Optical waveguide substrate

Abstract

An optical waveguide substrate according to one aspect disclosed herein includes a substrate, an optical waveguide, an optical path conversion unit, and an insulating layer. The optical waveguide is positioned on the substrate, and at least a portion including a tip extends along a first direction. The optical path conversion unit is positioned at the tip of the optical waveguide in a plan view, and changes the optical path of and emits incident light. The insulating layer covers the surface of the substrate. When a region that does not include the insulating layer in a plan view is defined as a non-formation region, the non-formation region includes a first region and a second region. The optical waveguide and the optical path conversion unit are positioned in the first region. The second region is adjacent to the optical path conversion unit via the insulating layer in a second direction orthogonal to the first direction. When the width, along the second direction, of the insulating layer positioned between the second region and the optical path conversion unit is D1, and the width, along the second direction, of a portion where the optical path conversion unit is positioned in the first region is D2, D1 < D2 is satisfied.

Description

Optical waveguide substrate

[0001] This disclosure relates to an optical waveguide substrate.

[0002] Conventionally, optical waveguide substrates have been disclosed in which optical waveguides and electrical wiring are arranged on a substrate for the purpose of parallel transmission of optical signals and electrical signals.

[0003] In the conventional technology described above, an insulating layer is sometimes provided on the surface of the optical waveguide substrate to ensure the insulation reliability of the substrate. Patent Document 1 discloses an optical waveguide substrate having an optical waveguide located on the substrate and a solder resist layer that protects the surface of the substrate.

[0004] Japanese Patent Publication No. 2018-159728

[0005] An optical waveguide substrate according to one aspect of the present disclosure comprises a substrate, an optical waveguide, an optical path conversion section, and an insulating layer. The optical waveguide is located on the substrate, and at least a portion of it, including its tip, extends along a first direction. The optical path conversion section is located at the tip of the optical waveguide in a plan view of the substrate and changes the optical path of incident light before emission. The insulating layer covers the surface of the substrate. In a plan view of the substrate, if the area where the insulating layer is not formed is defined as the non-formed area, the non-formed area includes a first area and a second area. The optical waveguide and the optical path conversion section are located in the first area. The second area is adjacent to the optical path conversion section via the insulating layer in a second direction perpendicular to the first direction. The width of the insulating layer located between the second area and the optical path conversion section along the second direction is D. １ The width along the second direction in the part of the first region where the optical path conversion unit is located is defined as D. ２ In that case, D １ <D ２ That is the case.

[0006] Figure 1 is a plan view showing an example of the configuration of an optical waveguide substrate according to the first embodiment. Figure 2 is a cross-sectional view showing the configuration near the first region in the view along the line II-II shown in Figure 1. Figure 3 is an enlarged cross-sectional view of region H2 shown in Figure 2. Figure 4 is a diagram showing the relationship between the distance between the insulating layer and the core in the first region and the amount of deviation from the design value of the optical waveguide film thickness in the first region. Figure 5 is an enlarged plan view showing the configuration near the second region in an optical waveguide substrate according to the second embodiment.

[0007] In the prior art, when manufacturing an optical waveguide substrate, if an attempt is made to form an optical waveguide after forming a solder resist layer on the substrate, when the optical waveguide material is applied onto the substrate, the solder resist layer repels the aforementioned material, which may result in an uneven film thickness of the formed optical waveguide.

[0008] According to the present disclosure, the risk of an uneven film thickness of an optical waveguide can be reduced, and the uniformity of the film thickness can be improved.

[0009] Hereinafter, modes for carrying out the optical waveguide substrate according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. It should be noted that the present disclosure is not limited by these embodiments. In addition, each embodiment can be appropriately combined within a range that does not cause contradiction in processing contents. In addition, in the following embodiments, the same parts are denoted by the same reference numerals, and repeated descriptions are omitted.

[0010] In addition, in the embodiments described below, expressions such as "orthogonal" or "parallel" may be used, but these expressions do not require being strictly "orthogonal" or "parallel". That is, each of the above expressions allows deviations from, for example, manufacturing accuracy and installation accuracy.

