Optical connection member, optical connection structure, glass substrate, and methods for manufacturing optical connection member and glass substrate

Abstract

Provided is an optical connection member that makes it possible to improve productivity.　An optical connection member 1 according to the present invention is disposed between a first optical waveguide 5, and a second optical waveguide 6, a light-emitting element, or a light-receiving element, and optically connects the first optical waveguide 5 to the second optical waveguide 6, the light-emitting element, or the light-receiving element. The optical connection member comprises: a base member 2 which has a first surface 2a and a second surface 2b facing the first surface 2a, and which has provided therein at least one through-hole 2c that penetrates therethrough from the first surface 2a to the second surface 2b; and a reflection structure that is provided inside the through-hole 2c and that reflects light.

Description

Optical connecting member, optical connecting structure, glass substrate, and methods for manufacturing optical connecting member and glass substrate

[0001] The present invention relates to an optical connecting member, an optical connecting structure using the optical connecting member, a glass substrate used in the optical connecting member, and a method for manufacturing the optical connecting member and the glass substrate.

[0002] In recent years, to meet the needs for high-speed transmission and large capacity in optical communications, research and development has been conducted on compact, high-capacity optical transceivers using optical circuits that use silicon photonics (SiPh). Although there are various methods for optically coupling SiPh to optical fibers, a method that is as simple as possible and highly reliable is required.

[0003] Patent Document 1 listed below discloses an example of an optical connection structure in which two optical waveguides are optically connected by a resin core. In this optical connection structure, a resin core, a clad, and a spacer are arranged between the two optical waveguides. More specifically, the resin core abuts against the core of one optical waveguide and the core of the other optical waveguide. The periphery of the resin core is covered by the clad. A spacer is arranged around a portion of the periphery of the clad.

[0004] When manufacturing the optical connection structure of Patent Document 1, the end faces of two optical waveguides are abutted against a spacer, and then a photocurable resin is placed between the two optical waveguides. Next, the photocurable resin is cured by irradiating it with light from each optical waveguide. This forms a resin core. Next, after removing the uncured photocurable resin, a resin material for the cladding is placed between the end faces of the two optical waveguides and cured. This forms the cladding.

[0005] International Publication No. 2021 / 033217

[0006] However, the optical connection structure of Patent Document 1 requires the placement of a spacer, the formation of a resin core, and the formation of a cladding for each optical waveguide to be connected, which makes it difficult to achieve sufficiently high productivity.

[0007] An object of the present invention is to provide an optical connecting member, an optical connection structure, and a method for manufacturing an optical connecting member that can increase productivity.

[0008] Hereinafter, various aspects of an optical connecting member, an optical connection structure, a glass substrate, and a method for manufacturing an optical connecting member and a glass substrate that solve the above problems will be described.

[0009] The optical connecting member according to aspect 1 of the present invention is an optical connecting member that is arranged between a first optical waveguide and a second optical waveguide, a light-emitting element, or a light-receiving element, and optically connects the first optical waveguide and the second optical waveguide, the light-emitting element, or the light-receiving element, and is characterized by comprising: a base member having a first surface and a second surface opposite to the first surface, and having at least one through hole that penetrates from the first surface to the second surface; and a reflective structure that is provided within the through hole and reflects light.

[0010] In the optical connecting member of Aspect 2, it is preferable that an inorganic material is used as the material of the base member in Aspect 1. In this case, the weather resistance of the optical connecting member can be improved. This makes the optical connecting member less susceptible to deterioration even when used in a high-temperature, high-humidity environment, etc. This improves the long-term reliability of the optical connecting member.

[0011] In the optical connecting member of Aspect 3, in Aspect 2, the inorganic material is preferably one of glass and silicon. In this case, the thermal expansion coefficient of the base member can be reduced. This makes it possible to effectively reduce misalignment between the first optical waveguide and the second optical waveguide, the light-emitting element, or the light-receiving element even when temperature changes occur. This reduces the impact on the optical connection. Therefore, the reliability of the optical connecting member can be increased.

[0012] In the optical connecting member of Aspect 4, in Aspect 3, it is preferable that the inorganic material is glass, and the reflective structure includes a transparent material having a higher refractive index than the base member. In this case, since the inorganic material is glass, an inorganic member made of glass is processed to obtain the base member. By adjusting the components of the glass, it is possible to adjust the chemical resistance of the inorganic member. This makes it easy to adjust the etching rate when forming through holes in the base member by etching the inorganic member. As a result, it is easy to process the inorganic material. In addition, since the reflective structure includes a transparent material having a higher refractive index than the base member, light loss in the optical connecting member can be suitably reduced.

[0013] In the optical connecting member of Aspect 5, in Aspect 4, it is preferable that the transparent material is a photocurable resin or a thermosetting resin. In this case, a reflective structure can be easily provided, and the optical connecting member can be easily obtained.

[0014] In the optical connecting member of Aspect 6, in any one of Aspects 1 to 5, it is preferable that an inner wall of at least one of the through holes in the base member is inclined with respect to the normal direction of the first surface. In this case, the spot diameter of the emitted light can be reduced. As a result, when the first optical waveguide and the light-receiving element are optically connected, the light can be more reliably incident on the light-receiving element.

[0015] In the optical connecting member of Aspect 7, in any one of Aspects 1 to 6, it is preferable that the reflective structure has a reflective film. In this case, the optical connecting member can more reliably and effectively reduce light loss.

[0016] In the optical connecting member of aspect 8, in any one of aspects 1 to 7, the through holes may be provided in plurality, and on at least one of the first surface and the second surface, the portions where at least some of the through holes are open may be arranged so as to be positioned on a straight line.

[0017] In the optical connecting member of Aspect 9, in any one of Aspects 1 to 8, the thermal expansion coefficient of the base member is 30×10 －７ / ℃ or more, 70 x 10 －７ / °C or less. In this case, even when a temperature change occurs, it is possible to minimize the positional deviation between the first optical waveguide and the second optical waveguide, the light emitting element, or the light receiving element. This further reduces the influence on the optical connection. Therefore, the reliability of the optical connecting member can be further increased.

[0018] In the optical connecting member of Aspect 10, in any one of Aspects 1 to 9, at least a portion of the surface of the base member may be an etched surface. If the surface of the base member is an etched surface, microcracks that existed on the surface of the base member's original material before the etching process are removed. This prevents a decrease in the mechanical strength of the base member. In particular, this effect can be further enhanced when the base member is made of glass.

[0019] In the optical connecting member of Aspect 11, in any one of Aspects 1 to 10, it is preferable that a plurality of through holes are provided. In this case, it is possible to increase the capacity of optical communication by the optical connecting member. Here, it is preferable that the shape of the through hole in a plan view is circular or polygonal.

[0020] In the optical connecting member of Aspect 12, in Aspect 11, it is preferable that the plurality of through holes include at least two through holes having different shapes in a planar view. In this case, by making the shape of each through hole correspond to the light passing through the through hole, it is possible to improve the efficiency of optical coupling between optical waveguides, etc., by the optical connecting member. If the through holes have a circular shape in a planar view, it is preferable that the diameters of the through holes are different. If the plurality of through holes have a polygonal shape in a planar view, it is preferable that the shapes of at least two through holes are similar to each other in a planar view. Furthermore, the plurality of through holes may include a through hole having a circular shape in a planar view and a through hole having a polygonal shape.

[0021] In the optical connecting member of Aspect 13, in any one of Aspects 1 to 12, inner walls of the plurality of through holes of the base member are inclined with respect to a direction normal to the first surface, the plurality of through holes include first through holes and second through holes having different shapes in a plan view, and a value obtained by dividing an opening area of ​​the first through hole on the first surface side by an opening area of ​​the first through hole on the second surface side may be different from a value obtained by dividing an opening area of ​​the second through hole on the first surface side by an opening area of ​​the second through hole on the second surface side. Specifically, the value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the first through hole on the second surface side is preferably greater than or equal to 10 and less than 100, and the value obtained by dividing the opening area of ​​the second through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is preferably greater than or equal to 1.1 and less than 50. The value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the second surface side of the first through hole is more preferably 30 or more and 90 or less, and the value obtained by dividing the opening area of ​​the second through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is more preferably 1.5 or more and less than 30. The value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is even more preferably 50 or more and 80 or less, and the value obtained by dividing the opening area of ​​the second through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is even more preferably 1.1 or more and less than 10. In Aspect 13, the ratio of the opening area of ​​the first through hole to the opening area of ​​the second surface side and the ratio of the opening area of ​​the first through hole to the opening area of ​​the second through hole are different from each other. Thus, a single optical connecting member can be used for applications including, for example, multiple optical paths having different aspects.

[0022] An optical connection structure according to aspect 14 of the present invention comprises an optical connection member according to any one of aspects 1 to 13, the first optical waveguide, and an optical element including the second optical waveguide, wherein the optical connection member is disposed between the first optical waveguide and the optical element so that the first surface side faces the first optical waveguide, and the optical connection member optically connects the first optical waveguide and the second optical waveguide.

[0023] In the optical connection structure of Aspect 15, in Aspect 14, the second optical waveguide may be a silicon waveguide.

[0024] An optical connection structure according to aspect 16 of the present invention comprises an optical connection member according to any one of aspects 1 to 12, the first optical waveguide, and an optical element including the light-receiving element, wherein the optical connection member is arranged between the first optical waveguide and the optical element so that the first surface side faces the first optical waveguide, the optical connection member optically connects the first optical waveguide and the light-receiving element, the inner wall of at least one of the through holes in the base member is inclined with respect to the direction in which the first surface and the second surface face each other, and in at least one of the through holes, the opening area on the first surface side is larger than the opening area on the second surface side.

[0025] The optical connection structure of aspect 17 of the present invention comprises an optical connection member of any one of aspects 1 to 13, the first optical waveguide, and the light-emitting element, wherein the optical connection member is arranged between the first optical waveguide and the light-emitting element so that the first surface side faces the first optical waveguide, and the optical connection member optically connects the first optical waveguide and the light-emitting element.

