WO2022071381A1 - Optical waveguide element, and optical modulation device and optical transmission apparatus using same - Google Patents

Optical waveguide element, and optical modulation device and optical transmission apparatus using same Download PDF

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Publication number
WO2022071381A1
WO2022071381A1 PCT/JP2021/035820 JP2021035820W WO2022071381A1 WO 2022071381 A1 WO2022071381 A1 WO 2022071381A1 JP 2021035820 W JP2021035820 W JP 2021035820W WO 2022071381 A1 WO2022071381 A1 WO 2022071381A1
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Prior art keywords
optical waveguide
optical
spot size
waveguide element
size conversion
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PCT/JP2021/035820
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French (fr)
Japanese (ja)
Inventor
祐美 村田
真悟 高野
宏佑 岡橋
優 片岡
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住友大阪セメント株式会社
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Priority to CN202180064083.9A priority Critical patent/CN116194828A/en
Publication of WO2022071381A1 publication Critical patent/WO2022071381A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/30—Optical coupling means for use between fibre and thin-film device
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
    • G02F1/035—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure

Definitions

  • the present invention relates to an optical waveguide element, an optical modulation device using the optical waveguide element, and an optical transmission device, and more particularly to an optical waveguide element including a rib-type optical waveguide and a reinforcing substrate that supports the optical waveguide.
  • optical waveguide elements such as optical modulators using a substrate having an electro-optical effect are often used.
  • due to the limited space of the base station it is necessary to increase the speed and size of the optical modulator.
  • the light confinement effect can be increased by miniaturizing the width of the optical waveguide, and as a result, the bending radius of the optical waveguide can be reduced and the size can be reduced.
  • LN lithium niobate
  • the mode field diameter (MFD) is about 10 ⁇ m
  • the bending radius of the optical waveguide is as large as several tens of mm, so that it is difficult to reduce the size.
  • the polishing technology of the substrate and the bonding technology of the substrate have improved, and it has become possible to make the LN substrate thinner, and the MFD of the optical waveguide has been researched and developed to be 3 ⁇ m or less and about 1 ⁇ m. As the MFD becomes smaller, the light confinement effect also becomes larger, so that the bending radius of the optical waveguide can also be made smaller.
  • SSC spot size converter
  • the taper-type waveguide whose spot size increases as the core portion of the optical waveguide expands has a high degree of difficulty in adjusting the refractive index of the core portion and the clad portion suitable for the spot size, and easily induces multi-mode.
  • the SSC of the element there is a limit to the design that can be used. Further, in order to convert to the required spot size, it is necessary to form a relatively long tapered portion, and there is a problem that it is difficult to miniaturize the optical waveguide element.
  • the tip of the rib-type optical waveguide 10 has a tapered shape 12 having a narrow width, and a core portion so as to surround the tip thereof.
  • the block portion 2 is arranged.
  • the refractive index of the block portion 2 is set lower than that of the optical waveguide 10, and the block body is made of an organic material (5) having a refractive index lower than that of the block portion 2 by about 0.01 to 0.03.
  • This organic material can be composed of a cured adhesive or the like.
  • This SSC has a tapered shape 12 of the optical waveguide 10 in a state of being covered with the block portion 2, so that the effective refractive index of the optical waveguide 10 is lowered and the confinement of light is weakened, so that light is emitted to the block portion 2. Mode shifts to realize an MFD larger than the optical waveguide 10.
  • FIG. 2 A cross-sectional view taken along the dotted lines AA'and BB' in FIG. 1 is shown in FIG. 2, and a cross-sectional view taken along the dotted line CC'in FIG. 1 is shown in FIG.
  • Reference numeral 1 is a thin plate (film body) of a material having an electro-optical effect such as lithium niobate, and the optical waveguide 10 is formed in a rib portion remaining after the thin plate is locally removed.
  • Reference numeral 3 is a reinforcing substrate that supports the thin plate 1 including the optical waveguide 10.
  • Reference numeral 4 is an upper substrate that serves as a reinforcing member when an optical fiber or an optical block is connected to the end face of the optical waveguide element.
  • Reference numeral 5 is an organically cured product obtained by curing the adhesive that joins the reinforcing substrate 3 and the upper substrate 4.
  • reference numeral 11 is a part of the thin plate 1 and indicates a portion remaining by etching when forming the tapered portion 12 of the optical waveguide.
  • the problem to be solved by the present invention is to solve the above-mentioned problems, and even when the spot size conversion unit is provided at the end of the optical waveguide, the upper substrate is attached in parallel to the reinforcing substrate, and the spot is formed.
  • an optical waveguide element that prevents damage to the size conversion portion, stabilizes the MFD by making the thickness of the adhesive layer uniform, and further makes the thermal stress uniform and suppresses the peeling of the upper substrate. be. Further, it is to provide an optical modulation device and an optical transmission device using the optical waveguide element.
  • the optical waveguide element of the present invention the optical modulation device using the optical waveguide element, and the optical transmission device have the following technical features.
  • an optical waveguide element provided with a rib-shaped optical waveguide formed of a material having an electro-optical effect and a reinforcing substrate supporting the optical waveguide
  • the optical waveguide propagates to one end of the optical waveguide.
  • a structure provided with a spot size conversion unit that changes the mode field diameter of the optical wave to be guided, arranged apart from the spot size conversion unit so as to sandwich the spot size conversion unit, and arranged on the reinforcing substrate.
  • the spot size conversion unit, the upper substrate arranged above the structure, and the height of the structure are set to be equal to or higher than the maximum height of the spot size conversion unit. It is characterized by.
  • the optical waveguide element according to (1) above is characterized in that the space formed by the spot size conversion unit, the structure, and the upper substrate is filled with an adhesive.
  • the optical waveguide element according to (2) above is characterized in that a groove for flowing the adhesive in the lateral direction is formed on the surface of the structure facing the upper substrate.
  • an adhesive outflow preventing means for suppressing the outflow of the adhesive in a direction away from the spot size conversion portion of the optical waveguide Is characterized by being arranged.
  • the surface of the optical waveguide opposite to the spot size conversion portion from the adhesive outflow prevention means is coated with the same material as the adhesive outflow prevention means. It is characterized by being done.
  • the refractive index of the material of the adhesive outflow prevention means is higher than the refractive index of the material constituting the rib-type optical waveguide. It is characterized by being low.
  • the optical waveguide element according to any one of (1) to (6) above is characterized in that the optical waveguide element is housed in a housing and includes an optical fiber for inputting or outputting a light wave to the optical waveguide. It is an optical modulation device.
  • the optical waveguide element includes a modulation electrode for modulating the light wave propagating in the optical waveguide, and a modulation signal input to the modulation electrode of the optical waveguide element is input. It is characterized by having an electronic circuit to be amplified inside the housing.
  • An optical transmission device comprising the optical modulation device according to (7) or (8) above, and an electronic circuit that outputs a modulation signal that causes the optical modulation device to perform a modulation operation.
  • the present invention is an optical waveguide element provided with a rib-type optical waveguide formed of a material having an electro-optical effect and a reinforcing substrate that supports the optical waveguide.
  • the optical waveguide is provided at one end of the optical waveguide.
  • a structure provided with a spot size conversion unit that changes the mode field diameter of the propagating light wave, arranged apart from the spot size conversion unit so as to sandwich the spot size conversion unit, and arranged on the reinforcing substrate.
  • a body is provided, and the height of the spot size conversion unit, the upper substrate arranged above the structure, and the structure is set to be equal to or higher than the maximum height of the spot size conversion unit. Therefore, the structure can support the upper substrate in parallel with the reinforcing substrate, and further, it is possible to suppress the upper substrate from coming into contact with the spot size conversion portion.
  • FIG. 1 is a cross-sectional view taken along the line AA'and BB' in FIG. 1. It is sectional drawing in the dotted line CC'in FIG. It is a top view which shows the 1st Embodiment which concerns on the optical waveguide element of this invention.
