JP2007178643A - Optical waveguide device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide device that can improve latitude of design without increasing connection loss, in connecting to an optical waveguide formed on a substrate an optical fiber cable guided in a groove formed thereon by anisotropic etching. <P>SOLUTION: In the optical waveguide device 1, in the end of the substrate 10 on which the optical waveguide 12 is formed, there is formed a V groove 111 for the purpose of passive alignment with the optical fiber cable 13, in the V groove forming face SF2 recessed by a prescribed depth d from the surface position of the substrate face SF1 on which the optical waveguide 12 is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical waveguide device connected to an optical fiber cable guided by a groove formed by anisotropic etching.

  In recent years, with the increase in data communication speed, there is an optical waveguide device as a communication device that performs low-loss and broadband communication in place of communication using a conventional metallic cable.

  In the optical waveguide device, it is important to accurately align the connection portions of the optical waveguides in order to reduce the loss due to the position with respect to the core that guides light and the angle shift. An optical waveguide device using a silicon substrate has a mask pattern formed by photolithography, and passive alignment is performed in a V-groove formed according to the mask pattern by etching, so that optical waveguides can be accurately connected to each other. Can do.

  This V-groove formation on the silicon substrate is an anisotropic process that can control the processing shape of silicon, which is the object of processing in a corrosive atmosphere in the gas phase or liquid phase, by utilizing the different etching rates for each crystal orientation. Formed by reactive etching.

  The V-groove formed by anisotropic etching on the silicon substrate can be formed at an angle determined by the crystal structure of silicon, and can be formed at a depth corresponding to the width by changing the etching width. The height position of the core in the optical fiber cable to be connected can be adjusted with accuracy by photolithography.

For example, Patent Document 1 discloses a technique for coupling an optical fiber cable and an optical waveguide with a V groove formed on a silicon substrate by this anisotropic etching.
JP 57-119314 A

  However, in the above-described prior art, when connecting a plurality of optical fiber cables side by side with a minimum pitch to a plurality of optical waveguides formed on a silicon substrate such as an optical splitter, the depth of the V groove becomes smaller than the set depth, There has been a problem that a positional shift occurs with respect to the height position of the optical waveguide core to be connected to the optical fiber cable, and the connection loss increases. This is a restriction caused by the shape of the V-groove formed by anisotropic etching. Specifically, the interval between the optical waveguide cores is the diameter of the optical fiber cable, and the optical fiber cables are in contact with each other at the outer periphery. It happened in some cases.

  The present invention has been made in view of the above-mentioned problems of the prior art, and connects an optical fiber cable guided by a groove formed in a substrate to the optical waveguide formed on the substrate by anisotropic etching. An object of the present invention is to provide an optical waveguide device capable of improving the degree of freedom in design without increasing connection loss.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a V-groove capable of fitting an end of an optical fiber cable is formed at an end of a substrate on which an optical waveguide composed of a core and a clad is formed. In this optical waveguide device, the V groove forming surface of the substrate is recessed by a predetermined depth from the position of the boundary surface between the cladding of the optical waveguide and the substrate to the back surface side of the substrate.

  According to a second aspect of the present invention, in the first aspect of the invention, the surface position of the V-groove forming surface is the light when the optical fiber cable is disposed in the core position of the optical waveguide and the V-groove. The fiber cable has a coaxial position with the core position of the fiber cable.

  According to a third aspect of the present invention, in the first aspect of the present invention, a plurality of the optical waveguides and V-grooves are formed in parallel, and the surface position of the V-groove forming surface is set to the V-groove. The core position of the optical fiber cable when the cable is disposed and the core position of the optical waveguide are coaxial with each other, and the clad outer peripheral surfaces of adjacent optical fiber cables are in contact with each other or close to each other. And

  According to the present invention, when an optical fiber cable guided by a groove formed in a substrate by anisotropic etching is connected to an optical waveguide formed on the substrate, design freedom can be achieved without increasing connection loss. The degree can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these embodiments. Further, the embodiment of the present invention shows the most preferable embodiment of the invention, and the terms and uses of the invention are not limited to this.

