JP6871106B2 - Optical waveguide chip connection structure - Google Patents

Description

The present invention relates to a connection structure between optical waveguide chips used in technical fields that require processing of optical signals such as optical communication and optical sensing.

Industrial fields that use optical signal processing technologies such as optical communication and optical sensing continue to develop rapidly along with related fields. Similar to this optical signal processing technology, electronic circuit technology continues to develop rapidly, and at the same time, it is often used in combination with optical signal processing technology. However, compared to this electronic circuit technology, the optical signal processing technology has some drawbacks. It is a miniaturization and a simple connection.

In electronic circuit technology centered on silicon, miniaturization directly leads to higher performance due to the scaling law, so miniaturization has been promoted very actively. However, in the optical signal processing technology, the size of the system becomes very large in the spatial optical system. In addition, even in a planar lightwave circuit (PLC) that can realize a system smaller than a spatial optical system, even the size of the waveguide, which is the most basic optical element, is several μm to several hundred nm due to the cutoff conditions. It tends to be an order, and the device size tends to be large compared to electronic circuit technology.

Next, in terms of simple connection, in the case of electronic circuit technology, it is possible to transmit signals very easily by simply connecting a conductor such as metal in the low frequency region, and RF in the high frequency region as well. Pluggable connection technologies such as connectors are mature. However, in the case of optical signal processing technology, it is not possible to realize a good connection simply by connecting a medium for transmitting an optical signal. In order to obtain good connection in optical signal processing technology, high-precision alignment between devices is indispensable. For example, in the case of a device with a single-mode waveguide, the accuracy is on the order of sub μm, depending on the material and design. Alignment is required.

A method as described in Patent Document 1 has been proposed as a method for simultaneously realizing miniaturization and simple connection in an optical signal processing technique. With the structure disclosed in Patent Document 1, a pluggable connection in which an optical waveguide chip (quartz-based PLC) can be connected only when necessary, such as a connector, can be realized. The connection structure of such an optical waveguide chip is hereinafter referred to as PPPP (Pluggable Photonic Circuit Platform).

12 (A) to 12 (D) are schematic views showing a typical configuration of PPPP. 12 (A) is a perspective view of PPPP, FIG. 12 (B) is a component development view of PPPP, FIG. 12 (C) is a view showing a joint surface between a quartz PLC and a quartz flat plate, and FIG. 12 (D) is PPPP. Is a cross-sectional view taken along the xy plane. 12 (A) to 12 (D) show quartz-based PLC1001, 1002 and quartz-based PLC1001, which are two optical waveguide chips formed by a quartz-based glass layer including a Si substrate and a waveguide layer. A PPPP is constructed by combining a quartz flat plate 1003, which is a base substrate without a waveguide, which is produced by the same method as 1002, and four optical fibers for spacers 1006 (spacer members), for a total of seven points. ing.

The PPPP shown in FIGS. 12 (A) to 12 (D) is configured to transmit an input optical signal 1005 via a quartz-based PLC 1001 and a quartz-based PLC 1002 until it becomes an output optical signal 1004. There is. As shown in FIGS. 12 (A) and 12 (B), the quartz-based PLC1001 and the quartz-based PLC1002 are arranged side by side so that their respective inlet / output end faces 11 and 12 face each other, and the two quartzs are arranged side by side. The system PLCs 1001 and 1002 are loaded on the quartz flat plate 1003.

As shown in FIG. 12D, the quartz-based PLC1001 has a structure in which an optical waveguide layer 1008 is formed on a Si substrate 1009. The optical waveguide layer 1008 is _{composed of a clad layer 1010 made of SiO 2} and a core 1011 formed in the clad layer 1010. Further, a fitting groove 1007 is formed in the clad layer 1010. The structure of the quartz-based PLC1002 is also the same as that of the quartz-based PLC1001.

On the Si substrate 1012 of the quartz-based flat plate 1003, a glass layer 1013 made of the same material as the clad layer 1010 of the quartz-based PLC 1001, 1002 is formed on the surface on which the quartz-based PLCs 1001 and 1002 are loaded. In the glass layer 1013, a fitting groove 1014 is formed at a position facing the fitting groove 1007 of the quartz-based PLCs 1001 and 1002 when the quartz-based PLCs 1001 and 1002 are loaded on the quartz-based flat plate 1003.

As shown in FIGS. 12B and 12C, the quartz-based PLC1001 and 1002 are fitted into the fitting groove 1014 on the quartz-based flat plate 1003 side and the fitting groove 1007 on the quartz-based PLC1001, 1002 side. It is fixed to the quartz flat plate 1003 via the matching optical fiber 1006 for spacers.
With the above structure, it is possible to realize passive alignment mounting that aligns quartz-based PLCs 1001 and 1002 only with mechanical accuracy of members, etc., and while realizing simple connection with accuracy in sub μm units, optical Miniaturization is also realized by enabling the integration of waveguides.

In the quartz-based PLC and quartz-based flat plate having a Si substrate used in the PPPP shown in FIGS. 12 (A) to 12 (D), it is often caused by the difference in the coefficient of thermal expansion between _{Si and SiO 2.} Stress is generated and warpage occurs. Such warpage may be a problem even in normal PLC applications, but it is especially problematic in the case of PPPP, which is premised on passive alignment mounting, and in many cases, the optical connection between PLCs is displaced. , Will result in an increase in insertion loss. Further, PPPP can be used for integrating an optical waveguide having a multi-layer structure, and at that time, PLC may be polished to be thinned. There is a problem that the warp tends to be larger than that of a PLC having a normal thickness due to this polishing.