[0026] In the optical connection structure of Aspect 18, in any of Aspects 14 to 17, the first optical waveguide may be an optical fiber.

[0027] A glass substrate according to a nineteenth aspect of the present invention has a first surface and a second surface opposite the first surface, and is provided with a plurality of through holes penetrating from the first surface to the second surface, the inner walls of the plurality of through holes being inclined with respect to a direction normal to the first surface, the plurality of through holes including first through holes and second through holes, wherein a value obtained by dividing an opening area of ​​the first through hole on the first surface side by an opening area of ​​the first through hole on the second surface side is different from a value obtained by dividing an opening area of ​​the second through hole on the first surface side by an opening area of ​​the second through hole on the second surface side. Specifically, the value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the first through hole on the second surface side is preferably 10 or more and 100 or less, and the value obtained by dividing the opening area of ​​the second through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is preferably 1.1 or more and less than 50. The value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is more preferably 30 or more and 90 or less, and the value obtained by dividing the opening area of ​​the second through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is more preferably 1.5 or more and less than 30. The value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is even more preferably 50 or more and 80 or less, and the value obtained by dividing the opening area of ​​the second through hole on the first surface side by the opening area of ​​the second through hole on the second surface side is even more preferably 1.1 or more and less than 10.

[0028] The method for manufacturing an optical connection member according to aspect 20 of the present invention is a method for manufacturing an optical connection member according to any one of aspects 1 to 13, and is characterized by comprising the steps of: modifying a part of an inorganic member made of glass by irradiating the inorganic member with laser light; and forming the through hole by etching the modified part of the inorganic member, thereby obtaining the base member.

[0029] A manufacturing method of an optical connecting member according to Aspect 21 of the present invention is the manufacturing method of an optical connecting member according to Aspect 13, and includes the steps of: preparing an inorganic member made of glass, having a third surface and a fourth surface opposite to the third surface; a first laser light irradiation step of irradiating the inorganic member with a laser light from the third surface side or the fourth surface side to form a first modified portion in a part of the inorganic member; a first etching step of etching the first modified portion to form a first recess for forming the first through hole; and a second etching step of irradiating the inorganic member with a laser light from the third surface side or the fourth surface side to form the first through hole. The method includes a second laser light irradiation step of forming a second modified region in a portion of the inorganic member other than the first recess, a second etching step of etching the second modified region to form a second recess for forming the second through hole, and a third etching step of etching the first recess and the second recess to form the first through hole and the second through hole, thereby obtaining the base member. The method is characterized in that the etching rate in the first etching step is different from the etching rates in the second etching step and the third etching step. In this case, the etching rate in the first etching step is preferably greater than the etching rates in the second etching step and the third etching step. This facilitates control of the value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the first through hole on the second surface side. Furthermore, the etching rates in the second etching step and the third etching step are preferably equal. This enables reduction in the cost of manufacturing the optical connecting member.

[0030] In the method for manufacturing a connecting member of Aspect 22, as in Aspect 21, the method further includes the steps of providing a protective sheet on the fourth surface of the inorganic member and peeling the protective sheet from the fourth surface of the inorganic member, and it is preferable that the first etching step and the second etching step are performed with the protective sheet provided on the fourth surface of the inorganic member, and the third etching step is performed after peeling the protective sheet from the fourth surface of the inorganic member. Here, the fourth surface of the inorganic member becomes the second surface of the base member in the optical connecting member, and the third surface of the inorganic member becomes the first surface of the base member in the optical connecting member. In Aspect 22, the diameters of the portions of the first through hole and the second through hole that open on the first surface and the second surface can be adjusted with high precision.

[0031] A method for manufacturing a glass substrate according to Aspect 23 of the present invention is the method for manufacturing a glass substrate according to Aspect 19, further comprising the steps of: preparing an inorganic member made of glass, the inorganic member having a third surface and a fourth surface opposite to the third surface; a first laser light irradiation step of irradiating the inorganic member with laser light from the third surface side or the fourth surface side to form a first modified portion in a part of the inorganic member; a first etching step of etching the first modified portion to form a first recess for forming the first through hole; and a second etching step of irradiating the inorganic member with laser light from the third surface side or the fourth surface side to form a first recess for forming the first through hole. The method includes a second laser light irradiation step of forming a second modified region in a portion of the inorganic member other than the first recess, a second etching step of etching the second modified region to form a second recess for forming the second through hole, and a third etching step of etching the first recess and the second recess to form the first through hole and the second through hole, wherein the etching rate in the first etching step is different from the etching rates in the second etching step and the third etching step. In this case, the etching rate in the first etching step is preferably greater than the etching rates in the second etching step and the third etching step. This makes it easy to control the value obtained by dividing the opening area of ​​the first through hole on the first surface side by the opening area of ​​the first through hole on the second surface side. Furthermore, it is preferable that the etching rates in the second etching step and the third etching step are equal. This makes it possible to reduce the cost of manufacturing the glass substrate.

[0032] According to the present invention, it is possible to provide an optical connecting member, an optical connection structure, a glass substrate, and a method for manufacturing an optical connecting member and a glass substrate, which can increase productivity.

[0033] FIG. 1 is a schematic cross-sectional view showing a portion of an example of an optical connection structure using an optical connecting member according to a first embodiment of the present invention. FIG. 2 is a schematic plan view showing an optical connecting member according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view taken along line II in FIG. 2. FIG. 4 is a schematic bottom view of an optical connecting member according to a first modified example of the first embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a cross section passing through a plurality of through holes of an optical connecting member in an example of an optical connection structure using an optical connecting member according to a first modified example of the first embodiment of the present invention. FIG. 6 is a schematic plan view of an optical connecting member according to a second modified example of the first embodiment of the present invention. FIGS. 7(a) to 7(c) are schematic cross-sectional views for explaining an example of a manufacturing method of the optical connecting member according to the first embodiment of the present invention. FIG. 8 is a schematic cross-sectional view showing a portion of an optical connecting member according to a second embodiment of the present invention, corresponding to the cross section taken along line II in FIG. 2. FIG. 9 is a schematic cross-sectional view showing a portion of an optical connecting member according to a modified example of the second embodiment of the present invention, corresponding to the cross section taken along line II in FIG. 2. FIG. 10 is a schematic cross-sectional view showing a portion of an optical connection structure according to a third embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing a portion of an optical connection structure according to a modified example of the third embodiment of the present invention. FIG. 12 is a schematic cross-sectional view showing a portion of an optical connection structure according to a fourth embodiment of the present invention. FIG. 13 is a schematic cross-sectional view showing a portion of an optical connection structure according to a fifth embodiment of the present invention. FIG. 14 is a schematic cross-sectional view showing a portion of an optical connecting member according to a sixth embodiment of the present invention, corresponding to the cross section along line II in FIG. 2. FIGS. 15(a) to 15(e) are schematic cross-sectional views for explaining an example of a manufacturing method for an optical connecting member according to the sixth embodiment of the present invention. FIGS. 16(a) to 16(e) are schematic cross-sectional views for explaining the third and fourth laser beam irradiation steps and the fourth to sixth etching steps in an example of a manufacturing method for an optical connecting member according to the sixth embodiment of the present invention. FIGS. 17(a) and 17(b) are schematic cross-sectional views for explaining the fifth laser beam irradiation step and the seventh etching step in an example of a manufacturing method for an optical connecting member according to the sixth embodiment of the present invention.

[0034] Hereinafter, embodiments of the present invention will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. Furthermore, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0035] (Optical connecting member) (First embodiment) Fig. 1 is a schematic cross-sectional view showing a part of an example of an optical connecting structure using an optical connecting member according to a first embodiment of the present invention. The dashed dotted line in Fig. 1 schematically shows the progression of light in an optical path.

[0036] 1 , the optical connecting member 1 is a member that optically connects a first optical waveguide 5 and a second optical waveguide 6. The optical connecting member 1 is disposed between the first optical waveguide 5 and the second optical waveguide 6. Specifically, it is preferable that the first optical waveguide 5 and the second optical waveguide 6 are made of, for example, a silicon waveguide or an optical fiber. The first optical waveguide 5 and the second optical waveguide 6 are included in, for example, an optical element.

[0037] In this specification, an optical element is an element that includes at least an optical waveguide, for example, a light-emitting element, a light-receiving element, or an integrated circuit. More specifically, it is preferable to use silicon photonics or an element in which an optical circuit is provided on a glass substrate as the optical element. It is preferable to use, for example, a photodiode or a phototransistor as the light-receiving element. It is preferable to use, for example, a light-emitting diode or a laser diode as the light-emitting element.

[0038] The optical connecting member 1 may optically connect the first optical waveguide 5 and the light receiving element. In this case, the optical connecting member 1 may be disposed between the first optical waveguide 5 and the light receiving element.

[0039] The specific configuration of the optical connecting member 1 of this embodiment will be described below. Fig. 2 is a schematic plan view showing the optical connecting member according to the first embodiment. Fig. 3 is a schematic cross-sectional view taken along line II in Fig. 2. The cross section of the optical connecting member 1 shown in Fig. 1 is taken along line II-II in Fig. 2.

[0040] As shown in Fig. 2, the optical connecting member 1 has a base member 2. In the present invention, the material of the base member 2 is preferably an inorganic material. It is more preferable that the inorganic material used for the base member 2 is glass. A preferred example of glass used as the material for the base member 2 is borosilicate glass. However, the material used for the base member 2 may also be, for example, silicon.

[0041] As shown in Fig. 3, the base member 2 has a first surface 2a and a second surface 2b. The first surface 2a and the second surface 2b face each other. When the optical connecting member 1 is used, the first surface 2a of the first surface 2a and the second surface 2b faces the first optical waveguide 5 shown in Fig. 1. The second surface 2b faces the second optical waveguide 6 or the light-receiving element.

[0042] 3 , the base member 2 has a plate-like shape. The first surface 2 a and the second surface 2 b of the base member 2 have a rectangular shape. However, the shapes of the first surface 2 a and the second surface 2 b are not limited to the above.

