Photonic crystal switches based on nonlinear directional couplers

In this paper, the all optical switch based on nonlinear photonic crystal directional coupler in both, hexagonal and square lattice structure has been simulated and analyzed by the finite difference time domain (FDTD) method. The refractive index of the nonlinear central row of the coupler is increased by the pump signal. Hence, it works in the nonlinear state and the light is guided to the cross output. We have tried to reduce the required power for switching and increase the coupling efficiency by modifying the bends structure in the directional coupler which is implemented in square lattice. Therefore, the input signal beam can be controlled to be exchanged between two output ports to earn the highest output power ratio and the smallest amount of power required for nonlinear performance.