Therefore, thinning and passive alignment, which are the characteristics of PPPP to realize miniaturization and easy connection, are affected by warpage due to the difference in the coefficient of thermal expansion of the material, and excessive insertion loss occurs. Will have the problem

JP-A-2017-32950

The present invention has been made in view of the above problems, and the purpose of the present invention is to alleviate warpage caused by physical property values and increase optical connection loss while maintaining a highly accurate and simple mounting method. It is an object of the present invention to provide the connection structure of the optical waveguide chip which can suppress the above.

The connection structure of the optical waveguide chip of the present invention includes a base substrate in which a plurality of first grooves having a rectangular cross section are formed in a first clad layer on the first substrate, and a part thereof protrudes from the base substrate. A plurality of spacer members that are fitted to the plurality of first grooves in shape, and a first optical waveguide is formed in a second clad layer on a second substrate, and faces the first groove. A second groove having a rectangular cross section is formed on the surface of the second clad layer to be fitted with the protruding portion of the spacer member, and is loaded on the base substrate in a form supported by the spacer member. A plurality of first optical waveguide chips are provided, and the plurality of first optical waveguide chips are arranged along a direction perpendicular to the loading direction of the base substrate and the first optical waveguide chip. The two adjacent first optical waveguide chips are loaded on the base substrate so that the entrance / exit end faces of the first optical waveguide face each other, and the base substrate is the first substrate and the first clad layer. The plurality of first optical waveguide chips are composed of three or more layers including, and have a structure in which the thermal expansion coefficient of the inner layer takes an extreme value with respect to the thermal expansion coefficient of the outer layer in the stacking direction. Consists of three or more layers including the second substrate and the second clad layer, and the thermal expansion coefficient of the inner layer takes an extreme value with respect to the thermal expansion coefficient of the outer layer in the stacking direction. It is characterized by having a structure.
Further, in one configuration example of the connection structure of the optical waveguide chip of the present invention, the base substrate is a second optical waveguide chip in which a second optical waveguide is formed in the first clad layer. It is something to do.

Further, the connection structure of the optical waveguide chip of the present invention includes a base substrate in which a plurality of first grooves having a rectangular cross section are formed, and the plurality of first grooves in a form in which a part thereof protrudes from the base substrate. A second groove having a rectangular cross section, which is formed with a plurality of spacer members to be fitted to each other and a first optical waveguide, and is fitted to a protruding portion of the spacer member on a surface facing the first groove. The plurality of first optical waveguide chips are formed and supported on the base substrate in a form supported by the spacer member, and the plurality of first optical waveguide chips are the base substrate and the first optical waveguide chip. It is arranged along a direction perpendicular to the loading direction with the optical waveguide chip of 1, and is placed on the base substrate so that the entrance / exit end faces of the first optical waveguide of two adjacent first optical waveguide chips face each other. stacked on the base substrate, provided on the first substrate and the first substrate, three layers or more including a first cladding layer, wherein the first grooves are formed, these thermal expansion coefficient of the inner layer with respect to the thermal expansion coefficient of the outer layer in the stacking direction has a structure Ru preparative extremes, each of the plurality of first optical waveguide chip comprises a second substrate It is composed of three or more layers including the first optical waveguide and the second clad layer on which the second groove is formed provided on the second substrate, and the outer layer in the stacking direction thereof. it is characterized in that the thermal expansion coefficient of the inner layer has a structure Ru preparative extreme relative thermal expansion coefficients.

Further, in one configuration example of the connection structure of the optical waveguide chip of the present invention, the base substrate is a second optical waveguide chip in which a second optical waveguide is formed on the first substrate or the first clad layer. It is characterized by being .

According to the present invention, a base substrate in which a first groove is formed on the first substrate, a spacer member that is partially projected from the base substrate and fitted to the first groove, and a first groove. Passive alignment that aligns only with mechanical accuracy by providing a plurality of first optical waveguide chips in which a second groove to be fitted with a protruding portion of the spacer member is formed on the surface of the second substrate facing each other. It is possible to realize high-precision and simple multi-chip mounting by mounting, and it is also possible to realize miniaturization of an optical circuit by enabling integration of optical waveguide chips. Further, in the present invention, the base substrate and the first optical waveguide chip have a one-layer structure consisting of only the first and second substrates, respectively, which is caused by the warp of the base substrate and the first optical waveguide chip. It is possible to suppress an increase in loss of optical connection due to widening of the gap between the first optical waveguide chips. Further, in the present invention, if, for example, a material system similar to a quartz-based PLC is adopted as the first and second substrates, the advanced technology cultivated in the quartz-based PLC up to now can be applied to the connection structure of the optical waveguide chip. While being applied, it is possible to alleviate the warp characteristics of ordinary quartz PLCs.

Further, in the present invention, the base substrate in which the first groove is formed in the first clad layer on the first substrate and the spacer member which is partially projected from the base substrate and fitted to the first groove. And by providing a first optical waveguide chip in which a second groove that fits with the protruding portion of the spacer member is formed on the surface of the second clad layer facing the first groove, only mechanical accuracy is provided. It is possible to realize highly accurate and simple multi-chip mounting by passive alignment mounting that aligns with, and it is also possible to realize miniaturization of the optical circuit by enabling the integration of optical waveguide chips. Further, in the present invention, the base substrate has a two-layer structure in which each of the first substrate and the first clad layer is made of a compound semiconductor, and the first optical waveguide chip is a second substrate and a second clad layer. By adopting a two-layer structure in which each of the above is made of a compound semiconductor, it is possible to suppress an increase in optical connection loss due to the widening of the gap between the base substrate and the first optical waveguide chip due to the warp of the first optical waveguide chip. Can be done.

