Lasing chirality control of thin-film defect-mode lasers based on cholesteric liquid crystal polymer mirrors

Abstract

This work investigates the emission chirality of a chiral distributed Bragg reflector (DBR) laser, which is composed by incorporating an isotropic medium containing laser dye between two cholesteric liquid crystal polymer films. The emitted laser showed different ratios of circularly polarized states corresponding to different pitch numbers of the chiral mirror. Through Berreman matrix numerical calculations and experimental results, we validated the variations of the emission chirality coupling in the defect resonance mode as a function of pitch numbers, as well as the effect of the defect layer thickness on the wavelength and mode number of the emitted laser. We also observed the cone-shape emission and examined the threshold of the lasing. The results successfully demonstrated the realization of DBR laser with controllable orthogonal circular polarization ratios in the emitted laser light. These results offer considerable potential for the development of micro-laser sources with different emission chirality and wavelengths for various applications.