DYNAMICS OF HELIX DEFORMATION IN A CHIRAL SMECTIC-C-ASTERISK LIQUID-CRYSTAL - OPTICAL EXPERIMENTS AND MODELING

Measurements are reported for the optical response in the classical el ectroclinic geometry of a chiral smectic-C liquid crystal. The sample was subjected to a weak ac electric field that was applied perpendicu lar to the helical axis. The response was found to be linear in field for E much smaller than the critical field for complete unwinding, and nearly independent of sample thickness, falling off approximately as f(-1) in the frequency range 200 < f < 20000 Hz. The behavior is model ed by a time-dependent Landau-Ginzburg model in which both the local p olarization and dielectric anisotropy are coupled to the electric fiel d.