The orientational mechanism of nonlinearity and the self-focusing of He-Ne laser radiation in nematic liquid crystal mesophase (theory and experiment)

A giant optical nonlinearity of self-focusing type in the oriented mesophase of nematic liquid crystals (NLC) due to the director reorientation under the action of a light wave field is predicted. Self-focusing of He-Ne laser radiation with power ～10^?2 W and power density ～50 W/cm² in a planar oriented 60 μm thick NLC layer has been carried out experimentally. The measured value of the nonlinearity effective constant ?₂ = 0.07 cm³/erg corresponds to theoretical predictions, and turns out to be larger than the CS₂ nonlinearity by ? 10⁹ times.