WO2023218578A1 - Optical switch - Google Patents

Optical switch Download PDF

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Publication number
WO2023218578A1
WO2023218578A1 PCT/JP2022/019993 JP2022019993W WO2023218578A1 WO 2023218578 A1 WO2023218578 A1 WO 2023218578A1 JP 2022019993 W JP2022019993 W JP 2022019993W WO 2023218578 A1 WO2023218578 A1 WO 2023218578A1
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waveguide
optical switch
input
mach
arm
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PCT/JP2022/019993
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French (fr)
Japanese (ja)
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裕士 藤原
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日本電信電話株式会社
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Priority to PCT/JP2022/019993 priority Critical patent/WO2023218578A1/en
Publication of WO2023218578A1 publication Critical patent/WO2023218578A1/en

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    • 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
    • G02F1/29—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 position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • G02F1/313—Digital deflection, i.e. optical switching in an optical waveguide structure

Definitions

  • the present invention relates to an optical switch, and more particularly to an optical switch that can change directions by controlling the refractive index using light.
  • An optical switch is an optical device that can switch the direction of light under external control.
  • a control method a method is known in which a heater integrated in a waveguide constituting an optical switch is driven to change the refractive index of the waveguide to realize a switching operation.
  • an optical switch that inputs a light pulse to a semiconductor optical amplifier (SOA) integrated in a waveguide and changes the refractive index to achieve a switching operation.
  • SOA semiconductor optical amplifier
  • a method is also known in which the direction of light is switched by driving an ultra-small mirror using MEMS (Micro Electro Mechanical Systems).
  • the former type of optical switch which performs switching operation using a heater or SOA, requires electric power to cause refractive index modulation each time the optical path is changed, and a certain amount of power is required to maintain the optical path after switching. It is necessary to continue supplying electricity.
  • initial optical characteristics may deviate from design values due to manufacturing errors, and in order to compensate for these manufacturing errors, it may be necessary to supply a constant amount of power even when the route is not switched.
  • the latter MEMS type optical switch is capable of a latch operation that supplies power only when switching directions (see, for example, Patent Documents 1 and 2).
  • Patent Documents 1 and 2 see, for example, Patent Documents 1 and 2).
  • An object of the present invention is to provide a latch-operated optical switch that requires power only during switching operation, which can be manufactured through a simple process, and which can compensate for manufacturing errors without requiring a constant power supply.
  • the purpose is to provide a switch.
  • the present invention includes a Mach-Zehnder interferometer formed on a plane light wave circuit and configured by a first waveguide and a second waveguide.
  • the optical switch includes grooves formed along the optical axis on both sides of the first arm of the Mach-Zehnder interferometer configured with the first waveguide, and a photosensitive resin is provided in the grooves.
  • visible light with a wavelength shorter than 550 nm is input into the first waveguide, and signal light is input into the second waveguide forming a second arm of the Mach-Zehnder interferometer. It is characterized by
  • FIG. 1 is a diagram showing the structure of an optical switch according to Embodiment 1 of the present invention
  • FIG. 2 is a diagram showing the structure of an optical switch according to Example 2 of the present invention
  • FIG. 3 is a diagram showing the structure of an optical switch according to Example 3 of the present invention
  • FIG. 4 is a diagram showing the transmission spectrum of the optical switch of Example 3
  • FIG. 5 is a diagram showing the structure of an optical switch according to Example 4 of the present invention.
  • the optical stitch of this embodiment is a Mach Zehnder Interferomter (MZI) that is formed on a planar lightwave circuit (PLC) and includes a first waveguide and a second waveguide. ).
  • MZI Mach Zehnder Interferomter
  • PLC planar lightwave circuit
  • the MZI has a structure in which a first directional coupler and a second directional coupler are connected by two arm waveguides.
  • a part of the cladding of one arm waveguide is replaced with photosensitive resin.
  • a visible light source with a wavelength shorter than 550 nm is connected to the input port of the first waveguide. Visible light input to the first waveguide changes the refractive index of the photosensitive resin filled in the cladding, changing the direction of the light.
  • the wavelength of the signal light input to the second waveguide, which is the other arm waveguide is assumed to be 1.3 ⁇ m to 1.6 ⁇ m.
  • the resin is selected from a material whose refractive index does not change at the wavelength of the signal light. Since the refractive index of the photosensitive resin that has changed due to the input of visible light is maintained even when the input of visible light is stopped, the optical switch of this embodiment can perform a latching operation.
  • the optical switch of this embodiment is an MZI composed of a standard optical waveguide, and the groove filled with photosensitive resin can be produced by a standard dry etching process. Therefore, the optical switch of this embodiment can be manufactured using a standard process for manufacturing optical waveguides, and can be easily realized without requiring any new equipment investment or process.
  • the optical switch described below is a one-input, two-output (1 ⁇ 2) switch, which can also be expanded to a 1 ⁇ N switch by connecting 1 ⁇ 2 switches in a cascade. In addition to latching the optical switch by inputting visible light, if you want to perform temporary switching, load a heater on one or both of the arm waveguides and change the refractive index using the thermo-optic effect. You may let them.
  • FIG. 1 shows the structure of an optical switch according to Example 1 of the present invention.
  • FIG. 1(a) is a perspective view seen from above, and
  • FIG. 1(b) is a sectional view taken along line B-B' in FIG. 1(a).
  • the optical switch of Example 1 is a 1 ⁇ 2 optical switch based on MZI.
  • the optical switch is an MZI formed on a PLC and configured by a first waveguide 21 and a second waveguide 22.
  • the MZI has a structure in which a first directional coupler 41 and a second directional coupler 42 are connected by two arm waveguides.
