JP2005017761A - Optical waveguide and method for manufacturing optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide which is exactly controlled in the position of a core in relation to a rod of a clad and a method for manufacturing the optical waveguide. <P>SOLUTION: A wafer of the optical waveguide includes the core 212 and the clad 218 having a level difference positioned in relation to the core 212 and has a mark 206 for recognizing the position of the core. Also, the method for manufacturing the optical waveguide includes a step of forming the core 212 on the lower clad 202, a step of covering substantially the entire surface of the core 212 with the upper clad 203, a step of providing the wafer with the mark 206 for recognizing the position of the core 212 and a step of providing the upper clad 203 or both of the upper clad 203 and the lower clad 202 or both the clads and the substrate 201 with level differences. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical waveguide and a method for manufacturing the optical waveguide.
[0002]
[Prior art]
In recent years, optical communication has been widely used in order to achieve high-speed and large-capacity information transmission. In optical communications, it is necessary to extract light of the target wavelength or combine light of different wavelengths, so an optical filter with wavelength selectivity is appropriately inserted in a predetermined part of the optical waveguide. Is done.
[0003]
6A and 6B are diagrams showing a ferrule that connects an optical fiber, which is a kind of optical waveguide, wherein FIG. 6A is a schematic perspective view, and FIG. 6B is a cross-sectional view taken along line DD shown in FIG. . As shown in FIGS. 6A and 6B, the ferrule 10 is used to connect two optical fibers 11 and 12, and a groove 10a is provided in the connecting portion. The optical fiber 11 includes a fiber 11c including a core 11a and a cladding 11b covering the core 11a, and a fiber coating 11d covering the same. Similarly, the optical fiber 12 includes a core 12a and a cladding 12b covering the core 12a. It consists of a strand 12c and a fiber coating 12d covering it. The optical fibers 11 and 12 are in a state in which the fiber coatings 11d and 12d are removed inside the ferrule 10 to expose the fiber strands 11c and 12c, respectively, and the fiber strand 11c is formed on one side wall portion of the groove 10a. The fiber strand 12c terminates at the other side wall portion of the groove 10a. That is, the end surface of the fiber strand 11 c and the end surface of the fiber strand 12 c are in a state of being opposed to each other through the groove 10 a provided in the ferrule 10.
[0004]
7 is a view showing a state in which an optical filter is mounted on the ferrule 10 shown in FIG. 6, wherein (a) is a schematic perspective view, and (b) is a cross-sectional view taken along line EE shown in (a). is there. As shown in FIGS. 7A and 7B, when the optical filter 30 is inserted into the groove 10 a provided in the ferrule 10, the light propagated from one of the optical fibers 11 and 12 depends on the characteristics of the optical filter 30. And is propagated to the other of the optical fibers 11 and 12. Thereby, it is possible to extract light having a target wavelength.
[0005]
8A and 8B are diagrams showing a waveguide-embedded optical circuit that is a kind of optical waveguide, in which FIG. 8A is a schematic perspective view, and FIG. 8B is a cross-sectional view taken along line FF shown in FIG. . As shown in FIGS. 8A and 8B, the waveguide-embedded optical circuit 20 includes a substrate 21, a clad 22 provided on the substrate 21, and a core 23 provided inside the clad 22. The clad 22 and the core 23 are divided by a groove 24 into a portion composed of the clad 22a and the core 23a and a portion composed of the clad 22b and the core 23b. Therefore, the core 23 a terminates at one side wall portion of the groove 24, and the core 23 b terminates at the other side wall portion of the groove 24. In other words, the end surface of the core 23 a and the end surface of the core 23 b are opposed to each other through the groove 24.
[0006]
9A and 9B are diagrams showing a state in which an optical filter is inserted into the waveguide-embedded optical circuit 20 shown in FIG. 8, where FIG. 9A is a schematic perspective view, and FIG. 9B is a GG line shown in FIG. FIG. As shown in FIGS. 20A and 20B, when the optical filter 30 is inserted into the groove 24 provided in the cladding 22, the light propagated from one of the cores 23 a and 23 b depends on the characteristics of the optical filter 30. Filtered and propagates to the other of the cores 23a, 23b. Thereby, it is possible to extract light having a target wavelength.
[0007]
When light propagates through the divided optical waveguide, a loss mainly caused by a diffraction phenomenon occurs in the divided portion. FIG. 10 is a diagram for explaining this, and shows how the light 40 propagates through the gap from the optical waveguide 41 composed of the core 41a and the clad 41b to the optical waveguide 42 composed of the core 42a and the clad 42b. This is schematically shown separately for a small case (a) and a large core diameter (b). As shown in FIGS. 10A and 10B, since the light emitted from the optical waveguide 41 spreads due to the diffraction phenomenon, the diffraction loss increases as the gap width d increases. On the other hand, as is clear from the comparison between FIG. 10A and FIG. 10B, the diffraction phenomenon becomes more conspicuous as the beam spot diameter becomes smaller. What is necessary is just to make a beam spot diameter large while narrowing.