[0011] In addition, in each of the drawings referred to below, in order to make the description easy to understand, mutually orthogonal X-axis direction, Y-axis direction, and Z-axis direction are defined, and an orthogonal coordinate system in which the Z-axis direction is a vertically upward direction may be shown in some cases.

[0012] (First Embodiment) First, the configuration of the optical waveguide substrate 100 according to the first embodiment will be described with reference to FIG. 1. FIG. 1 is a plan view showing a configuration example of the optical waveguide substrate 100 according to the first embodiment.

[0013] As shown in FIG. 1, the optical waveguide substrate 100 includes a substrate 1, an optical waveguide 2, and a plurality of optical path conversion units 3.

[0014] The substrate 1 has, for example, a planar rectangular plate shape in a plan view. The substrate 1 has a first surface 10 (see FIG. 2). An insulating layer 11 and an optical waveguide 2 are positioned on the first surface 10. The first surface 10 is a plane parallel to a first direction (herein, the direction along the X-axis) and a second direction orthogonal to the first direction (herein, the direction along the Y-axis). The substrate 1 may be, for example, an organic substrate or a ceramic substrate. Alternatively, the substrate 1 may be, for example, a semiconductor substrate.

[0015] The insulating layer 11 covers the first surface 10 of the substrate 1. By protecting the surface of the substrate 1 with the insulating layer 11, the insulation reliability of the optical waveguide substrate 100 can be improved. The insulating layer 11 may be formed of, for example, a resin material such as epoxy resin.

[0016] The optical waveguide substrate 100 of the present disclosure has a non-formation region where the insulating layer 11 is not formed in a plan view of the substrate 1. Such a non-formation region may include a first region 12 and a second region 13. The number of the first region 12 and the second region 13 may be plural. For example, the optical waveguide substrate 100 according to the first embodiment includes one first region 12 and three second regions 13.

[0017] The first region 12 extends inward of the substrate 1 from an end portion of the substrate 1 (herein, the end portion on the positive X-axis direction side) along the first direction. The optical waveguide 2 and a plurality of optical path conversion units 3 are positioned inside the first region 12. As will be specifically described later, the optical waveguide 2 according to the present embodiment extends along the first direction from the end portion on the positive X-axis direction side of the substrate 1 toward the inside of the substrate 1, and branches into two on the first surface 10 from the middle. After branching, the two branched optical waveguides 2 each extend along the first direction, and the optical path conversion unit 3 is positioned at the tip end thereof. The first region 12 includes a first portion 121 where the optical path conversion unit 3 is positioned, and a second portion 122 other than the first portion 121. For example, in the first embodiment, the first region 12 is composed of two first portions 121 and one second portion 122. Note that the number of the first portions 121 may be plural depending on the shape of the optical waveguide 2.

[0018] Each of the multiple first portions 121 has an optical path conversion unit 3 located inside it. In other words, the region of the first area 12 where the optical path conversion unit 3 is located is the first portion 121. The multiple first portions 121 may be spaced apart along the second direction. The second portion 122 extends along the first direction from the multiple first portions 121 to the edge of the substrate 1 (in this case, the edge on the positive X-axis side). That is, in the first embodiment, the first area 12 is formed by the second portion 122 and the multiple first portions 121 branching from the second portion 122.

[0019] The optical waveguide 2 transmits optical signals. The optical waveguide 2 is formed on the first surface 10 of the substrate 1 in the first region 12. There may be a gap between the outer edge of the first region 12 and the outer edge of the optical waveguide 2. At least a portion of the optical waveguide 2, including its tip, extends along the first direction. In this embodiment, the optical waveguide 2 has a first optical path portion 2A, which is a portion that extends along the first direction from the end of the substrate 1 on the positive X-axis side toward the inside of the substrate 1, and a second optical path portion 2B, which is a portion of the two branched optical waveguides 2 that extend along the first direction after branching.

[0020] The optical waveguide 2 has a plurality of cores 22 through which optical signals propagate. The plurality of cores 22 may be arranged with spacing between them along the second direction when the substrate 1 is viewed through a plane.

