Theory and experiment on optical transverse intensity bistability in the transmission through a nonlinear thin (nematic liquid crystal) film

A theory is presented for the transverse intensity distribution bistability of a Gaussian optical beam after its passage through a nonlinear thin film. The equations governing the intensity distribution are cast in the form analogous to optical bistability in a longitudinal cavity (a Fabry-Perot interferometer), i.e., into two coupled transcendental equations from which multiple solutions are obtained. This formalism allows one to examine various physical approximations in obtaining the equations, and to improve on these approximations. It also lucidly illustrates the mechanisms of transverse intensity distribution bistability. The theoretical predictions are verified with quantitative experimental results on thin films of nematic liquid crystals.