Random lasing action from ZnO-silica nanohybrids

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