  • a visible light source with a wavelength of 405 nm is connected to the input port of the first waveguide 21, and a signal light source is connected to the input port of the second waveguide 22.
  • Grooves 31a and 31b for filling with photosensitive resin are formed in the arm waveguide constituted by the first waveguide 21.
  • the grooves 31a and 31b have a constant length along the optical axis direction on both sides of the first waveguide 21 so as to sandwich the first waveguide 21 therebetween.
  • the photosensitive resin filled in the grooves 31a and 31b is preferably a material that is transparent from near-infrared wavelengths to visible wavelengths, and whose refractive index changes with visible light having a wavelength shorter than 550 nm.
  • acrylic resin, methacrylic resin, epoxy resin, polycarbonate, polystyrene, silicone resin, polyester, fluororesin, polybutadiene, polyisoprene, polychloroprene, etc. can be used.
  • the grooves 31a and 31b have a so-called tapered structure in which the groove width changes along the optical axis direction to achieve adiabatic coupling. It is preferable.
  • the MZI type PLC can be manufactured, for example, by the following procedure.
  • the layers are deposited in sequence.
  • the refractive index difference ⁇ between the core and the cladding was 1.8%.
  • the core layer is processed using common photolithography and dry etching techniques to form the core of the optical waveguide.
  • Both the first and second waveguides have a core width of 5.3 ⁇ m in order to propagate signal light with a wavelength of 1.3 ⁇ m to 1.6 ⁇ m in a single mode. Thereafter, an overcladding layer 13 made of silica-based glass is deposited on the core to form a buried waveguide.
  • grooves 31a and 31b to be filled with photosensitive resin are formed.
  • the length of the grooves 31a and 31b in the optical axis direction is required to be such that the signal light can feel the change in the refractive index of the arm waveguide, and was set to 3000 ⁇ m in Example 1.
  • the distance between the grooves 31a, 31b and the first waveguide 21 is desirably narrow so that refractive index modulation by visible light can be performed efficiently, but in Example 1, it was set to 6.0 ⁇ m in consideration of manufacturing accuracy.
  • the width of the grooves 31a and 31b was set to 10 ⁇ m in consideration of the mode distribution of the signal light propagating through the core.
  • a photosensitive resin is filled and hardened by heat treatment. Thereafter, it is diced into chips, and optical fibers are connected to the input/output ports of the chips using fiber blocks or the like as necessary. In this way, the optical switch module is completed.
  • the manufactured optical switch module may not have a sufficient extinction ratio due to manufacturing errors such as fluctuations in core film thickness and deviations in core width due to etching.
  • the refractive index of the filled photosensitive resin can be changed and trimming can be performed. Specifically, visible light with a wavelength of 405 nm from a visible light source is input to the input port of the first waveguide 21, and signal light is input to the input port of the second waveguide 22. Simultaneously with visible light input, the optical intensity of the signal light output from the output port of the second waveguide 22 is measured. By stopping visible light input when the desired light intensity, ie, the desired extinction ratio, is reached, the transmission characteristics can be easily trimmed. The wavelength and optical power of the input visible light are changed as appropriate for each filled photosensitive resin.
  • FIG. 2 shows the structure of an optical switch according to Example 2 of the present invention.
  • FIG. 2(a) is a perspective view seen from the top
  • FIG. 2(b) is a sectional view taken along line B-B' in FIG. 2(a).
  • the same members as in the optical switch of Example 1 are given the same reference numerals.
  • the optical switch of Example 2 is a 1 ⁇ 2 optical switch based on MZI, and the difference from the optical switch of Example 1 is that the structure of the arm waveguide composed of the first waveguide 21 is different. .
  • the first waveguide 21 sandwiched between the grooves 31a and 31b is a narrow waveguide 21b that is narrower than the width of the front and rear waveguides, and the front and rear waveguides in the optical axis direction are tapered waveguides 21a and 21c.
  • This increases the amount of visible light propagating through the narrow waveguide 21b that leaks out from the core of the waveguide, so that the refractive index of the photosensitive resin can be efficiently changed.
  • the signal light propagating through the arm waveguide constituted by the first waveguide 21 also has an increased amount of light seeping out from the core of the waveguide, and is more susceptible to the influence of refractive index modulation, making it difficult to switch efficiently. Can be done.
  • the optical stitch of this embodiment is designed assuming switching of signal light with a wavelength of 1.3 ⁇ m to 1.6 ⁇ m. Therefore, when visible light is input to the first and second waveguides, higher-order modes are likely to occur. Therefore, in the third embodiment, a mode filter is added to suppress higher-order modes.
  • FIG. 3 shows the structure of an optical switch according to Example 3 of the present invention.
  • the mode filter 51 is inserted between the input port of the first waveguide 21 and the first directional coupler 41, and is connected to a narrow waveguide 51b and a tapered waveguide 51a connected back and forth in the optical axis direction. , 51c. If the width of the narrow waveguide 51b is narrowed down to about 0.9 ⁇ m, it is possible to eliminate the higher-order mode of input light with a wavelength of 405 nm.
  • FIG. 4 shows the transmission spectrum of the optical switch of Example 3.
  • a visible light source with a wavelength of 405 nm is connected to the input port of the first waveguide 21, and a signal light source with a wavelength of 1.55 ⁇ m is connected to the input port of the second waveguide 22.
  • the signal light output from the output port was observed.
  • the state before visible light is input to the input port of the first waveguide 21 is the ON state. Due to the latching operation of the optical switch, when visible light with an optical power of 30 mW is input to the input port of the first waveguide 21, it becomes OFF in about 5 seconds. As shown in FIG. 4, an extinction ratio of 20 dB or more can be ensured in both ON and OFF states. After this, it was confirmed that the OFF state continued even after the input of visible light was stopped.
  • FIG. 5 shows the structure of an optical switch according to Example 4 of the present invention.
