Liquid crystal photorefractivity – towards supra-optical nonlinearity

Abstract A review of the basic mechanisms of optically induced refractive index modification in liquid crystalline materials is presented. We describe how the use of methyl-red dye or an azobenzene liquid crystal will dramatically enhance the nonlinear optical responses of typical nematic liquid crystals (NLC). The intensity dependent refractive index changes in these materials are characterized by nonlinear coefficients of over 1 cm 2 / W . The principal contributing mechanisms are orientational photorefractivity associated with photo-induced space charge fields, dopant-nematic molecular torque, and order parameter modification caused by trans–cis isomerization of the azo-dopants.