WO2016060263A1 - Coupleur optique intégré ayant une fonction de séparation/synthèse de polarisation - Google Patents

Coupleur optique intégré ayant une fonction de séparation/synthèse de polarisation Download PDF

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Publication number
WO2016060263A1
WO2016060263A1 PCT/JP2015/079367 JP2015079367W WO2016060263A1 WO 2016060263 A1 WO2016060263 A1 WO 2016060263A1 JP 2015079367 W JP2015079367 W JP 2015079367W WO 2016060263 A1 WO2016060263 A1 WO 2016060263A1
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mzi
wave plate
optical coupler
quarter
integrated optical
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PCT/JP2015/079367
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English (en)
Japanese (ja)
Inventor
川上　彰二郎
千葉　貴史
川嶋　貴之
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株式会社フォトニックラティス
有限会社オートクローニング・テクノロジー
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Priority to JP2016554144A priority Critical patent/JPWO2016060263A1/ja
Publication of WO2016060263A1 publication Critical patent/WO2016060263A1/fr

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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
    • G02B6/10—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
    • G02B6/126—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 using polarisation effects

Definitions

  • the present invention relates to a device technology in an optical communication system.
  • Digital coherent communication system is used to increase communication capacity per optical fiber against the background of rapid increase in information communication volume via the Internet.
  • this method separate signals are assigned to the two polarization components that propagate independently in the optical fiber. Therefore, the receiver needs to have a function to separate the two polarization components, and the transmitter has two polarization components. A function to superimpose spatially and supply to one fiber is required. The functions of these receivers and transmitters are collectively referred to as polarization diversity. Furthermore, in the communication system, downsizing of the transmitter and the receiver is an urgent issue for effective use of the space of the station building.
  • a light source, a light receiver, a modulator, an electronic circuit, etc. are usually arranged on a single plane, and they are connected in a straight or curved line with a waveguide. ing.
  • a waveguide In order to reduce the size of the device, it is necessary to bend the waveguide with a small radius of curvature.
  • the optical waveguide When the optical waveguide is bent, a part of the optical power is radiated due to the straightness inherent in the light, resulting in energy loss.
  • the diameter of the light beam is about 1 micron.
  • the diameter of the light beam is normally about 10 microns due to factors such as reducing loss during transmission, and this is caused by InP and silicon photonics. It is about an order of magnitude larger than the light beam diameter of the transceiver.
  • the smaller the MFD the smaller the allowable bending radius, which is advantageous for circuit miniaturization.
  • MFD relative refractive index difference
  • ⁇ relative refractive index difference
  • the relative refractive index difference ⁇ is usually 0.3%, and the MFD Is 4 to 5 microns, the relative refractive index difference ⁇ is about 2%. Further, the upper limit of the relative refractive index difference ⁇ that can be realized in the material technology is about 5% (MFD is about 3 microns). In the current planar optical circuit technology, the relative refractive index difference ⁇ is often 2.5% or less.
  • An optical fiber can propagate two polarization components at the same time, but the optical circuit and the optical functional device inside the transmitter and the receiver have different characteristics between the two polarization components, so they usually operate only in one polarization state. . Therefore, it is usually necessary to provide the following three functions between the optical fiber as the transmission path and the optical circuit in the transmitter / receiver.
  • SSC function spot size conversion
  • Two polarizations exist in one aperture on the optical fiber side, and polarization separation function (in the case of reception) that allocates one polarization to each of the two apertures on the circuit side, or the polarization in the opposite direction
  • Composite function for transmission.
  • the transmitter / receiver side often designs on the premise of only one polarization direction, and often wants to align the polarization direction after the polarization separation. Therefore, a polarization rotation function that rotates the polarized wave that is not desired on the circuit side of the two openings by 90 degrees and aligns it with the desired polarized light.
  • SSC function spot size conversion
  • Two polarizations exist in one aperture on the optical fiber side, and a polarization separation function that allocates one polarization to each of the two openings on the circuit side, or a polarization synthesis function in the opposite direction.
