JP6473391B2 - Polarization control element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a polarization control element and a manufacturing method thereof, and more particularly to a polarization control element in which a thin wave plate is disposed on an end face of a planar optical circuit and a manufacturing method thereof.

  In order to promote an increase in capacity and cost reduction of information communication, further enhancement of functions of optical communication technology is desired. Planar optical circuit components using a waveguide mechanism are widely used in the field of optical communications because they can mount optical multiplexing / demultiplexing functions, branching functions, switching functions, and the like with high accuracy. In particular, a planar lightwave circuit (PLC) made of quartz glass is excellent in coupling with optical fibers and has high reliability as a material, so it can be used for optical communications such as splitters, wavelength multiplexers / demultiplexers, and optical switches. It is applied to a wide variety of functional elements. In recent years, digital coherent communication including the phase and polarization of light has been realized in order to cope with an increase in communication traffic. Accordingly, even if an optical component such as a PLC is used, the phase and polarization can be adjusted. The need for precise control has emerged.

  In general, a planar lightwave circuit made of glass has birefringence due to residual stress at the time of manufacture, and this birefringence affects polarization. In order to control polarization, a method for controlling the phase of light with high accuracy while considering the birefringence characteristic of the waveguide is required. As such a technique, for example, a technique of changing the internal stress by changing the structure in the vicinity of the waveguide can be considered, but it has a drawback that it involves a process load. On the other hand, a technique for integrating a birefringent crystal or a resin with a PLC has been reported. For example, a method of changing the phase of light by filling a part of a waveguide with a birefringent resin that is compatible with glass is known.

  In this method of filling a part of a waveguide with a birefringent resin, a groove is formed in the optical waveguide of the PLC, and a wave plate having a large birefringence and a precisely controlled value is inserted therein. The As the wave plate to be inserted, a half-wave plate, a quarter-wave plate or the like obtained by orienting a polyimide film having a large optical anisotropy is drawn and oriented, and this is used to make polarization independent. (For example, refer to Patent Document 1).

  Further, between the waveguide type Y-branch coupler formed in the planar lightwave circuit and the multimode coupler, the slow axis is 0 ° and 90 ° with respect to the surface of the planar lightwave circuit. In addition, an application such as a polarization beam splitter PLC with a wide wavelength band is realized by inserting a ¼ wavelength plate (see, for example, Non-Patent Document 1). In this way, by arranging the phase plate so that the slow axis is in the direction of 45 ° orthogonal to the waveguide traveling direction in the PLC, it differs from the TE mode and TM mode of the light in the waveguide. A method of giving a phase difference is often used as a polarization control element for PLC.

  In addition, in the polarization control element, it is also required to apply such a phase collectively to a plurality of waveguide arrays. As described in Patent Document 2, it is also possible to integrate the polarization splitter function into a plurality of arrayed waveguides at once by inserting a comb-shaped wave plate into the groove of the PLC.

  In the above example, phase control is performed by inserting a wave plate into the groove in the waveguide. However, when phase is applied to the input / output part of the optical waveguide, similarly, It can also be realized by arranging in the vicinity of the input / output end face.

Japanese Patent No. 3501235 JP 2003-207668 A

Yusuke Nasu, et.al, “Temperature Insensitive and Ultra Wideband Silica-based Dual Polarization Optical Hybrid for Coherent Receiver with Highly Symmetrical Interferometer Design,” Tu.3.LeSaleve.4, 37th European Conference and Exhibition on Optical communication 2011 (September 18 -22, 2011, Geneva, Switzerland)

  As described above, it is possible to control the polarization of input / output light by arranging a wave plate in the vicinity of the input / output end face of the optical waveguide. From a plurality of waveguide arrays fabricated in the PLC, as a spatial beam In the case of outputting (or inputting) light, when the polarization control of the output light is performed collectively, it is realized by arranging the aforementioned comb-shaped wave plate in the vicinity of the input / output end face of the PLC. In view of actually producing such a configuration, in order to fix the orthogonal relationship between the slow axis of the wave plate and the circuit, both are integrated, that is, a plane like the polarization control element shown in FIG. It is preferable to arrange the wave plate 104 on the end face of the mold optical circuit 100 using an adhesive or the like.

