NON LINEARLY INDUCED SELF WAVE-GUIDING STRUCTURE IN DYE-DOPED NEMATICLIQUID-CRYSTALS CONFINED IN CAPILLARIES

We report on experiments dealing with the propagation of a collimated laser beam in a dye doped nematic confined in a capillary of optical f iber size. The nematic is aligned in a such a way that the source beam is self focused. The behavior of the beam - focusing, multifocus regi me, filamentation and undulation - already observed in larger cylindri cal geometry and pure nematic is shown here to be reproduced in the dy e doped medium, at much lower powers. Another feature is reported here : a stable regime looking like a waveguide appears in certain conditio ns, in which the beam to propagate in a narrow tube. This regime is si mply modeled in terms of saturated reorientation of the nematic. (C) 1 998 Optical Society of America.