  • the transmitter / receiver side often designs on the premise of only one polarization direction, and often wants to align the polarization direction after the polarization separation. Therefore, a polarization rotation function that rotates the polarized wave that is not desired on the circuit side of the two openings by 90 degrees and aligns it with the desired polarized light.
  • a spot size conversion method has been developed.
  • the mode field diameter of the planar optical circuit matches that of the standard optical fiber.
  • two or more MZIs may be used in parallel, and the difficulty of “multiple elements, multiple mounting processes” described above further increases.
  • the present invention has been made in view of such problems, and the purpose thereof is a normal optical fiber (eg, MFD is about 10 ⁇ m) and a small-diameter waveguide (eg, MFD is about 1 ⁇ m).
  • the present invention is to provide a small integrated optical coupler having a polarization separation / rotation function that connects the two with low loss.
  • the present invention relates to an integrated optical coupler having one or more symmetrical MZIs (Mach-Zehnder interferometers).
  • the symmetric MZI is formed in an optical plane circuit and can output light input to one port from two ports or output light input to two ports from one port. Two connecting portions are provided.
  • the MZI having such a 1 ⁇ 2 connection portion is referred to as “1 ⁇ 2 MZI” or the like.
  • the main body of 1 ⁇ 2 MZI and the connection portion on the 2 port side are configured as waveguides having a relative refractive index difference of 0.8% to 10%.
  • the 1 ⁇ 2 MZI 1 port side connection is connected to a standard SMF (single mode optical fiber).
  • the 1 ⁇ 2 MZI 1-port side connection is a waveguide that matches the standard SMF beam diameter via the mode field conversion unit.
  • the integrated optical coupler of the present invention has a groove having a width of 20 microns or less arranged so as to cross two interference arms forming the MZI.
  • a quarter-wave plate made of a photonic crystal having slow axes (or fast axes) orthogonal to each other is inserted into the grooves on the optical paths of the two interference arms of the MZI.
  • This quarter wave plate is integrally formed over the entire MZI.
  • the lower limit of the width of the groove is not particularly limited as long as the quarter-wave plate can be inserted.
  • the quarter wave plate made of a photonic crystal has a thickness of 20 microns or less, and is an integral wave plate composed of two or more uniform regions. It is preferable that the angle difference between the slow axes (or fast axes) of the regions crossing the adjacent waveguides is 90 degrees.
  • the minimum of the thickness of a quarter wave plate is not specifically limited, For example, it is preferable that it is 0.5 micron or more or 1 micron or more.
  • the groove width is preferably 12.5 microns or less.
  • the quarter wave plate made of photonic crystal is preferably 6 microns or less in thickness.
  • a preferred embodiment of the present invention relates to an integrated optical coupler having a plurality of symmetrical MZIs (Mach-Zehnder interferometers).
  • Each of the plurality of MZIs is formed in an optical planar circuit and can output light input to one port from two ports or output light input to two ports from one port 1 ⁇ 2 connection part is provided.
  • the main body of each MZI and the connection portion on the two-port side are waveguides having a relative refractive index difference of 0.8% to 10%.
  • the connection portion on the 1-port side of each MZI is a waveguide that matches a standard SMF (single mode optical fiber) beam diameter via a mode field conversion portion.
  • the integrated optocoupler of the present invention has a first groove with a width of 12.5 microns or less arranged across two interference arms forming each MZI.
  • a quarter-wave plate made of a photonic crystal having slow axes (or fast axes) orthogonal to each other is inserted into the first groove on the optical paths of the two interference arms. This quarter-wave plate is integrally formed over a plurality of MZIs.
  • the integrated optical coupler of the present invention has a 2 ⁇ 2 coupler that connects two interference arms of each MZI and two arms constituting a connection portion on the 2-port side.
  • a second groove having a width of 14.5 microns or less is formed in both or at least one of the two arms opposite to the interference arm connected to the 2 ⁇ 2 coupler.
  • a half-wave plate made of a photonic crystal whose slow axis (or fast axis) is rotated in the direction of 45 degrees with respect to the plane perpendicular to which the two arms are formed is inserted into the second groove.
  • the half-wave plate is integrally formed throughout the plurality of MZIs.
