JP4627481B2 - Optical waveguide circuit - Google Patents

Description

  The present invention relates to an optical waveguide circuit capable of improving the reflection angle controllability of a reflecting surface used in the input / output of guided light and improving the manufacturing yield of the reflecting surface.

  In a conventional optical waveguide circuit, a mirror groove orthogonal to the optical axis of the waveguide is formed by etching or the like, and a metal film is disposed in the mirror groove. The guided light is output from the waveguide by being reflected by the metal film (see, for example, Patent Document 1).

  In the optical waveguide circuit disclosed in Patent Document 1, a mirror groove that is perpendicular to the optical axis of the waveguide and deeper than the core of the waveguide in the optical waveguide circuit is provided, and a metal film is deposited on the bottom of the mirror groove. Is done. Furthermore, both ends of the ribbon-like metal film formed so as to draw a loop are pressure-bonded onto the metal film at the bottom of the mirror groove. The ribbon-like metal film reflects the guided light upward in order to extract the guided light from the waveguide.

However, it has been difficult to form a flat reflective surface with a ribbon-like metal film. For this reason, wavefront distortion and scattering of guided light have occurred. In addition, it is difficult to finely adjust the shape of the loop formed by the ribbon-like metal film. For this reason, the waveguide light reflected by the ribbon-like metal film has a different reflection angle depending on the location of reflection on the ribbon-like metal film, and the controllability of the reflection angle is poor, and the production yield is poor.
JP 2004-118081 A

  In order to solve such a problem, an object of the present invention is to provide an optical waveguide circuit with high controllability of reflection angle and good manufacturing yield.

  In the optical waveguide circuit according to the present invention, a mirror groove for inputting and outputting guided light includes a first side surface substantially orthogonal to the optical axis, a second side surface facing the first side surface substantially in parallel, and a second side surface. A side surface and a third side surface that intersects to have an internal angle greater than 90 ° and less than 180 °. Since the second side surface and the third side surface have an inner angle larger than 90 ° and smaller than 180 °, the curable resin poured into the mirror groove is prevented from rising due to its surface tension on the third side surface. Can do. For this reason, a reflective part with a flat surface can be formed. In addition, the mirror groove can be prevented from being filled with the curable resin. Therefore, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

  Furthermore, the optical waveguide circuit according to the present invention includes a first side surface in which a mirror groove for inputting / outputting guided light is substantially orthogonal to the optical axis, a second side surface facing the first side surface substantially parallel to the first side surface, A third side surface that intersects the second side surface so as to have an inner angle of 90 ° or more and smaller than 180 °, and a fourth side surface that intersects the third side surface with an outer angle smaller than 180 °. The intersection line formed between the fourth side surface and the third side surface is located on the first side surface side from the intersection line formed between the reflection surface of the reflection portion and the third side surface. For this reason, the curable resin poured into the mirror groove is clogged at the corners of the fourth side surface and the third side surface even if the flow is disturbed due to surface irregularities on the bottom surface of the mirror groove, and the mirror groove is hardened. Filling with resin can be prevented. Further, it is possible to suppress the influence of surface irregularities on the bottom surface and form a reflective portion having a flat surface. Therefore, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

Specifically, according to the first invention of the present application, a clad formed on a flat substrate, a core that guides light surrounded by the clad, and a bottom surface deeper than the core formed to block the core. An optical waveguide circuit comprising: a mirror groove, wherein the first side surface of the core that is exposed is substantially perpendicular to the optical axis of the core, and the second side surface is substantially parallel to the first side surface. Opposing in parallel, the third side surface intersects with the second side surface at an inner angle greater than 90 ° and smaller than 180 °, and the bottom surface is poured into the corner with the second side surface, and a liquid curable resin is poured and cured. This is an optical waveguide circuit having a reflection part formed at the corner to reflect light from the core to the side opposite to the bottom surface.

  The reflection part is preferably formed of a curable resin. It can be formed by pouring a liquid curable resin into a predetermined position of the mirror groove and curing. The reflecting portion has a slope at a corner between the bottom surface of the mirror groove and the second side surface, and is in contact with the bottom surface, the second side surface, and the third side surface. Since the third side intersects with the second side at an inner angle greater than 90 ° and smaller than 180 °, the curable resin poured into the mirror groove is prevented from rising due to surface tension on the third side. can do. For this reason, a reflection part with a flat surface can be formed. Further, by suppressing the rising phenomenon, the mirror groove can be prevented from being filled with the curable resin. Therefore, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

  In the first invention of the present application, the bottom surface exhibits a larger contact angle with respect to a substance forming a portion in contact with the bottom surface of the reflecting portion than a portion in which the reflecting portion does not have the reflecting portion. Is preferred.

  The mirror groove is subjected to surface treatment by an oblique vapor deposition method or the like. The bottom surface is divided into regions having different wettability, the first side surface side of the bottom surface exhibits a larger contact angle with the curable resin, and the second side surface exhibits a smaller contact angle. Divided into small contact angle regions. The third side surface is also divided into a large contact angle region that exhibits a larger contact angle with respect to the curable resin and a small contact angle region that exhibits a smaller contact angle. The curable resin poured into the mirror groove flows by selecting a small contact angle region exhibiting a smaller contact angle on the bottom surface and hits the third side surface. The curable resin rises a small contact angle region on the third side. The curable resin is dammed at the boundary between the small contact angle region and the large contact angle region on the bottom surface and the third side surface. Therefore, it is possible to accurately form a reflection portion having a slope at the corner between the small contact angle region on the bottom surface and the second side surface.

In the first invention of the present application, an angle formed by 90 ° from an inner angle formed by the third side surface and the second side surface is defined as θ °, an inclination angle formed by the reflecting portion with the bottom surface is defined as φ °, When the contact angle of the portion having no reflection portion on the bottom surface is Γ °, it is preferable that the θ satisfies the following formula (1).
θ ≧ sin ⁻¹ (cos Γ / sin φ) (1)
At this time, the portion having no reflecting portion on the bottom surface substantially coincides with the large contact angle region on the bottom surface, and thus the contact angle Γ indicates the contact angle in the large contact angle region on the bottom surface.