[0021] For example, in the optical waveguide 2 according to the first embodiment, the first optical path section 2A has 10 cores 22 along the second direction. One of the two second optical path sections 2B has 5 of the 10 cores 22. The tips of these 5 cores are located inside the first section 121 of one of the two second optical path sections 2B. The other of the two second optical path sections 2B has the other 5 of the 10 cores 22. The tips of these 5 cores are located inside the first section 121 of the other. An optical path conversion section 3 is located at the tip of each optical waveguide 2 located in the first section 121. The detailed configuration of the optical waveguide 2 will be described later with reference to Figure 2.

[0022] As shown in Figure 1, the distance along the second direction between the core 22 and the outer edge of the first region 12 in the first part 121 is L.１ , and let L be the distance along the second direction between the core 22 in the second portion 122 and the outer edge of the first region 12, here, the distance along the second direction between the core 22 in the first optical path portion 2A and the outer edge of the first region 12 ２ . In the optical waveguide substrate 100 according to the first embodiment, the distance L １ and the distance L ２ has a relationship of L １ < L ２ . Note that the distance along the second direction between the core 22 and the outer edge of the first region 12 refers to the distance along the second direction between the core 22 facing the outer edge of the first region 12 and the outer edge of the first region 12.

[0023] According to this configuration, as shown in FIG. 1, the plurality of cores 22 can be concentrated in the central portion in the second direction at the end portion on the positive X-axis direction side of the substrate 1. This makes it easy to connect the plurality of cores 22 to optical fibers of an optical connector (not shown) at the end portion on the positive X-axis direction side of the substrate 1.

[0024] The plurality of optical path converting portions 3 are respectively located at the tips of the plurality of optical waveguides 2 positioned inside the substrate 1 in a plan view of the substrate 1. The optical path converting portion 3 can change the optical path of incident light and emit the changed light. For example, light emitted in the negative X-axis direction from the tip of the optical waveguide 2 located inside the substrate 1 has its optical path changed by the optical path converting portion 3 and is emitted toward the positive Z-axis direction. Accordingly, for example, when an optical element (not shown) is disposed above the optical path converting portion 3, light from the optical waveguide 2 can be guided to the optical element. Similarly, for example, light emitted in the negative Z-axis direction from the optical element has its optical path changed by the optical path converting portion 3 and is emitted toward the positive X-axis direction. Accordingly, light from the optical element can be guided to the optical waveguide 2.

[0025] The optical element referred to herein is an element that mutually converts optical signals and electrical signals. Note that the optical element may have a plurality of electrodes. Such electrodes may be electrically connected to an electrode portion 4 described later included in the optical waveguide substrate 100.

[0026] The second region 13 is located adjacent to the optical path conversion unit 3 via the insulating layer 11 along the second direction. For example, in the first embodiment, multiple (in this case, two) optical path conversion units 3 and multiple (in this case, three) second regions 13 are arranged alternately along the second direction. In a plan view, the shape of the second region 13 may be, for example, a square.

[0027] Multiple electrode portions 4 may be provided around the optical path conversion unit 3. Specifically, the multiple electrode portions 4 may be positioned to surround the first portion 121 where the optical path conversion unit 3 is located in a plan view of the substrate 1. The detailed configuration of the electrode portions 4 will be described later with reference to Figure 2.

[0028] Next, the configuration of the optical waveguide substrate 100 according to the first embodiment will be described in more detail with reference to Figures 2 to 4. Figure 2 is a cross-sectional view showing the configuration near the first portion 121 in the view along the line II-II shown in Figure 1. Figure 3 is an enlarged cross-sectional view of region H2 shown in Figure 2. The dashed lines shown in Figures 2 and 3 indicate a perspective view of the optical path conversion unit 3.

[0029] As shown in Figure 2, the optical waveguide 2 has a lower cladding 21, a plurality of cores 22, and an upper cladding 23.

[0030] The lower cladding 21 is located on the first surface 10 of the substrate 1 in the first region 12. The lower cladding 21 is formed, for example, by coating the first surface 10 of the substrate 1 with a resin having a predetermined refractive index to a predetermined thickness, and then curing the resin with heat or light.

[0031] Multiple cores 22 are located on the lower cladding 21. As described above, at least a portion of the multiple cores 22 extend along the first direction and are arranged spaced apart from each other along the second direction. As shown in Figure 2, the multiple cores 22 located on the first portion 121 may be arranged at equal intervals along the second direction. The multiple cores 22 are formed, for example, by coating the surface of the lower cladding 21 with a resin having a predetermined refractive index to a predetermined thickness, curing the resin with heat or light, and then patterning the cured resin into a predetermined planar shape using a known method.

