JP2004279587A - Embedded optical component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an embedded optical component which has excellent optical coupling efficiency with respect to the embedded optical component used for optical communication or the like. <P>SOLUTION: The embedded optical component is composed of an outgoing side optical waveguide 10 and an incident side optical waveguide 11 which are embedded in a substrate 12, a groove 13 formed by cutting the interval between the outgoing side optical waveguide 10 and the incident side optical waveguide 11 and an optical element 1 which is inserted into the groove 13 and has a micro lens 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an embedded optical component used in optical communication and the like.
[0002]
[Prior art]
There is known an embedded optical component in which a waveguide is formed by embedding an optical fiber in a substrate, a groove for cutting the waveguide is formed, and various optical elements are inserted into the groove. For example, Patent Documents 1 and 2 disclose embedded optical components in which an optical isolator is inserted into a groove as an optical element. The embedded optical component has the advantages that it is easy to manufacture, and can be reduced in size and cost.
[0003]
[Patent Document 1]
JP-A-7-110412 [Patent Document 2]
JP-A-4-307512
[Problems to be solved by the invention]
However, in such a buried optical component, the light emitted from the emission side optical waveguide into the groove diverges at the light emission end and is diffracted by the optical element. There is a problem that the amount of incident light is reduced to cause a coupling loss.
[0005]
In a buried optical component having a multi-terminal waveguide in which a plurality of waveguides are arranged in parallel, in the groove, a part of the emission light diverged at a certain exit side waveguide end is adjacent to the light incident side end of the adjacent waveguide. There is a possibility that the light may enter the portion and cause crosstalk.
[0006]
An object of the present invention is to provide a buried optical component having excellent optical coupling efficiency.
[0007]
[Means for Solving the Problems]
The object is to provide an emission-side optical waveguide and an incidence-side optical waveguide embedded in a substrate, a groove formed by cutting between the emission-side optical waveguide and the incidence-side optical waveguide, And an optical element provided with a microlens.
[0008]
In the embedded optical component of the present invention, the microlens is formed on an optical substrate, and has a refractive index different from that of the optical substrate. Further, in the embedded optical component of the present invention, a wavelength selection filter is formed between the optical substrate and the microlens.
[0009]
Further, in the embedded optical component of the present invention, the optical substrate is a polarizer. Further, the optical element includes a Faraday rotator, a first polarizer disposed on a light incident surface of the Faraday rotator, and a second polarizer disposed on a light exit surface of the Faraday rotator. Wherein the microlens is formed on a light incident surface of the first polarizer and on a light exit surface of the second polarizer.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
A buried optical component according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a schematic configuration of an embedded optical component 9 according to the present embodiment. The embedded optical component 9 has, for example, an emission-side optical waveguide 10 and an incidence-side optical waveguide 11 formed by embedding an optical fiber in a substrate 12 mainly composed of glass and having the same optical axis. A groove 13 is formed between the emission-side optical waveguide 10 and the incidence-side optical waveguide 11 by cutting the waveguides 10 and 11. The optical element 1 is inserted into the groove 13.
[0011]
The optical element 1 of the present embodiment has an optical filter 4 formed of a dielectric multilayer film on a glass substrate, and a micro lens 8 formed on the optical filter 4. In the groove 13, the optical element 1 is arranged in the order of the optical filter 4 and the microlens 8 from the emission side optical waveguide 10 side to the incident side optical waveguide 11 side. The optical axes of the optical filter 4 and the microlens 8 coincide with the optical axes of the emission-side optical waveguide 10 and the incidence-side optical waveguide 11. The optical filter 4 functions as a wavelength selection filter for transmitted light / reflected light, and the microlens 8 functions as a condensing optical element for condensing transmitted light.
[0012]
Next, a method of manufacturing the embedded optical component 9 according to the present embodiment will be described. First, a method for manufacturing the optical element 1 will be described with reference to FIG. As shown in FIG. 2A, an optical filter 4 is manufactured by depositing a dielectric multilayer film 3 as an optical filter element on an optically polished glass substrate 2 having a diameter of 3 inches. Next, using a plasma CVD apparatus, as shown in FIG. 2B, a Ge-doped glass thin film (refractive index), which is a 5 μm-thick optical thin film doped with Ge (germanium) on the dielectric multilayer film 3, A control film 5 is formed. The refractive index control film 5 has a different refractive index from the glass substrate 2.
[0013]
Next, a photoresist is applied on the refractive index control film 5 by a spin coating method to form a photoresist layer having a thickness of 1.5 μm. Next, the photoresist layer is patterned using a photolithography method to form a columnar resin layer 6 having a diameter of 5 μm to 20 μm as shown in FIG.