  • 5(a) is a perspective view seen from the top
  • FIG. 5(b) is a sectional view taken along line B-B' in FIG. 5(a).
  • the same members as in the optical switch of Example 1 are given the same reference numerals.
  • the optical switch of Example 4 is a 1 ⁇ 2 optical switch based on MZI, and differs from the optical switch of Example 1 in the structure of the groove filled with photosensitive resin.
  • the grooves 32a to 32c are provided so as to cross the core of the arm waveguide composed of the first waveguide 21 perpendicularly to the optical axis.
  • Example 1-3 since the groove is provided in parallel with the arm waveguide, when the difference in refractive index between the core and the cladding is high, the input visible light is strongly confined in the core, and the refractive index of the photosensitive resin is A problem may arise in that it is not possible to change efficiently.
  • Example 4 since the photosensitive resin is filled across the arm waveguide, the refractive index of the resin can be easily changed even when the difference in refractive index is large.
  • the core of the waveguide is made of Ge-doped SiO 2 , but it may also be made of Zr-doped SiO 2 , Ti-doped SiO 2 , P-doped SiO 2 , or non-doped SiO 2 . Furthermore, instead of the photosensitive resin, Ge-doped SiO 2 , B-doped SiO 2 , or P-doped SiO 2 may be used.
  • the wavelength at which the switching operation is performed is in the 1.55 ⁇ m band, but for example, by using a configuration in which MZIs are cascaded in multiple stages (lattice filter), the operating wavelength can be designed with some degree of freedom.
  • each arm waveguide of the MZI cascaded in multiple stages may be provided with a groove or region for filling with photosensitive resin.

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  • Nonlinear Science (AREA)
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Abstract

The present invention provides a latch-operation optical switch that can be created using a simple process. Provided is an optical switch including a Mach-Zehnder interferometer that is formed upon a planar lightwave circuit and is composed of a first waveguide and a second waveguide, the optical switch comprising grooves that are formed along the optical axis on both sides of a first arm of the Mach-Zehnder interferometer formed by the first waveguide, wherein the grooves are filled with a photosensitive resin, visible light having a shorter wavelength than the wavelength 550 nm is input to the first waveguide, and signal light is input to the second waveguide, which forms a second arm of the Mach-Zehnder interferometer.

Description

光スイッチlight switch
　本発明は、光スイッチに関し、より詳細には、光による屈折率制御により方路を変更することができる光スイッチに関する。 The present invention relates to an optical switch, and more particularly to an optical switch that can change directions by controlling the refractive index using light.
　光スイッチは、外部からの制御により光の方路を切り替えることができる光デバイスである。制御方法としては、光スイッチを構成する導波路に集積されたヒータを駆動し、導波路の屈折率を変えて、スイッチング動作を実現する方法が知られている。また、導波路に集積された半導体増幅器（ＳＯＡ：Semiconductor Optical Amplifier）へ光パルスを入力し、屈折率を変えてスイッチング動作を実現する光スイッチも存在する。このような導波路型の光スイッチのほかに、ＭＥＭＳ（Micro Electro Mechanical Systems）により、超小型ミラーを駆動することにより、光の方路を切り替える方式も知られている。 An optical switch is an optical device that can switch the direction of light under external control. As a control method, a method is known in which a heater integrated in a waveguide constituting an optical switch is driven to change the refractive index of the waveguide to realize a switching operation. There is also an optical switch that inputs a light pulse to a semiconductor optical amplifier (SOA) integrated in a waveguide and changes the refractive index to achieve a switching operation. In addition to such a waveguide type optical switch, a method is also known in which the direction of light is switched by driving an ultra-small mirror using MEMS (Micro Electro Mechanical Systems).
　前者のヒータまたはＳＯＡによりスイッチング動作を行う光スイッチは、光の方路を切り替えるたびに、屈折率変調を起こすための電力が必要になり、切り替え後の方路を維持するためには、一定の電力を供給し続ける必要がある。加えて、作製誤差等により初期の光学特性が設計値からずれることもあり、この作製誤差を補償するために方路を切り替えていない状態でも一定の電力を供給する必要がある場合も存在する。後者のＭＥＭＳ型の光スイッチは、方路の切り替え時のみ電力を供給するラッチ動作が可能である（例えば、特許文献１および２参照）。しかし、前者の導波路型の光スイッチと比較して、一般的に製造プロセスにおける負荷が高く、実動作においては挿入損失が大きいという課題があった。 The former type of optical switch, which performs switching operation using a heater or SOA, requires electric power to cause refractive index modulation each time the optical path is changed, and a certain amount of power is required to maintain the optical path after switching. It is necessary to continue supplying electricity. In addition, initial optical characteristics may deviate from design values due to manufacturing errors, and in order to compensate for these manufacturing errors, it may be necessary to supply a constant amount of power even when the route is not switched. The latter MEMS type optical switch is capable of a latch operation that supplies power only when switching directions (see, for example, Patent Documents 1 and 2). However, compared to the former waveguide type optical switch, there are problems in that the manufacturing process is generally more demanding and insertion loss is greater in actual operation.
特開２００５－２６６７１２号公報Japanese Patent Application Publication No. 2005-266712 特許第４４７６６４９号公報Patent No. 4476649
　本発明の目的は、スイッチング動作時のみ電力を必要とするラッチ動作の光スイッチであって、簡易なプロセスで作製することができ、一定の電力供給を必要とせずに作製誤差を補償可能な光スイッチを提供することにある。 An object of the present invention is to provide a latch-operated optical switch that requires power only during switching operation, which can be manufactured through a simple process, and which can compensate for manufacturing errors without requiring a constant power supply. The purpose is to provide a switch.
