WO2020118625A1 - 光耦合结构、系统及光耦合结构的制备方法 - Google Patents

光耦合结构、系统及光耦合结构的制备方法 Download PDF

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Publication number
WO2020118625A1
WO2020118625A1 PCT/CN2018/120911 CN2018120911W WO2020118625A1 WO 2020118625 A1 WO2020118625 A1 WO 2020118625A1 CN 2018120911 W CN2018120911 W CN 2018120911W WO 2020118625 A1 WO2020118625 A1 WO 2020118625A1
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Prior art keywords
waveguide
lithium niobate
silica
core layer
layer
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PCT/CN2018/120911
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English (en)
French (fr)
Inventor
杨林
杨尚霖
张磊
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中国科学院半导体研究所
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Application filed by 中国科学院半导体研究所 filed Critical 中国科学院半导体研究所
Priority to JP2021532174A priority Critical patent/JP7163502B2/ja
Priority to EP18942939.2A priority patent/EP3896504A4/en
Priority to PCT/CN2018/120911 priority patent/WO2020118625A1/zh
Priority to US17/265,313 priority patent/US11513295B2/en
Publication of WO2020118625A1 publication Critical patent/WO2020118625A1/zh

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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
    • G02B6/24—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
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/0045—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
    • G02B6/0046—Tapered light guide, e.g. wedge-shaped light guide
    • 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
    • G02B6/12002—Three-dimensional structures
    • 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
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G02B6/136—Integrated optical circuits characterised by the manufacturing method by etching
    • 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
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4202—Packages, e.g. shape, construction, internal or external details for coupling an active element with fibres without intermediate optical elements, e.g. fibres with plane ends, fibres with shaped ends, bundles
    • G02B6/4203—Optical features
    • 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
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • 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
    • G02B2006/12035—Materials
    • G02B2006/1204—Lithium niobate (LiNbO3)
    • 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
    • G02B6/34—Optical coupling means utilising prism or grating

Definitions

  • the invention relates to the technical field of optical fiber communication and integrated optics, in particular to an optical coupling structure, a system and a preparation method of the optical coupling structure.
  • the cross-sectional area of the lithium niobate optical waveguide is on the order of square micrometers
  • the cross-sectional area of the single-mode optical fiber is on the order of one hundred square micrometers, because the cross-sectional area of the lithium niobate optical waveguide and the cross-sectional area of the single-mode optical fiber are not On an order of magnitude, the mode field between the lithium niobate optical waveguide and the single-mode fiber will not match. This leads to the problem of low coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber.
  • the present invention provides an optical coupling structure, system, and method for manufacturing the optical coupling structure, so as to at least partially solve the above technical problems.
  • an optical coupling structure including:
  • a lithium niobate optical waveguide formed on the substrate
  • a silica cladding layer formed on the peripheral wall of the silica core layer and surrounding the silica core layer.
  • the end face of the silicon dioxide core layer is rectangular or trapezoidal, and the end face area of the silicon dioxide core layer ranges from tens of square microns to hundreds of square microns.
  • the optical coupling structure further includes: an adhesive
  • the adhesive is provided on an end surface of the silica core layer and the silica cladding layer in the light transmission direction, and the refractive index of the adhesive is different from that of the silica core layer The difference in refractive index is less than 0.5.
  • an optical coupling system including: a first single-mode optical fiber, a second single-mode optical fiber, and the optical coupling structure;
  • the first end of the optical coupling structure is connected to the first single-mode optical fiber
  • the second end of the optical coupling structure is connected to the second single-mode optical fiber
  • both the first end and the second end are Located in the direction of light transmission.
  • the refractive index difference between the silica core layer and the silica cladding is ⁇ n, and the refractive index between the core region of the single-mode fiber and the cladding of the single-mode fiber The difference is ⁇ n', ⁇ n- ⁇ n' ⁇ 0.5.
  • the lithium niobate optical waveguide includes a rectangular parallelepiped waveguide located in the middle and a first quadrangular prism waveguide and a second quadrangular prism waveguide respectively located at both ends of the rectangular cuboid waveguide;
  • the first quadrangular prism waveguide is close to the first end, the end face of the first quadrangular prism waveguide away from the first single-mode optical fiber is connected to the end face of the rectangular parallelepiped waveguide, and the closeness of the first quadrangular prism waveguide
  • the distance between the end surface of the first single-mode optical fiber and the first end is greater than 0, and the cross-sectional dimension of the first quadrangular prism waveguide is away from the first single-mode optical fiber and close to the first single-mode optical fiber The direction of gradually becomes smaller;
  • the second quadrangular prism waveguide is close to the second end, the end surface of the second quadrangular prism waveguide away from the second single-mode optical fiber is connected to the end surface of the rectangular parallelepiped waveguide, and the second quadrangular prism waveguide is close to The distance between the end surface of the second single-mode optical fiber and the second end is greater than 0, and the cross-sectional dimension of the second quadrangular prism waveguide is away from the second single-mode optical fiber and close to the second single-mode optical fiber The direction gradually becomes smaller.
  • a method for manufacturing an optical coupling structure including:
  • Step S101 prepare the substrate
  • Step S102 forming a lithium niobate optical waveguide on the substrate
  • Step S103 forming a silica core layer surrounding the lithium niobate optical waveguide on the peripheral wall of the lithium niobate optical waveguide;
  • Step S104 forming a silica cladding layer surrounding the silica core layer on the peripheral wall of the silica core layer.
  • the substrate includes a quartz substrate layer, a buried silicon dioxide layer, and a lithium niobate thin film layer in sequence from bottom to top, and forming a lithium niobate optical waveguide on the substrate includes:
  • the lithium niobate thin film layer is etched by photolithography to form the lithium niobate optical waveguide.
  • forming a silicon dioxide core layer surrounding the lithium niobate optical waveguide on the peripheral wall of the lithium niobate optical waveguide includes:
  • the buried silicon dioxide layer forms the silicon dioxide core layer; the length of the silicon dioxide core layer in the light transmission direction is greater than the length of the lithium niobate optical waveguide in the light transmission direction.
  • forming a silica cladding layer surrounding the silica core layer on the peripheral wall of the silica core layer includes:
  • top silicon dioxide on the structure produced in step S103, the top silicon dioxide and the quartz substrate layer forming the silicon dioxide cladding; the length of the silicon dioxide core layer in the light transmission direction It is equal to the length of the silica cladding in the direction of light transmission.
  • optical coupling structure, system and method for preparing the optical coupling structure provided by the present invention have the following beneficial effects:
  • the optical coupling structure includes a silicon dioxide core layer formed on the peripheral wall of the lithium niobate optical waveguide and covering the lithium niobate optical waveguide; and a silicon dioxide core layer formed on the peripheral wall of the silicon dioxide core layer and wrapping the silicon dioxide core
  • the end face area of the silica core layer is larger than the cross-sectional area of the lithium niobate optical waveguide.
  • the end face area of the silica core layer is closer to the cross-sectional area of the single-mode optical fiber, which can be reduced due to
  • the optical loss problem caused by the mismatch of the mode field can therefore alleviate the technical problem of low coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber existing in the prior art, and achieve the improvement of the lithium niobate optical waveguide and the single-mode optical fiber The technical effect of the coupling efficiency.
