Lasing in cholesteric liquid crystal cells: Competition of Bragg and leaky modes

Measurements of the angular dependency of luminescence and lasing spectra were carried out for a planar layer of a dye-doped cholesteric liquid crystal (CLC). In addition to the known Bragg emission mode propagating along the cell normal, we observed that leaky modes also depend on the pump intensity and on the dimension and shape of the transverse cross section of the excitation beam. The leaky modes are valuable as a specific lasing regime but impose serious limitation on the energy of the Bragg lasing modes. This has to be taken into consideration when designing high energy lasing devices based on CLC.