绿光输出达85W的全固态绿光激光器谐振腔研究

Study on Resonator of 85 W All-Solid-State Green Laser

报道了对平均功率达 85W的高功率、高稳定性全固态绿光激光器谐振腔特性的研究 ,将高平均功率运转条件下的KTP倍频晶体的热透镜效应等效为一个薄透镜 ,利用ABCD传输矩阵 ,通过图解方法定性地讨论了KTP晶体的热透镜效应对谐振腔的稳定性和腔内激光模式的巨大影响 ,理论分析表明适当大小的倍频晶体热透镜焦距不但可以有效地补偿Nd∶YAG棒的热透镜效应 ,而且对增大激光介质中的模体积和在倍频晶体处提高功率密度都有积极作用。实验中采用了 80个 2 0W的高功率半导体激光器侧面抽运的单Nd∶YAG棒、两个声光Q开关、高效平 凹谐振腔结构、对大尺寸KTP晶体进行角度偏离法补偿相位失配等技术 ,并通过对KTP晶体采取适当的冷却方式 ,最终实现了高功率内腔倍频激光器的高稳定性运转 ;在抽运功率约为 10 80W时 ,实现了重复频率为 2 0 4kHz ,脉冲宽度 2 30ns ,输出功率达 85W的高功率、高重复频率绿光 (5 32nm)输出 ,不稳定性仅为± 1 0 3%。

In this paper, research on the resonator of a high-average-power high stabilization 85 W all-solid-state green laser was reported. The thermal effects of the KTP crystal operating at high-average-power condition were treated as a thin lens, and the effects of this thin lens on the stability and laser modes of the resonator were graphically discussed by ABCD matrix method. Theoretical analyses indicated that an optimum focal length of this thin lens would do a great deal of good to compensate thermal lens effect of Nd∶YAG rod, enlarge TEM 00 mode volume and enhance the laser power density at KTP crystal. In the experiment, 20 W×80 high power laser diode arrays and double acousto-optic Q-switching were employed inside single Nd∶YAG rod, and a flat-concave intracavity-frequency-doubled resonance structure was used. A maximum green power of 85 W was generated at 20 4 kHz repetition rate and 230 ns pulse width when pumped power was about 1080 W with compensating phase mismatch by angle departuring and properly cooling big KTP crystal, leading to ±1 03% instability.