission, and it is advantageous to use a large-sized multimode waveguide that is easy to align. is there. When higher speed is required, a single mode is used, and a VCSEL or PD that is a light source is selected so that it can respond at high speed.

  Further, an upper surface 11 of the mount substrate 1 is provided with an overlapping surface 14 on which a connecting piece 5 of the external waveguide substrate 2 described later is overlapped. The overlapping surface 14 is formed forward from the rear end surface 10 on the upper surface by the length of the connecting piece 5.

  Next, returning to FIG. 1, the mount substrate 3 on the light receiving side will be described. The basic configuration of the light receiving side mount substrate 3 is the same as that of the light emitting side mount substrate 1. However, an IC substrate in which a light receiving element 12b for converting an optical signal into an electric signal and an IC circuit for receiving an electric signal from the light receiving element 12b are formed on the upper surface 31 which is one surface of the light receiving side mounting substrate 3. 13b is different from the light-emitting side mounting substrate 1 in that it is mounted. A PD is employed as the light receiving element 12b, and the IC substrate 13b is an element such as a TIA (Trans-impedance Amplifier) that performs current / voltage conversion.

  Next, the external waveguide substrate 2 will be described based on FIG. 1, FIG. 2 (a), FIG. 3 (a), and FIG. 3 (b). The external waveguide substrate 2 includes external waveguides that can be optically coupled to the core portion 17 of the waveguide 16 of the light emitting side mount substrate 1 and the core portion 17 of the waveguide 16 of the light receiving side mount substrate 3. Yes.

  The external waveguide of the external waveguide substrate 2 includes a core part 21 and a clad part 22. In this embodiment, the entire external waveguide substrate 2 forms an external waveguide composed of a core portion 21 and a cladding portion 22, and is a flexible film having a narrower width than the mount substrate 1, and has a long shape. Consists of things. Further, the thickness of the external waveguide substrate 2 in this embodiment is about several tens of μm to 500 μm, but may be about 1 to 3 mm when flexibility is not required. However, even when the light transmission direction is limited to one direction, it is possible to improve the light efficiency by making the waveguide core part size behind the transmission smaller than that of the front waveguide.

  In addition, the core portion 21 of this embodiment is provided over the entire length so that the axis O2 (shown in FIG. 2A) and the axis of the external waveguide substrate 2 substantially coincide with each other. Further, the front and rear end surfaces of the core portion 21 in the longitudinal direction constitute a second abutting surface 21 a that abuts against the first abutting surface 17 a of the mount substrate 1, 3, respectively, and the distal end surface of the external waveguide substrate 2 It is almost flush with 20 and is exposed.

  The clad portion 22 is formed in a plate shape so as to cover the entire circumference of the core portion 21 as shown in FIG. The core portion 21 and the clad portion 22 constituting the external waveguide of the external waveguide substrate 2 are made of the same material as the core portion 17 and the clad portion 18 of the mount substrate 1. The thickness and width dimensions of the core portion 21 are substantially the same as the thickness and width dimensions of the core portion 17 of the mount substrate 1.

  At both ends in the longitudinal direction of the external waveguide substrate 2, a connecting piece 5 connected to the light emitting side mount substrate 1 and a connecting piece 5 connected to the light receiving side mount substrate are provided. These are symmetrically shaped in the front-rear direction, and only the connecting piece 5 connected to the light emitting side mount substrate 1 will be described below, and the description of the connecting piece 5 connected to the light receiving side mount substrate will be omitted.

  As shown in FIG. 2A, the connecting piece 5 is a plate protruding from the front end face 20 of the external waveguide substrate 2 to the front side with the same width and a predetermined thickness as the external waveguide substrate 2. It consists of a shape. In this embodiment, the connecting piece 5 is formed of the same material as that of the cladding part 22 and is formed integrally with the cladding part 22.

  Further, the lower surface of the connecting piece 5 (represented on the upper side in FIG. 2A) faces the overlapping surface 14 when it is superimposed on the overlapping surface 14 of the light emitting side mounting substrate 1. Thus, an abutting surface 51 that abuts is configured. The contact surface 51 is formed substantially flush with the upper surface of the core portion 21.