  FIG. 1 is a perspective view showing an external appearance of an optical waveguide device 1 according to the present invention. FIG. 2 is a perspective view showing an external appearance of an optical fiber cable 13 connected to the optical waveguide device 1, and FIG. FIG. 3B is a cross-sectional view taken along the line A-A, FIG. 3B is a cross-sectional view taken along the line B-B, and FIG. 4 is a schematic cross-sectional view illustrating a process of forming the V-groove forming regions 11a and 11b. FIG. 5 is a schematic cross-sectional view illustrating a process for forming the V-groove forming regions 11a and 11b, FIG. 6 is a schematic cross-sectional view illustrating a process for forming the optical waveguide 12, and FIG. 5 is a schematic cross-sectional view illustrating a process for forming the optical waveguide 12. FIG.

  As shown in FIGS. 1 and 2, the optical waveguide device 1 includes a V-groove formation region 11 a that fixes a plurality of optical fiber cables 13 by passive alignment on one end side (merging side) on the same plane of the substrate 10. A V-groove forming region 11b for fixing one optical fiber cable 13 to the other end side (branch side) and an optical waveguide for guiding and demultiplexing light between the V-groove forming region 11a and the V-groove forming region 11b. For example, the configuration includes an optical splitter 12.

  The substrate 10 is a plate-like substrate formed of single crystal silicon (Si), and fine shape processing is possible by performing dry or wet etching using a mask pattern formed on a plane by photolithography technology. It is a simple substrate. Further, the substrate 10 has a substrate surface SF1 having a plane orientation (100) as a processed surface (a surface in the Z1 direction in the illustrated example), so that the etching rate of the crystal plane (111) having a high atomic density is changed to another crystal plane. By utilizing the fact that it is slower than that, anisotropic etching using, for example, potassium hydroxide (KOH) or ethylenediamine pyrocatechol (EDP) is made possible.

  As shown in FIGS. 1, 2 and 3A, the V-groove formation regions 11a and 11b are planes in the Z1 direction on the substrate 10 and on the same substrate surface SF1 as the optical waveguide 12 formation surface on the substrate 10. A V-groove forming surface SF2 parallel to the substrate surfaces SF1 and SF3 is formed at a position recessed by a predetermined depth d in the substrate surface SF3 direction (Z2 direction) which is the back surface of the substrate surface SF1, and the V-groove forming surface In the SF2, a plurality of V grooves 111 are formed. The V-groove 111 is a groove formed with a known opening angle θ that depends on the crystal structure by using known anisotropic etching, and the depth can be adjusted according to the groove width set during the etching. Is possible.

  For this reason, in the optical waveguide device 1, the V-groove 111 is formed in the V-groove forming surface SF2 that is recessed by the predetermined depth d with respect to the substrate surface SF1, thereby limiting the design restrictions due to anisotropic etching of the V-groove 111. Can be eliminated by adjusting the predetermined depth d, and the core positions of the optical fiber cable 13 and the optical waveguide 12 can be formed coaxially. For example, as shown in FIG. 3A, the optical waveguide device 1 can perform passive alignment even when the outer peripheral surfaces of a plurality of optical fiber cables 13 are in contact with each other or close to each other.

  The optical waveguide 12 is made of a polymer resin material having optical transparency, and is composed of a core 121 and a clad 122 having different refractive indexes. Specifically, as shown in FIG. 3B, in the optical waveguide 12, a core 121 is formed on a lower clad layer 122a laminated with the substrate surface SF1 of the substrate 10 as a boundary surface, and the upper clad layer 122b is formed. It is laminated so as to cover the core 121. That is, the core 121 is embedded in the clad 122 by the lower clad layer 122a and the upper clad layer 122b. For this reason, the light is guided in the extending direction of the core 121 by totally reflecting the light inside the core 121. The core 121 has a Y-shaped portion, distributes light input from the V groove forming region 11b side, and outputs the light to the V groove forming region 11a side (reversely, from the V groove forming region 11a side). A configuration may be adopted in which input light is collected and output to the V-groove formation region 11b side).