Further, in the present invention, the base substrate is composed of three or more layers including the first substrate and the first clad layer, and the thermal expansion of the inner layer with respect to the coefficient of thermal expansion of the outer layer in the laminating direction of these. The structure has a structure in which the coefficient takes an extreme value, and the first optical waveguide chip is composed of three or more layers including a second substrate and a second clad layer, with respect to the coefficient of thermal expansion of the outer layer in the stacking direction. By adopting a structure in which the coefficient of thermal expansion of the inner layer takes an extreme value, the loss of optical connection due to the widening of the gap between the base substrate and the first optical waveguide chip due to the warp of the first optical waveguide chip is lost. The increase can be suppressed. Further, in the present invention, if each of the base substrate and the first optical waveguide chip has a three-layer structure of quartz-based glass, silicon, and quartz-based glass, the advanced technology cultivated in quartz-based PLC up to now can be used. While being applied to the connection structure of an optical waveguide chip, it is possible to relax the warp characteristics of ordinary quartz-based PLCs.

FIG. 1 is a schematic view showing a connection structure of an optical waveguide chip according to a first embodiment of the present invention. FIG. 2 is a schematic view showing a connection structure of an optical waveguide chip according to a second embodiment of the present invention. FIG. 3 is a diagram showing the coefficient of thermal expansion of the material constituting the optical waveguide chip according to the second embodiment of the present invention. FIG. 4 is a schematic view showing a connection structure of an optical waveguide chip according to a third embodiment of the present invention. FIG. 5 is a diagram showing the coefficient of thermal expansion of the material constituting the optical waveguide chip according to the third embodiment of the present invention. FIG. 6 is a schematic view showing another connection structure of the optical waveguide chip according to the first embodiment of the present invention. FIG. 7 is a schematic view showing another connection structure of the optical waveguide chip according to the second embodiment of the present invention. FIG. 8 is a schematic view showing another connection structure of the optical waveguide chip according to the third embodiment of the present invention. FIG. 9 is a cross-sectional view showing a connection structure of the optical waveguide chip according to the fourth embodiment of the present invention. FIG. 10 is a cross-sectional view showing another connection structure of the optical waveguide chip according to the fourth embodiment of the present invention. FIG. 11 is a perspective view showing a connection structure of the optical waveguide chip according to the fifth embodiment of the present invention. FIG. 12 is a schematic view showing a connection structure of a conventional optical waveguide chip.

[First Example]
Hereinafter, examples of the present invention will be described with reference to the drawings. 1 (A) to 1 (D) are schematic views showing the configuration of PPPP according to the first embodiment of the present invention. 1 (A) is a perspective view of PPPP, FIG. 1 (B) is a component development view of PPPP, FIG. 1 (C) is a view showing a joint surface between an upper layer PLC and a lower layer PLC, and FIG. 1 (D) is a view showing a joint surface of PPPP. Is a cross-sectional view taken along the xy plane. In FIGS. 1A to 1D, PLC101 and 102, which are two optical waveguide chips composed of only one quartz glass layer having an ion exchange type optical waveguide, and PLC103, which is a similar optical waveguide chip, are shown. A PPPP is formed by combining a total of seven members of four spacer optical fibers 108 (spacer members).

As shown in FIG. 1A, the input optical signal 105 incident on the PLC 102 propagates through the optical waveguide of the PLC 102, exits the PLC 102, enters the PLC 101, propagates through the optical wave guide of the PLC 101, and propagates the output optical signal 104. And exits from the PLC 101. Further, the input light signal 107 incident on the PLC 103 propagates through the optical waveguide of the PLC 103, becomes an output light signal 106, and is emitted from the PLC 103.

As shown in FIG. 1 (D), the PLC 101 is an optical waveguide (core) for transmitting an input optical signal 105 to the surface of a quartz glass plate 109 (second substrate) which is a support substrate and a clad layer. ) 110 has a structure formed by an ion exchange method. Further, a fitting groove 111 is formed on the surface of the quartz glass plate 109. The structure of the PLC 102 is the same as that of the PLC 101. FIG. 1C shows the joint surfaces of the quartz glass plates 109 of the PLCs 101 and 102 with the PLC 103. According to FIG. 1C, it can be seen that two fitting grooves 111 are formed in each of the PLCs 101 and 102.

As shown in FIGS. 1 (A) and 1 (B), the PLC 101 and the PLC 102 are arranged side by side along the direction perpendicular to the loading direction of the PLC 103, and the respective inlet / outlet end faces 11, The 12s are loaded on the PLC 103 so as to face each other.

Similar to the PLCs 101 and 102, the PLC 103 has an optical waveguide (core) 113 for transmitting an input optical signal 107 on the surface of a quartz glass plate 112 (first substrate) which is a support substrate and a clad layer. It has a structure formed by an ion exchange method. On the surface of the quartz glass plate 112, a fitting groove 114 having the same shape as the fitting groove 111 is formed at a position facing the fitting groove 111 of the PLC 101, 102 when the PLC 101, 102 is loaded on the PLC 103. ing.