  When the third side surface intersects with the second side surface at an internal angle greater than 90 ° and smaller than 180 °, the curable resin rises over the boundary where the contact angle differs on the third side surface due to surface tension. Can be prevented. More precisely, it is preferable that the angle formed between the third side surface and the inclined surface of the reflecting portion is smaller than the contact angle in the large contact angle region of the bottom surface. That is, the above equation (1) may be satisfied. By disposing the third side surface with respect to the second side surface so as to satisfy the above formula (1), the curable resin has a boundary between the large contact angle region and the small contact angle region on the third side surface. Can be prevented from climbing over.

Specifically, in the second invention of the present application, a clad formed on a flat substrate, a core for guiding light surrounded by the clad, and a bottom surface deeper than the core formed so as to block the core. An optical waveguide circuit comprising: a mirror groove, wherein the first side surface of the core that is exposed is substantially perpendicular to the optical axis of the core, and the second side surface is substantially parallel to the first side surface. Opposing in parallel, the third side surface intersects the second side surface at an inner angle of 90 ° or more and smaller than 180 °, the fourth side surface intersects the third side surface at an outer angle smaller than 180 °, and the bottom surface A reflection part formed on the corner by pouring and curing a liquid curable resin into the corner with the second side surface and reflecting the light from the core to the side opposite to the bottom surface; The line of intersection between the side surface and the third side surface is the reflection of the reflecting portion. An optical waveguide circuit in a first side surface side than the intersection line formed between the third side surface and.

  The reflection part is preferably formed of a curable resin. It can be formed by pouring a liquid curable resin into a predetermined position of the mirror groove and curing. The reflecting portion has a slope at a corner between the bottom surface of the mirror groove and the second side surface, and is in contact with the bottom surface, the second side surface, and the third side surface. Further, the fourth side surface is arranged so as to intersect the third side surface at an outer angle smaller than 180 °. The intersection line formed between the fourth side surface and the third side surface is slightly closer to the first side surface than the intersection line formed between the reflection surface of the reflection portion and the third side surface. For this reason, since the curable resin poured into the mirror groove is clogged at the corners of the fourth side surface and the third side surface even if the flow is disturbed due to surface irregularities on the bottom surface of the mirror groove, the mirror groove is cured. Can be prevented from being filled with the conductive resin. Further, since the influence of surface irregularities on the bottom surface can be suppressed, a reflective portion having a flat surface can be formed. Therefore, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

  In the second invention of the present application, the bottom surface exhibits a larger contact angle with respect to a substance that forms a portion in contact with the bottom surface of the reflecting portion than a portion in which the reflecting portion does not have the reflecting portion. It is preferable.

  Similar to the first invention, the mirror groove is subjected to a surface treatment by an oblique vapor deposition method or the like. The bottom surface is divided into regions having different wettability, and the first side surface side of the bottom surface is divided into a large contact angle region that exhibits a larger contact angle with the curable resin and a small contact angle region that exhibits a smaller contact angle. Divided. The third side surface is also divided into a large contact angle region exhibiting a large contact angle with respect to the curable resin and a small contact angle region exhibiting a small contact angle. The fourth side exhibits a small contact angle. The curable resin poured into the mirror groove flows by selecting a small contact angle region exhibiting a smaller contact angle on the bottom surface and hits the third side surface. The curable resin rises a small contact angle region on the third side. The curable resin is dammed at the boundary between the large contact angle region and the small contact angle region on the bottom surface. Furthermore, even if the flow is disturbed due to surface irregularities or the like on the bottom surface of the mirror groove, it is blocked by the surface tension at the corners of the fourth side surface and the third side surface and does not flow into the large contact angle region on the bottom surface. Therefore, it is possible to form a reflection portion having a slope at the corner between the small contact angle region on the bottom surface and the second side surface.

In the second invention of the present application, when the outer angle formed by the third side surface and the fourth side surface is σ ° and the contact angle of the portion having the reflecting portion on the bottom surface is γ °, the σ is lower. It is preferable to satisfy Formula (2).
σ ≦ γ + 90 (2)
At this time, since the portion having the reflection portion on the bottom surface and the small contact angle region on the bottom surface substantially coincide, the contact angle γ indicates the contact angle of the small contact angle region on the bottom surface.

  The fourth side intersects the third side with an outer angle less than 180 °. The intersection line formed between the fourth side surface and the third side surface is slightly closer to the first side surface than the intersection line formed between the reflection surface of the reflection portion and the third side surface. For this reason, even if there is surface irregularity on the bottom surface, the curable resin is blocked by the surface tension at the corners of the fourth side surface and the third side surface, does not flow into the large contact angle region, and the mirror groove is hardened Filling with resin can be prevented. Further, by suppressing the influence of surface irregularities on the bottom surface, a reflective portion having a flat surface can be formed. More precisely, when the outer angle formed by the third side surface and the fourth side surface is σ ° and the contact angle of the small contact angle region on the bottom surface is γ °, the σ satisfies the above equation (2). Things are preferable. By arranging the third side surface and the fourth side surface so as to satisfy the above formula (2), even if the surface of the bottom surface is irregular and the flow of the curable resin is somewhat disturbed, the curable resin is It can be stopped by its own surface tension at the corners of the fourth and third sides.

  These inventions described above can be combined as much as possible.

  According to the present invention, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.

(Embodiment 1)
The first embodiment of the present application includes a clad formed on a flat substrate, a core that guides light surrounded by the clad, a mirror groove that is formed so as to block the core and has a bottom surface deeper than the core, The mirror groove has a first side surface exposed by the core substantially perpendicular to the optical axis of the core, and a second side surface substantially parallel to the first side surface. The third side surface intersects with the second side surface at an inner angle larger than 90 ° and smaller than 180 °, and the bottom surface reflects light from the core to the opposite side to the bottom surface at the corner with the second side surface. This is an optical waveguide circuit having a portion.

