Optical Manipulation in Liquid Crystals: Effects of Tight Focusing on Nonlinear Optical Reorientation.

We report a detailed analysis of the problem of nonlinear optical reorientation induced in a nematic liquid crystal by a tightly focused Gaussian beam under experimental conditions that prevent the effect of conventional trapping originated by optical gradient forces. Novel features arise under these conditions: no threshold effect; reduced reorientation if compared the one induced by a paraxial Gaussian beam, orientational singularity at the focal waist. [ABSTRACT FROM AUTHOR]