JP3672421B2 - Method for forming optical waveguide coupler - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of an optical waveguide coupler of an optical element and a method for forming the same.
[0002]
[Prior art]
Conventionally, as a structure of an optical waveguide coupler in an optical element, there is a literature (Reference: Proceedings of the IEICE General Conference 1995) C-213 Subdivided Si for non-adjustment high-precision mounting of fiber on Si substrate for optical planar mounting -Study on V-groove) According to this optical waveguide coupler, the optical fiber is fixed on the Si substrate so that it is not necessary to adjust the alignment between the optical waveguide made of the SiO ₂ thin film formed on the Si substrate and the core portion of the optical fiber. Grooves are provided. If an optical fiber is fixed in this groove, the optical axis is aligned and mounting can be performed with higher accuracy. In order to form such a connection structure, at least a step of providing an optical waveguide layer on the Si substrate, a step of forming the optical waveguide by channeling the optical waveguide layer, an end face of the optical waveguide, and an optical fiber And a step of forming a groove for fixing an optical fiber by etching on a Si substrate.
[0003]
[Problems to be solved by the invention]
However, when an optical waveguide coupler is formed using the above-described forming method, it takes time to form, the number of steps is large, and mass productivity is low.
[0004]
Moreover, since the alignment of the optical axes of the optical fiber and the optical waveguide must be performed for each optical waveguide coupler to be formed, the forming operation is difficult.
[0005]
For this reason, the advent of an optical waveguide coupler that can mount an optical fiber on an optical waveguide with high accuracy and a method that can easily form the optical waveguide coupler has been desired.
[0006]
[Means for Solving the Problems]
For this reason, according to the method for forming an optical waveguide coupler of the present invention, in forming an optical waveguide coupler for coupling an optical fiber and an end face of the optical waveguide, a V for fixing the optical fiber to the common substrate is used. a groove, a convex or concave optical waveguide forming section to form a step of forming at once by pressing the same, the optical waveguide layer containing layer on the upper surface of the common substrate including a V groove and an optical waveguide forming section And dicing at least the optical waveguide layer-containing layer at the boundary between the V-groove and the optical waveguide forming portion to form the optical waveguide and the optical waveguide end face, and the V-groove end face facing the optical waveguide end face. It is good to contain. At this time, the step of forming the V-groove and the optical waveguide forming portion is performed by pressing so that the optical fiber and the end face of the optical waveguide are correctly coupled with the optical waveguide layer-containing layer formed on the V-groove. It is preferable that the depth at which the groove is formed is adjusted. By pressing, the V-groove and the optical waveguide forming portion for determining the positions of the optical fiber and the optical waveguide can be formed at a time on the common substrate. With such a simple process, the optical waveguide can be formed on the upper side of the optical waveguide forming portion, and a smooth waveguide end face can be formed. Therefore, the number of steps can be reduced, and the optical waveguide coupler can be formed by simple processing. In addition, since the dimensions of the pressing mold are initially set, if the pressing process is performed using this mold, the positions of the optical fiber and the optical waveguide are formed one by one when the same optical waveguide coupling portion is formed. There is no need to match. Therefore, it is possible to save the trouble of difficult alignment.
[0018]
Further, a thin film having a refractive index higher than that of the clad layer using a crystallized glass or ceramic as the common substrate, a clad layer made of SiO ₂ thin film as the optical waveguide layer-containing layer, and a material in which impurities are added to SiO ₂ A multilayer film with an optical waveguide layer made of The clad layer can further improve the light confinement effect in the optical waveguide layer. As the ceramic used for the common substrate, for example, zirconia capable of press working is used.
[0019]
The common substrate may be crystallized glass or ceramic, and the optical waveguide layer-containing layer may be an optical waveguide layer made of a polymer having a higher refractive index than the common substrate. As the polymer used at this time, PMMA (polymethyl methacrylate) or the like is preferable.
