Abstract

When an extraordinary optical wave is obliquely incident onto a homeotropically aligned Nematic Liquid Crystal (NLC) film, a steady-state reorientation of the molecular director is induced which is proportional to the intensity of the wave. For normal incidence, there is a threshold in the light intensity below which no molecular reorientation can be produced (1). A completely different phenomenon is observed when an ordinary wave is sent onto the sample at small incidence angle. The characteristic far-field diffraction pattern due to self-phase modulation, in fact, is stable in the former case and unstable in the latter, where the number of the aberrational rings varies periodically in time. Although this phenomenon was observed some years ago (2), a satisfactory explaination is not yet available.

© 1988 Optical Society of America