  • 4 is a cross-sectional view taken along the line AA'and BB' in FIG. 4. It is a top view which shows the 2nd Example which concerns on the optical waveguide element of this invention.
  • 6 is a cross-sectional view taken along the line AA'and BB' in FIG. It is a top view which shows the 3rd Example which concerns on the optical waveguide element of this invention.
  • FIG. 6 is a cross-sectional view taken along the dotted line CC'of FIG. It is a top view explaining the optical modulation device and the optical transmission apparatus of this invention.
  • the optical waveguide element of the present invention includes a rib-type optical waveguide 10 made of a material having an electro-optical effect and a reinforcing substrate 3 that supports the optical waveguide.
  • one end of the optical waveguide is provided with a spot size conversion unit 2 that changes the mode field diameter of the light wave propagating in the optical waveguide, and is separated from the spot size conversion unit so as to sandwich the spot size conversion unit.
  • the height of the structure S is provided with the structure S arranged on the reinforcing substrate 3, the spot size conversion unit 2, the upper substrate 4 arranged on the upper side of the structure S, and the height of the structure S.
  • H is characterized in that it is set to be equal to or higher than the maximum height of the spot size conversion unit 2.
  • the material 1 having an electro-optical effect used in the optical waveguide element of the present invention is a substrate such as lithium niobate (LN) or lithium tantalate (LT), PLZT (lead lanthanate titanate zirconate), or a material thereof.
  • a substrate such as lithium niobate (LN) or lithium tantalate (LT), PLZT (lead lanthanate titanate zirconate), or a material thereof.
  • Gas phase growth membranes and the like can be used.
  • various materials such as semiconductor materials and organic materials can also be used as optical waveguides.
  • a rib-type optical waveguide having a convex portion corresponding to the optical waveguide is formed on the substrate, such as etching a substrate 1 other than the optical waveguide or forming grooves on both sides of the optical waveguide. It is possible to use it. Further, the refractive index can be further increased by diffusing Ti or the like on the substrate surface by a thermal diffusion method, a proton exchange method, or the like in accordance with the rib-type optical waveguide.
  • the thickness of the substrate (thin plate) on which the optical waveguide 10 is formed is set to 10 ⁇ m or less, more preferably 5 ⁇ m or less, still more preferably 1 ⁇ m or less in order to achieve speed matching between the microwave and the light wave of the modulated signal.
  • the height of the rib-type optical waveguide is set to 4 ⁇ m or less, more preferably 3 ⁇ m or less, still more preferably 1 ⁇ m or less or 0.4 ⁇ m or less. It is also possible to form a vapor phase growth film on the reinforcing substrate 3 and process the film into the shape of an optical waveguide.
  • the substrate on which the optical waveguide is formed is adhesively fixed to the reinforcing substrate 3 by direct bonding or via an adhesive layer such as resin in order to increase the mechanical strength.
  • a material having a refractive index lower than that of the optical waveguide and the substrate on which the optical waveguide is formed and having a coefficient of thermal expansion close to that of the optical waveguide or the like for example, a substrate containing an oxide layer such as crystal or glass is suitable.
  • a composite substrate in which a silicon oxide layer is formed on a silicon substrate, which is abbreviated as SOI or LNOI, or a silicon oxide layer is formed on an LN substrate can also be used.
  • FIG. 4 and 5 are views for explaining the first embodiment of the optical waveguide element of the present invention
  • FIG. 4 is a plan view
  • FIG. 5 is a cross-sectional view (a) in the dotted line AA'of FIG. , It is a cross-sectional view (b) in the dotted line BB'.
  • FIGS. 4 and 5 show an example using the same spot size conversion unit (block body 2) as in FIGS. 1 to 3, but the present invention is not limited to these and is as shown in Patent Documents 1 to 3. It may be a spot size conversion unit having a tapered shape.
  • the feature of the optical waveguide element of the present invention is that, as shown in FIG. 4 or 5, a spot size conversion unit is arranged at one end of the optical waveguide, and the structure S so as to sandwich the spot size conversion unit (block body 2). Is to prepare.
  • This structure S has a refractive index lower than that of the optical waveguide 10, further is equal to or less than the refractive index of the block body 2, and more preferably has a refractive index lower than that of the organic cured product 5.
  • the refractive index of the structure S may be the same as that of the block body 2, but in that case, it is necessary to dispose a material having a low refractive index between the block body 2 and the structure S. ..
  • the refractive index when the refractive index is lower than that of the block body 2, the refractive index may be the same as that of the organic cured product 5 or the reinforcing substrate 3.
  • An ultraviolet (UV) curable resin can be used for the structure S. Further, it is a resin such as a thermoplastic resin or a thermosetting resin, and includes, for example, a polyamide resin, a melamine resin, a phenol resin, an amino resin, an epoxy resin, and the like, and as a low refractive index material, a rubber material. Alternatively, it can also contain a silicon oxide compound.
  • the structure S is, for example, a permanent resist. The structure S can be arranged by applying a photoresist made of a thermosetting resin as a material on the reinforcing substrate 3, patterning by a normal general photolithography process, and then heat-curing. ..
  • the upper substrate 4 is arranged on the upper side of the spot size conversion unit and the structure S.
  • a material having a refractive index and a coefficient of linear expansion similar to those of the reinforcing substrate 3 is used for the upper substrate.
  • the linear expansion coefficients match, it is possible to reduce defects such as the upper substrate coming off due to thermal stress, and an optical waveguide element having excellent heat resistance can be obtained.
  • an adhesive made of a UV curable resin, an acrylic resin, an epoxy resin, or the like can be used as the adhesive for joining the upper substrate 4 and the reinforcing substrate 3.
  • the feature of the optical waveguide element of the present invention is that the height H of the structure S is made higher than the maximum height of the spot size conversion unit, and the damage of the spot size conversion unit (block body 2) by the upper substrate 4 is suppressed. be.
  • FIGS. 6 and 7 are diagrams showing a second embodiment of the optical waveguide element of the present invention.
  • the feature of the second embodiment is that the convex portion S1 is provided on the upper surface (the surface facing the upper substrate) of the structure S, and a groove is formed between the adjacent convex portions. This groove contributes to efficiently draining the excess adhesive between the reinforcing substrate 3 and the upper substrate 4. Therefore, the distance between the reinforcing substrate 3 or the structure S and the upper substrate 4 can be maintained at a more uniform thickness.
  • the thickness of the layer formed by the organic cured product becomes constant, thereby stabilizing the size of the MFD of the light wave. Not only that, it is possible to realize SSC in which multi-mode is unlikely to occur.
  • the thickness H of the structure S (up to the upper surface of the protrusion S1) shown in FIG. 7 depends on the height of the spot size conversion portion, but when the adhesive is used as a part of the core portion, it is 1 ⁇ m or more. A range of 3.5 ⁇ m is set. Further, the area of the protrusion S1 in the total area of the upper surface of the structure S is set in the range of about 10% to 60%. This is because it is necessary to increase the mechanical strength of the protrusions to some extent, and if the gaps such as grooves become too narrow, problems such as air entering and being unable to be discharged occur. When the area of the upper surface of the protrusion S1 of the structure becomes large, the frictional force at the contact surface between the structure and the lid becomes high when the upper substrate is bonded, and the lid is fixed, which adversely affects the process workability.
  • FIGS. 8 and 9 are diagrams showing a third embodiment of the optical waveguide element of the present invention.
  • the feature of the third embodiment is that the adhesive outflow prevention means EB for suppressing the outflow of the adhesive (5) is arranged in the direction away from the spot size conversion unit (block body 2) of the optical waveguide 10. That is what you are doing.