[0008]
For this reason, when two optical fibers are connected using a ferrule, if spot size conversion is performed by using a TEC (Thermal Expanded Core) fiber whose core diameter is locally expanded at the terminal end, it is caused by a diffraction phenomenon. Loss can be reduced. The expansion of the core in the TEC fiber is performed by heating with a micro burner or a heater, as is well known (Japanese Patent No. 2693649).
[0009]
[Patent Literature]
Japanese Patent No. 2669649
[0010]
[Problems to be solved by the invention]
However, the waveguide-embedded optical circuit as shown in FIGS. 8 and 9 has a very large heat capacity compared to the optical fiber, so that the core diameter is locally expanded by heating as in the TEC fiber. It is difficult. For this reason, this type of optical waveguide has a problem that a loss due to a diffraction phenomenon is large in a groove portion in which the optical filter is inserted.
[0011]
In order to solve this problem, the present inventors have proposed a novel spot size conversion element and a waveguide embedded optical circuit using the same in Japanese Patent Application No. 2002-295334.
[0012]
FIG. 11A is a schematic perspective view of a waveguide-embedded optical circuit 100, which is an embodiment of the waveguide-embedded optical circuit, viewed from one direction, and FIG. 11B is a waveguide-embedded optical circuit. It is the schematic perspective view which looked at the optical circuit 100 from the reverse direction.
[0013]
As shown in FIG. 11, the waveguide-embedded optical circuit 100 of this embodiment includes a substrate 101, lower claddings 102-1 to 102-6, upper claddings 103-1 to 103-6, and a core 104-. 1 and 104-2 and optical resin layers 105-1 and 105-2 (these may be collectively referred to as the optical resin layer 105). The lower clad 102-1 to 102-3, the upper clad 103-1 to 103-3, the core 104-1, and the optical resin layer 105-1, the lower clad 102-4 to 102-6, the upper clad 103- The portion consisting of 4 to 103-6, the core 104-2, and the optical resin layer 105-2 is divided by a groove 106. That is, the groove 106 reaches the substrate 101, and the substrate 101 is exposed.
[0014]
The refractive indexes of the cores 104-1 and 104-2 are slightly larger than those of the lower claddings 102-1 to 102-6 and the upper claddings 103-1 to 103-6, and the lower claddings 102-1 to 102-6 and the upper claddings 102-1 to 102-6 The refractive indexes of the claddings 103-1 to 103-6 are slightly larger than the refractive index of the optical resin layer 105.
[0015]
11C is a cross-sectional view taken along line AA shown in FIG. 11A, and FIG. 11D is a cross-sectional view taken along line BB shown in FIG. As shown in FIGS. 11C and 11D, the cores 104-1 and 104-2 have substantially the same width (length in the vertical direction in FIG. 11C) at a constant distance from the end face. After that, it has a tapered shape in which the tip portion gradually becomes thinner toward the groove 106. For this reason, the cores 104-1 and 104-2 do not exist between the lower clad 102-2 and 102-5 and the upper clad 103-2 and 103-5 in the vicinity of the groove 106, both of which are directly They are in a laminated state (see FIGS. 11A and 11B).
[0016]
In the present invention, the optical waveguides in the section where the widths of the cores 104-1 and 104-2 are set to be substantially constant are referred to as “first optical waveguides”, and the cores 104-1 and 104-2 are provided. The optical waveguide in the non-interval is referred to as “second optical waveguide”, and the optical waveguide in the interval in which the widths of the cores 104-1 and 104-2 are gradually narrowed toward the groove 106 is referred to as “transition waveguide”.
[0017]
Next, the manufacturing process of the waveguide embedded optical circuit 100 of this embodiment will be described.
[0018]
First, a substrate 101 having a predetermined area is prepared, and a lower cladding layer and a core layer are formed in this order on one surface thereof.
[0019]
Next, the core layer is patterned to form the cores 104-1 and 104-2. The shapes of the cores 104-1 and 104-2 are as described above, and the cores 104-1 and 104-2 are patterned into a shape having a portion having a constant width and a tapered portion in which the width is gradually reduced.
[0020]
Next, an upper cladding layer is formed on the entire surface.
[0021]
Next, the laminated body of the lower clad layer and the upper clad layer (including the cores 104-1 and 104-2 in part) is patterned to obtain a central rod-like body (102-2, 103-2, 102-5, 103-5) and two rod-shaped bodies (102-1, 103-1, 102-4, 103-4) and (102-3, 103-3, 102-6, 103-6). Here, since the central rod-shaped body is used as the first optical waveguide and the core of the second optical waveguide (second core), the dimension shape and the core 104-1 in the rod-shaped body, It is necessary to accurately control the position of 104-2.
[0022]
Then, the optical resin layer 105 is filled between the rod-shaped bodies on both sides so as to cover the central rod-shaped body, and after hardening this, the groove 106 is formed.
[0023]
Thus, the waveguide embedded optical circuit 100 of this embodiment is completed.
