Sol-gel ZnO-SiO₂composite waveguide ultraviolet lasers

Random laser action with coherent feedback is realized in ZnO-SiO2composite films, which consists of ZnO clusters embedded in SiO2dielectric matrix prepared by sol-gel technique. The films are deposited on silicon substrate with a SiO2buffer layer to form a waveguide structure. Ultraviolet lasing at room temperature is observed from the composite films with ZnO : SiO2molar ratio varying between 1 : 5 and 1 : 30. The corresponding lasing wavelength and linewidth under 355-nm optical excitation are found to be ∼388 nm and less than 0.6 nm, respectively. Our experiment has shown that the proper control of light confinement inside the random cavities leads to coherent random lasing.