[0032] The upper cladding 23 is located on top of the lower cladding 21 and the core 22. The upper cladding 23 is formed, for example, by applying a resin having a predetermined refractive index to the surface of the lower cladding 21 and the core 22 to a predetermined thickness, and then curing the resin with heat or light.

[0033] Thus, the optical waveguide 2 has a configuration in which the lower cladding 21, core 22, and upper cladding 23 are stacked in this order, and the optical signal propagates inside the core 22. As described above, the optical waveguide 2 is formed in the first region 12 on the surface of the substrate 1 where the insulating layer 11 is not located.

[0034] By forming the optical waveguide 2 in the first region 12, the optical waveguide 2 can be made less likely to peel off from the substrate 1. For example, the wettability of the surface of the substrate 1 to the resin material which is the optical waveguide material is higher than the wettability of the surface of the insulating layer 11 to the optical waveguide material. Therefore, if the optical waveguide 2 is formed in the first region 12 where the insulating layer 11 is not located, the material can be evenly coated on the surface of the substrate 1, thereby improving the adhesion of the optical waveguide 2 to the substrate 1. Consequently, compared to the case where the optical waveguide 2 is formed on the surface of the insulating layer 11, the optical waveguide 2 can be made less likely to peel off from the substrate 1.

[0035] As shown in Figure 2, the width of the insulating layer 11 located between the second region 13 and the optical path conversion unit 3 (dashed line in Figure 2) along the second direction is D. １ The width along the second direction in the first part 121 is D. ２ In that case, width D １ and width D ２ The relationship is D １ <D ２ That's how it is.

[0036] With this configuration, the uniformity of the film thickness of the optical waveguide 2 in the first portion 121 can be improved. For example, when an optical waveguide is formed after forming an insulating layer 11 on a substrate, when the optical waveguide material is coated, the surface of the insulating layer 11, which has low wettability to the optical waveguide material, tends to repel the material. For this reason, the material coated on the substrate 1 tends to be unevenly distributed in areas where the insulating layer 11 is not formed.

[0037] For example, in the optical waveguide substrate 100 of the present disclosure, the above material is coated over the entire substrate 1 having a first region 12, and then light is irradiated onto the material located in the first region 12 to cure the material, thereby forming an optical waveguide 2 in the first region 12.

[0038] However, in such a case, the material repelled by the insulating layer 11 located around the first region 12 may flow into the first region 12, potentially causing variations in the film thickness of the optical waveguide 2 formed in the first region 12. In particular, variations in the film thickness of the core 22 are more likely to occur in the first portion 121 where the distance between the core 22 and the outer edge of the first region 12 is relatively small. If variations in the film thickness of the core 22 occur, the performance of the optical waveguide 2 may deteriorate. For this reason, it is desirable to make the film thickness of the optical waveguide 2 in the first portion 121 uniform.

[0039] D １ <D ２ In the optical waveguide substrate 100, a second region 13 is located near the first region 121 where the optical path conversion section 3 is located along the second direction, in which the insulating layer 11 is not formed. As a result, some of the optical waveguide material flows into the second region 13, reducing the inflow of the material into the first region 121. Therefore, the risk of the optical waveguide 2 becoming non-uniform in the first region 121 is reduced, and the uniformity of the film thickness can be improved.

[0040] As shown in Figure 2, a metal layer 14 may be located between the first surface 10 of the substrate 1 and the insulating layer 11. The metal layer 14 functions as a wiring conductor in the optical waveguide substrate 100. For example, the optical elements (not shown) described above are electrically connected to the metal layer 14. The metal layer 14 may be formed of a metallic material such as copper or aluminum.

[0041] As described above, a plurality of electrode portions 4 may be provided around the first portion 121. The electrode portions 4 are formed, for example, by providing an opening 111 in the insulating layer 11 located on the metal layer 14. That is, the electrode portions 4 may be the metal layer 14 exposed on the surface of the insulating layer 11. The electrodes of the optical element described above are connected to the electrode portions 4. This electrically connects the metal layer 14 and the optical element.