  However, in order to produce a wavelength plate integrated planar optical circuit (PLC) 100 as shown in FIG. 1, it is preferable to use a thin wave plate 104 such as polyimide from the viewpoint of loss deterioration, The plate was low in rigidity, and it was very difficult to handle it for bonding work. As shown in FIG. 1 (a), the phase imparting section and the air section (also referred to as non-phase imparting section) provided in a given portion of the comb wave plate 104 are maintained so that the slow axis is at a predetermined angle. Although it is necessary to accurately align with the arrayed waveguide core 102 of the PLC 102, it is difficult to align the comb wave plate 104.

  FIG. 2 is a cross-sectional view of the PLC 100 including the waveguide core 102. As shown in FIG. 2, when the comb-shaped wave plate 104 is bonded to the end face of the PLC using the adhesive 200, the adhesive is filled in the air portion (non-phase imparting portion) of the comb-shaped wave plate. Actually, it is difficult to fill the non-phase imparting portion (air portion) with an adhesive so as to have a uniform thickness as shown in FIG. The thickness of the adhesive (also referred to as an adhesive layer) becomes uneven. Due to the difference in the thickness of the adhesive layer, (1) the optical path length is different for each waveguide array, and as a result, the light propagation characteristics when the beam is emitted into the space are not uniform among the waveguide arrays. (2) Depending on the shape of the adhesive layer, the effect of a lens or the like may be manifested, and inconveniences such as the beam diameter differing from the design value may occur. Further, when the adhesive 200 is solidified, volume shrinkage occurs due to curing shrinkage, and accordingly, stress is generated in the comb-shaped wave plate 104, and further warping occurs in the comb-shaped wave plate 104 itself. This stress causes photoelastic birefringence to the comb wave plate (also referred to as phase plate) 104 and causes the lens effect as described above, and the phase difference of the wave plate at the time of design is As a result, there is a problem that precise polarization control and beam quality control become difficult.

  The present invention has been made in view of such problems, and the object of the present invention is to make the thickness of the adhesive layer uniform when adhering the wave plate, and to perform precise polarization control and beam It is an object of the present invention to provide a polarization control device capable of quality control and a manufacturing method thereof.

  A first aspect of the present invention for achieving such an object is a polarization control element for controlling polarization for outputting a light beam in space. The polarization control element includes a planar optical circuit (PLC) in which a plurality of optical waveguides are formed, a wave plate disposed on an end surface of the planar optical circuit, and a glass plate disposed together with the wave plate. The wave plate includes a phase applying unit that gives a desired phase difference to a desired waveguide among the plurality of optical waveguides formed on the PLC, and a non-phase difference that does not give a phase difference to the remaining waveguides of the plurality of optical waveguides. A phase providing unit. The non-phase imparting unit communicates with an open end in a cross-sectional shape orthogonal to the traveling direction of light. The end face of the PLC, the wave plate, and the glass plate are fixed by a filler, and the non-phase imparting portion of the wave plate between the end face of the PLC and the glass plate is uniformly filled with the filler.

  The filler may include a first filler material and a second filler material. In one embodiment, the first filler material is an adhesive and the second filler material is a refractive index matching material. The end face of the PLC, a part of the wave plate, and the glass plate are fixed with an adhesive. The non-phase imparting portion is filled with a refractive index matching material.

  In one embodiment, the polarization control element further includes a second glass plate disposed on the end face of the PLC together with the glass plate and the wavelength plate. The two glass plates including the second glass plate and the wave plate are fixed by a filler (for example, an adhesive), and the filler (for example, refractive index matching) is provided in the non-phase imparting portion of the wave plate between the two glass plates. Material) is uniformly filled. The second glass plate is fixed to the end face of the PLC.

  In one embodiment, a groove may be provided in the glass plate so that the adhesive that fixes the glass plate and the wave plate and the filler are not mixed in the non-phase imparting portion of the wave plate.

  A second aspect of the present invention is a method for manufacturing the above polarization control element.

  As described above, according to the present invention, it is possible to make the thickness of the adhesive layer uniform when adhering the wave plate, and the polarization control device capable of precise polarization control and beam quality control and The manufacturing method can be provided.

It is a figure which shows the polarization control element provided with the planar optical circuit and the wave plate arrange | positioned at an end surface, (a) is a perspective view, (b) is A- containing the waveguide core of (a). It is A 'sectional drawing. It is a figure for demonstrating the problem at the time of bonding a wavelength plate on the end surface of the planar optical circuit of a polarization control element using an adhesive agent. It is a figure which shows the polarization control element of one Embodiment of this invention, and is the figure which arrange | positioned the glass plate and the wavelength plate on the end surface of the planar optical circuit using the adhesive agent. It is a figure for demonstrating the structure of the wavelength plate in one Embodiment of this invention, (a) is sectional drawing of the planar optical circuit in the wavelength plate arrange | positioned with the glass plate in the end surface, (b) is It is sectional drawing of the multiwavelength plate suitable for implementation of this invention, (c) is a step view of the multiwavelength plate which is not suitable for implementation of this invention. It is a figure for demonstrating the manufacturing method of the polarization control element of one Embodiment of this invention, and is a figure for demonstrating the method of arrange | positioning a wavelength plate with a glass plate in the end surface of a planar optical circuit. It is a figure which shows the polarization control element of one Embodiment of this invention, and is a figure which shows the planar optical circuit (polarization beam splitter) which has arrange | positioned the glass plate and the wavelength plate to the end surface. It is a figure for demonstrating the polarization control element of one Embodiment of this invention. It is a figure for demonstrating the polarization control element of one Embodiment of this invention, (a) is a figure which shows a glass plate, (b) is a glass plate of (a) on the end surface of a planar optical circuit, and It is a figure which shows the polarization control element which has arrange | positioned the wavelength plate. It is a figure for demonstrating the polarization control element of one Embodiment of this invention, (a) is a figure which shows the structure which pinched | interposed the wavelength plate between two glass plates, (b) is a figure of (a). It is sectional drawing of a structure, (c) is a figure which shows the polarization control element which has arrange | positioned the structure of (a) to the end surface of a planar optical circuit. It is a figure for demonstrating the polarization control element of one Embodiment of this invention, (a) is a figure which shows the structure which pinched | interposed the wavelength plate between the glass plates shown to Fig.8 (a), (b) It is a figure which shows the polarization control element which has arrange | positioned the structure of (a) to the end surface of a planar optical circuit. It is a figure for demonstrating the polarization control element of one Embodiment of this invention, (a) is the glass plate of the polarization control element shown in FIG.3, FIG.6 (a) or FIG.8 (b), It is a figure which shows the polarization control element changed into the glass plate with an antireflection film, (b) is a glass plate of the polarization control element shown in FIG.9 (c) or FIG.9 (b), with an antireflection film. It is a figure which shows the polarization control element changed into the glass plate.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or similar symbols indicate the same or similar elements. Therefore, the overlapping description is omitted. In the following description, specific numerical examples and the like are shown, but the present invention is not limited to these, and can be carried out even with other numerical values without losing generality.

(First embodiment)
FIG. 3 shows the configuration of the polarization control element of the first embodiment of the present invention. The polarization control element of FIG. 3 includes a planar optical circuit (PLC) 100 and a thin wave plate 104 and a glass plate 300 disposed on the end face of the PLC 100. The PLC 100 includes a waveguide array including a plurality of waveguides, and outputs a light beam from an end surface to space. In the PLC 100, a thin wave plate 104 and a glass plate 300 are disposed on the end face on the beam output side. The wave plate 104 is formed with a phase applying unit that gives a desired phase difference to light emitted from a part of a desired waveguide core in the optical waveguide array 102. In the planar optical circuit 100 of the polarization control element according to the present embodiment, a wave plate 104 in which a desired waveguide core 102 and a phase providing unit are aligned is disposed between the glass plate 300 and the end face of the PLC. In this structure, the adhesive is filled and fixed.

  As described above with reference to FIG. 2, in the conventional structure in which the comb-shaped wave plate is directly bonded to the PLC, the adhesive is filled in the non-phase imparting portion (air portion) of the comb-shaped wave plate. Due to the surface tension and overflow of the agent, the optical path length, lens effect, and disturbance of the spatial beam have occurred. As will be described later, in the structure of the planar optical circuit according to the present embodiment, the thickness of the adhesive layer 200 is defined by the gap between the glass plate 300 and the end face of the PLC 100. As described with reference to FIG.