  • the end face of the silica core layer is rectangular or trapezoidal, and the end face area of the silica core layer ranges from tens of square microns to hundreds of square microns, between the silica core layer and the silica cladding layer
  • the refractive index difference is ⁇ n
  • the refractive index difference between the core region of the single-mode fiber and the cladding of the single-mode fiber is ⁇ n', ⁇ n- ⁇ n' ⁇ 0.5, so that the optical coupling structure matches the mode field of the single-mode fiber .
  • the optical coupling structure further includes: an adhesive, which is provided on the end surfaces of the silica core layer and the silica cladding in the light transmission direction, and the refractive index of the adhesive and silica
  • the difference in the refractive index of the core layer is less than 0.5. Therefore, in the process of coupling the light from the optical coupling structure to the single-mode optical fiber, the Fresnel reflection loss due to the sudden change of the refractive index can be reduced, so the prior art can be alleviated.
  • the existing technical problem of low coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber achieves the technical effect of improving the coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber.
  • the cross-sectional size of the first quadrangular prism waveguide decreases gradually away from the first single-mode fiber to the first single-mode fiber; the cross-sectional dimension of the second quadrangular prism waveguide moves away from the second single-mode fiber to the second
  • the direction of the single-mode optical fiber gradually becomes smaller, so that the optical field can slowly transition from the lithium niobate optical waveguide to the silica waveguide, reducing the optical loss during the transition process, therefore, the niobic acid existing in the prior art can be alleviated
  • the technical problem of low coupling efficiency between the lithium optical waveguide and the single-mode optical fiber achieves the technical effect of improving the coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber.
  • a photolithography etching process is used to obtain an optical coupling structure to avoid the problems of high process difficulty and poor device consistency caused by the high-temperature proton exchange process used in the prior art to prepare lithium niobate devices. Therefore, it can be The process difficulty of preparing the optical coupling structure is reduced, and the consistency of the optical coupling structure is improved.
  • the grating in the process of preparing the optical coupling structure, the grating is not used, so that the problem of sensitivity to light polarization state caused by using the grating to prepare the optical coupling structure in the prior art can be avoided.
  • the light coupling structure insensitive to the polarization state of light reduces the time for the staff to use the light coupling structure and improves the efficiency of the staff.
  • FIG. 1 is a flowchart of a method for manufacturing an optical coupling structure provided by an embodiment of the present invention
  • FIG. 2 is a front view of the substrate before the lithium niobate optical waveguide provided by the embodiment of the present invention is manufactured;
  • FIG. 3 is a front view of the substrate after the lithium niobate optical waveguide provided by the embodiment of the present invention is manufactured;
  • FIG. 4 is a top view of the substrate after the lithium niobate optical waveguide provided by the embodiment of the present invention is manufactured;
  • FIG. 5 is a front view of a silica waveguide before the silica core layer provided by the embodiment of the present invention is manufactured
  • FIG. 6 is a front view of a silicon dioxide waveguide after the silicon dioxide core layer provided by an embodiment of the present invention is manufactured
  • FIG. 7 is a top view of the silica waveguide after the silica core layer provided by the embodiment of the present invention is manufactured;
  • FIG. 8 is a front view of an optical coupling structure provided by an embodiment of the present invention.
  • FIG. 9 is a first plan view of an optical coupling system provided by an embodiment of the present invention.
  • FIG. 10 is a second plan view of an optical coupling system provided by an embodiment of the present invention.
  • FIG. 11 is a third plan view of the optical coupling system provided by an embodiment of the present invention.
  • FIG. 12 is a fourth top view of the optical coupling system provided by an embodiment of the present invention.
  • An embodiment of the present invention provides an optical coupling structure, a system, and a method for preparing an optical coupling structure, which can alleviate the technical problem of low coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber existing in the prior art, and achieve improved niobium The technical effect of the coupling efficiency between the lithium acid optical waveguide and the single-mode optical fiber.
  • the method for manufacturing a light coupling structure may include the following steps.
  • Step S101 Prepare the substrate.
  • the substrate may include a quartz substrate layer 11, a buried silicon dioxide layer 12 and a lithium niobate thin film layer 13 in this order from bottom to top.
  • the material composition of the quartz substrate layer 11 may be pure silicon dioxide, or may be doped silicon dioxide.
  • the quartz substrate layer 11 can serve to support the entire optical coupling structure.
  • the buried silicon dioxide 12 may be deposited silicon dioxide that adjusts the deposition (deposition) process.
  • the material composition of the buried silicon dioxide 12 may be pure silicon dioxide, or may be doped silicon dioxide.
  • the lithium niobate thin film layer 13 can be bonded to the buried silicon dioxide layer 12 by a special process.
  • the material composition of the lithium niobate thin film layer 13 may be pure lithium niobate, or may be a doped lithium niobate material.
  • the refractive index range of the quartz substrate layer 11 for light with a wavelength of 1550 nm is about 1.4 to 1.6.
  • the buried silicon dioxide 12 has a refractive index range of about 1.4 to 1.6 for light at a wavelength of 1550 nanometers.
  • the refractive index of the buried silicon dioxide 12 is higher than the refractive index of the quartz substrate layer 11.
  • Step S102 forming a lithium niobate optical waveguide on the substrate.
  • step S102 may include: as shown in FIG. 3, etching the lithium niobate thin film layer 13 by photolithography to form the lithium niobate optical waveguide 14.
  • the lithium niobate optical waveguide 14 may include a rectangular parallelepiped waveguide 15 in the middle and a first quadrangular prism waveguide 161 and a second quadrangular prism waveguide 162 located at both ends of the rectangular parallelepiped waveguide 15 respectively.
  • Step S103 forming a silicon dioxide core layer surrounding the lithium niobate optical waveguide on the peripheral wall of the lithium niobate optical waveguide.
  • the end face of the silica core layer is rectangular or trapezoidal, and the end face area of the silica core layer ranges from tens of square microns to hundreds of square microns.
  • forming a silica core layer surrounding the lithium niobate optical waveguide on the peripheral wall of the lithium niobate optical waveguide may include the following steps:
  • a cap layer silica 17 is formed on the structure produced in step S102.
  • the cap silicon dioxide 17 may be pure silicon dioxide formed by a deposition (deposition) process, or doped silicon dioxide.
  • the cap layer silicon dioxide 17 covers the lithium niobate optical waveguide 14.
  • the difference between the refractive index of the cap layer silica 17 and the refractive index of the quartz substrate layer 11 can be set within 10%.
  • the refractive index of the capping silica 17 for light at a wavelength of 1550 nm is about 1.4 to 1.6.
  • the plasma-enhanced chemical vapor deposition PECVD process can be used to form the cap silicon dioxide 17, which uses silane and nitric oxide at 350 degrees Celsius to generate silicon dioxide.
  • the reaction equation is as follows: SiH 4 (gaseous state) + 2N 2 O( Gaseous)——SiO 2 (solid state)+2N 2 (gaseous state)+2H 2 (gaseous state).
  • the cap layer silica 17 is leveled.
  • the cap layer silicon dioxide may be planarized by chemical mechanical polishing.
  • the capping silicon dioxide after the planarization treatment a part of the capping silicon dioxide and a part of the buried silicon dioxide are removed by etching using photolithography to etch to the quartz Above the substrate layer 11, the etched cap silicon dioxide 19 and the etched buried silicon dioxide 18 form the silicon dioxide core layer. As shown in FIG. 7, the silicon dioxide core layer completely wraps the lithium niobate optical waveguide 14.
