JP5472014B2 - Optical waveguide device and method for manufacturing optical waveguide device - Google Patents

Description

  The present invention relates to an optical waveguide element and a method for manufacturing the optical waveguide element.

  In an optical waveguide element in which an optical waveguide is formed on the surface of a substrate, the propagation light in the optical waveguide is monitored in order to control the light wave propagating through the optical waveguide. As a method for monitoring the propagation light, a light receiving element in which the light that branches the optical waveguide and taps a part of the propagation light, or the radiation mode light that is radiated out of the optical waveguide from the combined portion of the optical waveguide is arranged on the side surface of the substrate And a method of receiving evanescent light oozing out around the optical waveguide with a light receiving element disposed at the upper part of the optical waveguide (see, for example, Patent Document 1).

  On the other hand, when a dielectric substrate is used as the substrate, charges may accumulate on the substrate surface due to the pyroelectric effect, thereby degrading the optical characteristics of the optical waveguide device. As a countermeasure against this, a configuration in which a conductive film is formed on the back surface (the surface opposite to the surface on which the optical waveguide is formed) and the side surface of the substrate is known. According to this configuration, the charge accumulated on the substrate surface can be discharged to the outside of the substrate via this conductive film and escaped, and the above characteristic deterioration can be prevented.

JP 2001-215371 A

  Incidentally, in fixing the light receiving element to the substrate, a thermosetting adhesive, a photocurable adhesive, or the like is used. Thermosetting adhesives generally have a long curing time. For this reason, there is a problem that the time required for the bonding process becomes long, and there is a problem that it is easily affected by misalignment during curing, resulting in a decrease in mounting position accuracy and a deterioration in characteristics. Therefore, it is considered preferable to use a photocurable adhesive for fixing the light receiving element and the substrate.

  However, in the structure in which the conductive film is formed on the back surface and the side surface of the substrate as described above, the conductive film blocks light, so that light cannot be irradiated from the back surface side of the substrate, and the space between the light receiving element and the substrate. The adhesive applied to the resin cannot be cured. The adhesive protruding from between the light receiving element and the substrate can be cured by irradiating light from an oblique side of the light receiving element, but the strength after curing is insufficient.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an optical waveguide element and an optical waveguide capable of fixing a light receiving element to a substrate on which a conductive film is formed by using a photocurable adhesive. The object is to provide a method for manufacturing an element.

  The present invention has been made to solve the above-described problems, and includes a substrate having an electro-optic effect, an optical waveguide formed on the surface of the substrate, and a propagation formed on the surface of the substrate through the optical waveguide. An electrode for controlling a light wave to be transmitted; a light receiving element that monitors a part of the light wave that is fixed to the substrate by a photocurable adhesive and propagates through the optical waveguide; and a surface opposite to the surface of the substrate on which the optical waveguide is formed And a conductive film formed on another surface, a conductive film non-forming portion that does not form the conductive film is provided on a part of the opposing surface, and the substrate is interposed from the opposing surface side through the substrate. An optical waveguide element characterized in that the light curable adhesive can be irradiated with light.

  According to this structure, light can be irradiated to the photocurable adhesive between a light receiving element and a board | substrate through a conductive film non-formation part, and an adhesive agent can be hardened. Therefore, even if it is a board | substrate with which the electrically conductive film was formed, a light receiving element can be fixed to a board | substrate using a photocurable adhesive agent.

  In the optical waveguide element according to the present invention, the conductive film non-forming portion is provided in a portion of the facing surface excluding a portion facing the working portion on the substrate surface where the electrode is formed. It is characterized by.

  According to this configuration, the conductive film is present near the electrode, and the portion where the conductive film non-formed portion is present is limited to the portion away from the electrode. Therefore, charges generated by the pyroelectric effect in the vicinity of the electrode can be efficiently released outside the substrate through the conductive film.

  In the optical waveguide element according to the present invention, the conductive film non-forming portion is an opening formed in the conductive film.

  According to this configuration, light can be irradiated to the photocurable adhesive between the light receiving element and the substrate through the opening. In addition, since the area of the conductive film non-forming portion does not need to be increased more than necessary, the area of the conductive film can be increased, and the charges generated by the pyroelectric effect can be efficiently released to the outside of the substrate.

  According to the present invention, in the optical waveguide element described above, the shape of the opening is circular, rectangular, or substantially similar to the bonding surface of the light receiving element.

