WO2004057395A1 - Dual grating assisted optical coupler - Google Patents
Dual grating assisted optical coupler Download PDFInfo
- Publication number
- WO2004057395A1 WO2004057395A1 PCT/GB2003/005634 GB0305634W WO2004057395A1 WO 2004057395 A1 WO2004057395 A1 WO 2004057395A1 GB 0305634 W GB0305634 W GB 0305634W WO 2004057395 A1 WO2004057395 A1 WO 2004057395A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- waveguide
- coupler
- waveguides
- coupler according
- grating
- Prior art date
Links
Classifications
-
- 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
- G02B6/125—Bends, branchings or intersections
-
- 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
- G02B6/12004—Combinations of two or more optical elements
-
- 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
- G02B6/124—Geodesic lenses or integrated gratings
-
- 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
-
- 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
- G02B2006/12133—Functions
- G02B2006/12147—Coupler
Definitions
- the present invention relates to the coupling of light between two waveguides with dissimilar refractive indices and/or with dissimilar geometries.
- Examples of such coupling of light include coupling between an optical fibre and a thin semiconductor waveguide, and coupling between semiconductor waveguides of differing dimensions (for example where one of the waveguides comprises a photonic bandgap structure).
- the optical coupler between two different waveguides is an essential part of an optical system where the lightwave from one optical component is coupled into another component.
- a low-loss coupler between an optical fibre and a waveguide is crucial for successful implementation of integrated optics in optical fibre communication systems.
- the difficulty increases when attempting to couple from a fibre to a waveguide with a large refractive index difference between the core and cladding of that waveguide.
- An example of such a waveguide is a silicon waveguide with silicon dioxide cladding, or indeed some other semiconductor waveguide.
- Grating-assisted directional couplers are fundamental guided- wave components in some distributed feedback lasers, distributed Bragg reflector lasers, optical wavelength filters and wavelength division multiplexing devices.
- a typical known GADC is shown in the accompanying Figure 1, and consists of two waveguides, a and b, a grating region, and a separation layer (with height /.i and refractive index n ).
- the purpose of this coupler is to enable power transfer from one waveguide to the other, over a minimum grating length and with maximum efficiency.
- the grating enables matching between propagation constants of two interacting waveguide modes that exchange optical power.
- introduction of the grating will not improve the coupling efficiency significantly.
- the power must be coupled first to the thick upper waveguide with refractive index very close to the refractive index of the fibre (waveguide b in Figure 1) in order to achieve very small insertion loss. From this waveguide power is coupled to the thin semiconductor waveguide (waveguide a in Figure 1). The large difference between these two waveguides in both thickness and refractive index makes the task very difficult to solve.
- a first aspect of the present invention provides an optical coupler comprising an input waveguide, an intermediate waveguide, an output waveguide, a first grating situated between the input and intermediate waveguides, and a second grating situated between the intermediate and output waveguides such that, in use, light propagating in the input waveguide is coupled into the intermediate waveguide with the assistance of the first grating, and thence is coupled into the output waveguide with the assistance of the second grating.
- the direction of propagation of light through the optical coupler preferably is reversible, so that light propagating in the output waveguide may be coupled into the intermediate waveguide with the assistance of the second grating, and thence coupled into the input waveguide with the assistance of the first grating.
- the invention is described herein in terms of the coupling of light from the input waveguide to the output waveguide.
- the coupler according to the invention therefore includes at least two gratings, and preferably includes only two gratings (the first and second gratings).
- the coupler according to the invention preferably is a directional coupler.
- DGADC Double Grating-Assisted Directional Coupler
- the invention has the advantage that the use of two gratings and the intermediate waveguide enables high coupling efficiency between the input and the output waveguides, which preferably have differing geometries and/or refractive indices.
- the coupler according to the invention preferably is fabricated as a layered structure, for example of semiconductor and/or dielectric materials. Most preferably, the waveguides and gratings of the coupler comprise such layers. The layers preferably are fabricated by means of deposition or epitaxial growth and selective etching, a process which is well known in the art.
- the coupler according to the invention may be used, for example, to couple light between two waveguides having differing geometries and/or refractive indices.
- a first waveguide for example an optical fibre
- the input waveguide of the coupler preferably is dimensioned such that at least one transverse (i.e. cross-sectional) dimension thereof (preferably the thickness of the input waveguide layer for embodiments in which the waveguides comprise layers) is of the same order of magnitude as that of such a first waveguide (e.g. an optical fibre).
