Sol-gel ZnO-SiO2 composite waveguide ultraviolet lasers

Random laser action with coherent feedback is realized in ZnO-SiO₂ composite films, which consists of ZnO clusters embedded in SiO₂ dielectric matrix prepared by sol-gel technique. The films are deposited on silicon substrate with a SiO₂ buffer layer to form a waveguide structure. Ultraviolet lasing at room temperature is observed from the composite films with ZnO : SiO₂ molar 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.