  • the quarter-wave plate and the half-wave plate made of photonic crystals have thicknesses of 6 microns or less and 14 microns or less, respectively.
  • the minimum of the thickness of a quarter wave plate is not specifically limited, For example, it is preferable that it is 0.5 micron or more or 1 micron or more.
  • the lower limit of the thickness of the half-wave plate is not particularly limited, but is preferably 1 micron or more or 2 microns or more, for example.
  • the integrated optical coupler of the present invention preferably has one or more MZIs having a relative refractive index difference of 0.3% to 0.8% in the planar circuit.
  • two or more MZIs are formed in multiple rows in the parallel direction, and each of the grooves (first groove and second groove) It is preferable to cross two or more MZI interference arms.
  • the slow axis (fast axis) angle of a quarter-wave plate made of a photonic crystal may not be uniform and gradually change.
  • the angle difference of the quarter-wave plate is preferably 90 degrees.
  • the 1 ⁇ 2 symmetric MZI is converted into a 2 ⁇ 2 asymmetric 90 ° delay MZI (the phase amount of one of the two interfering arms is more polarized than the phase amount of the other arm).
  • MZI advanced by 90 degrees or delayed by 90 degrees.
  • the present invention may be an integrated optical coupler having one or more 2 ⁇ 2 asymmetric MZIs.
  • This MZI is formed in an optical planar circuit and has two ports on each of the input side and the output side, and two interference arms that connect the input side port and the output side port.
  • MZI can output light input to one port from two ports, or output light input to two ports from one port.
  • the MZI advances one phase amount of the two interference arms by 90 degrees or delays by 90 degrees from the phase amount of the other interference arm regardless of the polarization direction.
  • FIG. 4 shows an example of means for solving the problems according to the present invention.
  • the integrated optical coupler 20 is provided between a standard optical fiber (SMF-28 compatible) 21 and a thin waveguide receiver 22a or transmitter 22b.
  • SMF-28 compatible standard optical fiber
  • the diameter of the core of the optical fiber is about 10 microns
  • the width and height of the core of the thin waveguide is It is about 1 to 2 microns.
  • matching between the standard optical fiber 21 and the ultra high ⁇ plane optical circuit 25 and matching between the ultra high ⁇ plane optical circuit 25 and the small-diameter waveguide types 22a and 22b are performed. Utilizing this, the difference in mode field between the standard optical fiber 21 and the small-diameter waveguide 22 is converted and matched.
  • Polarization multiplexing / demultiplexing is performed by inserting wave plates 23 and 24 having a plurality of regions made of photonic crystals into grooves 26 provided on an ultrahigh ⁇ plane optical circuit.
  • the photonic crystal wave plates 23 and 24 are composited so as to have wave plates with different principal axis directions (including slow axis and fast axis) on one substrate. If necessary, wave plates having different main axis directions and different phase differences can be produced with a multi-segment structure.
  • wave plates having different main axis directions and different phase differences can be produced with a multi-segment structure.
  • the composite polarization rotation function can be realized by forming the second groove 26b in the MZI and inserting the half-wave plate 24 therein.
  • MFD Mode Field Diameter
  • MFD narrow waveguide
  • the standard optical fiber 21 and the ultra-high ⁇ plane optical circuit 25 are butt-connected.
  • the main part (main body) of the ultra-high ⁇ planar optical circuit 25 is composed of an ultra-high ⁇ planar optical circuit (super high delta, SHD) having an MFD of, for example, about 5 microns and is connected to the standard optical fiber 21.
  • a mode field matching portion 27 is provided in the vicinity of the terminal to be formed, matching with SHD at one end and matching with the standard optical fiber 21 at the other end.
  • the narrow device system is mainly composed of a narrow waveguide and has a spot size near the terminal to be connected in the fiber direction.
  • the beam diameter is expanded by a converter (SSC) 28 until it approximates SHD.
  • SSC converter
  • the functions of polarization separation / synthesis and polarization rotation are provided inside the SHD system.
  • the wave plate used in the SHD system it is preferable to use ultrathin wave plates 23 and 24 (a quarter wave plate 23 and a half wave plate) made of a photonic crystal.