[0020]
In forming the optical waveguide coupler, it is preferable to form an optical waveguide layer with a uniform film thickness on the upper surface of the common substrate, and to fix the optical fiber to the common substrate provided with the optical waveguide layer. Forming a V-groove and a convex or concave optical waveguide forming portion at the same time by the same pressing process, and dicing at least the optical waveguide layer at the boundary between the V-groove and the optical waveguide forming portion, an optical waveguide and the optical waveguide end face, viewing including the step of forming the said optical waveguide end face facing the V groove end surfaces, forming a V groove and the optical waveguide forming section, by press working, the optical waveguide in the optical waveguide A step of forming a V-groove having an optical waveguide layer is preferably formed on the convex upper portion or the concave bottom portion of the formation portion. Since the optical waveguide layer is deposited on the common substrate with a uniform film thickness and then pressed, a partial difference in film thickness on the substrate of the optical waveguide layer is eliminated. For this reason, it can be expected that the alignment accuracy between the optical fiber and the optical waveguide is further improved. Also in this forming method, the number of steps can be reduced as compared with the conventional method, and the processing in each step can be simplified. Further, since the positions of the optical fiber and the optical waveguide are also determined when setting the dimensions of the press mold, it is necessary to position each time and form a V-groove when forming the same optical waveguide coupler. Will disappear.
[0021]
In the case of forming the optical waveguide coupler by the above-described method, preferably, the common substrate is made of glass, crystallized glass, or ceramic, and the optical waveguide layer is made of glass having a refractive index higher than that of the common substrate. It is good to form as a material. The common substrate and the optical waveguide layer are preferably made of the above materials suitable for press working.
[0022]
Alternatively, the common substrate may be formed using plastic as a material, and the optical waveguide layer may be formed using a material having a refractive index higher than that of the common substrate.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Each figure is only schematically shown to the extent that the invention can be understood, and therefore the invention is not limited to the illustrated examples. Further, in the drawing, hatching (hatched lines) indicating a cross section is omitted except for a part for easy understanding of the drawing.
[0024]
<First Embodiment>
As a first embodiment, for example, an optical waveguide coupler having a single optical waveguide on a common substrate and connecting optical fibers to both ends of the optical waveguide will be described with reference to the drawings. To do. 2 to 4 are diagrams schematically showing main processes for forming the optical waveguide coupler of the present invention, and FIGS. 2A to 2D are plan views of the optical waveguide coupler as viewed from above. 3 (A) to 3 (D) are cross-sectional views showing cut surfaces cut along the line XX of FIGS. 2 (A) to 2 (D). 4 (A) to 4 (D) are cross-sectional views showing cut surfaces cut along the YY line in FIGS. 2 (A) to 2 (D).
[0025]
This optical waveguide coupler is formed as follows.
[0026]
First, the V-groove 13 and the optical waveguide forming portion 15 are formed in the common substrate 11 using press working.
[0027]
In this embodiment, first, the V-groove 13 to which the optical fiber is fixed and the portion 15 in which the optical waveguide is formed (referred to as an optical waveguide forming portion) are provided so that the optical fiber and the optical waveguide are preferably connected. It is formed on the common substrate 11 in the same process. In this example, as shown in FIGS. 2 (A) and 3 (A), a convex linear optical waveguide forming portion 15 and both ends (ends) of the straight line of the optical waveguide forming portion 15 are formed on the common substrate 11. V-groove 13 connected to each of the portion 15a and the end portion 15b) is formed.
