Optical coupler manufacturing method, optical coupler, photoelectric conversion circuit module, and optical transceiver

Abstract

This optical coupler manufacturing method comprises: a preparation step for preparing a translucent substrate (11) having a first main surface (SU11) and a second main surface (SU 12) which are arranged in a first direction (DIR1); a first coating step for coating the first main surface (SU11) with a first photosensitive glass paste (12) containing a first filler (P1); a masking step for disposing a gray scale mask (10), which is formed with a binary pattern, on the second main surface (SU12); an exposure step for exposing the first photosensitive glass paste (12) by irradiating the second main surface (SU12) with ultraviolet rays; a developing step for developing the first photosensitive glass paste (12) by removing the gray scale mask (10) from the second main surface (SU12); and a curing step for curing the first photosensitive glass paste (12) by removing the translucent substrate (11) from the developed first photosensitive glass paste (12). The maximum length (r1) of the first filler (P1) is longer than the wavelength of the ultraviolet rays.

Description

Optical coupler manufacturing method, optical coupler, photoelectric conversion circuit module, and optical transceiver

[0001] The present invention relates to a method for manufacturing an optical coupler, an optical coupler, an optoelectric conversion circuit module, and an optical transceiver.

[0002] For example, the grayscale mask described in Patent Document 1 is used for purposes such as manufacturing microlenses. The grayscale mask described in Patent Document 1 is composed of a plurality of adjacently arranged pixels. Each pixel has at least one unit area. The unit area is composed of a first area, which is a light-transmitting area that transmits light, and a second area, which is a light-shielding area that does not transmit light. The light transmittance of the unit area is determined according to the area ratio between the light-transmitting area and the light-shielding area.

[0003] Patent No. 5764948

[0004] When the grayscale mask described in Patent Document 1 is used as a photomask in the manufacture of optical couplers such as microlenses, the periodic structure of the light-transmitting and light-blocking regions causes light to be diffracted during exposure. The diffracted light is irradiated at a high level in directions other than the intended direction. As a result, the photosensitive material may not be exposed as designed, resulting in reduced processing accuracy.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for manufacturing an optical coupler that can prevent a decrease in processing accuracy, an optical coupler, an optoelectric conversion circuit module, and an optical transceiver.

[0006] A method for manufacturing an optical coupler according to one embodiment of the present invention includes: a preparation step of preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction; a first application step of applying a first photosensitive glass paste containing a first filler to the first main surface; a masking step of arranging a grayscale mask formed with a binary pattern on the second main surface; an exposure step of irradiating the second main surface with ultraviolet light to expose the first photosensitive glass paste; a development step of removing the grayscale mask from the second main surface and developing the first photosensitive glass paste; and a hardening step of removing the light-transmitting substrate from the developed first photosensitive glass paste and hardening the first photosensitive glass paste, wherein the longest length of the first filler is longer than the wavelength of the ultraviolet light.

[0007] When the longest length of the first filler is longer than the wavelength of the ultraviolet light, the ultraviolet light diffracted by the grayscale mask is scattered by the first filler. As a result, the diffracted light is not irradiated at a high level in directions other than the intended direction. Therefore, this embodiment can suppress a decrease in processing accuracy.

[0008] A method for manufacturing an optical coupler according to one embodiment of the present invention includes: a preparation step of preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction, the light-transmitting substrate including a third filler; a first application step of applying a first photosensitive glass paste to the first main surface; a masking step of arranging a grayscale mask formed with a binary pattern on the second main surface; an exposure step of irradiating the second main surface with ultraviolet light to expose the first photosensitive glass paste; a development step of removing the grayscale mask from the second main surface and developing the first photosensitive glass paste; and a curing step of removing the light-transmitting substrate from the developed first photosensitive glass paste and curing the first photosensitive glass paste, wherein the longest length of the third filler is longer than the wavelength of the ultraviolet light.

[0009] Even if the longest length of the third filler is longer than the wavelength of the ultraviolet light, the ultraviolet light diffracted by the grayscale mask is scattered by the third filler. As a result, the diffracted light is not irradiated at a high level in directions other than the intended direction. Therefore, this embodiment also can suppress a decrease in processing accuracy.

[0010] An optical coupler according to one embodiment of the present invention is an optical coupler made of a first photosensitive glass paste containing a first filler, wherein the longest length of the first filler is longer than the wavelength of ultraviolet light irradiated onto a grayscale mask formed with a binary pattern.

[0011] An optical coupler according to one embodiment of the present invention comprises: a first glass portion including a first glass and a first filler mixed within the first glass; and a second glass portion including at least a second glass and connected to the first glass portion, wherein the second glass portion includes the second filler mixed within the second glass, and the content of the second filler contained in the second glass portion is lower than the content of the first filler contained in the first glass portion, or the second glass portion does not include the second filler.

[0012] In this embodiment, the second glass portion contains no filler or has a lower filler content than the first glass portion. However, when ultraviolet light is irradiated from the first glass portion, the first filler in the first glass portion, which has a relatively high filler content, diffuses the diffracted light generated during manufacturing. As a result, diffracted light is not irradiated at a high level in directions other than the intended direction. Therefore, this embodiment also suppresses a decrease in processing accuracy.

[0013] An optical coupler according to one embodiment of the present invention comprises: a first glass portion; and a transmissive portion connected to the first glass portion; the first glass portion includes glass and a first filler mixed into the glass; the transmissive portion includes a medium and a second filler mixed into the medium; and the longest length of the second filler is different from the longest length of the first filler.

[0014] In this embodiment, the first glass portion or the transmissive portion having the longest filler length is irradiated with ultraviolet light to diffuse the diffracted light. As a result, high levels of diffracted light are not irradiated in directions other than the intended direction. Therefore, this embodiment also prevents a decrease in processing accuracy.

[0015] According to the optical coupler manufacturing method, the optical coupler, the photoelectric conversion circuit module, and the optical transceiver of the present invention, it is possible to suppress a decrease in processing accuracy.

[0016] FIG. 1 is a perspective view of the optical coupler 1. FIG. 2 is a cross-sectional view of the optical coupler 1 and the optical fiber 5. FIG. 3 is a plan view of the optical coupler 1 viewed in the first direction DIR1. FIG. 4 is a flowchart showing a manufacturing method of the optical coupler 1. FIG. 5 is a cross-sectional view of the optical coupler 1 during manufacturing. FIG. 6 is a diagram showing pixels 15 of a grayscale mask 10. FIG. 7 is a diagram showing a pattern in which the pixels 15 of the grayscale mask 10 are arranged in order of aperture ratio. FIG. 8 is an example of a grayscale mask 10 corresponding to the optical coupler 1. FIG. 9 is a light intensity distribution of a comparative example during an exposure process. FIG. 10 is a light intensity distribution of the first embodiment during an exposure process. FIG. 11 is a perspective view of a light-transmitting substrate 11. FIG. 12 is a cross-sectional view of the optical coupler 1b and the optical fiber 5. FIG. 13 is a flowchart showing a manufacturing method of the optical coupler 1b. FIG. 14 is a cross-sectional view of the optical coupler 1b during manufacturing. FIG. 15 is a cross-sectional view of the optical coupler 1c and the optical fiber 5. FIG. 16 is a cross-sectional view of the optical coupler 1c during manufacturing. Fig. 17 is a cross-sectional view of the optical coupler 1d and the optical fiber 5. Fig. 18 is a perspective view of the optoelectronic conversion circuit module 50 and the optical fiber 5. Fig. 19 is a cross-sectional view of the optoelectronic conversion circuit module 50 and the optical fiber 5 taken along line A-A. Fig. 20 is a perspective view of the optoelectronic conversion circuit module 50a and the optical fiber 5. Fig. 21 is a perspective view of the optical transceiver 100 and the optical fiber 5.

[0017] [First Embodiment] [Structure of Optical Coupler 1] An optical coupler 1 according to a first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view of the optical coupler 1. Note that in Fig. 1, only a representative first filler P1 among a plurality of first fillers P1 is designated by a reference symbol. Fig. 2 is a cross-sectional view of the optical coupler 1 and an optical fiber 5. Note that the second side wall portion 22 and the third side wall portion 23 are omitted in Fig. 2. Fig. 3 is a plan view of the optical coupler 1 viewed in a first direction DIR1.