  • the adhesive (5) spreads in the optical waveguide element so as to cover the surface of the optical waveguide 10, the place where the photodetector or the like required for configuring the optical modulator is installed is separated from the SSC unit. Since it is necessary to provide it in the light, there is a problem that it cannot be miniaturized. Further, if the adhesive adheres to a portion not designed for the optical waveguide, a part of the propagating light wave leaks out, or the light corresponding to the bending of the optical waveguide cannot be confined and the propagation loss becomes large.
  • the refractive index of the material constituting the adhesive outflow prevention means EB needs to be lower than the refractive index of the material constituting the optical waveguide 10.
  • the same material as the structure S is used to form the structure S. It is also possible to form an adhesive outflow prevention means by utilizing the forming process.
  • the surface of the optical waveguide 10 on the side of the spot size conversion unit (block body 2) or the side opposite to the block body 2 from the adhesive outflow prevention means EB is covered with the same material as the adhesive outflow prevention means EB. Is formed.
  • Such a covering portion plays a role of filling the rough surface of the optical waveguide 10, and by arranging the materials around the optical waveguide 10 in order of the coating layer CO, the adhesive outflow prevention means EB, and the block body 2. It also contributes to the reduction of propagation loss by suppressing sudden changes in the refractive index.
  • the optical waveguide element of the present invention is provided with a modulation electrode that modulates the light wave propagating in the optical waveguide 10, and is housed in the housing 8 as shown in FIG. Further, by providing an optical fiber (F) for inputting / outputting light waves to the optical waveguide, the optical modulation device MD can be configured.
  • the optical fiber is introduced into the housing through a through hole penetrating the side wall of the housing and is directly bonded to the optical waveguide element.
  • the optical waveguide element and the optical fiber can also be optically connected via a spatial optical system.
  • an optical transmission device OTA by connecting an electronic circuit (digital signal processor DSP) that outputs a modulation signal that causes the optical modulation device MD to perform a modulation operation to the optical modulation device MD. Since the modulation signal applied to the optical waveguide element needs to be amplified, the driver circuit DRV is used.
  • the driver circuit DRV or the digital signal processor DSP can be arranged outside the housing 8, but can also be arranged inside the housing 8. In particular, by arranging the driver circuit DRV in the housing, it is possible to further reduce the propagation loss of the modulated signal from the driver circuit.
  • the spot size conversion unit is provided at the end of the optical waveguide, the upper substrate is attached in parallel to the reinforcing substrate and the spot size conversion unit is damaged.
  • the MFD can be stabilized, and further, it becomes possible to provide an optical waveguide element in which the thermal stress is made uniform and the peeling of the upper substrate is suppressed. Further, it becomes possible to provide an optical modulation device and an optical transmission device using the optical waveguide element.

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Abstract

Provided is an optical waveguide element comprising a rib-shaped optical waveguide (10) formed of a material having an electrooptic effect and a reinforcement substrate (3) that supports the optical waveguide, wherein: a spot size conversion unit (2) that changes a mode field diameter of light waves propagating the optical waveguide is provided at one end of the optical waveguide; a structure (S) is disposed to be spaced apart from the spot size conversion unit so that the spot size conversion unit is interposed therebetween, and is disposed on the reinforcement substrate (3); and the spot size conversion unit (2) and an upper substrate (4) disposed above the structure (S) are set such that the height (H) of the structure (S) is greater than or equal to the maximum height of the spot size conversion unit (2).

Description

光導波路素子及びそれを用いた光変調デバイス並びに光送信装置Optical waveguide elements, optical modulation devices using them, and optical transmitters
　本発明は、光導波路素子及びそれを用いた光変調デバイス並びに光送信装置に関し、特に、リブ型の光導波路と、該光導波路を支持する補強基板とを備えた光導波路素子に関する。 The present invention relates to an optical waveguide element, an optical modulation device using the optical waveguide element, and an optical transmission device, and more particularly to an optical waveguide element including a rib-type optical waveguide and a reinforcing substrate that supports the optical waveguide.
　光計測技術分野又は光通信技術分野において、電気光学効果を有する基板を用いた光変調器などの光導波路素子が多用されている。特に、近年の情報通信量の増大に伴い、長距離の都市間又はデータセンター間に用いられる光通信の高速化及び大容量化が望まれている。しかも、基地局のスペースの制限もあり、光変調器の高速化と小型化が必要となっている。 In the field of optical measurement technology or optical communication technology, optical waveguide elements such as optical modulators using a substrate having an electro-optical effect are often used. In particular, with the increase in the amount of information communication in recent years, it is desired to increase the speed and capacity of optical communication used between long-distance cities or data centers. Moreover, due to the limited space of the base station, it is necessary to increase the speed and size of the optical modulator.
　光変調器の小型化には、光導波路の幅を狭くする微細化を施すことで、光の閉じ込め効果を大きくすることができ、結果として、光導波路の曲げ半径を小さくし、小型化が可能となる。例えば、電気光学効果を有するニオブ酸リチウム（ＬＮ）は、電気信号を光信号に変換する際に、歪みが少なく、光損失が少ないことから、長距離向け光変調器として用いられる。ＬＮ光変調器の従来の光導波路では、モードフィールド径（ＭＦＤ）は１０μｍ程度であり、光導波路の曲げ半径は数十ｍｍと大きいので、小型化が困難であった。 To reduce the size of the optical modulator, the light confinement effect can be increased by miniaturizing the width of the optical waveguide, and as a result, the bending radius of the optical waveguide can be reduced and the size can be reduced. Will be. For example, lithium niobate (LN) having an electro-optic effect is used as an optical modulator for a long distance because it has less distortion and less optical loss when converting an electric signal into an optical signal. In the conventional optical waveguide of the LN optical modulator, the mode field diameter (MFD) is about 10 μm, and the bending radius of the optical waveguide is as large as several tens of mm, so that it is difficult to reduce the size.
　近年、基板の研磨技術及び基板の貼り合わせ技術が向上し、ＬＮ基板の薄板化が可能となり、光導波路のＭＦＤも３μｍ以下、１μｍ程度が研究開発されている。ＭＦＤが小さくなるに従い、光の閉じ込め効果も大きくなるので、光導波路の曲げ半径もより小さくすることができる。 In recent years, the polishing technology of the substrate and the bonding technology of the substrate have improved, and it has become possible to make the LN substrate thinner, and the MFD of the optical waveguide has been researched and developed to be 3 μm or less and about 1 μm. As the MFD becomes smaller, the light confinement effect also becomes larger, so that the bending radius of the optical waveguide can also be made smaller.
　一方、光ファイバのＭＦＤである１０μｍφよりも小さいＭＦＤを有する微細光導波路を使用する場合には、光導波路素子に設けられた光導波路の端部（素子端面）と、光ファイバとを直接接合すると、大きな挿入損失が発生する。 On the other hand, when a fine optical waveguide having an MFD smaller than 10 μmφ, which is the MFD of an optical fiber, is used, the end of the optical waveguide provided in the optical waveguide element (element end face) is directly bonded to the optical fiber. , Large insertion loss occurs.
　このような不具合を解消するには、光導波路の端部にスポットサイズ変換部（スポットサイズコンバーター，ＳＳＣ）を配置することが考えらえる。一般的なＳＳＣは、二次元又は三次元に光導波路を拡大する、テーパー形状の光導波路部分を設けることである。参考までに、特許文献１乃至３には、テーパー型導波路の例が示されている。 In order to solve such a problem, it is conceivable to arrange a spot size converter (spot size converter, SSC) at the end of the optical waveguide. A general SSC is to provide a tapered optical waveguide portion that expands the optical waveguide in two or three dimensions. For reference, Patent Documents 1 to 3 show an example of a tapered waveguide.