  • planar light can be obtained by using a quarter-wave plate made of a photonic crystal as a quarter-wave plate that makes the polarization states of two lights propagating through two interference arms of MZI orthogonal.
  • the main part of the circuit can be configured as a waveguide (super high delta, SHD) having an MFD of about 5 microns, for example. Using such an SHD system to mode-match a narrow waveguide to a standard optical fiber system is much easier and more efficient than matching by SSC.
  • this wave plate is a composite wave plate integrated by photonic crystallization technology ( By using the size of several organic wavelength plates), it is possible to integrate in one behavior, which is advantageous for saving labor and reducing mounting angle errors.
  • the use of a photonic crystal ultrathin wave plate made of a-Si and SiO 2 as the wave plate used in the SHD system is extremely excellent because the diffraction loss can be minimized.
  • the MFD of light is about 10 microns, and two signals of vertical polarization and horizontal polarization are superimposed and transmitted.
  • a spot size conversion circuit 16 (SSC, spot size converter) is connected to an optical fiber 11 having an MFD of about 10 microns.
  • the spot size conversion circuit 16 converts the MFD from 10 microns to about 5 microns.
  • the light passing through the pot size conversion circuit 16 is guided to the 1 ⁇ 2 symmetric MZI circuit 14.
  • the MZI circuit 14 includes two interference arms 15a and 15b. A groove 12 is formed on the two interference arms 15a and 15b so as to cross both of them.
  • FIG. 2 is a cross-sectional view of the insertion portion of the quarter-wave plate 13.
  • the quarter-wave plate 13 is disposed on the optical path of each of the two interference arms 15a and 15b, and the principal axis directions with respect to the two interference arms 15a and 15b are orthogonal to each other.
  • the light that has passed through the 2 ⁇ 2 coupler 23 in the MZI of FIG. 1 is separated into a vertical polarization component and a horizontal polarization component, and the vertical polarization component and the horizontal polarization component are divided into two on the output side.
  • the two-port waveguides 18a and 18b are respectively reached.
  • the respective waveguide outputs are detected by the respective polarization receivers 20a and 20b.
  • the vertically polarized wave receiver 20a and the horizontally polarized wave receiver 20b are configured by a thin waveguide system suitable for miniaturization.
  • the MFD of the narrow waveguide system is about 1 to 2 microns.
  • the receivers 20a and 20b configured by a small-diameter waveguide system are connected to the SSC 21 located between the small-diameter waveguide 19 and the quartz-based high ⁇ waveguide with respect to the output side of the integrated optical coupler according to the present invention. Connected through.
  • the SSC 21 formed on the narrow waveguide side does not need to be matched with the MFD of the standard optical fiber 11 and can be converted to the MFD of an ultra-high ⁇ plane optical circuit that is about half of that, so that the conversion loss can be minimized. It is advantageous.
  • the integrated optical coupler of the present invention can be configured by inserting one integrated composite photonic crystal wave plate 13 into one groove once.
  • it is advantageous for reducing the number of operations, reducing the circuit size, and minimizing the mechanical error.
  • the number of wave plate mountings is only one, regardless of the number of MZIs.
  • the quarter-wave plate or the half-wave plate in the present invention is an optical element including a substrate and a photonic crystal formed on the substrate.
  • the substrate is divided into a plurality of regions at least on one side of the substrate.
  • the plurality of regions of the substrate have regions divided into a plurality of portions in the x-axis direction when one surface of the substrate is an xy plane.
  • a plurality of grooves each having a unique periodic pattern are formed, and there are at least two types of patterns as groove patterns formed in each region.
  • the two types of patterns can each have orthogonal principal axis directions.
  • the photonic crystal has a plurality of portions corresponding to a plurality of regions of the substrate and having a periodic structure reflecting a periodic pattern of each region on the substrate. Further, when one side of the substrate is an xy plane, the photonic crystal has a plurality of periodic layers formed of dielectrics having different refractive indexes in the layers adjacent to the z-axis direction in the z-axis direction. Have.
  • a photonic crystal it is preferable to use what was disclosed by such patent document 4. FIG.