[0043] A plurality of through holes 2c are provided in the base member 2. Specifically, the plurality of through holes 2c penetrate from the first surface 2a to the second surface 2b. As shown in FIG. 2 , in this embodiment, the portions of the first surface 2a where all of the through holes 2c are open are arranged in a row. More specifically, the portions of the first surface 2a where all of the through holes 2c are open are arranged so as to be positioned on a single straight line. Although not shown, the portions of the second surface 2b where all of the through holes 2c are open are also arranged so as to be positioned on a single straight line. Note that the arrangement of the through holes 2c is not limited to the above. It is sufficient that at least one through hole 2c is provided in the base member 2.

[0044] 3, the inner walls of the plurality of through holes 2c in the base member 2 are inclined with respect to the normal direction of the first surface 2a. In each through hole 2c, the opening area on the first surface 2a side is larger than the opening area on the second surface 2b side. However, the inner walls of the plurality of through holes 2c in the base member 2 may extend parallel to the normal direction of the first surface 2a. That is, in each through hole 2c, the opening area on the first surface 2a side and the opening area on the second surface 2b side may be the same.

[0045] In this embodiment, the shape of the through hole 2c in the base member 2 in a plan view is circular. When the shape of the through hole 2c in a plan view is circular, the diameter of the through hole 2c can be, for example, 10 μm or more and 100 μm or less. Note that the shape of the through hole 2c in a plan view is not limited to a circular shape. The dimension of the base member 2 along the normal direction to the first surface 2a is not particularly limited, but can be, for example, 100 μm or more and 500 μm or less.

[0046] A reflective structure is provided inside the through-hole 2c of the base member 2. Specifically, the reflective structure is a structure that reflects light. In this embodiment, the reflective structure has a reflective film 4. More specifically, the reflective structure is configured by providing the reflective film 4 on the inner wall of the through-hole 2c of the base member 2.

[0047] The reflective film 4 may be, for example, a metal film or a dielectric multilayer film. The material of the metal film is not particularly limited, but metals such as aluminum and silver can be used. The thickness of the reflective film 4 is not particularly limited, but may be, for example, 0.05 μm or more and 2 μm or less.

[0048] 3 indicates the direction of light guide in the optical connecting member 1. In this embodiment, the direction of light guide in the optical connecting member 1 is parallel to the normal direction of the first surface 2a of the base member 2. However, depending on the object to be optically connected using the optical connecting member 1, the direction of light guide in the optical connecting member 1 may be inclined with respect to the normal direction of the first surface 2a.

[0049] In the example shown in Fig. 1, a first optical waveguide 5 and a second optical waveguide 6 are optically connected by an optical connecting member 1. The element shown by a simplified rectangular shape in Fig. 1 is a grating coupler 8. This is also true for the other simplified cross-sectional views. The grating coupler 8 switches the direction of travel of light.

[0050] For example, when light is emitted from the second optical waveguide 6, the light is incident on the grating coupler 8. The light emitted from the grating coupler 8 passes through the through hole 2c in the base member 2 and is incident on the first optical waveguide 5. At this time, at least a part of the light heading toward the inner wall of the through hole 2c in the base member 2 is reflected by the reflective structure and is incident on the first optical waveguide 5. This makes it possible to reduce the loss of light transmitted from the second optical waveguide 6 to the first optical waveguide 5. Note that the manner of optical connection between the first optical waveguide 5 and the second optical waveguide 6 and the direction of light transmission are not limited to those described above.

[0051] A feature of this embodiment is that, as shown in FIG. 2, a through hole 2c is provided in the base member 2, and a reflective structure is provided within the through hole 2c. This allows the optical connecting member 1 to be an independent member with low loss in optical transmission. For example, when optical waveguides are optically connected to each other, the optical connecting member 1 can be placed between the optical waveguides. This eliminates the need for complicated processes such as multiple repetitions of curing and removing resin between the optical waveguides. Therefore, the productivity of the optical connection structure can be effectively increased.

[0052] As in this embodiment, it is preferable that a plurality of through holes 2c are provided in the base member 2, and a reflective structure is provided in each through hole 2c. In this case, even when multiple pairs of first optical waveguides 5 and second optical waveguides 6 are provided as shown in FIG. 1, for example, the optical connecting member 1 can be disposed between the multiple first optical waveguides 5 and the multiple second optical waveguides 6. When manufacturing the optical connecting member 1, multiple through holes 2c can be provided in the base member 2 according to the positions of the multiple pairs of first optical waveguides 5 and second optical waveguides 6 to be optically connected. This eliminates the need for a complicated process for optically connecting each of the first optical waveguides 5 and second optical waveguides 6. Therefore, the productivity of the optical connection structure can be further improved. The same applies to optically connecting multiple pairs of first optical waveguides 5 and light-emitting elements, or optically connecting multiple pairs of first optical waveguides 5 and light-receiving elements.

[0053] It is preferable that, on at least one of the first surface 2 a and the second surface 2 b, the open portions of at least some of all of the through holes 2 c are arranged so as to be positioned on a straight line. This allows for suitable optical connection between multiple pairs of first optical waveguides 5 and second optical waveguides 6 when at least one of the multiple first optical waveguides 5 and the multiple second optical waveguides 6 is arranged so as to be positioned on a straight line. The same applies when at least one of the multiple first optical waveguides 5 and the multiple light-emitting elements is arranged so as to be positioned on a straight line. The same applies when at least one of the multiple first optical waveguides 5 and the multiple light-receiving elements is arranged so as to be positioned on a straight line.

[0054] For example, the portions of the first surface 2 a where the plurality of through holes 2 c are open may be arranged in two rows. In this case, the portions of the first surface 2 a where some of the plurality of through holes 2 c are open are arranged to be positioned on one straight line, and the portions of the first surface 2 a where the remaining plurality of through holes 2 c are open are arranged to be positioned on another straight line. As a result, when the plurality of first optical waveguides 5 are arranged in two rows, it is possible to suitably optically connect multiple pairs of first optical waveguides 5 and second optical waveguides 6, multiple pairs of first optical waveguides 5 and light-emitting elements, or multiple pairs of first optical waveguides 5 and light-receiving elements.

[0055] As in this embodiment, it is preferable that an inorganic material is used for the base member 2. In this case, the weather resistance of the optical connecting member 1 can be improved. This makes the optical connecting member 1 less likely to deteriorate even when used in a high-temperature and high-humidity environment. This improves the long-term reliability of the optical connecting member 1.

[0056] It is more preferable that glass is used as the material for the base member 2. In this case, the thermal expansion coefficient of the base member 2 can be reduced. This makes it possible to effectively reduce misalignment between the first optical waveguide 5 and the second optical waveguide 6, the light-emitting element, or the light-receiving element, even when a temperature change occurs. This makes it possible to reduce misalignment, etc. that affects the optical connection when a temperature change occurs. Therefore, the reliability of the optical connecting member 1 can be effectively increased.

[0057] The thermal expansion coefficient of the base member 2 is 30×10 －７ / ℃ or more, 70 x 10 －７ / °C or less. This can further reduce positional deviations that affect optical connections when temperature changes occur. Therefore, the reliability of the optical connecting member 1 can be further increased.

[0058] It should be noted that even when silicon is used as the material of the base member 2, it is possible to effectively reduce the thermal expansion coefficient of the base member 2. This makes it possible to increase the reliability of the optical connecting member 1.

[0059] The light guide direction in the optical connecting member 1 is parallel to the normal direction of the first surface 2a. That is, the through hole 2c in the base member 2 extends parallel to the normal direction of the first surface 2a. However, the light guide direction in the optical connecting member 1 may be inclined with respect to the normal direction of the first surface 2a. That is, the through hole 2c in the base member 2 may extend at an angle with respect to the normal direction of the first surface 2a.

[0060] In the base member 2 of this embodiment, the multiple through holes 2c all have a circular shape in a plan view. The multiple through holes 2c have the same diameter. More specifically, the diameters of the portions of the multiple through holes 2c that open to the first surface 2a are the same. The diameters of the portions of the multiple through holes 2c that open to the second surface 2b are also the same. Note that the multiple through holes 2c may include at least two through holes 2c with different diameters. More specifically, the multiple through holes 2c may include at least two through holes 2c in which at least one of the diameters of the portions that open to the first surface 2a and the diameters of the portions that open to the second surface 2b are different from each other. This example is shown as a first modified example of the first embodiment.

[0061] (First Modification) Fig. 4 is a schematic bottom view of an optical connecting member according to a first modification of the first embodiment. Fig. 5 is a schematic cross-sectional view showing a cross section passing through a plurality of through holes of the optical connecting member in an example of an optical connection structure using the optical connecting member according to the first modification of the first embodiment. The arrows in Fig. 5 indicate the direction in which light travels.

[0062] 4, the base member 2A has four through holes 2c1 and four through holes 2c2. The through holes 2c1 and 2c2 are both circular in plan view. However, the through holes 2c1 and 2c2 have different diameters.

[0063] 5, light passes from grating coupler 8 through through hole 2c1 in base member 2A and enters first optical waveguide 5. As in the example shown in Fig. 1, a reflective film 9 is provided on a portion of first optical waveguide 5. Light that enters first optical waveguide 5 is reflected by reflective film 9 and is suitably guided in first optical waveguide 5. Diameter D1 of the incident side of through hole 2c1 is diameter D1 of the portion of through hole 2c1 that opens to second surface 2b.

[0064] Meanwhile, light passes from the first optical waveguide 5 through the through hole 2c2 in the base member 2A and enters the grating coupler 8. The diameter D2 on the exit side of the through hole 2c2 is the diameter D2 of the portion of the through hole 2c2 that opens to the second surface 2b, where D1≠D2.

