Mode coupling by scattering in chiral nematic liquid crystal ring lasing

Lasing in dye-doped chiral nematic liquid crystal can be realized with low pump energy and relatively high efficiency thanks to the high reflectivity of the periodic structure. When the helical axis is oriented perpendicular to the substrates, the main lasing peak is normal to the substrates. In some cases, ring lasing of a particular wavelength is observed into an emission cone with axial symmetry. In this paper we explain how scattering of light in the liquid crystal layer leads to optical coupling between normal modes and inclined modes. Based on a numerical model that takes into account spontaneous emission, gain and scattering we show that scattering leads to emission characteristics that are similar to experimental results. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement