Electric Field Dependence of Lasing Wavelength in Cholesteric Liquid Crystal with an In-Plane Helix Alignment

Abstract

The authors report continue tuning of the lasing wavelength in cholesteric liquid crystals (ChLCs) by an applied electrical fields. Although the pitch length and the corresponding lasing wavelength is sensible to external fields, only a discrete shift in the pitch is observed in the conventional cell configuration where the helix axis is lying the cell-normal direction, since the molecules are anchored to a single direction at the substrate interfaces. In this study, continuous wavelength tuning is achieved by laying the helix in the cell-plane direction, mitigating the effects of anchoring: this alignment is attained simply by applying an electric field while cooling the sample from the isotropic state, in a planarly rubbed sandwich cell. We also show that the tuning characteristics as that predicted based on calculations using the elastic theory.

Keywords:

• Cholesteric liquid crystal
• in-plane helix alignment
• lasing action