[0065] 5, the direction of travel of light passing through through hole 2c1 in base member 2A is different from the direction of travel of light passing through through hole 2c2. The diameter or angle of light passing through through hole 2c1 may differ from the diameter or angle of light passing through through hole 2c2. In such cases, it is preferable to design each through hole to have a shape that corresponds to the light passing through that through hole. This makes it possible to improve the efficiency of optical coupling by optical connecting member 1A.

[0066] The number of locations where the through holes 2c1 are provided, the number of locations where the through holes 2c2 are provided, and the total number of locations where the through holes 2c1 and the through holes 2c2 are provided can be adjusted as appropriate.

[0067] When optically connecting the first optical waveguide 5 and the second optical waveguide 6, the optical connecting member 1A may be disposed between the first optical waveguide 5 and the second optical waveguide 6. Therefore, similar to the first embodiment, the productivity of the optical connection structure can be effectively increased.

[0068] 5, the inner walls of through holes 2c1 and 2c2 in base member 2A are inclined with respect to the normal direction to first surface 2a. However, for example, the inner walls of through holes 2c1 and 2c2 in base member 2A may extend parallel to the normal direction to first surface 2a, and the inner walls of through holes 2c2 may be inclined with respect to the normal direction to first surface 2a. Alternatively, the inner walls of through holes 2c1 and 2c2 in base member 2A may extend parallel to the normal direction to first surface 2a, and the diameters of through holes 2c1 and 2c2 may be different from each other.

[0069] In the first embodiment and its first modified example, the shape of each of the plurality of through holes in a plan view is circular. The shape of each of the plurality of through holes in a plan view may be the same polygon. In this case, the shapes of at least two of the through holes in a plan view may be similar to each other. More specifically, the plurality of through holes may include at least two through holes in which at least one of the shape of a portion opening on the first surface of the base member and the shape of a portion opening on the second surface of the base member is similar to each other.

[0070] Alternatively, the plurality of through holes may include at least two through holes having different shapes in a plan view, as will be described as a second modified example of the first embodiment.

[0071] (Second Modification) FIG. 6 is a schematic plan view of an optical connecting member according to a second modification of the first embodiment.

[0072] The base member 2B has four through holes 2c3 and four through holes 2c4. The through holes 2c3 have a circular shape in a plan view. The through holes 2c4 have a polygonal shape in a plan view. Specifically, the through holes 2c4 have a rectangular shape in a plan view.

[0073] 1, the optical connecting member 1B may be disposed between the first optical waveguide 5 and the second optical waveguide 6. This effectively increases the productivity of the optical connection structure, as in the first embodiment.

[0074] An example of a method for manufacturing the optical connecting member 1 according to the first embodiment will be described below.

[0075] (Manufacturing Method) FIGS. 7A to 7C are schematic cross-sectional views for explaining an example of a manufacturing method for the optical connecting member according to the first embodiment.

[0076] As shown in FIG. 7( a), an inorganic member 7 made of glass is prepared. The inorganic member 7 has a first surface 7 a and a second surface 7 b. The first surface 7 a and the second surface 7 b face each other. Next, the inorganic member 7 is irradiated with laser light L from the first surface 7 a side. Note that the irradiation with laser light L may also be performed from the second surface 7 b side of the inorganic member 7. By irradiating with laser light L, a portion of the inorganic member 7 is modified. By repeating this process, multiple locations of the inorganic member 7 are modified.

[0077] However, when manufacturing the optical connecting member of the present invention, it is sufficient to irradiate at least one location on the inorganic member with laser light depending on the object to be optically connected using the optical connecting member, thereby modifying at least one location on the inorganic member.

[0078] Next, the modified portion of the inorganic member 7 shown in Fig. 7(a) is subjected to an etching treatment, thereby forming a through hole 2c and obtaining a base member 2 as shown in Fig. 7(b).

[0079] 7(c), a reflective film 4 is formed inside the through-hole 2c of the base member 2. The reflective film 4 can be formed by, for example, sputtering or vacuum deposition. When the inner wall of the through-hole 2c in the base member 2 is inclined with respect to the normal direction of the first surface 2a, it is particularly easy to form the reflective film 4 by sputtering or vacuum deposition. Alternatively, when a metal film is formed as the reflective film 4, the reflective film 4 may be formed by plating.

[0080] The optical connecting member 1 is obtained in this manner. In this manner, the optical connecting member 1 can be easily manufactured. For example, when optically connecting the first optical waveguide 5 and the second optical waveguide 6 shown in FIG. 1 , the optical connecting member 1 can be disposed between the first optical waveguide 5 and the second optical waveguide 6. On the other hand, when optically connecting the first optical waveguide 5 and the light-receiving element, the optical connecting member 1 can be disposed between the first optical waveguide 5 and the light-receiving element. Therefore, the productivity of the optical connection structure can be effectively increased.

[0081] As described above, it is preferable that glass be used as the material for the base member 2. In this case, the chemical resistance of the inorganic member 7 can be adjusted by adjusting the components of the glass. This makes it easy to adjust the etching rate when forming the through-holes 2c in the base member 2 by etching the inorganic member 7. As a result, the inorganic member 7 can be easily processed.

[0082] Incidentally, the inorganic member 7 shown in Fig. 7(a) is irradiated with laser light L from the normal direction of the first surface 7a. However, for example, the inorganic member 7 may be irradiated with laser light L from a direction inclined with respect to the normal direction of the first surface 7a. In this case, the through hole 2c shown in Fig. 7(b) can be formed to extend at an angle with respect to the normal direction of the first surface 2a. This allows the light guide direction in the optical connecting member 1 to be inclined with respect to the normal direction of the first surface 2a.

[0083] The optical connecting member 1 may be obtained by singulating the base member 2 as a substrate. More specifically, the inorganic member 7 shown in FIG. 7(a) may be a substrate made of an inorganic material. In this case, the base member 2 obtained by forming the through-holes 2c is a substrate, as shown in FIG. 7(b). Then, the base member 2 may be singulated after providing the reflective film 4 shown in FIG. 7(c). This allows multiple optical connecting members 1 to be obtained at one time. Therefore, the productivity of the optical connecting member 1 can be further increased. This also allows the productivity of the optical connection structure to be further increased.

[0084] The method for forming the through-holes 2c of the base member 2 is not limited to the above. For example, the through-holes 2c may be formed using a drill or the like.

[0085] In the above example, glass is used as the material for the base member 2. However, silicon may also be used as the material for the base member 2. In this case, it is sufficient to prepare an inorganic member 7 made of silicon.

[0086] Hereinafter, examples of the optical connecting member according to the present invention other than the first embodiment will be described.

[0087] (Optical Connecting Member) (Second Embodiment) FIG. 8 is a schematic cross-sectional view showing a portion of an optical connecting member according to a second embodiment, which corresponds to the cross section taken along line II in FIG.

[0088] This embodiment differs from the first embodiment in that the reflective structure 13 has a transparent material 17 in addition to the reflective film 4. The transparent material 17 is filled in the through-hole 2c of the base member 2. The reflective film 4 is positioned around the transparent material 17. Except for the above points, the optical connecting member 11 of this embodiment has the same configuration as the optical connecting member 1 of the first embodiment.

[0089] The refractive index of the transparent material 17 is higher than that of the base member 2. More specifically, the refractive index of the transparent material 17 is higher than that of glass, which is the material of the base member 2. In this embodiment, the transparent material is a photocurable resin. As the photocurable resin, for example, an acrylate-based ultraviolet curable resin or an epoxy-based ultraviolet curable resin is preferably used. Alternatively, a thermosetting resin may be used as the transparent material 17.

[0090] When manufacturing the optical connecting member 11 of this embodiment, the through-holes 2c are formed in the base member 2, and then the through-holes 2c are filled with a photocurable resin. More specifically, the reflective film 4 is formed in the through-holes 2c, and then the through-holes 2c are filled with a photocurable resin. The photocurable resin is then photocured. In this way, the reflective structure 13 can be easily formed, and the optical connecting member 11 can be easily obtained.

[0091] When optical waveguides are to be optically connected to each other, the optical connecting member 11 may be disposed between the optical waveguides. Alternatively, when an optical waveguide and a light receiving element are to be optically connected to each other, the optical connecting member 11 may be disposed between the optical waveguide and the light receiving element. In this embodiment, as in the first embodiment, the productivity of the optical connection structure can be effectively increased.

[0092] It should be noted that the reflective structure 13 in the optical connecting member 11 does not necessarily have to have the reflective film 4. This example will be shown as a modified example of the second embodiment.

[0093] (Modification) FIG. 9 is a schematic cross-sectional view showing a portion of an optical connecting member according to a modification of the second embodiment, which corresponds to the cross section taken along line II in FIG.

[0094] In this modification, the reflective structure 13A has a transparent material 17 and does not have a reflective film 4. The refractive index of the transparent material 17 is higher than the refractive index of the base member 2. This allows light to be suitably reflected at the interface between the transparent material 17 and the base member 2. This allows light loss to be suitably reduced in the optical connecting member 11A. In this modification as well, the productivity of the optical connecting structure can be increased, as in the second embodiment.

[0095] However, it is preferable that the reflective structure 13A has a reflective film 4. This makes it possible to more reliably and effectively reduce the loss of light in the optical connecting member 11A.

[0096] The optical connecting member according to the present invention is used in an optical connection structure. Examples of the optical connection structure according to the present invention will be described below.

[0097] (Optical connection structure) (Third embodiment) Fig. 10 is a schematic cross-sectional view showing a part of an optical connection structure according to a third embodiment. In Fig. 10, the light-emitting element is shown as a schematic diagram in which two diagonal lines are added to a rectangle. The dashed dotted line in Fig. 10 schematically shows the progression of light in the optical path. The same applies to schematic cross-sectional views other than Fig. 10.

[0098] The optical connection structure 20 has an optical connecting member 21 and multiple pairs of first optical waveguides 25 and second optical waveguides 26. The cross section of the optical connecting member 21 shown in Fig. 10 is a cross section of a portion corresponding to the cross section along line II-II in Fig. 2. The same applies to schematic cross-sectional views other than Fig. 10. In the optical connection structure 20, first optical waveguides 25 and second optical waveguides 26 similar to the first optical waveguide 25 and second optical waveguide 26 shown in Fig. 10 are lined up in the depth direction in Fig. 10.