[0028]
It is necessary to connect the optical fiber and the optical waveguide so as to reduce the connection loss of light as much as possible. For this reason, here, the dimensions of the pressing mold are determined so that the optical fiber and the optical waveguide are provided at a position where the core end surface of the optical fiber overlaps the optical waveguide end surface by 50 to 100%. The final mold dimensions are determined by repeating the experiment. In this embodiment, the length L of the common substrate 11 in the direction along the straight line of the optical waveguide is 2 cm, the length M of the common substrate 11 in the width direction of the optical waveguide is 1 cm, and the length of the V-groove 13 N is 5 mm, the width O of the V groove 13 is 150 μm (see FIG. 2A), the depth P of the V groove 13 is 129 μm, and the height Q from the bottom surface of the common substrate 11 to the upper side of the V groove 13 is 600 μm. The height R from the bottom surface of the common substrate 11 to the lower side of the convex optical waveguide forming portion 15 is 500 μm (see FIG. 3A), and the height S of the optical waveguide forming portion 15 is 6 μm (see FIG. A), the width T of the optical waveguide forming portion 15 is 4 μm (see FIG. 3A), and the length U of the optical waveguide forming portion 15 is 1 cm (see FIG. 4A). The dimensions of the press mold were determined. In addition, crystallized glass was used as the material for the common substrate 11, and here, Milaclon PP or Milaclon PH manufactured by NGK Corporation was used. In the press processing, the material of the common substrate 11 is put into a mold and then pressed to form (see FIGS. 2A, 3A, and 4A).
[0029]
Next, an optical waveguide layer-containing layer is formed on the upper surface of the common substrate.
[0030]
In this embodiment, the optical waveguide layer-containing layer 17 is composed of a clad layer and a multilayer film of an optical waveguide layer having a refractive index 1% higher than that of the clad layer (not shown). In this embodiment, the refractive index difference between the cladding layer and the optical waveguide layer is set to 1% in order to make the optical waveguide a single mode. The cladding layer is a SiO ₂ thin film, and the optical waveguide layer is a film in which Ge is mixed with SiO ₂ in order to increase the refractive index. A multilayer film as the optical waveguide layer-containing layer 17 is formed on the upper surface of the pressed common substrate 11 by a CVD method with a thickness of 4 μm (FIGS. 2B, 3B, and 4). See B).
[0031]
Next, at least the optical waveguide layer-containing layer at the boundary between the V groove and the optical waveguide forming portion is diced to form the optical waveguide and the optical waveguide end face, and the V groove end face facing the optical waveguide end face.
[0032]
Here, the optical waveguide layer-containing layer 17 at the boundary between the V-groove 13 and the optical waveguide forming portion 15 is diced, but in order to perform this dicing a little excessively, the common substrate 11 under the optical waveguide layer-containing layer 17 is diced. A groove 19 of about several tens of μm is formed. The width V of the groove 19 is 40 μm. The optical waveguide 21 and the optical waveguide end face 21a are formed by dicing (see FIGS. 2C, 3C, and 4C). This optical waveguide 21 is a channel-type optical waveguide.
[0033]
Through the above steps, an optical waveguide coupler can be formed.
[0034]
As a result, the alignment of the optical fiber and the optical waveguide, the formation of the V-groove on the common substrate, and the formation of the optical waveguide forming portion on the common substrate can be performed in the same process. An optical waveguide coupler can be formed by reducing the number of steps for forming the device and by simple processing. In addition, since the dimensions of the pressing mold are initially set, if the pressing process is performed using this mold, the positions of the optical fiber and the optical waveguide are formed one by one when the same optical waveguide coupling portion is formed. There is no need to match. Therefore, it is possible to save the trouble of difficult alignment.
[0035]
An example of the structure of the optical waveguide coupler formed in the above-described process will be described with reference to FIG. FIG. 1 is a schematic perspective view of the optical waveguide coupler according to the first embodiment.
[0036]
This optical waveguide coupler includes a common substrate 11, a V-groove 13 formed in the common substrate 11, and an end (15 a or 15 b) that is formed in the common substrate 11 and faces one end of the V-groove 13. A convex optical waveguide forming portion 15 having a channel-type optical waveguide 21 formed in the optical waveguide forming portion 15 is provided.
[0037]
The material of the common substrate 11 is a crystallized glass, channel optical waveguides 21, Yes constituted Te than a multilayer film of the cladding layer and the optical waveguide layer, the cladding layer is made of SiO ₂ thin film, optical The wave layer is made of a thin film in which Ge is added to SiO ₂ to make the refractive index 1% higher than that of the cladding layer. The convex optical waveguide forming portion 15 has a quadrangular cross-sectional shape. The groove 19 is formed by dicing for forming the optical waveguide 21 and the end face of the optical waveguide.