  Further, the present invention provides a substrate having an electro-optic effect, an optical waveguide formed on the surface of the substrate, an electrode formed on the surface of the substrate for controlling a light wave propagating through the optical waveguide, and a photocurable adhesive A light receiving element that monitors a part of a light wave that is fixed to the substrate by an agent and propagates through the optical waveguide, a conductive film that is formed on an opposite surface of the surface on which the optical waveguide is formed on the substrate, and another surface; The method of manufacturing an optical waveguide device comprising: a step of irradiating light to the photocurable adhesive through the substrate from a conductive film non-forming portion provided on a part of the facing surface. It is a manufacturing method of an optical waveguide device.

  Further, the present invention provides an interference fringe indicating a thickness state of the photocurable adhesive through the conductive film non-forming portion before or after the light irradiation step in the method for manufacturing an optical waveguide element. The method includes a step of inspecting.

  According to this configuration, it is possible to accurately discriminate between a non-defective product and a defective product regarding the adhesion state between the light receiving element and the substrate by inspection of interference fringes.

Further, the present invention provides the above-described method for manufacturing an optical waveguide element, wherein the photocurable adhesive has a viscosity of 1000 cp or less, and when the photocurable adhesive is cured, the light receiving element is attached to the substrate. The pressing pressure is 50 to 1000 g / mm ² .

  According to the present invention, it is possible to fix a light receiving element to a substrate on which a conductive film is formed using a photocurable adhesive.

It is a figure which shows the structure of the optical waveguide element by the 1st Embodiment of this invention. It is a figure explaining the process of fixing a light receiving element to a substrate. It is a figure which shows the structure of the optical waveguide element by the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an optical waveguide device 1 according to the first embodiment of the present invention.

  In FIG. 1, the optical waveguide element 1 includes a substrate 10 and a light receiving element 20.

  The substrate 10 is a substrate having an electro-optic effect, and is, for example, a dielectric crystal such as lithium niobate (LN) or lithium tantalate (LT).

  As shown in the top view of FIG. 1, optical waveguides 101 to 104 and electrodes 105 to 107 are formed on the surface of the substrate 10.

  The input waveguide 101 is connected to one end of the first branch waveguide 102 and one end of the second branch waveguide 103. The other end of the first branch waveguide 102 and the other end of the second branch waveguide 103 are connected to the output waveguide 104. Thus, a Mach-Zehnder type waveguide is configured.

  The first electrode 105 is provided along the first branch waveguide 102 between the first branch waveguide 102 and the edge of the substrate 10. The second electrode 106 is provided between the first branch waveguide 102 and the second branch waveguide 103 along the first branch waveguide 102 and the second branch waveguide 103. The third electrode 107 is provided between the second branch waveguide 103 and the edge of the substrate 10 along the second branch waveguide 103. A predetermined voltage is supplied to each of these electrodes 105 to 107 from the outside of the optical waveguide device 1 through an electric wiring (not shown).

  Thus, the optical waveguide element 1 applies an electric field from the first electrode 105, the second electrode 106, and the third electrode 107 to the first branch waveguide 102 and the second branch waveguide 103 of the Mach-Zehnder type waveguide. Thus, the refractive indexes of the first branch waveguide 102 and the second branch waveguide 103 are changed by the electro-optic effect. That is, the optical waveguide device 1 is configured as a modulator that modulates light waves propagating through the first branch waveguide 102 and the second branch waveguide 103 by the electric fields from the electrodes 105 to 107.

  Here, the light wave propagating through the region indicated by the dotted frame in the top view of FIG. 1, that is, the first branching waveguide 102 and the second branching waveguide 103 of the Mach-Zehnder type waveguide is caused by the electrodes 105 to 107. A region that is affected by an electric field is defined as an “action portion”.

  As shown in the side view of FIG. 1, a conductive film 110 is formed on the entire side surface of the substrate 10.

  As shown in the bottom view of FIG. 1, a conductive film 120 is formed on the back surface of the substrate 10 (the surface facing the surface on which the optical waveguide and electrodes are formed) except for a part of the back surface. A portion where the conductive film 120 is not formed is referred to as a conductive film non-forming portion 130. As shown in the bottom view of FIG. 1, the position of the conductive film non-forming part 130 is a position facing a fixed position of the light receiving element 20 described later, and an action part of the substrate 10 (see the top view of FIG. 1). It is a non-relative position. In other words, the conductive film 120 exists in the part of the back surface facing the action part, and the conductive film non-formation part 130 is located at a location away from the action part.

  The material of the conductive film 110 on the side surface and the conductive film 120 on the back surface is, for example, Au, Ti, Si, or the like.

  Since the conductive films 110 and 120 are formed on the side surface and the back surface of the substrate 10 as described above, the charges accumulated on the surface of the substrate 10 due to the pyroelectric effect are discharged to the outside of the substrate 10 through the conductive films 110 and 120. It is possible to let it escape. Here, although the pyroelectric effect is likely to occur in the vicinity of the electrodes 105 to 107, the conductive film 120 is present in the portion near the electrodes 105 to 107 on the back surface of the substrate, so that the charges accumulated on the substrate 10 are efficiently used. It can discharge well. Note that at least one of the conductive films 110 and 120 is electrically connected to a conductive casing (not shown) via a conductive adhesive or the like.

  As shown in the top view and the side view of FIG. 1, the light receiving element 20 is fixed to the substrate 10 so as to be in contact with the surface of the substrate 10 above the output waveguide 104. The light receiving surface of the light receiving element 20 is directed to the substrate 10 side. The light receiving element 20 is used to monitor the power of the light wave propagating through the output waveguide 104. Evanescent light that has oozed out of the output waveguide 104 is taken in from the light receiving surface of the light receiving element 20, and Power is detected.

  A light curable adhesive is used to fix the light receiving element 20 to the substrate 10. Hereinafter, the process of fixing the light receiving element 20 to the substrate 10 will be described with reference to FIG.

First, as a step (A), a photo-curing adhesive (viscosity 1000 cp or less) is applied between the light receiving element 20 (light receiving surface) and the substrate 10 with the light receiving surface of the light receiving element 20 facing the substrate 10 side. Then, the light receiving element 20 and the substrate 10 are brought into close contact with each other, and the light receiving element 20 is pressed against the substrate 10 with a pressure of 50 to 1000 g / mm ² . Then, UV light (ultraviolet light) is irradiated obliquely from above the light receiving element 20 to cure the adhesive leaking out around the light receiving element 20. The irradiation time of UV light is, for example, within 1 minute, and preferably about 10 seconds. In this state, only the adhesive leaking around the light receiving element 20 is cured (temporarily fixed), and the UV light does not reach the adhesive applied to the contact surface between the light receiving element 20 and the substrate 10. Not cured. Therefore, the adhesive strength between the light receiving element 20 and the substrate 10 is not sufficient, but the light receiving element 20 is not peeled off from the substrate 10 unless a large force is applied. Here, peeling and fracture of the adhesive can be prevented by setting the pressing pressure within the above range. Further, since the UV light irradiation time (adhesive curing time) is short, the positional deviation between the light receiving element 20 and the substrate 10 during curing is small, and high-accuracy positioning is possible.

  Next, as a step (B), an uncured portion of the adhesive between the light receiving element 20 and the substrate 10 is observed from the back surface side of the substrate 10 through the conductive film non-forming portion 130, and interference fringes appearing in the portion are observed. inspect. The appearance of the interference fringes reflects the thickness and uniformity of the adhesive between the light receiving element 20 and the substrate 10. By examining the interference fringes, it can be determined whether or not the application state of the adhesive is in an appropriate state, and a good product and a defective product can be discriminated. In the case of a defective product, the light receiving element 20 and the substrate may be peeled off once and the process (A) may be performed again without proceeding to the next process (C).

Next, as a step (C), the adhesive remaining uncured between the light receiving element 20 and the substrate 10 is irradiated with UV light from the back surface side of the substrate 10 through the conductive film non-forming portion 130, and the adhesive To cure. The irradiation time of UV light is, for example, about 1 to several minutes. By this step, all the adhesive applied to the contact surface between the light receiving element 20 and the substrate 10 is cured, and the light receiving element 20 and the substrate 10 are fixed with sufficient adhesive strength. Since a part of the adhesive is already cured in the previous step (A), it is not necessary to press the light receiving element 20 against the substrate 10 when the adhesive is cured in this step (C). However, the light receiving element 20 may be pressed against the substrate 10 at a pressure of 50 to 1000 g / mm ² in the same manner as in the step (A) in order to reliably prevent the adhesive from peeling or breaking.

  Next, as in step (D), as in step (B), the adhesive between the light receiving element 20 and the substrate 10 is observed from the back surface side of the substrate 10 through the conductive film non-forming portion 130 and appears in the portion. Check for interference fringes. By examining the interference fringes, it can be determined whether or not the cured state of the adhesive is in an appropriate state, and a good product and a defective product can be discriminated.

