Polarimetric study of the optically induced dynamical behaviour in nematicliquid crystal films

We report the photopolarimetric study of the molecular director dynamics ob served in a homeotropically aligned nematic liquid crystal layer under the action of a small angle incident s-polarised laser beam. For increasing lig ht intensities several interesting dynamical regimes have been observed. In order to accomplish this aim, we propose a new experimental apparatus whic h, using a pump-probe technique and a new polarimeter (four-detector polari meter), allows us to measure with a good resolution the variation in the po larisation state of the laser probe during the molecular reorientation indu ced by a laser beam in the sample. A preliminary description of the dynamic al regimes, based on the analysis of the Fourier spectra and the autocorrel ation functions of the measured time series, have been reported. (C) 2000 E lsevier Science B.V. All rights reserved.