  • FIG. 3 shows an integrated optical coupler 30 according to the second embodiment.
  • the configuration of the integrated optical coupler 30 located in the center of the drawing is basically the same as that in the first embodiment shown in FIG.
  • the two interference arms of MZI are coupled by a 2 ⁇ 2 coupler 37.
  • the coupler 37 is connected to two two-port side waveguides 38a and 38b (arms) on the opposite side to the side connected to the MZI.
  • a second groove 36b is formed in the two 2-port waveguides 38a and 38b so as to cross them.
  • a half-wave plate 34 made of an integral photonic crystal is inserted into the second groove 36b.
  • the half-wave plate 34 is disposed so that the polarizations of the light propagating rightward through the two-port waveguides 38a and 38b at the right end of the MZI are aligned. As shown in FIG. 3, the half-wave plate 34 is perpendicular to the plane perpendicular to which the two-port waveguide is formed with respect to one of the two two-port waveguides 38a and 38b. Thus, the slow axis (or the fast axis) is rotated in the direction of 45 degrees. In the present embodiment, the half-wave plate 34 is not rotated on the slow axis (or fast axis) with respect to the other of the two two-port waveguides 38a and 38b.
  • the half-wave plate 34 is formed of an integral photonic crystal, so that mounting performance and mechanical accuracy can be improved.
  • an ultrathin wave plate is a configuration using photonic crystals of amorphous silicon (a-Si) and silicon dioxide (SiO 2 ).
  • the substrate has a groove pattern formed linearly in a certain direction and a groove pattern formed linearly in a direction perpendicular to the pattern formed at least once.
  • an amorphous silicon (a-Si) layer and a silicon dioxide (SiO 2 ) layer are alternately stacked to form a photonic crystal.
  • the photonic crystal including the amorphous silicon (a-Si) layer and the silicon dioxide (SiO 2 ) layer has a periodic structure reflecting the groove pattern on the substrate.
  • amorphous silicon (a-Si) with a refractive index of 3.4 and a thickness of 120 nm and silicon dioxide (SiO 2 ) with a refractive index of 1.5 and a thickness of 120 nm are alternately stacked,
  • a periodic groove periodic stacked photonic crystal having a groove inclination of 40 degrees and an in-plane period of 0.5 microns is formed.
  • This periodic groove periodic stacked photonic crystal can be realized in which the phase constants of the TE wave and the TM wave are 0.84 ⁇ radians / micron and 0.77 ⁇ radians / micron, respectively.
  • the effective refractive index 2.6 is obtained as an average.
  • a half-wave plate (TE wave and TM wave phase difference of 180 degrees) can be realized with a thickness of 3.1 microns, and a quarter-wave plate (TE wave and TM wave phase difference of 90 degrees) This can be achieved with a half thickness of 1.6 microns.
  • This is compared with the structure using a niobium pentoxide (Nb 2 O 5 ) / silicon oxide (SiO 2 ) photonic crystal having a half-wave plate of about 12 microns and a quarter-wave plate of about 7 microns. The effect of reducing diffraction loss at the groove is great.
  • FIG. 9 shows the diffraction loss of the groove by comparing nick crystals.
  • the groove is determined by the material of the wave plate by the thickness of the element to be inserted + (when present) the substrate thickness + the adhesive thickness.
  • the diffraction loss takes into consideration the refractive index of the element, the refractive index of the substrate (1.5), and the refractive index of the adhesive (1.5). As shown in FIG.
  • a groove 36b is formed in the two waveguides 38a and 38b on the two-port side of the MZI so as to cross them, and the half-wave plate 34 is formed in the groove 36b.
  • the groove 36b or the half-wave plate 34 may be omitted.
  • a third embodiment for further enhancing the effect of the present invention will be described with reference to FIG.
  • the third embodiment mainly has the following features.
  • Photonic crystal wave plate is originally suitable for thinning, but a-Si / SiO 2 element is newly used to further enhance its characteristics
  • one of the two optical fibers 21 (for example, the upper side) is a transmission path for transmitting an optical signal that reaches the integrated optical coupler 20 and is input to the receiver 22a, and the other (for example, the lower side) ) Is a transmission path for sending out the output signal of the transmitter 22b after the signal is processed by an optical device (not shown) connected to the integrated optical coupler 20.
