Ultraviolet lasing of ZnO whiskers prepared by catalyst-free thermal evaporation

ZnO whiskers were synthesized by vapor transportation via thermal evaporation of ZnO powders in open air. Preferred aligned hexagonal ZnO whiskers with length of 30–40 μm were obtained. Room temperature photoluminescence spectrum of the whiskers exhibits intense ultraviolet excitonic emission and weak defect related visible emission. Optical pumped lasing actions have been observed at 393 nm at room temperature when the excitation intensity exceeds 150 kW/cm2. Laser cavities are formed in the whiskers between the smooth interfaces of the two ends, which acted as reflectors.