[0038]
Since the V-groove 13 for fixing the optical fiber to the common substrate 11 and the optical waveguide forming portion 15 are formed, the optical waveguide layer-containing layer 17 (or the optical waveguide layer 31) is formed on the optical waveguide forming portion 15. ), The optical waveguide 21 can be easily formed. Further, only by fixing the optical fiber in the V-groove 13 of the optical waveguide coupler, the core end face of the optical fiber and the end face of the optical waveguide face each other to align the optical axis. Therefore, the optical fiber can be easily mounted on the optical waveguide with high accuracy.
[0039]
When the optical fiber 23 is connected to the optical waveguide coupler, a structure as shown in FIGS. 2D, 3D, and 4D is obtained. As the optical fiber 23 connected to the optical waveguide coupler of this embodiment, for example, one having a diameter of 125 μm and a core 25 having a diameter of 8 μm is used. The optical fiber 23 is fixed to the V-groove 13 using an epoxy resin as an adhesive here.
[0040]
The core end face 25a of the optical fiber 23 faces the optical waveguide end face 21a of the channel type optical waveguide 21, and the area of the optical waveguide end face 21a facing the core end face 25a is 50% or more of the total area of the core end face 25a. It has become.
[0041]
As a result, since crystallized glass is used as the material for the common substrate, molding by press working can be performed with an accuracy of an error of 1 μm or less.
[0042]
In addition, since the channel type optical waveguide has a structure in which a cladding layer is provided around the optical waveguide layer, the effect of confining light in the optical waveguide layer can be improved.
[0043]
Further, the area of the region of the optical waveguide end face facing the core end face is at least 50% or more of the total area of the core end face. Thereby, in the optical waveguide coupler of this embodiment, it is said that there is little light connection loss, and it can be said that the optical fiber can be mounted on the optical waveguide with high accuracy.
[0044]
In the optical waveguide coupler of this embodiment, ceramic, plastic, and glass that can be pressed may be used for the common substrate. In addition, a polymer such as polymethyl methacrylate having a higher refractive index than that of the common substrate may be used for the channel type optical waveguide.
[0045]
Further, the optical waveguide forming portion may be a concave shape instead of a convex shape. In this case, an optical waveguide layer is formed at least in the recess, and this optical waveguide layer becomes a channel-type optical waveguide. The cross-sectional shape of the convex or concave optical waveguide forming portion may be triangular, quadrangular, trapezoidal, or semicircular.
[0046]
<Second Embodiment>
As a second embodiment, an optical waveguide coupler having the same structure as that of the optical waveguide coupler described in the first embodiment is shown in FIG. Will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view at a main process step corresponding to FIG. 3 of the first embodiment.
[0047]
Hereinafter, differences from the first embodiment will be described, and detailed description of points similar to those of the first embodiment will be omitted.
[0048]
First, an optical waveguide layer is formed on the upper surface of the common substrate.
[0049]
In this embodiment, glass is used as the material of the common substrate 11. The optical waveguide layer 31 is formed of glass having a uniform film thickness on the flat upper surface of the common substrate 11 and, for example, a glass whose refractive index is higher than that of the common substrate 11 by changing the composition. FIG. 5 (A)). The optical waveguide layer 31 is preferably formed using a sol-gel method or a sputtering method.
[0050]
Next, the V-groove 13 and the optical waveguide forming portion 15 are formed by pressing the common substrate 11 provided with the optical waveguide layer 31.
[0051]
The optical waveguide forming portion 15 has a concave quadrilateral cross-sectional shape. The dimensions of this press working mold are determined through experiments in advance so that the optical waveguide layer 31 in the concave portion of the optical waveguide forming portion 15 and the core of the optical fiber fixed to the V-groove 13 are in good connection. It is. By this pressing, the V-groove 13 and the optical waveguide forming portion 15 are formed in the common substrate 11 and the optical waveguide layer 31 (FIG. 5B).
[0052]
Next, as in the first embodiment, at least the optical waveguide layer 31 at the boundary between the V-groove 13 and the optical waveguide forming portion 15 is diced to form the optical waveguide 21 and the optical waveguide end face, and the optical waveguide. A V-groove end face facing the end face is formed.