  • the mask is used for exposure and development, and the pattern of the mask is transferred to the photoresist. Then, the photoresist pattern is transferred to the capping silicon dioxide by etching.
  • the mixed gas of CF 4 and H 2 is selected as the etching gas of silicon dioxide, where the content of H 2 in the mixed gas is 50% of the volume of the mixed gas.
  • the CF 4 /H 2 mixed gas of this component The selectivity to silicon exceeds 40:1, and the etch selectivity is better.
  • CF 4 can produce fluorine atoms, which react with silicon dioxide to etch silicon dioxide. The reaction equation is as follows:
  • H 2 is to reduce the effect of reaction rate and silicon CF 4, CF 4 to improve the selective etching ratio of silica and silicon. This etching process etched all the way up to the quartz substrate layer.
  • the refractive index of the buried layer silica may be equal to the refractive index of the cap layer silica, and the refractive index of the buried layer silica may also be similar to the refractive index of the cap layer silica.
  • the refractive index of the cap layer silicon dioxide is higher than that of the quartz substrate layer.
  • the refractive index of the buried layer silica can be determined as the refractive index of the silica core layer. If the refractive index of the buried layer silica is close to that of the cap layer silica, then the average value of the refractive index of the buried layer silica and the cap layer silica can be determined as that of the silica core layer Refractive index.
  • the length of the silica core layer in the light transmission direction is greater than the length of the lithium niobate optical waveguide in the light transmission direction.
  • the silica core layer completely enclose the lithium niobate optical waveguide, but the end portion of the silica core layer does not wrap the lithium niobate optical waveguide, and the end portion of the silica core layer is completely silicon dioxide waveguide.
  • Step S104 forming a silica cladding layer surrounding the silica core layer on the peripheral wall of the silica core layer.
  • forming the silica cladding layer surrounding the silica core layer on the peripheral wall of the silica core layer includes: forming a top layer 2 on the structure produced in step S103
  • the silicon oxide 20, the top layer silicon dioxide 20 and the quartz substrate layer 11 form the silicon dioxide cladding, and the length of the silicon dioxide core layer in the light transmission direction is equal to the silicon dioxide cladding The length in the direction of light transmission.
  • the top silicon dioxide 20 may be pure silicon dioxide formed by a deposition (deposition) process, or doped silicon dioxide. Specifically, the top layer silicon dioxide 20 may be deposited silicon dioxide that adjusts the deposition process. Specifically, the refractive index of the top layer silica 20 for light at a wavelength of 1550 nanometers ranges from about 1.4 to 1.6.
  • the refractive index of the top silica can be equal to the refractive index of the quartz substrate layer, and the refractive index of the top silica can also be similar to the refractive index of the quartz substrate layer.
  • the refractive index of the top layer silica is lower than that of the buried layer silica.
  • the refractive index of the top layer silica is lower than that of the cap layer silica.
  • the refractive index of the top layer silica and the quartz substrate layer are lower than the refractive index of the silica core layer.
  • the refractive index of the top silica can be determined as the refractive index of the silica cladding. If the refractive index of the top silica is similar to the refractive index of the quartz substrate layer, the average value of the refractive index of the top silica and the refractive index of the quartz substrate layer can be determined as the refractive index of the silica cladding.
  • a silica core layer surrounding the lithium niobate optical waveguide is formed on the peripheral wall of the lithium niobate optical waveguide, and a silica core layer is formed on the peripheral wall of the silica core layer
  • the end face area of the silica core layer is larger than the cross-sectional area of the lithium niobate optical waveguide.
  • the end face area of the silica core layer is closer to the cross-sectional area of the single-mode fiber, which can reduce the The optical loss problem caused by the field mismatch, therefore, the technical problem of low coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber existing in the prior art can be alleviated to achieve an improvement between the lithium niobate optical waveguide and the single-mode optical fiber The technical effect of the coupling efficiency.
  • the photo-coupling structure is obtained by the photolithography etching process to avoid the problems of high process difficulty and poor device consistency caused by the high-temperature proton exchange process used in the prior art to prepare the lithium niobate device, so the preparation of the photo-coupling can be reduced
  • the technical difficulty of the structure improves the consistency of the optical coupling structure.
  • the grating In the process of preparing the optical coupling structure, the grating is not used, so the problem of sensitivity to light polarization caused by using the grating to prepare the optical coupling structure in the prior art can be avoided.
  • the sensitive optical coupling structure reduces the time for the staff to use the optical coupling structure and improves the efficiency of the staff.
  • optical coupling structure includes:
  • the substrate may include a quartz substrate layer 11, a buried silicon dioxide layer 12 and a lithium niobate thin film layer 13 in this order from bottom to top.
  • the lithium niobate optical waveguide 14 may include a rectangular parallelepiped waveguide 15 in the middle and a first quadrangular prism waveguide 161 and a second quadrangular prism waveguide 162 located at both ends of the rectangular parallelepiped waveguide 15 respectively.
  • the value range of the width and height of the rectangular waveguide 15 may be 1-20 microns.
  • a silicon dioxide core layer formed on the peripheral wall of the lithium niobate optical waveguide and surrounding the lithium niobate optical waveguide.
  • the end face of the silica core layer is rectangular or trapezoidal, and the end face area of the silica core layer ranges from tens of square microns to hundreds of square microns.
  • a silica cladding layer formed on the peripheral wall of the silica core layer and surrounding the silica core layer.
  • the optical coupling structure may further include: an adhesive.
  • the adhesive is provided on an end surface of the silica core layer and the silica cladding layer in the light transmission direction, and the refractive index of the adhesive is different from that of the silica core layer The difference in refractive index is less than 0.5.
  • the adhesive can be used to fix the end face of the single-mode optical fiber with the silica core layer and the silica cladding in the light transmission direction.
  • the ends of the silica core layer and the silica cladding layer in the light transmission direction are aligned with the single-mode optical fiber, they can be fixed with an adhesive.
  • the quartz substrate layer can be etched first Groove, then place the single-mode fiber in In the groove, the cover plate and adhesive can be used to fix it.
  • the optical coupling structure in the embodiment of the present invention has a large optical bandwidth.
  • FIG. 10, FIG. 11 and FIG. 12 are schematic diagrams of optical coupling structures with different silica waveguide end structures in the case where the silica core layer is completely covered with a lithium niobate optical waveguide.
  • 10 is a schematic diagram of an optical coupling structure having a terminal structure with a constant width
  • FIG. 11 is a schematic diagram of an optical coupling structure having a terminal structure whose width gradually narrows in a direction away from a single-mode fiber to a single-mode fiber
  • FIG. 12 is A schematic diagram of an optical coupling structure having an end structure whose width gradually widens in a direction away from the single-mode optical fiber to close to the single-mode optical fiber.
  • the optical coupling structure in actual use should include but not limited to these three situations.
  • one end face of the silica core layer and the silica cladding in the light transmission direction is connected to the single-mode optical fiber 213 through the adhesive 223, and the other end face is passed through the adhesive 224 and Single-mode fiber 214 is connected.
  • one end face of the silica core layer and the silica cladding in the light transmission direction is connected to the single-mode optical fiber 215 through the adhesive 225, and the other end face is passed through the adhesive 226 and the single-mode The optical fiber 216 is connected.
  • FIG. 10 one end face of the silica core layer and the silica cladding in the light transmission direction is connected to the single-mode optical fiber 213 through the adhesive 223, and the other end face is passed through the adhesive 224 and Single-mode fiber 214 is connected.
