High-efficiency broad-bandwidth subwavelength grating-based fiber-chip coupler in silicon-on-insulator

We report a comprehensive study on the performance of uniform and nonuniform-based subwave-length grating couplers in a silicon-on-insulator. The two performance metrics, coupling efficiency, bandwidth enhancement, and tradeoffs are presented. We also present design parameters to achieve high-efficiency and broadband operation based on the detailed study of various loss mechanisms in the grating. Based on a detailed analysis, subwavelength grating coupler designs with efficiency as high as 84% with a 1-dB bandwidth of 50-nm and 98% with a 44-nm 1-dB bandwidth is presented. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE