基于气相传输法制备具有六方对称截面棒状的氧化锌样品,在应用扫描电子显微镜和X-射线衍射仪进行结构表征后,室温下以中心波长为355 nm的纳秒脉冲激光激发,研究激励光强变化对其紫外受激辐射特性影响。实验中发现,当激励光功率密度提高至225 kW/cm2左右时，在宽谱自发辐射背景中初步观测到中心波长为393 nm的低阈值、高Q值的受激辐射；此时，进一步提高激励光功率密度,辐射光强会迅速提高,辐射模式与波长基本稳定；继续提高激励光强至450 kW/cm2左右时，受激辐射光强随激励光强的增加呈饱和现象，辐射模式数相对稳定但各模式中心呈现波长连续红移。理论分析表明,所观测的受激辐射具有典型回音壁模谐振模特征,辐射模式和光强随激励条件变化，与样品中激子激子非弹性碰撞散射后的复合发光机制有关；高功率密度激励条件下辐射强度饱和、各模式中心波长的连续红移,与样品Mott相变后的库仑屏蔽效应、能级重整以及自由载流子的无辐射复合有关。

ZnO microrods samples with hexagonal cross-section are prepared by the vapor phase transport method, and examined by scanning electron microscope and X-ray diffraction diffractometer. Excited by 355 nm laser pulse with different excitation power densities, the stimulated emission characteristics from the mentioned samples are experimentally investigated. The fascinating two-stage behaviors of stimulated emission are observed. In the first stage, with excitation power intensity around 225 kW/cm2, samples begin to exhibit typically stimulated emission, which peaking at 393 nm and appearing red-shift compared with spontaneous emission, with a low lasing threshold and high quality factor. The discrete lasing modes and corresponding wavelength keep invariable while emission intensity increases dramatically dependence on the increase of excitation power density. As the excitation power density increases to a second threshold about 450 kW/cm2, the stimulated emission displays saturation in intensity and continuous red-shift in wavelength. Theoretically analysis show that this performance can attribute to the whispering gallery mode lasing, exciton-exciton collision, Mott transition, energy level renormalization and compound without emission effect, respectively.