JP7799206B2 - Optical waveguide device manufacturing method and optical waveguide device - Google Patents

Description

The present invention relates to a method for manufacturing an optical waveguide device and an optical waveguide device, and more particularly to a technique for connecting an optical fiber to an optical waveguide substrate.

The technology for connecting optical fibers to such optical waveguides involves first dicing the optical waveguide substrate vertically and horizontally to divide it into chips of several millimeters square, and then optically polishing the input and output sections of the optical waveguide using an abrasive such as selenium oxide. Then, multiple optical fibers for inputting and outputting optical signals are connected to the optical waveguide substrate.

When connecting multiple optical fibers, a substrate is prepared with multiple V-grooves whose spacing is adjusted to match the spacing of the optical waveguides to be connected. The optical fibers are then aligned and placed in the corresponding V-grooves (see Non-Patent Document 1). The optical fibers are then pressed toward the substrate with a glass plate so that the optical fibers are in close contact with the slope of the V-groove. In this process, the connection end faces of the optical fiber bundle (optical fiber array) are optically polished in the same way as the substrate side of the optical waveguides.

NTT Advanced Technology, "Adhesive for Fiber Array Assembly," [online], April 27, 2021, 1/4-4/4, [Retrieved June 29, 2021] Internet (URL: https://keytech.ntt-at.co.jp/adhesive/prd_10012.html)

In the above-mentioned technology for connecting an optical fiber to a waveguide substrate, the optical polishing process for the substrate and optical fiber member is carried out through a rough polishing process using an abrasive containing coarse abrasive grains, a medium polishing process, and a finish polishing process using fine silica particles, which takes a relatively long time. Furthermore, the polishing process requires special jigs and tools to control the polishing angle of the end face. Furthermore, for highly integrated substrates with electrode patterns formed on their surfaces, such as silicon photonics chips, special processing steps such as providing a cover to protect the surface from contamination that occurs during the polishing process are required.

In the process of connecting the optical waveguide substrate and the optical fiber array, the optical waveguide substrate or the optical fiber array is fixed to a fine-adjustment stage with a resolution of 0.1 μm or less, and a separately prepared light source and optical power monitor are connected to the optical fiber and aligned by active alignment to maximize the optical power. After that, an ultraviolet (UV) curing adhesive is dropped onto the connecting end face and cured to fix the connection.

As described above, there is a problem in that connecting an optical fiber array to an optical waveguide substrate and ensuring a certain level of optical input/output function requires a great deal of time and cost for processes such as optical polishing and alignment of each component.

An object of the present invention is to provide a method for manufacturing a fiber array that can omit the polishing step and alignment step when connecting an optical waveguide substrate and an optical fiber.

In order to achieve this object, one aspect of the method for manufacturing an optical waveguide device of the present invention includes the steps of passing a plurality of optical fibers through a plurality of through holes formed in a fixing block, the through holes having a diameter larger than the diameter of the optical fibers, placing the tip portions of the plurality of optical fibers exposed from the fixing block in a plurality of recesses of a temporary fixing substrate, respectively, and fixing the plurality of optical fibers to the temporary fixing substrate and the fixing block while pressing the plurality of optical fibers against the recesses with a temporary holding plate, dicing the temporary fixing substrate and the temporary holding plate together with the plurality of optical fibers to set the tip portions of the plurality of optical fibers to a predetermined length, removing the temporary fixing substrate and the temporary holding plate from the tip portions of the plurality of optical fibers, and arranging and fixing the tip portions of each of the plurality of optical fibers fixed to the fixing block while aligning them with a plurality of recesses of a waveguide substrate on which optical waveguides are formed , wherein the spacing between the plurality of recesses of the temporary fixing substrate and the spacing between the plurality of recesses of the waveguide substrate are equal, and the plurality of recesses of the waveguide substrate are formed to match the positions of the optical waveguides .

It is possible to omit the polishing process and active alignment for both the optical waveguide substrate (chip) and the fiber array, and the fiber array can be made smaller, resulting in the effect of reducing the manufacturing time and manufacturing costs.