  The optical fiber cable 13 is an optical fiber that is formed in a cylindrical shape by stretching a preform doped with germania (GeO2) or the like on quartz (SiO2) glass. A core 131 extends from the cylindrical center so as to be wrapped by a clad 132. The end portion of the optical fiber cable 13 is fixed by an adhesive member (not shown) in a state in contact with the wall surface of the V groove 111. For this reason, the optical waveguide between the optical fiber cable 13 and the core 121 is connected.

  The optical fiber cable 13 may be a multi-component glass, a plastic optical fiber (POF) cable, or the like, and has a cylindrical shape as described above, and is limited to a configuration in which a core is formed at the center position. Although not a thing, the said structure that the core position at the time of contacting and fixing to the wall surface of the V-groove 111 depends only on the outer diameter of a cylinder is preferable on a design.

  Next, a process of forming the V groove forming regions 11a and 11b on the substrate 10 will be described. First, as shown in FIG. 4A, a mask M1 is applied and formed on the processed surface (substrate surface SF1) of the substrate 10 described above. Next, as shown in FIG. 4B, the surface other than the portion covered with the mask M1 is subjected to dry etching or wet etching so as to be recessed in the direction of the substrate surface SF3 (back surface), and the mask M1 is removed. In addition, about this etching, the dry etching which can perform fine control of the formation position of the surface by an etching is preferable. Through the above-described steps, the V groove forming surface SF2 of the V groove forming regions 11a and 11b is recessed to a predetermined depth d corresponding to the etching with respect to the processed surface of the substrate 10 as shown in FIG. Can be formed.

  Next, as shown in FIG. 5A, a silicon nitride film M2 is vapor-deposited on the V-groove forming surface SF2 that is recessed to a predetermined depth d by the etching described above. Next, as shown in FIG. 5B, a photosensitive resin M3 is applied on the silicon nitride film M2 so as to remove the portion of the silicon nitride film M2 that becomes the V groove 111 by lithography. Next, as shown in FIG. 5C, the corresponding silicon nitride film M2 is removed using the photosensitive resin M3 as a mask, leaving the silicon nitride film M2 serving as a mask portion for forming the V-groove 111, leaving the photosensitive resin. Remove M3. Next, the groove width corresponding to the silicon nitride film M2 serving as a mask portion is formed by anisotropic wet etching in which the substrate in this state is immersed in a potassium hydroxide (KOH) solution set to a predetermined temperature and concentration for a predetermined time. The V-shaped groove 111 having an opening angle θ derived from the crystal structure is formed.

  Next, a process for forming the optical waveguide 12 will be described. First, as shown in FIG. 6A, a lower clad layer 122a is formed at a position on the substrate 10 where the optical waveguide 12 is to be formed with the substrate surface SF1 as a boundary surface. The lower cladding layer 122a is made of a transparent resin having optical transparency such as fluorinated polyimide. The lower clad layer 122a of fluorinated polyimide is formed, for example, by forming a layer of polyamic acid or the like on the substrate 10 by spin coating or the like and then imidizing it by heat treatment. Since this imidized coating film becomes insoluble in the solvent, it can be applied repeatedly. In addition to the fluorinated polyimide, the transparent resin having optical transparency may be an epoxy resin, a silicon resin, an acrylic resin (for example, polymethyl methacrylate: PMMA), or the like.

  Next, as shown in FIG. 6B, a core layer 121a having a refractive index higher than that of the lower cladding layer 122a is formed on the lower cladding layer 122a. The core layer 121a may be one in which the material of the lower cladding layer 122a described above is doped with another material to adjust the refractive index. However, in the case of fluorinated polyimide or the like, a material having a changed fluorination rate is used as the lower cladding layer 122a. Similarly, it is formed by a spin coat method or the like.

  Next, as shown in FIG. 6C, a mask M4 for forming a core pattern at the time of etching is formed by photolithography and patterned. As a material of the mask M4, a Si-containing resist, a deposited film such as a metal or glass, SOG (Spin On Glass), or the like can be used.

