Cholesteric liquid crystal laser in a dielectric mirror cavity upon band-edge excitation.

Low threshold laser action of dye-doped cholesteric liquid crystals (CLCs) is demonstrated using an input circularly polarized light whose handedness is the same as the cholesteric helix of the sample at the high-energy band edge of the reflection band. The mechanism originates from the dramatic increase of the photon density of state at the band edges. We also demonstrate an enhanced laser action of a CLC in a dielectric multilayer cavity. In such a device configuration, the band-edge excitation at high-energy band edge improves the lasing performance not only for the same handedness circularly polarized pump beam as the cholesteric helix but also for the opposite one. It stems from the polarization independence of the dielectric multilayers.