Field driven helix unwinding in thick AFLC cells

The interaction of the antiferroelectric helix with an electric field appli ed perpendicular to its axis is investigated, A two stage switching process is observed, in which the helix unwinds to an intermediate state in the pr etransitional regime, at voltages below the threshold for antiferroelectric to ferroelectric switching. A series of experimental studies and theoretic al modelling show that the intermediate state is an antiferroelectric state in which the directors lie in the plane containing the applied electric fi eld and the smectic laver normal. The mechanism for the unwinding process i s the interaction of the applied field with an induced polarisation, which arises from a distortion to the antiferroelectric ordering.