Low threshold and coherent random lasing from dye-doped cholesteric liquid crystals using oriented cells

We demonstrate the realization of a coherent random laser in a strongly scattering medium, which contained a dispersive solution of Ag nanoparticles and laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) in cholesteric liquid crystals that was injected into an oriented cell. Multiple scattering of Ag nanoparticles and helical domains greatly enhanced by the oriented cell confinement effect was experimentally verified to account for the coherent lasing observed in our oriented system. Based on non-oriented cells and oriented cells, this paper extends the active and scattering media-based random lasers from the incoherent regime to the coherent regime.