[0018] In this specification, directions are defined as follows. As shown in FIG. 1 , the direction in which the bottom portion 24 and the reflecting portion 3 are arranged in this order is defined as a first direction DIR1. The direction in which the reflecting portion 3 and the optical fiber fixing portion 4 are arranged in this order is defined as a second direction DIR2. The direction in which the second side wall portion 22 and the third side wall portion 23 are arranged in this order is defined as a third direction DIR3. The first direction DIR1, the second direction DIR2, and the third direction DIR3 are perpendicular to each other. However, the first direction DIR1, the second direction DIR2, and the third direction DIR3 in this specification are defined for the convenience of explanation and do not necessarily coincide with the first direction DIR1, the second direction DIR2, and the third direction DIR3 when the optical coupler 1 is in use.

[0019] The optical coupler 1 is a device for changing the direction of travel of light emitted from a photoelectric conversion circuit or the like and outputting the light into an optical fiber, or for changing the direction of travel of light emitted from an optical fiber and outputting the light into a photoelectric conversion circuit or the like. In this embodiment, a case will be described in which the optical coupler 1 changes the direction of travel of light L emitted from a photoelectric conversion circuit or the like from a first direction DIR1 to a second direction DIR2 and outputs the light into an optical fiber 5. As shown in FIG. 2 , the optical coupler 1 has an incident surface S11 through which the light L is incident in the first direction DIR1 and an exit surface S12 through which the light L is output in the second direction DIR2. Note that, when the optical coupler 1 changes the direction of travel of light L emitted from the optical fiber 5 from the opposite direction of the second direction DIR2 to the opposite direction of the first direction DIR1 and outputs the light into a photoelectric conversion circuit or the like, the incident surface and the exit surface may be interchanged. Note that the optical coupler 1 is an example of an “optical coupler” of the present invention. The "optical coupler" of the present invention may be a condenser lens, a microlens array, etc. The structure of the optical coupler 1 will be described in detail below.

[0020] As shown in FIG. 1 , the optical coupler 1 includes a holding portion 2, a reflecting portion 3, and an optical fiber fixing portion 4. The optical coupler 1 is integrally molded from glass containing a filler. The optical coupler 1 is also a single member. Here, a single member means a member that has a structure that makes it impossible to separate without being damaged. Therefore, for example, a member in which two resin pieces are fixed with screws is not a single member. The optical coupler 1 does not have to be integrally molded from glass containing a filler. The optical coupler 1 does not have to be a single member.

[0021] The optical coupler 1 is integrally molded from a material including glass M1 and a plurality of first fillers P1 mixed in the glass M1. The glass is an amorphous material that exhibits a glass transition phenomenon. The glass is, for example, SiO ２ , B ２ O ３ , P ２ O ５ , GeO ２ , AS3O ３ Glass of simple oxides such as Li ２ O—SiO ２ , Na ２ O—SiO ２ , K ２ O—SiO ２ Silicate glass such as Na ２ O-Al ２ O ３ -SiO ２ , CaO-Al ２ O ３ -SiO ２ aluminosilicate glasses such as Li ２ Alumni ２ O ３ , Na ２ Alumni ２ O ３ Borate glasses such as CaO—Al ２ O ３ -B ２ O ３ Aluminoborate glass such as Na ２ O-Al ２ O ３ -B ２ O ３-SiO ２ and borosilicate glasses such as:

[0022] The plurality of first fillers P1 are metal oxide particles such as crystalline silica, amorphous silica, alumina, magnesium oxide, titanium oxide, barium titanate, or calcium titanate, or organic particles such as graphite. The first filler P1 includes a filler having a non-spherical shape. The plurality of first fillers P1 are dispersed throughout the glass M1. Note that the first filler P1 does not necessarily include a filler having a non-spherical shape. Furthermore, the plurality of first fillers P1 may be dispersed uniformly throughout the glass M1, or may be dispersed unevenly throughout the glass M1.

[0023] The longest length of each of the multiple first fillers P1 is defined as r1. If each of the multiple first fillers P1 has a spherical shape, the longest length r1 of each of the multiple first fillers P1 is the diameter of the sphere. If each of the multiple first fillers P1 has an oval spherical shape, the longest length r1 of each of the multiple first fillers P1 is the length in the major axis direction of the oval sphere. Thus, the longest length r1 of each of the multiple first fillers P1 is the longitudinal length of the longest portion of each of the multiple first fillers P1. In this embodiment, the maximum value of the longest length r1 of each of the multiple first fillers P1 is longer than the wavelength λ of ultraviolet light UV, which will be described later. In other words, there is a first filler P1 having a longest length r1 longer than the wavelength λ of ultraviolet light UV.

[0024] The holding portion 2 holds each of the reflecting portion 3 and the optical fiber fixing portion 4. The holding portion 2 is connected to each of the reflecting portion 3 and the optical fiber fixing portion 4. The holding portion 2 includes a first side wall portion 21, a second side wall portion 22, a third side wall portion 23, and a bottom portion 24. Note that the holding portion 2 does not necessarily have to include each of the first side wall portion 21, the second side wall portion 22, and the third side wall portion 23.

[0025] The first side wall portion 21 is connected to each of the second side wall portion 22, the third side wall portion 23, and the bottom portion 24. More specifically, the first side wall portion 21 has a shape extending in the third direction DIR3. In this embodiment, the first side wall portion 21 has a plate shape. An end face of the first side wall portion 21 in the third direction DIR3 is connected to the third side wall portion 23. An end face of the first side wall portion 21 in the opposite direction to the third direction DIR3 is connected to the second side wall portion 22. An end face of the first side wall portion 21 in the opposite direction to the first direction DIR1 is connected to the bottom portion 24. Note that the first side wall portion 21 does not have to have a plate shape.

[0026] The second side wall portion 22 is connected to each of the first side wall portion 21, the bottom portion 24, the reflecting portion 3, and the optical fiber fixing portion 4. More specifically, the second side wall portion 22 has a shape extending in the second direction DIR2. In this embodiment, the second side wall portion 22 has a plate shape. A portion of the end face of the second side wall portion 22 in the third direction DIR3 is connected to each of the end face of the first side wall portion 21 in the direction opposite to the third direction DIR3, the reflecting portion 3, and the optical fiber fixing portion 4. The end face of the second side wall portion 22 in the direction opposite to the first direction DIR1 is connected to the bottom portion 24. Note that the second side wall portion 22 does not have to have a plate shape.

[0027] The third side wall 23 is connected to each of the first side wall 21, the bottom 24, the reflecting unit 3, and the optical fiber fixing unit 4. More specifically, the third side wall 23 has a shape extending in the second direction DIR2. In this embodiment, the third side wall 23 has a plate shape. A portion of the end face of the third side wall 23 in the direction opposite to the third direction DIR3 is connected to each of the end face of the first side wall 21 in the third direction DIR3, the reflecting unit 3, and the optical fiber fixing unit 4. The end face of the third side wall 23 in the direction opposite to the first direction DIR1 is connected to the bottom 24. Note that the third side wall 23 does not have to have a plate shape.

[0028] The bottom 24 is connected to each of the first side wall 21, the second side wall 22, the third side wall 23, the reflecting unit 3, and the optical fiber fixing unit 4. More specifically, the bottom 24 has a plate shape. In this embodiment, the bottom 24 has a rectangular shape when viewed in the first direction DIR1. A portion of the end face of the bottom 24 in the first direction DIR1 is connected to each of the end face of the first side wall 21 in the direction opposite to the first direction DIR1, the end face of the second side wall 22 in the direction opposite to the first direction DIR1, the end face of the third side wall 23 in the direction opposite to the first direction DIR1, the reflecting unit 3, and the optical fiber fixing unit 4. Note that the bottom 24 does not have to have a rectangular shape when viewed in the first direction DIR1.

[0029] 2 , light L enters the optical coupler 1 from an end face S1 of the bottom 24 that faces in the opposite direction to the first direction DIR1. Therefore, the end face S1 of the bottom 24 that faces in the opposite direction to the first direction DIR1 includes the incident surface S11 of the optical coupler 1. The light L that enters the bottom 24 from the end face S1 of the bottom 24 that faces in the opposite direction to the first direction DIR1 passes through the inside of the bottom 24 and enters the reflector 3.