　光導波路のコア部の拡大に伴いスポットサイズが拡大するテーパー型導波路は、スポットサイズに適したコア部とクラッド部の屈折率調整の難易度が高く、マルチモードを誘起し易いので、光導波路素子のＳＳＣとしては、使用可能なデザインに制限がある。さらに、必要なスポットサイズに変換するためには比較的長くテーパー部分を形成する必要が有り、光導波路素子の小型化が難しい課題があった。 The taper-type waveguide whose spot size increases as the core portion of the optical waveguide expands has a high degree of difficulty in adjusting the refractive index of the core portion and the clad portion suitable for the spot size, and easily induces multi-mode. As the SSC of the element, there is a limit to the design that can be used. Further, in order to convert to the required spot size, it is necessary to form a relatively long tapered portion, and there is a problem that it is difficult to miniaturize the optical waveguide element.
　さらに、本出願人においては、図１乃至３に示すようなＳＳＣを検討しているが、リブ型の光導波路１０の先端を幅が狭くなるテーパー形状１２とし、それを取り囲むようにコア部となるブロック部２を配置している。ブロック部２の屈折率は光導波路１０の屈折率よりも低く設定されており、さらに、ブロック部２よりも屈折率が０．０１～０．０３程度低い有機材料（５）で、ブロック体を取り囲んでいる。この有機材料は、接着剤を硬化したもの等で構成することが可能である。このＳＳＣは、ブロック部２で覆われた状態で光導波路１０のテーパー形状１２となることで、光導波路１０の実効屈折率が低下し、光の閉じ込めが弱くなることで、ブロック部２に光のモードが移行し、光導波路１０よりも大きなＭＦＤを実現している。 Further, the applicant is considering an SSC as shown in FIGS. 1 to 3, but the tip of the rib-type optical waveguide 10 has a tapered shape 12 having a narrow width, and a core portion so as to surround the tip thereof. The block portion 2 is arranged. The refractive index of the block portion 2 is set lower than that of the optical waveguide 10, and the block body is made of an organic material (5) having a refractive index lower than that of the block portion 2 by about 0.01 to 0.03. Surrounding. This organic material can be composed of a cured adhesive or the like. This SSC has a tapered shape 12 of the optical waveguide 10 in a state of being covered with the block portion 2, so that the effective refractive index of the optical waveguide 10 is lowered and the confinement of light is weakened, so that light is emitted to the block portion 2. Mode shifts to realize an MFD larger than the optical waveguide 10.
　図１の点線Ａ－Ａ’及びＢ－Ｂ’における断面図を図２に示し、図１の点線Ｃ－Ｃ’における断面図を図３に示している。符号１は、ニオブ酸リチウムなど電気光学効果を有する材料の薄板（膜体）であり、光導波路１０は、当該薄板を局所的に除去して残ったリブ部に形成されている。符号３は、光導波路１０を含む薄板１を支持する補強基板である。 A cross-sectional view taken along the dotted lines AA'and BB' in FIG. 1 is shown in FIG. 2, and a cross-sectional view taken along the dotted line CC'in FIG. 1 is shown in FIG. Reference numeral 1 is a thin plate (film body) of a material having an electro-optical effect such as lithium niobate, and the optical waveguide 10 is formed in a rib portion remaining after the thin plate is locally removed. Reference numeral 3 is a reinforcing substrate that supports the thin plate 1 including the optical waveguide 10.
　符号４は、光導波路素子の端面に光ファイバ又は光学ブロックを接続する際の補強部材となる上部基板である。符号５は、補強基板３と上部基板４とを接合する接着剤が硬化した有機硬化物である。また、符号１１は、薄板１の一部であり、光導波路のテーパー部１２を形成する際のエッチングで残留した部分を示している。 Reference numeral 4 is an upper substrate that serves as a reinforcing member when an optical fiber or an optical block is connected to the end face of the optical waveguide element. Reference numeral 5 is an organically cured product obtained by curing the adhesive that joins the reinforcing substrate 3 and the upper substrate 4. Further, reference numeral 11 is a part of the thin plate 1 and indicates a portion remaining by etching when forming the tapered portion 12 of the optical waveguide.
　特許文献１乃至３又は図１乃至３に示すＳＳＣにおいては、リブ型の光導波路だけでなく、該光導波路よりも厚みが大きく、補強基板３の表面から上側に大きく突出する特許文献３のテーパー部又は図２のブロック部２などが存在する。このように、補強基板３の表面から大きく突出した部分は、上部基板４を貼り付ける際に、当該突出部分の存在が、該上部基板を補強基板３の表面に対して平行に貼り合わせることを難しくする。しかも、上部基板４を接合のため上側から押し付けると、押圧力が当該突起部分に集中し、当該突起部分を破損するなどの不具合も生じる。また、上部基板４を平行に貼れず接着層厚が不均一になると、ＭＦＤが不均一になったり、熱応力により上部基板４が外れたりするなどの不具合も生じる。 In the SSCs shown in Patent Documents 1 to 3 or FIGS. 1 to 3, not only the rib-type optical waveguide but also the taper of Patent Document 3 which is thicker than the optical waveguide and greatly projects upward from the surface of the reinforcing substrate 3. There is a section, a block section 2 of FIG. 2, and the like. In this way, the portion that greatly protrudes from the surface of the reinforcing substrate 3 is such that when the upper substrate 4 is attached, the presence of the protruding portion causes the upper substrate to be attached in parallel to the surface of the reinforcing substrate 3. Make it difficult. Moreover, when the upper substrate 4 is pressed from above for joining, the pressing force is concentrated on the protruding portion, and problems such as damage to the protruding portion occur. Further, if the upper substrate 4 cannot be attached in parallel and the adhesive layer thickness becomes non-uniform, problems such as non-uniform MFD and detachment of the upper substrate 4 due to thermal stress occur.
特開２００６－２８４９６１号公報Japanese Unexamined Patent Publication No. 2006-288961 特開２００７－２６４４８７号公報Japanese Unexamined Patent Publication No. 2007-264487 国際公開ＷＯ２０１２／０４２７０８号International release WO2012 / 042708
　本発明が解決しようとする課題は、上述したような問題を解決し、光導波路の端部にスポットサイズ変換部を設けた場合でも、上部基板を補強基板に対して平行に貼り付け、該スポットサイズ変換部を破損することを防止し、接着層厚を均一化することによりＭＦＤが安定化され、更には、熱応力が均一化され上部基板の剥がれを抑制した光導波路素子を提供することである。さらには、その光導波路素子を用いた光変調デバイスと光送信装置を提供することである。 The problem to be solved by the present invention is to solve the above-mentioned problems, and even when the spot size conversion unit is provided at the end of the optical waveguide, the upper substrate is attached in parallel to the reinforcing substrate, and the spot is formed. By providing an optical waveguide element that prevents damage to the size conversion portion, stabilizes the MFD by making the thickness of the adhesive layer uniform, and further makes the thermal stress uniform and suppresses the peeling of the upper substrate. be. Further, it is to provide an optical modulation device and an optical transmission device using the optical waveguide element.
　上記課題を解決するため、本発明の光導波路素子及びそれを用いた光変調デバイス並びに光送信装置は、以下の技術的特徴を有する。
（１）　電気光学効果を有する材料で形成されるリブ型の光導波路と、該光導波路を支持する補強基板とを備えた光導波路素子において、該光導波路の一端には、該光導波路を伝搬する光波のモードフィールド径を変化するスポットサイズ変換部を備え、該スポットサイズ変換部を挟むように、該スポットサイズ変換部から離間して配置されると共に、該補強基板上に配置される構造体を備え、該スポットサイズ変換部と該構造体の上側に配置される上部基板と、該構造体の高さは、該スポットサイズ変換部の最大の高さ以上となるように設定されていることを特徴とする。 In order to solve the above problems, the optical waveguide element of the present invention, the optical modulation device using the optical waveguide element, and the optical transmission device have the following technical features.
(1) In an optical waveguide element provided with a rib-shaped optical waveguide formed of a material having an electro-optical effect and a reinforcing substrate supporting the optical waveguide, the optical waveguide propagates to one end of the optical waveguide. A structure provided with a spot size conversion unit that changes the mode field diameter of the optical wave to be guided, arranged apart from the spot size conversion unit so as to sandwich the spot size conversion unit, and arranged on the reinforcing substrate. The spot size conversion unit, the upper substrate arranged above the structure, and the height of the structure are set to be equal to or higher than the maximum height of the spot size conversion unit. It is characterized by.