[0099] Plural pairs of first optical waveguides 25 and second optical waveguides 26 are optically connected by the optical connecting member 21. However, it is sufficient that the optical connection structure 20 has at least one pair of the first optical waveguide 25 and the second optical waveguide 26.

[0100] The optical connecting member 21 differs from the optical connecting member 1 according to the first embodiment in that the inner wall of the through hole 2c in the base member 2 extends parallel to the normal direction of the first surface 2a. Except for the above-mentioned point, the optical connecting member 21 has the same configuration as the optical connecting member 1 according to the first embodiment. The configuration of the optical connecting member 21 used in the optical connection structure 20 is not particularly limited. It is sufficient that the optical connecting structure 20 uses the optical connecting member according to the present invention.

[0101] In this embodiment, the first optical waveguide 25 is an optical fiber. The first optical waveguide 25 is included in the optical element 22A. The optical element 22A is an element for transmitting light. The optical element 22A has a substrate 23. The substrate 23 is provided with a plurality of grooves 23a aligned in the depth direction in FIG. 10. Each of the first optical waveguides 25 is embedded in each of the grooves 23a. The substrate 23 can be made of a material such as glass, ceramic, or silicon.

[0102] In this embodiment, the second optical waveguide 26 is a silicon waveguide. The second optical waveguide 26 is included in the optical element 22B. The optical element 22B is silicon photonics. The optical element 22B has a substrate 24 made of silicon. A plurality of second optical waveguides 26 are provided in the substrate 24 and aligned in the depth direction in FIG. 10 .

[0103] In addition to the plurality of second optical waveguides 26, the optical element 22B has a light-emitting element 27 and a plurality of grating couplers 8 lined up in the depth direction in FIG. 10 . The light-emitting element 27 in this embodiment is a laser diode. However, the light-emitting element 27 is not limited to a laser diode. The plurality of second optical waveguides 26 are optically connected to the same light-emitting element 27. Each second optical waveguide 26 optically connects the light-emitting element 27 and each grating coupler 8.

[0104] More specifically, a recess 24a is provided in the substrate 24. A light emitting element 27 is provided in the recess 24a. Each grating coupler 8 is connected to a corresponding second optical waveguide 26. The plurality of grating couplers 8 and the plurality of second optical waveguides 26 are aligned in the depth direction in FIG. 10 .

[0105] The configuration of the optical element 22B is not limited to the above. For example, the optical element 22B may have a plurality of light-emitting elements 27. For example, one second optical waveguide 26 may be optically connected to one light-emitting element 27.

[0106] The optical connecting member 21 is disposed between the first optical waveguide 25 and the optical element 22B. More specifically, the optical connecting member 21 is disposed so that the first surface 2a side of the base member 2 of the optical connecting member 21 faces the first optical waveguide 25. More specifically, the optical connecting member 21 is disposed between the first optical waveguide 25 and the grating coupler 8. The optical connecting member 21 and the grating coupler 8 are disposed between the first optical waveguide 25 and the second optical waveguide 26 in the optical circuit.

[0107] In the optical connection structure 20, light emitted from the light-emitting element 27 in the optical element 22B passes through the second optical waveguide 26 and enters the grating coupler 8. The light is emitted from the grating coupler 8 to the optical connecting member 21. The light passes through the optical connecting member 21 and enters the first optical waveguide 25.

[0108] In this embodiment, in the optical fiber serving as the first optical waveguide 25, the portion where light is incident and the end face are different portions. At least the vicinity of the portion where light is incident in the first optical waveguide 25 has a planar shape. In the first optical waveguide 25, the end face is inclined with respect to a direction perpendicular to the planar portion where light is incident. A reflective film 9 is provided on the end face of the first optical waveguide 25. Light incident on the first optical waveguide 25 is reflected by the reflective film 9 and is suitably guided in the first optical waveguide 25.

[0109] However, the arrangement of the first optical waveguide 25 and the configuration near the end face are not limited to the above. For example, the first optical waveguide 25 may be arranged so that light is incident from the end face of the first optical waveguide 25. In this case, the reflective film 9 is not provided on the end face of the first optical waveguide 25.

[0110] To obtain the optical connection structure 20, the optical connecting member 21 is simply placed between the first optical waveguide 25 and the optical element 22B. This allows the first optical waveguide 25 and the second optical waveguide 26 to be optically connected via the optical connecting member 21 and the grating coupler 8. Therefore, no complicated steps are required to optically connect the first optical waveguide 25 and the second optical waveguide 26. This makes it possible to effectively increase the productivity of the optical connection structure 20.

[0111] The optical elements 22A and 22B may be bonded to the optical connecting member 21 with an adhesive or the like, which makes it possible to easily fix the optical elements 22A and 22B to the optical connecting member 21.

[0112] An appropriate support may be provided between the optical element 22A and the optical element 22B. This allows the support and the optical connecting member 21 to suitably support the optical element 22A and the optical element 22B.

[0113] In this embodiment, the through-hole 2c in the base member 2 extends parallel to the normal direction of the first surface 2a. Note that the extension direction of the through-hole 2c may be inclined with respect to the normal direction of the first surface 2a, depending on the direction of the light emitted from the grating coupler 8.

[0114] However, in this embodiment, the reflective structure has a reflective film 4. This makes it possible to more reliably and effectively reduce light loss in the optical connecting member 21 regardless of the direction of light emitted from the grating coupler 8. Therefore, it is not necessary to change the direction in which the through holes 2c extend depending on the direction of light emitted from the grating coupler 8. In other words, it is not necessary to change the manufacturing conditions when forming the through holes 2c. This makes it possible to further increase the productivity of the optical connecting member 21. This also makes it possible to further increase the productivity of the optical connection structure 20.

[0115] In addition, in the optical element 22B, a light receiving element may be arranged instead of the light emitting element 27 or the grating coupler 8. In these cases, the light emitted from the first optical waveguide 25 passes through the optical connecting member 21 and enters the light receiving element.

[0116] Alternatively, the optical element 22B may have both the light-emitting element 27 and the light-receiving element. In this case, light is emitted from some of the first optical waveguides 25, and light is incident on the remaining first optical waveguides 25.

[0117] The optical fiber serving as the first optical waveguide 25 does not necessarily have to be included in the optical element 22A. In this case, it is sufficient that the first optical waveguide 25 is appropriately held so that the first optical waveguide 25 is connected to the optical connecting member 21. Holding here refers to suppressing movement in three dimensions, movement only in two dimensions, or movement only in one dimension.

[0118] For example, the first optical waveguide 25 may be configured so that light is incident from an end face of the first optical waveguide 25. This example will be shown as a modification of the third embodiment.

[0119] (Modification) FIG. 11 is a schematic cross-sectional view showing a part of an optical connection structure according to a modification of the third embodiment.

[0120] The first optical waveguide 25 in this modified example is an optical fiber. The first optical waveguide 25 is not included in the optical element. However, the first optical waveguide 25 is held in a portion not shown. The optical fiber serving as the first optical waveguide 25 may be bent as appropriate. This modified example differs from the third embodiment in the arrangement of the first optical waveguide 25, the direction in which the end face of the first optical waveguide 25 extends, and the fact that a reflective film is not provided on the end face. This modified example also differs from the third embodiment in that the first optical waveguide 25 is not included in the optical element. Other than the above points, the optical connection structure 20A of this modified example has the same configuration as the optical connection structure 20 of the third embodiment.

[0121] The end face of the first optical waveguide 25 extends in a direction perpendicular to the direction in which light is guided in the portion near the end face of the first optical waveguide 25. Note that the direction in which the end face extends is not limited to the above. The end face of the first optical waveguide 25 is arranged so as to cover the portion where the through hole 2c is opened on the first surface 2a of the base member 2 of the optical connecting member 21. This allows light to be incident from the end face of the first optical waveguide 25. As with the third embodiment, in this modified example, the productivity of the optical connection structure 20A can be effectively increased.

[0122] The first optical waveguide 25, the optical element 22B, and the optical connecting member 21 may be joined by an adhesive or the like, which makes it possible to easily fix the first optical waveguide 25, the optical element 22B, and the optical connecting member 21.

[0123] The portion that holds the first optical waveguide 25 may be provided on the first surface 2 a of the base member 2 in the optical connecting member 21 , for example.

[0124] In addition, a light receiving element may be arranged in the optical element 22B instead of the light emitting element 27 or the grating coupler 8. In these cases, light emitted from the end face of the first optical waveguide 25 is incident on the light receiving element. Alternatively, the optical element 22B may have both the light emitting element 27 and the light receiving element.

[0125] 12 is a schematic cross-sectional view showing a part of an optical connection structure according to a fourth embodiment. In Fig. 12, the light receiving element is shown as a rectangle with two diagonal lines added.

[0126] This embodiment differs from the third embodiment in that the optical connecting member 1 has the same configuration as that of the first embodiment. This embodiment also differs from the third embodiment in that the optical connecting member 1 optically connects multiple pairs of first optical waveguides 25 and light-receiving elements 37, and in the configuration of the optical element 32B. Except for the above points, the optical connection structure 30 of this embodiment has the same configuration as the optical connection structure 20 of the third embodiment.

[0127] The optical element 32B has a substrate 34 and a plurality of light receiving elements 37 arranged in the depth direction in Fig. 12. The substrate 34 has a plurality of recesses 34a arranged in the depth direction in Fig. 12. Each light receiving element 37 is provided in each recess 34a.

[0128] The optical connecting member 1 is disposed between the first optical waveguide 25 and the optical element 32B so that the first surface 2a of the base member 2 faces the first optical waveguide 25. More specifically, the optical connecting member 1 is disposed between the first optical waveguide 25 and the light-receiving element 37. In the optical connection structure 30, light emitted from the first optical waveguide 25 passes through the optical connecting member 1 and enters the light-receiving element 37.

