A random laser made of nematic liquid crystal doped with a laser dye

• Laser dye doped nematic liquid crystal mixtures were measured using the VSL method.
• The gain and losses coefficients for stimulated emission were estimated.
• An increase of ASE was observed above the Fredericks threshold voltage.
• The metalized SRG was used to assist the directional and coherent random laser emission.

We report on random laser emission obtained in 5CB and E7 nematic liquid crystal (LC) mixtures doped with 1% weight to weight ratio of DCM laser dye. The LC cell was used as asymmetric planar waveguide were emission was collected from the edge of the sample. Variable stripe length method was utilized to estimate the gain and the losses coefficients. Both systems have shown the threshold energy fluence in order of several mJ/cm2. In both cases above Fredericks potential, significant increase of emission intensity was observed due to the increase of light scattering on liquid crystalline domains. Moreover the use of fifth order of diffraction grating covered with thin alumina film resulted in strong multimode and directional laser emission.