抑制Nd:YAG激光器自锁模的实验研究

用于抽运钛宝石的电光调Q Nd:YAG激光器会出现自锁模调制,导致峰值功率不稳从而损伤钛宝石晶体,为了抑制这种自锁模调制,分析了产生该现象的原因,研究了谐振腔内插入法布里-珀罗(F-P)标准具的技术方案。实验采用单个厚度20mm,膜层反射率60%的标准具,有效抑制了该Nd:YAG激光器的自锁模调制,实现了脉宽约70ns,脉冲能量约600mJ的1064nm激光的稳定输出,既避免了引入较大的插入损耗,又防止了对F-P标准具膜层的损伤。分析认为单个厚度合适、膜层反射率不太高的标准具可有效抑制Nd:YAG激光器自锁模现象的原因在于:标准具一个透射峰半峰全宽(FWHM)内理论上虽有约5个纵模,但偏离透射峰中心的纵模损耗较大,使得单个透射峰内实际起振的纵模可能只有1个;激光器的增益线宽内虽存在标准具的多个透射峰,但起振纵模因不相邻避免了形成相位锁定。

Experimental Study on Eliminating Self-Mode Locking of Nd:YAG Laser

The phenomena of self-mode locking in Q-switched Nd:YAG laser used for pumping Tisapphire will result in instability of laser pulse peak power output and mangle the optical devices. In order to eliminate this phenomena availably, the reason caused for self-mode locking is investigated, and Fabry-Perot (F-P) etalon with different parameters is employed. By using one piece of 20 mm-thick F-P etalon with a reflectivity of 60%, which can not only reduce inserting loss but also avoid the damage of F-P etalon′s coatings, a smooth pulse waveform in pulse width of 70 ns and pulse energy of 600 mJ at 1064 nm is realized, the reason for it may be as follows: though there are probably five longitudinal modes in a full width at half maximum (FWHM) of F-P etalon theoretically, only one longitudinal mode may be able to oscillate considering the loss; though there are several transmission peaks in the gain bandwidth of Nd:YAG, incontiguous longitudinal modes can not meet the condition of mode locking.