  An example of the wave plate 104 is a comb wave plate in which phase imparting portions are formed in a comb shape. The shape of a cross section orthogonal to the traveling direction of the light beam (hereinafter also referred to as an orthogonal cross section) Similar effects can be obtained as long as the shape of the phase applying portion is such that a desired phase difference is given to a part of the desired waveguides. However, as a shape of the wave plate on which the phase applying part is formed, a region that does not give a phase difference (a beam does not pass through the wave plate) in the orthogonal cross section, that is, a region in which the phase applying part is not formed ( As shown in FIGS. 4A and 4B, the air portion and the non-phase imparting portion have a shape having an open end, for example, a comb shape, a rectangle or a polygon, or a circle, an ellipse or a curve. It is preferable that there is a region (that is, a region which is not a closed shape, and a non-closed portion is an open end). That is, as shown in FIG. 4B, it is not preferable that the region where no phase difference is given is closed. This is because if the adhesive layer penetrates into the closed area, there will be no area to escape when bubbles are generated, and bubbles will be generated in the beam passing area. This is because it disappears. If the shape has an open end (further, the region where the phase imparting portion is not formed through the open end (the shape in which the air portion and the non-phase imparting portion) communicate with each other) It is possible to remove the bubbles by performing a process such as pressing or depressurizing so that the bubbles come out of the region through the open end.

<Manufacturing method>
Below, with reference to FIG. 5, the manufacturing method of the planar optical circuit of this embodiment is demonstrated. First, a PLC having a plurality of waveguides is manufactured, and its end face is polished flat. Here, an example of right-angle polishing at 90 ° is shown, but a predetermined angle such as 8 ° polishing or 45 ° polishing may be applied. In this case, the light beam is output at a predetermined angle along Snell's law. The PLC is manufactured so that light output from the arrayed waveguide satisfies a single mode condition, and generally two orthogonal polarization modes of a TE mode and a TM mode are output. In the present embodiment, as shown in FIG. 6, in the PLC 100, the polarization beam splitter 600 is integrated on each of the optical input sides of the arrayed waveguides 102, and the modes TE, TM, TE, TM are transmitted from the ray waveguide 102. ... Are alternately output. In the example, the pitch between two adjacent TM modes (and between TM modes) is 125 μm.

  Next, a thin wave plate is produced. The material of the wave plate includes crystals, organic polymers, dielectric films, liquid crystals, etc., but it is preferable to reduce the thickness. As a medium suitable for thinness, a polyimide wave plate used for a conventional PLC is particularly preferable. Usually, the passage of the wave plate material leads to an increase in optical loss, but the reduction in loss due to diffraction or the like can be minimized by reducing the thickness. Preferably it is 50 micrometers or less. As an example, a 15 μm half-wave plate was used as a polyimide wave plate. The polyimide phase plate was machined to mold the phase imparting portions so that the pitch between adjacent phase imparting portions (and between the non-phase imparting portions (air portions)) was a comb having a 125 μm pitch. This pitch can be molded at an arbitrary pitch within the range possible with machining accuracy, and the phase applying portion can be molded at a desired waveguide position in the waveguide array of the PLC 100.

  In the present embodiment, a polarization control element in which a thin and comb-shaped wave plate 104 is arranged together with the glass plate 300 on the end face of the planar optical circuit so as to function as a polarization beam splitter as shown in FIG. By arranging the comb wave plate 104 on the output side end face of the arrayed waveguide 102 of the PLC 100, only one of the TE mode and the TM mode is output. In this embodiment, the phase imparting section and the non-phase imparting section (air) section of the thin wave plate 102 are adjacent to each other among the light modes TE, TM, TE, TM. In addition to the pitch between the TM modes, the pitch between the phase applying portions was set to 125 μm. In addition to the polarization beam splitter, a similar circuit can be realized by previously inputting polarization controlled by a polarization maintaining fiber or a polarization controller from input light. This time, an array of eight waveguides was fabricated in the PLC, but the number of waveguides is not limited to eight, and any number of waveguides may be used as long as it can be manufactured. In the following figures, for the sake of simplification of the drawing, the waveguide type polarization beam splitter is omitted and only a straight waveguide is shown. It is assumed that the polarization of the output beam is appropriately controlled by inputting the polarization. The output waveguide portion is illustrated by taking the beam output from a straight waveguide having a rectangular core as an example. However, the output waveguide portion is designed so that the output waveguide portion is rectangular, circular, or elliptical, or a rib type. A waveguide, a ridge-type waveguide, or the like may be used. Also, the output waveguide will be described by taking the light output from a single core as an example, but instead of the light output from a single core, it is connected to the light output from multiple waveguide arrays and slab waveguides. The present invention can also be applied to light output from a plurality of waveguide arrays. For example, as shown in FIG. 7, a plurality of slab waveguides 602 and a waveguide array composed of a plurality of waveguides 102 connected to the output side of each slab waveguide are produced in one PLC 100, and the waveguide array You may implement this invention in the form which arrange | positions the thin wave plate 104 and the glass plate 300 in the end surface of PLC100 so that polarization may be controlled every time.

