OBSERVATION OF LIGHT-INDUCED HYDRODYNAMIC INSTABILITIES IN A NEMATIC LIQUID-CRYSTAL IN A SINGLE-MODE LASER-BEAM

Light-induced hydrodynamic instabilities have been discovered and studied in a nematic liquid crystal which is initially in a state of uniform orientation. The instabilities occur when a single-mode laser beam excites convective flows and dynamic orientation structures with a complex (and controllable) topology. These structures lead to a self-induced diffraction and to a scattering of light with an optical bistability. These effects stem exclusively from a multiple internal feedback which arises in a strongly absorbing nematic liquid crystal. These effects are observed in an all-optical experiment, without any additional quasistatic fields or initial temperature gradients.