  The optical waveguide circuit according to the first embodiment will be described with reference to FIGS. FIG. 1 is a top view of the optical waveguide circuit according to the first and second embodiments. FIG. 2 is an optical waveguide circuit according to the first embodiment, and is a cross-sectional view taken along the plane A-A ′ of FIG. 1. An optical waveguide circuit 91 shown in FIGS. 1 and 2 includes a clad 11 formed on a flat substrate 10, a core 12 surrounded by the clad 11 to guide light, and a bottom surface 24 formed so as to block the core 12. Is an optical waveguide circuit 91 including a mirror groove 20 deeper than the core 12, and the mirror groove 20 has a first side surface 25 where the core 12 is exposed substantially orthogonal to the optical axis 101 of the core 12, The side surface 26 faces the first side surface 25 substantially in parallel, the third side surface 27 intersects the second side surface 26 at an inner angle greater than 90 ° and smaller than 180 °, and the bottom surface 24 is in contact with the second side surface 26. A reflection portion 21 that reflects light from the core 12 to the opposite side of the bottom surface 24 is provided at the corner.

As the optical waveguide circuit 91, it is preferable to use a silica glass optical waveguide circuit in which the cladding 11 and the core 12 are mainly composed of SiO ₂ , but it is not limited thereto. The quartz glass-based optical waveguide circuit has high performance with little optical loss. For example, the clad 11 and the core 12 may be a polymer optical waveguide circuit made of fluorinated polyimide or the like. The manufacturing process can be simplified and the cost can be reduced. The optical waveguide circuit 91 is preferably an embedded optical waveguide circuit. A slab type optical waveguide circuit may be used. The optical waveguide circuit 91 may be single mode or multimode.

  The substrate 10 is formed in a flat plate shape. It is preferable to use a silicon substrate. A quartz substrate, a polyimide substrate, or the like may be used. The clad 11 and the core 12 are preferably formed by a flame deposition method. It may be formed by a CVD (Chemical Vapor Deposition) method or the like.

  The mirror groove 20 is formed so as to block the traveling direction of light guided by the core 12. The mirror groove 20 is substantially orthogonal to the core 12, and the bottom surface 24 is deeper than the core 12. The depth may reach the substrate 10. The mirror groove 20 is preferably formed by a dry etching method. It can be formed precisely. A wet etching method, a sand blast method, a micro blast method, or the like may be used. The mirror groove 20 includes a bottom surface 24, a first side surface 25, a second side surface 26, a third side surface 27, and a reflecting portion 21. The first side surface 25 is a surface that is substantially orthogonal to the optical axis 101 of the core 12 and exposes the core 12. The core 12 is cut substantially orthogonally on the first side surface 25. On the first side surface 25, the light guided by the core 12 is emitted in the direction of the optical axis 101 of the core 12. The second side surface 26 is a surface facing the first side surface 25 substantially in parallel. The third side surface 27 intersects the second side surface 26 at an interior angle greater than 90 ° and less than 180 °. The reflecting portion 21 has a corner slope between the second side surface 26 and the bottom surface 24.

  The mirror groove 20 cuts the core 12 included in the optical waveguide circuit 91, takes out the guided light from the cut surface of the core 12 exposed on the first side surface 25, reflects the extracted guided light at the reflecting portion 21, It is for output to the outside. Light from the outside can also be reflected by the reflecting portion 21 and input to the core 12.

  The bottom surface 24 has a reflecting portion 21 at a corner with the second side surface 26. The reflecting portion 21 has a slope at the corner between the bottom surface 24 and the second side surface 26, and is a portion for reflecting the light from the core 12 to the opposite side to the bottom surface 24 and outputting it to the outside of the waveguide. On the contrary, it is also used to reflect light from the outside in the direction of the optical axis 101 of the core 12 and input it to the core 12. The reflecting portion 21 is preferably formed of a curable resin. As the curable resin, a photocurable resin, a thermosetting resin, or the like can be used. Examples of the photocurable resin include an ultraviolet curable resin, a visible light curable resin, and the like, and generally have a high curing speed and excellent adhesiveness. An epoxy resin is preferably used as the thermosetting resin. Excellent heat resistance, moisture resistance and adhesion, and high surface curability. For example, a phenol resin or an unsaturated polyester resin may be used.

  As shown in FIG. 1, the mirror groove 20 is preferably formed in an L shape when viewed from above, and communicates with the resin supply groove 30. By injecting the curable resin into the resin supply groove 30, it is possible to finely adjust the flow rate and flow rate of the curable resin poured into the mirror groove 20. The resin supply groove 30 may communicate with another mirror groove included in the optical waveguide circuit 91. The liquid curable resin poured into the corners of the bottom surface 24 and the second side surface 26 through the resin supply groove 30 advances through the corners due to the effect of surface tension, and cures at the corners, thereby reflecting the reflecting portion 21. Is formed. The reflecting portion 21 has a slope at the corner between the bottom surface 24 and the second side surface 26, and contacts the bottom surface 24, the second side surface 26, and the third side surface 27.

  The third side surface 27 preferably intersects the bottom surface 24 at a substantially right angle. Easy to form. The angle may be changed depending on the surface tension of the curable resin. Further, the third side surface 27 intersects the second side surface 26 at an inner angle greater than 90 ° and smaller than 180 °. The third side surface 27 stops the flow of the curable resin poured into the mirror groove 20. If an appropriate amount of curable resin is poured into the corners of the bottom surface 24 and the second side surface 26 of the mirror groove 20, the curable resin is caused by the surface tension of the bottom surface 24, the second side surface 26, and the third side surface 27. It remains at the corner between the bottom surface 24 and the second side surface 26. Therefore, it is possible to form the reflecting portion 21 having an inclined surface at the corner between the bottom surface 24 and the second side surface 26 without filling the mirror groove 20.