  • the integrated coupling circuit 20 for coupling each of the two optical fibers 21 to the narrow waveguide receiver 22a and the narrow waveguide transmitter 22b is the same as that shown in FIG. That is, in the integrated optical coupler 20, two MZIs are formed in parallel on the ultrahigh ⁇ planar optical circuit 25.
  • the MZI main body and the connection portion on the 2-port side are waveguides having a relative refractive index difference of 0.8% to 10%.
  • the connection portion on the one-port side of the MZI is a waveguide that matches the standard SMF (single mode optical fiber) beam diameter via the mode field conversion portion. For example, an optical signal input to a 1-port side connection is demultiplexed into two interference arms at the input end of the MZI, and after being transmitted through each interference arm, it is combined by a coupler disposed at the output end of the MZI. Waved.
  • a first groove 26a is formed so as to cross two interference arms constituting each MZI, that is, a total of four interference arms.
  • the first groove 26a includes a quarter-wave plate 23 (a TE wave and a TM wave having a phase difference of 90 degrees) made of photonic crystal of amorphous silicon (a-Si) and silicon dioxide (SiO 2 ). ) Is inserted.
  • the width of the first groove 26a may be 15 microns or less, but by using amorphous silicon for the quarter-wave plate 23, the width can be further reduced to 10 microns or less.
  • the width of the quarter wave plate 23 is not more than the first groove 26a and can be not more than 15 microns, and is particularly preferably not more than 10 microns.
  • the width of the quarter-wave plate 23 may be any width that can be fixed by being inserted into the first groove 26a.
  • the width of the quarter-wave plate 23 is the width of the first groove 26a. What is necessary is just to make it 0.5 micron or 1 micron narrower than the width.
  • the minimum of the thickness of a quarter wave plate is not specifically limited, For example, it is preferable that it is 0.5 micron or more or 1 micron or more.
  • the quarter wave plate 23 is disposed on the optical path of each of the two interference arms constituting the MZI. Further, for example, when the MZI is composed of a first interference arm and a second interference arm, the quarter-wave plate 23 has a region positioned on the optical path of the first interference arm and the first interference arm. The slow axis (or fast axis) of the region located on the optical path of the two interference arms is orthogonal to each other. In the embodiment shown in FIG. 4, a quarter-wave plate 23 made of an integral photonic crystal is disposed so as to straddle a total of four interference arms.
  • the quarter-wave plate 23 is formed by alternately forming mutually orthogonal regions such as a 0 ° region, a 90 ° region, a 0 ° region, and a 90 ° region. This combination may be formed by forming orthogonal regions such as a 45 ° region, a ⁇ 45 ° region, a 45 ° region, and a ⁇ 45 ° region.
  • the quarter-wave plate 23 is preferably formed of a photonic crystal of amorphous silicon (a-Si) and silicon dioxide (SiO 2 ) as described above. Thereby, the quarter wave plate 23 can be formed as an ultrathin film of 10 microns or less.
  • each MZI The two interference arms of each MZI are coupled to a 2 ⁇ 2 coupler.
  • two couplers are arranged in the planar optical circuit 25.
  • the coupler combines the optical signals guided through the two interference arms of each MZI and outputs them to the two-port-side waveguides 28a and 28b, or vice versa.
  • the two-port-side waveguides 28a and 28b are respectively arranged on the right side of the two MZIs, and a total of four waveguides 28a and 28b are formed.
  • a second groove 26b is formed so as to cross the four waveguides 28a and 28b.
  • An integral half-wave plate 24 made of a photonic crystal of amorphous silicon (a-Si) and silicon dioxide (SiO 2 ) is inserted into the second groove 26b.
  • the width of the second groove 26b may be 15 microns or less, but by using amorphous silicon for the half-wave plate 24, the width can be further reduced to 10 microns or less.
  • the width of the half-wave plate 24 is equal to or smaller than the second groove 26b and can be 15 microns or less, and is particularly preferably 10 microns or less.
