  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.
