Abstract

We present a quantitative theoretical and experimental study of the transverse dependence of nematic liquid crystal axis reorientation by a laser beam of beam sizes that are comparable to the liquid crystal film thickness. As a result of the interplay between the boundary torques and the torques exerted by the molecules outside the laser beam on the molecules within the laser beam, interesting nonlocal effects arise. The natures of the torque balance equations and the solutions for the reorientation profile are very different for laser polarizations that are normal, or obliquely inclined, to the director axis. If the laser polarization is perpendicular to the director axis there is a threshold intensity for reorientation to occur. The relative width of the reorientation profile (with respect to the laser beam waist) can be larger (or smaller) than unity depending on whether the laser beam size is smaller (or larger) than the film thickness. On the other hand, if the beam polarization is not normal to the director axis, the width of the response is always larger than the laser beam waist. These nonlocal behaviors have profound effects on transverse optical bistability switching behaviors and switching intensities.

© 1986 Optical Society of America