[0024]
Here, as a method of patterning the laminated body of the lower cladding layer and the upper cladding layer to form a rod-shaped body, a mask film is formed on the surface of the upper cladding layer, and then a photoresist is formed on the surface of the mask film. Is applied, and the photoresist corresponding to the three rod-shaped bodies is exposed to form an etching pattern to form an etching pattern. Then, the mask film is patterned using the etching pattern, and the lower cladding layer and the mask film are formed using the mask film. It is preferable to remove unnecessary portions of the laminate of the upper clad layer by dry etching.
[0025]
The invention of Japanese Patent Application No. 2002-295334 solves the problem that the loss due to the diffraction phenomenon is large, but it is necessary to accurately control the position of the core relative to the rod-like body for further improvement. That is, since the central rod-shaped body is used as the first optical waveguide and the core of the second optical waveguide (second core), the dimension shape and the cores 104-1 and 104 in the rod-shaped body are used. The position of -2 needs to be accurately controlled. In the above-described process, when the photoresist etching pattern corresponding to the rod-shaped body is formed, the positions of the cores 104-1 and 104-2 are determined by the convex portions of the upper clad layer generated by the cores 104-1 and 104-2. It has been recognized that the protrusions of the upper cladding layer may be difficult to see, and the relative positions of the cores 104-1 and 104-2 with respect to the photoresist etching pattern may not be accurately controlled. Therefore, the relative positions of the rod-shaped body patterned with the photoresist and the cores 104-1 and 104-2 cannot be accurately controlled, and the shape of the beam whose spot size has been converted by the rod-shaped body is distorted and the loss increases. was there.
[0026]
In addition, even in the case where a step, that is, a groove, is provided in the clad between adjacent cores in the “2002 Society of Electronics, Information and Communication Engineers Electronics Society Conference C-3-35”, the position of the clad rod and the core surrounding the core It is necessary to control precisely. FIG. 12 is a structural diagram of the “C-3-35”. Here, “Under cladding”, “Core”, and “Over cladding” shown in FIG. 12 correspond to a rod-shaped body.
[0027]
Therefore, an object of the present invention is to provide an optical waveguide in which the position of the core is accurately controlled with respect to the clad rod-shaped body, and a method for manufacturing the optical waveguide.
[0028]
[Means for Solving the Problems]
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention for a spot size conversion waveguide will be described in detail with reference to the accompanying drawings.
[0030]
FIG. 1 is a view showing a first manufacturing method of a spot size conversion waveguide which is a preferred embodiment of the present invention. For simplicity, only one rod-like body is shown. First, a quartz glass substrate 201 having a predetermined area is prepared (FIG. 1A), and a plurality of core marks 206 are formed on the substrate (FIG. 1B).
[0031]
FIG. 3 is a view of the core mark 206 as viewed from above the substrate 201. Although the form of the core mark 206 is not particularly limited, in the present embodiment, the core mark 206 has a shape in which four squares each having a side of 20 μm form a cross shape with an interval of 10 μm and are arranged in a lattice shape. The film thickness of the core mark can also be set arbitrarily in consideration of visibility and ease of manufacture. Also, the position and number on the substrate can be set as appropriate so that the alignment with the photomask can be performed appropriately.
[0032]
The method of forming the core mark 206 is not particularly limited, but after forming a core mark film on one surface of the substrate 201, a positive photoresist is applied onto the surface of the core mark film, and the core mark 206 is formed. It is preferable that a photoresist other than the portion corresponding to 206 is exposed to form an etching pattern, and unnecessary portions of the core mark film are removed by dry etching using this etching pattern. Here, the material and film forming method of the core mark film are not particularly limited. For example, it is preferable to form a material such as WSi, Cr, Au, or Pt by sputtering, vacuum deposition, or the like. . Alternatively, the core mark 206 may be formed by directly processing the substrate by etching or the like.
[0033]
Next, the lower clad layer 202 and the core layer 204 are formed in this order on one surface of the substrate having the core mark 206 (FIG. 1C). A method for forming the lower cladding layer 202 and the core layer 204 is not particularly limited, but a vapor phase growth method using a chemical species including constituent elements of the lower cladding layer 202 and the core layer 204, for example, a CVD method. It is preferable to use a sputtering method, a vacuum deposition method, an FHD (Frame Hydrolysis Deposition) method, a coating method, or the like. When quartz glass is used as the material of the lower cladding layer 202 and the core layer 204, productivity and film quality are improved. From the viewpoint, the CVD method or the FHD method is particularly preferably used. When a polymer is used as the material for the lower cladding layer 202 and the core layer 204, the coating method is particularly preferably used from the viewpoint of simplicity.
[0034]
Next, a core mask film 207 for patterning the core 212 is formed on the core layer 204 (FIG. 1D). When the core mask film 207 is formed, the lower cladding layer 202 above the core mark 206 is covered with a jig or the like so that the core mask film 207 after the film formation does not hinder the visibility of the core mark 206.
[0035]
As with the core mark 206, the material and film forming method of the core mask film 207 are not particularly limited. For example, a material such as WSi, Cr, Au, or Pt is formed by sputtering, vacuum deposition, or the like. It is preferable.