  • one end face of the silica core layer and the silica cladding in the light transmission direction is connected to the single-mode optical fiber 215 through the adhesive 225, and the other end face is passed through the adhesive 226 and the single-mode The
  • one end surface of the silica core layer and the silica cladding in the light transmission direction is connected to the single-mode optical fiber 217 through the adhesive 227, and the other end surface is connected to the single-mode optical fiber through the adhesive 228 Fiber 218 is connected.
  • the optical coupling structure further includes an adhesive
  • the adhesive is provided on the end surfaces of the silica core layer and the silica cladding in the light transmission direction, and the refractive index of the adhesive is different from that of the silica core layer
  • the difference in refractive index is less than 0.5. Therefore, in the process of coupling light from the optical coupling structure to the single-mode optical fiber, the Fresnel reflection loss caused by the sudden change in refractive index can be reduced, which can alleviate the niobic acid existing in the prior art.
  • the technical problem of low coupling efficiency between the lithium optical waveguide and the single-mode optical fiber is conducive to further improving the coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber.
  • the optical coupling system may include: a first single-mode optical fiber, a second single-mode optical fiber, and the foregoing embodiments Light coupling structure.
  • the first end of the optical coupling structure is connected to the first single-mode optical fiber
  • the second end of the optical coupling structure is connected to the second single-mode optical fiber
  • both the first end and the second end are Located in the direction of light transmission.
  • the first end 231 of the optical coupling structure may be connected to the first single-mode optical fiber 211 by an adhesive 221, and the second end 232 of the optical coupling structure may be connected by an adhesive 222 and The second single-mode optical fiber 212 is connected.
  • the refractive index difference between the silica core layer and the silica cladding is ⁇ n
  • the refractive index difference between the core region of the single-mode fiber and the cladding of the single-mode fiber is ⁇ n ', ⁇ n- ⁇ n' ⁇ 0.5.
  • the lithium niobate optical waveguide may include a rectangular parallelepiped waveguide 15 in the middle and a first quadrangular prism waveguide 161 and a second quadrangular prism waveguide 162 located at both ends of the rectangular parallelepiped waveguide 15 respectively.
  • the first quadrangular prism waveguide 161 is close to the first end 231, and the end surface of the first quadrangular prism waveguide 161 away from the first single-mode optical fiber 211 is connected to the end surface of the rectangular parallelepiped 15
  • the distance between the end surface of the first quadrangular prism waveguide 161 near the first single-mode optical fiber 211 and the first end 231 is greater than 0, and the cross-sectional dimension of the first quadrangular prism waveguide 161 is away from the first
  • the direction from the single-mode optical fiber 211 to the first single-mode optical fiber 211 gradually decreases.
  • the second quadrangular prism waveguide 162 is close to the second end 232, the end surface of the second quadrangular prism waveguide 162 away from the second single-mode optical fiber 212 is connected to the end surface of the rectangular parallelepiped waveguide 15, the second The distance between the end surface of the quadrangular prism waveguide 162 near the second single-mode optical fiber 212 and the second end 232 is greater than 0, and the cross-sectional dimension of the second quadrangular prism waveguide 162 is away from the second single-mode optical fiber The direction from 212 to close to the second single-mode optical fiber 212 gradually becomes smaller.
  • the vertical distance between the end surface of the first quadrangular prism waveguide 161 near the first single-mode optical fiber 211 and the end surface far from the first single-mode optical fiber 211 is greater than 0.5 ⁇ m.
  • the vertical distance between the end surface of the second quadrangular prism waveguide 162 near the second single-mode optical fiber 212 and the end surface far from the second single-mode optical fiber 212 is greater than 0.5 ⁇ m.
  • the preferred value range of the width and height of the rectangular waveguide 15 may be 1 to 1.5 microns.
  • the vertical distance between the end surface of the first quadrangular prism waveguide 161 near the first single-mode optical fiber 211 and the end surface far from the first single-mode optical fiber 211 may be 200 ⁇ m.
  • the vertical distance between the end surface of the second quadrangular prism waveguide 162 near the second single-mode fiber 212 and the end surface far from the second single-mode fiber 212 may be 200 ⁇ m, so that the optical field can be slowly removed from the lithium niobate optical waveguide Transition to the silica waveguide that will be formed later.
  • the end face of the silica core layer is rectangular or trapezoidal, and the end face area of the silica core layer ranges from tens of square microns to hundreds of square microns.
  • the silica core layer and the two The difference between the refractive index difference between the silicon oxide cladding and the refractive index difference between the core region and the cladding of the single-mode fiber is less than 0.5, so that the optical coupling structure is matched with the mode field of the single-mode fiber to reduce the band of mode mutation Mode mismatch loss, it can alleviate the existing technical problems of low coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber, which is beneficial to further improve the Coupling efficiency.
  • the cross-sectional dimension of the first quadrangular prism waveguide gradually decreases along the direction away from the first single-mode fiber to the first single-mode optical fiber; the cross-sectional dimension of the second quadrangular prism waveguide moves away from the second single-mode fiber to near the second single-mode fiber
  • the direction gradually decreases, so that the light field can slowly transition from the lithium niobate optical waveguide to the silicon dioxide waveguide, reducing the optical loss during the transition process, therefore, the existing lithium niobate optical waveguide in the prior art can be alleviated
  • the technical problem of low coupling efficiency with the single-mode optical fiber is conducive to further improving the coupling efficiency between the lithium niobate optical waveguide and the single-mode optical fiber.
  • the method of the present invention also includes other steps. Since it is not related to the innovation of the present invention, it will not be repeated here.