  In order to connect the light emitting side mount substrate 1 and the external waveguide substrate 2 configured as described above, as shown in FIG. 3, the first abutting surface 17a of the core portion 17 of the light emitting side mount substrate 1 is connected to the outside. The second abutting surface 21 a of the core portion 21 of the waveguide substrate 2 is abutted. As a result, the core portion 17 of the light emitting side mount substrate 1 and the core portion 21 of the external waveguide substrate 2 are optically coupled.

  At that time, as shown in FIG. 3B, the contact surface 51 of the external waveguide substrate 2 and the upper surface of the core portion 21 of the external waveguide substrate 2 are flush with each other, and the mount substrate 1 is overlaid. Since the surface 14 and the upper surface of the core portion 17 are flush with each other, the positions of the axes O1 and O2 of the core portions 17 and 21 in the vertical direction (thickness direction) match. Therefore, the optical axis can be hardly shifted.

  In this state, an adhesive is put between the overlapping surface 14 of the mount substrate 1 and the contact surface 51 of the external waveguide substrate 2. Thereby, both adhere.

  Further, since the light emitting elements 12a and 12b and the IC substrates 13a and 13b are disposed on the side of the waveguide 16 on the upper surface 11 of the mount substrates 1 and 3, the mount substrates 1 and 3 and the external waveguide substrate 2 are The adhesive used for bonding can be made without any risk of attachment.

  In this embodiment, an epoxy thermosetting material is used as the adhesive. The adhesive is not limited to an epoxy-based thermosetting material, and for example, a photocurable material can be used. However, when a silicon substrate is used as the mount substrate 1, an uncured portion that is not cured may be generated, and therefore, a thermosetting material is preferably used. However, if the external waveguide is made transparent with respect to the wavelength of photocuring, the uncured portion can be prevented.

  In this embodiment, the photoelectric conversion device has been described as an optical module, but the present invention is applicable to coupling between waveguides formed on two base materials. For example, a passive component having no light receiving and emitting element such as an optical splitter and a waveguide film can be applied.

  Next, the optical module of the second embodiment will be described with reference to FIGS. 4 (a) and 4 (b). As shown in FIG. 4A, in the mount substrate 701 on the light emitting side of the optical module of the second embodiment, the first abutting surface 717a of the core portion 717 is on the connecting piece 705 side, that is, one side in the thickness direction. It is formed on an inclined surface that is inclined so that the distance from the core portion 721 of the external waveguide substrate 702 gradually becomes narrower as it goes upward. Others have the same configuration as that of the first embodiment.

  With this configuration, when the mount substrate 701 and the connection piece 705 of the external waveguide substrate 702 are bonded with an adhesive, the overlapping surface 714 of the light-emission mount substrate 701 and the connection piece 705 come into contact with each other. An adhesive layer 700 is formed between the surface 751 and a core portion 717 provided on the mount substrate 701 is disposed at a lower position on the other side in the thickness direction with respect to the core portion 721 of the external waveguide substrate 702. Even in this case, the light from the core portion 717 of the mount substrate 701 is refracted in the first abutting surface 717a obliquely upward in the direction of the core portion 721 of the external waveguide, and the light of the core portion 721 of the external waveguide substrate 702 is reflected. The light enters the second abutting surface 721a. Thereby, optical coupling loss can be suppressed.

  When light is incident on the core portion provided on the mount substrate from the core portion 721 of the external waveguide substrate 702, for example, as shown in FIG. 4B, the core portion 717 provided on the light receiving side mount substrate 703 is used. The second abutting surface 721a of the core portion 721 of the external waveguide substrate 702 that abuts against the first abutting surface 717a of the mounting substrate 702 on the side of the light receiving side gradually increases as the second abutting surface 721a goes upward on the connecting piece 705 side. It forms in the inclined surface inclined so that distance may become wide.

