Electrically tunable prism grating based on a liquid crystal film with a photoconductive layer

This study is the first to investigate an optically addressed, electrically tunable prism grating based on homogeneously aligned liquid crystals (LCs) with a photoconductive layer. A conductivity-gradient electrode-like grating pattern of the polymer layer results in a spatially periodic gradient of the effective electric-field drop, producing a prism grating with a spatially periodic LC gradient reorientation. The asymmetric diffraction pattern can be adjusted by varying the dc voltage. The first-order diffraction efficiency is 64% at optimal conditions. The proposed prism grating exhibits extremely low diffraction noise in the off state, a high switching contrast in the on-off state (similar to 1000), simplicity of fabrication, and high controllability at a low voltage range (0 to 0.4 V/mu m). (C)2012 Optical Society of America