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Abstract

提供了光耦合结构、光耦合系统及光耦合结构的制备方法，方法包括：步骤S101：准备基底；步骤S102：在基底上形成铌酸锂光波导；步骤S103：在铌酸锂光波导的周壁上形成包裹铌酸锂光波导的二氧化硅芯层；步骤S104：在二氧化硅芯层的周壁上形成包裹二氧化硅芯层的二氧化硅包层。该光耦合结构缓解了现有技术中的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到了提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。

Description

光耦合结构、系统及光耦合结构的制备方法 技术领域
本发明涉及光纤通信与集成光学技术领域，尤其是涉及一种光耦合结构、系统及光耦合结构的制备方法。
背景技术
传统的铌酸锂器件采用高温质子交换等工艺制备，具有器件体积大、工艺一致性差等缺陷。铌酸锂刻蚀工艺的出现，使得利用光刻与刻蚀等工艺在铌酸锂晶片上集成多个光学功能器件成为可能。
在实际应用中，铌酸锂光波导的截面积在平方微米量级，而单模光纤的截面积在百平方微米量级，由于铌酸锂光波导的截面积与单模光纤的截面积不在一个量级上，会使得铌酸锂光波导与单模光纤间的模场不匹配。进而导致铌酸锂光波导与单模光纤间的耦合效率低的问题。
发明内容
(一)要解决的技术问题
鉴于上述问题，本发明提供了一种光耦合结构、系统及光耦合结构的制备方法，以至少部分解决以上所存在的技术问题。
(二)技术方案
根据本发明的一个方面，提供了一种光耦合结构，包括：
基底；
形成于所述基底上的铌酸锂光波导；
形成于所述铌酸锂光波导的周壁上、且包裹所述铌酸锂光波导的二氧化硅芯层；
形成于所述二氧化硅芯层的周壁上、且包裹所述二氧化硅芯层的二氧化硅包层。
在一些实施例中，所述二氧化硅芯层的端面为矩形或梯形，所述二氧 化硅芯层的端面面积的取值范围为数十平方微米至数百平方微米。
在一些实施例中，所述的光耦合结构还包括：粘接剂；
所述粘接剂设置在所述二氧化硅芯层和所述二氧化硅包层的在光的传输方向上的端面上，所述粘接剂的折射率与所述二氧化硅芯层的折射率的差值小于0.5。
根据本发明的另一个方面，还提供了一种光耦合系统，包括：第一单模光纤、第二单模光纤和所述的光耦合结构；
所述光耦合结构的第一端和所述第一单模光纤连接，所述光耦合结构的第二端和所述第二单模光纤连接，所述第一端和所述第二端均位于光的传输方向上。
在一些实施例中，所述二氧化硅芯层和所述二氧化硅包层间的折射率差为Δn，所述单模光纤的芯区和所述单模光纤的包层间的折射率差为Δn’，Δn-Δn’＜0.5。
在一些实施例中，所述铌酸锂光波导包括位于中间的长方体波导与分别位于所述长方体波导两端的第一四棱柱波导和第二四棱柱波导；
所述第一四棱柱波导靠近所述第一端，所述第一四棱柱波导的远离所述第一单模光纤的端面和所述长方体波导的端面连接，所述第一四棱柱波导的靠近所述第一单模光纤的端面与所述第一端之间的距离大于0，所述第一四棱柱波导的截面尺寸沿远离所述第一单模光纤至靠近所述第一单模光纤的方向逐渐变小；
所述第二四棱柱波导靠近所述第二端，所述第二四棱柱波导的远离所述第二单模光纤的端面和所述长方体波导的端面连接，所述第二四棱柱波导的靠近所述第二单模光纤的端面与所述第二端之间的距离大于0，所述第二四棱柱波导的截面尺寸沿远离所述第二单模光纤至靠近所述第二单模光纤的方向逐渐变小。
根据本发明的又一个方面，提供了一种光耦合结构的制备方法，包括：
步骤S101：准备基底；
步骤S102：在所述基底上形成铌酸锂光波导；
步骤S103：在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层；
步骤S104：在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层。
在一些实施例中，所述基底自下向上依次包括：石英衬底层、埋层二氧化硅和铌酸锂薄膜层，所述在所述基底上形成铌酸锂光波导，包括：
利用光刻刻蚀所述铌酸锂薄膜层，形成所述铌酸锂光波导。
在一些实施例中，在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层，包括：
在步骤S102制出的结构上形成盖层二氧化硅；
对所述盖层二氧化硅进行平整化处理；
利用光刻刻蚀去除部分所述盖层二氧化硅与部分所述埋层二氧化硅，刻蚀至所述石英衬底层的上方，经过刻蚀后的盖层二氧化硅和经过刻蚀后的埋层二氧化硅形成所述二氧化硅芯层；所述二氧化硅芯层在光的传输方向上的长度大于所述铌酸锂光波导在光的传输方向上的长度。
在一些实施例中，在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层，包括：
在步骤S103制出的结构上形成顶层二氧化硅，所述顶层二氧化硅和所述石英衬底层形成所述二氧化硅包层；所述二氧化硅芯层在光的传输方向上的长度等于所述二氧化硅包层在光的传输方向上的长度。
(三)有益效果
从上述技术方案可以看出，本发明提供的光耦合结构、系统及光耦合结构的制备方法具有以下有益效果：
(1)光耦合结构包括形成于铌酸锂光波导的周壁上、且包裹铌酸锂光波导的二氧化硅芯层；及形成于二氧化硅芯层的周壁上、且包裹二氧化硅芯层的二氧化硅包层，由于二氧化硅芯层的端面面积大于铌酸锂光波导的截面积，所以，二氧化硅芯层的端面面积与单模光纤的截面积更加接近，可以减少由于模场不匹配而导致的光损耗问题，因此，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。
(2)二氧化硅芯层的端面为矩形或梯形，二氧化硅芯层的端面面积的取值范围为数十平方微米至数百平方微米，二氧化硅芯层和二氧化硅包 层间的折射率差为Δn，单模光纤的芯区和单模光纤的包层间的折射率差为Δn’，Δn-Δn’＜0.5，所以，使得光耦合结构与单模光纤的模场匹配，减少由于模式突变带来的模式失配损耗，因此，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。
(3)光耦合结构还包括：粘接剂，粘接剂设置在二氧化硅芯层和二氧化硅包层的在光的传输方向上的端面上，粘接剂的折射率与二氧化硅芯层的折射率的差值小于0.5，所以，光从光耦合结构耦合到单模光纤的过程中，可以减少由于折射率突变带来的菲涅尔反射损耗，因此，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。
(4)第一四棱柱波导的截面尺寸沿远离第一单模光纤至靠近第一单模光纤的方向逐渐变小；第二四棱柱波导的截面尺寸沿远离第二单模光纤至靠近第二单模光纤的方向逐渐变小，使得光场可以缓慢地从铌酸锂光波导中过渡到二氧化硅波导中，减少过渡过程中的光损耗，因此，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。
(5)本发明中，利用光刻刻蚀工艺得到光耦合结构，避免由于现有技术中利用高温质子交换工艺制备铌酸锂器件而导致的工艺难度高及器件一致性差的问题，因此，可以降低制备光耦合结构的工艺难度，提高光耦合结构的一致性。
(6)本发明中，在制备光耦合结构的过程中，未使用光栅，所以可以避免由于现有技术中使用光栅制备光耦合结构而导致的对光偏振态敏感的问题，因此，可以得到对光偏振态不敏感的光耦合结构，降低了工作人员使用光耦合结构的时间，提高工作人员的使用效率。