1 shows a diagram of an implementation of a fiber array according to an embodiment of the present invention. 1A to 1C are diagrams showing a process for producing a fiber array according to an embodiment of the present invention. 1A to 1C are diagrams showing a process for producing a fiber array according to an embodiment of the present invention. 1 shows a diagram of an implementation of a fiber array according to an embodiment of the present invention. FIG. 10 is a diagram showing a fiber array of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In this embodiment, a recess (in this specification, a recess having a roughly V-shaped cross section is referred to as a V-groove) is formed on a Si substrate on which a silicon photonics optical waveguide has been formed, by photolithography and etching processes, in alignment with the position of the optical waveguide. The cross section of the recess may be roughly U-shaped, or it may simply be a recess. The depth of the V-groove is determined in accordance with the height of the waveguide. In other words, the depth of the V-groove is determined so that when an optical fiber is placed and fixed in the V-groove, the center of the optical fiber core will be aligned with the height of the optical waveguide.

FIG. 1 shows a diagram in which a fiber array is mounted in a plurality of V-grooves formed in accordance with the position (height) of the optical waveguide in the optical signal input/output section of a substrate on which a silicon photonics optical waveguide is formed, as described above.

As shown in Fig. 1, a plurality of V-grooves 103 are formed in a substrate 101 on which silicon photonics waveguides are formed (hereinafter also referred to simply as an optical waveguide substrate). In this embodiment, the number of these V-grooves 103 corresponds to the number of optical fibers that make up an optical fiber array 102. Meanwhile, the optical fiber array 102 is fixed to a glass block 104. The block 104, which holds a portion of the optical fiber array 102 in this manner, is connected to the substrate 101 while aligning each optical fiber 102a of the optical fiber array 102 with the corresponding V-groove 103.

Then, an ultraviolet (UV) curing adhesive is filled into the interface between the optical waveguide substrate 101 and the block 104 , thereby fixing the optical fiber array 102 to the optical waveguide substrate 101 .

When connecting the optical waveguide substrate 101 and the optical fiber array 102 described above, the corresponding optical fibers 102a are placed in the V-grooves 103 and pressed tightly against the optical waveguides, and then glued and fixed. This ensures reliable optical coupling between the optical fibers and the waveguides and ensures adhesive strength. Note that even if adhesive leaks into the V-grooves 103 of the optical waveguide substrate 101, it does not pose a problem because it contributes to fixing the optical fiber array 102.

2(a) to 2(c) and 3(a) and 3(b) are diagrams for explaining the method of fabricating a fiber array in order.

2(a), the optical fiber array 102 is first passed through a fixing glass block 104. More specifically, through-holes several tens of μm larger in diameter than the individual optical fibers 102a are formed in the block 104. The optical fibers 102a, whose coating has been removed and cleaved, are then passed through these through-holes.

Next, as shown in FIG. 2B, a substrate 105 is prepared in which V-grooves 105a are formed in the same number as the optical fibers. The optical fibers 102a are aligned with the V-grooves 105a while the block 104 is moved relative to the substrate 105. At this time, the optical fiber array 102 and the block 104 are not fixed to each other. In manufacturing the optical fiber array 102, as described above, a V-groove substrate 105 is prepared separately from the V-grooves 103 of the optical waveguide substrate 101 to which it will ultimately be connected. The V-grooves of this substrate 105 are formed to have the same arrangement pitch (spacing) and depth as the multiple V-grooves 103 of the optical waveguide substrate 101. The block 104 used in this embodiment may be a split-type block. In this case, the block 104 is split into two parts, one above the other, and the optical fibers 102a are aligned, and then the block 104 is placed on the V-groove substrate 105.

Next, as shown in Figure 2(c), with the optical fibers 102a and the V-groove aligned, the optical fiber array 102 is temporarily held down on the V-groove substrate 105 by a glass temporary holding plate 106. Then, in this state, each optical fiber 102a is adhesively fixed into the corresponding V-groove. After temporary holding with the temporary holding plate 106, the through holes in the block 104 are filled with a UV-curable adhesive, and the optical fiber array 102 is fixed to the block 104 by irradiating it with UV. In addition, a reinforcing resin 107 is piled up around the base of the coated side of the optical fiber array 102 for protection.

Next, as shown in Fig. 3(a), the V-groove substrate 105 is cut using a dicing device 108. More specifically, the substrate is diced together with a temporary fixing presser plate 106, and an optical fiber array 102 having oblique end faces at a predetermined angle is obtained, as will be described in detail later with reference to Fig. 4.

