Hybrid Silicon All‐Optical Switching Devices Integrated with 2D Material

Abstract Hybrid all‐optical switching devices that combine silicon nanocavities and 2D semiconductor materials are proposed and demonstrated. By exploiting the refractive index modulation caused by photo‐induced carriers in the 2D material instead of the silicon substrate, the switching speed limitation imposed by the carrier lifetime of silicon is overcome while maintaining a low switching energy. Air‐mode photonic crystal nanobeam cavities capable of efficient interaction with 2D materials are fabricated, and molybdenum ditelluride, a 2D material with rapid carrier recombination, is transferred onto the cavities. The molybdenum ditelluride flake is excited by an optical pump pulse to shift the resonant wavelength of the cavity for switching operation. All‐optical switching operations are achieved on the time scale of tens of picoseconds while requiring low switching energies of a few hundred femtojoules.