Novel design of two-dimensional grating couplers with backside metal mirror in 250 nm silicon-on-insulator

We present the design of two-dimensional grating couplers working as polarization splitter in a 250 nm silicon-on-insulator platform. Optimized dimensions of two grating structures with circular and square etched holes are simulated achieving coupling efficiencies of -1.8 dB and -1.9 dB, respectively. A further optimization leads to a novel two-dimensional coupler with aperiodic gratings and rectangular etched holes showing a coupling efficiency of -1.7 dB at 1.55 μm.