FIG. 1C shows the joint surface of the quartz glass plate 112 with the PLCs 101 and 102. Since two fitting grooves 111 are formed in each of the PLCs 101 and 102 as described above, the two fitting grooves 111 formed in the positions facing the fitting grooves 111 of the PLC 101 and the fitting grooves 111 of the PLC 102 are formed in the positions facing each other. A total of four fitting grooves 114 are formed in the quartz glass plate 112. In this embodiment, the longitudinal directions of the fitting grooves 111 and 114 are the z-axis directions (the optical axis direction of the light emitted from the PLC 102 to the PLC 101 and the optical axis direction of the light incident on the PLC 103, and FIGS. It was made parallel to 1 (C) in the left-right direction).

Examples of the optical waveguides (cores) 110 and 113 include, for example, Ag ⁺ ion exchange waveguide and K ⁺ ion exchange waveguide, but the materials are not limited to these.

In order to produce the PPPP of this embodiment, the spacer optical fibers 108 are fitted one by one into the four fitting grooves 114 formed in the quartz glass plate 112 of the PLC 103. Then, as shown in FIG. 1 (B), the joint surface of the quartz glass plate 112 and the joint surface of the quartz glass plate 109 of the PLC 101 are fitted into the fitting groove 114 of the quartz glass plate 112 so as to face each other. The two spacer optical fibers 108 and the two fitting grooves 111 formed in the quartz glass plate 109 of the PLC 101 are fitted, and the PLC 101 is loaded on the PLC 103.

Similarly, for two spacers fitted in the fitting groove 114 of the quartz glass plate 112 so that the joint surface of the quartz glass plate 112 of the PLC 103 and the joint surface of the quartz glass plate 109 of the PLC 102 face each other. The optical fiber 108 and the two fitting grooves 111 formed in the quartz glass plate 109 of the PLC 102 are fitted, and the PLC 102 is loaded on the PLC 103.

In this way, the PLCs 101 and 102 can be loaded on the PLC 103 so that the entrance / exit end faces 11 of the PLC 101 and the entrance / exit end faces 12 of the PLC 102 face each other at a close distance, and the optical connection between the PLC 101 and the PLC 102 can be realized.

The fitting grooves 111 and 114 are formed by photolithography. Therefore, the width (dimensions in the left-right direction of FIG. 1 (D)) and length (dimensions of FIGS. 1 (B) and 1 (C) in the left-right direction) and positions of the fitting grooves 111 and 114 are extremely accurate. Can be decided with. As a result, the axial deviation of the optical waveguide 110 in the in-plane direction of the substrate can be positioned with extremely high accuracy.

Further, the spacer optical fibers 108 having the same diameter are fitted into the four fitting grooves 114 on the PLC 103 side, and the fitting grooves 111 on the PLC 101 side are fitted into two of the four spacer optical fibers 108. Since the fitting groove 111 on the PLC102 side is fitted into the remaining two spacer optical fibers 108, the inclination of the PLCs 101 and 102 with respect to the PLC 103 can be made negligibly small.

By adopting the above PPPP structure, the core positions of the two PLCs 101 and 102 with respect to the PLC 103 are determined with high accuracy. When the PLCs 101 and 102 are loaded on the PLC 103, the positions of the optical waveguides 110 of the two PLCs 101 and 102 are positioned on the same straight line, so that a low-loss connection of light can be realized. In this way, in this embodiment, it is possible to realize a simple multi-chip mounting with accuracy at the sub μm level by passive alignment mounting without inputting and outputting light, and by enabling the integration of PLCs 101 and 102, the light can be integrated. It is also possible to reduce the size of the circuit.

Further, in this embodiment, by realizing each of the PLCs 101 to 103 with only one quartz glass layer, it is possible to prevent the warpage of the PLCs 101 to 103, and the PLCs 101 and 102 due to the warpage of the PLCs 101 to 103 can be prevented from occurring. It is possible to suppress an increase in the loss of optical connection due to the widening of the gap between them.

[Second Example]
Next, a second embodiment of the present invention will be described. 2 (A) to 2 (D) are schematic views showing the configuration of a PLCP according to a second embodiment of the present invention, FIG. 2 (A) is a perspective view of the PLCP, and FIG. 2 (B) is a PPPP. 2 (C) is a view showing a joint surface between the PLC of the upper layer and the PLC of the lower layer, and FIG. 2 (D) is a cross-sectional view of the PPPP cut along the xy plane. In FIGS. 2A to 2D, PLC201 and 202, which are two optical waveguide chips each having an AlGaAs-based waveguide, PLC203, which is a similar optical waveguide chip, and optical fiber 208 for four spacers, respectively. A PPPP is formed by combining a total of seven members (spacer members).

_{In the PLC201, as shown in FIG. 2D, a clad layer 210 made of Al 0.3} Ga _0.7 As is formed on the surface of the support substrate 209 (second substrate) made of GaAs, and GaAs is further formed on the surface of the clad layer 210. It has a structure in which an optical waveguide (core) 211 made of the above is formed. As described above, the optical waveguide 211 has a strip waveguide structure. Further, a fitting groove 212 is formed on the surface of the clad layer 210. The structure of PLC202 is also the same as that of PLC201. In this embodiment, two fitting grooves 212 are formed in each of the PLCs 201 and 202.

_{Similar to PLC201 and 202, in PLC203, a clad layer 214 made of Al 0.3} Ga _0.7 As is formed on the surface of a support substrate 213 (first substrate) made of GaAs, and an optical wave made of GaAs is further formed on the surface of the clad layer 214. It has a structure in which a waveguide (core) 215 is formed. Further, on the surface of the clad layer 214, a fitting groove 216 having the same shape as the fitting groove 212 is formed at a position facing the fitting groove 212 of the PLC 201 and 202 when the PLC 201 and 202 are loaded on the PLC 203. ing.