[0036]
Next, a photoresist 208 is applied on the core mask film 207, and the photoresist 208 other than the portion corresponding to the core shape is exposed using the photomask 209 (FIG. 1E). In that case, after aligning the position of the core mark 206 provided on the substrate and the mask mark 210 provided on the photomask 209 corresponding to the core mark 206, the portion corresponding to the core mask 211 is irradiated with light. The photoresist 208 other than those is exposed. This photomask 209 has a pattern 219 of a Cr core mask 211 and a mask mark 210 on a quartz glass substrate, and the position of the pattern of the core mask 211 is accurately controlled with respect to the mask mark 210.
[0037]
FIG. 4 is a view of the photomask 209 as viewed from above. A spot size conversion optical waveguide core pattern 219 is provided near the center, and a mask mark 210 is provided at the end. The form of the mask mark 210 is not particularly limited, and may be any shape corresponding to the core mark 206. However, in this embodiment, the mask mark 210 has a cross shape with a width of 6 μm and a side of 46 μm. Therefore, if the cross mark of the core mark 206 having a width of 10 μm is aligned with the cross mark of the mask mark 210 having a width of 6 μm, the position of the photomask 209 relative to the substrate can be accurately aligned.
[0038]
Next, unnecessary portions of the core mask film 207 are removed by etching using a photoresist to form the core mask 211 (FIG. 1F).
[0039]
Next, the core 212 is patterned using the core mask 211 (FIG. 1G). The core 212 has a shape including a portion having a constant width and a tapered portion in which the width gradually decreases. Here, the method of patterning the core 212 is not particularly limited, but it is preferable to remove unnecessary portions of the core layer 204 by dry etching.
[0040]
Next, after the core mask 211 remaining on the top of the core 212 is removed by etching or the like, the upper clad layer 203 is formed on the entire surface (FIG. 1H). A method for forming the upper clad layer 203 is not particularly limited, but, like the lower clad layer 202 and the core layer 204, a vapor phase growth method or a coating method using a chemical species containing a constituent element of the upper clad layer 203 is used. In the case where quartz glass is used as the material of the upper cladding layer 203, it is particularly preferable to use the CVD method or the FHD method as described above, and the case where a polymer is used as the material of the upper cladding layer 203. It is particularly preferable to use the coating method as described above.
[0041]
Next, a rod-shaped body mask film 213 for patterning the rod-shaped body 218 is formed on the upper clad layer 203 (FIG. 1 (i)). At this time, in order to ensure the visibility of the core mark 206 after the rod-shaped body mask film 213 is formed, the film is formed by covering the upper clad layer 203 above the core mark 206 with a jig or the like.
[0042]
As with the core mark 206, the material and film forming method of the rod-shaped body mask film 213 are not particularly limited. For example, a material such as WSi, Cr, Au, or Pt is formed by sputtering or vacuum evaporation. It is preferable to form a film.
[0043]
Next, a positive type photoresist 214 is applied on the rod-shaped body mask film 213, and the photoresist 214 other than the portion corresponding to the rod-shaped body mask 217 is exposed using the photomask 215 (FIG. 1 (j)). In that case, after aligning the position of the core mark 206 provided on the substrate and the mask mark 216 provided on the photomask 215 corresponding to the core mark 206, the light is irradiated to correspond to the rod-shaped body mask 217. The photoresist 214 to be cured is cured. This photomask 215 has a Cr rod mask 217 pattern and a mask mark 216 on a quartz glass substrate, and the position of the rod mask 217 pattern is accurately controlled with respect to the mask mark 216. . By aligning the positions of the substrate 201 and the photomask 215 in this manner, the rod-shaped body mask 217 whose position with respect to the core mark 206 is accurately controlled can be formed (FIG. 1 (k)).
[0044]
Like the mask mark 210, the form of the mask mark 216 is not particularly limited, and may be any shape corresponding to the core mark 206. For example, the shape may be the same as the mask mark 210 shown in FIG.
[0045]
Next, the rod-shaped body 218 is patterned using the rod-shaped body mask 217 (FIG. 1 (l)). Here, the method for patterning the rod-shaped body 218 is not particularly limited, but it is preferable to remove unnecessary portions of the upper clad 203 and the lower clad 202 by dry etching to form a step in the clad. Here, FIG. 1 shows an example in which both the upper clad and the lower clad are removed to form a step, but if necessary, a part of the upper clad or a part of the substrate is removed. The method of forming the step can be selected as appropriate.
[0046]
Then, after removing the rod-shaped body mask 217 remaining on the upper portion of the rod-shaped body 218 by etching or the like, an optical resin layer 205 is formed so as to cover the rod-shaped body 218 (FIG. 1 (m)), and this is cured. As described above, a wafer of a spot size conversion element can be manufactured.