  The curable resin poured into the mirror groove 20 advances through the corners of the bottom surface 24 and the second side surface 26 by the surface tension and hits the third side surface 27. Since the third side surface 27 intersects with the second side surface 26 at an inner angle greater than 90 ° and smaller than 180 °, the third side surface 27 rises beyond the inclination angle of the reflecting portion 21 to be formed on the third side surface 27. Can be prevented. Therefore, it is possible to form the reflecting portion 21 having a flat slope with no excessive rising portion on the third side surface 27. In addition, since the mirror groove 20 can be prevented from being filled with the curable resin, the manufacturing yield can be improved. That is, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

(Embodiment 2)
In the second embodiment of the present application, in the first embodiment of the present application, the portion that does not have the reflecting portion on the bottom surface has a larger contact with the substance that forms the portion that contacts the bottom surface of the reflecting portion than the portion that has the reflecting portion. An optical waveguide circuit characterized by exhibiting a corner.

  An optical waveguide circuit according to the second embodiment will be described with reference to FIGS. FIG. 1 is a top view of the optical waveguide circuit 91 according to the first and second embodiments. FIG. 4 is an optical waveguide circuit 92 according to the second and third embodiments, and is a cross-sectional view taken along the plane A-A ′ of FIG. 1. Here, the cross-sectional view taken along the plane AA ′ of the optical waveguide circuit 91 of FIG. 1 is the optical waveguide circuit 91 of FIG. 2 according to the first embodiment and the optical waveguide circuit 92 of FIG. 4 according to the second embodiment. Indicated by The second embodiment is shown by the optical waveguide circuit 91 in FIG. 1 and the optical waveguide circuit 92 in FIG. 4, but since the two are the same, the optical waveguide circuit 92 is used as a representative. An optical waveguide circuit 92 shown in FIGS. 1 and 2 includes a clad 11 formed on a flat substrate 10, a core 12 surrounded by the clad 11 to guide light, and a bottom surface formed so as to block the core 12. 24 is an optical waveguide circuit including a mirror groove 20 deeper than the core 12, and the mirror groove 20 has a first side surface 25 where the core 12 is exposed substantially orthogonal to the optical axis 101 of the core 12, The side surface 26 faces the first side surface 25 substantially in parallel, the third side surface 27 intersects the second side surface 26 at an inner angle greater than 90 ° and smaller than 180 °, and the bottom surface 24 is in contact with the second side surface 26. The corner 21 has a reflection portion 21 that reflects light from the core 12 to the side opposite to the bottom surface 24, and a portion of the bottom surface 24 that does not have the reflection portion 21 is compared with a portion having the reflection portion 21. The substance that forms the part in contact with the bottom surface 24 On the other hand, a large contact angle is exhibited.

  As in the first embodiment, a curable resin is preferable as the substance that forms the portion in contact with the bottom surface 24 of the reflecting portion 21.

  The contact angle is the angle between the liquid surface and the solid surface at the boundary line where these three phases contact when the surface of the solid is in contact with the gas containing the liquid and its vapor (usually air). It is a corner represented by. When the contact angle is large, the droplet is close to a sphere, and when the contact angle is small, the droplet is close to a plane. A large contact angle is synonymous with good wettability, and a small contact angle is synonymous with poor wettability.

  As shown in FIG. 4, on the bottom surface 24, the second side surface 26 side, which is a region where the reflecting portion 21 is to be formed, is a small contact angle region 23, and the other part of the bottom surface 24 is a large contact angle region 22. To do. Surface treatment is performed so that the large contact angle region 22 exhibits a larger contact angle than the small contact angle region 23.

  Here, a surface treatment method for dividing the mirror groove 20 into regions having different contact angles will be described. However, it is not limited to the following method. First, Ti is deposited obliquely from the upper side of the mirror groove 20 to a thickness of about 0.1 μm. At this time, Ti is not vapor-deposited, that is, the shaded portion with respect to the vapor deposition direction is made to substantially coincide with the region where the reflecting portion 21 is to be formed. Since the reflection part 21 is scheduled to be formed at the corner of the second side face 26 and the bottom face 24, the vapor deposition is performed so that the second side face 26 becomes a shadow. Next, while rotating the optical waveguide circuit 92, Cr is deposited to a thickness of about 0.1 μm on the entire surface of the optical waveguide circuit 92 including the mirror groove 20 so as not to shadow. Next, the entire surface of the optical waveguide circuit 92 is immersed in dilute hydrofluoric acid, and Cr is lifted off with Ti to be removed. As a result of this process, Cr remains in the shadowed part of the Ti deposition direction in the previous process. Next, a surface treatment film is formed on the entire surface of the optical waveguide circuit 92. As the surface treatment film, a fluorine-based water repellent treatment agent can be used, but is not limited thereto. The surface treatment film exhibits a large contact angle with respect to the curable resin, and the contact angle with respect to the curable resin is preferably 45 ° or more. Finally, the entire surface of the optical waveguide circuit 92 is immersed in a Cr etching solution, and the surface treatment film is lifted off with Cr and removed. As a result of this process, the surface treatment film is lifted off and removed from the region where the reflection portion 21 is to be formed in the mirror groove 20, and the surface treatment film in other regions remains. The area where the surface treatment film is removed exhibits a smaller contact angle with respect to the curable resin than the area where the surface treatment film remains.

