High efficient photonic band-edge cholesteric liquid crystal lasers

Abstract

In this paper, we demonstrated a new dye-doped cholesteric liquid crystal (CLC) photonic band edge laser with emission enhanced by an external cholesteric resonator. As one-dimensional photonic crystal, the 5-&mgr;m dye-doped cholesteric liquid crystal cell generates circularly polarized laser emission at its photonic band edge. When sandwiched between two 5-&mgr;m cholesteric liquid crystal mirrors whose reflection band reflects the laser emission from the central dye-doped CLC laser, the emission can be enhanced by ~800X. In experiment, a second-harmonic Q-switched Nd-YAG pulsed laser is used to pump the CLC laser assembly at normal incidence. The detected laser emission is elliptically polarized and is still located at the band edge wavelength of the central CLC cell. The beam divergence is decreased by ~10X due to an increased cavity length. Theoretical analysis using 4x4 transfer matrix and scattering matrix has shown that the circular resonator produces transmission peaks based on Fabry-Perot effect inside reflection band and, moreover, the transmission peak at the band edge of central CLC can be well-preserved. Both experiment results and simulation results are present in good agreement.