　本発明は、このような目的を達成するために、一実施態様は、平面光波回路上に形成された、第１の導波路および第２の導波路により構成されるマッハ・ツェンダー干渉計を含む光スイッチであって、前記第１の導波路で構成される前記マッハ・ツェンダー干渉計の第１のアームの両側に、光軸に沿って形成された溝を備え、前記溝に感光性樹脂が充填され、前記第１の導波路に波長５５０ｎｍより短波長の可視光が入力され、前記マッハ・ツェンダー干渉計の第２のアームを構成する前記第２の導波路に信号光が入力されることを特徴とする。 In order to achieve such an object, the present invention includes a Mach-Zehnder interferometer formed on a plane light wave circuit and configured by a first waveguide and a second waveguide. The optical switch includes grooves formed along the optical axis on both sides of the first arm of the Mach-Zehnder interferometer configured with the first waveguide, and a photosensitive resin is provided in the grooves. visible light with a wavelength shorter than 550 nm is input into the first waveguide, and signal light is input into the second waveguide forming a second arm of the Mach-Zehnder interferometer. It is characterized by
図１は、本発明の実施例１にかかる光スイッチの構造を示す図、FIG. 1 is a diagram showing the structure of an optical switch according to Embodiment 1 of the present invention, 図２は、本発明の実施例２にかかる光スイッチの構造を示す図、FIG. 2 is a diagram showing the structure of an optical switch according to Example 2 of the present invention, 図３は、本発明の実施例３にかかる光スイッチの構造を示す図、FIG. 3 is a diagram showing the structure of an optical switch according to Example 3 of the present invention, 図４は、実施例３の光スイッチの透過スペクトルを示す図、FIG. 4 is a diagram showing the transmission spectrum of the optical switch of Example 3, 図５は、本発明の実施例４にかかる光スイッチの構造を示す図である。FIG. 5 is a diagram showing the structure of an optical switch according to Example 4 of the present invention.
　以下、図面を参照しながら本発明の実施形態について詳細に説明する。本実施形態の光スティッチは、平面光波回路（Planer Lightwave Circuit：ＰＬＣ）上に形成された、第１の導波路および第２の導波路により構成されるマッハ・ツェンダー干渉計（Mach Zehnder Interferomter：ＭＺＩ）である。ＭＺＩは、第１の方向性結合器と第２の方向性結合器との間を、２本のアーム導波路により接続した構造である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The optical stitch of this embodiment is a Mach Zehnder Interferomter (MZI) that is formed on a planar lightwave circuit (PLC) and includes a first waveguide and a second waveguide. ). The MZI has a structure in which a first directional coupler and a second directional coupler are connected by two arm waveguides.
　本実施形態の光スティッチは、一方のアーム導波路のクラッドの一部が感光性樹脂に置換されている。一方のアーム導波路となる第１の導波路のクラッドの一部を感光性樹脂に置き換える場合、第１の導波路の入力ポートに波長５５０ｎｍより短波長の可視光光源が接続される。第１の導波路に入力される可視光によって、クラッドに充填された感光性樹脂の屈折率を変化させ、光の方路を変更する。他方のアーム導波路となる第２の導波路に入力される信号光の波長は１．３μｍから１．６μｍを想定しており、第１の導波路のクラッドの一部に充填された感光性樹脂は、信号光の波長では屈折率変化が起こらない材料が選択されている。可視光の入力で変化した感光性樹脂の屈折率は、可視光の入力を停止しても維持されるため、本実施形態の光スイッチは、ラッチ動作をすることが可能となる。 In the optical stitch of this embodiment, a part of the cladding of one arm waveguide is replaced with photosensitive resin. When replacing part of the cladding of the first waveguide, which is one of the arm waveguides, with a photosensitive resin, a visible light source with a wavelength shorter than 550 nm is connected to the input port of the first waveguide. Visible light input to the first waveguide changes the refractive index of the photosensitive resin filled in the cladding, changing the direction of the light. The wavelength of the signal light input to the second waveguide, which is the other arm waveguide, is assumed to be 1.3 μm to 1.6 μm. The resin is selected from a material whose refractive index does not change at the wavelength of the signal light. Since the refractive index of the photosensitive resin that has changed due to the input of visible light is maintained even when the input of visible light is stopped, the optical switch of this embodiment can perform a latching operation.
　本実施形態の光スイッチは、標準的な光導波路で構成されたＭＺＩであり、感光性樹脂を充填する溝は、標準的なドライエッチングプロセスで作製可能である。従って、本実施形態の光スイッチは、光導波路を作製する標準的なプロセスで作製可能であり、新たな設備投資、プロセスを必要とせず簡易に実現することができる。以下で説明する光スイッチは、１入力２出力（１×２）スイッチであり、１×２スイッチをカスケードに接続することによって１×Ｎスイッチに拡張することもできる。また、可視光の入力による光スイッチのラッチ動作に加えて、一時的なスイッチングを行いたい場合は、アーム導波路の一方または双方にヒータを装荷し、熱光学効果を利用して屈折率を変化させてもよい。 The optical switch of this embodiment is an MZI composed of a standard optical waveguide, and the groove filled with photosensitive resin can be produced by a standard dry etching process. Therefore, the optical switch of this embodiment can be manufactured using a standard process for manufacturing optical waveguides, and can be easily realized without requiring any new equipment investment or process. The optical switch described below is a one-input, two-output (1×2) switch, which can also be expanded to a 1×N switch by connecting 1×2 switches in a cascade. In addition to latching the optical switch by inputting visible light, if you want to perform temporary switching, load a heater on one or both of the arm waveguides and change the refractive index using the thermo-optic effect. You may let them.