Refer to FIG. 5 again.
(Procedure 11) Adhesive 200 is applied to the end face of the PLC 100.
(Procedure 12) Further, a wave plate 104 is attached. When attaching the wave plate, align it in advance so that the shape of the comb of the predetermined output port and the wave plate matches, and attach the wave plate so that the slow axis of the wave plate is 45 ° with respect to the horizontal plane of the PLC. . Thereby, the adhesive 200 is filled in the non-phase imparting portion (air portion) of the comb.
(Procedure 13) Thereafter, an optical glass plate 300 having a thickness of 0.5 mm and matching the size of the orthogonal cross section of PLC 100 (the cross section orthogonal to the traveling direction of the light beam) was mounted.
(Procedure 14) Thereafter, a certain pressing force was uniformly applied to the glass plate. As a result, the bubbles of the adhesive in the non-phase imparting portion of the comb are released to the open end side, there is no bubble, and the adhesive thickness is uniform.

  After this, the adhesive was cured. In this example, the curing of the adhesive was completed by irradiating with UV light in a state where the pressure was maintained using a UV curable adhesive having a refractive index substantially matching that of the PLC. The gap between the finished PLC and the glass plate was 16 μm, and it was confirmed that the entire surface had a uniform thickness. This is an effect of the present invention. That is, the thickness of the adhesive layer of the non-phase imparting portion (air portion) of the comb depends on the thickness and pressing force of the wave plate, and this time, by using a wave plate having a thickness of 15 μm, became. If the wave plate is made thicker, the adhesive layer thickness is increased, and if the wave plate is made thinner, the adhesive layer thickness can be reduced.

  In this case, the UV curable adhesive is used, but other adhesives such as heat curing and moisture curing may be used. However, the UV curing type is preferable from the viewpoint of simplicity of the curing process.

  When the warpage after adhesive curing was measured with a measuring device using interference, it was confirmed that the warpage was small enough to be ignored. Since the wave plate itself is thin, if the glass plate is not used, the wave plate is also deformed along the curing shrinkage of the adhesive, and the optical characteristics are deteriorated due to the lens effect caused by warping or bending. However, this effect can be eliminated by the present invention. This is also an effect of the present invention. In this embodiment, the glass plate 300 having a thickness of 0.5 mm is used, but the present invention is not limited to this value. However, if it is too thick, it will affect the loss of optical properties and the like, while if it is too thin, the influence of warp accompanying the curing shrinkage cannot be ignored. From the viewpoint of warpage, the thickness of the glass plate 300 is preferably 0.2 mm or more.

The adhesive 200 preferably has a small Young's modulus. Preferably, it is 5 × 10 ⁹ Pa or less, more preferably 1 × 10 ⁹ Pa or less. In the above example, an adhesive of 1 × 10 ⁹ Pa was used. Since the Young's modulus is small, the stress accompanying curing shrinkage is reduced, the stress applied to the wave plate is reduced, and the retardation property deterioration of the wave plate can be suppressed.

  According to this mounting form, the TE light output from the PLC 100 does not pass through the phase applying unit of the wave plate, but is output as TE light as it passes through only the adhesive layer, and the TM light is output as the phase applying unit of the wave plate. , Receives a phase of λ / 2, and is converted to TE light. As a result of actually measuring the degree of polarization with a polarimeter measuring device, it was confirmed that all were output as TE light.