[0014]
Next, the glass substrate 2 on which the refractive index control film 5 and the resin layer 6 are laminated is placed on a hot plate and subjected to a heat treatment at 150 ° C. for 5 minutes, as shown in FIG. The resin layer 6 is caused to flow to form a resin layer 7 having a curved outer surface (for example, a hemispherical shape such as a lens shape).
[0015]
Next, the refractive index control film 5 is etched by anisotropic etching such as RIE (reactive ion etching) using the resin layer 7 as an etching mask. At the time of this etching, the resin layer 7 of the etching mask is also gradually etched away from the peripheral portion, so that the three-dimensional resin layer 7 before etching is formed on the dielectric multilayer film 3 as shown in FIG. A microlens 8 having a curved outer surface similar to the shape is formed. Next, the glass substrate 2 is cut into a predetermined size, and the optical element 1 in which the micro lens 8 is formed on the optical filter 4 is completed.
[0016]
On the other hand, an optical fiber is buried in the substrate 12, a waveguide is formed, a groove 13 is formed, and the waveguide is cut, thereby forming the exit-side optical waveguide 10 and the entrance-side optical waveguide 11 whose optical axes match. Next, the optical element 1 is inserted into the groove 13 to complete the embedded optical component 9.
[0017]
Next, the operation of the embedded optical component 9 according to the present embodiment will be described. Light transmitted through the emission-side optical waveguide 10 is emitted into the groove 13 from the emission end of the emission-side optical waveguide 10. The emitted light becomes divergent light having an angle component, enters the optical filter 4 of the optical element 1, and selectively transmits light of a predetermined wavelength. The transmitted light that has passed through the optical filter 4 enters the microlens 8, is condensed, and enters the incident-side optical waveguide 11. The light coupling loss of the microlens 8 can sufficiently reduce the optical coupling loss on the incident side optical waveguide 11 side.
[0018]
As described above, according to the embedded optical component 9 of the present embodiment, the light diverged / diffracted in the groove 13 can be condensed and incident on the incident side optical waveguide 11, so that the optical coupling loss can be sufficiently reduced. Will be able to do that.
[0019]
Next, a buried optical component according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic configuration of the embedded optical component 19 according to the present embodiment, and shows a cross section cut in a direction perpendicular to the substrate surface. The embedded optical component 19 has an emission-side optical waveguide 22 and an incidence-side optical waveguide 23 formed by embedding an optical fiber in a substrate 24 mainly composed of glass and having the same optical axis. A groove 13 is formed between the emission-side optical waveguide 22 and the incidence-side optical waveguide 23 by cutting the waveguides 22 and 23. The optical element 21 is inserted into the groove 13.
[0020]
The optical element 21 according to the present embodiment functions as an optical isolator with microlenses. The optical element 21 has a Faraday rotator 20 disposed at the center. The polarizer 14a is arranged on the light incident surface side (the exit side optical waveguide 22 side) of the Faraday rotator 20, and 45 degrees with respect to the optical axis of the polarizer 14a on the light exit surface side (the incident side optical waveguide 23 side). A polarizer 14b having an optical axis inclined at an angle is disposed. As the polarizers 14a and 14b, a birefringent plate such as rutile or polarizing glass can be used. A micro lens 18a is formed on the light incident surface side of the polarizer 14a. A micro lens 18b is formed on the light exit surface side of the polarizer 14b. The optical axis from the micro lens 18a to the micro lens 18b of the optical element 21 coincides with the optical axis of the emission-side optical waveguide 22 and the incidence-side optical waveguide 23. An optical isolator is composed of the Faraday rotator 20, the polarizers 14a and 14b on both sides thereof, and a magnet (not shown) that applies a magnetic field to the Faraday rotator 20. The micro lens 18a functions as a collimating lens for shaping the divergent wavefront of the light emitted from the emission side optical waveguide 22 into a substantially parallel wavefront, and the micro lens 18b functions as a light collecting optical element for collecting light emitted from the optical isolator. It is supposed to.
[0021]
Next, a method of manufacturing the embedded optical component 19 according to the present embodiment will be described. First, a method for manufacturing the optical element 21 will be described with reference to FIG. As shown in FIG. 4A, a Ge-doped glass thin film (refractive index control film) 15 which is a 3 μm-thick optical thin film doped with Ge (germanium) is formed on the polarizer 30 by using a plasma CVD apparatus. Form a film. The refractive index control film 15 has a different refractive index from the polarizer 30. After the refractive index control film 15 is formed, the outer surface similar to the three-dimensional shape of the resin layer 17 before the etching is formed on the polarizer 30 through the steps of FIGS. Are formed. Next, the polarizer 30 is cut out to a predetermined size, and the polarizer 14a on which the microlenses 18a are formed is manufactured. Similarly, a polarizer 14b having a microlens 18b formed thereon is manufactured. The optical axes of the polarizers 14a and 14b are aligned on a predetermined direction on both sides of the Faraday rotator 20 and fixed with, for example, an optical adhesive, thereby completing the optical element 21 of the optical isolator having the microlenses 18 formed on both sides. Note that the manufacturing steps of FIGS. 4B to 4D are substantially the same as the manufacturing steps of FIGS. 2C to 2E, and a description thereof will be omitted.