[0129] To obtain the optical connection structure 30, the optical connecting member 1 is simply placed between the first optical waveguide 25 and the optical element 32B. This allows the first optical waveguide 25 and the light-receiving element 37 to be optically connected by the optical connecting member 1. Therefore, no complicated steps are required to optically connect the first optical waveguide 25 and the light-receiving element 37. This makes it possible to effectively increase the productivity of the optical connection structure 30.

[0130] In the optical connecting member 1, the inner wall of the through hole 2c in the base member 2 is inclined with respect to the normal direction of the first surface 2a. The opening area of ​​the through hole 2c on the first surface 2a side is larger than the opening area on the second surface 2b side. This makes it possible to reduce the spot diameter of the light emitted to the second surface 2b side. This allows the light to be more reliably incident on the light receiving element 37.

[0131] Fifth Embodiment FIG. 13 is a schematic cross-sectional view showing a part of an optical connection structure according to a fifth embodiment.

[0132] The optical connecting member 41 in the optical connection structure 40 optically connects the element and the optical waveguide in one optical element 42. Specifically, in this embodiment, the optical element 42 is silicon photonics. The optical element 42 includes a substrate 24, a light-emitting element 27, and a first optical waveguide 45. A recess 24a is provided in the substrate 24. The light-emitting element 27 is provided in the recess 24a. In this embodiment, the light-emitting element 27 is a laser diode. In this embodiment, the first optical waveguide 45 is a silicon waveguide.

[0133] The optical connecting member 41 is disposed between the first optical waveguide 45 and the light-emitting element 27 so that the first surface 2a side faces the first optical waveguide 45. The optical connecting member 41 optically connects the first optical waveguide 45 and the light-emitting element 27.

[0134] To obtain the optical connection structure 40, the optical connecting member 41 is simply placed between the first optical waveguide 45 and the light emitting element 27. This optically connects the first optical waveguide 45 and the light emitting element 27. Therefore, no complicated steps are required to optically connect the first optical waveguide 45 and the light emitting element 27. Therefore, the productivity of the optical connection structure 40 can be effectively increased.

[0135] In the base member 2 of the optical connecting member 41, the opening area of ​​the through-hole 2c on the first surface 2a side is smaller than the opening area on the second surface 2b side. This allows light to be more reliably incident on the first optical waveguide 45. Note that the relationship between the opening area of ​​the through-hole 2c on the first surface 2a side and the opening area on the second surface 2b side is not limited to the above.

[0136] The optical element 42 is not limited to silicon photonics. Alternatively, the first optical waveguide 45 does not necessarily have to be included in the optical element 42. For example, the first optical waveguide 45 may be an optical fiber or the like.

[0137] In the optical connection structures according to the third to fifth embodiments, the first optical waveguide is directly connected to the optical connecting member. However, the first optical waveguide may be indirectly connected to the optical connecting member via an appropriate optical member. The optical member may be light-transmitting. Examples of the optical member include a glass plate, a lens, a prism, and the like.

[0138] When the optical member is provided between the first optical waveguide and the optical member, for example, light emitted from the first optical waveguide passes through the optical member and the optical connecting member and enters the second optical waveguide or the light receiving element. Alternatively, for example, light emitted from the second optical waveguide or the light emitting element passes through the optical connecting member and the optical member and enters the first optical waveguide. The optical connecting member according to the present invention may be disposed between the first optical waveguide and the second optical waveguide, the light emitting element, or the light receiving element, and optically connects the first optical waveguide with the second optical waveguide, the light emitting element, or the light receiving element.

[0139] 4, the plurality of through holes in the base member 2A include a plurality of through holes 2c1 and a plurality of through holes 2c2. The diameters of the portions opening toward the second surface 2b between the through holes 2c1 and the through holes 2c2 are different from each other. Note that the plurality of through holes may include a plurality of through holes whose diameters of the portions opening toward the first surface 2a are different from each other. This example is shown in the sixth embodiment.

[0140] (Optical Connecting Member) (Sixth Embodiment) FIG. 14 is a schematic cross-sectional view showing a portion of an optical connecting member according to a sixth embodiment, which corresponds to the cross section taken along line II in FIG.

[0141] The base member of the optical connecting member 51 is a glass substrate 52 according to one embodiment of the present invention. The plurality of through holes in the glass substrate 52 serving as the base member include a plurality of first through holes 52c and a plurality of second through holes 52d. The first through holes 52c and the second through holes 52d have different diameters at the portions opening to the first surface 52a and the portions opening to the second surface 52b. This embodiment differs from the first embodiment in that the plurality of through holes include a plurality of first through holes 52c and a plurality of second through holes 52d. Except for the above points, the optical connecting member 51 of this embodiment has the same configuration as the optical connecting member 1 of the first embodiment.

[0142] The inner walls of the plurality of through holes in the glass substrate 52 are inclined with respect to the normal direction of the first surface 52 a. As in the first embodiment, a reflective film 4 is provided on the inner wall of each through hole in the glass substrate 52 serving as the base member. This forms a reflective structure.

[0143] In the present invention, the value obtained by dividing the opening area of ​​each first through hole 52c on the first surface 52a side by the opening area of ​​each first through hole 52c on the second surface 52b side is preferably equal to or greater than 10, more preferably equal to or greater than 30, and even more preferably equal to or greater than 50. On the other hand, the value obtained by dividing the opening area of ​​each first through hole 52c on the first surface 52a side by the opening area of ​​each first through hole 52c on the second surface 52b side is preferably equal to or less than 100, more preferably equal to or less than 90, and even more preferably equal to or less than 80.

[0144] The value obtained by dividing the opening area of ​​each second through hole 52d on the first surface 52a side by the opening area of ​​each second through hole 52d on the second surface 52b side is preferably equal to or greater than 1.1, more preferably equal to or greater than 1.5, and even more preferably equal to or greater than 2. On the other hand, the value obtained by dividing the opening area of ​​each second through hole 52d on the first surface 52a side by the opening area of ​​each second through hole 52d on the second surface 52b side is preferably less than 50, more preferably less than 30, and even more preferably less than 10.

[0145] In other words, the value obtained by dividing the opening area of ​​the first through hole 52c on the first surface 52a side by the opening area of ​​the first through hole 52c on the second surface 52b side is preferably 10 or more and 100 or less. The value obtained by dividing the opening area of ​​the second through hole 52d on the first surface 52a side by the opening area of ​​the second through hole 52d on the second surface 52b side is preferably 1.1 or more and less than 50. The value obtained by dividing the opening area of ​​the first through hole 52c on the first surface 52a side by the opening area of ​​the second through hole 52c on the second surface 52b side is more preferably 30 or more and 90 or less. The value obtained by dividing the opening area of ​​the second through hole 52d on the first surface 52a side by the opening area of ​​the second through hole 52d on the second surface 52b side is more preferably 1.5 or more and less than 30. The value obtained by dividing the opening area of ​​the first through hole 52c on the first surface 52a side by the opening area of ​​the first through hole 52c on the second surface 52b side is more preferably not less than 50 and not more than 80. The value obtained by dividing the opening area of ​​the second through hole 52d on the first surface 52a side by the opening area of ​​the second through hole 52d on the second surface 52b side is more preferably not less than 1.1 and less than 10.

[0146] As described above, in this embodiment, the ratio of the opening area of ​​the first through-hole 52c on the first surface 52a side to the opening area of ​​the second through-hole 52d on the first surface 52a side to the opening area of ​​the second through-hole 52d on the first surface 52a side to the opening area of ​​the second surface 52b side is significantly different from each other. Therefore, a single optical connecting member 51 can be used for applications including, for example, multiple optical paths having significantly different configurations. Furthermore, when optically connecting a first optical waveguide to a second optical waveguide, a light-emitting element, or a light-receiving element, the optical connecting member 51 can be simply disposed between the first optical waveguide and the second optical waveguide, the light-emitting element, or the light-receiving element. This effectively increases the productivity of the optical connection structure.

[0147] The base member of the optical connecting member 51 is a glass substrate 52. However, as described above, the material of the base member is not limited to glass.

[0148] The first through-hole 52c and the second through-hole 52d in the optical connecting member 51 are formed by, for example, an etching process. At this time, the surface of the glass substrate 52 serving as the base member is also etched. Therefore, at least a portion of the surface of the base member is an etched surface. The etched surface is a smooth surface that does not contain microcracks. Therefore, when at least a portion of the surface of the base member is an etched surface, the mechanical strength of the base member is improved. Below, an example of a manufacturing method using an etching process for the optical connecting member 51 according to the sixth embodiment will be described.

[0149] (Manufacturing Method) FIGS. 15(a) to 15(e) are schematic cross-sectional views for explaining an example of a manufacturing method for the optical connecting member according to the sixth embodiment.

[0150] As shown in Fig. 15(a), an inorganic member 57 made of glass is prepared. The inorganic member 57 has a third surface 57a and a fourth surface 57b. The third surface 57a and the fourth surface 57b face each other. The third surface 57a of the inorganic member 57 corresponds to the first surface 7a of the inorganic member 7 shown in Fig. 7(a). The fourth surface 57b of the inorganic member 57 corresponds to the second surface 7b of the inorganic member 7. Next, a protective sheet 58 is provided on the fourth surface 57b of the inorganic member 57.

[0151] Next, a first laser light irradiation step is performed. Specifically, laser light is irradiated onto the inorganic member 57 from the third surface 57a side. As a result, a first modified portion 57e is formed in a part of the inorganic member 57, extending from the third surface 57a to the fourth surface 57b. By repeating this process, a plurality of first modified portions 57e are formed in the inorganic member 57. However, it is sufficient that at least one first modified portion 57e is formed in the inorganic member 57.

[0152] Next, a first etching step is performed. Specifically, the plurality of first modified portions 57e in the inorganic member 57 are etched. As a result, a plurality of first recesses 57c are formed in the inorganic member 57, as shown in FIG. 15(b). The first recesses 57c are recesses for forming the first through-holes 52c in the glass substrate 52 shown in FIG.