  • the width of the half-wave plate 24 may be a width that can be fixed by being inserted into the second groove 26b.
  • the width of the half-wave plate 24 is the width of the second groove 26b. What is necessary is just to make it 0.5 micron or 1 micron narrower than the width.
  • the lower limit of the thickness of the half-wave plate is not particularly limited, but is preferably 1 micron or more or 2 microns or more, for example.
  • the half-wave plate 24 is disposed on the optical path of each of the two interference arms constituting the MZI. Further, for example, when the MZI is composed of a first interference arm and a second interference arm, the half-wave plate 24 has a region located on the optical path of the first interference arm and the first interference arm. In at least one of the regions located on the optical path of the two interference arms, a slow axis (or fast axis) forms a photonic crystal rotated in a 45-degree direction with respect to the insertion direction. In the embodiment shown in FIG. 4, the half-wave plate 24 formed of an integral photonic crystal is disposed so as to straddle a total of four waveguides 28a and 28b.
  • the half-wave plate 24 has a slow axis (or fast axis) in the insertion direction, such as a 45 ° region, a non-rotating region (0 ° region), a 45 ° region, and a non-rotating region (0 ° region). In contrast, the regions rotated in the direction of 45 degrees are alternately formed.
  • the half-wave plate 24 is preferably formed of a photonic crystal of amorphous silicon (aSi) and silicon dioxide (SiO 2 ) as described above. Thereby, the half-wave plate 24 can be formed as a very thin film of 10 microns or less.
  • the light traveling rightward through the two-port waveguides 28a and 28b at the right end of the MZI is arranged so that the polarization is aligned by the half-wave plate 24.
  • the radial waveguide transmitter 22b two independent signals having the same polarization coming from the right optical device (not shown) are orthogonalized by the half-wave plate 24. It is converted into a component and directed to a quarter-wave plate 23 that is integrally formed so as to straddle the two interference arms of MZI through a 2 ⁇ 2 coupler.
  • the half-wave plate 24 on the transmission side and the reception side is formed of an integral photonic crystal, so that mounting performance and machine accuracy can be improved.
  • an ultrathin wave plate is a configuration using photonic crystals of amorphous silicon (a-Si) and silicon dioxide (SiO 2 ).
  • the wave plate formed in this way can be molded to a width that can be fixed by being inserted into a groove of 10 microns or less (for example, 8 microns or more and less than 10 microns).
  • FIG. 5 is a simplified version of the embodiment shown in FIGS. 1 and 2.
  • the relative refractive index difference ⁇ of the planar optical circuit in the configuration of FIG. 1 is changed from 0.3% to 0.8%.
  • no spot size converter is provided between the standard optical fiber 51 and the planar optical circuit.
  • FIG. 6 shows a configuration in which MZIs 64 are arranged in multiples (four or more) in the parallel direction, and one groove 62 is provided across all the interference arms 65a and 65b of each MZI.
  • One quarter-wave plate 63 made of an integral photonic crystal is inserted into the one groove 62.
  • the photonic crystal type quarter-wave plate 63 a plurality of MZIs having polarization separation can be formed simultaneously by a single insertion operation.
  • the conventional technology uses a plurality of uniform wave plates (polyimide or quartz), when arranging the wave plates on a planar optical circuit, the main axis (slow axis, speed) of the wave plate is used.
  • one wavelength plate axis may be assigned to each interference arm 65 of MZI 64.
  • the lower interference arm and the upper interference arm of adjacent MZIs may be assigned in pairs so as to be in the same axial direction.
  • FIG. 7 shows a configuration in which the main axis (slow axis, fast axis) of the photonic crystal type quarter-wave plate 73 is gradually changed in the longitudinal direction (groove direction).
  • the principal axis (slow axis) of the wave plate is caused by the interference arms 75a and 75b of the MZI. , The same effect as rotating the fast axis) can be obtained.
  • the quarter-wave plate 73 can be adjusted.
  • the angle difference of the quarter-wave plate 73 of the photonic crystal type is 90 °. preferable.
