Mode Control in Planar Waveguide Grating Couplers With Double Surface Corrugation

Grating couplers with double surface corrugation are proposed to adjust the resonance behavior of both TE and TM modes simultaneously. Through proper selection of parameters, we designed a polarization-independent grating coupler operating at 1.55-μm telecommunication wavelength. Efficiency is achieved at around 55% for both TE and TM modes, and the polarization-dependent loss is <; 0.05 dB within the spectral window from 1544 to 1561 nm. Furthermore, a double-channel grating coupler is proposed to excite the TE and TM modes at 1.31 and 1.49 μm, respectively. The achievable efficiency is around 60% for both channels with good uniformity.