　本実施形態によれば、従来の標準的な光導波路作製プロセスにより、容易にラッチ動作可能な光スイッチを提供することができる。 According to this embodiment, it is possible to provide an optical switch that can easily perform a latching operation using a conventional standard optical waveguide manufacturing process.
　図１に、本発明の実施例１にかかる光スイッチの構造を示す。図１（ａ）は、上面から見た透視図であり、図１（ｂ）は、図１（ａ）のＢ－Ｂ’の断面図である。実施例１の光スイッチは、ＭＺＩをベースとした１×２光スイッチである。光スイッチは、ＰＬＣ上に形成された、第１の導波路２１および第２の導波路２２により構成されるＭＺＩである。ＭＺＩは、第１の方向性結合器４１と第２の方向性結合器４２との間を、２本のアーム導波路により接続した構造である。 FIG. 1 shows the structure of an optical switch according to Example 1 of the present invention. FIG. 1(a) is a perspective view seen from above, and FIG. 1(b) is a sectional view taken along line B-B' in FIG. 1(a). The optical switch of Example 1 is a 1×2 optical switch based on MZI. The optical switch is an MZI formed on a PLC and configured by a first waveguide 21 and a second waveguide 22. The MZI has a structure in which a first directional coupler 41 and a second directional coupler 42 are connected by two arm waveguides.
　第１の導波路２１の入力ポートには、波長４０５ｎｍの可視光光源が接続され、第２の導波路２２の入力ポートには、信号光の光源が接続される。第１の導波路２１で構成されるアーム導波路には、感光性樹脂を充填するための溝３１ａ，３１ｂが形成されている。溝３１ａ，３１ｂは、第１の導波路２１を挟むように、第１の導波路２１の両側に光軸方向に沿って一定の長さを有している。 A visible light source with a wavelength of 405 nm is connected to the input port of the first waveguide 21, and a signal light source is connected to the input port of the second waveguide 22. Grooves 31a and 31b for filling with photosensitive resin are formed in the arm waveguide constituted by the first waveguide 21. The grooves 31a and 31b have a constant length along the optical axis direction on both sides of the first waveguide 21 so as to sandwich the first waveguide 21 therebetween.
　溝３１ａ，３１ｂに充填される感光性樹脂は、近赤外波長から可視波長域まで透明であり、波長５５０ｎｍより短波長の可視光によって屈折率が変化する材料が好ましい。具体的には、アクリル系樹脂、メタクリル系樹脂、エポキシ系樹脂、ポリカーボネート、ポリスチレン、シリコーン系樹脂、ポリエステル、フッ素系樹脂、ポリブタジエン、ポリイソプレン、ポリクロロプレン等を用いることができる。溝が形成された領域における散乱、モードミスマッチによる損失を低減するため、溝３１ａ，３１ｂは、アディアバティック結合となるように、光軸方向に沿って溝の幅が変わる構造、いわゆるテーパ構造を有することが好ましい。 The photosensitive resin filled in the grooves 31a and 31b is preferably a material that is transparent from near-infrared wavelengths to visible wavelengths, and whose refractive index changes with visible light having a wavelength shorter than 550 nm. Specifically, acrylic resin, methacrylic resin, epoxy resin, polycarbonate, polystyrene, silicone resin, polyester, fluororesin, polybutadiene, polyisoprene, polychloroprene, etc. can be used. In order to reduce loss due to scattering and mode mismatch in the region where the grooves are formed, the grooves 31a and 31b have a so-called tapered structure in which the groove width changes along the optical axis direction to achieve adiabatic coupling. It is preferable.
　実施例１の光スイッチの作製方法について以下に説明する。ＭＺＩ型のＰＬＣは、例えば、次の手順で作製することができる。Ｓｉ基板１１上に厚さ２０μｍの石英系ガラスで構成されたアンダークラッド層１２と、ゲルマニウム（Ｇｅ）をドープすることにより屈折率を高めた厚さ４．５μｍの石英系ガラスで構成されたコア層とを順に堆積する。実施例１では、コアとクラッドの屈折率差Δは１．８％とした。一般的なフォトリソグラフィおよびドライエッチング技術により、コア層を加工し光導波路のコアを形成する。第１および第２の導波路ともに、波長１．３μｍから１．６μｍの信号光をシングルモードで伝搬させるため、コア幅は、５．３μｍである。その後、石英系ガラスで構成されたオーバークラッド層１３をコア上に堆積し、埋め込み型導波路を形成する。 A method for manufacturing the optical switch of Example 1 will be described below. The MZI type PLC can be manufactured, for example, by the following procedure. An underclad layer 12 made of silica-based glass with a thickness of 20 μm on a Si substrate 11, and a core made of quartz-based glass with a thickness of 4.5 μm whose refractive index is increased by doping with germanium (Ge). The layers are deposited in sequence. In Example 1, the refractive index difference Δ between the core and the cladding was 1.8%. The core layer is processed using common photolithography and dry etching techniques to form the core of the optical waveguide. Both the first and second waveguides have a core width of 5.3 μm in order to propagate signal light with a wavelength of 1.3 μm to 1.6 μm in a single mode. Thereafter, an overcladding layer 13 made of silica-based glass is deposited on the core to form a buried waveguide.
