Hydrodynamically controlled optical propagation in a nematic fiber

Abstract

We show that a cylindrical guide whose core is a liquid crystal (LC), having initially the escaped configuration, can be mechanically controlled. Indeed, we show how the nematic textures, distorted by a pressure gradient applied along the cylinder, are able to significantly alter the propagation of the optical fields. Above certain critical pressure, the fiber only conducts the optical beams within two coaxial but unconnected regions, where the light can propagate independently. We demonstrate this result by using two complementary formalisms. For multimodal waveguides in the small wavelength limit and by performing exact numerical calculation of the transverse magnetic (TM) modes distribution in the guide. The last calculation not only corroborates the asymptotic results of the geometrical analysis, but evinces the way in which the signals propagating in each region overlap and interact each other, when their wavelength are larger than the regions thickness.