Optical reorientation in nematic liquid crystals controlled by the laser beam shape

We demonstrate experimentally that the transverse shape of the laser beam c an strongly affect the laser-induced molecular reorientation in nematic liq uid crystals. In this paper we studied only the case of elliptical beam cro ss-section. In this case, a relatively strong extra-torque was observed ten ding to reorient the liquid crystal director parallel to the ellipse major axis. The extra-torque is zero for circular beam cross-section and increase s as the beam cross-section becomes more and more elliptical. (C) 1999 Publ ished by Elsevier Science B.V. All rights reserved.