  In this embodiment, a wave plate that gives a phase difference of λ / 2 is used. However, the phase difference may be arbitrarily changed according to the polarization state to be obtained. For example, if a λ / 4 plate is used, it can be converted into clockwise or counterclockwise circularly polarized light. Further, as described above, the cross-sectional shape of the wave plate is not limited to the comb shape, and may be any shape described above. For example, this time, in order to give the phase difference one after another, it has a comb shape. However, the phase difference of λ / 2 is given to the first to fourth ports, and the phase difference is given to the fifth to eighth ports. If not, a phase applying unit corresponding to the positions of the first to fourth ports is formed on the wave plate, and a non-phase applying unit (air unit) is provided at a position corresponding to the fifth to eighth ports. What is necessary is just to fill an adhesive agent.

(Second Embodiment)
A polarization control element according to the second embodiment of the present invention will be described with reference to FIG. The polarization control element of this embodiment includes a planar optical circuit (PLC) 100 and a thin wavelength plate 104 and a glass plate 700 disposed on the end face of the PLC 100. As the PLC 100 and the wave plate 104, the same planar optical circuit and comb wave plate as those of the first embodiment are used. Of course, different planar optical circuits and different wave plates may be used.

  FIG. 8A shows a glass plate 700. In the glass plate 700, two shallow grooves are formed on the surface of the glass plate (the surface facing the orthogonal cross section of PCL). Two grooves on the surface of the glass plate are formed in the horizontal direction (waveguide array direction), and the interval between the two grooves is equal to or slightly wider than the width in the vertical direction of the phase applying portion of the wave plate. A gap is generated between the end face of the PLC and the wave plate.

As shown in FIG. 8B, in this embodiment, the gap between the PLC 100 and the glass plate 700 is filled with two types of materials. As shown in FIG. 8B, with the groove 702 as a boundary, the PLC 100 in a region not including the waveguide core 102 and a part of the glass plate 700 or the wave plate 104 (the lower part of the wave plate 104 in FIG. 8B) The gap is filled with an adhesive 200 and fixed. Further, with the groove as a boundary, the gap between the PLC 100 and the glass 700 and the gap between the wave plate 104 in the region including the waveguide core 102 and the refractive index matching agent 704 as the second filler are filled. The refractive index matching agent 704 is made of high viscosity oil. Since this high-viscosity oil is essentially not cured, the effects of stress on the wave plate and the effects of warpage due to the curing shrinkage described above do not appear. Thereby, compared with 1st Embodiment, there exists an effect that stricter polarization control and beam quality maintenance are realizable. The gap between the glass plate 700 and the end face of the PLC 100 is defined with high accuracy by an adhesive, and the effects of the first embodiment can be obtained at the same time. In this embodiment, high-viscosity oil is used as the second filler. However, silicone grease or a polymer having a Young's modulus of 1 × 10 ⁷ Pa or less may be used.

  The groove 702 of the glass plate 700 exists to separate the adhesive that is the first filler and the refractive index matching resin that is the second filler without protruding. The groove 702 prevents the first filler and the second filler from protruding from each other across the boundary with the groove as a boundary when the adhesive or the filler is filled by capillary action described later.

Hereinafter, a method for manufacturing the polarization control element of this embodiment will be described. Basically, it can be manufactured in the same manner as the manufacturing method described in the first embodiment. However, it is realized by providing a device in the resin filling sequence. The PCL 100 and the wave plate 104 are manufactured as in the first embodiment. The glass plate 700 is produced by forming two V-grooves having a depth of about 0.1 mm as shown in FIG. 8A on a glass plate having a thickness of 0.5 mm. Thereafter, the waveguide 102 and the wave plate 104 are mounted at predetermined positions with the end face (orthogonal cross section) of the PLC 10 to be bonded facing upward. As shown in FIG. 8, the glass plate 700 is then mounted on the wave plate 104.
(Procedure 21) A first filler (adhesive 200) is placed in a first filling location (a gap between the PLC 100 and the glass plate 700 or the wave plate 104 in a region not including the waveguide core 102 with the groove 702 as a boundary). Infiltration using capillary action (for example, filling from the vertical direction).
(Procedure 22) After confirming that the adhesive has sufficiently penetrated, similarly, the second filling point (the gap between the PLC 100 in the region including the waveguide core 102 and the glass 700 or the wave plate 104 with the groove as a boundary) The second filling material (refractive index matching agent 704 (resin, high-viscosity oil having refractive index matching) is filled from the gap by utilizing capillary action (for example, filling from the horizontal direction).
(Procedure 23) Finally, a uniform pressing force is applied to the glass plate 700, and the adhesive is cured with UV light. At this time, a part of the wave plate 104 (the lower part of the wave plate 104 in FIG. 8B) is disposed in the region filled with the adhesive layer. It will be bonded and fixed. The phase imparting part and non-phase imparting part (air part) of the wave plate through which the outgoing beam passes are not filled with an adhesive, but are filled with high viscosity oil as the refractive index matching agent 704.

