Ultralow Power Nonlinear Response in an Si Photonic Crystal Nanocavity

Optical nonlinear response and bistability behavior are observed in a fabricated silicon photonic crystal three defect-long (L3) nanocavity. The L3 cavity, which is coupled with a photonic crystal waveguide, has a quality factor of 60 000. Optical nonlinear response of the L3 cavity is observed at 4.65- μW input power, and the threshold power for optical bistability in the L3 cavity is 26.1 μW, which are the lowest values for silicon L3 cavities. A nonlinear coupled mode model is established to analyze nanocavity characteristics systematically. Numerical simulation results indicate that the ultralow power nonlinearity is due to the high Q factor and large thermal resistance of the nanocavity.