All-optical nonlinear switching cell made of photonic crystal.

We analyze and propose a directional optical coupler embedded in photonic crystal, which is driven by an external command signal. Therefore, this switching cell can work in an all-optical switch. The switching method uses a low-power external command signal, inserted in the central coupling region, which acts as another waveguide. The switching process is based on the change from the bar state to the cross state due to the external command signal. In our simulations we used the plane wave expansion method, finite-difference time-domain method, and our own binary propagation method.