（２）　上記（１）に記載の光導波路素子において、該スポットサイズ変換部、該構造体及び該上部基板が形成する空間には、接着剤が充填されていることを特徴とする。 (2) The optical waveguide element according to (1) above is characterized in that the space formed by the spot size conversion unit, the structure, and the upper substrate is filled with an adhesive.
（３）　上記（２）に記載の光導波路素子において、該構造体の該上部基板に対向する面には、該接着剤を横方向に流す溝が形成されていることを特徴とする。 (3) The optical waveguide element according to (2) above is characterized in that a groove for flowing the adhesive in the lateral direction is formed on the surface of the structure facing the upper substrate.
（４）　上記（２）又は（３）に記載の光導波路素子において、該光導波路の該スポットサイズ変換部から離れる方向に、該接着剤が流出するのを抑制するための接着剤流出防止手段が配置されていることを特徴とする。 (4) In the optical waveguide element according to (2) or (3) above, an adhesive outflow preventing means for suppressing the outflow of the adhesive in a direction away from the spot size conversion portion of the optical waveguide. Is characterized by being arranged.
（５）　上記（４）に記載の光導波路素子において、該接着剤流出防止手段から該スポットサイズ変換部と反対側の該光導波路の表面には、該接着剤流出防止手段と同じ材料で被覆されていることを特徴とする。 (5) In the optical waveguide element according to (4) above, the surface of the optical waveguide opposite to the spot size conversion portion from the adhesive outflow prevention means is coated with the same material as the adhesive outflow prevention means. It is characterized by being done.
（６）　上記（４）又は（５）のいずれかに記載の光導波路素子において、該接着剤流出防止手段の材料の屈折率は、前記リブ型の光導波路を構成する材料の屈折率よりも低いことを特徴とする。 (6) In the optical waveguide element according to any one of (4) or (5) above, the refractive index of the material of the adhesive outflow prevention means is higher than the refractive index of the material constituting the rib-type optical waveguide. It is characterized by being low.
（７）　上記（１）乃至（６）いずれかに記載の光導波路素子は、該光導波路素子は筐体内に収容され、該光導波路に光波を入力又は出力する光ファイバを備えることを特徴とする光変調デバイスである。 (7) The optical waveguide element according to any one of (1) to (6) above is characterized in that the optical waveguide element is housed in a housing and includes an optical fiber for inputting or outputting a light wave to the optical waveguide. It is an optical modulation device.
（８）　上記（７）に記載の光変調デバイスにおいて、該光導波路素子は該光導波路を伝搬する光波を変調するための変調電極を備え、該光導波路素子の変調電極に入力する変調信号を増幅する電子回路を該筐体の内部に有することを特徴とする。 (8) In the optical modulation device according to (7) above, the optical waveguide element includes a modulation electrode for modulating the light wave propagating in the optical waveguide, and a modulation signal input to the modulation electrode of the optical waveguide element is input. It is characterized by having an electronic circuit to be amplified inside the housing.
（９）　上記（７）又は（８）に記載の光変調デバイスと、該光変調デバイスに変調動作を行わせる変調信号を出力する電子回路とを有することを特徴とする光送信装置である。 (9) An optical transmission device comprising the optical modulation device according to (7) or (8) above, and an electronic circuit that outputs a modulation signal that causes the optical modulation device to perform a modulation operation.
　本発明は、電気光学効果を有する材料で形成されるリブ型の光導波路と、該光導波路を支持する補強基板とを備えた光導波路素子において、該光導波路の一端には、該光導波路を伝搬する光波のモードフィールド径を変化するスポットサイズ変換部を備え、該スポットサイズ変換部を挟むように、該スポットサイズ変換部から離間して配置されると共に、該補強基板上に配置される構造体を備え、該スポットサイズ変換部と該構造体の上側に配置される上部基板と、該構造体の高さは、該スポットサイズ変換部の最大の高さ以上となるように設定されているので、構造体が上部基板を補強基板に対して平行に支持することができ、さらに、上部基板がスポットサイズ変換部に接触することも抑制することが可能となる。 The present invention is an optical waveguide element provided with a rib-type optical waveguide formed of a material having an electro-optical effect and a reinforcing substrate that supports the optical waveguide. The optical waveguide is provided at one end of the optical waveguide. A structure provided with a spot size conversion unit that changes the mode field diameter of the propagating light wave, arranged apart from the spot size conversion unit so as to sandwich the spot size conversion unit, and arranged on the reinforcing substrate. A body is provided, and the height of the spot size conversion unit, the upper substrate arranged above the structure, and the structure is set to be equal to or higher than the maximum height of the spot size conversion unit. Therefore, the structure can support the upper substrate in parallel with the reinforcing substrate, and further, it is possible to suppress the upper substrate from coming into contact with the spot size conversion portion.
光導波路素子に使用されるスポットサイズ変換部の一例を示す平面図である。It is a top view which shows an example of the spot size conversion part used for an optical waveguide element. 図１の点線Ａ－Ａ’及びＢ－Ｂ’における断面図である。1 is a cross-sectional view taken along the line AA'and BB' in FIG. 1. 図１の点線Ｃ－Ｃ’における断面図である。It is sectional drawing in the dotted line CC'in FIG. 本発明の光導波路素子に係る第１の実施例を示す平面図である。It is a top view which shows the 1st Embodiment which concerns on the optical waveguide element of this invention. 図４の点線Ａ－Ａ’及びＢ－Ｂ’における断面図である。4 is a cross-sectional view taken along the line AA'and BB' in FIG. 4. 本発明の光導波路素子に係る第２の実施例を示す平面図である。It is a top view which shows the 2nd Example which concerns on the optical waveguide element of this invention. 図６の点線Ａ－Ａ’及びＢ－Ｂ’における断面図である。6 is a cross-sectional view taken along the line AA'and BB' in FIG. 本発明の光導波路素子に係る第３の実施例を示す平面図である。It is a top view which shows the 3rd Example which concerns on the optical waveguide element of this invention. 図６の点線Ｃ－Ｃ’における断面図である。FIG. 6 is a cross-sectional view taken along the dotted line CC'of FIG. 本発明の光変調デバイス及び光送信装置を説明する平面図である。It is a top view explaining the optical modulation device and the optical transmission apparatus of this invention.
　以下、本発明の光導波路素子について、好適例を用いて詳細に説明する。
　本発明の光導波路素子は、図４及び５に示すよう、電気光学効果を有する材料で形成されるリブ型の光導波路１０と、該光導波路を支持する補強基板３とを備えた光導波路素子において、該光導波路の一端には、該光導波路を伝搬する光波のモードフィールド径を変化するスポットサイズ変換部２を備え、該スポットサイズ変換部を挟むように、該スポットサイズ変換部から離間して配置されると共に、該補強基板３上に配置される構造体Ｓを備え、該スポットサイズ変換部２と該構造体Ｓの上側に配置される上部基板４と、該構造体Ｓの高さＨは、該スポットサイズ変換部２の最大の高さ以上となるように設定されていることを特徴とする。 Hereinafter, the optical waveguide device of the present invention will be described in detail with reference to suitable examples.
As shown in FIGS. 4 and 5, the optical waveguide element of the present invention includes a rib-type optical waveguide 10 made of a material having an electro-optical effect and a reinforcing substrate 3 that supports the optical waveguide. In, one end of the optical waveguide is provided with a spot size conversion unit 2 that changes the mode field diameter of the light wave propagating in the optical waveguide, and is separated from the spot size conversion unit so as to sandwich the spot size conversion unit. The height of the structure S is provided with the structure S arranged on the reinforcing substrate 3, the spot size conversion unit 2, the upper substrate 4 arranged on the upper side of the structure S, and the height of the structure S. H is characterized in that it is set to be equal to or higher than the maximum height of the spot size conversion unit 2.