　次に、フォトリソグラフィとドライエッチング技術を用いて、感光性樹脂を充填する溝３１ａ，３１ｂを形成する。溝３１ａ，３１ｂの光軸方向の長さは、アーム導波路の屈折率変化を信号光が感じる程度必要であり、実施例１では３０００μｍとした。溝３１ａ，３１ｂと第１の導波路２１との間隔は、可視光による屈折率変調を効率よくできるように狭い方が望ましいが、実施例１では作製精度を考慮して６．０μｍとした。溝３１ａ，３１ｂの幅は、コアを伝搬する信号光のモード分布を考慮して１０μｍとした。溝３１ａ，３１ｂを形成した後、感光性樹脂を充填し、熱処理によって硬化させる。その後、ダイシングによってチップ化を行い、チップの入出力ポートに必要に応じて、ファイバブロック等を用いて光ファイバを接続する。このようにして、光スイッチモジュールが完成する。 Next, using photolithography and dry etching techniques, grooves 31a and 31b to be filled with photosensitive resin are formed. The length of the grooves 31a and 31b in the optical axis direction is required to be such that the signal light can feel the change in the refractive index of the arm waveguide, and was set to 3000 μm in Example 1. The distance between the grooves 31a, 31b and the first waveguide 21 is desirably narrow so that refractive index modulation by visible light can be performed efficiently, but in Example 1, it was set to 6.0 μm in consideration of manufacturing accuracy. The width of the grooves 31a and 31b was set to 10 μm in consideration of the mode distribution of the signal light propagating through the core. After forming the grooves 31a and 31b, a photosensitive resin is filled and hardened by heat treatment. Thereafter, it is diced into chips, and optical fibers are connected to the input/output ports of the chips using fiber blocks or the like as necessary. In this way, the optical switch module is completed.
　作製した光スイッチモジュールは、コアの膜厚揺らぎ、エッチングによるコア幅のずれ等の作製誤差により、十分な消光比が得られない場合がある。その場合、第１の導波路２１の入力ポートに可視光を入力することにより、充填した感光性樹脂の屈折率を変えて、トリミングすることができる。具体的には、第１の導波路２１の入力ポートには、可視光光源から波長４０５ｎｍの可視光を入力し、第２の導波路２２の入力ポートには信号光を入力する。可視光入力と同時に、第２の導波路２２の出力ポートから出力される信号光の光強度を測定する。所望の光強度、すなわち所望の消光比になった時点で可視光入力を停止することにより、容易に透過特性のトリミングが可能である。入力する可視光の波長、光パワーは充填した感光性樹脂ごとに適宜変更する。 The manufactured optical switch module may not have a sufficient extinction ratio due to manufacturing errors such as fluctuations in core film thickness and deviations in core width due to etching. In that case, by inputting visible light into the input port of the first waveguide 21, the refractive index of the filled photosensitive resin can be changed and trimming can be performed. Specifically, visible light with a wavelength of 405 nm from a visible light source is input to the input port of the first waveguide 21, and signal light is input to the input port of the second waveguide 22. Simultaneously with visible light input, the optical intensity of the signal light output from the output port of the second waveguide 22 is measured. By stopping visible light input when the desired light intensity, ie, the desired extinction ratio, is reached, the transmission characteristics can be easily trimmed. The wavelength and optical power of the input visible light are changed as appropriate for each filled photosensitive resin.
　図２は、本発明の実施例２にかかる光スイッチの構造を示す。図２（ａ）は、上面から見た透視図であり、図２（ｂ）は、図２（ａ）のＢ－Ｂ’の断面図である。実施例１の光スイッチと同じ部材には、同じ符号を付与している。実施例２の光スイッチは、ＭＺＩをベースとした１×２光スイッチであり、実施例１の光スイッチとの相違点は、第１の導波路２１で構成されるアーム導波路の構造が異なる。 FIG. 2 shows the structure of an optical switch according to Example 2 of the present invention. FIG. 2(a) is a perspective view seen from the top, and FIG. 2(b) is a sectional view taken along line B-B' in FIG. 2(a). The same members as in the optical switch of Example 1 are given the same reference numerals. The optical switch of Example 2 is a 1×2 optical switch based on MZI, and the difference from the optical switch of Example 1 is that the structure of the arm waveguide composed of the first waveguide 21 is different. .
　溝３１ａ，３１ｂに挟まれた第１の導波路２１は、前後の導波路幅よりも細い細幅導波路２１ｂであり、光軸方向の前後はテーパ導波路２１ａ，２１ｃとなっている。これにより、細幅導波路２１ｂを伝搬する可視光が、導波路のコアからしみ出す光量が多くなるので、感光性樹脂の屈折率を効率よく変化させることができる。また、第１の導波路２１で構成されるアーム導波路を伝搬する信号光も、導波路のコアからしみ出す光量が多くなり、より屈折率変調の影響を受け易くなり、効率よくスイッチングさせることができる。 The first waveguide 21 sandwiched between the grooves 31a and 31b is a narrow waveguide 21b that is narrower than the width of the front and rear waveguides, and the front and rear waveguides in the optical axis direction are tapered waveguides 21a and 21c. This increases the amount of visible light propagating through the narrow waveguide 21b that leaks out from the core of the waveguide, so that the refractive index of the photosensitive resin can be efficiently changed. Further, the signal light propagating through the arm waveguide constituted by the first waveguide 21 also has an increased amount of light seeping out from the core of the waveguide, and is more susceptible to the influence of refractive index modulation, making it difficult to switch efficiently. Can be done.
　本実施形態の光スティッチは、波長１．３μｍから１．６μｍの信号光のスイッチングを想定して設計されている。従って、第１および第２の導波路に、可視光を入力すると高次モードが発生しやすい。そこで、実施例３では、高次モードを抑制するためのモードフィルタを追加する。 The optical stitch of this embodiment is designed assuming switching of signal light with a wavelength of 1.3 μm to 1.6 μm. Therefore, when visible light is input to the first and second waveguides, higher-order modes are likely to occur. Therefore, in the third embodiment, a mode filter is added to suppress higher-order modes.
