Nonlinear Optical Properties of Ionic Thermotropic and Lyotropic Liquid Crystals

This work presents the analysis of experimental research on the optical and nonlinear optical properties of two different representatives of metal alkanoate-based liquid crystals. Namely, ionic lyotropic liquid crystals of potassium caprylate doped with electrochromic viologen additives, and anisotropic glasses of ionic thermotropic liquid crystals of cobalt alkanoates of the homologous series (n = 7, 9, 11) and their multicomponent mixtures. Prior to the nonlinear optical experiment, the optical absorption spectra of all samples were investigated. For proposed absorbing media, laser-induced dynamic grating recording under the action of nanosecond laser pulses has been realised, observed and analysed. The studied materials were found to exhibit cubic optical nonlinearity, with cubic nonlinear susceptibility χ(3) and hyperpolarizability γ values comparable to the best organic dyes. The possible mechanism of nonlinear response in the systems studied was considered on the basis of the data obtained. The nonlinear response mechanism is related to the non-linear polarisation of the π-electrons in the field of the laser radiation.