Molecular reorientation of a nematic glass by laser-induced heat flow

Laser-induced birefringence patterns which break the symmetry of the experimental setup have been observed in a low molar mass anisotropic glass with nematic orientational order under a polarizing microscope. It is shown that the observed spatial modulations in birefringence can be explained by laser-induced heat flow and stress, leading to molecular reorientation which is then frozen and stored in the glassy state if the optical excitation is switched off. The experimental findings can be regarded as a manifestation of heat-flow alignment caused by a spatially inhomogeneous temperature field.