[0022]
On the other hand, a waveguide is formed by embedding an optical fiber in the substrate 24, the groove 13 is formed, and the waveguide is cut, so that the emission-side optical waveguide 22 and the incidence-side optical waveguide 23 whose optical axes coincide with each other are formed. Next, the optical element 21 is inserted into the groove 13 to complete the embedded optical component 19.
[0023]
Next, the operation of the embedded optical component 19 according to the present embodiment will be described. Light transmitted through the emission-side optical waveguide 22 is emitted into the groove 13 from the emission end of the emission-side optical waveguide 22. The emitted light becomes divergent light having an angular component and enters the optical element 21, is shaped into a substantially parallel wavefront by the microlens 18a, and enters the optical isolator. The light emitted by rotating the polarization direction by a predetermined amount by the optical isolator enters the microlens 18 b and is collected, and then enters the incident side optical waveguide 23. Due to the light condensing action of the micro lens 18b, the optical coupling loss in the incident side optical waveguide 23 can be greatly reduced. Further, for example, the light reflected on the incident end face of the incident-side optical waveguide 23 is blocked by the optical isolator function of the optical element 21, so that the reflected light is not coupled to the emission-side optical waveguide 22.
[0024]
As described above, according to the embedded optical component 19 of the present embodiment, the light diverged / diffracted in the groove 13 can be shaped and made incident on the incident side optical waveguide 23, so that the optical coupling efficiency is further improved. Will be able to do it. Further, light propagating in the opposite direction from the incident side optical waveguide 23 toward the emission side optical waveguide 22 is blocked by the optical element 21 which is an optical isolator with a microlens, and is not coupled to the emission side optical waveguide 22. Can prevent the oscillation of a laser diode (not shown) used in the system, and can improve the stability of the whole system using the embedded optical component 19.
[0025]
Next, a buried optical component according to a third embodiment of the present invention will be described with reference to FIG. The embedded optical component of the present embodiment is characterized in that a plurality of sets of light emitting waveguides and light incident waveguides and an optical isolator having a microlens array therebetween are provided. I have. FIG. 5 is a schematic configuration of the embedded optical component 25 according to the present embodiment, and shows a state viewed in the normal direction of the substrate surface. The method of manufacturing the embedded optical component 25 according to the present embodiment is the same as that of the embedded optical components 1 and 21 according to the first and second embodiments, and a description thereof will be omitted.
[0026]
The buried optical component 25 is formed by embedding, for example, four optical fibers in the substrate 12 mainly composed of glass, and includes four sets of the emission-side optical waveguides 27 and the incidence-side optical waveguides 28 whose optical axes coincide with each other. Have. The grooves 13 are formed by cutting the waveguides 27 and 28 between each pair of the exit side optical waveguide 27 and the entrance side optical waveguide 28. An optical element 26 is inserted into the groove 13.
[0027]
The optical element 26 of the present embodiment functions as an optical isolator with a microlens array. The optical element 26 has a Faraday rotator 20 disposed at the center. The polarizer 14a is disposed on the light incident surface side (the exit side optical waveguide 27 side) of the Faraday rotator 20, and 45 degrees with respect to the optical axis of the polarizer 14a on the light exit surface side (the incident side optical waveguide 27 side). A polarizer 14b having an optical axis inclined at an angle is disposed. Microlenses 18a are formed on the light incident surface side of the polarizer 14a so as to coincide with the optical axes of the respective exit-side optical waveguides 27. Microlenses 18b are formed on the light exit surface side of the polarizer 14b so as to coincide with the optical axes of the respective incident side optical waveguides 28. The optical axes of the microlenses 18a and the microlenses 18b corresponding to the exit-side optical waveguides 27 and the entrance-side optical waveguides 28 of the respective sets coincide with the optical axes of the exit-side optical waveguides 22 and the incident-side optical waveguides 23 of the respective sets. ing. An optical isolator is composed of the Faraday rotator 20, the polarizers 14a and 14b on both sides thereof, and a magnet (not shown) that applies a magnetic field to the Faraday rotator 20. Each micro lens 18a functions as a collimating lens for shaping the wavefront of the light emitted from each emission side optical waveguide 27, and each micro lens 18b functions as a condensing optical element for condensing light emitted from the optical isolator. It has become.