- the refractive index of the input waveguide preferably is such that it is relatively close to that of the first waveguide (e.g. a silica optical fibre having a refractive index of approximately 1.45).
- the output waveguide of the coupler may be coupled to a second waveguide, such that light is coupled between the first waveguide (e.g. an optical fibre) and the second waveguide, via the coupler according to the invention. It is generally preferred, however, for the output waveguide of the coupler itself to be the "second waveguide". That is, the coupler preferably is used to couple light between an external first waveguide (e.g. an optical fibre) and the output waveguide of the coupler.
- the output waveguide of the coupler according to the invention preferably is a semiconductor waveguide of an integrated optical device. It was also indicated earlier that the coupler according to the invention may be used, for example, to couple between two semiconductor waveguides of differing dimensions.
- the "first" and “second” waveguides may be the two semiconductor waveguides of differing dimensions.
- the first waveguide may be the input waveguide of the coupler, and/or the second waveguide may be the output waveguide of the coupler.
- the first or the second waveguide may, for example, comprise a photonic bandgap structure.
- the input and output waveguides of the coupler according to the invention preferably have differing refractive indices and/or at least one differing transverse dimension.
- Transverse herein being transverse to the direction of propagation of the light, and including “vertical” as well as “horizontal” dimensions, i.e. any dimension that is cross-sectional with respect to the propagation axis of the waveguide.
- the intermediate waveguide of the coupler preferably has a different refractive index and/or at least one different transverse dimension to that of the input waveguide and/or the output waveguide.
- the coupler according to the invention advantageously has lower insertion loss, higher efficiency and better tolerances of structure parameters than any previously published design. Therefore, unlike previous coupler designs, it can enable the successful fabrication of a practicable integrated device that has satisfactory performance.
- a second aspect of the invention provides an integrated optical device comprising an optical coupler according to the first aspect of the invention, in which the input waveguide and/or the output waveguide of the coupler comprises a semiconductor waveguide of the device.
- the semiconductor waveguide of the device may, for example, comprise a semiconductor laser or a photodiode (or other component) of the device.
- a third aspect of the invention provides the use of an optical coupler or device according to the invention, to couple light between an external first waveguide and the output waveguide of the coupler, via the input waveguide of the coupler.
- the external first waveguide may, for example, comprise an optical fibre.
- Figure 1 is a schematic illustration of a conventional grating-assisted directional optical coupler
- FIGS. 2 to 4 are schematic illustrations of three embodiments of the optical coupler according to the invention.
- Figures 5 and 6 are schematic illustrations of two embodiments of the optical coupler according to the invention for coupling light between an optical fibre and a silicon-on-insulator (SOI) semiconductor waveguide; and
- Figure 7 is a schematic illustration of an embodiment of the optical coupler according to the invention for coupling light between a semiconductor laser and a large dimension waveguide or optical fibre.
- the coupler comprises the following: an approximately 5 ⁇ m thick input waveguide layer 10 having a refractive index very close to the refractive index of optical fibre (resulting in very low insertion loss); a silica top layer 11; a first transitional layer 12 having a refractive index slightly less than that of the input waveguide layer 10; a first grating 31; an intermediate waveguide layer 30; a second grating 32; a second transitional layer 22; and an output semiconductor waveguide layer 20.
- Light from input waveguide layer 10 is coupled to the intermediate waveguide 30 using the first grating 31, and subsequently to the output semiconductor waveguide layer 20 using the second grating 32. Coupling lengths and/or periods and/or depths and/or duty cycles generally are different for the two gratings.
- the profile of the grating is usually rectangular, but other grating profiles may be used.
- the refractive index of intermediate waveguide layer 30 generally must be larger than that of input waveguide layer 10, but less than the refractive index of the output waveguide layer 20.
- the intermediate waveguide layer 30 is crucial for the operation of the coupler device, because it enables highly efficient coupling occurring at both gratings, consequently forming an efficient DGADC.
- Layer 41 below the other layers serves for isolation from a substrate 40, strongly reducing radiation losses.
- FIGS. 3 and 4 Two further embodiments of the invention are illustrated in figures 3 and 4. These embodiments are simpler in fabrication terms, but generally will function satisfactorily only if waveguide coupling is efficient in the grating regions but is less efficient elsewhere.