  • FIG. 8 is obtained by replacing the 1 ⁇ 2 symmetric MZI 14 of FIG. 1 with a 2 ⁇ 2 asymmetric 90 ° delay MZI 84.
  • the 2 ⁇ 2 asymmetric 90 ° delay MZI 84 is an MZI in which one phase amount of two interfering arms is advanced by 90 degrees or delayed by 90 degrees with respect to the phase amount of the other arm regardless of the polarization direction.
  • the MZI 84 is formed in an optical plane circuit, and includes two ports on each of the input side and the output side, and two interference arms that connect the input side port and the output side port. Have.
  • the two interference arms are connected by 2 ⁇ 2 couplers 82 and 24 on the input side and the output side, respectively.
  • the MZI 84 can output light input to one port from two ports, or output light input to two ports from one port. Further, the MZI 84 advances one phase amount of the two interference arms by 90 degrees or delays 90 degrees with respect to the phase amount of the other interference arm regardless of the polarization direction. Even with such a configuration, substantially the same operation as that of the integrated optical coupler shown in FIG. 1 can be realized.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

Le problème décrit par l'invention est de pourvoir à un coupleur optique intégré compact qui présente une fonction de séparation de polarisation consistant à connecter une fibre optique normale et un guide d'ondes de petit diamètre avec une faible perte. La solution selon l'invention porte sur un coupleur optique intégré qui comprend un ou plusieurs MZI symétriques, chaque MZI étant formé dans un circuit optique plan et pourvu d'une partie de connexion 1 × 2. Une partie de connexion entre un corps principal et un côté à deux ports du MZI est un guide d'ondes ayant une différence d'indice de réfraction relative de 0,8 à 10 % inclus, et une partie de connexion sur un côté à port unique du MZI est un guide d'ondes conçu pour correspondre à un diamètre de faisceau de fibre optique monomode (SMF) standard. Le coupleur optique intégré comporte une rainure ayant une largeur de 20 microns ou moins, il est disposé de manière à croiser deux bras d'interférence qui forment le MZI, et une plaque en quart d'onde fabriquée à partir d'un cristal photonique et possédant des axes lents (ou axes rapides) perpendiculaires est introduite dans la rainure sur les chemins optiques respectifs des deux bras d'interférence. La plaque en quart d'onde est d'une seule pièce sur tout le MZI.
PCT/JP2015/079367 2014-10-17 2015-10-16 Coupleur optique intégré ayant une fonction de séparation/synthèse de polarisation WO2016060263A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0792326A (ja) * 1993-05-07 1995-04-07 Nippon Telegr & Teleph Corp <Ntt> 光波長板とその製造方法及びこれを用いた導波型光デバイス
JP2003207668A (ja) * 2002-01-11 2003-07-25 Nippon Telegr & Teleph Corp <Ntt> 偏波制御回路アレイおよびそれを用いた光回路
JP2011076049A (ja) * 2009-10-01 2011-04-14 Photonic Lattice Inc 光信号受信装置
WO2012102039A1 (fr) * 2011-01-26 2012-08-02 日本電信電話株式会社 Séparateur de faisceau de polarisation de type guide d'ondes
WO2012102041A1 (fr) * 2011-01-26 2012-08-02 日本電信電話株式会社 Séparateur de faisceau de polarisation de type guide d'ondes

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0792326A (ja) * 1993-05-07 1995-04-07 Nippon Telegr & Teleph Corp <Ntt> 光波長板とその製造方法及びこれを用いた導波型光デバイス
JP2003207668A (ja) * 2002-01-11 2003-07-25 Nippon Telegr & Teleph Corp <Ntt> 偏波制御回路アレイおよびそれを用いた光回路
JP2011076049A (ja) * 2009-10-01 2011-04-14 Photonic Lattice Inc 光信号受信装置
WO2012102039A1 (fr) * 2011-01-26 2012-08-02 日本電信電話株式会社 Séparateur de faisceau de polarisation de type guide d'ondes
WO2012102041A1 (fr) * 2011-01-26 2012-08-02 日本電信電話株式会社 Séparateur de faisceau de polarisation de type guide d'ondes

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