[0047]
Thereafter, grooves as shown in FIG. 11 are formed. The method for forming the groove is not particularly limited, but it is preferable to process by dicing. Further, like the patterning of the core 211 and the like, the optical resin layer 205, the upper cladding layer 203, and the lower cladding layer 202 may be removed by dry etching.
[0048]
As described above, according to the first manufacturing method of the present invention, it is possible to form the rod-shaped body mask 217 whose position with respect to the core mark 206 is accurately controlled, so that the relative position between the core 212 and the rod-shaped body 218 is changed. It is possible to manufacture a spot size conversion waveguide that can be accurately controlled, has little beam shape distortion, and has a low loss.
[0049]
FIG. 2 is a view showing a second manufacturing method of a spot size conversion waveguide which is a preferred embodiment of the present invention. For simplicity, only one rod-like body is shown. The second manufacturing method is different from the first manufacturing method in that a core mask 310 and a core mark 306 for patterning the core 311 are formed simultaneously.
[0050]
Hereinafter, the second manufacturing method will be described with reference to the drawings, focusing on differences from the first manufacturing method.
[0051]
First, a quartz glass substrate 301 having a predetermined area is prepared (FIG. 2A), and a lower clad layer 302 and a core layer 304 are formed in this order on one surface of the substrate (FIG. 2B). ).
[0052]
Next, a core mask film 307 for patterning the core 311 is formed on the core layer 304 (FIG. 2C).
[0053]
Next, a positive photoresist 308 is applied on the core mask film 307, and the photoresist 308 other than the portions corresponding to the core mask 310 and the core mark 306 is exposed using the photomask 309 (FIG. 2D). This photomask 309 has a pattern of a core mask 310 of Cr and a core mark 306 on a quartz glass substrate, and the position of the pattern of the core mask 310 is accurately controlled with respect to the core mark 306.
[0054]
The form of the core mark 306 is not particularly limited, but may be the same shape as the first manufacturing method described above, for example.
[0055]
Next, unnecessary portions of the core mask film 307 are removed by etching using a photoresist (FIG. 2E). Thus, if the core mask 310 and the core mark 306 for patterning the core 311 are formed at the same time, the photomask 309 can be used without particularly aligning the relative positions of the core mask 310 and the core mark 306 as in the first manufacturing method. It can be controlled accurately.
Next, after removing unnecessary photoresist, the core 311 is patterned using the core mask 310 (FIG. 2F).
[0056]
Next, the core mask 310 remaining on the upper portion of the core 311 is removed by etching or the like while leaving the core mark 306 (FIG. 2G). In that case, since it is only necessary to form a photoresist so as to protect only the core mark 306, the photomask accuracy required at the time of forming the photoresist may be loose.
[0057]
Next, the upper clad layer 303 is formed on the entire surface (FIG. 2H).
[0058]
Next, a rod-shaped body mask film 312 for patterning the rod-shaped body 317 is formed on the upper clad layer 303 (FIG. 2 (i)). At this time, in order to ensure the visibility of the core mark 306 after the rod-shaped body mask film 312 is formed, the film is formed by covering the upper clad layer 303 above the core mark 306 with a jig or the like.
[0059]
Next, a photoresist 313 is applied on the rod-shaped body mask film 312, and the photoresist 313 other than the portion corresponding to the rod-shaped body 317 is exposed (FIG. 2 (j)). In that case, after aligning the position of the core mark 306 provided on the substrate and the mask mark 315 provided on the photomask 314 corresponding to the core mark 306, light is irradiated to correspond to the rod-shaped body 317. The photoresist 313 is exposed. The photomask 314 has a Cr rod-shaped body 317 pattern and a mask mark 315 on a quartz glass substrate, and the position of the pattern of the rod-shaped body 317 is accurately controlled with respect to the mask mark 315. If unnecessary photoresist is removed by etching, a rod-shaped body mask 316 whose position relative to the core mark 306 is accurately controlled can be formed (FIG. 2 (k)).
[0060]
Next, the rod-shaped body 317 is patterned by etching or the like using the rod-shaped body mask 316 (FIG. 2 (l)).
[0061]
Then, after removing the rod-shaped body mask 316 remaining on the upper portion of the rod-shaped body 317 by etching or the like, an optical resin layer 305 is formed so as to cover the rod-shaped body 317 (FIG. 2 (m)), and this is cured. As described above, a wafer of a spot size conversion element can be manufactured. Thereafter, grooves as shown in FIG. 11 are formed.
[0062]
According to the second manufacturing method, the core mask 310 and the core mark 306 for patterning the core 311 are formed at the same time, so that the relative positions of the core mask 310 and the core mark 306 are not particularly matched as in the first manufacturing method. Thus, the photomask 309 can be accurately controlled, the process can be simplified, and the manufacturing yield can be improved. Further, since it is possible not to leave a mask film made of metal or the like in the spot size conversion element, it is possible to prevent cracks or the like generated at the interface between the metal and glass.
[0063]
The spot size conversion optical waveguide can be manufactured by the method as described above. The manufacturing method of the optical waveguide of the present embodiment is not limited to this, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is done.
