Self-focusing of laser light in the isotropic phase of a nematic liquid crystal

Self-focusing of ruby laser light is studied as a function of sample length and temperature in the isotropic phase of nematic liquid-crystal MBBA. The critical power for self-focusing, 0.36 kW, observed near the phase transition temperature is a factor of 20 times less than that for CS2. The corresponding nonlinear index 4.4 × 10−10 esu is the largest value known so far for any material.