[0042] As shown in Figure 2, when the optical waveguide substrate 100 has a metal layer 14, the insulating layer 11 may cover the upper surface and the side surface on the first region 12 side of the metal layer 14. Specifically, the side surface on the first region 12 side of the metal layer 14 refers to the side surface of the metal layer 14 located along the outer edge of the first region 12. In the example shown in Figure 2, the insulating layer 11 covers the side surface of the metal layer 14 located along the outer edges of the first region 12 and the second region 13.

[0043] With this configuration, when the optical waveguide substrate 100 has a metal layer 14, the film thickness of the optical waveguide 2 can be made suitably uniform. For example, in the portion where the metal layer 14 is located between the substrate 1 and the insulating layer 11, the height of the upper surface of the insulating layer 11 relative to the first surface 10 of the substrate 1 is increased by the thickness of the metal layer 14. With the above configuration, as shown in Figure 2, a region in which only the insulating layer 11 is formed, that is, a region in which the height of the upper surface of the insulating layer 11 is relatively low, can be formed along the side surface of the metal layer 14 on the first region 12 side.

[0044] Therefore, the height of the upper surface of the insulating layer 11 located along the outer edge of the first region 12 can be reduced. This allows for a favorable reduction in the inflow of the optical waveguide material into the first region 12 during the coating process. Consequently, the film thickness of the optical waveguide 2 formed in the first region 12 can be favorably made uniform.

[0045] As shown in Figure 2, the thickness of the insulating layer 11 may be less than the thickness of the lower cladding 21. Specifically, the thickness of the insulating layer 11 refers to the height of the upper surface of the insulating layer 11 relative to the first surface 10 of the substrate 1.

[0046] With this configuration, it is easy to form a lower cladding 21 having a predetermined film thickness. For example, in the optical waveguide substrate 100 of the present disclosure, after coating the entire substrate 1 having a first region 12 with lower cladding material, the material located in the first region 12 is irradiated with light to cure the material, thereby forming lower cladding 21 in the first region 12.

[0047] In this case, during the coating process of the lower cladding 21, the thickness of the lower cladding material coated on the first region 12 is greater than the thickness of the insulating layer 11. Therefore, it is difficult to form a lower cladding 21 that is thinner than the thickness of the insulating layer 11. On the other hand, if the lower cladding 21 is thicker than the thickness of the insulating layer 11, it can be formed, for example, simply by curing the coated material. Therefore, with an optical waveguide substrate 100 having the above configuration, it is easy to form a lower cladding 21 having a predetermined film thickness.

[0048] As shown in Figure 3, the distance between adjacent cores 22 is L. ３ In that case, distance L １ and interval L ３ The relationship is, L １ > (L ３ It may also be ×6). As mentioned above, distance L １ This is the distance along the second direction between the core 22 and the outer edge of the first region 12 in the first part 121. Note that L is the distance between adjacent cores 22. ３ Specifically, this refers to the distance between the centers of adjacent cores 22.

[0049] The optical waveguide substrate 100 having such a configuration exhibits high uniformity in the film thickness of the core 22 in the first portion 121. For example, distance L １ If the distance L is too small, the core material repelled by the insulating layer 11 is more likely to flow into the first portion 121 during the core material coating process, which can cause variations in the thickness of the core 22 formed in the first portion 121. １ If the amount is sufficiently large, the material will not easily flow into the first portion 121, so the film thickness of the core 22 in the first portion 121 will be more uniform.

[0050] Figure 4 shows the distance L between the insulating layer 11 and the core 22 in the first portion 121. １ This figure shows the relationship between the amount of deviation from the design value of the film thickness of the optical waveguide 2 at the first part 121 and the distance L. １ In Figure 4, the distance L １ interval L ３ This is expressed as a ratio to [a certain value]. The vertical axis in Figure 4 represents the difference between the design value of the film thickness of the optical waveguide 2 at the first part 121 and the measured value of the actual film thickness of the formed optical waveguide 2.