[0030] As shown in FIG. 3 , the area of ​​the end face S1 of the bottom 24 facing the opposite direction to the first direction DIR1 that overlaps with the reflector 3 when viewed in the first direction DIR1 is defined as area A1. The area of ​​the end face S1 of the bottom 24 facing the opposite direction to the first direction DIR1 that does not overlap with the reflector 3 when viewed in the first direction DIR1 is defined as area A2. The end face S1 of the bottom 24 facing the opposite direction to the first direction DIR1 includes both area A1 and area A2. Light L enters the optical coupler 1 from area A1 of the bottom 24. Therefore, area A1 is the incident surface S11. Area A2 is the mounting surface S21 for mounting the optical coupler 1 on a substrate when the optical coupler 1 is incorporated into an optoelectronic conversion circuit module or the like. The end face S1 of the bottom 24 facing the opposite direction to the first direction DIR1 includes the incident surface S11 and the mounting surface S21. That is, the mounting surface S21 is in the same plane as the incident surface S11.

[0031] As shown in Fig. 1 , the reflector 3 is connected to each of the second side wall 22, the third side wall 23, and the bottom 24. As shown in Fig. 2 , the reflector 3 changes the traveling direction of light L incident on the incident surface S11 from a first direction DIR1 to a second direction DIR2, and outputs the light to one of the five optical fibers 5. The reflector 3 includes a prism portion 31 and five condenser lens portions 32. The number of condenser lens portions 32 is not limited to five. Furthermore, the reflector 3 does not necessarily have to include a condenser lens portion 32.

[0032] The prism portion 31 is connected to each of the second side wall portion 22, the third side wall portion 23, and the bottom portion 24. More specifically, in this embodiment, the prism portion 31 has a right-angled isosceles triangular prism shape extending in the third direction DIR3. The prism portion 31 has a prism portion entrance surface S2, a prism portion reflection surface S3, a prism portion exit surface S4, an end face in the third direction DIR3, and an end face in the opposite direction to the third direction DIR3. The end face of the prism portion 31 in the third direction DIR3 is connected to the third side wall portion 23. The end face of the prism portion 31 in the opposite direction to the third direction DIR3 is connected to the second side wall portion 22. Note that the prism portion 31 does not have to have a right-angled isosceles triangular prism shape.

[0033] The prism portion incident surface S2 is an end surface of the prism portion 31 in the opposite direction to the first direction DIR1. The prism portion incident surface S2 is connected to the bottom portion 24. The light L that has passed through the inside of the bottom portion 24 is incident on the prism portion 31 from the prism portion incident surface S2. The light L that has entered the prism portion 31 from the prism portion incident surface S2 passes through the inside of the prism portion 31.

[0034] When viewed in the third direction DIR3, the prism portion reflective surface S3 forms an angle of 45 degrees with both the prism portion entrance surface S2 and the prism portion exit surface S4. The end of the prism portion reflective surface S3 in the first direction DIR1 is located in the second direction DIR2 further from the end of the prism portion reflective surface S3 in the opposite direction to the first direction DIR1. The prism portion reflective surface S3 reflects light L that has passed through the interior of the prism portion 31. As a result, the prism portion reflective surface S3 changes the traveling direction of the light L from the first direction DIR1 to the second direction DIR2.

[0035] Five condenser lens portions 32 are provided on the prism portion reflecting surface S3. The five condenser lens portions 32 are aligned in the third direction DIR3. The surfaces of the condenser lens portions 32 are aspherical. The condenser lens portions 32 condense and reflect light L that passes through the inside of the prism portion 31 and whose traveling direction vector includes a component of the first direction DIR1. As a result, the condenser lens portions 32 change the traveling direction of the light L from a direction including a component of the first direction DIR1 to the second direction DIR2.

[0036] The prism unit exit surface S4 is an end face of the prism unit 31 in the first direction DIR1. The prism unit exit surface S4 is perpendicular to the prism unit entrance surface S2. The prism unit exit surface S4 emits light L that has been reflected by the prism unit reflecting surface S3 or the condenser lens unit 32 and passed through the inside of the prism unit 31. The light L emitted from the prism unit exit surface S4 travels in the first direction DIR1. The prism unit exit surface S4 is the exit surface S12 of the optical coupler 1.

[0037] The optical fiber fixing portion 4 fixes each of the five optical fibers 5. The optical fiber fixing portion 4 is connected to each of the second side wall portion 22, the third side wall portion 23, and the bottom portion 24. More specifically, the optical fiber fixing portion 4 has a plate shape extending in the third direction DIR3. In this embodiment, the end face of the optical fiber fixing portion 4 in the third direction DIR3 is connected to the third side wall portion 23. The end face of the optical fiber fixing portion 4 in the opposite direction to the third direction DIR3 is connected to the second side wall portion 22. The end face of the optical fiber fixing portion 4 in the opposite direction to the first direction DIR1 is connected to the bottom portion 24.

[0038] As shown in FIG. 1 , five V-shaped grooves G are provided on the end face of the optical fiber fixing part 4 in the first direction DIR1 when viewed in the second direction DIR2. Each of the five grooves G has a shape extending in the second direction DIR2. The five grooves G are aligned in the third direction DIR3. As shown in FIG. 2 , five optical fibers 5 are fixed to each of the five grooves G. The five optical fibers 5 are aligned in the third direction DIR3. Each of the five optical fibers 5 and the five focusing lens parts 32 are aligned in the second direction DIR2 when viewed in the first direction DIR1. Note that no grooves G may be provided on the end face of the optical fiber fixing part 4 in the first direction DIR1. Furthermore, each of the five grooves G may have a U-shape when viewed in the second direction DIR2. Furthermore, the number of grooves G is not limited to five.

[0039] Each of the five optical fibers 5 has a shape that extends in the second direction DIR2. The end face of each of the five optical fibers 5 facing the opposite side of the second direction DIR2 faces the opposite side of the second direction DIR2. The end face of each of the five optical fibers 5 facing the opposite side of the second direction DIR2 faces the prism section exit surface S4 with a gap therebetween. As a result, the light L emitted from the prism section exit surface S4 is incident on one of the five optical fibers 5.

[0040] [Method of Manufacturing Optical Coupler 1] Next, a method of manufacturing the optical coupler 1 will be described with reference to the drawings. FIG. 4 is a flowchart showing a method of manufacturing the optical coupler 1. FIG. 5 is a cross-sectional view of the optical coupler 1 during manufacturing. Note that the second side wall portion 22 and the third side wall portion 23 are omitted in FIG. 5. FIG. 6 is a diagram showing pixels 15 of the grayscale mask 10. FIG. 7 is a diagram showing a pattern in which the pixels 15 of the grayscale mask 10 are arranged in order of aperture ratio. FIG. 8 is an example of a grayscale mask 10 corresponding to the optical coupler 1.

[0041] First, as shown in Fig. 5, a light-transmitting substrate 11 having a first main surface SU11 and a second main surface SU12 aligned in a first direction DIR1 is prepared (preparation step, Fig. 4: step ST1). The first main surface SU11 is positioned further in the first direction DIR1 than the second main surface SU12. The light-transmitting substrate 11 has a plate shape.

[0042] Next, a first photosensitive glass paste 12 is applied to the first main surface SU11 of the light-transmitting substrate 11 (first application step, FIG. 4 : step ST2). In this embodiment, the first photosensitive glass paste 12 is negative. In a developing step described later, the solubility of the exposed portions in a developer decreases. As a result, the exposed portions of the first photosensitive glass paste 12 remain. The first photosensitive glass paste 12 may be positive. In this case, the solubility of the exposed portions in a developer increases in a developing step described later. As a result, the unexposed portions of the first photosensitive glass paste 12 remain. The first photosensitive glass paste 12 includes a glass M1 and a plurality of first fillers P1 mixed into the glass M1. In addition to the glass M1 and the plurality of first fillers P1 mixed into the glass M1, the first photosensitive glass paste 12 may include additives such as a dispersant and a light absorber.

[0043] Next, a grayscale mask 10 is placed on the second main surface SU12 of the light-transmitting substrate 11 (mask process, FIG. 4: step ST3). The grayscale mask 10 is formed with a binary pattern. The grayscale mask 10 adjusts the light transmittance by controlling the aperture ratio. The grayscale mask 10 will be described in detail below.