As shown in FIG. 2A, the input light signal 205 incident on the PLC 202 propagates through the optical waveguide 211 of the PLC 202, exits the PLC 202, enters the PLC 201, propagates through the optical wave guide 211 of the PLC 201, and outputs light. The signal 204 is emitted from the PLC 201. Further, the input light signal 207 incident on the PLC 203 propagates through the optical waveguide 215 of the PLC 203, becomes an output light signal 206, and is emitted from the PLC 203.

In order to produce the PPPP of this embodiment, the spacer optical fibers 208 are fitted one by one into the four fitting grooves 216 formed in the clad layer 214 of the PLC 203. Then, the two spacer optical fibers 208 fitted in the fitting groove 216 of the clad layer 214 and the clad layer 210 of the PLC 201 are fitted so that the joint surface of the clad layer 214 and the joint surface of the clad layer 210 of the PLC 201 face each other. The two fitting grooves 212 formed in the above are fitted together, and the PLC 201 is loaded on the PLC 203.

Similarly, the two spacer optical fibers 208 and the PLC 202 fitted into the fitting groove 216 of the clad layer 214 so that the joint surface of the clad layer 214 of the PLC 203 and the joint surface of the clad layer 210 of the PLC 202 face each other. The two fitting grooves 212 formed in the clad layer 210 are fitted together, and the PLC 202 is loaded on the PLC 203.

In this way, the PLCs 201 and 202 can be loaded on the PLC 203 so that the entrance / exit end faces 21 of the PLC 201 and the entry / exit end faces 22 of the PLC 202 face each other at a close distance, and the accuracy in units of sub μm described in the first embodiment can be obtained. It is possible to realize a simple optical connection and miniaturization of the optical circuit.

Further, as shown in FIG. 3, the coefficient of thermal expansion of GaAs constituting the support substrates 209 and 213 is 5.73 × 10 ^-6 _{/ K, and the coefficient of thermal expansion of Al 0.3} Ga _0.7 As constituting the clad layers 210 and 214 is The coefficient is 5.57 × 10 ^-6 / K. Therefore, the difference in the specific heat expansion coefficient obtained by subtracting the minimum coefficient of thermal expansion from the maximum coefficient of thermal expansion of the substances constituting PLC201-203 and dividing by the maximum coefficient of thermal expansion is (5.73-5.57) / 5. 73 = 0.028.

In the case of quartz-based PLC, which is suitable as an application destination of PPPP and is also very often used in current PLC applications, the coefficient of thermal expansion of Si is 2.6 × 10 ^-6 / K, and the thermal expansion of _{SiO 2} Since the coefficient is 0.5 × 10 ^-6 / K, the difference in the coefficient of specific thermal expansion in this system is (2.6-0.5) /2.6 = 0.81.

In this embodiment, although it is widely used as an optical circuit, it is made of an AlGaAs-based material having a smaller specific heat expansion coefficient difference without using a quartz-based PLC made of a material having a large specific heat expansion coefficient difference. By adopting the two-layer structure for PLCs 201 to 203, it is possible to reduce the warpage of PLCs 201 to 203, which causes an increase in insertion loss in PPPP.

Generally, for compound semiconductor material systems represented by AlGaAs material systems, mature techniques for forming optical waveguides have been put into practical use. When each of the PLCs 201 to 203 is formed with a structure of a plurality of layers, the difference in the specific thermal expansion coefficient between the layers can be made smaller than that of the quartz PLC, so that a good PPPP connection can be easily achieved.

[Third Example]
Next, a third embodiment of the present invention will be described. 4 (A) to 4 (D) are schematic views showing the configuration of a PLCP according to a third embodiment of the present invention, FIG. 4 (A) is a perspective view of the PLCP, and FIG. 4 (B) is a PPPP. 4 (C) is a view showing a joint surface between the PLC of the upper layer and the PLC of the lower layer, and FIG. 4 (D) is a cross-sectional view of the PPPP cut along the xy plane. 4 (A) to 4 (D) show PLC301 and 302, which are two optical waveguide chips having Si-based waveguides, PLC303, which is a similar optical waveguide chip, and optical fiber 308 for four spacers. A PPPP is formed by combining a total of seven members (spacer members).

_{In the PLC301, as shown in FIG. 4D, a clad layer 310 made of SiO 2} is formed on the surface of a support substrate 309 (second substrate) made of Si, and the support substrate 309 on the opposite side of the clad layer 310 is formed. SiO ₂ layer 311 is formed on the surface, and has a light guide (core) 312 made of SiO ₂ and Ge doped in the cladding layer 310 are formed structure. Further, a fitting groove 313 is formed on the surface of the clad layer 310. The structure of the PLC 302 is the same as that of the PLC 301. In this embodiment, two fitting grooves 313 are formed in each of the PLCs 301 and 302.

_{Similar to PLC301 and 302, in PLC303, a clad layer 315 made of SiO 2} is formed on the surface of a support substrate 314 made of Si (first substrate), and SiO is formed on the surface of the support substrate 314 opposite to the clad layer 315. _The structure is such that two layers 316 are formed, and an optical waveguide (core) 317 made _{of Ge-doped SiO 2 is formed in the clad layer 315.} Further, on the surface of the clad layer 315, a fitting groove 318 having the same shape as the fitting groove 313 is formed at a position facing the fitting groove 313 of the PLC 301 and 302 when the PLC 301 and 302 are loaded on the PLC 303. ing.