  Thus, the mirror groove 20 can be divided into regions having different contact angles by the above method. The bottom surface 24 has a large contact angle region 22 where the surface treatment film remains on the first side surface 25 side and exhibits a larger contact angle, and a smaller contact angle when the surface treatment film is removed on the second side surface 26 side. It is divided into a small contact angle region 23. Since the boundary between the large contact angle region 22 and the small contact angle region 23 is a boundary between the shadowed portion of the second side surface 26 by the oblique deposition and the deposited portion, It becomes substantially parallel to the second side surface 26. The third side surface 27 is also divided into a large contact angle region that exhibits a larger contact angle and a small contact angle region that exhibits a smaller contact angle. On the bottom surface 24 and the third side surface 27, the small contact angle region substantially coincides with the portion where the reflecting portion 21 is to be formed.

  The curable resin poured into the mirror groove 20 through the resin supply groove 30 flows by selecting the small contact angle region 23 exhibiting a smaller contact angle on the bottom surface 24 and hits the third side surface 27. The curable resin rises a small contact angle region on the third side surface 27. Since the third side surface 27 intersects with the second side surface 26 at an inner angle greater than 90 ° and smaller than 180 °, the curable resin rises over the boundary between the regions having different contact angles on the third side surface 27. This can be prevented. Further, since the curable resin is dammed at the boundary between the small contact angle region and the large contact angle region, the resin can be supplied until the hydraulic pressure and the atmospheric pressure are balanced, that is, until the inclined surface of the reflecting portion 21 becomes flatter. it can. That is, it is possible to form the reflecting portion 21 having a flat slope at the corner between the small contact angle region 23 and the second side surface 26 as compared with the first embodiment.

  Therefore, it is possible to form the reflective portion 21 that has no excessive rising portion on the third side surface 27 and has a flat slope as compared with the first embodiment. Further, since it is possible to prevent the curable resin from rising excessively on the third side surface 27, it is possible to prevent the mirror groove 20 from being filled with the curable resin.

Furthermore, in the second embodiment, the angle formed by 90 ° from the inner angle formed by the third side surface 27 and the second side surface 26 is θ °, and the inclination angle formed by the reflecting portion 21 and the bottom surface 24 is φ °. When the contact angle of the portion of the bottom surface 24 that does not have the reflecting portion 21 is Γ °, it is preferable that the θ satisfies the following formula (1).
θ ≧ sin ⁻¹ (cos Γ / sin φ) (1)
At this time, the contact angle Γ ° of the portion of the bottom surface 24 that does not have the reflecting portion 21 is the contact angle of the large contact angle region 22 of the bottom surface 24.

  Derivation of the above equation (1) will be described with reference to FIGS. FIG. 5 is a perspective view of a corner formed by the second side surface 26, the third side surface 27, and the bottom surface 24 when the second side surface 26 and the third side surface 27 meet at a right angle inner angle. FIG. 6 is a perspective view of a corner formed by the second side surface 26, the third side surface 27, and the bottom surface 24 when the second side surface 26 and the third side surface 27 intersect at an internal angle of (90 + θ) °.

  5 and 6 include a bottom surface 24, a second side surface 26 that intersects perpendicularly with the bottom surface 24, a third side surface 27 that intersects perpendicularly with the bottom surface 24, and the reflecting portion 21. In FIGS. 5 and 6, the boundary of the contact angle on the third side surface 27 and the boundary indicating the location where the reflection portion 21 is to be formed is indicated by a one-dot chain line, and the reflection portion 21, the bottom surface 24, and the third side surface 27. The boundary is shown by a broken line. A portion where the alternate long and short dash line and the broken line overlap is representatively shown by a broken line. In addition, for convenience, orthogonal coordinate axes are illustrated. The intersection of the second side surface 26, the third side surface 27, and the bottom surface 24 is the origin, and the intersection line with the second side surface 26 and the third side surface 27 is the intersection of the Z axis, the bottom surface 24, and the second side surface 26. Let the line be the Y-axis, the origin and the perpendicular of the second side surface 26 be the X-axis. In FIG. 6, the normal vector 41 of the slope of the reflecting portion 21 and the normal vector 42 of the third side surface 27 are set, the angle formed by the reflecting portion 21 and the bottom surface 24 is γ °, and the second side surface 26 And the third side surface 27 is defined as θ °, and the inner angle formed between the normal vector 42 on the third side surface and the normal vector 41 of the inclined surface of the reflecting portion 21 is defined as β °.

  In FIG. 5, since the third side surface 27 and the second side surface 26 intersect at a right angle, the curable resin rises on the third side surface 27 beyond the boundary where the contact angle differs due to surface tension. As shown in FIG. 6, in order to prevent the curable resin from rising on the third side surface 27, more strictly, the angle formed by the third side surface 27 and the inclined surface of the reflecting portion 21 is determined. The contact angle may be smaller than the contact angle of the large contact angle region 22 on the bottom surface 24. The angle formed between the third side surface 27 and the inclined surface of the reflecting portion 21 is equal to the internal angle formed by the normal vector 42 of the third side surface and the normal vector 41 of the inclined surface of the reflecting portion 21 with β °. That is, if β ≦ Γ, the curable resin can be prevented from rising on the third side surface 27.

In the equation, the normal vector 41 is represented by nr, the normal vector 42 is represented by nw, and the above equation (1) is derived. When each normal vector is displayed as a component,
nr = (sin θ, cos θ, 0)
nw = (sin φ, 0, cos φ).
Therefore, the inner product of the normal vector 41 and the normal vector 42 is
From nw · nr = | nr || nw | cosβ,
sinθsinφ = cosβ
θ = sin ⁻¹ (cos β / sin φ)
From β ≦ Γ,
θ ≧ sin ⁻¹ (cos Γ / sin φ).
Therefore, the above equation (1) was derived. At θ satisfying the above formula (1), the third side surface 27 is preferably arranged so as to intersect with the second side surface 26 so as to have an internal angle of (90 + θ) °. Therefore, more strictly, the curable resin can be prevented from rising on the third side surface 27 beyond the boundary between the large contact angle region and the small contact angle region.

