WO2022130454A1 - Metal layer for protecting vicinity of light input/output portion of optical waveguide - Google Patents

Abstract

The present disclosure provides a technology for protecting the vicinity of an optical input/output portion of an optical waveguide formed in the vicinity of a surface of an optical waveguide substrate. The optical input/output portion of the optical waveguide is on an end surface of the optical waveguide substrate, and a metal layer is provided to the optical waveguide on the surface of the optical waveguide substrate and adjacent to the end surface of the optical waveguide substrate. The metal layer includes a protective pattern, and the protective pattern is formed on the optical waveguide and follows the optical waveguide. The width of the protective pattern is greater than the width of the optical waveguide , and the material of the metal layer is the same as the material of an electric wiring layer formed on the surface of the optical waveguide substrate.

Description

Metal layer to protect the vicinity of the optical input / output part of the optical waveguide

The present disclosure relates to a technique for protecting the vicinity of an optical input / output portion of an optical waveguide formed in the vicinity of the surface of an optical waveguide substrate.

Conventionally, in the optical waveguide structure using silicon photonics technology, a SiO ₂ layer and a Si layer are sequentially deposited on a Si substrate, and the Si layer is etched into a desired pattern by photolithography to form a waveguide, and further. It is formed by covering a pattern formed by depositing _two layers of SiO. On the surface of the substrate, electrical wiring for driving a photodiode and the like and a pad for fixing the substrate are provided by a metal layer containing Au as a main component.

An optical waveguide substrate for inputting and outputting optical signals to an optical waveguide substrate (hereinafter, also referred to as a silicon photonics optical waveguide substrate) having a silicon waveguide (thin wire waveguide) formed by using silicon photonics, which is a fine processing technology. It is necessary to optically polish the end face of the optical fiber and connect one or more optical fibers (see, for example, Patent Document 1).

Generally, the optical polishing step is usually carried out through a rough polishing step using coarse abrasive grains, a polishing step using medium abrasive grains, and a finish polishing step using fine silica particles.

Japanese Unexamined Patent Publication No. 09-090161

Since the layer above the Si layer on which the optical waveguide is formed in the silicon photonics optical waveguide substrate is very thin, about several μm, there is a problem if chipping that occurs during the optical polishing process causes chips or cracks in the upper layer. There is. If this chip hangs on the optical waveguide, a large optical connection loss will be caused when the optical fiber is connected.

In addition, it is important to control the amount of polishing in the optical polishing process. If the amount of polishing is excessive or insufficient, the structure of the optical waveguide near the optical fiber connection portion and the mode shape of the light change, so that the optical connection loss with the optical fiber increases.

When connecting a plurality of optical fibers, a lid formed by arranging the optical fibers on a glass substrate (hereinafter referred to as V-groove substrate) that has been subjected to V-groove processing with high precision and arranging the optical fibers directly above the optical fibers. An optical fiber array having a structure in which the optical fiber is pressed so as to be in close contact with the slope of the V-groove is used. As described above, since the layer above the Si layer on which the optical waveguide of the silicon photonics optical waveguide is formed is very thin, the thickness of the glass substrate for holding the optical fiber array when the optical fiber array is connected is very thin. The connection structure is asymmetric with respect to the thickness direction of the Si substrate. Generally, an ultraviolet curable adhesive is used when connecting such an optical fiber array, but in the above-mentioned asymmetric structure, the ultraviolet curable adhesive accumulates in a slope shape on the stepped portion, and when irradiated with ultraviolet light, the ultraviolet curable adhesive is cured and shrunk. The optical fiber array is tilted in the direction perpendicular to the optical waveguide substrate, and optical loss occurs due to the angular deviation of the fiber.

The present disclosure has been made in view of such a problem, and an object thereof is to provide a technique for protecting the vicinity of an optical input / output portion of an optical waveguide formed near the surface of an optical waveguide substrate. To do.

In order to achieve such an object, one embodiment of the present invention is a metal layer for protecting the vicinity of the optical input / output portion of the optical waveguide formed near the surface of the optical waveguide substrate. The optical input / output portion of the optical waveguide is on the end surface of the optical waveguide substrate, and the metal layer is provided on the optical waveguide on the surface of the optical waveguide substrate and adjacent to the end surface of the optical waveguide substrate. The metal layer includes a protective pattern, which is formed on the optical waveguide along the optical waveguide. The width of the protection pattern is larger than the width of the optical waveguide, and the material of the metal layer is the same as the material of the electric wiring layer formed on the surface of the optical waveguide substrate.

According to one embodiment of the present invention, it is possible to protect the vicinity of the optical input / output portion of the optical waveguide formed near the surface of the optical waveguide substrate.

