Ultracompact low-loss nonvolatile silicon photonic phase shifter with Sb2Se3 embedded into the waveguide slot

We propose and experimentally demonstrate an ultracompact low-loss nonvolatile silicon photonic phase shifter by embedding phase change material Sb2Se3 into the waveguide slot. The device performance is characterized by an unbalanced Mach-Zehnder interferometer (UMZI), with Sb2Se3 deposited in the longer arm. Reversible switching of Sb2Se3 state is achieved by applying laser pulses with appropriate power and pulse width through direct laser writing (DLW). This novel embedded architecture significantly enhances the optical mode overlap with Sb2Se3, achieving a high phase shift efficiency of 0.178 π μm-1 and a low waveguide propagation loss of 0.027 dB μm-1.