  Next, as shown in FIG. 7A, dry etching or wet etching is performed until the lower cladding layer 122a is exposed, and the remaining mask M4 is removed as shown in FIG. 7B.

  Next, as shown in FIG. 7C, an upper clad layer 122b is formed by spin coating or the like so as to cover the core 121. The upper clad layer 122b is component-adjusted so as to have the same refractive index as the lower clad layer 122a. For example, in the case of fluorinated polyimide, a polyamic acid layer is formed and then heat-treated to imidize the polyamic acid. Thus, the optical waveguide 12 in which the core 121 is embedded by the lower clad layer 122a and the upper clad layer 122b is formed.

  As described above, the optical waveguide device 1 includes the V-groove 111 for passive alignment with the optical fiber cable 13 at the end of the substrate 10 on which the optical waveguide 12 is formed, and the surface of the substrate surface SF1 on which the optical waveguide 12 is formed. In this configuration, the groove is formed on the V-groove forming surface SF2 which is recessed by a predetermined depth d from the position.

  Therefore, the optical waveguide device 1 can improve the degree of design freedom without increasing the connection loss even when the V-groove 111 is formed by anisotropic etching or the like.

  Note that the description in the present embodiment shows an example of the present invention, and the present invention is not limited to this. The detailed configuration of the optical waveguide device 1 in the present invention can be appropriately changed without departing from the spirit of the present invention.

  For example, in the present embodiment, an optical splitter that distributes light input from one optical fiber cable 13 and outputs the light to a plurality of optical fiber cables 13 is exemplified. However, for example, a plurality of optical fiber cables 13 having different diameters are used. It may be an optical connector that connects them in parallel.

  The formation of the optical waveguide 12 may be a direct exposure method or a photo bleaching method (refractive index change method), and is not particularly limited to the method described above. Further, the optical waveguide 12 may be a ridge type or a slab type other than the embedded type exemplified in the above-described embodiment.

It is a perspective view which shows the external appearance of the optical waveguide device 1 which is this invention. 1 is a perspective view showing an external appearance of an optical fiber cable 13 connected to an optical waveguide device 1. FIG. (A) is sectional drawing which shows the cross section of AA of FIG. 2, (b) is sectional drawing which shows the cross section of BB of FIG. It is the cross-sectional schematic explaining the formation process of V groove formation area | region 11a, 11b. It is the cross-sectional schematic explaining the formation process of V groove formation area | region 11a, 11b. 5 is a schematic cross-sectional view illustrating a process for forming the optical waveguide 12. FIG. 5 is a schematic cross-sectional view illustrating a process for forming the optical waveguide 12. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical waveguide device 10 Substrate 11a, 11b V-groove formation area 12 Optical waveguide 13 Optical fiber cable 111 V-groove 121, 131 Core 121a Core layer 122, 132 Clad 122a Lower clad layer 122b Upper clad layer d Predetermined depth M1, M4 Mask M2 Silicon nitride film M3 Photosensitive resin SF1 Substrate surface SF2 V-groove forming surface SF3 Substrate surface θ Open angle

Claims (3)

In an optical waveguide device in which a V-groove into which an end of an optical fiber cable can be fitted is formed at an end of a substrate on which an optical waveguide composed of a core and a clad is formed.
An optical waveguide device, wherein a V-groove forming surface of the substrate is formed in a concave portion having a predetermined depth on the back surface side of the substrate from the position of the boundary surface between the cladding and the substrate of the optical waveguide.   The surface position of the V groove forming surface is a position where the core position of the optical waveguide and the core position of the optical fiber cable when the optical fiber cable is disposed in the V groove are coaxial. The optical waveguide device according to claim 1. The optical waveguide and the V groove are formed in parallel,
The surface position of the V-groove forming surface is such that when the optical cable is disposed in the V-groove, the core position of the optical fiber cable and the core position of the optical waveguide are coaxial with each other and the outer periphery of the cladding of the adjacent optical fiber cable The optical waveguide device according to claim 1, wherein the surfaces are in contact with each other or in close proximity to each other.

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