NONLINEAR RAMAN-SPECTROSCOPY OF LIQUID-CRYSTALS - ORIENTATIONAL ALIGNMENT AND SWITCHING BEHAVIOR IN A FERROELECTRIC LIQUID-CRYSTAL MIXTURE

Picosecond inverse Raman spectroscopy has been employed to probe the a lignment behaviour and switching characteristics of a 6 mu m thick fer roelectric liquid crystal based on a host mixture of fluorinated pheny l biphenyl-carboxylates and a chiral dopant. Optical bistability is ob served in the Raman signal on application of de electric fields of opp osite polarity. For particular polarities of the applied field, the Ra man signals display a cos(4) theta dependence on the angle of rotation around the beam direction. Reorientational rate constants of 300 mu s and 590 mu s are observed for the aromatic core at the high-voltage l imit for the rise and decay of the 1600 cm(-1) Raman signal on applica tion of a switching ac electric field.