It is a figure which shows the connection between a silicon photonics optical waveguide board and an optical fiber array. It is a figure which shows the connection of the silicon photonics optical waveguide substrate which has the protective metal layer which concerns on one Embodiment of this invention, and an optical fiber array. It is a figure which shows the structure of the protective metal layer which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of a technique for protecting the vicinity of the optical input / output portion of the optical waveguide formed near the surface of the optical waveguide substrate will be described with reference to the drawings. The same or similar reference numerals indicate the same or similar elements, and the repeated description may be omitted. In the following description, the above-mentioned silicon photonics optical waveguide board will be exemplified as the optical waveguide board, and the above-mentioned optical fiber array will be exemplified as the connection target with the optical waveguide board. First, the structure of the connection portion between the conventional optical waveguide substrate and the optical fiber array will be described, and then the structure of the connection portion between the optical waveguide substrate having a metal layer and the optical fiber array according to the embodiment of the present invention will be described. do.

FIG. 1 shows the structure of a connection portion between a conventional silicon photonics optical waveguide substrate 100 and an optical fiber array 110. The optical waveguide substrate 100 covers the SiO _{2 layer 102 laminated on the Si substrate 101, the optical waveguide 104 formed by processing the Si layer 103 laminated on the SiO 2 layer} 102, and the optical waveguide 104. It is provided with SiO ₂ (not shown) deposited in. Further, the optical waveguide substrate 100 is provided with electrical wiring and a pad for fixing the substrate (not shown) on the surface (for example, a position above the optical waveguide 104). On the other hand, the optical fiber array 110 includes a V-groove substrate 111 in which a V-groove is formed, an optical fiber 112, and a lid 113. A part of the optical fiber 112 is pressed and fixed by the lid 113 so as to be in close contact with the slope of the V groove of the V groove substrate 111. The connection portion between the connection end surface of the optical waveguide substrate 100 and the connection end surface of the optical fiber array 110 is bonded and fixed by an ultraviolet curing adhesive 120 for connection after aligning the optical waveguide 104 and the optical fiber 112. The fixing of the V-groove substrate 111, the optical fiber 112, and the lid 113 can be reinforced by the reinforcing resin 121.

For example, in the configuration shown in FIG. 1, the light propagating through the three optical fibers 112 is coupled to each of the three optical waveguides 104 at the connection portion. In the example shown in FIG. 1, the light propagating in the central optical fiber of the three optical fibers 112 is coupled to the central optical waveguide 104 of the three optical waveguides 104 and then two according to the optical waveguide pattern. It branches to the optical waveguide 104 and propagates.

The connection end face of the optical waveguide substrate 100 including the end face of the optical waveguide 104 is optically polished before being adhesively fixed to the connection end face of the optical fiber array 110. Since the layer above the Si layer 103 on which the optical waveguide 104 is formed is very thin, chipping in the optical polishing step causes chips and cracks in the vicinity of the optical waveguide 104, which causes connection loss.

Further, in the vicinity of the end face of the optical waveguide 104, the metal layer of the electric wiring and the pad for fixing the substrate is not provided in the upper layer of the optical waveguide 104. Since the upper layer of the optical waveguide 104 is very thin, the pattern of the optical waveguide 104 can be confirmed from the surface of the optical waveguide substrate 100. On the other hand, the V-groove is formed on the surface of the V-groove substrate 111. In a state where the optical waveguide 104 and the optical fiber 112 are aligned (aligned) by abutting the connection end surface of the optical waveguide substrate 100 and the connection end surface of the optical fiber array 110, the position of the surface of the optical waveguide substrate 100 And the position of the surface of the optical fiber array 110, a step corresponding to the thickness of the lid 113 is generated. That is, the connection portion between the optical waveguide board 100 and the optical fiber array 110 is stepped.

As shown in FIG. 1, a surplus of the UV-curing adhesive 120 for connection is accumulated in a slope shape on a step portion generated at a connection portion between the optical waveguide substrate 100 and the optical fiber array 110 to form a fillet. At the time of irradiation with ultraviolet rays, the optical fiber array 110 is tilted in a direction perpendicular to the optical waveguide substrate 100 due to the curing shrinkage of the excess of the ultraviolet curing adhesive 120 for connection (or the normal of the connection end face of the optical fiber array 110 is the optical waveguide. (Inclined from the normal of the substrate 100), optical loss occurs due to the angular deviation of the optical axis at the connection portion.

FIG. 2 shows the structure of the connection portion between the optical waveguide substrate 100 having the protective metal layer 200 and the optical fiber array 110 according to the embodiment of the present invention. The protective metal layer 200 is provided in the vicinity of the end face of the optical waveguide 104 on the surface layer of the optical waveguide substrate 100, and includes a protection pattern 300. The protective metal layer 200 is, for example, a metal layer on a SiO ₂ layer (not shown) deposited so as to cover the optical waveguide 104, and can be formed by using a metal material such as Au. By using the same metal material as the electric wiring layer (not shown) formed on the surface of the optical waveguide substrate 100 for the protective metal layer 200, the electric wiring layer and the protective metal layer 200 can be efficiently combined in one process. Can be made.