As shown in FIG. 4A, the input light signal 305 incident on the PLC 302 propagates through the optical waveguide 312 of the PLC 302, exits the PLC 302, enters the PLC 301, propagates through the optical wave guide 312 of the PLC 301, and outputs light. It becomes a signal 304 and exits from the PLC 301. Further, the input light signal 307 incident on the PLC 303 propagates through the optical waveguide 317 of the PLC 303, becomes an output light signal 306, and is emitted from the PLC 303.

In order to produce the PPPP of the present embodiment, the spacer optical fibers 308 are fitted one by one into the four fitting grooves 318 formed in the clad layer 315 of the PLC 303. Then, the two spacer optical fibers 308 fitted in the fitting groove 318 of the clad layer 315 and the clad layer 310 of the PLC 301 are fitted so that the joint surface of the clad layer 315 and the joint surface of the clad layer 310 of the PLC 301 face each other. The two fitting grooves 313 formed in the above are fitted together, and the PLC 301 is loaded on the PLC 303.

Similarly, the two spacer optical fibers 308 and PLC 302 fitted into the fitting groove 318 of the clad layer 315 so that the joint surface of the clad layer 315 of the PLC 303 and the joint surface of the clad layer 310 of the PLC 302 face each other. The two fitting grooves 313 formed in the clad layer 310 are fitted together, and the PLC 302 is loaded on the PLC 303.

In this way, the PLCs 301 and 202 can be loaded on the PLC 303 so that the entrance / exit end faces 31 of the PLC 301 and the entry / exit end faces 32 of the PLC 302 face each other at a close distance, and the accuracy in units of sub μm described in the first embodiment can be obtained. It is possible to realize a simple optical connection and miniaturization of the optical circuit.

Further, as shown in FIG. 5, the coefficient of thermal expansion of Si constituting the support substrates 309 and 314 is 2.6 × 10 ^-6 / K, and the coefficient of thermal expansion of the clad layers 310 and 315 and the SiO ₂ layers 311, 316 is Is 0.5 × 10 ^-6 / K. Therefore, in each of the PLCs 301 to 303, the change in the coefficient of thermal expansion along the stacking direction has a large coefficient of thermal expansion of the inner layer (support substrate 309, 314) and the outer layer (clad layers 310, 315 and SiO _2). Layers 311, 316) have a small coefficient of thermal expansion. That is, the coefficient of thermal expansion does not decrease monotonically or increase monotonically along the stacking direction.

Therefore, in this embodiment, in each of the PLCs 301 to 303, the stresses generated by the difference in the coefficient of thermal expansion between the inner layer and the layers above and below the inner layer are generated symmetrically with respect to the inner layer, so that the stresses generated symmetrically cancel each other out. Will be in conflict. As described above, in this embodiment, by adopting PLC301 to 303 having a structure in which the coefficient of thermal expansion of the inner layer takes an extreme value with respect to the coefficient of thermal expansion of the outer layer in the stacking direction, the insertion loss in PPPP It is possible to reduce the warp of PLC 301 to 303, which causes an increase in the coefficient.

In this embodiment, each of the PLCs 301 to 303 has a three-layer structure, but four or more layers may be used. Further, in this embodiment, an example in which the coefficient of thermal expansion of the inner layer has the maximum value with respect to the outer layer is shown in each of the PLCs 301 to 303, but the thermal expansion of the inner layer with respect to the outer layer is shown. The structure may have a minimum coefficient.

In the first to third embodiments, the lower base substrates on which the PLCs 101, 102, 201, 202, 301, and 302 are loaded are also PCL103, 203, 303 having the same structure as these PLCs. Not limited. In the present invention, it is sufficient that the warp of the lower base substrate can be suppressed as in the case of the upper PLC. Therefore, the base substrate has a structure without optical waveguides 113, 215 and 317 (quartz glass plate 112, clad layer 214, clad). A structure in which the optical waveguides 113, 215, and 317 are not formed on the layer 315) may be used.

FIG. 6 shows an example of PPPP using the base substrate 103a having a structure in which the optical waveguide 113 is not formed on the quartz glass plate 112 in the first embodiment.
FIG. 7 shows an example of PPPP using the base substrate 203a having a structure in which the optical waveguide 215 is not formed on the clad layer 214 in the second embodiment.
FIG. 8 shows an example of PPPP using the base substrate 303a having a structure in which the optical waveguide 317 is not formed on the clad layer 315 in the third embodiment.

[Fourth Example]
Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the lower base substrate and the upper PLC have the same type of structure, but the base substrate and the PLC may have different types of structures. Specifically, the first to third embodiments may be combined as appropriate.

For example, FIG. 9 shows an example of PPPP in which the PLC201 described in the second embodiment is loaded on the PLC103 described in the first embodiment. In order to produce such a PPPP, the joint surface of the quartz glass plate 112 of the PLC 103 and the joint surface of the clad layer 210 of the PLC 201 are fitted into the fitting groove 114 of the quartz glass plate 112 so as to face each other. The two spacer optical fibers 108 and the two fitting grooves 212 formed in the clad layer 210 of the PLC 201 may be fitted, and the PLC 201 may be loaded on the PLC 103. In FIG. 9, only the PLC 201 is loaded, but it goes without saying that the PLC 202 is also loaded on the PLC 103 as in the first and second embodiments. Further, instead of the PLC 103, the base substrate 103a described with reference to FIG. 6 may be used.

