Infrared laser wave mixing and optical limiting with nematic liquid crystal films.

The passage of one (or two) laser beams through a highly nonlinear medium is accompanied by several effects. When a laser beam passes through a highly nonlinear thin film, the transmission will undergo various forms of spatial intensity distribution (self-focusing, defocusing, bistability, bending, etc.) that can be utilized in optical switches and limiters. When two laser beams are mixed in the medium, mutual exchange of energy and creation of new diffracted beams can be used for image/beam manipulaiations, amplifications, and combining. Theoretical calculations made of some fundamental aspects of these effects as well as feasibility types of calculation for some switching, optical limiting, and amplification devices are presented. Results of experiments based on the extraordinarily high-thermal-index gradient of nematic liquid crystals near the phase transition temperature are described.