FIG. 3 illustrates the configuration of the protective metal layer 200 according to the embodiment of the present invention. The protection pattern 300 is formed directly above each optical waveguide 104 along the optical waveguide 104, and is the width of the optical waveguide 104 (the length in the direction parallel to the main surface of the optical waveguide substrate 100 and orthogonal to the light propagation direction). ), And has a length of about several mm (length from the connection end) in the same direction as the optical waveguide 104. The length of the protective metal layer 200 in the lateral direction may be the same as or different from the length of the protection pattern 300.

The protective pattern 300 included in the protective metal layer 200 is manufactured by using a metal process such as wiring in silicon photonics technology. By making the width of the protection pattern 300 larger than the mode diameter in the plane direction of the light propagating through the optical waveguide 104, chips and cracks generated in the polishing process reach the mode of light propagating through the optical waveguide 104. You can prevent that.

Further, the protective metal layer 200 may include ladder-shaped patterns 301 arranged on both sides of the protective pattern 300. The ladder-shaped pattern 301 is formed along the optical waveguide 104 and serves as a scale when monitoring the polishing amount in the polishing process, and the protection pattern 300 on the optical waveguide 104 is defective in a manufacturing process such as a surface cleaning process. It has the effect of preventing it from happening.

Further, the protective metal layer 200 may include guide patterns 302 arranged on both sides of the ladder-shaped pattern 301. The guide pattern 302 may be arranged so as to continue from the ladder-shaped pattern 301 to the chip end face (that is, the end face of the optical waveguide substrate 100). The guide pattern 302 may be arranged so as to be symmetrical with respect to the ladder-shaped pattern 301. FIG. 3 shows, as an example, a case where the guide pattern 302 has an arc shape. As shown in FIG. 2, in the guide pattern 302, the surplus of the UV curable adhesive 120 for connection used when connecting the optical fiber array 110 and the optical waveguide substrate 100 is applied to the end face side from the surface of the optical waveguide substrate 100. Guide to. The guide pattern 302 prevents the surplus of the UV-curing adhesive 120 for connection from remaining on the stepped portion at the joint between the surface of the optical waveguide substrate 100 and the optical fiber array 110 to form a fillet, and UV-curing for connection. It has the effect of suppressing the angular deviation of the fiber due to the curing shrinkage of the adhesive 120.

Furthermore, since the protective metal layer 200 is a metal film having good visibility, an image recognition marker 303 may be arranged. By using the image recognition marker 303 and the image recognition technique, the connection between the optical waveguide substrate 100 and the optical fiber array 110 can be facilitated particularly with respect to the plane direction of the optical waveguide substrate 100.
The connection between the silicon photonics optical waveguide board and the optical fiber array has been described above as an example. However, the optical waveguide substrate is not limited to the silicon photonics optical waveguide substrate, and the present invention can be carried out by using other types of optical waveguide substrates as long as the gist of the present invention is not deviated. Further, the connection target with the optical waveguide board is not limited to the optical fiber array, and an optical waveguide board having various functions may be used.

As described above, according to the present disclosure, it is possible to protect the vicinity of the connection portion of the optical waveguide board.

Claims (6)

1. A metal layer for protecting the vicinity of the optical input / output portion of the optical waveguide formed near the surface of the optical waveguide substrate.
   The optical input / output portion of the optical waveguide is on the end face of the optical waveguide substrate.
   The metal layer is provided on the optical waveguide on the surface of the optical waveguide substrate and adjacent to the end surface of the optical waveguide substrate.
   The metal layer contains a protective pattern and
   The protection pattern is formed on the optical waveguide along the optical waveguide.
   The width of the protection pattern is larger than the width of the optical waveguide,
   The material of the metal layer is the same as the material of the electric wiring layer formed on the surface of the optical waveguide substrate.
2. The metal layer according to claim 1, wherein the width of the protection pattern is larger than the mode diameter of the light propagating through the optical waveguide in the plane direction of the optical waveguide substrate.
3. The metal layer according to claim 1, further comprising a ladder-like pattern formed along the optical waveguide arranged on both sides of the protection pattern.
4. The metal layer according to claim 3, further comprising a guide pattern arranged so as to continue from the ladder-shaped pattern to the end face of the optical waveguide substrate.
5. The metal layer according to claim 1, further comprising an image recognition marker.
6. The metal layer according to claim 1, wherein the optical waveguide substrate includes a SiO ₂ layer _{, a} Si layer, and a SiO ₂ layer sequentially deposited on the Si substrate, and the optical waveguide is formed on the Si layer.

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