　図３に、本発明の実施例３にかかる光スイッチの構造を示す。モードフィルタ５１は、第１の導波路２１の入力ポートと第１の方向性結合器４１との間に挿入され、細幅導波路５１ｂと、光軸方向の前後に接続されるテーパ導波路５１ａ，５１ｃとから構成されている。細幅導波路５１ｂの幅を０．９μｍ程度まで絞れば、波長４０５ｎｍの入力光の高次モードを除くことが可能である。 FIG. 3 shows the structure of an optical switch according to Example 3 of the present invention. The mode filter 51 is inserted between the input port of the first waveguide 21 and the first directional coupler 41, and is connected to a narrow waveguide 51b and a tapered waveguide 51a connected back and forth in the optical axis direction. , 51c. If the width of the narrow waveguide 51b is narrowed down to about 0.9 μm, it is possible to eliminate the higher-order mode of input light with a wavelength of 405 nm.
　図４に、実施例３の光スイッチの透過スペクトルを示す。第１の導波路２１の入力ポートに、波長４０５ｎｍの可視光光源を接続し、第２の導波路２２の入力ポートに波長１．５５μｍ帯の信号光光源を接続し、第１の導波路の出力ポートから出力される信号光を観測した。第１の導波路２１の入力ポートに可視光を入力する前の状態がＯＮ状態である。光スイッチのラッチ動作のため、光パワーは３０ｍＷの可視光を、第１の導波路２１の入力ポートに入力すると、５秒程度でＯＦＦ状態となる。図４に示すように、ＯＮ／ＯＦＦ状態のいずれの場合も消光比２０ｄＢ以上を確保することができる。この後、可視光の入力を停止した後も、ＯＦＦ状態が継続していることを確認した。 FIG. 4 shows the transmission spectrum of the optical switch of Example 3. A visible light source with a wavelength of 405 nm is connected to the input port of the first waveguide 21, and a signal light source with a wavelength of 1.55 μm is connected to the input port of the second waveguide 22. The signal light output from the output port was observed. The state before visible light is input to the input port of the first waveguide 21 is the ON state. Due to the latching operation of the optical switch, when visible light with an optical power of 30 mW is input to the input port of the first waveguide 21, it becomes OFF in about 5 seconds. As shown in FIG. 4, an extinction ratio of 20 dB or more can be ensured in both ON and OFF states. After this, it was confirmed that the OFF state continued even after the input of visible light was stopped.
　図５は、本発明の実施例４にかかる光スイッチの構造を示す。図５（ａ）は、上面から見た透視図であり、図５（ｂ）は、図５（ａ）のＢ－Ｂ’の断面図である。実施例１の光スイッチと同じ部材には、同じ符号を付与している。実施例４の光スイッチは、ＭＺＩをベースとした１×２光スイッチであり、実施例１の光スイッチとの相違点は、感光性樹脂を充填する溝の構造が異なる。 FIG. 5 shows the structure of an optical switch according to Example 4 of the present invention. 5(a) is a perspective view seen from the top, and FIG. 5(b) is a sectional view taken along line B-B' in FIG. 5(a). The same members as in the optical switch of Example 1 are given the same reference numerals. The optical switch of Example 4 is a 1×2 optical switch based on MZI, and differs from the optical switch of Example 1 in the structure of the groove filled with photosensitive resin.
　溝３２ａ－３２ｃは、第１の導波路２１で構成されるアーム導波路のコアを、光軸に対して垂直に横断するように設けられている。実施例１－３では、アーム導波路と並行に溝が設けられているので、コアとクラッドの屈折率差が高い場合、入力された可視光がコアに強く閉じ込められ、感光性樹脂の屈折率を効率的に変化させることができないという問題が生じうる。実施例４では、アーム導波路を横断するように感光性樹脂が充填されているため、屈折率差が大きい場合でも樹脂の屈折率を、容易に変化させることができる。 The grooves 32a to 32c are provided so as to cross the core of the arm waveguide composed of the first waveguide 21 perpendicularly to the optical axis. In Example 1-3, since the groove is provided in parallel with the arm waveguide, when the difference in refractive index between the core and the cladding is high, the input visible light is strongly confined in the core, and the refractive index of the photosensitive resin is A problem may arise in that it is not possible to change efficiently. In Example 4, since the photosensitive resin is filled across the arm waveguide, the refractive index of the resin can be easily changed even when the difference in refractive index is large.
　本実施形態では、導波路のコアをＧｅドープＳｉＯ２としたが、その他にＺｒドープＳｉＯ２、ＴｉドープＳｉＯ２、ＰドープＳｉＯ２、またはノンドープＳｉＯ２としてもよい。また、感光性樹脂の代わりに、ＧｅドープＳｉＯ２、ＢドープＳｉＯ２、ＰドープＳｉＯ２を用いてもよい。 In this embodiment, the core of the waveguide is made of Ge-doped SiO 2 , but it may also be made of Zr-doped SiO 2 , Ti-doped SiO 2 , P-doped SiO 2 , or non-doped SiO 2 . Furthermore, instead of the photosensitive resin, Ge-doped SiO 2 , B-doped SiO 2 , or P-doped SiO 2 may be used.
　本実施形態では、スイッチング動作を行う波長を１．５５μｍ帯としているが、例えば、ＭＺＩを多段にカスケード接続した構成（ラティスフィルタ）を用いることにより、動作波長をある程度自由に設計することができる。その場合、多段にカスケードしたＭＺＩの各アーム導波路に、感光性樹脂を充填するための溝または領域を設けてもよい。 In this embodiment, the wavelength at which the switching operation is performed is in the 1.55 μm band, but for example, by using a configuration in which MZIs are cascaded in multiple stages (lattice filter), the operating wavelength can be designed with some degree of freedom. In that case, each arm waveguide of the MZI cascaded in multiple stages may be provided with a groove or region for filling with photosensitive resin.

