Band-edge-enhanced tunable random laser using a polymer-stabilised cholesteric liquid crystal

Electrically tunable random laser action has been demonstrated in a cavity-free structure. The scattering structure was shaped by the treatment of AC, and a polymer network structure is introduced to fix it. The fluorescence of the laser dye is scattered internally and selectively amplified at the band-edge of the photonic crystal, due to the concentrate of the photonic density of state. As the electric field increased, the deformation of the polymer network causes the cholesteric liquid crystal pitch to form a gradient distribution, resulting in the widening of the bandgap, and the random laser wavelength changes accordingly. This random laser with a broad tuning range (∼100 nm) opens new possibilities for the design of highly efficient incoherent light source in a large area with a thickness of micron level.