[0153] Specifically, the etching treatment in the first etching step is a wet etching treatment. For example, hydrofluoric acid can be used in the etching treatment in the first etching step. Note that an etching solution other than hydrofluoric acid may also be used in the first etching step.

[0154] Next, as shown in FIG. 15( c), a second laser light irradiation step is performed. Specifically, laser light is irradiated onto the inorganic member 57 from the third surface 57a side. As a result, a second modified portion 57f is formed in the inorganic member 57 except for the first recess 57c, extending from the third surface 57a to the fourth surface 57b. By repeating this process, a plurality of second modified portions 57f are formed in the inorganic member 57. However, it is sufficient to form at least one second modified portion 57f in the inorganic member 57.

[0155] 15(c), more specifically, when forming one second modified region 57f, multiple points on the inorganic member 57 are irradiated with laser light. On the other hand, when forming one first modified region 57e, one point on the inorganic member 57 is irradiated with laser light. This makes it possible to adjust the diameters of the multiple recesses or multiple through holes to be formed. Note that when forming one second modified region 57f, laser light may be irradiated at one point on the inorganic member 57.

[0156] Next, a second etching step is performed. Specifically, the inorganic member 57 is etched to form the first recesses 57c and the second modified regions 57f. As a result, as shown in FIG. 15(d), the inorganic member 57 is formed with the second recesses 57d, and the diameters of the first recesses 57c are expanded. The second recesses 57d are recesses for forming the second through-holes 52d in the glass substrate 52 shown in FIG. 14.

[0157] Specifically, the etching treatment in the second etching step is a wet etching treatment. For example, a sodium hydroxide aqueous solution can be used in the etching treatment in the second etching step. Note that, in the second etching step, an etching solution other than the sodium hydroxide aqueous solution may be used.

[0158] The first etching step and the second etching step are performed in a state in which the protective sheet 58 is provided on the fourth surface 57b of the inorganic member 57. On the other hand, steps other than the first etching step and the second etching step do not need to be performed in a state in which the protective sheet 58 is provided. For example, the protective sheet 58 may be provided on the fourth surface 57b of the inorganic member 57 after the first laser light irradiation step. The protective sheet 58 may be peeled off from the fourth surface 57b after the first etching step. In this case, the protective sheet 58 may be provided on the fourth surface 57b before or after the second laser light irradiation step.

[0159] When the first laser light irradiation step is performed without providing the protective sheet 58 on the fourth surface 57b of the inorganic member 57, the laser light may be irradiated from the fourth surface 57b side. Similarly, in the second laser light irradiation step, the laser light may be irradiated from the fourth surface 57b side.

[0160] After the second etching step, the protective sheet 58 is peeled off from the fourth surface 57b of the inorganic member 57. After the protective sheet 58 is peeled off from the fourth surface 57b, a third etching step is performed. Specifically, the first recesses 57c and the second recesses 57d in the inorganic member 57 are etched. As a result, a plurality of first through holes 52c and a plurality of second through holes 52d are formed, as shown in FIG. 15( e), and the glass substrate 52 is obtained.

[0161] Specifically, the etching treatment in the third etching step is a wet etching treatment. For example, a sodium hydroxide aqueous solution can be used in the etching treatment in the third etching step. Note that, in the third etching step, an etching solution other than the sodium hydroxide aqueous solution may be used.

[0162] The etching rate in the first etching step is different from the etching rates in the second etching step and the third etching step, which allows the diameters of the first through holes 52c and the second through holes 52d to be adjusted more reliably and with high precision.

[0163] In the above example, the etching rates are made different by using different types of etching liquid in the first etching step and the second etching step. However, for example, the etching rates may be made different by using the same type of etching liquid but different concentrations in the first etching step and the second etching step. Alternatively, for example, the etching rates may be made different by using the same type of etching liquid but different etching temperatures in the first etching step and the second etching step. The same applies to the first etching step and the third etching step. That is, by adjusting the type of etching liquid, the concentration of the etching liquid, the etching temperature, and the etching time, it is possible to arbitrarily adjust the etching rates in the first etching step, the second etching step, and the third etching step.

[0164] Furthermore, in the above example, by using the protective sheet 58, the etching treatment in the first etching step and the second etching step is performed only on the third surface 57a of the third surface 57a and the fourth surface 57b of the inorganic member 57. Thereafter, the protective sheet 58 is peeled off from the fourth surface 57b. Then, the etching treatment in the third etching step is performed from the fourth surface 57b side. This makes it possible to adjust with high precision the diameter of the portion of the first through hole 52c and the second through hole 52d that opens to the first surface 52a and the portion that opens to the second surface 52b.

[0165] 15(a) to 15(e) are a part of an example of a method for manufacturing the optical connecting member 51 shown in Fig. 14. At the same time, this method is also an example of a method for manufacturing the glass substrate 52 according to one embodiment of the present invention.

[0166] 14 is formed in the plurality of first through-holes 52c and the plurality of second through-holes 52d of the glass substrate 52. The reflective film 4 can be formed by, for example, a sputtering method or a vacuum deposition method.

[0167] Below, another example of a method for manufacturing the optical connecting member 51 according to the sixth embodiment will be described. In this example, the laser beam is irradiated three times and the etching process is performed four times, but for convenience, these will be referred to as the third to fifth laser beam irradiation steps and the fourth to seventh etching steps. However, these steps may also be referred to as the first to third laser beam irradiation steps and the first to fourth etching steps.

[0168] 16(a) to 16(e) are schematic cross-sectional views for explaining the third and fourth laser beam irradiation steps and the fourth to sixth etching steps in an example of a method for manufacturing an optical connecting member according to the sixth embodiment. Figures 17(a) and 17(b) are schematic cross-sectional views for explaining the fifth laser beam irradiation step and the seventh etching step in an example of a method for manufacturing an optical connecting member according to the sixth embodiment.

[0169] 16A, an inorganic member 57 made of glass is prepared. Next, a protective sheet 58 is provided on a fourth surface 57b of the inorganic member 57.

[0170] Next, a third laser light irradiation step is performed. Specifically, laser light is irradiated onto the inorganic member 57 from the third surface 57a side. In the third laser light irradiation step, a first modified portion 57e is formed in a part of the inorganic member 57, extending from the third surface 57a to the portion between the third surface 57a and the fourth surface 57b. By repeating this process, a plurality of first modified portions 57e are formed in the inorganic member 57. However, it is sufficient to form at least one first modified portion 57e in the inorganic member 57.

[0171] In the third laser light irradiation step, when forming one modified portion, laser light is irradiated to one point on the inorganic member 57. This is the same as in the fourth laser light irradiation step and the fifth laser light irradiation step described later.

[0172] Next, a fourth etching step is performed. Specifically, the first modified portions 57e in the inorganic member 57 are etched. As a result, a plurality of first recesses 57c are formed in the inorganic member 57, as shown in FIG. 16B .

[0173] Specifically, the etching treatment in the fourth etching step is a wet etching treatment. For example, hydrofluoric acid may be used in the etching treatment in the fourth etching step. Note that an etching solution other than hydrofluoric acid may also be used in the fourth etching step.

[0174] 16(c), a fourth laser light irradiation step is performed. Specifically, laser light is irradiated onto the third surface 57a of the inorganic member 57. As a result, a second modified portion 57f is formed in the inorganic member 57 except for the first recess 57c, extending from the third surface 57a to the fourth surface 57b. By repeating this process, a plurality of second modified portions 57f are formed in the inorganic member 57. However, it is sufficient to form at least one second modified portion 57f in the inorganic member 57.

[0175] Next, a fifth etching step is performed. Specifically, the first recesses 57c and the second modified regions 57f are etched in the inorganic member 57. As a result, as shown in FIG. 16D, the second recesses 57d are formed in the inorganic member 57, and the diameters of the first recesses 57c are expanded.

[0176] Specifically, the etching treatment in the fifth etching step is a wet etching treatment. For example, a sodium hydroxide aqueous solution can be used in the etching treatment in the fifth etching step. Note that, in the fifth etching step, an etching solution other than the sodium hydroxide aqueous solution may be used.

[0177] The fourth etching step and the fifth etching step are performed in a state in which the protective sheet 58 is provided on the fourth surface 57b of the inorganic member 57. On the other hand, steps other than the fourth etching step and the fifth etching step do not need to be performed in a state in which the protective sheet 58 is provided. For example, the protective sheet 58 may be provided on the fourth surface 57b of the inorganic member 57 after the third laser light irradiation step. The protective sheet 58 may be peeled off from the fourth surface 57b after the third etching step. In this case, the protective sheet 58 may be provided on the fourth surface 57b before or after the fourth laser light irradiation step.

[0178] When the fourth laser light irradiation step is performed without providing the protective sheet 58 on the fourth surface 57b of the inorganic member 57, the laser light may be irradiated from the fourth surface 57b side.

[0179] After the fifth etching step, the protective sheet 58 is peeled off from the fourth surface 57b of the inorganic member 57. After the protective sheet 58 is peeled off from the fourth surface 57b, a sixth etching step is performed. Specifically, the plurality of second recesses 57d in the inorganic member 57 are etched. As a result, a plurality of second through holes 52d are formed, as shown in FIG. 16( e). Note that in the fifth etching step, the plurality of first recesses 57c are also etched, and therefore the diameters of the plurality of first recesses 57c are expanded.

[0180] Specifically, the etching treatment in the sixth etching step is a wet etching treatment. In the sixth etching step, for example, an aqueous sodium hydroxide solution can be used. Note that in the sixth etching step, an etching solution other than the aqueous sodium hydroxide solution may also be used.

[0181] Next, as shown in FIG. 17( a), a sixth laser light irradiation step is performed. Specifically, laser light is irradiated onto the first recess 57c in the inorganic member 57 from the third surface 57a side or the fourth surface 57b side. This forms a third modified region 57g extending from the bottom of the first recess 57c to the fourth surface 57b. By repeating this process, multiple third modified regions 57g are formed in the inorganic member 57. However, it is sufficient to form at least one third modified region 57g in the inorganic member 57.

