研制了一种基于铌酸锂(LN)电光调Q的高重复频率窄脉宽短腔激光器.通过测量激光穿过置于正交偏振镜间的电光晶体后, 透射强度随晶体上施加的脉冲高压的变化情况, 探究了不同尺寸LN晶体中的压电振铃效应, 并与磷酸钛氧铷(RTP)晶体中的压电振铃效应进行了比较.实验发现, 块状LN晶体中的压电振铃效应严重, 而小尺寸LN晶体中的压电振铃效应和RTP晶体中的相似, 基本可以忽略.结合压电效应理论得出, 压电振铃效应的强弱与外加电压大小及晶体固有的压电共振频率有关, 电压越低, 压电共振频率越大, 压电振铃效应越弱.在此基础上, 制备了可高重频应用的尺寸为1.2 mm×9 mm×9.4 mm的LN调Q开关, 并实现了LN晶体的高重频调Q运转.激光增益介质采用具有较大受激发射截面和较短荧光寿命的Nd∶YVO4晶体, 其一端镀有1.064 μm的全反膜, 另一端沿布儒斯特角切割, 从而省去了全反镜和偏振镜, 缩短了腔长。泵浦源采用中心波长为808 nm的光纤耦合激光二极管.设计的激光器谐振腔长度仅为20 mm。在退压式电光调Q运转下, 获得了最大重复频率为15 kHz、脉宽为5.4 ns、峰值功率为2.94 kW的稳定的激光输出.

With a LiNbO3 crystal as the electro-optic Q-switch, a compact Q-switched laser with a high repetition rate and a narrow pulse width was developed. The crystal was sandwiched between two crossed polarizers, then the variation of the laser transmitted intensity with the pulsed high voltage applied to the crystal was measured to investigate the piezoelectric ringing effects in LiNbO3 crystals with different dimensions. Additionally, the piezoelectric ringing effects in LiNbO3 crystals were compared with that of a RbTiOPO4 crystal. The results show that the block LiNbO3 crystal suffers enormously from piezoelectric ringing, while the piezoelectric ringing in the miniaturized LiNbO3 crystal is similar to that of the RbTiOPO4 crystal and is negligible. Combining with the piezoelectric effect theory, it is derived that the acoustic ringing is influenced by the applied voltage and the piezoelectric resonance frequency, the acoustic ringing decreases with the decreasing of applied voltage and the increasing of piezoelectric resonance frequency. Based on these results, a miniaturized LN electro-optic Q-switch that can operate at a high repetition rate was prepared, its dimensions is 1.2 mm×9 mm×9.4 mm. The miniature LN crystal was successfully used for high repetition rate electro-optic Q-switching. A Nd∶YVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime was used as the gain medium. One side of the Nd∶YVO4 crystal was high-reflection coated at 1 064 nm, and another side was cut along the Brewster angle, then a reflecting mirror and a polarizer was saved and the cavity length was shortened. The pump source was a fiber-coupled laser diode with a central wavelength of 808 nm. Based on the above design, a compact cavity with a length of only 20 mm was achieved. In the pulse-off Q-switching operation, a stable pulsed laser operating at a maximum repetition rate of 15 kHz with a pulse width of 5.4 ns and a peak power of 2.94 kW was obtained.