[0064]
For example, in the above embodiment, the optical resin layer is also provided in the portion corresponding to the first optical waveguide. However, since the optical resin layer functions as a clad of the second optical waveguide, The optical resin layer may be omitted in the portion corresponding to the waveguide. Further, it is not necessary to use an optical resin layer as the second cladding, and other materials may be used as long as the refractive index is different from that of the lower cladding layer and the upper cladding layer.
[0065]
The position of the core mark is not limited to the substrate as in the first manufacturing method or the core layer as in the second manufacturing method. For example, the clad layer, the back side of the core layer, or the lower cladding with respect to the substrate It may be on the layer, inside the lower cladding layer, or inside the upper cladding layer in a range where the core can be recognized.
[0066]
Also, instead of the quartz glass substrate, for example, the surface of the Si substrate is made of SiO by a thermal oxidation method. ₂ Layer formed or SiO on Si substrate ₂ A film or the like obtained by forming a film may be used. As long as the refractive index is lower than that of the lower cladding, SiO added with B, P, etc. ₂ Etc. may be formed.
[0067]
Further, the shape, size, position, and the like of the core mark can be arbitrarily selected so as to facilitate alignment of the core mark and the photomask, such as a square or a cross shape having a side of about 10 μm.
[0068]
Further, the present invention can be applied not only to a spot size conversion optical waveguide, but also to an optical waveguide that needs to accurately control the position of the core of the clad surrounding the core and the core. That is, when forming a rod-like body like the “2002 Society of Electronics, Information and Communication Engineers Electronics Society C-3-35” shown in FIG. 12, the position where the step (in this case, the heat insulating groove) is formed in the clad, However, the present invention can also be applied to such a case.
[0069]
Further, the level difference of the cladding is not limited to the one substantially parallel to the core as described above, and may be, for example, a direction crossing the core as in the case of embedding a filter, or an oblique direction with respect to the core. .
[0070]
【Example】
[Example 1]
According to the first manufacturing method of the optical waveguide of the above embodiment, there are a large number of spot size conversion waveguide patterns in the central portion of the φ3 inch quartz glass substrate, and four squares each having a side of 20 μm are formed in the vicinity of the outer peripheral portion. An optical waveguide wafer having core marks formed in a cross shape at intervals of 10 μm and arranged in a lattice shape was manufactured, and a spot size conversion waveguide was manufactured.
[0071]
As a material of the core 212 (first core), SiO doped with Ge ₂ Glass (refractive index: 1.4558) is used, and the material of the lower clad 202 and the upper clad 203 (first clad = second core) is BPSG (SiO with B and P added). ₂ Glass, refractive index: 1.4501) was used, and an optical adhesive (refractive index: 1.4437) was used as the material of the optical resin layer 205 (second clad).
[0072]
The size of the core 212 (first core) is set such that the length of the portion corresponding to the first optical waveguide is 200 μm, and the height and width of the portion corresponding to the first optical waveguide are both 7 μm. And the length x of the tapered portion corresponding to the transition waveguide ₂ Is set to 1000 μm, and the width x of the tip of the taper portion ₁ Was set to 0.4 μm.
[0073]
The rod-shaped body (first clad = second core) composed of the lower clad 202 and the upper clad 203 was set to have a length of 2400 μm, a height of 35 μm, and a width of 34 μm. Of these, the 200 μm section (the part corresponding to the first optical waveguide) in which the height and width of the core 212, which is the first core, are set to be constant functions as the first cladding. The non-existent 1200 μm section (the part corresponding to the second optical waveguide) functions as the second core. In addition, the section of 1000 μm in which the core 212 is tapered (portion corresponding to the transition waveguide) gradually changes from the function as the first cladding to the function as the second core.
[0074]
Specifically, a spot size conversion optical waveguide was fabricated by the following process.
