Polarimetric study of the optically induced dynamical behaviour in nematic liquid crystal films

We report the photopolarimetric study of the molecular director dynamics observed in a homeotropically aligned nematic liquid crystal layer under the action of a small angle incident s-polarised laser beam. For increasing light intensities several interesting dynamical regimes have been observed. In order to accomplish this aim, we propose a new experimental apparatus which, using a pump-probe technique and a new polarimeter (four-detector polarimeter), allows us to measure with a good resolution the variation in the polarisation state of the laser probe during the molecular reorientation induced by a laser beam in the sample. A preliminary description of the dynamical regimes, based on the analysis of the Fourier spectra and the autocorrelation functions of the measured time series, have been reported. (C) 2000 Elsevier Science B.V. All rights reserved.