　本発明の光導波路素子に使用される電気光学効果を有する材料１は、ニオブ酸リチウム（ＬＮ）又はタンタル酸リチウム（ＬＴ）、ＰＬＺＴ（ジルコン酸チタン酸鉛ランタン）などの基板又は、これらの材料による気相成長膜などが利用可能である。
　また、半導体材料又は有機材料など種々の材料も光導波路として利用可能である。 The material 1 having an electro-optical effect used in the optical waveguide element of the present invention is a substrate such as lithium niobate (LN) or lithium tantalate (LT), PLZT (lead lanthanate titanate zirconate), or a material thereof. Gas phase growth membranes and the like can be used.
Further, various materials such as semiconductor materials and organic materials can also be used as optical waveguides.
　光導波路１０の形成方法としては、光導波路以外の基板１をエッチングしたり、光導波路の両側に溝を形成するなど、基板に光導波路に対応する部分を凸状としたリブ型の光導波路を利用することが可能である。さらに、リブ型の光導波路に合わせて、Ｔｉなどを熱拡散法又はプロトン交換法などで基板表面に拡散させることにより、屈折率をより高くすることも可能である。 As a method for forming the optical waveguide 10, a rib-type optical waveguide having a convex portion corresponding to the optical waveguide is formed on the substrate, such as etching a substrate 1 other than the optical waveguide or forming grooves on both sides of the optical waveguide. It is possible to use it. Further, the refractive index can be further increased by diffusing Ti or the like on the substrate surface by a thermal diffusion method, a proton exchange method, or the like in accordance with the rib-type optical waveguide.
　光導波路１０を形成した基板（薄板）の厚さは、変調信号のマイクロ波と光波との速度整合を図るため、１０μｍ以下、より好ましくは５μｍ以下、さらに好ましくは１μｍ以下に設定される。また、リブ型光導波路の高さは、４μｍ以下、より好ましくは３μｍ以下、さらに好ましくは１μｍ以下又は０．４μｍ以下に設定される。また、補強基板３の上に気相成長膜を形成し、当該膜を光導波路の形状に加工することも可能である。 The thickness of the substrate (thin plate) on which the optical waveguide 10 is formed is set to 10 μm or less, more preferably 5 μm or less, still more preferably 1 μm or less in order to achieve speed matching between the microwave and the light wave of the modulated signal. The height of the rib-type optical waveguide is set to 4 μm or less, more preferably 3 μm or less, still more preferably 1 μm or less or 0.4 μm or less. It is also possible to form a vapor phase growth film on the reinforcing substrate 3 and process the film into the shape of an optical waveguide.
　光導波路を形成した基板は、機械的強度を高めるため、直接接合又は樹脂等の接着層を介して、補強基板３に接着固定される。直接接合する補強基板３としては、光導波路及び光導波路を形成した基板よりも屈折率が低く、光導波路などと熱膨張率が近い材料、例えば水晶又はガラス等の酸化物層を含む基板が好適に利用される。ＳＯＩ、ＬＮＯＩと略されるシリコン基板上に酸化ケイ素層又はＬＮ基板上に酸化ケイ素層を形成した複合基板も利用可能である。 The substrate on which the optical waveguide is formed is adhesively fixed to the reinforcing substrate 3 by direct bonding or via an adhesive layer such as resin in order to increase the mechanical strength. As the reinforcing substrate 3 to be directly bonded, a material having a refractive index lower than that of the optical waveguide and the substrate on which the optical waveguide is formed and having a coefficient of thermal expansion close to that of the optical waveguide or the like, for example, a substrate containing an oxide layer such as crystal or glass is suitable. Used for. A composite substrate in which a silicon oxide layer is formed on a silicon substrate, which is abbreviated as SOI or LNOI, or a silicon oxide layer is formed on an LN substrate can also be used.
　図４及び５は、本発明の光導波路素子の第１の実施例を説明する図であり、図４は平面図、図５は、図４の点線Ａ－Ａ’における断面図（ａ）と、点線Ｂ－Ｂ’における断面図（ｂ）である。 4 and 5 are views for explaining the first embodiment of the optical waveguide element of the present invention, FIG. 4 is a plan view, and FIG. 5 is a cross-sectional view (a) in the dotted line AA'of FIG. , It is a cross-sectional view (b) in the dotted line BB'.
　図４及び５では、図１乃至３と同様のスポットサイズ変換部（ブロック体２）を用いた例を示しているが、本発明はこれらに限定されず、特許文献１乃至３に示すようなテーパー形状のスポットサイズ変換部であっても良い。 4 and 5 show an example using the same spot size conversion unit (block body 2) as in FIGS. 1 to 3, but the present invention is not limited to these and is as shown in Patent Documents 1 to 3. It may be a spot size conversion unit having a tapered shape.
　本発明の光導波路素子の特徴は、図４又は５に示すように、光導波路の一端にスポットサイズ変換部を配置し、当該スポットサイズ変換部（ブロック体２）を挟むように、構造体Ｓを備えることである。この構造体Ｓは、光導波路１０よりも低い屈折率を持ち、さらにはブロック体２の屈折率以下であり、より好ましくは、有機硬化物５よりも低い屈折率を有する。また、構造体Ｓの屈折率は、ブロック体２と同等の屈折率でもよいが、その場合にはブロック体２と構造体Ｓとの間に、低屈折率を有する材料を配置する必要がある。一方、ブロック体２よりも低い屈折率とした場合は、有機硬化物５又は補強基板３と同じ程度の屈折率であっても良い。構造体Ｓには、紫外線（ＵＶ）硬化樹脂が利用可能である。さらに、熱可塑性樹脂または熱硬化性樹脂等の樹脂であり、一例として、ポリアミド系樹脂、メラミン系樹脂、フェノール系樹脂、アミノ系樹脂、エポキシ系樹脂等を含み、低屈折率材として、ラバー材又は酸化ケイ素化合物を含むことも可能である。また、構造体Ｓは、例えば永久レジストである。熱硬化型の樹脂を材料とするフォトレジストを補強基板３上に塗布し、通常の一般的なフォトリソグラフィプロセスによってパターニングを行った後に熱硬化させることにより、構造体Ｓを配設することができる。 The feature of the optical waveguide element of the present invention is that, as shown in FIG. 4 or 5, a spot size conversion unit is arranged at one end of the optical waveguide, and the structure S so as to sandwich the spot size conversion unit (block body 2). Is to prepare. This structure S has a refractive index lower than that of the optical waveguide 10, further is equal to or less than the refractive index of the block body 2, and more preferably has a refractive index lower than that of the organic cured product 5. Further, the refractive index of the structure S may be the same as that of the block body 2, but in that case, it is necessary to dispose a material having a low refractive index between the block body 2 and the structure S. .. On the other hand, when the refractive index is lower than that of the block body 2, the refractive index may be the same as that of the organic cured product 5 or the reinforcing substrate 3. An ultraviolet (UV) curable resin can be used for the structure S. Further, it is a resin such as a thermoplastic resin or a thermosetting resin, and includes, for example, a polyamide resin, a melamine resin, a phenol resin, an amino resin, an epoxy resin, and the like, and as a low refractive index material, a rubber material. Alternatively, it can also contain a silicon oxide compound. Further, the structure S is, for example, a permanent resist. The structure S can be arranged by applying a photoresist made of a thermosetting resin as a material on the reinforcing substrate 3, patterning by a normal general photolithography process, and then heat-curing. ..