Further, FIG. 10 shows an example of PPPP in which the PLC301 described in the third embodiment is loaded on the PLC203 described in the second embodiment. In order to produce such a PPPP, two spacers fitted in the fitting groove 216 of the clad layer 214 so that the joint surface of the clad layer 214 of the PLC 203 and the joint surface of the clad layer 310 of the PLC 301 face each other. The optical fiber 208 and the two fitting grooves 313 formed in the clad layer 310 of the PLC 301 may be fitted, and the PLC 301 may be loaded on the PLC 203. In FIG. 10, only the PLC 301 is loaded, but it goes without saying that the PLC 302 is also loaded on the PLC 203 as in the second and third embodiments. Further, instead of the PLC 203, the base substrate 203a described with reference to FIG. 7 may be used.

Further, the PLCs 301 and 302 described in the third embodiment are placed on the PLC 103 described in the first embodiment or on the base substrate 103a having a structure in which the optical waveguide 113 is not formed on the quartz glass plate 112. It may be loaded.

Further, the PLCs 101 and 102 described in the first embodiment are loaded on the PLC 203 described in the second embodiment or on the base substrate 203a having a structure in which the optical waveguide 215 is not formed in the clad layer 214. You may.

Further, on the PLC 303 described in the third embodiment, or on the base substrate 303a having a structure in which the optical waveguide 317 is not formed in the clad layer 315, the PLC 101, 102, or the first The PLCs 201 and 202 described in the second embodiment may be loaded.

[Fifth Example]
In the first to fourth embodiments, the case where the plurality of PLCs in the upper layer are of the same type is described, but the plurality of PLCs in the upper layer may be of different types. Further, in the first to fourth embodiments, the case where the lower layer PLC or the base substrate is one is described, but the lower layer may be a plurality of PLCs of the same type, and the plurality of lower layer PLCs may be of different types. There may be. FIG. 11 is a perspective view showing the configuration of PPPP according to the fifth embodiment of the present invention.

In FIG. 11, 120 is a PLC having the same structure as the PLC 103 of the first embodiment, 121 is a PLC having the same structure as the PLCs 101 and 102 of the first embodiment, and 220 is a PLC 201 and 202 of the second embodiment. The PLC and 320 having the same structure as the PLC of the third embodiment are the PLCs having the same structure as the PLC 303 of the third embodiment, and 321 is the PLC having the same structure as the PLCs 301 and 302 of the third embodiment.

In the example of FIG. 11, three PLCs 121, 220, 321 are mounted on two PLCs 120 and 320 by the PPPP technique described in the first to fourth embodiments. The two adjacent PLCs 120 and 320 are arranged so that the entrance / exit end faces of the optical waveguides (corresponding to the optical waveguides 113 and 317) face each other. Further, the two adjacent PLCs 121 and 220 are loaded on the PLCs 120 and 320 so that the entrance and exit end faces of the optical waveguides (corresponding to the optical waveguides 110 and 211) face each other. Similarly, two adjacent PLCs 220 and 321 are loaded on the PLCs 120 and 320 so that the entrance and exit end faces of the optical waveguides (corresponding to the optical waveguides 211 and 312) face each other.

As shown in FIG. 11, the input optical signal 405 incident on the PLC 121 propagates through the optical waveguide (optical waveguide 110) of the PLC 121, exits the PLC 121, enters the PLC 220, and propagates through the optical wave guide (optical waveguide 211) of the PLC 220. Then, the PLC 220 is emitted, is incident on the PLC 321 and propagates through the optical wave guide (optical wave guide 312) of the PLC 321 to become an output optical signal 404 and is emitted from the PLC 321. Further, the input optical signal 407 incident on the PLC 320 propagates through the optical waveguide (optical waveguide 317) of the PLC 320, exits the PLC 320, enters the PLC 120, propagates through the optical wave guide (optical wave guide 113) of the PLC 120, and outputs light. It becomes a signal 406 and exits from the PLC 120.

The upper layer PLC has a PLC having the same structure as the PLCs 101 and 102 of the first embodiment, a PLC having the same structure as the PLCs 201 and 202 of the second embodiment, and a PLC having the same structure as the PLCs 301 and 302 of the third embodiment. It may be any of the PLCs of.
Similarly, the lower layer PLC is a PLC having the same structure as the PLC 103 of the first embodiment, a PLC having the same structure as the PLC 203 of the second embodiment, and a PLC having the same structure as the PLC 303 of the third embodiment. Either one may be used.

Further, the lower layer is one PLC having the same structure as the PLC 103, one base substrate having the same structure as the substrate 103a, one PLC having the same structure as the PLC 203, and one one having the same structure as the substrate 203a. It may be either a base substrate, one PLC having the same structure as the PLC 303, or one base substrate having the same structure as the substrate 303a.

When the lower layer has a plurality of PLCs, it is preferable that the connection position between the lower layer PLCs is deviated from the connection position between the upper layer PLCs.
Further, in the example of FIG. 11, since the lower layer is composed of a plurality of PLCs, the PPPP may be placed on another base that supports the plurality of PLCs.

In the present invention, there is no particular limitation on how the input optical signal for PPPP is input or how the output optical signal is output. That is, in the case of an input optical signal, an input by a spatial optical system, an input by an optical fiber via optical fiber block bonding, a laser diode arranged on or inside the PLC without an optical signal input surface on the end face of the PLC, etc. Any input method such as input from the light emitting element / modulation element of the above may be used. Further, in the case of an output optical signal, an output by a spatial optical system, an output by an optical fiber via optical fiber block bonding, a photodiode having no optical signal output surface on the end face of the PLC, and a photodiode arranged on or inside the PLC, etc. Any output method such as output to the light receiving element may be used.