[0044] As shown in Figure 6, the grayscale mask 10 is configured with a plurality of pixels 15 arranged adjacent to each other. Each pixel 15 has a unit area 16 and a runner portion 17. The unit area 16 is square when viewed in the first direction DIR1. The unit area 16 is further divided into four square portions A11, A12, A21, and A22. The runner portion 17 is arranged around the unit area 16 when viewed in the first direction DIR1. The runner portion 17 is a light-shielding area b that does not transmit light.

[0045] Each unit region 16 is composed of an open light-transmitting region a (which transmits light) and a closed light-shielding region b (which does not transmit light). The opening ratio (light transmittance) of each unit region 16 changes as the area ratio between the light-transmitting region a and the light-shielding region b changes.

[0046] For example, when all four square portions A11, A12, A21, and A22 are open, the aperture ratio of the unit region 16 is 100%. When two square portions A12 and A21 are open and two square portions A11 and A22 are not open, the area ratio of the light-transmitting region a to the light-blocking region b is 1:1, and the aperture ratio (light transmittance) of the unit region 16 is 50%. When none of the four square portions A11, A12, A21, and A22 are open, the aperture ratio of the unit region 16 is 0%.

[0047] As shown in Fig. 7 , when unit regions 16 in the grayscale mask 10 with aperture ratios ranging from 0% to 100% are arranged in this order in the second direction DIR2, the pattern of the grayscale mask 10 forms a gradation. While the unit regions 16 with aperture ratios that differ by 10% are arranged in order in Fig. 7 , it is possible to maintain continuity of light transmittance by increasing the resolution of the aperture ratio, for example, by arranging unit regions 16 with aperture ratios that differ by 0.1% in order. In this way, the grayscale mask 10 adjusts the light transmittance by controlling the aperture ratio.

[0048] As shown in FIG. 8 , the optical coupler 1 can be manufactured using the grayscale mask 10 by increasing the aperture ratio of the portions of the grayscale mask 10 corresponding to the first side wall portion 21, the second side wall portion 22, and the third side wall portion 23 and decreasing the aperture ratio of the portions of the grayscale mask 10 corresponding to the groove G.

[0049] Next, as shown in FIG. 5 , ultraviolet rays UV are irradiated onto the second main surface SU12 of the light-transmitting substrate 11 to expose the first photosensitive glass paste 12 (exposure process, FIG. 4 : step ST4). The wavelength λ of the ultraviolet rays UV is longer than 10 nm and shorter than 380 nm. The exposure process exposes the first photosensitive glass paste 12 to light. In this embodiment, as described above, the maximum value of the longest length r1 of each of the multiple first fillers P1 is longer than the wavelength λ of the ultraviolet rays UV.

[0050] Next, the grayscale mask 10 is removed from the second main surface SU12 of the light-transmitting substrate 11, and the first photosensitive glass paste 12 is developed (developing step, FIG. 4: step ST5). More specifically, the first photosensitive glass paste 12 and the light-transmitting substrate 11 are immersed in a developer. By the developing step, the exposed portions of the first photosensitive glass paste 12 remain, and the unexposed portions are removed. After development, the first photosensitive glass paste 12 and the light-transmitting substrate 11 are washed and dried.

[0051] Finally, the light-transmitting substrate 11 is removed from the developed first photosensitive glass paste 12, and the first photosensitive glass paste 12 is cured (curing step, FIG. 4 : step ST6). More specifically, the first photosensitive glass paste 12 is fired to harden the first photosensitive glass paste 12. Through the above steps, the optical coupler 1 is completed. Alternatively, as shown in FIG. 5 , grayscale masks 10 corresponding to multiple optical couplers 1 may be placed on the second main surface SU12 of the light-transmitting substrate 11, and after the first photosensitive glass paste 12 has hardened, the hardened first photosensitive glass paste 12 may be cut to complete the multiple optical couplers 1.

[0052] [Effect] The manufacturing method of the optical coupler 1 can suppress a decrease in processing accuracy. As a comparative example, a manufacturing method of an optical coupler that does not include a filler will be described with reference to the drawings. FIG. 9 shows the light intensity distribution of the comparative example in the exposure process. FIG. 10 shows the light intensity distribution of the first embodiment in the exposure process. Note that in FIGS. 9 and 10, the ultraviolet light UV is laser light. Furthermore, the beam diameter of the ultraviolet light UV is sufficiently smaller than the light transmission region a.

[0053] During the exposure process, ultraviolet light UV is diffracted by the periodic structure of the light-transmitting regions a and light-shielding regions b of the grayscale mask 10. If the first photosensitive glass paste 12 does not contain a filler, as shown in FIG. 9 , high levels of light are distributed in areas other than the position x1 in the second direction DIR2 of the ultraviolet light UV. Therefore, high levels of ultraviolet light UV are also exposed to portions of the first photosensitive glass paste 12 other than the position x1. In this embodiment, the first photosensitive glass paste 12 is negative. Therefore, during the development process, portions of the first photosensitive glass paste 12 other than the position x1 are likely to remain. Thus, light distributed in areas other than the position x1 can cause a decrease in processing accuracy.

[0054] Therefore, according to the manufacturing method of the optical coupler 1, the first photosensitive glass paste 12 contains a first filler P1. The longest length r1 of the first filler P1 is longer than the wavelength λ of the ultraviolet light UV. As a result, the ultraviolet light UV diffracted by the periodic structure of the light-transmitting region a and the light-blocking region b of the grayscale mask 10 is scattered by the first filler P1. As a result, the light intensity distribution of the ultraviolet light UV becomes a normal distribution with the strongest light at position x1. As shown in FIG. 10, the light intensity I(x) distributed at positions other than x1 is smaller than that of the comparative example, and high levels of ultraviolet light UV are not irradiated at positions other than x1. Therefore, during the development process, portions of the first photosensitive glass paste 12 other than position x1 are less likely to remain. As a result, according to the manufacturing method of the optical coupler 1, a decrease in processing accuracy can be suppressed.

[0055] Note that scattering of the ultraviolet rays UV is suppressed when the longest length r1 of the first filler P1 is equal to or less than the wavelength λ of the ultraviolet rays UV. Therefore, when using a grayscale mask 10 formed with a binary pattern, scattering of the ultraviolet rays UV occurs by making the longest length r1 of the first filler P1 longer than the wavelength λ of the ultraviolet rays UV, and it is possible to reduce the light intensity I(x) distributed in areas other than the position x1 in the second direction DIR2 of the ultraviolet rays UV.

[0056] Furthermore, according to the manufacturing method of the optical coupler 1, the content of the first filler P1 contained in the first photosensitive glass paste 12 can be reduced. More specifically, the first filler P1 contains fillers having aspherical shapes. This allows for more scattering of ultraviolet light UV than when the first filler P1 contains only fillers having spherical shapes. As a result, according to the manufacturing method of the optical coupler 1, the content of the first filler P1 contained in the first photosensitive glass paste 12 can be reduced.

[0057] [First Modification] [Structure of Optical Coupler 1a] An optical coupler 1a according to a first modification of the present invention will be described below. Note that, with regard to the structure of the optical coupler 1a according to the first modification, only the parts that differ from the structure of the optical coupler 1 according to the first embodiment will be described, and the rest will be omitted.

[0058] In this modified example, the longest length r1 of each of the multiple first fillers P1 is smaller than the wavelength λ of the ultraviolet ray UV. Note that in this modified example, the longest length r1 of each of the multiple first fillers P1 may be equal to or greater than the wavelength λ of the ultraviolet ray UV. Also, in this modified example, the optical coupler 1a may not include the first filler P1. Note that in this modified example, the optical coupler 1a corresponds to the "first glass portion" of the present invention.

[0059] [Method of Manufacturing Optical Coupler 1a] Next, a method of manufacturing an optical coupler 1a according to a first modified example of the present invention will be described with reference to the drawings. Fig. 11 is a perspective view of the light-transmitting substrate 11. Note that in Fig. 11, only a representative third filler P3 among the multiple third fillers P3 is designated by a reference symbol. Note that, with regard to the method of manufacturing the optical coupler 1a according to the first modified example, only the parts that differ from the method of manufacturing the optical coupler 1 according to the first embodiment will be described, and the rest will be omitted.

