Investigations of the spontaneous and stimulated emission spectra by optical pumping of ZnO layers deposited on silicon oxide were carried out. The stimulated emission pumped under ultraviolet 337 nm N-2 laser excitation was observed at 397 nm at room temperature from ZnO-SiO2-Si type thin film structures. The threshold pumped power for the electron-hole plasma recombination laser process is of the order of 35 MW/cm(2). (C) 2003 Elsevier B.V. All rights reserved.