Lasing Thresholds of Cholesteric Liquid Crystals Lasers

Cholesteric liquid crystals (CLCs) are one dimensional photonic band-gap materials. Due to distributed feedback, low threshold mirrorless lasing can occur in dyedoped and pure CLCs. In order to optimize the lasing conditions, we have studied the dependence of the lasing threshold on dye concentration and sample thickness. In particular, we have studied dye concentrations in the range of 0.1-3.0 wt%, and cell thicknesses are in the range of 5-50 ?m. We have found that the system has a shallow lasing threshold minimum and can operate efficiently in the range of dye concentrations of 0.3-2.4wt% and sample thicknesses of 10-50 ?m. We discuss the physical processes responsible for the observed behaviour.