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Abstract
The threshold intensity for the laser induced deformation of nematic liquid crystals is calculated as a function of the spot size of the illuminating beam. It is shown, that due to the small size of the light spot, the optical threshold is higher than that expected from the Fredericks threshold formula for static electric fields of infinite large dimension in the cell plane. Experimental data measured on a homeotrop OCB (octyl-cyano-byphenyl) sample fit well the theoretical curve. Results obtained on the temperature and wavelength dependence of the threshold can be interpreted on the basis of the given theory.