[0060] The light-transmitting substrate 11 includes a medium M2 and a plurality of third fillers P3 mixed in the medium M2. The medium M2 is, for example, a resin. The medium M2 may also be glass or the like.

[0061] The plurality of third fillers P3 are metal oxide particles such as crystalline silica, amorphous silica, alumina, magnesium oxide, titanium oxide, barium titanate, or calcium titanate, or organic particles such as graphite. The third filler P3 includes a filler having a non-spherical shape. The plurality of third fillers P3 are dispersed throughout the medium M2. Note that the third filler P3 does not necessarily include a filler having a non-spherical shape. The plurality of third fillers P3 may be dispersed uniformly throughout the medium M2, or may be dispersed unevenly throughout the medium M2.

[0062] The longest length of each of the multiple third fillers P3 is defined as r3. If each of the multiple third fillers P3 has a spherical shape, the longest length r3 of each of the multiple third fillers P3 is the diameter of the sphere. If each of the multiple third fillers P3 has an oval spherical shape, the longest length r3 of each of the multiple third fillers P3 is the length in the major axis direction of the oval sphere. Thus, the longest length r3 of each of the multiple third fillers P3 is the longitudinal length of the longest portion of each of the multiple third fillers P3. In this modified example, the maximum value of the longest length r3 of each of the multiple third fillers P3 is longer than the wavelength λ of ultraviolet light UV. Therefore, the maximum value of the longest length r3 of each of the multiple third fillers P3 is longer than the maximum value of the longest length r1 of each of the multiple first fillers P1. There is a third filler P3 having a longest length r3 longer than the maximum value of the longest length r1 of the first filler P1.

[0063] In this modification, the light-transmitting substrate 11 does not need to be removed from the developed first photosensitive glass paste 12 in the curing step. That is, the light-transmitting substrate 11 may be connected to the optical coupler 1 a. In this case, the light-transmitting substrate 11 corresponds to the "transmitting portion" of the present invention.

[0064] The above-described manufacturing method of the optical coupler 1a also achieves the same effects as the manufacturing method of the optical coupler 1. Furthermore, according to the manufacturing method of the optical coupler 1a, the content of the first filler P1 contained in the first photosensitive glass paste 12 can be reduced. More specifically, the longest length r3 of the third filler P3 contained in the light-transmitting substrate 11 is longer than the wavelength λ of the ultraviolet (UV) light. As a result, the ultraviolet (UV) light diffracted by the periodic structure of the light-transmitting region a and the light-blocking region b of the grayscale mask 10 is scattered by the third filler P3 contained in the light-transmitting substrate 11. As a result, the light intensity distribution of the ultraviolet (UV) light becomes a normal distribution with the strongest light intensity at position x1. The light intensity I(x) distributed other than at position x1 is smaller than in the comparative example, and high levels of ultraviolet (UV) light are not irradiated at positions other than x1. Therefore, in the development process, portions of the first photosensitive glass paste 12 other than at position x1 are less likely to remain. This makes it possible to suppress a decrease in processing accuracy even when the content of the first filler P1 contained in the first photosensitive glass paste 12 is reduced. As a result, according to the method for manufacturing the optical coupler 1 a, the content of the first filler P1 contained in the first photosensitive glass paste 12 can be reduced.

[0065] Furthermore, the manufacturing method of the optical coupler 1a can improve the processing accuracy of the optical coupler 1a. More specifically, the third filler P3 includes fillers having aspherical shapes. This allows for more scattering of ultraviolet light UV than when the third filler P3 includes only fillers having spherical shapes. Therefore, the manufacturing method of the optical coupler 1a can reduce the content of the third filler P3 in the light-transmitting substrate 11. As a result, the manufacturing method of the optical coupler 1a can improve the processing accuracy of the optical coupler 1a.

[0066] [Second Modification] [Structure of Optical Coupler 1b] An optical coupler 1b according to a second modification of the present invention will be described below with reference to the drawings. Fig. 12 is a cross-sectional view of the optical coupler 1b and the optical fiber 5. Note that the second side wall portion 22 and the third side wall portion 23 are omitted in Fig. 12. Note that, with regard to the structure of the optical coupler 1b according to the second modification, only the parts that differ from the structure of the optical coupler 1 according to the first embodiment will be described, and the rest will be omitted.

[0067] In this modification, a plurality of first fillers P1 are contained only in the bottom portion 24, and no filler is contained in the first side wall portion 21, the second side wall portion 22, the third side wall portion 23, the reflecting portion 3, or the optical fiber fixing portion 4. It is noted that a plurality of first fillers P1 are contained only in the end face S1 of the bottom portion 24 facing in the opposite direction to the first direction DIR1, and no filler may be contained in any portion of the bottom portion 24 other than the end face S1 facing in the opposite direction to the first direction DIR1. In this modification, the bottom portion 24 corresponds to the "first glass portion" of the present invention. The first side wall portion 21, the second side wall portion 22, the third side wall portion 23, the reflecting portion 3, and the optical fiber fixing portion 4 each correspond to the "second glass portion" or the "transmitting portion" of the present invention. The "second glass portion" of the present invention includes at least glass.

[0068] [Manufacturing Method of Optical Coupler 1b] Next, a manufacturing method of the optical coupler 1b according to a second modified example of the present invention will be described with reference to the drawings. Fig. 13 is a flowchart showing the manufacturing method of the optical coupler 1b. Fig. 14 is a cross-sectional view of the optical coupler 1b during manufacturing. Note that the second side wall portion 22 and the third side wall portion 23 are omitted in Fig. 14. Note that, with regard to the manufacturing method of the optical coupler 1b according to the second modified example, only the parts that differ from the manufacturing method of the optical coupler 1 according to the first embodiment will be described, and the rest will be omitted.

[0069] In this modification, after the first application step, a second photosensitive glass paste 13 containing no filler is applied to the first photosensitive glass paste 12 (second application step, FIG. 13 : step ST21). In this modification, the second photosensitive glass paste 13 is negative type. Note that, if the first photosensitive glass paste 12 is positive type, the second photosensitive glass paste 13 may also be positive type. Note that, in addition to glass, the second photosensitive glass paste 13 may contain additives such as a dispersant or a light absorber. Note that the second application step may be performed after the masking step. The second application step may be performed between the first application step and the exposure step.

[0070] In the exposure step, ultraviolet rays UV are irradiated onto the second main surface SU12 of the light-transmitting substrate 11, thereby exposing the first photosensitive glass paste 12 and the second photosensitive glass paste 13 ( FIG. 13 : step ST4). The exposure step exposes the first photosensitive glass paste 12 and the second photosensitive glass paste 13 to light.

[0071] In the development process, the grayscale mask 10 is removed from the second main surface SU12 of the light-transmitting substrate 11, and the first photosensitive glass paste 12 and the second photosensitive glass paste 13 are developed ( FIG. 13 : step ST5). More specifically, the first photosensitive glass paste 12, the second photosensitive glass paste 13, and the light-transmitting substrate 11 are immersed in a developer. In the development process, the exposed portions of the first photosensitive glass paste 12 and the second photosensitive glass paste 13 remain, and the unexposed portions are removed. After development, the first photosensitive glass paste 12, the second photosensitive glass paste 13, and the light-transmitting substrate 11 are washed and dried.

[0072] In the curing step, the light-transmitting substrate 11 is removed from the developed first photosensitive glass paste 12, and the first photosensitive glass paste 12 and the second photosensitive glass paste 13 are cured ( FIG. 13 : step ST6). More specifically, the first photosensitive glass paste 12 and the second photosensitive glass paste 13 are fired to cure the first photosensitive glass paste 12 and the second photosensitive glass paste 13.

[0073] The above-described manufacturing method for the optical coupler 1b also achieves the same effects as the manufacturing method for the optical coupler 1. More specifically, in the exposure process, ultraviolet rays UV are irradiated onto the second main surface SU12 of the light-transmitting substrate 11. Therefore, since the longest length r1 of the first filler P1 contained in the first photosensitive glass paste 12 applied to the first main surface SU11 of the light-transmitting substrate 11 is longer than the wavelength λ of the ultraviolet rays UV, the ultraviolet rays UV diffracted by the periodic structure of the light-transmitting region a and the light-shielding region b of the grayscale mask 10 are scattered by the first filler P1. As a result, the light intensity distribution of the ultraviolet rays UV becomes a normal distribution with the strongest intensity at position x1, and the light intensity I(x) distributed other than at position x1 is smaller than in the comparative example, preventing high levels of ultraviolet rays UV from being irradiated other than at position x1. Therefore, in the development process, portions of the first photosensitive glass paste 12 and the second photosensitive glass paste 13 other than at position x1 are less likely to remain. Therefore, even if the second photosensitive glass paste 13 applied to the first photosensitive glass paste 12 does not contain a filler, the same effect as that of the method for manufacturing the optical coupler 1 can be achieved.