[0075]
First, a 0.2 μm thick WSi film is formed on a quartz glass substrate 201 having a diameter of 3 mm and a thickness of 1 mm by sputtering, and four squares each having a side of 20 μm form a cross shape with an interval of 10 μm in a lattice shape. Four aligned core marks 206 were formed in the vicinity of the outer periphery of the substrate 201 at intervals of 90 degrees with respect to the center. Next, BPSG having a film thickness of 14 μm is formed on the substrate 201 having the core mark 206 by the CVD method to form the lower cladding layer 202, and then SiO added with Ge thereon ₂ A core layer 204 was formed by forming glass with a film thickness of 7 μm by a CVD method. Next, in order to ensure the visibility of the core mark 206, the upper portion of the core mark 206 is protected with a jig, and WSi as the core mask film 207 is formed with a thickness of 1 μm by a sputtering method, and then the photoresist 208 is formed. Was applied. Next, a photomask 209 having a cross-shaped mask mark 210 having a width of 6 μm and a side of 46 μm corresponding to the core mark 206 at a position corresponding to the core mark 206 and having a pattern 219 of the core mask 211 at the center is used. After aligning the positions of the mask mark 210 and the core mark 206 provided on the photomask 209, the photoresist of the core mask 211 portion was cured by irradiating light. Next, only the WSi film in the portion of the core mask 211 was removed by etching, unnecessary portions were removed, and then the core layer 204 was etched to form a core 212 having a height and width of 7 μm. Next, after removing the WSi remaining on the upper portion of the core 212, a BPSG film having a thickness of 21 μm was formed by a CVD method to form the upper clad layer 203. Next, in order to ensure the visibility of the core mark 206, the BPSG located above the core mark 206 is protected with a jig, and a WSi film having a thickness of 2 μm is formed by sputtering, and then a photoresist 214 is applied. did. Next, a cross-shaped mask mark 216 having a width of 6 μm and a side of 46 μm corresponding to the core mark 206 is provided at a position corresponding to the core mark 206, and a photomask 215 having a rod-shaped mask 217 pattern at the center. The position of the mask mark 216 provided on the photomask 215 and the position of the core mark 206 were aligned, and then light was irradiated to cure the photoresist in the portion of the rod-shaped body mask 217. Next, only the WSi film in the portion of the rod-shaped body mask 217 is removed by etching, and unnecessary portions are removed, and then the upper cladding layer 203 and the lower cladding layer 202 are etched to form a rod-shaped body having a height of 35 μm and a width of 34 μm. 218 was formed. Next, after removing WSi remaining on the upper portion of the rod-shaped body 218, the optical adhesive 2 having a thickness of about 0.1 mm was applied to form an optical resin layer 205.
[0076]
Light having an optical electric field mode distribution (spot size = about 10 μm) shown in FIG. 5A is incident on the spot size converting optical waveguide having such a structure from the first optical waveguide side, and the second optical The optical electric field mode distribution of the light emitted from the waveguide side was measured. As a result, the optical electric field mode distribution of the light emitted from the second optical waveguide side was as shown in FIG. As shown in FIG. 5B, the spot size of the light emitted from the second optical waveguide was about 28 μm, and it was confirmed that the spot size was enlarged by 2.8 times.
[0077]
[Example 2]
According to the second manufacturing method of the spot size conversion optical waveguide of the above embodiment, the central portion of the φ3 inch quartz glass substrate 301 has a large number of spot size conversion waveguide patterns, and has a side of 20 μm in the vicinity of the outer peripheral portion. An optical waveguide wafer having core marks having a shape in which four squares form a cross shape with an interval of 10 μm and aligned in a lattice shape, and a spot size conversion waveguide was manufactured.
[0078]
The spot size conversion optical waveguide included in the second embodiment is made of the same material and size as that of the first embodiment.
[0079]
A BPSG film having a thickness of 14 μm is formed on a quartz glass substrate 301 having a thickness of 3 mm and a thickness of 1 mm by a CVD method to form a lower clad layer 302, and Ge is added on the SiO 2 layer. ₂ A core layer 304 was formed by forming glass with a film thickness of 7 μm by a CVD method. Next, WSi as the core mask layer 307 was formed to a thickness of 1 μm by a sputtering method, and a photoresist 308 was applied. Next, four squares each having a side of 20 μm form a cross shape with an interval of 6 μm and are arranged in a lattice pattern, and have four patterns in the vicinity of the outer periphery at intervals of 90 degrees with respect to the center of the substrate 301. Used the photomask 309 having the pattern of the core mask 310 to cure the core mark 306 and the photoresist 308 in the core mask 310 portion. Next, etching removes unnecessary portions while leaving only the WSi film of the core mark 306 and the core mask 310, and then the core layer 304 is etched to form four squares each having a side of 20 μm to form a cross shape with an interval of 10 μm. A core mark 306 and a core 312 having a height and a width of 7 μm were formed. Next, a photoresist was applied and only the photoresist in the vicinity of the core mark 306 was cured, and then the WSi film remaining on the core was removed while leaving the WSi film as the core mark 306. Next, BPSG having a film thickness of 21 μm was formed by a CVD method to form the upper cladding layer 303. Next, in order to ensure the visibility of the core mark 306, the BPSG located above the core mark 306 is protected with a jig, and the WSi film as the rod-shaped body mask film 312 is formed to a thickness of 2 μm by sputtering. After film formation, a photoresist 313 was applied. Next, a cross-shaped mask mark 315 having a width of 6 μm and a side of 46 μm is provided at a position corresponding to the core mark 306, and a photomask 314 having a pattern of a rod-shaped mask 316 is used in the center portion. After aligning the position of the provided mask mark 315 and the core mark 306, light was irradiated to cure the photoresist 313 in the portion of the rod-shaped body mask 316. Next, only a portion of the WSi film corresponding to the rod-shaped body 317 was removed by etching, and unnecessary portions were removed, and then BPSG was etched to form a rod-shaped body 317 having a height of 35 μm and a width of 34 μm. Next, after removing the WSi film remaining on the upper portion of the rod-shaped body 317, an optical adhesive having a thickness of about 0.1 mm was applied to form an optical resin layer 305.
