Random lasing action from ZnO–silica nanohybrids

Abstract

Optically active zinc oxide–silica, inorganic–inorganic nanohybrid materials have beensynthesized via a sol–gel process utilizing a room temperature scheme that does not requirehigh temperature annealing. Random laser action is demonstrated from theseZnO–silica nanocomposites. The ZnO nanoparticles act as both the gain andthe strong scattering medium, which leads to random optical feedback due tomultiple elastic scattering, while the amorphous silica matrix offers a high degree ofmaterial stability. Optical pumping of the nanocomposites by ultraviolet laserpulses, of duration shorter than the ZnO photoluminescence lifetime, leads to aprofound optical gain behavior and random laser action above a certain thresholdvalue of the excitation energy density. In this context, the effects of laser andmaterial parameters on the observed random lasing are investigated for a series ofnanocomposites. The observed dependence of the emission wavelength on excitationenergy and the excitation energy density value of the random laser threshold areinterpreted on the basis of the formation and the inversion of an electron–hole plasma,respectively.