[0074] Furthermore, according to the method for manufacturing the optical coupler 1b, the second photosensitive glass paste 13 does not contain filler, which makes it possible to improve the shape accuracy of the optical coupler 1b.

[0075] [Third Modification] [Structure of Optical Coupler 1c] An optical coupler 1c according to a third modification of the present invention will be described below. Fig. 15 is a cross-sectional view of the optical coupler 1c and the optical fiber 5. Note that the second side wall portion 22 and the third side wall portion 23 are omitted from Fig. 15. Note that, with regard to the structure of the optical coupler 1c according to the third modification, only the parts that differ from the structure of the optical coupler 1b according to the second modification will be described, and the rest will be omitted.

[0076] In this modification, the bottom 24 contains glass M1 and a plurality of first fillers P1 mixed into the glass M1. The first side wall 21, the second side wall 22, the third side wall 23, the reflecting unit 3, and the optical fiber fixing unit 4 each contain glass M1 and a plurality of second fillers P2 mixed into the glass M1. The content of the second filler P2 contained in each of the first side wall 21, the second side wall 22, the third side wall 23, the reflecting unit 3, and the optical fiber fixing unit 4 is lower than the content of the first filler P1 contained in the bottom 24. Note that the content of the second filler P2 contained in parts of the bottom 24 other than the end face S1 in the direction opposite to the first direction DIR1 may be lower than the content of the first filler P1 contained in the end face S1 of the bottom 24 in the direction opposite to the first direction DIR1.

[0077] The plurality of second fillers P2 are metal oxide particles such as crystalline silica, amorphous silica, alumina, magnesium oxide, titanium oxide, barium titanate, or calcium titanate, or organic particles such as graphite. The second filler P2 includes a filler having a non-spherical shape. The plurality of second fillers P2 are dispersed throughout the glass M1. Note that the second filler P2 does not necessarily include a filler having a non-spherical shape. Furthermore, the plurality of second fillers P2 may be dispersed uniformly throughout the glass M1, or may be dispersed unevenly throughout the glass M1.

[0078] [Manufacturing Method of Optical Coupler 1c] Next, a manufacturing method of the optical coupler 1c according to the third modified example of the present invention will be described with reference to the drawings. Fig. 16 is a cross-sectional view of the optical coupler 1c during manufacturing. Note that the second side wall portion 22 and the third side wall portion 23 are omitted from Fig. 16. Note that, with regard to the manufacturing method of the optical coupler 1c according to the third modified example, only the parts that differ from the manufacturing method of the optical coupler 1b according to the second modified example will be described, and the rest will be omitted.

[0079] In this modification, after the first application step, a second photosensitive glass paste 13 containing a second filler P2 is applied to the first photosensitive glass paste 12 (second application step). The content of the second filler P2 contained in the second photosensitive glass paste 13 is lower than the content of the first filler P1 contained in the first photosensitive glass paste 12. The second application step may be performed after the masking step. The second application step may be performed between the first application step and the exposure step.

[0080] The above-described method for manufacturing optical coupler 1 c also provides the same advantages as those of optical coupler 1 b. More specifically, for the same reasons as those of optical coupler 1 b, even if the content of second filler P2 contained in second photosensitive glass paste 13 applied to first photosensitive glass paste 12 is lower than the content of first filler P1 contained in first photosensitive glass paste 12, the same advantages as those of optical coupler 1 b can be provided.

[0081] Furthermore, according to the manufacturing method of the optical coupler 1c, the content of the second filler P2 contained in the second photosensitive glass paste 13 is lower than the content of the first filler P1 contained in the first photosensitive glass paste 12. Therefore, according to the manufacturing method of the optical coupler 1c, it is possible to improve the shape accuracy of the optical coupler 1c.

[0082] [Fourth Modification] [Structure of Optical Coupler 1d] An optical coupler 1d according to a fourth modification of the present invention will be described below with reference to the drawings. Fig. 17 is a cross-sectional view of the optical coupler 1d and the optical fiber 5. Note that the second side wall 22 and the third side wall 23 are omitted from Fig. 17. Note that, with regard to the structure of the optical coupler 1d according to the fourth modification, only the parts that differ from the structure of the optical coupler 1c according to the third modification will be described, and the rest will be omitted.

[0083] The longest length of each of the multiple second fillers P2 is defined as r2. If each of the multiple second fillers P2 has a spherical shape, the longest length r2 of each of the multiple second fillers P2 is the diameter of the sphere. If each of the multiple second fillers P2 has an oval spherical shape, the longest length r2 of each of the multiple second fillers P2 is the length in the major axis direction of the oval sphere. Thus, the longest length r2 of each of the multiple second fillers P2 is the longitudinal length of the longest portion of each of the multiple second fillers P2. In this modified example, the maximum value of the longest length r2 of each of the multiple second fillers P2 is greater than 0 and less than the wavelength λ of ultraviolet light UV. Therefore, the maximum value of the longest length r2 of each of the multiple second fillers P2 is shorter than the maximum value of the longest length r1 of each of the multiple first fillers P1. There is a first filler P1 having a longest length r1 that is longer than the maximum value of the longest length r2 of the second filler P2. The maximum value of the longest length r2 of each of the plurality of second fillers P2 is different from the maximum value of the longest length r1 of each of the plurality of first fillers P1.

[0084] [Method of Manufacturing Optical Coupler 1d] An optical coupler 1d according to a fourth modified example of the present invention will be described below. Note that, with regard to the method of manufacturing the optical coupler 1d according to the fourth modified example, only the parts that differ from the method of manufacturing the optical coupler 1c according to the third modified example will be described, and the rest will be omitted.

[0085] In this modification, the maximum value of the longest length r2 of each of the plurality of second fillers P2 contained in the second photosensitive glass paste 13 is greater than 0 and is equal to or less than the wavelength λ of the ultraviolet light UV.

[0086] The above-described method for manufacturing optical coupler 1d also achieves the same effects as those of optical coupler 1c. More specifically, for the same reasons as those of optical coupler 1c, even when the longest length r2 of second filler P2 contained in second photosensitive glass paste 13 applied to first photosensitive glass paste 12 is longer than 0 and equal to or less than the wavelength λ of ultraviolet light UV, the method for manufacturing optical coupler 1d achieves the same effects as those of optical coupler 1c.

[0087] Furthermore, according to the manufacturing method of the optical coupler 1d, the longest length r2 of the second filler P2 contained in the second photosensitive glass paste 13 is longer than 0 and is equal to or shorter than the wavelength λ of the ultraviolet light UV. Therefore, according to the manufacturing method of the optical coupler 1d, it is possible to improve the processing accuracy of the optical coupler 1d.

[0088] [Fifth Modification] [Structure of Photoelectric Conversion Circuit Module 50] A photoelectric conversion circuit module 50 according to a fifth modification will be described below with reference to the drawings. Fig. 18 is a perspective view of the photoelectric conversion circuit module 50 and the optical fiber 5. Note that in Fig. 18, reference numerals are assigned only to representative optical couplers 1, optical fibers 5, and optical waveguides OW among the plurality of optical couplers 1, the plurality of optical fibers 5, and the plurality of optical waveguides OW. Fig. 19 is a cross-sectional view taken along the line A-A of the photoelectric conversion circuit module 50 and the optical fiber 5.

