Reversible tuning of lasing in cholesteric liquid crystals controlled by light-emitting diodes

The lasing wavelength of dye-doped cholesteric liquid-crystal lasers is optically tuned by the reversible photoisomerization of the azo- or azoxynematic components of the cholesteric mixture. The figure demonstrates that the laser can be tuned over a range of almost 70 nm. The nematic components are easily and reversibly isomerized by illumination from light-emitting diodes at 405 and 466 nm.