  In the above embodiment, the first filling material (adhesive) and the second filling material (refractive index matching agent 704 (resin, oil)) in the gap are filled at the same time, and then the first filling material is used. If the second resin is devised so that the second resin can permeate later, the same structure can be realized by filling only the first adhesive and curing, and then filling the second oil. That is, for example, a gap adjusting spacer may be interposed between the wave plate and the glass plate in advance, and then the second resin may be filled from the gap.

(Third embodiment)
A polarization control element according to a third embodiment of the present invention will be described with reference to FIG. The polarization control element of the present embodiment uses two glass plates 300 in order to make mounting easier in connection with the first embodiment. That is, the PCL 100 and the wave plate 104 are prepared in advance as in the first embodiment, the wave plate 104 is sandwiched between the two glasses 300, and the adhesive 200 is filled in the gap between the two glasses 300. Then, a cured structure (FIGS. 9A and 9B) is produced, and this is fixed to the end face of the PLC 100 with an adhesive 200 (FIG. 8C). Compared with the polarization control element of the first embodiment, although optical characteristic deterioration due to the increase of one glass plate occurs, the work efficiency of aligning the wave plate 104 with the PLC end face together with the glass plate 300 is improved. Greatly improved. In particular, when the distance between the waveguide cores on the end face of the PLC 100 is as narrow as several tens of μm and the positional relationship between the PLC 100 and the wave plate 104 is controlled with high accuracy, it is preferable to hold the jig with a jig or the like instead of manually. However, as shown in FIG. 9 (a), the two glass plates 300 and the wave plate 104 are integrated in advance so that they are held in a jig to perform sub-micron precision alignment and angle alignment. A new effect that it becomes possible to do so occurs.

  Actually, a PLC 100 having a plurality of waveguides was manufactured, and a λ / 4 wavelength plate integrated with two glass plates shown in FIG. 9B was attached to a part of the output end face. This λ / 4 wave plate has a complicated shape depending on the circuit, and the output pitch of some waveguides becomes narrow. Therefore, the positional relationship needs to be precisely controlled, but it is integrated with two glass plates. Alignment was performed on a submicron order by holding the converted wave plate with a jig and moving the jig while observing the position of the core and the position of the wave plate with a microscope image. After alignment, the λ / 4 wavelength plate integrated with the two glass plates and the PLC are fixed with a UV curable adhesive so as to be integrated with the PLC, and the polarization control element (FIG. 9C). )) Was produced. Circularly polarized light is output by the λ / 4 plate.

(Fourth embodiment)
A polarization control device according to a fourth embodiment of the present invention will be described with reference to FIG. In the polarization control element of this embodiment, the two glass plates 300 integrated with the wave plate 104 described in the third embodiment are formed with the two grooves 702 described in the second embodiment. The glass plate 700 (FIG. 8) is changed. The surface of the two glass plates 700 where the grooves are formed is opposed to each other, and the wavelength plate 104 is disposed between the first filler (adhesive) 200 and the second filler (refractive index matching agent) 704. Fill. The wavelength plate 104 integrated with the two glass plates 700 is fixed to the end face of the PLC 100 with a UV curable adhesive, thereby eliminating the effect of the second embodiment, that is, the influence of stress accompanying curing shrinkage, warping, etc. It is possible to achieve both suppression and the effect of the third embodiment, that is, improvement in mounting workability.