附图说明
为了更清楚地说明本发明具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本发明的一些实施方式，对于本领域普 通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本发明实施例提供的光耦合结构的制备方法的流程图；
图2为本发明实施例提供的铌酸锂光波导制成前的基底的正视图；
图3为本发明实施例提供的铌酸锂光波导制成后的基底的正视图；
图4为本发明实施例提供的铌酸锂光波导制成后的基底的俯视图；
图5为本发明实施例提供的二氧化硅芯层制成前的二氧化硅波导的正视图；
图6为本发明实施例提供的二氧化硅芯层制成后的二氧化硅波导的正视图；
图7为本发明实施例提供的二氧化硅芯层制成后的二氧化硅波导的俯视图；
图8为本发明实施例提供的光耦合结构的正视图；
图9为本发明实施例提供的光耦合系统的第一种俯视图；
图10为本发明实施例提供的光耦合系统的第二种俯视图；
图11为本发明实施例提供的光耦合系统的第三种俯视图；
图12为本发明实施例提供的光耦合系统的第四种俯视图。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚明白，以下结合具体实施例，并参照附图，对本发明进一步详细说明。
本发明实施例提供的一种光耦合结构、系统及光耦合结构的制备方法，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。
为便于对本实施例进行理解，首先对本发明实施例所公开的一种光耦合结构的制备方法进行详细介绍，如图1所示，光耦合结构的制备方法可以包括以下步骤。
步骤S101：准备基底。
其中，如图2所示，所述基底自下向上可以依次包括：石英衬底层11、埋层二氧化硅12和铌酸锂薄膜层13。石英衬底层11的材料组分可以为纯 二氧化硅，或者可以为掺杂二氧化硅。石英衬底层11可以起到支撑整个光耦合结构的作用。埋层二氧化硅12可以为调整淀积(沉积)工艺的淀积二氧化硅，埋层二氧化硅12的材料组分可以为纯二氧化硅，或者可以为掺杂二氧化硅。铌酸锂薄膜层13可以通过特殊工艺键和到埋层二氧化硅12上。铌酸锂薄膜层13的材料组分可以为纯净的铌酸锂，或者可以为掺杂铌酸锂材料。
进一步的，石英衬底层11对于1550纳米波长的光的折射率范围约为1.4～1.6。埋层二氧化硅12对于1550纳米波长的光的折射率范围约为1.4～1.6。
需要注意的是，埋层二氧化硅12的折射率高于石英衬底层11的折射率。
步骤S102：在所述基底上形成铌酸锂光波导。
其中，步骤S102可以包括：如图3所示，利用光刻刻蚀所述铌酸锂薄膜层13，形成所述铌酸锂光波导14。如图4所示，所述铌酸锂光波导14可以包括位于中间的长方体波导15与分别位于所述长方体波导15两端的第一四棱柱波导161和第二四棱柱波导162。
步骤S103：在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层。
优选的，所述二氧化硅芯层的端面为矩形或梯形，所述二氧化硅芯层的端面面积的取值范围为数十平方微米至数百平方微米。
其中，所述在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层，可以包括以下步骤：
如图5所示，在步骤S102制出的结构上形成盖层二氧化硅17。
示例性的，盖层二氧化硅17可以为通过淀积(沉积)工艺形成的纯二氧化硅，或者掺杂二氧化硅。盖层二氧化硅17覆盖在铌酸锂光波导14上面。盖层二氧化硅17的折射率与石英衬底层11的折射率的差值可以设置在10％以内。具体的，盖层二氧化硅17对于1550纳米波长的光的折射率范围约为1.4～1.6。
具体的，可以采用等离子增强化学气相沉积PECVD工艺方法形成盖层二氧化硅17，利用硅烷与一氧化氮在350摄氏度反应生成二氧化硅，反 应方程式如下：SiH 4(气态)+2N 2O(气态)——SiO 2(固态)+2N 2(气态)+2H 2(气态)。
对所述盖层二氧化硅17进行平整化处理。
示例性的，可以利用化学机械抛光对所述盖层二氧化硅进行平整化处理。
如图6所示，在经过平整化处理后的盖层二氧化硅上，利用光刻刻蚀去除部分所述盖层二氧化硅与部分所述埋层二氧化硅，刻蚀至所述石英衬底层11的上方，经过刻蚀后的盖层二氧化硅19和经过刻蚀后的埋层二氧化硅18形成所述二氧化硅芯层。如图7所示，二氧化硅芯层将铌酸锂光波导14完全包裹。
具体的，在盖层二氧化硅上涂覆光刻胶后，利用掩膜版进行曝光和显影，将掩膜版图形转移到光刻胶上。然后通过刻蚀将光刻胶图形转移到盖层二氧化硅上。选择CF 4与H 2的混合气体作为二氧化硅的刻蚀气体，其中H 2在混合气体内的含量为混合气体体积的50％，该组分的CF 4/H 2混合气体对二氧化硅和硅的选择比超过40∶1，刻蚀选择性较好。在等离子体环境中，CF 4可以产生氟原子，氟原子与二氧化硅发生反应，从而刻蚀二氧化硅，反应方程式如下：
CF 4+e-——CF 3+F+e-
4F(自由基)+SiO 2(固态)——SiF 4(气态)+O 2(气态)
其中，H 2的作用是降低CF 4与硅的反应速率，提高CF 4对二氧化硅和硅的选择刻蚀比。该刻蚀过程一直刻蚀到石英衬底层上方。
需要注意的是，埋层二氧化硅的折射率可以等于盖层二氧化硅的折射率，埋层二氧化硅的折射率也可以与盖层二氧化硅的折射率相近。盖层二氧化硅的折射率高于石英衬底层的折射率。要得到满足条件的盖层二氧化硅的折射率，可以通过在化学方法：SiH 4(气态)+2N 2O(气态)——SiO 2(固态)+2N 2(气态)+2H 2(气态)中调整SiH 4与2N 2O两种气体比例实现，也可以通过掺杂实现。若埋层二氧化硅的折射率等于盖层二氧化硅的折射率，那么可以将埋层二氧化硅的折射率确定为二氧化硅芯层的折射率。若埋层二氧化硅的折射率与盖层二氧化硅的折射率相近，那么可以将埋层二氧化硅的折射率与盖层二氧化硅的折射率的均值确定为二氧化硅芯层的 折射率。
其中，所述二氧化硅芯层在光的传输方向上的长度大于所述铌酸锂光波导在光的传输方向上的长度。也就是说，二氧化硅芯层不仅完全将铌酸锂光波导包裹住，而且二氧化硅芯层的末端部分没有包裹铌酸锂光波导，二氧化硅芯层的末端部分完全为二氧化硅波导。
步骤S104：在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层。
其中，如图8所示，所述在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层，包括：在步骤S103制出的结构上形成顶层二氧化硅20，所述顶层二氧化硅20和所述石英衬底层11形成所述二氧化硅包层，所述二氧化硅芯层在光的传输方向上的长度等于所述二氧化硅包层在光的传输方向上的长度。
示例性的，顶层二氧化硅20可以为通过淀积(沉积)工艺形成的纯二氧化硅，或者掺杂二氧化硅。具体的，顶层二氧化硅20可以为调整淀积工艺的淀积二氧化硅。具体的，顶层二氧化硅20对于1550纳米波长的光的折射率范围约为1.4～1.6。
需要注意的是，顶层二氧化硅的折射率可以等于石英衬底层的折射率，顶层二氧化硅的折射率也可以与石英衬底层的折射率相近。顶层二氧化硅的折射率低于埋层二氧化硅的折射率。顶层二氧化硅的折射率低于盖层二氧化硅的折射率。顶层二氧化硅的折射率与石英衬底层的折射率均低于二氧化硅芯层的折射率。若顶层二氧化硅的折射率等于石英衬底层的折射率，那么可以将顶层二氧化硅的折射率确定为二氧化硅包层的折射率。若顶层二氧化硅的折射率与石英衬底层的折射率相近，那么可以将顶层二氧化硅的折射率与石英衬底层的折射率的均值确定为二氧化硅包层的折射率。
