Linear and quadratic electrooptic effects in antiferroelectric liquid crystals

The electrooptical effects occurring in antiferroelectric liquid crystals were investigated. The optical response was calculated, assuming that the external electric field coupled linearly to the residual spontaneous polarization (appearing due to the presence of helical structure) and quadraticaly to the dielectric anisotropy. The calculation showed that the electrooptic response contains components of both fundamental and second harmonic frequency. The per formed experiments demonstrated a good qualitative agreement with the results of calculations. The measurements of linear and second-order electrooptic effects can be a useful tool for precise determination of phase transitions between various smectic phases.