采用硼酸锂(LBO)晶体腔外和频Nd∶YAG 1 064 nm与1319 nm激光获得了高功率准连续微秒脉冲钠导星激光。通过改进的欧拉方法数值模拟了和频过程的三波耦合方程, 优化了基频光的束腰大小与LBO晶体长度。为了提高和频效率, 通过像传递系统对两路基频光进行扩束整形实现了空间模式匹配, 通过精确控制触发延时实现了时域激光脉冲同步。研究了500, 600, 800及1000 Hz条件下的和频输出特性, 结果显示, 该条件下分别产生了53, 42.6, 27及22 W的589 nm激光输出, 相应的和频效率分别为21.8%, 20.3%, 16.9%和16.3%。 黄光最高功率时的光束质量因子M2为1.32, 脉冲宽度为100 μs。采用了PZT与步进电机复合控制系统进行稳频, 实现频率的波动为±0.2 GHz, 保证了黄光波长在钠原子D2a谱线的吸收谱内。该项研究为获取50 W级高功率准连续微秒脉冲钠导星激光提供了有效的技术支持。

A high-power quasi-continuous microsecond pulse sodium guide laser was generated by extra-cavity sum frequency of Nd: YAG 1064 and 1319 nm spectral line lasers in a Lithium Borate (LBO) crystal. The three wave coupling equations of the sum-frequency process were simulated by the improved Euler method, and the waist size of fundamental light and the length of LBO crystal were optimized. To improve the sum frequency efficiency, the spatial mode matching and time domain pulse synchronization of two fundamental lasers were realized by the beam shaping of image propagation and the precise control of trigger delay. The laser outputs were researched ,and the results show that the 589 nm laser outputs with the powers of 53, 42.6, 27 and 22 W are obtained under the conditions of 500, 600, 800 and 1000 Hz, and the corresponding sum-frequency efficiencies are 21.8%, 20.3%, 16.9 % and 16.3%, respectively. Moreover, the beam quality factor of M2 is 1.32 and the pulse width is 100 μs at the maximum power of yellow light. A control system compound by a PZT and a stepper motor was used to stabilize the frequency, and results indicate that the frequency fluctuation is in the range of ±0.2 GHz, which ensures that the wavelength of yellow light is within the D2a absorption spectrum of sodium atom. The research results iprovide a technologic support for generating 50 W high-power quasi-continuous microsecond pulse sodium guide lasers.