本实施例具有以下有益效果：
(1)在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层，在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层，由于二氧化硅芯层的端面面积大于铌酸锂光波导的截面积，所以，二氧化硅芯层的端面面积与单模光纤的截面积更加接近，可以减少由于模场不匹配而导致的光损耗问题，因此，可以缓解现有技术中存在的 铌酸锂光波导与单模光纤间的耦合效率低的技术问题，达到提高铌酸锂光波导与单模光纤间的耦合效率的技术效果。
(2)利用光刻刻蚀工艺得到光耦合结构，避免由于现有技术中利用高温质子交换工艺制备铌酸锂器件而导致的工艺难度高及器件一致性差的问题，因此，可以降低制备光耦合结构的工艺难度，提高光耦合结构的一致性。
(3)在制备光耦合结构的过程中，未使用光栅，所以可以避免由于现有技术中使用光栅制备光耦合结构而导致的对光偏振态敏感的问题，因此，可以得到对光偏振态不敏感的光耦合结构，降低了工作人员使用光耦合结构的时间，提高工作人员的使用效率。
在本发明的又一实施例中，对本发明实施例所公开的一种光耦合结构进行详细介绍，光耦合结构包括：
基底。
其中，如图2所示，所述基底自下向上可以依次包括：石英衬底层11、埋层二氧化硅12和铌酸锂薄膜层13。
形成于所述基底上的铌酸锂光波导。
其中，如图3和图4所示，所述铌酸锂光波导14可以包括位于中间的长方体波导15与分别位于所述长方体波导15两端的第一四棱柱波导161和第二四棱柱波导162。示例性的，长方体波导15的宽度及高度的取值范围可以为1～20微米。
形成于所述铌酸锂光波导的周壁上、且包裹所述铌酸锂光波导的二氧化硅芯层。
优选的，所述二氧化硅芯层的端面为矩形或梯形，所述二氧化硅芯层的端面面积的取值范围为数十平方微米至数百平方微米。
形成于所述二氧化硅芯层的周壁上、且包裹所述二氧化硅芯层的二氧化硅包层。
本发明实施例中，光耦合结构还可以包括：粘接剂。
所述粘接剂设置在所述二氧化硅芯层和所述二氧化硅包层的在光的传输方向上的端面上，所述粘接剂的折射率与所述二氧化硅芯层的折射率的差值小于0.5。
其中，粘接剂可以用于固定单模光纤与二氧化硅芯层和二氧化硅包层的在光的传输方向上的端面。
进一步的，二氧化硅芯层和二氧化硅包层的在光的传输方向上的端面与单模光纤对准后，可以利用粘接剂进行固定。在对准的过程中，可以先在石英衬底层上刻蚀
Figure PCTCN2018120911-appb-000001
型槽，然后将单模光纤放置在
Figure PCTCN2018120911-appb-000002
型槽中，最后可以利用盖板与粘接剂进行固定。本发明实施例中的光耦合结构具有大的光学带宽。
举例说明，图10、图11与图12是在二氧化硅芯层完全包覆铌酸锂光波导的情况下，具有不同的二氧化硅波导末端结构的光耦合结构的示意图。图10为具有宽度不变的末端结构的光耦合结构的示意图，图11为具有宽度沿远离单模光纤至靠近单模光纤的方向逐渐变窄的末端结构的光耦合结构的示意图，图12为具有宽度沿远离单模光纤至靠近单模光纤的方向逐渐变宽的末端结构的光耦合结构的示意图。实际使用中的光耦合结构应包含但不限于这三种情形。
其中，如图10所示，二氧化硅芯层和二氧化硅包层的在光的传输方向上的一个端面通过粘接剂223和单模光纤213连接，另一个端面通过粘接剂224和单模光纤214连接。如图11所示，二氧化硅芯层和二氧化硅包层的在光的传输方向上的一个端面通过粘接剂225和单模光纤215连接，另一个端面通过粘接剂226和单模光纤216连接。如图12所示，二氧化硅芯层和二氧化硅包层的在光的传输方向上的一个端面通过粘接剂227和单模光纤217连接，另一个端面通过粘接剂228和单模光纤218连接。
本实施例具有以下有益效果：
由于光耦合结构还包括粘接剂，粘接剂设置在二氧化硅芯层和二氧化硅包层的在光的传输方向上的端面上，粘接剂的折射率与二氧化硅芯层的折射率的差值小于0.5，所以，光从光耦合结构耦合到单模光纤的过程中，可以减少由于折射率突变带来的菲涅尔反射损耗，进而可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，有利于进一步提高铌酸锂光波导与单模光纤间的耦合效率。
在本发明的又一实施例中，对本发明实施例所公开的一种光耦合系统进行详细介绍，光耦合系统可以包括：第一单模光纤、第二单模光纤和如 上述实施例所述的光耦合结构。
所述光耦合结构的第一端和所述第一单模光纤连接，所述光耦合结构的第二端和所述第二单模光纤连接，所述第一端和所述第二端均位于光的传输方向上。
如图9所示，所述光耦合结构的第一端231可以通过粘接剂221和所述第一单模光纤211连接，所述光耦合结构的第二端232可以通过粘接剂222和所述第二单模光纤212连接。
优选的，所述二氧化硅芯层和所述二氧化硅包层间的折射率差为Δn，所述单模光纤的芯区和所述单模光纤的包层间的折射率差为Δn’，Δn-Δn’＜0.5。
其中，如图9所示，所述铌酸锂光波导可以包括位于中间的长方体波导15与分别位于所述长方体波导15两端的第一四棱柱波导161和第二四棱柱波导162。
优选的，所述第一四棱柱波导161靠近所述第一端231，所述第一四棱柱波导161的远离所述第一单模光纤211的端面和所述长方体波导15的端面连接，所述第一四棱柱波导161的靠近所述第一单模光纤211的端面与所述第一端231之间的距离大于0，所述第一四棱柱波导161的截面尺寸沿远离所述第一单模光纤211至靠近所述第一单模光纤211的方向逐渐变小。所述第二四棱柱波导162靠近所述第二端232，所述第二四棱柱波导162的远离所述第二单模光纤212的端面和所述长方体波导15的端面连接，所述第二四棱柱波导162的靠近所述第二单模光纤212的端面与所述第二端232之间的距离大于0，所述第二四棱柱波导162的截面尺寸沿远离所述第二单模光纤212至靠近所述第二单模光纤212的方向逐渐变小。
其中，第一四棱柱波导161的靠近第一单模光纤211的端面与远离第一单模光纤211的端面之间的垂直距离大于0.5微米。第二四棱柱波导162的靠近第二单模光纤212的端面与远离第二单模光纤212的端面之间的垂直距离大于0.5微米。
优选的，为保证单模式传输，长方体波导15的宽度及高度的优选取值范围可以为1～1.5微米。第一四棱柱波导161的靠近第一单模光纤211 的端面与远离第一单模光纤211的端面之间的垂直距离可以为200微米。第二四棱柱波导162的靠近第二单模光纤212的端面与远离第二单模光纤212的端面之间的垂直距离可以为200微米，以使得光场可以缓慢地从铌酸锂光波导中过渡到后面将要形成的二氧化硅波导中。
所述二氧化硅芯层的端面为矩形或梯形，所述二氧化硅芯层的端面面积的取值范围为数十平方微米至数百平方微米，所述二氧化硅芯层和所述二氧化硅包层间的折射率差与单模光纤的芯区和包层间的折射率差的差值小于0.5，所以，使得光耦合结构与单模光纤的模场匹配，减少由于模式突变带来的模式失配损耗，因此，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，有利于进一步提高铌酸锂光波导与单模光纤间的耦合效率。
