Electrical Modulation of Random Lasing Emission from ZnO Nanopowder and Liquid Crystal Hybrid Polymer Film

Electrical modulation of random lasing characteristics from hybrid polymer thin films consisting of ZnO nanopowder and liquid crystal (E7) was demonstrated. The emission intensity of incoherent random lasing from the ZnO is enhanced by up to a factor of ∼1.4 by applying an electric field with a voltage amplitude of 40 V to the thin film, while that of the spontaneous emission is not changed. By analyzing pumping power dependence of the photoemission intensity with a rate equation model of a two-level gain system in a cavity, we found that the enhancement of lasing emission is caused by the decrease in random cavity loss due to the electrical application. The reason for suppressing the cavity loss is anisotropic enhancement in the light scattering strength of liquid crystal droplets due to the alignment of liquid crystal to the direction parallel to the applied electric field.