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

We demonstrate experimentally that the transverse shape of the laser beam can strongly affect the laser-induced molecular reorientation in nematic liquid crystals. In this paper we studied only the case of elliptical beam cross-section. In this case, a relatively strong extra-torque was observed tending to reorient the liquid crystal director parallel to the ellipse major axis. The extra-torque is zero for circular beam cross-section and increases as the beam cross-section becomes more and more elliptical.