  Accordingly, even when the core portion 717 provided on the light receiving side mount substrate 703 is disposed at a lower position than the core portion 717 of the external waveguide substrate 702 by the adhesive layer 700, the external waveguide substrate 702 is disposed. The light from the core portion 717 is refracted obliquely downward on the core portion 717 side of the mount substrate 703 on the light receiving side at the second abutting surface 721a, and enters the core portion 717 provided on the mount substrate 703. Coupling loss can be suppressed.

  Next, an optical module according to a third embodiment will be described with reference to FIGS. 5 (a), 5 (b), and 5 (c). As shown in FIGS. 5A and 5B, the mount substrate 101 on the light emitting side of the optical module of the third embodiment receives and bonds the front end portion of the external waveguide substrate 2 to the rear end side. A receiving recess 140 is provided.

  Specifically, the light emitting side mount substrate 101 is cut into the light emitting side mount substrate 101 by cutting a part of the upper part of the rear end surface 110 of the light emitting side mount substrate 101 to the entire width. A receiving recess 140 having a side surface 141 formed so as to be substantially orthogonal to the axis O1 of the provided core portion 17 and a bottom surface 142 formed so as to be substantially orthogonal to the side surface 141 is provided. The first abutting surface 17a of the core portion 17 is substantially flush with the side surface 141. Others have the same configuration as that of the first embodiment.

  Then, the first butting surface 17a of the light emitting side mounting substrate 101 and the second butting surface 21a of the core portion 21 of the external waveguide substrate 2 are butted. In this state, an adhesive is put between the mount substrate 1 and the connecting piece 5, and the receiving recess 140 is filled with the adhesive from the side of the external waveguide substrate 2. As a result, the adhesive 100 penetrates between the receiving recess 140 and the external waveguide substrate 2 by capillary action, and the rear end of the mount substrate 101 and the front end of the external waveguide substrate 2 can be bonded.

  Therefore, in addition to the bonding between the mount substrate 1 and the connecting piece 5, the receiving recess 840 can be bonded, and the bonding area can be increased to increase the bonding strength. In addition, when the external waveguide substrate 2 is bent, the first butted surface 17a of the core portion 17 of the light emitting side mount substrate 101 and the second butted surface 21a of the core portion 21 of the external waveguide substrate 2 are separated from each other. It can be difficult.

  The depth of the receiving recess 140 is 50 μm to 500 μm when the light emitting side mount substrate 101 having a thickness of 500 μm is used and the external waveguide substrate 2 of 50 μm to 400 μm is used. The method for forming the receiving recess 140 is not particularly limited, and can be performed by, for example, half-cutting by dicing, dry etching by RIE, or the like. The shape of the receiving recess 140 is not limited to that shown in FIG. 4B. For example, as shown in FIG. 4C, the portion from the side surface 141a to the bottom surface 142a of the receiving recess 140a is curved. It can be changed as appropriate.

  Next, an optical module according to a fourth embodiment will be described with reference to FIGS. 6 (a), 6 (b), and 6 (c). As shown in FIGS. 6A and 6B, the mount substrate 201 on the light emitting side of the optical module of the fourth embodiment is configured by a groove 243 provided in the receiving recess 240.

  Specifically, the light emitting side mount substrate 201 in the fourth embodiment is provided with a receiving recess 240 formed by cutting from the rear end surface 210 in the same manner as the receiving recess 140 in the third embodiment. A groove 243 is provided on the bottom surface 242 of the receiving recess 240. The groove 243 of this embodiment is formed with a predetermined depth and width along the side surface 241 of the receiving recess 240. Others have the same configuration as that of the first embodiment.

  With this configuration, when an adhesive is applied to the receiving recess 240, the adhesive easily enters the groove 243 by capillary action. Further, the adhesive that has entered the groove 243 becomes difficult to come out of the groove 243 due to the anchor effect, and the adhesive strength can be increased.

  The depth of the groove 243 is not limited, but is effective at 10 μm to 200 μm. Also, the length of the groove is not particularly limited. For example, the groove may be provided over the entire width of the receiving recess 240 (mount substrate 201), or may be provided with a length substantially the same as the width dimension of the external waveguide substrate 2. .

