Analysis of Cavity-Mode Lasing Characteristics from a Resonator with Broadband Cholesteric Liquid-Crystal Bragg Reflectors

Abstract

Detailed optical lasing characteristics in liquid crystal (LC) microlasers consisting of multiple polymer cholesteric LC (PCLC) layers are presented as broadband resonators sandwiching a layer of thick gain media, dye-containing nematic LC (NLC) or isotropic liquid, in between. Multiple lasing emission peaks due to Fabry-Perot cavity modes are observed for both gain media, and their polarization characteristics investigated. To analyze lasing characteristics, specified eigen modes are defined, the polarization states of which are maintained before and after passing through the broadband resonator, and obtained for the present full system by using the Berreman 4 x 4 matrix method. Using these specified eigen modes, the optical density for each mode is calculated and compared with the experimental results, and shows good agreement. Finally, lasing characteristics between the resonators with NLC and isotropic gain media are compared, and the advantages of adopting dye-doped NLC gain medium are shown for tunable red, green, blue lasing in a microlaser system with a broadband resonator.