Fiber-chip edge coupler with large mode size for silicon photonic wire waveguides

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1117/12.2181547
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Name affiliation
  1. National Research Council Canada. NRC Institute for Microstructural Sciences
  2. National Research Council Canada. NRC Industrial Materials Institute
FormatText
TypeArticle
Proceedings titleIntegrated Optics: Physics and Simulations II
Series titleProceedings of SPIE; no. 9516
ConferenceSPIE Optics + Optoelectronics, April 13-15, 2015, Prague, Czech Republic
ISSN0277-786X
1996-756X
ISBN9781628416374
Article number95160K
Subjectfinite difference time domain method; integrated optics; laser pulses; multimode fibers; optical fibers; optical waveguides; photonic devices; refractive index; silicon on insulator technology; silicon oxides; time domain analysis; waveguides; 3D finite difference time domains; effective refractive index; high numerical apertures; mode transformation; planar waveguide circuit; silicon wire waveguides; single-mode optical fiber; transverse electric polarizations; optical fiber coupling
Abstract
Fiber-chip edge couplers are extensively used in integrated optics as one of the key structures for coupling of light between planar waveguide circuits and optical fibers. In this work, a new fiber-chip edge coupler concept with large mode size for coupling to submicrometer silicon photonic wire waveguides is presented. The coupler allows direct coupling to conventional SMF-28 optical fiber and circumvents the need for lensed fibers. We demonstrate by simulations a 95% mode overlap between the mode at the chip facet and a high numerical aperture single mode optical fiber with 6 μm mode field diameter (MFD). We also demonstrate a modified design with 89% overlap between the mode at the chip facet and a standard SMF-28 fiber with 10.4 μm MFD. The coupler is designed for 220 nm silicon-oninsulator (SOI) platform. An important advantage of our coupler is that large mode size is obtained without the need to increase buried oxide (BOX) thickness, which in our design is set to 3 μm. This remarkable feature is achieved by implementing in the SiO2 upper cladding two thin high-index Si3N4 layers. The high-index layers increase the effective refractive index of the upper cladding layer near the facet and are gradually tapered out along the coupler to provide adiabatic mode transformation to the silicon wire waveguide. Simultaneously, the Si-wire waveguide is inversely tapered along the coupler. The mode overlap at the chip facet is studied using a vectorial 2D mode solver and the mode transformation along the coupler is studied by 3D Finite-Difference Time-Domain simulations. The couplers are optimized for operating with transverse electric (TE) polarization and the operating wavelength is centered at 1.55 μm.
Publication date
PublisherSPIE
LanguageEnglish
Peer reviewedYes
NPARC number21276987
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Record created2015-11-10
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