[0053]
A smooth optical waveguide end face is formed by this dicing. A groove 19 is formed in the common substrate 11.
[0054]
When the optical waveguide coupler is formed by the above steps, and the optical fiber 23 is fixed to the V groove 13 of the optical waveguide coupler with an epoxy resin or the like, a structure having a cross section as shown in FIG. 5C is obtained. . Since the core 25 of the optical fiber and the end face of the optical waveguide are aligned by a pressing mold, the optical connection loss is reduced and the connection is good.
[0055]
If the optical waveguide coupler is formed by the above-described forming method, the optical waveguide layer is deposited with a uniform thickness on the common substrate and then pressed, so that the partial thickness of the optical waveguide layer on the substrate is reduced. The difference disappears. For this reason, it can be expected that the alignment accuracy between the optical fiber and the optical waveguide is further improved.
[0056]
Also in this forming method, the number of steps can be reduced as compared with the conventional method, and the processing in each step can be simplified. Further, since the positions of the optical fiber and the optical waveguide are also determined when setting the dimensions of the press mold, it is necessary to position each time and form a V-groove when forming the same optical waveguide coupler. Will disappear.
[0057]
In the optical waveguide coupler of this embodiment, preferably, the common substrate may be formed using crystallized glass or ceramic as a material. Further, the optical waveguide layer may be formed of glass having a refractive index higher than that of the common substrate. These common substrate and optical waveguide layer materials are suitable for press working.
[0058]
Alternatively, the common substrate may be formed using plastic as a material, and the optical waveguide layer may be formed using a material having a refractive index higher than that of the common substrate.
[0059]
The optical waveguide forming portion may be convex, and the concave or convex cross-sectional shape may be a triangle, a quadrangle, a trapezoid, or a semicircle.
[0060]
【The invention's effect】
As is clear from the above description, according to the optical waveguide coupler of the present invention, the common substrate, the V-groove formed in the common substrate, and the common substrate are formed so as to face one end of the V-groove. A convex or concave optical waveguide forming portion having an end portion and a channel type optical waveguide formed in the optical waveguide forming portion are provided.
[0061]
Since the V-groove for fixing the optical fiber to the common substrate and the optical waveguide forming portion are formed, the optical waveguide can be easily formed by providing an optical waveguide layer on the optical waveguide forming portion. it can. Further, only by fixing the optical fiber in the V groove of the optical waveguide coupler, the core end face of the optical fiber and the end face of the optical waveguide face each other and the optical axis is aligned. Therefore, the optical fiber can be easily mounted on the optical waveguide with high accuracy.
[0062]
Further, in forming this optical waveguide coupler, a step of forming a V-groove and an optical waveguide forming portion on a common substrate using press working, and a step of forming an optical waveguide layer-containing layer on the upper surface of the common substrate; And dicing at least the optical waveguide layer-containing layer at the boundary between the V groove and the optical waveguide forming portion to form the optical waveguide and the optical waveguide end face, and the V groove end face facing the optical waveguide end face. It is good to be out.
[0063]
By pressing, the V-groove and the optical waveguide forming portion for determining the positions of the optical fiber and the optical waveguide can be formed at a time on the common substrate. Next, after providing the optical waveguide layer-containing layer with a film thickness set by CVD or the like on this common substrate, a simple process of dicing the optical waveguide layer-containing layer at the boundary between the V groove and the optical waveguide forming portion Thus, the optical waveguide can be formed above the optical waveguide forming portion, and a smooth waveguide end face can be formed. Therefore, the number of steps can be reduced, and the optical waveguide coupler can be formed by simple processing. In addition, since the dimensions of the pressing mold are initially set, if pressing is performed using this mold, the position of the optical fiber and the optical waveguide will be different each time when forming the same optical waveguide coupler. There is no need to match. Therefore, the trouble of difficult alignment can be saved.
