Optical nonlinearities in the supercooled phase of nematic liquid crystal drops

Abstract Raman scattering with different incident powers and varying chopping frequencies of the input laser is used to study the microscopic origin of the third-order nonlinear optical susceptibility (χ 3 ) of a nematic liquid crystal drop. Thermal self-focusing arises in the nematic state if intrinsic residual absorption is present. Conversely, self-focusing associated with molecular reorientations comes in view at low input powers and produces stimulated Raman scattering if the drop is supercooled below the melting point. The latter effect is related to the substantial increase in the time scale for molecular reorientations in the supercooled nematic. The possibility of using χ 3 and Raman scattering for the study of the dynamics of supercooled organic liquids is suggested.