INVERSE RAMAN-STUDY OF LIQUID-CRYSTALS

Picosecond inverse Raman spectroscopy has been used for studying the R aman spectra, alignment behaviour, and switching characteristics of th e nematic liquid crystal 4-pentyl-4'-cyanobiphenyl (5CB) and a ferroel ectric liquid crystal based on a host mixture of fluorinated phenyl bi phenylcarboxylates and a chiral dopant. The orientational ordering of the liquid crystal (LC) molecules has been altered by electric fields applied across the samples. The change of orientation has been monitor ed by detecting the inverse Raman signal arising from a selected Raman transition. For the nematic liquid crystal, the measured reorientatio nal time constants are in the range 10-150 ms, whereas those for the f erroelectric liquid crystal samples are below I ms. (C) 1997 Elsevier Science B.V.