- the second grating 32 is used to couple light from the intermediate waveguide 30 to the output waveguide 20, via the second transitional layer 22.
- optical modes in output waveguide 20 and intermediate waveguide layer 30 should not be phase matched in the direction of propagation (the z- direction as indicated), or light will generally couple from output waveguide 20, back into the intermediate waveguide 30.
- FIGS 5 and 6 Two embodiments of the optical coupler according to the invention, based on Silicon on Insulator (SOI) technology, are illustrated schematically in figures 5 and 6.
- SOI Silicon on Insulator
- III/V alloy semiconductor-based technologies for example GaAs and its ternary compounds, or InP and its quaternary compounds
- lithium niobate or related compounds can also be used.
- the specific embodiments of the invention disclosed herein may be varied in many ways while retaining one or more of the features of the coupler.
- the approach can be applicable to any homogeneous and isotropic material-based technology (SOI, GaAs, InP etc).
- Layers 10, 11 and 12 may, for example, be formed from glass, for example phosphosilicate glass, especially such glass having several percent by weight of p-type dopant.
- the waveguides may be of the rib, planar, strip or embedded type, for example.
- the optical coupler according to the invention will normally have a good spectral selectivity, because of the presence of two cascaded gratings.
- This selectivity can be varied, for example by using chirped or apodized gratings with appropriate windows.
- some polarisation insensitivity can be introduced by chirping one or both gratings to broaden the spectral response of one or both gratings, and hence broaden the response in terms of the modal propagation constants.
- Additional versatility can be introduced by making the gratings tunable. For example, by injection of carriers in a top waveguide or changing the temperature of the grating region, the refractive index in the region of the optical mode changes, modulating the effective index of the mode interacting with the grating, thereby making the grating tunable.
- the invention can, for example, be used for the realisation of monolithic waveguide-detector systems, where a photodiode can be implemented in the semiconductor (see figures 3 and 4).
- Figure 7 shows a further embodiment of the invention in which the coupler can be used for integration of a semiconductor laser (layer 20 in Figure 7) and a glass (or other) waveguide (10).
- An optical sensor could also be fabricated using the principle of Figure 7.
- optical power from waveguide 20 can be coupled to waveguide 10. If waveguide 10 has a geometry and refractive index profile that results in a significant optical field (evanescent field) at the surface of the structure, or in layer 11, that field can be made to take part in sensing functions. Thus the sensing region is localised in the overall structure.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/540,618 US7221825B2 (en) | 2002-12-23 | 2003-12-23 | Optical coupler |
AU2003295155A AU2003295155A1 (en) | 2002-12-23 | 2003-12-23 | Dual grating assisted optical coupler |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0229732A GB2396705B (en) | 2002-12-23 | 2002-12-23 | Optical coupler |
GB0229732.3 | 2002-12-23 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2004057395A1 true WO2004057395A1 (en) | 2004-07-08 |
Family
ID=9950098
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2003/005634 WO2004057395A1 (en) | 2002-12-23 | 2003-12-23 | Dual grating assisted optical coupler |
Country Status (4)
Country | Link |
---|---|
US (1) | US7221825B2 (en) |
AU (1) | AU2003295155A1 (en) |
GB (1) | GB2396705B (en) |
WO (1) | WO2004057395A1 (en) |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100759805B1 (en) * | 2005-12-07 | 2007-09-20 | 한국전자통신연구원 | Optically boosted elctroabsorption duplexer |
JP2008198944A (en) * | 2007-02-15 | 2008-08-28 | Fujitsu Ltd | Semiconductor optical integrated element |
