Whispering gallery mode lasing in mesomorphic liquid crystal microdroplets

Abstract

In recent years, investigation on the non-display applications of liquid crystals has increased considerably. One of the emerging applications is whispering gallery mode (WGM) lasing. Here, we report experimental studies on the morphology and WGM lasing in nematic (N), smectic-A (SmA) and smectic-C (SmC) microdroplets dispersed in a highly transparent and low refractive index perfluopolymer. The mesomorphic microdroplets, obtained by varying the temperature, exhibit radial director configuration. The SmA microdroplets are found to be highly stable and robust against mechanical stress compared to the N and SmC microdroplets. We study lasing properties such as intensity, threshold pump energy and linewidth, and show that overall the SmA microdroplets are superior to the N and SmC microdroplets. The experimental results are discussed based on the orientation of the dye molecules, director fluctuations and tilting at the interface.