[0028]
Next, the operation of the embedded optical component 25 according to the present embodiment will be described. The operations of the emission-side optical waveguide 27, the incidence-side optical waveguide 28, and the optical element 26 of each set are the same as those of the embedded optical component 19 of the second embodiment. Therefore, since the divergent light emitted from a certain emission-side optical waveguide 27 is condensed after wavefront shaping by the action of the microlenses 18a and 18b, the light emitted from the microlens 18b does not enter the adjacent incident-side optical waveguide 28. Therefore, crosstalk generated between adjacent optical waveguides can be significantly reduced.
[0029]
As described above, according to the embedded optical component 25 of the present embodiment, the light diverged / diffracted in the groove 13 can be shaped and made incident on the predetermined optical waveguide on the incident side 28, so that the optical coupling efficiency is further improved. Can be improved. Further, light propagating in the opposite direction from the incident side optical waveguide 28 to the emission side optical waveguide 27 is blocked by the optical element 26 which is an optical isolator with a microlens, and is not coupled to each emission side optical waveguide 27. Instability of oscillation of a laser diode (not shown) used as a light source can be prevented, and stability of the whole system using the embedded optical component 25 can be improved. Further, even when a plurality of optical waveguides are formed in an array, crosstalk generated between adjacent optical waveguides can be sufficiently reduced.
[0030]
The present invention is not limited to the above embodiment, and various modifications are possible.
For example, the refractive index of the microlenses 8, 18a, 18b in the above embodiment is constant in the film thickness direction, but the present invention is not limited to this. For example, the microlenses 8, 18a, 18b may be formed using a refractive index control film whose refractive index changes continuously or stepwise in the film thickness direction, and a microlens with small aberration can be realized. .
[0031]
Further, in the above embodiment, the outer surfaces of the microlenses 8, 18a, and 18b are formed in a curved shape that is convex with respect to the substrate surface, but the present invention is not limited to this. A microlens 8, 18a, 18b having a curved surface with a part of the refractive index control film concave with respect to the substrate surface is formed so that light transmitted from the substrate through the microlenses 8, 18a, 18b becomes a divergent light beam. Of course you can.
[0032]
Further, in the above-described embodiment, the embedded optical components 9, 19, and 25 in which optical fibers are embedded in the substrates 12, 24 have been described as examples, but the present invention is not limited to this. Of course, it is also possible to use the optical elements 1, 21, 26 between optical fibers or in a plane optical waveguide instead of the embedded optical components 9, 19, 25.
[0033]
【The invention's effect】
As described above, according to the present invention, a buried optical component having excellent optical coupling efficiency can be realized.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of an embedded optical component according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a method of manufacturing the optical element 1 according to the first embodiment of the present invention.
FIG. 3 is a view showing a schematic configuration of a buried optical component according to a second embodiment of the present invention, showing a cross section cut in a direction perpendicular to a substrate surface.
FIG. 4 is a diagram illustrating a method for manufacturing an optical element 21 according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a schematic configuration of a buried optical component according to a third embodiment of the present invention, as viewed in a direction normal to a substrate surface.
[Explanation of symbols]
1, 21, 26 Optical element 2 Glass substrate 3 Dielectric multilayer film 4 Optical filter 5, 15 Refractive index control film 6, 7, 16, 17 Resin layer 8, 18a, 18b Microlens 9, 19, 25 Embedded light Components 10, 22, 27, 27a Emission-side optical waveguides 11, 23, 28, 28a Incident-side optical waveguides 12, 24 Substrate 13 Grooves 14a, 14b, 30 Polarizer 20 Faraday rotator

Claims (5)

An emission-side optical waveguide and an incidence-side optical waveguide formed by being embedded in a substrate,
A groove formed by cutting between the emission-side optical waveguide and the incidence-side optical waveguide,
And an optical element having a microlens inserted in the groove. The embedded optical component according to claim 1,
The embedded optical component, wherein the microlens is formed on an optical substrate and has a refractive index different from a refractive index of the optical substrate. The embedded optical component according to claim 2,
An embedded optical component, wherein a wavelength selection filter is formed between the optical substrate and the microlens. The embedded optical component according to claim 2 or 3,
The embedded optical component, wherein the optical substrate is a polarizer. The embedded optical component according to claim 1 or 4,
The optical element,
A Faraday rotator,
A first polarizer disposed on a light incident surface of the Faraday rotator;
A second polarizer disposed on the light exit surface of the Faraday rotator,
The embedded optical component, wherein the microlens is formed on a light incident surface of the first polarizer and a light exit surface of the second polarizer.

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