Design of high-Q polystyrene nonlinear cavity for ultrafast all-optical switching in mid-infrared photonic crystal slabs with cavity-waveguide structure

In this study, we design a nonlinear cavity with ultrafast response speed material in photonic crystal slabs for all-optical switching. We consider triangular lattice photonic crystal slab made from air holes in anisotropic Tellurium background which is on top of Teflon substrate. The cavity itself is then created by enlarging one of the air holes and infiltrating it with polystyrene. Optimization of structural parameters yields a single mode cavity with quality factor of Q=2.5×104Q=2.5×104, by using the three-dimensional finite-difference time-domain (FDTD) simulation and filter diagonalization approach. This shows great enhancement compared with previous studies in which organic polymer materials have been used. In order to study the coupling characteristic of cavity mode and waveguides, the nonlinear cavity is placed between two waveguides, symmetrically. At the end, we used the FDTD method to investigate shift magnitude of cavity mode resonance frequency under pump light. The designed structure can be helpful to achieve extremely fast response speed in all-optical switching devices with high efficiency in the mid-infrared wavelength range.