ELECTROOPTIC EFFECT AND 3RD-ORDER NONLINEAR DIELECTRIC RESPONSE IN ANTIFERROELECTRIC LIQUID-CRYSTALS

We have theoretically studied the electro-optic effect and third-order nonlinear dielectric response in antiferroelectric liquid crystals on the basis of phenomenological equations of motion. It has been found that the antiferroelectric soft and Goldstone modes can be excited by an electric field, though they respond to the square of the field but not to the field itself, and they modulate the dielectric constant both for the visible light and low frequencies, contributing to the electro-optic effect and the third-order nonlinear dielectric response, respectively. The transmitted intensity and the third-order dielectric constant were theoretically derived, and the former was compared with experimental results.