Ferroelectric ordering and electroclinic effect in chiral smectic liquid crystals

Ferroelectric ordering, the electroclinic effect and chiral smectic C (SmC*) - smectic A (SmA*) phase transitions in thin planar ferroelectric liquid crystal (FLC) cells are studied by means of linear electrooptic and second harmonic generation techniques. The ferroelectric switching is detected in biased FLC cells by measuring azimuthal dependences of linear and nonlinear responses. The applied DC-electric field rotates the FLC symmetry axis with initial and final orientations in the cell plane. Comparative studies of the switching behavior in reflection and transmission allows to distinguish the contributions from the bulk and the sub-surface layers of the cell. The analysis of temperature dependence shows the existence of a strong surface coupling. The temperature dependent nonlinear polarization shows a critical behavior corresponding to the superfluid model.