　スポットサイズ変換部及び構造体Ｓの上側には、上部基板４が配置される。上部基板には、補強基板３と同じ程度の屈折率及び線膨張係数を有する材料が利用される。線膨張係数が一致していると、上部基板が熱応力で外れるなど不具合を低減することが可能となり、耐熱性に優れた光導波路素子が得られる。上部基板４と補強基板３とを接合する接着剤には、ＵＶ硬化樹脂又は、アクリル系又はエポキシ系等の樹脂などによる接着剤が使用可能である。 The upper substrate 4 is arranged on the upper side of the spot size conversion unit and the structure S. For the upper substrate, a material having a refractive index and a coefficient of linear expansion similar to those of the reinforcing substrate 3 is used. When the linear expansion coefficients match, it is possible to reduce defects such as the upper substrate coming off due to thermal stress, and an optical waveguide element having excellent heat resistance can be obtained. As the adhesive for joining the upper substrate 4 and the reinforcing substrate 3, an adhesive made of a UV curable resin, an acrylic resin, an epoxy resin, or the like can be used.
　本発明の光導波路素子の特徴は、構造体Ｓの高さＨをスポットサイズ変換部の最大高さよりも高くし、上部基板４によるスポットサイズ変換部（ブロック体２）の破損を抑制することである。 The feature of the optical waveguide element of the present invention is that the height H of the structure S is made higher than the maximum height of the spot size conversion unit, and the damage of the spot size conversion unit (block body 2) by the upper substrate 4 is suppressed. be.
　図６及び７は、本発明の光導波路素子に係る第２の実施例を示す図である。第２の実施例の特徴は、構造体Ｓの上面（上部基板に対向する面）に、凸状部Ｓ１を設け、隣接する凸状部の間に溝を形成することである。この溝は、補強基板３と上部基板４との間にある余分な接着剤を効率的に排出することに寄与する。そのため、補強基板３又は構造体Ｓと上部基板４との間隔をより均一な厚さに維持することができる。 6 and 7 are diagrams showing a second embodiment of the optical waveguide element of the present invention. The feature of the second embodiment is that the convex portion S1 is provided on the upper surface (the surface facing the upper substrate) of the structure S, and a groove is formed between the adjacent convex portions. This groove contributes to efficiently draining the excess adhesive between the reinforcing substrate 3 and the upper substrate 4. Therefore, the distance between the reinforcing substrate 3 or the structure S and the upper substrate 4 can be maintained at a more uniform thickness.
　特に、有機硬化物５をスポットサイズ変換部（ＳＳＣ）のコア部の一部とする場合には、有機硬化物が形成する層の厚みが一定となることにより、光波のＭＦＤのサイズを安定化できるだけでなく、マルチモードが発生し難いＳＳＣを実現することが可能となる。 In particular, when the organic cured product 5 is used as a part of the core portion of the spot size conversion unit (SSC), the thickness of the layer formed by the organic cured product becomes constant, thereby stabilizing the size of the MFD of the light wave. Not only that, it is possible to realize SSC in which multi-mode is unlikely to occur.
　図７に示す構造体Ｓ（突起部Ｓ１の上面まで）の厚さＨは、スポットサイズ変換部の高さにも依存するが、接着剤をコア部の一部として利用する場合は、１μｍ～３．５μｍの範囲が設定される。また、構造体Ｓの上面の全面積に占める突起部Ｓ１の面積は、１０％から６０％程度の範囲に設定される。これは、突起部の機械的強度をある程度高くする必要があることと、溝等の隙間が狭くなり過ぎると、空気が入り込み排出できないなどの不具合を生じるためである。構造体の突起部Ｓ１の上面の面積が大きくなると上部基板を貼り合わせる際に、構造体とリッドとの接触面における摩擦力が高くなりリッドが固着化され、プロセス作業性に悪影響を及ぼす。 The thickness H of the structure S (up to the upper surface of the protrusion S1) shown in FIG. 7 depends on the height of the spot size conversion portion, but when the adhesive is used as a part of the core portion, it is 1 μm or more. A range of 3.5 μm is set. Further, the area of the protrusion S1 in the total area of the upper surface of the structure S is set in the range of about 10% to 60%. This is because it is necessary to increase the mechanical strength of the protrusions to some extent, and if the gaps such as grooves become too narrow, problems such as air entering and being unable to be discharged occur. When the area of the upper surface of the protrusion S1 of the structure becomes large, the frictional force at the contact surface between the structure and the lid becomes high when the upper substrate is bonded, and the lid is fixed, which adversely affects the process workability.
　図８及び９は、本発明の光導波路素子に係る第３の実施例を示す図である。第３の実施例の特徴は、光導波路１０のスポットサイズ変換部（ブロック体２）から離れる方向に、接着剤（５）が流出するのを抑制するための接着剤流出防止手段ＥＢが配置されていることである。 8 and 9 are diagrams showing a third embodiment of the optical waveguide element of the present invention. The feature of the third embodiment is that the adhesive outflow prevention means EB for suppressing the outflow of the adhesive (5) is arranged in the direction away from the spot size conversion unit (block body 2) of the optical waveguide 10. That is what you are doing.
　接着剤（５）が、光導波路１０の表面を覆うように光導波路素子内に広がると、光変調器を構成する場合に必要な光検出器などの設置する場所をＳＳＣ部よりも離れた場所に設ける必要が生じるため、小型化ができないなどの問題が生じる。また、光導波路の設計にない部分に接着剤が付着することで伝搬する光波の一部が漏出したり、光導波路の曲げに対応する光の閉じ込めが出来ず伝搬損失が大きくなる。 When the adhesive (5) spreads in the optical waveguide element so as to cover the surface of the optical waveguide 10, the place where the photodetector or the like required for configuring the optical modulator is installed is separated from the SSC unit. Since it is necessary to provide it in the light, there is a problem that it cannot be miniaturized. Further, if the adhesive adheres to a portion not designed for the optical waveguide, a part of the propagating light wave leaks out, or the light corresponding to the bending of the optical waveguide cannot be confined and the propagation loss becomes large.
　接着剤流出防止手段ＥＢを構成する材料の屈折率は、光導波路１０を構成する材料の屈折率よりも低いことが必要であり、特に、構造体Ｓと同じ材料を使用し、構造体Ｓを形成するプロセスを利用して接着剤流出防止手段を形成することも可能である。 The refractive index of the material constituting the adhesive outflow prevention means EB needs to be lower than the refractive index of the material constituting the optical waveguide 10. In particular, the same material as the structure S is used to form the structure S. It is also possible to form an adhesive outflow prevention means by utilizing the forming process.
　さらに、接着剤流出防止手段ＥＢからスポットサイズ変換部（ブロック体２）側又はブロック体２と反対側の光導波路１０の表面には、接着剤流出防止手段ＥＢと同じ材料で被覆する被覆部ＣＯが形成されている。このような被覆部は、光導波路１０の荒れた表面を埋める役割を果たすと共に、光導波路１０の周辺の材料を被覆層ＣＯ、接着剤流出防止手段ＥＢ、ブロック体２と順番に配置することにより、急激な屈折率変化を抑制することからも伝搬損失の低減に寄与する。 Further, the surface of the optical waveguide 10 on the side of the spot size conversion unit (block body 2) or the side opposite to the block body 2 from the adhesive outflow prevention means EB is covered with the same material as the adhesive outflow prevention means EB. Is formed. Such a covering portion plays a role of filling the rough surface of the optical waveguide 10, and by arranging the materials around the optical waveguide 10 in order of the coating layer CO, the adhesive outflow prevention means EB, and the block body 2. It also contributes to the reduction of propagation loss by suppressing sudden changes in the refractive index.
