Two-photon pumped random laser in nanocrystalline ZnO

Thin film of ZnO nanoparticles with dimension of about 5-10 nm were fabricated by the pulsed laser ablation method. By using a femtosecond laser beam at 700 nm to pump micrometer-thick films the authors observed two-photon-induced lasing at 385 nm. Experimentally obtained dependence of the threshold on the excitation spot radius r(0) is closer to (1/r(0)(2)) than to (1/r(0)), thus suggesting efficiency of the feedback by scattering-random lasing. The experimental data on nonlinear transmission of the film at the wavelength of pumping are presented. (c) 2006 American Institute of Physics.