Theoretical and experimental investigations of the reorientation of liquid crystal molecules induced by laser beams

Theoretical investigations, relying mainly on numerical solutions of the non-linear differential equations of the reorientation angle, are conducted for a wide range of parameters and for a number of physical configurations which include self-diffraction and fast transients. The experiments are performed using homeotropically aligned 5CD liquid crystalscells. In particular, the temporal evolution of a ring structure in the far field pattern and response to short pulses are investigated involving time scales from nanosecond to tens of seconds regions. Comparisons between experimental results and theoretical predictions show that excellent match can be achieved for any one experiment by the choice of parameters like optical anisotropy, elastic constant and viscosity, but when parameter values derived from different experiments are compared, these parameters turn out to depend on the experimental conditions.