为了实现光参变放大抽运光源高稳定输出的目的。通过对倍频过程的数值模拟分析,提出倍频中存在“稳定区”的概念,在基频光强一定的条件下(小于倍频晶体破坏阈值),通过非共线双程倍频的方式或串联倍频的方式可有效延长倍频晶体的有效作用长度,保证倍频工作区能够被控制在“稳定区”内,从而实现高稳定高转换效率的倍频输出。实验数据验证了这一结论,实验中,利用非共线双程倍频的方式使得倍频工作区在“稳定区”内,对波动±5.7%的1064 nm高斯脉冲基频光, 倍频光波动小于±2%,脉冲形状为高阶高斯脉冲,转换效率大于70％,实验结果表明,倍频光的稳定性指标相对于基频光提高了近3倍。

To improve the stability of pumping source of optical parametric amplifier, the concept of stable area in the frequency-doubling is proposed, with the numerical simulation of the frequency doubling process. Under certain intensity of the fundamental light, less than the breakdown threshold of the frequency-doubling crystal, the valid length of the frequency-doubling crystal is prolonged with the nonlinear two-pass frequency-doubling or the tandem frequency-doubling, with which the frequency-doubling course is located in the stable area and the highly stable second harmonic output with high conversion efficiency is realized. The experiments prove the above conclusion, and in the experiment the nonlinear two-pass frequency-doubling method is used to ensure the work area of the frequency-doubling in the stable area. The fluctuation of the second harmonic is less than ±2% for the 1064 nm fundamental Gaussian pulse with flutuation ±5.7%, and the conversion efficiency exceeds 70% for high-order Gaussian pulses. The experimental results show that the stability of the second harmonic is near 3 times higher than that of the fundamental light.