Theoretical investigation of integratable photonic crystal nanobeam all-optical switching with ultrafast response and ultralow switching energy

High-performance all-optical switching is of paramount importance to realize integrated photonic circuit. Due to the ultra-sharp resonance mode, it is demonstrated that Fano resonance is far superior to Lorentz resonance for the implementation of all-optical switching. However, it is still a difficulty to realize an integratable all-optical switching with faster response and lower switching energy simultaneously. In this work, we propose double Fano resonances based all-optical switching composed of a silicon-polymer compound photonic crystal nanobeam (PCN) side-coupled with a photonic crystal nanobeam cavity (PCNC). The pump and probe wavelengths locate at the position of two Fano resonant modes. Introducing the excellent Kerr nonlinearity of polymer materials, all-optical switching dynamics are investigated explicitly by numerical pump-probe technique based on the finite-difference time-domain method. Associated with the sharp transmission profile of Fano resonance modes and excellent nonlinear optical property of polymer, sub-picosecond switching time and sub-picojoule switching energy can be realized simultaneously with in-plane pumping scheme. Such PCN-PCNC structures are compact and can be fabricated based on the silicon-on-insulator material, which are compatible with the complementary-metal-oxide-semiconductor technology. Our results eliminate the obstacles for the realization of high-performance optical switching, and unlock the potential for the construction of integrated photonic circuits.