[0182] Next, a seventh etching step is performed. Specifically, the third modified portion 57g in the inorganic member 57 is etched. As a result, as shown in FIG. 17B, a plurality of first through holes 52c are formed, and the glass substrate 52 is obtained. Note that in the seventh etching step, the plurality of second through holes 52d are also etched, and therefore the diameters of the plurality of second through holes 52d are enlarged.

[0183] The etching rate in the fourth etching step is different from the etching rates in the fifth to seventh etching steps, which allows the diameters of the first through holes 52c and the second through holes 52d to be adjusted more reliably and with high precision.

[0184] Furthermore, in the above example, by using the protective sheet 58, the etching treatment in the fourth etching step and the fifth etching step is performed only on the third surface 57a of the third surface 57a and the fourth surface 57b of the inorganic member 57. Thereafter, the protective sheet 58 is peeled off from the fourth surface 57b. Then, the etching treatment in the sixth etching step and the seventh etching step is performed on the fourth surface 57b side. This makes it possible to adjust with high precision the diameter of the portion of the first through hole 52c and the second through hole 52d that opens to the first surface 52a and the portion that opens to the second surface 52b.

[0185] Additionally, in the above example, the second through hole 52d is formed by the sixth etching step. Meanwhile, the first through hole 52c is formed by the seventh etching step. It is preferable that the etching rates or etching times of the sixth and seventh etching steps are different from each other. This allows the diameters of the portions of the first through hole 52c that open to the second surface 52b of the glass substrate 52 and the diameters of the portions of the second through hole 52d that open to the second surface 52b to be adjusted with even greater precision.

[0186] The methods shown in Figures 16(a) to 16(e) and Figures 17(a) and 17(b) are part of an example of a method for manufacturing the optical connecting member 51 shown in Figure 14. At the same time, these methods are also an example of a method for manufacturing the glass substrate 52 according to one embodiment of the present invention.

[0187] Next, the reflective film 4 shown in FIG. 14 is formed in the plurality of first through-holes 52c and the plurality of second through-holes 52d of the glass substrate 52.

[0188] In the above embodiment, a glass substrate is used as the base member of the optical connecting member, but this is not limiting. The glass substrate may have minute through-holes for wiring in a core substrate, an interposer, etc. In this case, a through-electrode may be formed by filling the through-holes with a conductive material.

[0189] DESCRIPTION OF SYMBOLS 1, 1A, 1B...optical connecting member 2, 2A, 2B...base member 2a, 2b...first and second surfaces 2c, 2c1 to 2c4...through hole 4...reflecting film 5, 6...first and second optical waveguides 7...inorganic member 7a, 7b...first and second surfaces 8...grating coupler 9...reflecting film 11, 11A...optical connecting member 13, 13A...reflecting structure 17...transparent material 20, 20A...optical connecting structure 21...optical connecting member 22A, 22B...optical element 23...substrate 23a...groove portion 24...substrate 24a...recess 25, 26...first and second optical waveguides 27...light emitting element 30...optical connecting structure 32B...optical element 34...substrate 34a...recess 37...light receiving element 40...optical connecting structure 41...optical connecting member 42... Optical element 45... First optical waveguide 51... Optical connecting member 52... Glass substrate 52a, 52b... First and second surfaces 52c, 52d... First and second through holes 57... Inorganic member 57a, 57b... Third and fourth surfaces 57c, 57d... First and second recesses 57e to 57g... First to third modified portions 58... Protective sheet

Claims

1. An optical connecting component disposed between a first optical waveguide and a second optical waveguide, a light emitting element, or a light receiving element, and optically connecting the first optical waveguide and the second optical waveguide, the light emitting element, or the light receiving element, comprising: a base member having a first surface and a second surface opposite the first surface, and having at least one through hole penetrating from the first surface to the second surface; and a reflective structure provided within the through hole that reflects light.

2. The optical connecting member according to claim 1, wherein the base member is made of an inorganic material.

3. The optical connecting member according to claim 2, wherein the inorganic material is one of glass and silicon.

4. The optical connecting member according to claim 3, wherein the inorganic material is glass, and the reflecting structure has a transparent material having a higher refractive index than the base member.

5. The optical connecting member according to claim 4, wherein the transparent material is a photocurable resin or a thermosetting resin.

6. An optical connecting member according to any one of claims 1 to 5, wherein an inner wall of at least one of said through holes in said base member is inclined with respect to the normal direction of said first surface.

7. The optical connecting member according to any one of claims 1 to 5, wherein the reflective structure has a reflective film.

8. An optical connection member according to any one of claims 1 to 5, wherein a plurality of the through holes are provided, and on at least one of the first surface and the second surface, the openings of at least some of the plurality of through holes are arranged so as to be positioned on a straight line.

9. The thermal expansion coefficient of the base member is 30 x 10 －７ / ℃ or more, 70 x 10 －７ The optical connecting member according to any one of claims 1 to 5, wherein the temperature is 100°C or lower.

10. The optical connecting member according to any one of claims 1 to 5, wherein at least a part of the surface of the base member is an etched surface.

11. The optical connecting member according to any one of claims 1 to 5, wherein a plurality of the through holes are provided.

12. The optical connecting member according to claim 11, wherein the plurality of through holes include at least two through holes having different shapes in a plan view.

13. An optical connection member as described in claim 12, wherein the inner walls of the plurality of through holes of the base member are inclined with respect to the normal direction of the first surface, the plurality of through holes include first through holes and second through holes having mutually different shapes in a planar view, and a value obtained by dividing the opening area of the first through hole on the first surface side by the opening area of the first through hole on the second surface side is different from a value obtained by dividing the opening area of the second through hole on the first surface side by the opening area of the second through hole on the second surface side.

14. An optical connection structure comprising: an optical connection member according to any one of claims 1 to 5; the first optical waveguide; and an optical element including the second optical waveguide, wherein the optical connection member is disposed between the first optical waveguide and the optical element so that the first surface side faces the first optical waveguide, and the optical connection member optically connects the first optical waveguide and the second optical waveguide.

15. The optical connection structure according to claim 14, wherein the second optical waveguide is a silicon waveguide.

16. An optical connection structure comprising: an optical connection member according to any one of claims 1 to 5; the first optical waveguide; and an optical element including the light-receiving element, wherein the optical connection member is disposed between the first optical waveguide and the optical element so that the first surface side faces the first optical waveguide; the optical connection member optically connects the first optical waveguide and the light-receiving element; the inner wall of at least one of the through holes in the base member is inclined with respect to the direction in which the first surface and the second surface face each other; and the opening area of at least one of the through holes on the first surface side is larger than the opening area on the second surface side.

17. An optical connection structure comprising: an optical connection member according to any one of claims 1 to 5; the first optical waveguide; and the light-emitting element, wherein the optical connection member is disposed between the first optical waveguide and the light-emitting element so that the first surface side faces the first optical waveguide, and the optical connection member optically connects the first optical waveguide and the light-emitting element.

18. The optical connection structure according to claim 14, wherein the first optical waveguide is an optical fiber.

19. A glass substrate having a first surface and a second surface opposite the first surface, a plurality of through holes penetrating from the first surface to the second surface, inner walls of the plurality of through holes being inclined with respect to a normal direction of the first surface, the plurality of through holes including first through holes and second through holes, wherein a value obtained by dividing an opening area of the first through hole on the first surface side by an opening area of the first through hole on the second surface side is different from a value obtained by dividing an opening area of the second through hole on the first surface side by an opening area of the second through hole on the second surface side.

20. A method for manufacturing an optical connection member according to any one of claims 1 to 5, comprising the steps of: modifying a part of an inorganic member made of glass by irradiating the inorganic member with laser light; and forming the through-hole by etching the modified part of the inorganic member, thereby obtaining the base member.

21. A method for manufacturing an optical connecting member according to claim 13, comprising the steps of: preparing an inorganic member made of glass and having a third surface and a fourth surface opposite the third surface; a first laser light irradiation step of irradiating the inorganic member with laser light from the third surface side or the fourth surface side to form a first modified portion in a part of the inorganic member; a first etching step of etching the first modified portion to form a first recess for forming the first through hole; a second laser light irradiation step of irradiating the inorganic member with laser light from the third surface side or the fourth surface side to form a second modified portion in a part of the inorganic member other than the first recess; a second etching step of etching the second modified portion to form a second recess for forming the second through hole; and a third etching step of etching the first recess and the second recess to form the first through hole and the second through hole, thereby obtaining the base member. The method for manufacturing an optical connecting member, wherein the etching rate in the first etching step is different from the etching rates in the second etching step and the third etching step.

22. A method for manufacturing an optical connection member as described in claim 21, further comprising the steps of: providing a protective sheet on the fourth surface of the inorganic member; and peeling off the protective sheet from the fourth surface of the inorganic member; wherein the first etching step and the second etching step are performed in a state where the protective sheet is provided on the fourth surface of the inorganic member; and the third etching step is performed after the protective sheet has been peeled off from the fourth surface of the inorganic member.

23. A method for manufacturing a glass substrate as recited in claim 19, comprising the steps of: preparing an inorganic member made of glass and having a third surface and a fourth surface opposite the third surface; a first laser light irradiation step of irradiating the inorganic member with laser light from the third surface side or the fourth surface side to form a first modified portion in a part of the inorganic member; a first etching step of etching the first modified portion to form a first recess for forming the first through hole; a second laser light irradiation step of irradiating the inorganic member with laser light from the third surface side or the fourth surface side to form a second modified portion in a part of the inorganic member other than the first recess; a second etching step of etching the second modified portion to form a second recess for forming the second through hole; and a third etching step of etching the first recess and the second recess to form the first through hole and the second through hole, The method for manufacturing a glass substrate, wherein the etching rate in the first etching step is different from the etching rates in the second etching step and the third etching step.

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