[0080]
For the spot size conversion optical waveguide having such a structure, a groove having a width of 100 μm that divides substantially the center of the second optical waveguide was provided, and an optical filter was embedded. As a result, an optical filter module having good characteristics with an insertion loss of 1 dB or less could be produced.
[0081]
【The invention's effect】
As described above, in the manufacturing method of the present invention, the core mark for controlling the position of the core and the position of the rod-shaped body is provided, and the core and the rod-shaped body are patterned with respect to the core mark. The position of the core with respect to the rod-shaped body can be accurately controlled.
[Brief description of the drawings]
FIG. 1 is a diagram showing a method for manufacturing an optical waveguide according to a preferred embodiment of the present invention.
FIG. 2 is a diagram showing a method of manufacturing an optical waveguide according to a preferred embodiment of the present invention, different from FIG.
3 is a view of a substrate 201 having a core mark 206 as viewed from above, and an enlarged view of the core mark 206. FIG.
FIG. 4 is a view of a photomask 209 viewed from above and an enlarged view of a mask mark.
5 is a graph showing optical electric field mode distribution in Example 1. FIG. (A) is an optical electric field mode distribution of light incident on the first optical waveguide side, and (b) is an optical electric field mode distribution of light emitted from the second optical waveguide side.
6A and 6B are diagrams showing a ferrule that connects an optical fiber, which is a kind of optical waveguide, where FIG. 6A is a schematic perspective view, and FIG. 6B is a cross-sectional view taken along line DD shown in FIG. .
7 is a view showing a state in which an optical filter is attached to the ferrule 10 shown in FIG. 6. FIG. 7 (a) is a schematic perspective view, and FIG. 7 (b) is a cross-sectional view taken along line EE shown in FIG. is there.
8A and 8B are diagrams showing a waveguide-embedded optical circuit that is a kind of optical waveguide, in which FIG. 8A is a schematic perspective view, and FIG. 8B is a cross-sectional view taken along line FF shown in FIG. .
9 is a diagram showing a state in which an optical filter is inserted into the waveguide-embedded optical circuit 20 shown in FIG. 8, where (a) is a schematic perspective view, and (b) is a GG line shown in (a). FIG.
FIGS. 10A and 10B are diagrams for explaining a mechanism of loss generation due to a diffraction phenomenon. FIG. 10A shows a case where the core diameter is small, and FIG. 10B shows a case where the core diameter is large.
11A and 11B are diagrams showing a waveguide-embedded optical circuit 100 according to the present invention, in which FIG. 11A is a schematic perspective view seen from one direction, and FIG. 11B is a schematic perspective view seen from the reverse direction; FIG. 2C is a cross-sectional view taken along the line AA shown in FIG. 1A, and FIG. 4D is a cross-sectional view taken along the line BB shown in FIG.
FIG. 12 is a structural diagram of “2002 Society of Electronics, Information and Communication Engineers Electronics Society Conference C-3-35”.
[Explanation of symbols]
201, 301 substrate
202, 302 Lower clad
203, 303 Upper clad
204, 304 Core layer
205, 305 Resin layer
206, 306 Core Mark
207, 307 Core mask film
208, 214, 308, 313 Photoresist
209, 215, 309, 314 Photomask
210, 216, 315 Mask mark
211, 310 core mask
212,311 core
213, 312 Rod-shaped mask film
217, 316 Bar-shaped body mask
218, 317 Rod-shaped body

Claims (6)

An optical waveguide wafer comprising a core and a clad having a step positioned with respect to the core,
An optical waveguide wafer comprising a mark for recognizing the position of the core. A method of manufacturing an optical waveguide having a core and a clad having a step positioned with respect to the core,
Forming a core on the lower cladding;
Covering substantially the entire surface of the core with an upper cladding;
Providing a wafer with a mark for recognizing the position of the core;
Providing a step in the upper clad, or both the upper clad and the lower clad, or both clad and the substrate;
An optical waveguide manufacturing method including: A method of manufacturing an optical waveguide having a core and a clad having a step positioned with respect to the core,
Patterning a core for guiding light on the lower clad, and forming a layer for providing a mark on the wafer for recognizing the position of the core;
Covering substantially the entire surface of the core with an upper cladding;
Providing a step in the upper clad or both the upper clad and the lower clad;
A method for manufacturing an optical waveguide according to claim 1. A core for guiding light;
A first cladding covering substantially the entire surface of the core;
A second cladding covering at least a portion of the first cladding excluding the light propagation direction;
A mark for recognizing the position of the core;
An optical waveguide wafer comprising: Forming a first cladding and a second cladding adjacent to each other;
Forming a core for guiding light on the first cladding;
Covering substantially the entire surface of the core with a first cladding;
Providing a wafer with a mark for recognizing the position of the core;
The method for producing a wafer according to claim 4, comprising: Forming a first cladding and a second cladding adjacent to each other;
Patterning a core for guiding light on the first clad and forming a layer for providing a mark on the wafer for recognizing the position of the core;
Covering substantially the entire surface of the core with a first cladding;
The method for producing a wafer according to claim 4, comprising:

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