第一四棱柱波导的截面尺寸沿远离第一单模光纤至靠近第一单模光纤的方向逐渐变小；第二四棱柱波导的截面尺寸沿远离第二单模光纤至靠近第二单模光纤的方向逐渐变小，使得光场可以缓慢地从铌酸锂光波导中过渡到二氧化硅波导中，减少过渡过程中的光损耗，因此，可以缓解现有技术中存在的铌酸锂光波导与单模光纤间的耦合效率低的技术问题，有利于进一步提高铌酸锂光波导与单模光纤间的耦合效率。
以上所述的具体实施例，对本发明的目的、技术方案和有益效果进行了进一步详细说明，所应理解的是，以上所述仅为本发明的具体实施例而已，并不用于限制本发明，凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。
至此，已经结合附图对本发明实施例进行了详细描述。依据以上描述，本领域技术人员应当对本发明有了清楚的认识。
需要说明的是，在附图或说明书正文中，未绘示或描述的实现方式，均为所属技术领域中普通技术人员所知的形式，并未进行详细说明。此外，上述对各元件和方法的定义并不仅限于实施例中提到的各种具体结构、形状或方式，本领域普通技术人员可对其进行简单地更改或替换。
当然，根据实际需要，本发明方法还包含其他的步骤，由于同本发明的创新之处无关，此处不再赘述。
此外，上述对各元件和方法的定义并不仅限于实施例中提到的各种具体结构、形状或方式，本领域普通技术人员可对其进行简单地更改或替换。
需要说明的是，实施例中提到的方向用语，例如“上”、“下”、“前”、“后”、“左”、“右”等，仅是参考附图的方向，并非用来限制本发明的保护范围。贯穿附图，相同的元素由相同或相近的附图标记来表示。在可能导致对本发明的理解造成混淆时，将省略常规结构或构造。并且图中各部件的形状和尺寸不反映真实大小和比例，而仅示意本发明实施例的内容。另外，在权利要求中，不应将位于括号之间的任何参考符号构造成对权利要求的限制。
除非有所知名为相反之意，本说明书及所附权利要求中的数值参数是近似值，能够根据通过本发明的内容所得的所需特性改变。具体而言，所有使用于说明书及权利要求中表示组成的含量、反应条件等等的数字，应理解为在所有情况中是受到「约」的用语所修饰。一般情况下，其表达的含义是指包含由特定数量在一些实施例中±10％的变化、在一些实施例中±5％的变化、在一些实施例中±1％的变化、在一些实施例中±0.5％的变化。
再者，单词“包含”或“包括”不排除存在未列在权利要求中的元件或步骤。位于元件之前的单词“一”或“一个”不排除存在多个这样的元件。
说明书与权利要求中所使用的序数例如“第一”、“第二”、“第三”等的用词，以修饰相应的元件，其本身并不意味着该元件有任何的序数，也不代表某一元件与另一元件的顺序、或是制造方法上的顺序，该些序数的使用仅用来使具有某命名的一元件得以和另一具有相同命名的元件能做出清楚区分。
类似地，应当理解，为了精简本发明并帮助理解各个公开方面中的一个或多个，在上面对本发明的示例性实施例的描述中，本发明的各个特征有时被一起分组到单个实施例、图、或者对其的描述中。然而，并不应将该公开的方法解释成反映如下意图：即所要求保护的本发明要求比在每个权利要求中所明确记载的特征更多的特征。更确切地说，如下面的权利要求书所反映的那样，公开方面在于少于前面公开的单个实施例的所有特征。 因此，遵循具体实施方式的权利要求书由此明确地并入该具体实施方式，其中每个权利要求本身都作为本发明的单独实施例。
以上所述的具体实施例，对本发明的目的、技术方案和有益效果进行了进一步详细说明，所应理解的是，以上所述仅为本发明的具体实施例而已，并不用于限制本发明，凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种光耦合结构，其特征在于，包括：
    基底；
    形成于所述基底上的铌酸锂光波导；
    形成于所述铌酸锂光波导的周壁上、且包裹所述铌酸锂光波导的二氧化硅芯层；
    形成于所述二氧化硅芯层的周壁上、且包裹所述二氧化硅芯层的二氧化硅包层。
  2. 根据权利要求1所述的光耦合结构，其特征在于，所述二氧化硅芯层的端面为矩形或梯形，所述二氧化硅芯层的端面面积的取值范围为数十平方微米至数百平方微米。
  3. 根据权利要求2所述的光耦合结构，其特征在于，还包括：粘接剂；
    所述粘接剂设置在所述二氧化硅芯层和所述二氧化硅包层的在光的传输方向上的端面上，所述粘接剂的折射率与所述二氧化硅芯层的折射率的差值小于0.5。
  4. 一种光耦合系统，其特征在于，包括：第一单模光纤、第二单模光纤和如权利要求1至3中任一项所述的光耦合结构；
    所述光耦合结构的第一端和所述第一单模光纤连接，所述光耦合结构的第二端和所述第二单模光纤连接，所述第一端和所述第二端均位于光的传输方向上。
  5. 根据权利要求4所述的光耦合系统，其特征在于，所述二氧化硅芯层和所述二氧化硅包层间的折射率差为Δn，所述单模光纤的芯区和所述单模光纤的包层间的折射率差为Δn’，Δn-Δn’＜0.5。
  6. 根据权利要求5所述的光耦合系统，其特征在于，所述铌酸锂光波导包括位于中间的长方体波导与分别位于所述长方体波导两端的第一四棱柱波导和第二四棱柱波导；
    所述第一四棱柱波导靠近所述第一端，所述第一四棱柱波导的远离所述第一单模光纤的端面和所述长方体波导的端面连接，所述第一四棱柱波导的靠近所述第一单模光纤的端面与所述第一端之间的距离大于0，所述 第一四棱柱波导的截面尺寸沿远离所述第一单模光纤至靠近所述第一单模光纤的方向逐渐变小；
    所述第二四棱柱波导靠近所述第二端，所述第二四棱柱波导的远离所述第二单模光纤的端面和所述长方体波导的端面连接，所述第二四棱柱波导的靠近所述第二单模光纤的端面与所述第二端之间的距离大于0，所述第二四棱柱波导的截面尺寸沿远离所述第二单模光纤至靠近所述第二单模光纤的方向逐渐变小。
  7. 一种光耦合结构的制备方法，其特征在于，包括：
    步骤S101：准备基底；
    步骤S102：在所述基底上形成铌酸锂光波导；
    步骤S103：在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层；
    步骤S104：在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层。
  8. 根据权利要求7所述的光耦合结构的制备方法，其特征在于，所述基底自下向上依次包括：石英衬底层、埋层二氧化硅和铌酸锂薄膜层，所述在所述基底上形成铌酸锂光波导，包括：
    利用光刻刻蚀所述铌酸锂薄膜层，形成所述铌酸锂光波导。
  9. 根据权利要求8所述的光耦合结构的制备方法，其特征在于，在所述铌酸锂光波导的周壁上形成包裹所述铌酸锂光波导的二氧化硅芯层，包括：
    在步骤S102制出的结构上形成盖层二氧化硅；
    对所述盖层二氧化硅进行平整化处理；
    利用光刻刻蚀去除部分所述盖层二氧化硅与部分所述埋层二氧化硅，刻蚀至所述石英衬底层的上方，经过刻蚀后的盖层二氧化硅和经过刻蚀后的埋层二氧化硅形成所述二氧化硅芯层；所述二氧化硅芯层在光的传输方向上的长度大于所述铌酸锂光波导在光的传输方向上的长度。
  10. 根据权利要求9所述的光耦合结构的制备方法，其特征在于，在所述二氧化硅芯层的周壁上形成包裹所述二氧化硅芯层的二氧化硅包层，包括：
    在步骤S103制出的结构上形成顶层二氧化硅，所述顶层二氧化硅和所述石英衬底层形成所述二氧化硅包层；所述二氧化硅芯层在光的传输方向上的长度等于所述二氧化硅包层在光的传输方向上的长度。
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