[0051] In the experimental results shown in Figure 4, the deviation of the film thickness of the optical waveguide 2 from the design value is, distance L １ As the value of increases, it decreases, L １ > (L ３ It can be seen that it is almost constant in the region of ×6). Thus, L １ > (L ３ With the optical waveguide substrate 100 (×6), the uniformity of the film thickness of the optical waveguide 2 formed in the first portion 121 can be improved. Furthermore, if the uniformity of the film thickness of the optical waveguide 2 is high, the uniformity of the film thickness of the core 22 will also be high.

[0052] (Second Embodiment) Next, the configuration of the optical waveguide substrate 200 according to the second embodiment will be described with reference to Figure 5. Figure 5 is an enlarged plan view showing the configuration near the second region 13 in the optical waveguide substrate 200 according to the second embodiment. Note that Figure 5 corresponds to an enlarged cross-sectional view of region H1 shown in Figure 1.

[0053] In the first embodiment, an example was described in which the width and height of the second region 13 in plan view are the same. Specifically, the shape of the second region 13 in the first embodiment was a square in plan view. On the other hand, in the second embodiment, the width and height of the second region 13 in plan view may be different. Specifically, the shape of the second region 13 in the second embodiment is, for example, a rectangle in plan view.

[0054] In this case, as shown in Figure 5, the smaller of the width and height of the second region 13 in plan view is D ３ In this case, width D ３ and interval L ３The relationship is D ３ ≥ L ３ This is also acceptable. As mentioned above, L ３ This is the distance between adjacent cores 22. Note that the width D shown in Figure 5 is... ４ This indicates the larger of the width and height of the second region 13. For example, in Figure 5, width D ３ D is the length in the Y-axis direction, and the width is D. ４ This is the length in the X-axis direction.

[0055] With this configuration, a relatively large second region 13 can be formed. Therefore, in the coating process of the optical waveguide material, the inflow of the material into the first portion 121 can be suitably reduced. Consequently, the film thickness of the optical waveguide 2 in the first portion 121 can be suitably made uniform.

[0056] In the second embodiment, an example was described in which the shape of the second region 13 in plan view is rectangular, but the shape of the second region 13 is not limited to this. The shape of the second region 13 may be, for example, an ellipse, or any other shape. Even in such cases, D ３ ≥ L ３ That would be fine.

[0057] Note that the width and height are lengths in mutually orthogonal directions. For example, if the width is the length in the Y-axis direction and the height is the length in the X-axis direction, then the width of the second region 13 may be the maximum length in the Y-axis direction, and the height of the second region 13 may be the maximum length in the X-axis direction. For example, if the shape of the second region 13 is an ellipse that is long in the X-axis direction, then the width of the second region 13 may be the length of the minor axis of the ellipse, and the height of the second region 13 may be the length of the major axis of the ellipse.

[0058] Furthermore, even in the case where the width and height of the second region 13 in a plan view are the same, as in the second region 13 in the first embodiment, the width and height of the second region 13 are set to the above interval L. ３ By making it larger than this, the film thickness of the optical waveguide 2 in the first portion 121 can be made suitably uniform.

[0059] Although the present disclosure has been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the gist of this disclosure.

