ANOMALOUS BEHAVIOR OF PHOTOACTIVE FREESTANDING SMECTIC FILMS UNDER ILLUMINATION

Illumination of free-standing smectic films doped with azo dyes produc es bubbles in the SmA phase; these cannot be observed in bulk samples. The bubbles appear in the films with some time delay after the beginn ing of illumination. This time delay depends linearly on (T-IA -T), wh ere T-IA is the smectic A-isotropic transition temperature. This depen dence shows that illumination induces in the interior of the films a s mectic A-isotropic phase transition. The SmC in-plane director field configuration depends on the orientation of the polarization plane of the incident light. In the SmC phase no bubbles are observed even on continuous illumination.