Further, in the present invention, what kind of optical circuit the PLC constituting the PPPP has is not particularly limited. The optical circuit shown in the first to fifth embodiments is only a simple linear optical waveguide, but it is merely an example, and the present invention can be applied to an optical circuit other than the linear optical waveguide. That is, the PPPP technology and the present invention are independent of the type and configuration of the optical circuit.

Further, in the first to fifth embodiments, all the optical fibers for spacers are used as members for joining the PLC or the base substrate, but if they are properly fitted to the grooves, they can be used as spacer members for spacers. Materials and shapes other than optical fibers may be used. Specifically, as the material of the spacer member, a metal, a ceramic, a polymer, or the like can be arbitrarily used in addition to glass. Further, as the shape of the spacer member, a spherical shape, a trapezoidal shape, a polygonal columnar shape, an elliptical spherical shape, or the like can be arbitrarily adopted in addition to the cylindrical shape.

In the first to fifth embodiments, the number of fitting grooves 111, 114, 212, 216, 313, 318 may be two or more per PLC (or one base substrate). The number of spacer optical fibers 108, 208, 308 may be as many as the number corresponding to the fitting grooves 111, 114, 212, 216, 313, 318.

Further, in the first to fifth embodiments, the heights of the spacer optical fibers 108, 208, 308 are the sum of the depths of the upper and lower fitting grooves into which the spacer optical fibers 108, 208, 308 are fitted. Higher than is desirable.

The present invention can be applied to a technique for connecting optical waveguide chips to each other.

11, 12, 21, 22, 31, 32 ... Input / exit end faces, 101-103, 120, 121
, 201-203, 220, 301-303, 320, 321 ... PLC, 103a, 203a ... Base substrate, 104, 106, 204, 206, 304, 306, 404, 406 ... Output optical signal, 105, 107, 205, 207, 305, 307, 405, 407 ... Input optical signal, 108, 208, 308 ... Spacer optical fiber, 109, 112 ... Quartz glass plate, 110, 113, 211, 215, 312, 317 ... Optical waveguide, 111 , 114,212,216,313,318 ... Fitting groove, 209,213,309,314 ... Support substrate, 210,214,310,315 ... Clad layer, 311,316 ... SiO ₂ layer.

Claims (4)

A base substrate in which a plurality of first grooves having a rectangular cross section are formed in a first clad layer on the first substrate, and a base substrate.
A plurality of spacer members, each of which is fitted with the plurality of first grooves in a form in which a part thereof protrudes from the base substrate.
A first optical waveguide is formed in the second clad layer on the second substrate, and the surface of the second clad layer facing the first groove is fitted with a protruding portion of the spacer member. A second groove having a rectangular cross section is formed, and a plurality of first optical waveguide chips mounted on the base substrate in a form supported by the spacer member are provided.
The plurality of first optical waveguide chips are arranged along a direction perpendicular to the loading direction of the base substrate and the first optical waveguide chip, and the first of two adjacent first optical waveguide chips. It is loaded on the base substrate so that the entrance / exit end faces of the optical waveguide of 1 face each other.
The base substrate is composed of three or more layers including the first substrate and the first clad layer, and the coefficient of thermal expansion of the inner layer is extremely different from the coefficient of thermal expansion of the outer layer in the stacking direction. Has a value-taking structure
The plurality of first optical waveguide chips are composed of three or more layers including the second substrate and the second clad layer, and the inner layer with respect to the coefficient of thermal expansion of the outer layer in the stacking direction thereof. A connection structure of an optical waveguide chip, which has a structure in which the coefficient of thermal expansion of the above takes an extreme value. In the connection structure of the optical waveguide chip according to claim 1.
The base substrate is a connection structure of an optical waveguide chip, which is a second optical waveguide chip in which a second optical waveguide is formed in the first clad layer. A base substrate having a plurality of first grooves having a rectangular cross section and
A plurality of spacer members, each of which is fitted with the plurality of first grooves in a form in which a part thereof protrudes from the base substrate.
Along with the formation of the first optical waveguide, a second groove having a rectangular cross section is formed on the surface facing the first groove and fitted with the protruding portion of the spacer member, and is supported by the spacer member. A plurality of first optical waveguide chips mounted on the base substrate in a rectangular shape are provided.
The plurality of first optical waveguide chips are arranged along a direction perpendicular to the loading direction of the base substrate and the first optical waveguide chip, and the first of two adjacent first optical waveguide chips. It is loaded on the base substrate so that the entrance / exit end faces of the optical waveguide of 1 face each other.
The base substrate is composed of three or more layers including a first substrate and a first clad layer on which the first groove is formed, which is provided on the first substrate, and is outside in the stacking direction thereof. Has a structure in which the coefficient of thermal expansion of the inner layer takes an extreme value with respect to the coefficient of thermal expansion of the layer of
Each of the plurality of first optical waveguide chips is provided on a second substrate and the second substrate, and the first optical waveguide and the second clad layer on which the second groove is formed are formed. A connection structure of an optical waveguide chip, which comprises three or more layers including and, and has a structure in which the coefficient of thermal expansion of the inner layer takes an extreme value with respect to the coefficient of thermal expansion of the outer layer in the stacking direction. .. In the connection structure of the optical waveguide chip according to claim 3.
The base substrate is a connection structure of an optical waveguide chip, which is a second optical waveguide chip in which a second optical waveguide is formed on the first substrate or the first clad layer .

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