[0060] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0061] Furthermore, this technology can also take the following configuration: (1) A substrate; an optical waveguide located on the substrate, with at least a portion including its tip extending along a first direction; an optical path conversion unit located at the tip of the optical waveguide in a plan view of the substrate, which changes the optical path of incident light and emits it; and an insulating layer covering the surface of the substrate, wherein in the plan view, if the region where the insulating layer is not formed is defined as a non-formed region, the non-formed region includes a first region and a second region, the optical waveguide and the optical path conversion unit are located in the first region, the second region is adjacent to the optical path conversion unit via the insulating layer in a second direction perpendicular to the first direction, and the width of the insulating layer located between the second region and the optical path conversion unit along the second direction is D １ The width along the second direction in the portion of the first region where the optical path conversion unit is located is defined as D. ２ In that case, D １ <D ２ (2) The optical waveguide substrate according to (1), wherein the optical waveguide comprises a lower cladding located on the substrate, a core located on the lower cladding and extending along the first direction, and an upper cladding located on the lower cladding and the core. (3) The first region comprises a first portion on which the optical path conversion unit is located, and a second portion extending along the first direction from the first portion to the edge of the substrate, wherein the distance along the second direction between the core in the first portion and the outer edge of the first region is L １The distance along the second direction between the core and the outer edge of the first region in the second portion is L. ２ In that case, L １ <L above ２ The optical waveguide substrate as described in (2) above. (4) The optical waveguide substrate as described in (3) above, wherein the non-formed region includes a plurality of second regions, the first region has a plurality of first portions branching from the second portion, and the plurality of first portions and the plurality of second regions are alternately located along the second direction. (5) The optical waveguide has a plurality of cores arranged apart from each other along the second direction, and the distance between adjacent cores in the first portion is L ３ In that case, L １ >(L above) ３ (6) The optical waveguide substrate according to (3) or (4) above. (6) The optical waveguide has a plurality of cores arranged apart from each other along the second direction, and the distance between adjacent cores in the first portion is L ３ Let D be the smaller of the width and height of the second region in plan view. ３ In that case, D ３ ≧L above ３ The optical waveguide substrate according to any one of (3) to (5) above. (7) The optical waveguide substrate according to any one of (2) to (6) above, wherein the thickness of the insulating layer is less than the thickness of the lower cladding. (8) The optical waveguide substrate according to any one of (1) to (7) above, wherein it has a metal layer located between the substrate and the insulating layer, and the insulating layer covers the upper surface and the side surface on the first region side of the metal layer.

[0062] 1 Substrate 2 Optical waveguide 2A First optical path section 2B Second optical path section 3 Optical path conversion section 4 Electrode section 10 First surface 11 Insulating layer 12 First region 13 Second region 14 Metal layer 21 Lower cladding 22 Core 23 Upper cladding 100 Optical waveguide substrate 111 Aperture 121 First section 122 Second section

Claims

1. The optical waveguide comprises a substrate, an optical waveguide located on the substrate with at least a portion including its tip extending along a first direction, an optical path conversion unit located at the tip of the optical waveguide in a plan view of the substrate and which changes the optical path of incident light and emits it, and an insulating layer covering the surface of the substrate, wherein in the plan view, if the region where the insulating layer is not formed is defined as a non-formed region, the non-formed region includes a first region and a second region, the optical waveguide and the optical path conversion unit are located in the first region, the second region is adjacent to the optical path conversion unit via the insulating layer in a second direction perpendicular to the first direction, and the width of the insulating layer located between the second region and the optical path conversion unit along the second direction is D １ The width along the second direction in the portion of the first region where the optical path conversion unit is located is defined as D. ２ In that case, D １ <D ２ This is an optical waveguide substrate.

2. The optical waveguide substrate according to claim 1, wherein the optical waveguide comprises a lower cladding located on the substrate, a core located on the lower cladding and extending along the first direction, and an upper cladding located on the lower cladding and the core.

3. The first region has a first portion where the optical path conversion unit is located, and a second portion extending from the first portion to the edge of the substrate along the first direction, and the distance along the second direction between the core in the first portion and the outer edge of the first region is L. １ The distance along the second direction between the core and the outer edge of the first region in the second portion is L. ２ In that case, L １ <L above ２ The optical waveguide substrate according to claim 2.

4. The optical waveguide substrate according to claim 3, wherein the non-formed region includes a plurality of the second region, the first region has a plurality of the first portion branching from the second portion, and the plurality of the first portion and the plurality of the second region are alternately located along the second direction.

5. The optical waveguide has the plurality of cores arranged spaced apart from each other along the second direction, wherein L is the distance between the cores adjacent to each other at the first portion ３ , wherein the L １ > (the L ３ ×6), the optical waveguide substrate according to claim 3 or 4.

6. The optical waveguide has a plurality of cores arranged at intervals from each other along the second direction, and the distance between adjacent cores in the first portion is L ３ Let D be the smaller of the width and height of the second region in plan view. ３ In that case, D ３ ≧L above ３ The optical waveguide substrate according to any one of claims 3 to 5.

7. The optical waveguide substrate according to any one of claims 2 to 6, wherein the thickness of the insulating layer is smaller than the thickness of the lower cladding.

8. An optical waveguide substrate according to any one of claims 1 to 7, comprising a metal layer located between the substrate and the insulating layer, wherein the insulating layer covers the upper surface and the side surface on the first region side of the metal layer.

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