Self-focusing effects in a nematic liquid crystal at 10.6 $\mathsf{\mu}$m

E7 is a room temperature nematic liquid crystal that presents both a high temperature nematic-to-isotropic transition and a high positive dielectric anisotropy. The optical characteristics of this liquid crystal have been widely investigated in the visible region of the spectrum, while less experiments have been performed in the middle infrared spectral region, where, nevertheless, potential applications are important. We investigate the self-focusing of a middle infrared laser beam when it passes through a film of E7. We also take into account the heating of the liquid crystal film caused by the partial absorption of the laser light by means of a thermographic technique. A theoretical interpretation of the self-focusing phenomenon is given in terms of the reorientation of the molecules with respect to their unperturbed direction and an estimation of the average value of the elastic constants of the liquid crystal is given by fitting the experimental data with the theoretical model.Received: 16 April 2003PACS: 42.70.Df Liquid crystals - 42.65.-k Nonlinear optics - 42.55.Lt Gas lasers including excimer and metal-vapor lasers