Intrinsic and photo-induced optical properties of photoaligning azo-based materials coupled with liquid crystal systems

Photoaligning azobenzene-based PAAD materials can show strong photoresponse without a surface relief pattern. We report an experimental investigation of PAADs optical properties, such as complex refractive indices and optically induced birefringence. Formation of photoinduced phase gratings in 20-50 nm, thin PAAD layers is demonstrated, with a strong dependence of diffraction on the probe beam polarization. The light induced diffraction in liquid crystal systems coupled with PAAD films is also studied. We demonstrate a stable and strong diffraction grating, which can be rewritten by illumination or switched off by reorienting the liquid crystals with a bias voltage.