(Fifth embodiment)
A polarization control element according to the fifth embodiment of the present invention will be described with reference to FIG. In the polarization control element of this embodiment, the AR coating film (antireflection film) 1000 is provided on one surface of the space output side of the glass plates 300 and 700 in the polarization control element of any one of the first to fourth embodiments. It is the applied polarization control element. FIG. 11A is a diagram showing a polarization control element obtained by changing the glass plate of the polarization control element shown in FIG. 3, FIG. 6 or FIG. 8B to a glass plate with an antireflection film, and FIG. ) Is a diagram showing a polarization control element in which the glass plate of the polarization control element shown in FIG. 9C or FIG. 11B is changed to a glass plate with an antireflection film. Thereby, the reflected return light at the interface between the output light from the PLC 100 and the air can be suppressed, and the optical characteristics can be further improved.

100 Planar optical circuit, PLC
102 Waveguide Core, Waveguide Core Array 104 Comb Wave Plate 200 Adhesive, Adhesive Layer 300,700 Glass Plate 404 Wave Plate 600 Planar Optical Circuit (Polarized Beam Splitter)
602 Slab waveguide 702 Groove 704 Refractive index matching oil 1000 Antireflection film, AR coating film

Claims (7)

A polarization control element that outputs a light beam to space,
A planar optical circuit in which a plurality of optical waveguides are formed;
A wave plate disposed on an end face of the planar optical circuit;
A glass plate disposed with the wave plate;
The wave plate includes a phase applying unit that is disposed at a position corresponding to a desired waveguide among the plurality of optical waveguides and that gives a desired phase difference.
A position corresponding to the remaining waveguides of the plurality of optical waveguides is provided with a non-phase imparting portion that is in communication with each other and filled with a filler ,
The end face of the front Symbol planar optical circuit, the wave plate and the glass plate is fixed by the filling material, the in the non-phase imparting portion of the wavelength plate of the end face and the glass plates of the planar optical circuit A polarization control element characterized by being filled uniformly with a filler. The filler includes a first filler material and a second filler material, the first filler material is an adhesive, and the second filler material is a refractive index matching material;
The end face of the planar optical circuit, a part of the wave plate, and the glass plate are fixed by the adhesive, and the non-phase imparting portion of the wave plate between the end face of the planar optical circuit and the glass plate The polarization control element according to claim 1, wherein the refractive index matching material is filled. A second glass plate disposed between the end face of the planar optical circuit and the wave plate;
The second glass plate, the wave plate, and the glass plate are fixed by the filler, and the filler is also uniform in the non-phase imparting portion of the wave plate between the second glass plate and the glass plate. Filled in
The polarization control element according to claim 1, wherein the second glass plate is fixed to the end face of the planar optical circuit. The filler includes a first filler material and a second filler material, the first filler material is an adhesive, and the second filler material is a refractive index matching material;
The second glass plate, the wave plate, and the glass plate are fixed by the adhesive, and the refractive index matching material is provided in the non-phase imparting portion of the wave plate between the second glass plate and the glass plate. Filled,
The polarization control element according to claim 3, wherein the second glass plate is fixed to the end face of the planar optical circuit with an adhesive.   The polarization control element according to claim 1, wherein an antireflection film is formed on the glass plate. A method of manufacturing a polarization control element that outputs a light beam to space,
Applying a filler to the end face of a planar optical circuit in which a plurality of optical waveguides are formed;
A wave plate and a glass plate are disposed on the end face, and the wave plate is disposed at a position corresponding to a desired waveguide among the plurality of optical waveguides and has a phase applying unit that gives a desired phase difference. provided, at a position corresponding to the rest of the waveguide of the plurality of optical waveguides, they communicate with each other, non-phase deposition unit which filler is filled is provided, and that,
Pressing from the surface of the glass plate toward the end surface, and the non-phase imparting portion of the wave plate between the end surface of the planar optical circuit and the glass plate is uniformly filled with the filler. A method for manufacturing a polarization control element. A method of manufacturing a polarization control element that outputs a light beam to space,
The wave plate is disposed between two glass plates, and the wave plate includes a phase applying unit that is disposed at a position corresponding to a desired waveguide among a plurality of optical waveguides and gives a desired phase difference. A position corresponding to the remaining waveguides of the plurality of optical waveguides is provided with a non-phase imparting portion that communicates with each other and is filled with a filler ;
Excluding the phase imparting part and the non-phase imparting part, filling an adhesive between the two glass plates;
Filling the phase imparting portion and the non-phase imparting portion with a refractive index matching material;
And fixing one of the two glass plates to an end surface of the planar optical circuit in which the plurality of optical waveguides are formed.