Nonlinear Raman spectroscopy of liquid crystals: orientational alignment and switching behaviour in a ferroelectric liquid crystal mixture

摘要

Picosecond inverse Raman spectroscopy has been employed to probe the alignment behaviour and switching characteristics of a 6 μm thick ferroelectric liquid crystal based on a host mixture of fluorinated phenyl biphenyl-carboxylates and a chiral dopant. Optical bistability is observed in the Raman signal on application of dc electric fields of opposite polarity. For particular polarities of the applied field, the Raman signals display a cos~4 θ dependence on the angle of rotation around the beam direction. Reorientational rate constants of 300 μs and 590 μs are observed for the aromatic core at the high-voltage limit for the rise and decay of the 1600 cm~(-1) Raman signal on application of a switching ac electric field.