Ge2Sb2Se4Te1-assisted non-volatile silicon mode selective switch

A silicon waveguide mode selective switch based on optical phase-change material Ge2Sb2Se4Te1(GSST) is theoretically demonstrated. The mode switch formed by three cascaded asymmetric directional couplers (ADCs) allows the input TE11 mode to be selectively converted to TE21, TE31 or TE41 mode based on the state of GSST. Each ADC consists of the single-mode silicon waveguide and the GSST film covered multimode silicon waveguide. The phase change of GSST could adjust the effective index of GSST/Si hybrid waveguide, thereby implementing the mode conversion. The three-dimensional finite-difference time-domain (3D-FDTD) method is adopted for performance optimization. The simulation results show that the mode conversion efficiencies of TE11 to TE21, TE31 and TE41 mode are 89.96%, 92.87% and 90.94%, respectively. The proposed mode selective switch has good potentials in on-chip signal multiplexing.