WO2009141332A1 (en) * | 2008-05-19 | 2009-11-26 | Interuniversitair Microelektronica Centrum Vzw (Imec) | Integrated photonics device |
FR3008493B1 (en) * | 2013-07-15 | 2015-09-04 | Commissariat Energie Atomique | OPTICAL COUPLER PROVIDED WITH AN INTERMEDIATE WAVEGUIDE |
US9613886B2 (en) * | 2013-08-29 | 2017-04-04 | Industrial Technology Research Institute | Optical coupling module |
WO2015135794A1 (en) | 2014-03-08 | 2015-09-17 | Oerlikon Textile Gmbh & Co. Kg | Method and device for melt-spinning, drawing, crimping and winding multiple threads |
EP3153899A1 (en) * | 2015-10-09 | 2017-04-12 | Caliopa NV | Optical coupling scheme |
FR3051561B1 (en) | 2016-05-20 | 2019-07-12 | Stmicroelectronics (Crolles 2) Sas | INTEGRATED PHOTONIC DEVICE WITH ENHANCED OPTICAL COUPLING |
CN106154442B (en) * | 2016-09-20 | 2019-01-08 | 青岛海信宽带多媒体技术有限公司 | Optical module and its manufacturing method |
CN106680932A (en) * | 2017-03-20 | 2017-05-17 | 天津工业大学 | CMOS post-process integrated high-efficiency bidirectional grating coupler |
US10908286B2 (en) * | 2017-09-29 | 2021-02-02 | Intel Corporation | Integrated optical transmitter and receiver |
US10921525B2 (en) * | 2018-11-30 | 2021-02-16 | Mitsubishi Electric Research Laboratories, Inc. | Grating coupler and integrated grating coupler system |
US11670908B2 (en) * | 2019-10-27 | 2023-06-06 | Poet Technologies, Inc. | Planar laser structure with vertical signal transition |
US11143821B1 (en) * | 2020-03-24 | 2021-10-12 | Mitsubishi Electric Research Laboratories, Inc. | Integrated grating coupler system |
CN111624708B (en) * | 2020-07-10 | 2024-03-19 | 北京爱杰光电科技有限公司 | CMOS process compatible longitudinal optical coupling system and method thereof |
US20230384540A1 (en) * | 2022-05-24 | 2023-11-30 | Taiwan Semiconductor Manufacturing Company | Vertical grating coupler |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6404958B1 (en) * | 2000-10-31 | 2002-06-11 | Digital Optics Corp. | Intergrated optical coupler |
US20020122629A1 (en) * | 1999-05-12 | 2002-09-05 | Victor Grubsky | Wavelength-selective optical fiber components using cladding-mode assisted coupling |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4776661A (en) * | 1985-11-25 | 1988-10-11 | Canon Kabushiki Kaisha | Integrated optical device |
US5140149A (en) * | 1989-03-10 | 1992-08-18 | Canon Kabushiki Kaisha | Optical apparatus using wavelength selective photocoupler |
DE69311638T2 (en) * | 1992-07-15 | 1998-01-22 | Nippon Telegraph & Telephone | Optical switch |
US5412743A (en) * | 1993-12-06 | 1995-05-02 | Eastman Kodak Company | Method and apparatus for amplitude modulation of a laser beam |
US5420947A (en) * | 1994-06-17 | 1995-05-30 | Eastman Kodak Company | Method for achromatically coupling a beam of light into a waveguide |
US6567573B1 (en) * | 1997-02-12 | 2003-05-20 | Digilens, Inc. | Switchable optical components |
US6510266B2 (en) * | 2000-11-30 | 2003-01-21 | Institut National D'optique | Tunable optoelectronic frequency filter |
-
2002
- 2002-12-23 GB GB0229732A patent/GB2396705B/en not_active Expired - Fee Related
-
2003
- 2003-12-23 WO PCT/GB2003/005634 patent/WO2004057395A1/en not_active Application Discontinuation
- 2003-12-23 US US10/540,618 patent/US7221825B2/en not_active Expired - Fee Related
- 2003-12-23 AU AU2003295155A patent/AU2003295155A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020122629A1 (en) * | 1999-05-12 | 2002-09-05 | Victor Grubsky | Wavelength-selective optical fiber components using cladding-mode assisted coupling |
US6404958B1 (en) * | 2000-10-31 | 2002-06-11 | Digital Optics Corp. | Intergrated optical coupler |
Non-Patent Citations (1)
Title |
---|
KASHYAP,R: "Fiber Bragg Gratings", 1999, ACADEMIC PRESS, USA, XP002277349 * |
Also Published As
Publication number | Publication date |
---|---|
US7221825B2 (en) | 2007-05-22 |
US20060120667A1 (en) | 2006-06-08 |
AU2003295155A1 (en) | 2004-07-14 |
GB2396705A (en) | 2004-06-30 |
GB0229732D0 (en) | 2003-01-29 |
GB2396705B (en) | 2006-05-03 |
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