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针对纳秒量级调Q宽频带光纤激光器,分别模拟了利用光栅角色散补偿(ASD),棱镜ASD以及晶体级联方法对倍频效率的影响。采用LBO晶体Ⅰ类相位匹配,通过数值求解高斯光束三波耦合方程,得到了入射基频光线宽、聚焦光斑位置、聚焦光斑大小以及晶体长度对倍频转换效率的影响,并对晶体参数进行优化。计算结果显示:直接倍频时,对于5 nm宽频带激光,倍频效率只有17%;采用光栅角色散补偿可以在大光谱范围内倍频效率达到70%以上;棱镜提供的补偿较小,但也能使倍频效率提高50%;三块晶体级联可以使倍频效率提高130%。
Aiming at the nanosecond Q-switched broadband fiber laser, the effect of multiplicative efficiency on the frequency doubling efficiency is simulated respectively using the ASD, the prism ASD and the crystal cascade method. By using LBO crystal type Ⅰ phase matching, the effects of wide incident fundamental frequency, focused spot position, focal spot size and crystal length on multiplier conversion efficiency were obtained by numerical solution of the three-wave coupling equation of Gaussian beam. The crystal parameters were optimized. The calculation results show that the frequency multiplication efficiency is only 17% for the 5 nm wide-band laser when the direct frequency doubling is used, and the frequency doubling efficiency can be achieved over 70% in the large spectral range by using grating angular dispersion compensation. The prism provides smaller compensation, Can also make frequency doubling efficiency increased by 50%; three crystal cascade can make the frequency doubling efficiency increased by 130%.