All-optical switching and multistability in photonic structures with liquid crystal defects

We demonstrate that one-dimensional photonic crystals with pure nematic liquid-crystal defects can operate as all-optical switching devices based on optical orientational nonlinearities of liquid crystals. We show that such a periodic structure is responsible for a modulated threshold of the optical Fŕedericksz transition in the spectral domain, and this leads to all-optical switching and light-induced multistability. This effect has no quasistatics electric field analog, and it results from nonlinear coupling between light and a defect mode.