Direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal

Abstract

We demonstrate a direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal (CLC) in a homogeneous cell coated with a metallic mirror on the inner side of a glass substrate. Due to coherent superposition of two orthogonal polarization states, the output laser light becomes linearly polarized and its output energy is greatly enhanced. Moreover, the linear polarization direction angle is proportional to the product of the CLC effective birefringence and cell gap. Hence direction tunable laser devices can be demonstrated by controlling the cell gap and the operating temperature.

Polarization-tunable chiral nematic liquid crystal lasing

“…Accordingly, extensive work has been performed on the lasing action of CLCs. [4][5][6][7][8] Many works have studied the control of the lasing action in the dye-doped CLC system using external stimuli, such as heat, 9,10 electrical field, 11,12 optical field, 13,14 and mechanical stress. 15 The chiral structure of dye-doped CLCs causes laser emission that is generated to be typically circularly polarized in the same sense as the cholesteric helix.…”

Enhanced laser emission in opposite handedness using a cholesteric polymer film stack

“…Currently, there are several factors that limit the output power from the CLC polymer lasers, such as dyebleaching during the UV polymerization process and deformation of the ordered cholesteric structure due to insufficient surface anchoring energy. In order to increase the output power and, in the meantime, lower the threshold, different approaches have been proposed, such as adding external reflectors [11][12][14][15][16] or stacking multiple active polymer films [17]. Adding a cholesteric passive reflector helps to enhance the laser output based on a further coherent amplification [15] while the enhancement from a metallic mirror essentially results from the second pump of the active layer [16].…”