(Embodiment 3)
The third embodiment of the present application includes a clad formed on a flat substrate, a core that guides light surrounded by the clad, a mirror groove that is formed so as to block the core and has a bottom surface deeper than the core, The mirror groove has a first side surface exposed by the core substantially perpendicular to the optical axis of the core, and a second side surface substantially parallel to the first side surface. The third side surface intersects with the second side surface at an inner angle of 90 ° or more and smaller than 180 °, the fourth side surface intersects with the third side surface at an outer angle smaller than 180 °, and the bottom surface is the second side surface. And a reflection portion that reflects light from the core to the opposite side of the bottom surface, and an intersection formed by the fourth side surface and the third side surface is a reflection surface of the reflection portion and the third side. On the first side surface from the line of intersection with the side surface, and on the bottom surface, No portion of the section is compared with the portion having the reflective portion, with respect to the material forming the portion in contact with the bottom surface of the reflective portion is an optical waveguide circuit characterized by exhibiting a high contact angle.

  An optical waveguide circuit according to a third embodiment will be described with reference to FIGS. FIG. 3 is a top view of the optical waveguide circuit 92 according to the third embodiment. FIG. 4 is an optical waveguide circuit according to the second and third embodiments, and is a cross-sectional view taken along the plane A-A ′ of FIG. 3. The optical waveguide circuit 92 shown in FIGS. 3 and 4 includes a clad 11 formed on a flat substrate 10, a core 12 that is surrounded by the clad 11 and guides light, and is formed so as to block the core 12. Is an optical waveguide circuit 92 including a mirror groove 20 deeper than the core 12, and the mirror groove 20 has a first side surface 25 where the core 12 is exposed substantially perpendicular to the optical axis 101 of the core 12, The side surface 26 faces the first side surface 25 substantially parallel, the third side surface 27 intersects the second side surface 26 at an inner angle of 90 ° or more and smaller than 180 °, and the fourth side surface 28 is an outer angle smaller than 180 °. At the corner of the second side surface 26, the bottom surface 24 has a reflecting portion 21 that reflects the light from the core 12 to the opposite side of the bottom surface 24, and the fourth side surface 28 and the third side surface The intersecting line formed with the side surface 27 of the reflecting portion is the reflecting surface of the reflecting portion 21 and the third side. 27 on the first side face 25 from the intersection line formed with the line 27, and in the bottom surface 24, the part not having the reflection part 21 forms a part in contact with the bottom surface 24 of the reflection part 21 compared to the part having the reflection part 21. It exhibits a large contact angle with respect to the substances to be used.

  As in the second embodiment, a curable resin is preferable as the substance that forms the portion in contact with the bottom surface 24 of the reflecting portion 21. Moreover, it is preferable that the inclined surface of the reflection part 21 is metal-deposited. A precise reflecting surface is formed. For example, a metal film may be bonded to the inclined surface of the reflecting portion 21. Au is preferably used as the metal to be deposited. Ag, Cu, Pt, Cr, etc. may be used.

  The curable resin poured into the mirror groove 20 through the resin supply groove 30 flows by selecting the small contact angle region 23 and hits the third side surface 27 as in the second embodiment. The curable resin tends to rise beyond the boundary on the boundary line of the contact angle. In particular, the curable resin crosses the boundary of the contact angle at the intersection of the third side surface 27, the bottom surface 24, and the reflection surface of the reflection portion 21. There is a tendency to rise. For this reason, when the bottom surface 24 has surface irregularities or the like, and a slight flow of the curable resin is found, the curable resin is near the intersection of the third side surface 27, the bottom surface 24, and the reflective surface of the reflecting portion 21. May flow beyond the boundary of the contact angle.

  In the third embodiment, a fourth side surface 28 is provided, the fourth side surface 28 intersects with the third side surface 27 at an outer angle smaller than 180 °, and the fourth side surface 28 and the third side surface 27 The intersecting line formed by is located closer to the first side face 25 than the intersecting line formed between the reflecting surface of the reflecting portion 21 and the third side face 27. The point of intersection of the fourth side surface 28 and the third side surface 27 with the bottom surface 24 is slightly more than the point of intersection of the third side surface 27, the bottom surface 24 and the reflecting surface of the reflecting portion 21. It is preferably on the 25th side. Since the bottom surface 24 has surface irregularities and the like, and the flow of the curable resin is disturbed, the curable resin can be blocked at the corners of the fourth side surface 28 and the third side surface 27, so that the mirror groove 20 is hardened. Filling with resin can be prevented. Moreover, since the influence of the surface irregularity etc. of the bottom face 24 can be suppressed, the reflection part 21 with a flat surface can be formed. Therefore, it is possible to provide an optical waveguide circuit with high controllability of the reflection angle and good manufacturing yield.

Furthermore, in the third embodiment, when the external angle formed by the third side surface 27 and the fourth side surface 28 is σ °, and the contact angle of the portion having the reflecting portion 21 on the bottom surface 24 is γ °, σ is It is preferable that the following formula (2) is satisfied.
σ ≦ γ + 90 (2)
At this time, the contact angle γ of the portion having the reflecting portion 21 on the bottom surface 24 is a contact angle of the small contact angle region 23 of the bottom surface 24.

  Derivation of the above equation (2) will be described with reference to FIG. FIG. 7 is a top view of a corner formed by the third side surface 27 and the fourth side surface 28 when the third side surface 27 intersects the fourth side surface 28 at an external angle of σ °. 7 shows a second side surface 26, a bottom surface 24 (not shown) and a third side surface 27 perpendicular to the second side surface 26, and a third side surface 27 perpendicular to the bottom surface 24 (not shown). A fourth side surface 28 that intersects at an external angle of σ ° and the reflection portion 21 are included. In FIG. 7, for convenience, an auxiliary line 43, an auxiliary line 43, and a third line are formed at the boundary between the large contact angle region 22 (not shown) and the small contact angle region 23 (not shown) of the bottom surface 24 (not shown). An auxiliary line 44 passing through the intersection with the side surface 27 and parallel to the fourth side surface 28 is shown by a one-dot chain line, and a boundary between the reflecting portion 21 and the bottom surface 24 (not shown) is shown by a broken line. A portion where the one-dot chain line and the broken line overlap is represented by a one-dot chain line as a representative. The angle formed by the auxiliary line 43 and the auxiliary line 44 is (σ−90) °. The fourth side surface 28 becomes a small contact angle region due to the balance between the angle formed by the fourth side surface and the third side surface and the angle at which the oblique deposition method or the like is performed.

  In order to stop the curable resin at the corners of the fourth side surface 28 and the third side surface 27 even if the bottom surface 24 has surface irregularities and the flow of the curable resin is disturbed, more precisely, the auxiliary line 43 And the auxiliary line 44 need only be smaller than the contact angle γ of the small contact angle region 23 (not shown). The above equation (2) is derived from the equation modification of σ−90 ≦ γ. If the fourth side surface 28 is arranged so as to satisfy the condition of the above formula (2), the curable resin is the third side surface at the intersection of the third side surface 27, the bottom surface 24, and the reflecting surface of the reflecting portion 21. 27, the flow into the large contact angle region 22 beyond the contact angle boundary of the bottom surface 24 can be blocked at the corners of the third side surface 27 and the fourth side surface 28.

  Next, the operation of the optical waveguide circuit in the first embodiment, the second embodiment, and the third embodiment will be described with reference to FIGS. The light guided by the core 12 is emitted from the cut surface of the core 12 on the first side surface 25 in the mirror groove 20. The light emitted from the cut surface of the core 12 is reflected to the opposite side of the bottom surface 24 by the reflecting surface of the reflecting portion 21. According to the present invention, the flat reflecting portion 21 can be formed, and the inclination angle φ formed by the reflecting portion 21 and the bottom surface 24 can be determined with high accuracy, so that the controllability of the reflection angle of the reflected light is high. Therefore, the reflected light can be extracted outside the optical waveguide circuit with low loss. Further, light can be emitted from the outside of the optical waveguide circuit toward the reflecting surface of the reflecting portion 21 and reflected by the reflecting surface, so that the light can be input to the core 12 with high accuracy. You may install a light receiving element, another optical waveguide, etc. in the upper part of the mirror groove | channel 20 of an optical waveguide circuit. By making the inclination angle of the reflecting portion 21 approximately 45 °, vertical input / output of guided light can be performed with high accuracy. In addition, it is preferable to match the refractive index by filling a matching oil or the like at a connection portion between the mirror groove and another optical component.

  As described above, in the optical waveguide circuit 91, the bottom surface 24 is divided into the large contact angle region 22 and the small contact angle region 23, and the third side surface 27 is greater than 90 ° and 180 ° with respect to the second side surface 26. More precisely, by intersecting at a smaller interior angle, more precisely, using the angle θ that satisfies the condition of the above formula (1), the second side surface 26 intersects at an interior angle of (90 + θ) °, so that the third side surface 27 A flat reflecting portion 21 with no excessive rise is formed. Further, the mirror groove 20 can be prevented from being filled with the curable resin. Further, when the fourth side surface 28 intersects the third side surface 27 at an outer angle smaller than 180 °, more precisely, the fourth side surface 28 intersects at the outer angle of σ ° satisfying the condition of the above expression (2), thereby the mirror groove Even if the bottom surface 24 of the surface 20 has irregularities, the curable resin is blocked at the corners of the fourth side surface 28 and the third side surface 27, and the mirror groove 20 is prevented from being filled with the curable resin. Can do. Moreover, since the influence of the surface irregularity etc. of the bottom face 24 can be suppressed, the reflection part 21 with a flat surface can be formed. Therefore, the controllability of the reflection angle can be increased and the manufacturing yield can be improved.

  Examples of the present invention will be described in detail. However, the present invention is not limited to the following examples.

As the optical waveguide circuit, an embedded optical waveguide circuit in which a silica-based optical waveguide circuit made of glass containing SiO ₂ as a main component on a Si substrate was formed by a flame deposition method was used. The relative refractive index difference between the core and the clad is 0.5%, the thickness of the lower clad is 20 μm, the core is 7 μm square, and the thickness including the upper and lower clads is 40 μm. As shown in FIGS. 1 and 3, a resin supply groove is provided at a desired location in the optical waveguide circuit. The resin supply groove is L-shaped, the groove length D is 200 μm, the groove width W is 70 μm, and the width of the resin supply groove. A mirror groove having a depth of 30 μm and a depth of 40 μm reaching the substrate to the bottom was formed by dry etching. The third side surface of the mirror groove intersects at 90 ° with respect to the bottom surface. The mirror groove was subjected to a surface treatment with a fluorine-based water repellent agent, and was divided into a large contact angle region and a small contact angle region. The contact angle in the large contact angle region was 75 ° to 80 °, and the contact angle in the small contact angle region was 10 ° to 30 °. Epoxy resin as a curable resin was dropped into the resin supply groove and poured into the small contact angle region of the mirror groove to form a reflection portion having an inclination angle of approximately 45 °.

  Regarding the first invention of the present application, the manufacturing yield was examined when the internal angle at which the third side intersects the second side was changed. Specifically, when the inner angle formed by the third side surface and the second side surface is (θ + 90) °, 264 pieces of nine kinds of mirror grooves each having θ changed from 0 to 40 every 5 are formed. A total of 2376 mirror grooves distributed uniformly on a 4-inch wafer were examined. With respect to the mirror groove with θ = 0, the yield was 95.1%, and 13 mirror grooves were filled with a curable resin at the periphery of the wafer. On the other hand, the yield was 100% for the mirror groove with 5 ≦ θ ≦ 40. For example, when the contact angle Γ = 75 in the large contact angle region is substituted into the above formula (1) and calculated, the curable resin is prevented from rising on the third side surface when θ is about 21 or more. Can do. However, since 5 ≦ θ ≦ 40 and the yield is 100%, it is possible to prevent the mirror groove from being filled without completely preventing the rising, and the yield can be improved.