[0089] As shown in FIG. 18 , the photoelectric conversion circuit module 50 includes a plurality of optical couplers 1, a substrate 51, and an optoelectric conversion circuit 52. The plurality of optical couplers 1 and the optoelectric conversion circuit 52 are mounted on the substrate 51. The optoelectric conversion circuit 52 is disposed at the center of the substrate 51 when viewed in the first direction DIR1. The plurality of optical couplers 1 are disposed around the optoelectric conversion circuit 52 when viewed in the first direction DIR1. Each of the plurality of optical fibers 5 is fixed to the optical fiber fixing portion 4 of each of the plurality of optical couplers 1. The number of optical couplers 1 is not limited to a plurality, and may be one. Furthermore, the optoelectric conversion circuit 52 does not have to be disposed at the center of the substrate 51 when viewed in the first direction DIR1. Furthermore, the plurality of optical couplers 1 do not have to be disposed around the optoelectric conversion circuit 52 when viewed in the first direction DIR1. Moreover, the photoelectric conversion circuit module 50 may include, instead of the optical coupler 1, an optical coupler 1a, an optical coupler 1b, an optical coupler 1c, or an optical coupler 1d.

[0090] The substrate 51 has a plate shape with two main surfaces aligned in the first direction DIR1. However, as shown in Fig. 19, an optical waveguide OW and a mirror M are provided inside the substrate 51. The optical waveguide OW is provided between the photoelectric conversion circuit 52 and each of the multiple optical couplers 1. The mirror M is provided in the opposite direction of the first direction DIR1 from the reflecting unit 3. The light L emitted from the photoelectric conversion circuit 52 passes through the optical waveguide OW.

[0091] The optical couplers 1 are mounted on one of the two main surfaces of the substrate 51 that is located in the first direction DIR1. More specifically, the mounting surface S21 is mounted on the other of the two main surfaces of the substrate 51 that is located in the first direction DIR1.

[0092] The photoelectric conversion circuit 52 is mounted on the principal surface of the substrate 51 that is located in the first direction DIR1, out of the two principal surfaces of the substrate 51. The photoelectric conversion circuit 52 converts an electrical signal into light that enters the optical coupler 1, or converts light that is emitted from the optical coupler 1 into an electrical signal. A case where the photoelectric conversion circuit 52 converts an electrical signal into light that enters the optical coupler 1 will be described.

[0093] The photoelectric conversion circuit 52 converts the electrical signal into light L that is incident on each of the multiple optical couplers 1. The light L emitted by the photoelectric conversion circuit 52 travels in the second direction DIR2 within the optical waveguide OW. The light L traveling in the second direction DIR2 within the optical waveguide OW is reflected by the mirror M. As a result, the traveling direction of the light L is changed from the second direction DIR2 to the first direction DIR1. The light L then enters the incident surface S11 of the optical coupler 1, and the traveling direction is changed by the optical coupler 1 from the first direction DIR1 to the second direction DIR2, and is emitted from the exit surface S12 of the optical coupler 1. As a result, the light L is incident on each of the five optical fibers 5.

[0094] The photoelectric conversion circuit module 50 as described above also provides the same effects as the optical coupler 1 .

[0095] [Sixth Modification] [Structure of Photoelectric Conversion Circuit Module 50a] A photoelectric conversion circuit module 50a according to a sixth modification will be described below with reference to the drawings. Fig. 20 is a perspective view of the photoelectric conversion circuit module 50a and the optical fiber 5. Note that in Fig. 20, reference numerals are assigned only to representative optical couplers 1 and optical fibers 5 among the plurality of optical couplers 1 and the plurality of optical fibers 5. Note that, for the photoelectric conversion circuit module 50a according to the sixth modification, only the differences from the photoelectric conversion circuit module 50 according to the fifth modification will be described, and the rest will be omitted.

[0096] The photoelectric conversion circuit module 50a differs from the photoelectric conversion circuit module 50 in that the substrate 51 is a semiconductor substrate and that the substrate 51 includes a plurality of light emitting portions 53. The number of light emitting portions 53 is not limited to a plurality and may be one.

[0097] Each of the plurality of light emitting portions 53 is, for example, a surface light emitting element formed on one of the two main surfaces of the substrate 51, the main surface being located in the first direction DIR1. Each of the plurality of light emitting portions 53 is, for example, a vertical cavity surface emitting laser (VCSEL). Each of the plurality of light emitting portions 53 emits light L based on an electrical signal generated by the photoelectric conversion circuit 52. The light L emitted from each of the plurality of light emitting portions 53 is incident on each of the plurality of optical fibers 5 via each of the plurality of optical couplers 1.

[0098] The photoelectric conversion circuit module 50 a as described above also provides the same effects as the photoelectric conversion circuit module 50 .

[0099] [Seventh Modification] [Structure of Optical Transceiver 100] The optical transceiver 100 will be described below with reference to the drawings. Fig. 21 is a perspective view of the optical transceiver 100 and the optical fibers 5. Note that in Fig. 21, only a representative optical fiber 5 out of the five optical fibers 5 is designated by a reference symbol. Note that for the optical transceiver 100 according to the seventh modification, only the differences from the optoelectric conversion circuit module 50a according to the sixth modification will be described, and the rest will be omitted.

[0100] The optical transceiver 100 differs from the photoelectric conversion circuit module 50a in that the optical transceiver 100 has one optical coupler 1 and one light emitting section 53.

[0101] The light L emitted by the light emitting section 53 enters each of the five optical fibers 5 via the optical coupler 1, or the light L emitted from each of the five optical fibers 5 enters the photoelectric conversion circuit 52 via the optical coupler 1.

[0102] The optical transceiver 100 as described above also provides the same effects as the photoelectric conversion circuit module 50a.

[0103] Other Embodiments The optical couplers according to the present invention are not limited to the optical coupler 1, the optical coupler 1a, the optical coupler 1b, the optical coupler 1c, and the optical coupler 1d, and may be modified within the scope of the gist thereof. In addition, the structures of the optical coupler 1, the optical coupler 1a, the optical coupler 1b, the optical coupler 1c, and the optical coupler 1d may be combined in any manner.

[0104] The photoelectric conversion circuit module according to the present invention is not limited to the photoelectric conversion circuit module 50 and the photoelectric conversion circuit module 50a, and can be modified within the scope of the present invention. Furthermore, the structures of the photoelectric conversion circuit module 50 and the photoelectric conversion circuit module 50a may be combined in any manner.

[0105] The optical transceiver according to the present invention is not limited to the optical transceiver 100, and can be modified within the scope of the gist thereof.

[0106] The present invention has the following configuration.

[0107] (1) A method for manufacturing an optical coupler, comprising: a preparation step of preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction; a first application step of applying a first photosensitive glass paste containing a first filler to the first main surface; a masking step of arranging a grayscale mask formed with a binary pattern on the second main surface; an exposure step of irradiating the second main surface with ultraviolet light to expose the first photosensitive glass paste; a development step of removing the grayscale mask from the second main surface and developing the first photosensitive glass paste; and a curing step of removing the light-transmitting substrate from the developed first photosensitive glass paste and curing the first photosensitive glass paste, wherein the longest length of the first filler is longer than the wavelength of the ultraviolet light.

[0108] (2) The method for manufacturing an optical coupler according to (1), further comprising a second application step between the first application step and the exposure step of applying a second photosensitive glass paste to the first photosensitive glass paste, wherein the first photosensitive glass paste and the second photosensitive glass paste are exposed to light in the exposure step, the first photosensitive glass paste and the second photosensitive glass paste are developed in the development step, and the first photosensitive glass paste and the second photosensitive glass paste are hardened in the hardening step, wherein the second photosensitive glass paste contains a second filler, and a content of the second filler contained in the second photosensitive glass paste is lower than a content of the first filler contained in the first photosensitive glass paste, or the second photosensitive glass paste does not contain the second filler.

[0109] (3) The method for manufacturing an optical coupler according to (1), further comprising a second application step between the first application step and the exposure step of applying a second photosensitive glass paste containing a second filler to the first photosensitive glass paste, wherein the first photosensitive glass paste and the second photosensitive glass paste are exposed to light in the exposure step, the first photosensitive glass paste and the second photosensitive glass paste are developed in the development step, and the first photosensitive glass paste and the second photosensitive glass paste are hardened in the hardening step, and the longest length of the second filler is longer than 0 and equal to or shorter than the wavelength of the ultraviolet light.

[0110] (4) The method for manufacturing an optical coupler according to any one of (1) to (3), wherein the first filler includes a filler having a non-spherical shape.

