Self-waveguiding in an isotropic channel induced in dye doped nematic liquid crystal and a bent self-waveguide

A Gaussian beam emerging out of a fibre and launched into a dye doped nematic liquid crystal experiences self-waveguiding for appropriate input power in the milliwatt range. This is a consequence of the large thermal non-linearity exhibited by such a material. Two modes have been reported, occurring for two different ranges of input powers. It has been shown previously that the high power mode occurs in the isotropic phase, the light being trapped within a tube of isotropic material. In this paper, the onset of the phase transition is experimentally detailed. A simulation of the beam propagation in both modes of self-waveguiding is presented as well, in full agreement with the experimental results obtained on the distribution of the optical field in a cross section of the waveguide. Finally, it is shown how it is possible to drive a probe beam through bent self-waveguides, generated by such isotropic tubes.