  Further, regarding the second invention of the present application, the manufacturing yield when the inner angle formed by the third side surface with respect to the second side surface is fixed at 90 ° and the outer angle formed by the fourth side surface with respect to the third side surface is changed. I investigated. Specifically, when the outer angle formed by the fourth side surface with respect to the third side surface is σ °, 475 mirror grooves of 475 each having σ changed every 10 from 100 to 60 were created. A total of 2375 mirror grooves were uniformly distributed on a 4-inch wafer. For the mirror groove with σ = 100, the yield was 97.7%. Eleven mirror grooves in the periphery of the wafer were filled with curable resin, and irregular shapes of the inclined surface of the reflecting portion occurred. On the other hand, the yield of the mirror groove with 110 ≦ σ ≦ 60 was 100%. The mirror groove with σ = 100 was filled with a curable resin or the irregular shape of the inclined surface of the reflecting portion was calculated by substituting into the above equation (2) and calculating the contact angle γ ° in the small contact angle region. This is thought to be due to a partial area of 10 ° or less.

  It turns out that the yield improvement effect of the reflection part was acquired by the above Example. Therefore, according to the present invention, the in-process inspection in the manufacturing of the reflecting portion can be omitted, and the price of the application device using the vertical input / output structure of the guided light by the reflecting portion can be reduced. Furthermore, it was confirmed that the rising on the third side face was prevented. Therefore, according to the present invention, it is possible to realize a reflecting portion having a flat slope with little distortion.

  Since the present invention can realize a flat reflecting surface with little distortion and little wavefront distortion or scattering of incident light, it is particularly effective for inputting semiconductor laser light into a waveguide that requires a high-performance optical path conversion function. is there.

It is a top view of the optical waveguide circuit concerning a 1st embodiment and a 2nd embodiment of this application. FIG. 2 is an optical waveguide circuit according to the first embodiment, and is a cross-sectional view taken along the plane A-A ′ of FIG. 1. It is a top view of the optical waveguide circuit concerning a 3rd embodiment. FIG. 4 is a cross-sectional view taken along the line A-A ′ of FIGS. 1 and 3, illustrating optical waveguide circuits according to second and third embodiments. FIG. 6 is a perspective view of a corner formed by a second side surface, a third side surface, and a bottom surface when the second side surface and the third side surface meet at a right angle. FIG. 10 is a perspective view of a corner formed by a second side surface, a third side surface, and a bottom surface when the second side surface and the third side surface intersect at an internal angle of (90 + θ) °. FIG. 6 is a top view of a corner formed by a third side surface and a fourth side surface when the third side surface intersects the fourth side surface at an external angle of σ °.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 11 Cladding 12 Core 20 Mirror groove 21 Reflecting part 22 Large contact angle region 23 Small contact angle region 24 Bottom surface 25 First side surface 26 Second side surface 27 Third side surface 28 Fourth side surface 30 Resin supply groove 41, 42 Normal vector 43, 44 Auxiliary line 91 Optical waveguide circuit 92 Optical waveguide circuit 101 Optical axis

Claims (6)

A clad formed on a flat substrate;
A core that guides light surrounded by the cladding;
An optical waveguide circuit comprising a mirror groove formed to shield the core and having a bottom surface deeper than the core,
The mirror groove is
The exposed first side surface of the core is substantially orthogonal to the optical axis of the core,
The second side surface is substantially parallel to the first side surface;
The third side intersects the second side at an interior angle greater than 90 ° and less than 180 °;
An optical waveguide having a reflecting portion that reflects light from the core to the opposite side of the bottom surface , which is formed at the corner by pouring and curing a liquid curable resin into the corner with the second side surface. circuit.   The bottom surface has a larger contact angle with respect to a substance that forms a portion of the reflecting portion that contacts the bottom surface than a portion where the reflecting portion does not have the reflecting portion. 2. An optical waveguide circuit according to 1. An angle obtained by drawing 90 ° from an inner angle formed by the third side surface and the second side surface is θ °,
The angle of inclination formed by the reflecting portion with the bottom surface is φ °,
When the contact angle of the portion that does not have the reflective portion on the bottom surface is Γ °,
The optical waveguide circuit according to claim 2, wherein the θ satisfies the following expression (1).
θ ≧ sin ⁻¹ (cos Γ / sin φ) (1) A clad formed on a flat substrate;
A core that guides light surrounded by the cladding;
An optical waveguide circuit comprising a mirror groove formed to shield the core and having a bottom surface deeper than the core,
The mirror groove is
The exposed first side surface of the core is substantially orthogonal to the optical axis of the core,
The second side surface is substantially parallel to the first side surface;
The third side intersects the second side at an internal angle of 90 ° or more and less than 180 °,
The fourth side intersects the third side with an outer angle less than 180 °,
The bottom surface is formed at the corner by pouring and curing a liquid curable resin into the corner with the second side surface, and has a reflecting portion that reflects light from the core to the opposite side of the bottom surface,
An optical waveguide circuit in which an intersection line formed between the fourth side surface and the third side surface is located closer to a first side surface than an intersection line formed between the reflection surface of the reflection portion and the third side surface.   The bottom surface has a larger contact angle with respect to a substance that forms a portion of the reflecting portion that contacts the bottom surface than a portion where the reflecting portion does not have the reflecting portion. 5. An optical waveguide circuit according to 4. The outer angle formed by the third side surface and the fourth side surface is σ °,
When the contact angle of the portion having the reflective portion on the bottom surface is γ °,
The optical waveguide circuit according to claim 5, wherein the σ satisfies the following expression (2).
σ ≦ γ + 90 (2)

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