  In addition, the shape of the groove is not limited to a rectangular cross section as shown in FIG. 6B, but is formed in a groove 243a having a semicircular cross section as shown in FIG. It can be changed as appropriate. The grooves 243 and 243a can also be formed by, for example, half cutting by dicing, dry etching by RIE, or the like.

  In the above embodiment, the connecting piece is provided on the external waveguide substrate. However, the connecting piece may be provided on the light emitting side mounting substrate or the light receiving side mounting substrate, and can be changed as appropriate.

1 is an overall schematic diagram of an optical module according to a first embodiment of the present invention. (A) is the principal part expansion perspective view of the state which turned the external waveguide board upside down, (b) is the principal part expansion perspective view of the mount board | substrate of the light emission side. (A) is the principal part enlarged plan view of the state which connected the mount board | substrate and the external waveguide board | substrate of the light emission side, (b) is the III-III sectional view taken on the line of Fig.3 (a). FIG. 6 is an explanatory diagram of a second embodiment of the present invention, where (a) is an enlarged cross-sectional view of a main part in a state where the light emitting side mount substrate and an external waveguide substrate are connected, and (b) is the external waveguide. It is a principal part expanded sectional view of the state which the board | substrate and the mount board | substrate of the light-receiving side connected. FIG. 5A is an explanatory diagram of a third embodiment of the present invention, where FIG. 5A is an enlarged plan view of a main part in a state where a mounting substrate on the light emission side and an external waveguide substrate are connected, and FIG. (C) is a cross-sectional view taken along the line V-V, and (c) is an enlarged cross-sectional view of the main part in a state in which the mount substrate on the light emitting side provided with the receiving recesses of the other embodiment and the external waveguide substrate are connected. FIG. 6A is an explanatory diagram of a fourth embodiment of the present invention. FIG. 6A is an enlarged plan view of a main part in a state where a mounting substrate on the light emitting side is connected to an external waveguide substrate, and FIG. (C) is a cross-sectional view taken along line VI-VI, and (c) is an enlarged cross-sectional view of the main part in a state in which the mounting substrate on the light emitting side provided with the receiving recess having the groove of the other embodiment and the external waveguide substrate are connected. .

Explanation of symbols

1, 101, 201, 701 Light emitting side mount substrate 2, 702 External waveguide substrate 3, 703 Light receiving side mount substrate 5, 705 Connecting piece 17, 717 Waveguide core portions 17a, 717a First abutting surfaces 21, 721 Core portion 21a, 721a of external waveguide Second abutting surface

Claims (4)

An optical module comprising a mount substrate on which an optical element is provided and an external waveguide substrate that is optically coupled to the mount substrate,
The mount substrate is provided with a waveguide having a core portion that is optically coupled to the optical element,
The core portion of the waveguide includes a first butting surface,
The external waveguide substrate is provided with an external waveguide having a core portion that can be optically coupled to the waveguide of the mount substrate,
The core portion of the external waveguide includes a second abutting surface, and the second abutting surface and the first abutting surface are abutted with each other, so that the waveguide and the external waveguide are optically coupled. And
Furthermore, a connection piece is provided on either one of the mount substrate and the external waveguide substrate,
The connecting piece is overlapped with any one of the other one of the mount substrate and the external waveguide substrate when the first abutting surface and the second abutting surface are abutted with each other. An optical module, which is bonded by an adhesive. The connecting piece is superimposed on a part of the other external waveguide substrate or the mount substrate in the thickness direction,
2. The optical module according to claim 1, wherein one of the first butted surface and the second butted surface that are abutted with each other is formed as an inclined surface that is inclined in the thickness direction.   An end of the other external waveguide substrate or the mount substrate is provided with a receiving recess for receiving a part of the end of the one mount substrate or the external waveguide substrate and bonding it with an adhesive. The optical module according to claim 1, wherein the optical module is characterized in that:   The optical module according to claim 3, wherein the receiving recess is provided with a groove formed at a predetermined depth from an inner surface of the receiving recess.

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