High-efficiency broad-bandwidth sub-wavelength grating based fibre-chip coupler in SOI

We report a comprehensive study on the performance of uniform and non-uniform based subwavelength grating couplers in Silicon-on-Insulator. The two performance metrics, coupling efficiency and bandwidth enhancement and trade-offs is 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 the 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.