[0064]
For this reason, it is possible to form an optical waveguide coupler which can mount an optical fiber on the optical waveguide with high accuracy, and to easily form the optical waveguide coupler with a reduced number of processes. Therefore, the mass productivity can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of an optical waveguide coupler for explaining the first embodiment.
FIG. 2 is a plan view of an optical waveguide coupler as viewed from above for explaining the first embodiment, and is a schematic process diagram.
FIG. 3 is a schematic process cross-sectional view (No. 1) of the optical waveguide coupler for explaining the first embodiment;
FIG. 4 is a schematic process cross-sectional view (No. 2) of the optical waveguide coupler for explaining the first embodiment;
FIG. 5 is a schematic process cross-sectional view of the optical waveguide coupler corresponding to FIG. 3 for explaining the second embodiment;
[Explanation of symbols]
11: common substrate 13: V-groove 15: optical waveguide forming portions 15a, 15b: straight end portions of the optical waveguide forming portion 17: optical waveguide layer-containing layer 19: groove 21: optical waveguide, channel-type optical waveguide 21a: optical waveguide End face 23: Optical fiber 25: Core 25a: Core end face 31: Optical waveguide layer

Claims (6)

In forming the optical waveguide coupler for coupling the optical fiber and the end face of the optical waveguide,
Forming a V-groove for fixing the optical fiber on the common substrate and a convex or concave optical waveguide forming portion at the same time by the same pressing process;
Forming an optical waveguide layer-containing layer on an upper surface of the common substrate including the V-groove and the optical waveguide forming portion ;
The boundary between said V-groove the optical waveguide forming section, and forming at least by dicing the optical waveguide layer containing layer, and the optical waveguide and the optical waveguide end faces, the optical waveguide end face facing the V groove end surfaces only including,
In the step of forming the V-groove and the optical waveguide forming portion, the optical fiber and the end face of the optical waveguide are correctly coupled with the optical waveguide layer-containing layer formed on the V-groove by the press working. As described above, the method for forming an optical waveguide coupler is characterized in that the depth at which the V-groove is formed is adjusted . In the optical waveguide coupler formation method according to claim 1,
The common substrate is made of crystallized glass or ceramic, and the optical waveguide layer-containing layer is made of a clad layer made of SiO ₂ thin film and a material in which impurities are added to SiO ₂ , and has a refractive index of 3 or less than the clad layer. %. A method for forming an optical waveguide coupler, comprising: a multilayer film with an optical waveguide layer comprising a thin film having a high height. In the optical waveguide coupler formation method according to claim 1,
Optical waveguide coupler formation characterized in that the common substrate is crystallized glass or ceramic, and the optical waveguide layer-containing layer is an optical waveguide layer made of a polymer having a refractive index 3% higher than that of the common substrate. Method. In forming the optical waveguide coupler for coupling the optical fiber and the end face of the optical waveguide,
Forming an optical waveguide layer with a uniform film thickness on the upper surface of the common substrate;
Forming a V-groove and a convex or concave optical waveguide forming portion for fixing the optical fiber on the common substrate provided with the optical waveguide layer at the same time by the same pressing process;
The boundary between said V-groove the optical waveguide forming section, by dicing the at least optical waveguide layer, including said optical waveguide and the optical waveguide end face, and forming a the optical waveguide end face facing the V groove end surfaces See
In the step of forming the V-groove and the optical waveguide forming portion, the optical waveguide is formed on the convex upper portion or the concave bottom portion of the optical waveguide forming portion by the press working, and the V having the optical waveguide layer is formed. An optical waveguide coupler forming method characterized by being a step of forming a groove . In the optical waveguide coupler formation method according to claim 4,
An optical waveguide characterized in that the common substrate is formed of glass, crystallized glass, or ceramic, and the optical waveguide layer is formed of glass having a refractive index that is 3% higher than that of the common substrate. A coupler forming method. In the optical waveguide coupler formation method according to claim 4,
A method for forming an optical waveguide coupler, wherein the common substrate is formed using plastic as a material, and the optical waveguide layer is formed using a material having a refractive index that is 3% higher than the common substrate.

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