[0111] (5) A method for manufacturing an optical coupler, comprising: a preparation step of preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction, the light-transmitting substrate including a third filler; a first application step of applying a first photosensitive glass paste to the first main surface; a masking step of arranging a grayscale mask formed with a binary pattern on the second main surface; an exposure step of irradiating the second main surface with ultraviolet light to expose the first photosensitive glass paste; a development step of removing the grayscale mask from the second main surface and developing the first photosensitive glass paste; and a curing step of removing the light-transmitting substrate from the developed first photosensitive glass paste and curing the first photosensitive glass paste, wherein the longest length of the third filler is longer than the wavelength of the ultraviolet light.

[0112] (6) The method for manufacturing an optical coupler according to (5), wherein the third filler includes a filler having a non-spherical shape.

[0113] (7) An optical coupler made of a first photosensitive glass paste containing a first filler, wherein the longest length of the first filler is longer than the wavelength of ultraviolet light irradiated onto a grayscale mask formed with a binary pattern.

[0114] (8) An optical coupler comprising: a first glass portion including a first glass and a first filler mixed in the first glass; and a second glass portion including at least a second glass and connected to the first glass portion, wherein the second glass portion includes the second filler mixed in the second glass, and the content of the second filler contained in the second glass portion is lower than the content of the first filler contained in the first glass portion; or the second glass portion does not include the second filler.

[0115] (9) An optical coupler comprising: a first glass portion; and a transmitting portion connected to the first glass portion; wherein the first glass portion includes glass and a first filler mixed in the glass; and the transmitting portion includes a medium and a second filler mixed in the medium; and wherein the longest length of the second filler is different from the longest length of the first filler.

[0116] (10) The optical coupler according to (9), wherein the medium is glass.

[0117] (11) The optical coupler according to any one of (7) to (10), wherein the first filler includes a filler having a non-spherical shape.

[0118] (12) The optical coupler according to (9) or (10), wherein the transmission portion is a light-transmitting substrate.

[0119] (13) The optical coupler according to (12), wherein the second filler includes a filler having a non-spherical shape.

[0120] (14) A photoelectric conversion circuit module comprising: an optical coupler according to any one of (7) to (13); a substrate; and an optical-electric conversion circuit mounted on the substrate, wherein the optical-electric conversion circuit converts an electrical signal into light incident on the optical coupler, or converts light emitted from the optical coupler into an electrical signal.

[0121] (15) The photoelectric conversion circuit module according to (14), wherein the substrate is a semiconductor substrate and includes a light emitting portion that emits light, and the optical coupler is mounted on the substrate.

[0122] (16) An optical transceiver comprising the optical coupler according to any one of (7) to (13).

[0123] DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c, 1d: Optical coupler 2: Holding portion 3: Reflecting portion 4: Optical fiber fixing portion 5: Optical fiber 10: Grayscale mask 11: Light-transmitting substrate 12: First photosensitive glass paste 13: Second photosensitive glass paste 15: Pixel 16: Unit area 17: Runner portion 21: First side wall portion 22: Second side wall portion 23: Third side wall portion 24: Bottom portion 31: Prism portion 32: Condenser lens portion 50, 50a: Photoelectric conversion circuit module 51: Substrate 52: Photoelectric conversion circuit 53: Light emitting portion 100: Optical transceiver A1, A2: Area A11, A12, A21, A22: Square-shaped portion DIR1: First direction DIR2: Second direction DIR3: Third direction G: Groove I: Light intensity L: Light M: Mirror M1: Glass M2: Medium OW: Optical waveguide P1: First filler P2: Second filler P3: Third filler S1: End face S11: Incident surface S12: Exit surface S2: Prism part incident surface S21: Mounting surface S3: Prism part reflecting surface S4: Prism part exit surface SU11: First main surface SU12: Second main surface UV: Ultraviolet light a: Light transmitting area b: Light blocking area

Claims

1. A method for manufacturing an optical coupler comprising: a preparation step of preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction; a first application step of applying a first photosensitive glass paste containing a first filler onto the first main surface; a masking step of arranging a grayscale mask formed in a binary pattern on the second main surface; an exposure step of irradiating the second main surface with ultraviolet light and exposing the first photosensitive glass paste to light; a development step of removing the grayscale mask from the second main surface and developing the first photosensitive glass paste; and a hardening step of removing the light-transmitting substrate from the developed first photosensitive glass paste and hardening the first photosensitive glass paste, wherein the longest length of the first filler is longer than the wavelength of the ultraviolet light.

2. A method for manufacturing an optical coupler as described in claim 1, further comprising a second coating step between the first coating step and the exposure step of coating a second photosensitive glass paste onto the first photosensitive glass paste, wherein the first photosensitive glass paste and the second photosensitive glass paste are exposed to light in the exposure step, the first photosensitive glass paste and the second photosensitive glass paste are developed in the development step, and the first photosensitive glass paste and the second photosensitive glass paste are hardened in the hardening step, the second photosensitive glass paste contains a second filler, and a content of the second filler contained in the second photosensitive glass paste is lower than a content of the first filler contained in the first photosensitive glass paste, or the second photosensitive glass paste does not contain the second filler.

3. A method for manufacturing an optical coupler as described in claim 1, further comprising a second application step between the first application step and the exposure step, of applying a second photosensitive glass paste containing a second filler to the first photosensitive glass paste, wherein the first photosensitive glass paste and the second photosensitive glass paste are exposed to light in the exposure step, the first photosensitive glass paste and the second photosensitive glass paste are developed in the development step, and the first photosensitive glass paste and the second photosensitive glass paste are hardened in the hardening step, and the longest length of the second filler is longer than 0 and equal to or shorter than the wavelength of the ultraviolet light.

4. The method for manufacturing an optical coupler according to any one of claims 1 to 3, wherein the first filler includes a filler having a non-spherical shape.

5. A method for manufacturing an optical coupler, comprising: a preparation step of preparing a light-transmitting substrate having a first main surface and a second main surface aligned in a first direction, the light-transmitting substrate including a third filler; a first application step of applying a first photosensitive glass paste to the first main surface; a masking step of arranging a grayscale mask formed with a binary pattern on the second main surface; an exposure step of irradiating the second main surface with ultraviolet light and exposing the first photosensitive glass paste to light; a development step of removing the grayscale mask from the second main surface and developing the first photosensitive glass paste; and a hardening step of removing the light-transmitting substrate from the developed first photosensitive glass paste and hardening the first photosensitive glass paste, wherein the longest length of the third filler is longer than the wavelength of the ultraviolet light.

6. The method for manufacturing an optical coupler according to claim 5, wherein the third filler includes a filler having a non-spherical shape.

7. An optical coupler made of a first photosensitive glass paste containing a first filler, wherein the maximum length of the first filler is longer than the wavelength of ultraviolet light irradiated onto a grayscale mask formed with a binary pattern.

8. An optical coupler comprising: a first glass part including a first glass and a first filler mixed within the first glass; and a second glass part including at least a second glass and connected to the first glass part, wherein the second glass part includes a second filler mixed within the second glass, and the content of the second filler contained in the second glass part is lower than the content of the first filler contained in the first glass part, or the second glass part does not include the second filler.

9. An optical coupler comprising: a first glass portion; and a transmissive portion connected to the first glass portion, wherein the first glass portion includes glass and a first filler mixed into the glass, and the transmissive portion includes a medium and a second filler mixed into the medium, and a maximum length of the second filler is different from a maximum length of the first filler.

10. The optical coupler according to claim 9, wherein the medium is glass.

11. The optical coupler according to any one of claims 7 to 10, wherein the first filler includes a filler having a non-spherical shape.

12. The optical coupler according to claim 9 or 10, wherein the transmitting portion is a light-transmitting substrate.

13. The optical coupler of claim 12, wherein the second filler comprises a filler having a non-spherical shape.

14. An optoelectronic conversion circuit module comprising: an optical coupler according to any one of claims 7 to 13; a substrate; and an optoelectronic conversion circuit mounted on the substrate, wherein the optoelectronic conversion circuit converts an electrical signal into light incident on the optical coupler, or converts light emitted from the optical coupler into an electrical signal.

15. The photoelectric conversion circuit module according to claim 14, wherein the substrate is a semiconductor substrate and includes a light emitting portion that emits light, and the optical coupler is mounted on the substrate.

16. An optical transceiver comprising an optical coupler according to any one of claims 7 to 13.

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