High-efficiency fully etched fiber-chip grating couplers with subwavelength structures for datacom and telecom applications

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DOIResolve DOI: http://doi.org/10.1117/12.2177861
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TypeArticle
Proceedings titleProceedings of SPIE: The International Society for Optical Engineering
ConferenceIntegrated Optics: Physics and Simulations II, 13 April 2015 through 15 April 2015
ISSN0277-786X
ISBN9781628416374
Volume9516
Article number95160I
SubjectFabrication; Fibers; Finite difference time domain method; Integrated optics; Light; Optical fiber fabrication; Optical fibers; Optical interconnects; Photonic devices; Photonics; Refractive index; Silicon on insulator technology; Telecommunication; Time domain analysis; Datacommunications; Dielectric reflectors; Grating couplers; Silicon photonics; Sub-wave length grating; Diffraction gratings
AbstractSurface grating couplers are key components to couple light between planar waveguide circuits in silicon-on-insulator (SOI) platform and optical fibers. Here, we demonstrate by using simulations and experiments that a high coupling efficiency can be achieved for an arbitrary buried oxide thickness by judicious adjustment of the grating radiation angle. The coupler strength is engineered by subwavelength structures, which have pitch and feature sizes smaller than the wavelength of light propagating through it, thereby frustrating diffraction effects and behaving as a homogeneous media with an adjustable equivalent refractive index. This makes it possible to apodize the grating coupler with a preferred single etch fabrication process. The coupling efficiency of the grating coupler is optimized for operating with the transverse electric (TE) polarization state at the wavelengths near 1.3 μm and 1.55 μm, which are the bands relevant for datacom and telecom interconnects applications, respectively. The design and analysis of the grating coupler is carried out using two-dimensional (2-D) Fourier-eigenmode expansion method (F-EEM) and finite difference time domain (FDTD) method. The simulations show a peak fiber-chip coupling efficiency of -1:61 dB and - 1:97 dB at 1.3 μm and 1.55 μm wavelengths, respectively, with a minimum feature size of 100 nm, compatible with 193 nm deep-ultraviolet (DUV) lithography. The measurements of our fabricated continuously apodized grating coupler demonstrate fiber-chip coupling efficiency of - 2:16 dB at a wavelength near 1.55 μm with a 3 dB bandwidth of 64 nm. These results open promising prospects for low-cost and high-volume fabrication of surface grating couplers in SOI using 193 nm DUV lithography, which is now used in several silicon photonics foundries. It is also predicted that a coupling efficiency as high as - 0:42 dB can be achieved for the coupler structure with a bottom dielectric mirror.
Publication date
PublisherSPIE
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for Microstructural Sciences
Peer reviewedYes
NPARC number21276937
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Record identifiere5293759-af02-452e-a123-2b0fa393ef1c
Record created2015-11-10
Record modified2016-05-09
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