　本発明の光導波路素子は、光導波路１０を伝搬する光波を変調する変調電極を設け、図１０のように、筐体８内に収容される。さらに、光導波路に光波を入出力する光ファイバ（Ｆ）を設けることで、光変調デバイスＭＤを構成することができる。図１０では、光ファイバは、筐体の側壁を貫通する貫通孔を介して筐体内に導入し、光導波路素子に直接接合されている。光導波路素子と光ファイバとは、空間光学系を介して光学的に接続することも可能である。 The optical waveguide element of the present invention is provided with a modulation electrode that modulates the light wave propagating in the optical waveguide 10, and is housed in the housing 8 as shown in FIG. Further, by providing an optical fiber (F) for inputting / outputting light waves to the optical waveguide, the optical modulation device MD can be configured. In FIG. 10, the optical fiber is introduced into the housing through a through hole penetrating the side wall of the housing and is directly bonded to the optical waveguide element. The optical waveguide element and the optical fiber can also be optically connected via a spatial optical system.
　光変調デバイスＭＤに変調動作を行わせる変調信号を出力する電子回路（デジタル信号プロセッサーＤＳＰ）を、光変調デバイスＭＤに接続することにより、光送信装置ＯＴＡを構成することが可能である。光導波路素子に印加する変調信号は増幅する必要があるため、ドライバ回路ＤＲＶが使用される。ドライバ回路ＤＲＶ又はデジタル信号プロセッサーＤＳＰは、筐体８の外部に配置することも可能であるが、筐体８内に配置することも可能である。特に、ドライバ回路ＤＲＶを筐体内に配置することで、ドライバ回路からの変調信号の伝搬損失をより低減することが可能となる。 It is possible to configure an optical transmission device OTA by connecting an electronic circuit (digital signal processor DSP) that outputs a modulation signal that causes the optical modulation device MD to perform a modulation operation to the optical modulation device MD. Since the modulation signal applied to the optical waveguide element needs to be amplified, the driver circuit DRV is used. The driver circuit DRV or the digital signal processor DSP can be arranged outside the housing 8, but can also be arranged inside the housing 8. In particular, by arranging the driver circuit DRV in the housing, it is possible to further reduce the propagation loss of the modulated signal from the driver circuit.
　以上説明したように、本発明によれば、光導波路の端部にスポットサイズ変換部を設けた場合でも、上部基板を補強基板に対して平行に貼り付け、該スポットサイズ変換部を破損することを防止し、接着層厚を均一化することによりＭＦＤが安定化され、更には、熱応力が均一化され上部基板の剥がれを抑制した光導波路素子を提供することが可能となる。さらには、その光導波路素子を用いた光変調デバイスと光送信装置を提供することが可能となる。 As described above, according to the present invention, even when the spot size conversion unit is provided at the end of the optical waveguide, the upper substrate is attached in parallel to the reinforcing substrate and the spot size conversion unit is damaged. By preventing the above and making the thickness of the adhesive layer uniform, the MFD can be stabilized, and further, it becomes possible to provide an optical waveguide element in which the thermal stress is made uniform and the peeling of the upper substrate is suppressed. Further, it becomes possible to provide an optical modulation device and an optical transmission device using the optical waveguide element.
　１　光導波路を形成する基板（薄板，膜体）
　２　スポットサイズ変換部を構成するブロック体
　３　補強基板
　４　上部基板
　５　接着剤
　１０　光導波路
　Ｓ　構造体
　Ｓ１　突起部
　ＥＢ　接着剤流出防止手段
　ＣＯ　被覆部

  1 Substrate (thin plate, film body) forming an optical waveguide
2 Block body that constitutes the spot size conversion part 3 Reinforcing board 4 Upper board 5 Adhesive 10 Optical waveguide S structure S1 Protrusion part EB Adhesive outflow prevention means CO coating part

Claims (9)

  1. 　電気光学効果を有する材料で形成されるリブ型の光導波路と、該光導波路を支持する補強基板とを備えた光導波路素子において、
    　該光導波路の一端には、該光導波路を伝搬する光波のモードフィールド径を変化するスポットサイズ変換部を備え、
    　該スポットサイズ変換部を挟むように、該スポットサイズ変換部から離間して配置されると共に、該補強基板上に配置される構造体を備え、
    　該スポットサイズ変換部と該構造体の上側に配置される上部基板と、
    　該構造体の高さは、該スポットサイズ変換部の最大の高さ以上となるように設定されていることを特徴とする光導波路素子。     In an optical waveguide element provided with a rib-type optical waveguide formed of a material having an electro-optical effect and a reinforcing substrate supporting the optical waveguide.
    One end of the optical waveguide is provided with a spot size conversion unit that changes the mode field diameter of the light wave propagating in the optical waveguide.
    It is provided with a structure that is arranged apart from the spot size conversion unit so as to sandwich the spot size conversion unit and is arranged on the reinforcing substrate.
    The spot size conversion unit, the upper substrate arranged on the upper side of the structure, and
    An optical waveguide element characterized in that the height of the structure is set to be equal to or higher than the maximum height of the spot size conversion unit.
  2. 　請求項１に記載の光導波路素子において、該スポットサイズ変換部、該構造体及び該上部基板が形成する空間には、接着剤が充填されていることを特徴とする光導波路素子。 The optical waveguide element according to claim 1, wherein the space formed by the spot size conversion unit, the structure, and the upper substrate is filled with an adhesive.
  3. 　請求項２に記載の光導波路素子において、該構造体の該上部基板に対向する面には、該接着剤を横方向に流す溝が形成されていることを特徴とする光導波路素子。 The optical waveguide element according to claim 2, wherein a groove for flowing the adhesive in the lateral direction is formed on the surface of the structure facing the upper substrate.
  4. 　請求項２又は３に記載の光導波路素子において、該光導波路の該スポットサイズ変換部から離れる方向に、該接着剤が流出するのを抑制するための接着剤流出防止手段が配置されていることを特徴とする光導波路素子。 In the optical waveguide element according to claim 2 or 3, an adhesive outflow prevention means for suppressing the outflow of the adhesive is arranged in a direction away from the spot size conversion portion of the optical waveguide. An optical waveguide element characterized by.
  5. 　請求項４に記載の光導波路素子において、該接着剤流出防止手段から該スポットサイズ変換部と反対側の該光導波路の表面には、該接着剤流出防止手段と同じ材料で被覆されていることを特徴とする光導波路素子。 In the optical waveguide element according to claim 4, the surface of the optical waveguide opposite to the spot size conversion portion from the adhesive outflow preventing means is coated with the same material as the adhesive outflow preventing means. An optical waveguide element characterized by.
  6. 　請求項４又は５のいずれかに記載の光導波路素子において、該接着剤流出防止手段の材料の屈折率は、前記リブ型の光導波路を構成する材料の屈折率よりも低いことを特徴とする光導波路素子。 The optical waveguide element according to claim 4 or 5, characterized in that the refractive index of the material of the adhesive outflow prevention means is lower than the refractive index of the material constituting the rib-type optical waveguide. Optical waveguide element.
  7. 　請求項１乃至６いずれかに記載の光導波路素子は、該光導波路素子は筐体内に収容され、該光導波路に光波を入力又は出力する光ファイバを備えることを特徴とする光変調デバイス。 The optical waveguide element according to any one of claims 1 to 6 is an optical modulation device in which the optical waveguide element is housed in a housing and includes an optical fiber for inputting or outputting a light wave to the optical waveguide.
  8. 　請求項７に記載の光変調デバイスにおいて、該光導波路素子は該光導波路を伝搬する光波を変調するための変調電極を備え、該光導波路素子の変調電極に入力する変調信号を増幅する電子回路を該筐体の内部に有することを特徴とする光変調デバイス。 In the optical modulation device according to claim 7, the optical waveguide element includes a modulation electrode for modulating a light wave propagating in the optical waveguide, and an electronic circuit for amplifying a modulation signal input to the modulation electrode of the optical waveguide element. An optical modulation device comprising the inside of the housing.
  9. 　請求項７又は８に記載の光変調デバイスと、該光変調デバイスに変調動作を行わせる変調信号を出力する電子回路とを有することを特徴とする光送信装置。 An optical transmission device comprising the optical modulation device according to claim 7 or 8 and an electronic circuit that outputs a modulation signal that causes the optical modulation device to perform a modulation operation.
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