As described above, the optical fiber array 102 is fixed in the V-groove of the V-groove substrate 105, and
By performing dicing while the wafer is temporarily fixed with the presser plate 106, the accuracy of the cut surface can be increased, and a cut surface similar to the polished surface can be obtained. As a result, it is possible to omit the optical polishing process, which requires a relatively large number of steps.

Next, the optical fiber array 102 is pulled out together with the block 104 from the V-grooved substrate 105 for temporary fixing, and the optical fiber array is completed as shown in FIG. 3(b).

FIG. 4 is a diagram illustrating the connection relationship between the optical waveguide substrate and the optical fiber array according to this embodiment. As shown in the figure, in this embodiment, the optical fiber is connected to the optical waveguide at an angle θ from the perpendicular direction of the connection surface. In this embodiment, θ is a few degrees (approximately 8 to 10°). This makes it possible to prevent reflection at the connection surface when optically coupled. In this embodiment, this angle is achieved by the dicing cut described above. The position at which the optical fiber array 102 is cut is determined according to the length of the V-groove formed in the optical waveguide substrate 101.

The optical fiber array 102 fixed to the completed block 104 is connected to the optical waveguide substrate 101 to manufacture an optical waveguide device. More specifically, the optical fiber array 102 fixed to the block 104 is spaced at equal intervals with the V-grooves 103 of the optical waveguide substrate 101 via the V-grooves of the V-groove substrate 105, and in this state is placed in the V-groove 103 of the optical waveguide substrate 101, as shown in FIG. 1. This allows the completed optical fiber array 102 to be connected to the optical waveguide substrate 101 with its cores aligned. As a result, it is possible to omit the alignment of the V-grooves 103 of the optical waveguide substrate 101 with the corresponding optical fibers.

The polishing process and active alignment can be omitted for both the optical waveguide substrate (chip) 101 and the fiber array, and the fiber array can be made smaller, resulting in the effect of reducing the manufacturing time and manufacturing costs.

Although this optical waveguide device employs multiple optical fibers, the present invention is not limited to this configuration. In the case of a single-function device using an optical waveguide, for example, a single-core device such as an optical modulator may also be used.

(Comparative Example)
5(a) and 5(b) are diagrams illustrating the connection of an optical fiber array according to a comparative example. As shown in these figures, each optical fiber 202a of the optical fiber array is placed in a V-groove of a V-groove substrate 205 and fixed with adhesive 209 for fixing the fiber to the V-groove. The root portion of the fiber is fixed with adhesive 210.

The optical fiber 202a fixed to the V-groove substrate 205 in this manner is then connected to a waveguide (not shown) formed on a substrate (not shown). In this connection, the optical fiber 202a is simply fixed in the V-groove of the V-groove substrate 205, and the V-groove of the V-groove substrate 205 is not aligned with the waveguide, so alignment is required. Furthermore, because the above-mentioned dicing is not performed, an optical polishing process is required for the optical fiber.

Claims (3)

Passing a plurality of the optical fibers through a plurality of through holes formed in a fixing block and having a diameter larger than the diameter of the optical fibers;
the tip portions of the optical fibers exposed from the fixing block are respectively placed in the recesses of a temporary fixing substrate, and the optical fibers are fixed to the temporary fixing substrate and the fixing block while pressing the optical fibers against the recesses with a temporary holding plate;
the temporary fixing substrate and the temporary holding plate are diced together with the plurality of optical fibers to cut the tip portions of the plurality of optical fibers to a predetermined length;
removing the temporary fixing substrate and the temporary holding plate from the tip portions of the plurality of optical fibers;
the tip portions of the optical fibers fixed to the fixing block are aligned with and fixed to a plurality of recesses of a waveguide substrate on which optical waveguides are formed;
The method comprises the steps of:
a plurality of recesses of the temporary fixing substrate and a plurality of recesses of the waveguide substrate are spaced apart by the same distance, and the plurality of recesses of the waveguide substrate are formed to match the positions of the optical waveguides. a distance between the recesses in the temporary fixing substrate being equal to a distance between the optical waveguides connected to the optical fibers;
The method for manufacturing the optical waveguide device according to claim 1 . The depth of the recess of the temporary fixing substrate is adjusted so that the center of the core of the optical fiber is aligned with the height of the optical waveguide.
3. The method for manufacturing the optical waveguide device according to claim 1.