Claims (7)

  1. 　平面光波回路上に形成された、第１の導波路および第２の導波路により構成されるマッハ・ツェンダー干渉計を含む光スイッチであって、
    　前記第１の導波路で構成される前記マッハ・ツェンダー干渉計の第１のアームの両側に、光軸に沿って形成された溝を備え、
    　前記溝に感光性樹脂が充填され、前記第１の導波路に波長５５０ｎｍより短波長の可視光が入力され、
    　前記マッハ・ツェンダー干渉計の第２のアームを構成する前記第２の導波路に信号光が入力されることを特徴とする光スイッチ。     An optical switch including a Mach-Zehnder interferometer formed on a planar light wave circuit and configured by a first waveguide and a second waveguide,
    grooves formed along the optical axis on both sides of the first arm of the Mach-Zehnder interferometer configured with the first waveguide;
    The groove is filled with a photosensitive resin, and visible light with a wavelength shorter than 550 nm is input into the first waveguide,
    An optical switch characterized in that signal light is input to the second waveguide constituting the second arm of the Mach-Zehnder interferometer.
  2. 　平面光波回路上に形成された、第１の導波路および第２の導波路で構成されるマッハ・ツェンダー干渉計を備えた光スイッチであって、
    　前記第１の導波路で構成される前記マッハ・ツェンダー干渉計の第１のアームを横断するように形成された溝を備え、
    　前記溝に感光性樹脂が充填され、前記第１の導波路に波長５５０ｎｍより短波長の可視光が入力され、
    　前記マッハ・ツェンダー干渉計の第２のアームを構成する前記第２の導波路に信号光が入力されることを特徴とする光スイッチ。     An optical switch comprising a Mach-Zehnder interferometer formed on a planar light wave circuit and comprising a first waveguide and a second waveguide,
    a groove formed to cross a first arm of the Mach-Zehnder interferometer configured with the first waveguide;
    The groove is filled with a photosensitive resin, and visible light with a wavelength shorter than 550 nm is input into the first waveguide,
    An optical switch characterized in that signal light is input to the second waveguide constituting the second arm of the Mach-Zehnder interferometer.
  3. 　前記第１のアームは、前後にテーパ導波路が接続された細幅導波路を含むことを特徴とする請求項１に記載の光スイッチ。 The optical switch according to claim 1, wherein the first arm includes a narrow waveguide with tapered waveguides connected at the front and rear.
  4. 　前記第１の導波路の入力ポートに接続され、高次モードを抑制するモードフィルタをさらに備えたことを特徴とする請求項１または２に記載の光スイッチ。 The optical switch according to claim 1 or 2, further comprising a mode filter connected to the input port of the first waveguide and suppressing higher-order modes.
  5. 　前記感光性樹脂は、アクリル系樹脂、メタクリル系樹脂、エポキシ系樹脂、ポリカーボネート、ポリスチレン、シリコーン系樹脂、ポリエステル、フッ素系樹脂、ポリブタジエン、ポリイソプレン、またはポリクロロプレンのいずれかであることを特徴とする請求項１または２に記載の光スイッチ。 The photosensitive resin is characterized in that it is any one of acrylic resin, methacrylic resin, epoxy resin, polycarbonate, polystyrene, silicone resin, polyester, fluorine resin, polybutadiene, polyisoprene, or polychloroprene. The optical switch according to claim 1 or 2.
  6. 　前記感光性樹脂は、ＧｅドープＳｉＯ２、ＢドープＳｉＯ２、またはＰドープＳｉＯ２のいずれかであることを特徴とする請求項１または２に記載の光スイッチ。 3. The optical switch according to claim 1, wherein the photosensitive resin is one of Ge-doped SiO2 , B-doped SiO2 , or P-doped SiO2 .
  7. 　前記第１および第２の導波路のコアは、ＧｅドープＳｉＯ２、ＺｒドープＳｉＯ２、ＴｉドープＳｉＯ２、ＰドープＳｉＯ２、またはノンドープＳｉＯ２で構成されていることを特徴とする請求項１または２に記載の光スイッチ。 1 . The cores of the first and second waveguides are made of Ge-doped SiO 2 , Zr-doped SiO 2 , Ti-doped SiO 2 , P-doped SiO 2 , or non-doped SiO 2 . Or the optical switch according to 2.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06242335A (en) * 1993-02-16 1994-09-02 Nippon Telegr & Teleph Corp <Ntt> Consolidation type plane optical waveguide
JPH11507741A (en) * 1995-06-09 1999-07-06 コーニング インコーポレイテッド Mach-Zehnder switch
US20040071380A1 (en) * 2002-10-10 2004-04-15 International Business Machines Corporation Pretrimming of tunable finite response (FIR) filter
JP2006513458A (en) * 2002-08-02 2006-04-20 ウルトラドッツ・インコーポレイテッド Quantum dots, nanocomposites with quantum dots, optical devices with quantum dots, and related manufacturing methods
WO2017135436A1 (en) * 2016-02-04 2017-08-10 古河電気工業株式会社 Optical element and method for manufacturing same, and optical modulator

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06242335A (en) * 1993-02-16 1994-09-02 Nippon Telegr & Teleph Corp <Ntt> Consolidation type plane optical waveguide
JPH11507741A (en) * 1995-06-09 1999-07-06 コーニング インコーポレイテッド Mach-Zehnder switch
JP2006513458A (en) * 2002-08-02 2006-04-20 ウルトラドッツ・インコーポレイテッド Quantum dots, nanocomposites with quantum dots, optical devices with quantum dots, and related manufacturing methods
US20040071380A1 (en) * 2002-10-10 2004-04-15 International Business Machines Corporation Pretrimming of tunable finite response (FIR) filter
WO2017135436A1 (en) * 2016-02-04 2017-08-10 古河電気工業株式会社 Optical element and method for manufacturing same, and optical modulator

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