  As described above, according to the optical waveguide device 1 of the present embodiment, the photocurable adhesive between the light receiving element 20 and the substrate 10 can be irradiated with UV light through the conductive film non-forming portion 130, and adhesion is achieved. The agent can be cured. Further, since the curing of the adhesive in the step (B) can be completed in a short time, the accuracy of the fixing position of the light receiving element 20 can be improved.

FIG. 3 is a diagram showing a configuration of the optical waveguide device 2 according to the second embodiment of the present invention.
The difference between the optical waveguide device 2 of the present embodiment and the optical waveguide device 1 of the first embodiment is the shape of the conductive film non-forming portion 140.

  As shown in the bottom view of FIG. 3, the conductive film 120 is formed on the back surface of the substrate 10 of the optical waveguide element 2 so that the conductive film non-forming portion 140 has a circular opening. Similarly to the first embodiment, the position of the conductive film non-forming portion 140 is a position facing the fixed position of the light receiving element 20 and a position not facing the action portion of the substrate 10 (see the top view of FIG. 3). .

  The same effect as that of the optical waveguide device 1 of the first embodiment can be obtained by the optical waveguide device 2 having such a configuration. Furthermore, according to the optical waveguide device 2 of the present embodiment, since the conductive film 120 has a larger area than that of the first embodiment, the charges accumulated on the substrate 10 due to the pyroelectric effect can be discharged more efficiently than in the first embodiment. Is possible.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to
For example, in FIG. 3, the shape of the conductive film non-forming portion 140 (opening) is circular, but may be a shape (substantially similar shape) matched to the shape of the bottom surface of the light receiving element 20 or a rectangle.
Further, the position where the light receiving element 20 is bonded to the substrate 10 is not limited to the upper part of the output waveguide 104, and may be the upper part of the input waveguide 101 or the like.
The configuration of the optical waveguide may be a configuration other than the Mach-Zehnder type waveguide as shown in FIG. 1 or FIG.
Furthermore, it is good also as a structure which adhere | attaches the light receiving element 20 on the side surface of the board | substrate 10 according to the structure of an optical waveguide.

  DESCRIPTION OF SYMBOLS 1, 2 ... Optical waveguide element 10 ... Board | substrate 20 ... Light receiving element 101 ... Input waveguide 102 ... 1st branch waveguide 103 ... 2nd branch waveguide 104 ... Output waveguide 105 ... 1st electrode 106 ... 2nd electrode 107 ... Third electrode 110, 120 ... conductive film 130, 140 ... conductive film non-formation part

Claims (7)

A substrate having an electro-optic effect, an optical waveguide formed on the surface of the substrate, an electrode formed on the surface of the substrate for controlling a light wave propagating through the optical waveguide, and fixed to the substrate by a photocurable adhesive A light receiving element that monitors a part of a light wave propagating through the optical waveguide, and a conductive film formed on an opposite surface of the surface on which the optical waveguide is formed and on another surface of the substrate. ,
A conductive film non-formation portion that does not form the conductive film is provided on a part of the facing surface, and the photocurable adhesive can be irradiated with light from the facing surface side through the substrate. Optical waveguide element.   2. The conductive film non-forming portion is provided in a portion of the facing surface excluding a portion facing the action portion on which the electrode is formed on the substrate surface. Optical waveguide element.   The optical waveguide element according to claim 1, wherein the conductive film non-forming portion is an opening formed in the conductive film.   4. The optical waveguide element according to claim 3, wherein the shape of the opening is circular, rectangular, or substantially similar to an adhesive surface of the light receiving element. A substrate having an electro-optic effect, an optical waveguide formed on the surface of the substrate, an electrode formed on the surface of the substrate for controlling a light wave propagating through the optical waveguide, and fixed to the substrate by a photocurable adhesive A light receiving element that monitors a part of the light wave propagating through the optical waveguide, and a conductive film formed on an opposite surface of the surface on which the optical waveguide is formed on the substrate and on another surface. In the manufacturing method,
A method for manufacturing an optical waveguide device, comprising: irradiating light to the photocurable adhesive through the substrate from a conductive film non-forming portion provided on a part of the facing surface.   6. The method according to claim 5, further comprising a step of inspecting interference fringes indicating a thickness state of the photocurable adhesive through the conductive film non-forming portion before or after the step of irradiating the light. Manufacturing method of optical waveguide element. The viscosity of the photocurable adhesive is 1000 cp or less, and the pressure for pressing the light receiving element against the substrate when the photocurable adhesive is cured is 50 to 1000 g / mm ^2. The manufacturing method of the optical waveguide element of Claim 5 or Claim 6 to do.

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