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Research Paper

Journal of the Optical Society of Korea 2016; 20(2): 291-299

Published online April 25, 2016 https://doi.org/10.3807/JOSK.2016.20.2.291

Copyright © Optical Society of Korea.

Comparative Study of Uniform and Nonuniform Grating Couplers for Optimized Fiber Coupling to Silicon Waveguides

Moon Hyeok Lee, Jae Young Jo, Dong Wook Kim, Yudeuk Kim, and Kyong Hon Kim

Department of Physics, Inha University

Received: November 25, 2015; Revised: February 18, 2016; Accepted: February 19, 2016

We have investigated the ultimate limits of nonuniform grating couplers (NGCs) for optimized fiber coupling to silicon waveguides, compared to uniform grating couplers (UGCs). Simple grating coupler schemes, which can be fabricated in etching steps of the conventional complementary metal-oxide semiconductor (CMOS) process on silicon-on-insulator (SOI) wafers without forming any additional overlay structure, have been simulated numerically and demonstrated experimentally. Optimum values of the grating period, fill factor, and groove number for ultimate coupling efficiency of the NGCs are determined from finite-difference time-domain (FDTD) simulation, and confirmed with experimentally demonstrated devices by comparison to those for the UGCs. Our simulated results indicate that maximum coupling efficiency of NGCs is possible when the minimum pattern size is below 50 nm, but the experimental value for the maximum coupling efficiency is limited by the attainable fabrication tolerance in a practical device process.

Keywords: Grating couplers, Integrated optics devices,

OCIS codes: 230.1950; 230.3120; 130.2790

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