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理论上分析了掺MgO的周期极化LiNbO_3(PPMgLN)晶体准相位匹配光参量振荡(QPM-OPO)波长的调谐特性,计算了抽运阈值和转换效率。采用高斯光束抽运,当抽运功率密度为阈值抽运功率密度约6.5倍时,可以获得约71%的转换效率。而相位匹配情况下,平面波抽运功率密度为阈值(π/2)~2倍时,转换效率可达到100%。1064 nm激光抽运PPMgLN晶体(MgO摩尔分数5%),单谐振光参量振荡技术采用e→e+e相位匹配,利用PPMgLN晶体的最大非线性系数d_(33)(27.4 pm/V),采用周期调谐方式,实验上获得了中红外波长调谐范围2.7～4.8μm,当抽运功率为23 W,频率为7 kHz时,在波长3.7μm处激光输出功率超过3.2 W,斜率效率超过18%,对应闲频光波长1.49μm输出功率约8 W,相当于转换斜率效率约为63%。实验结果与理论分析基本一致。
The tuning characteristics of quasi-phase-matched optical parametric oscillation (QPM-OPO) with MgO doped periodically poled LiNbO_3 (PPMgLN) crystal were theoretically analyzed. The pumping threshold and the conversion efficiency were calculated. With Gaussian beam pumping, a conversion efficiency of about 71% can be obtained when the pumping power density is about 6.5 times the threshold pumping power density. In the case of phase matching, the conversion efficiency can reach 100% when the pumping power density of planar wave is threshold (π / 2) ~ 2 times. The PPMgLN crystal was pumped by 1064 nm laser (5% MgO mole fraction). The single-resonant optical parametric oscillation technique used e → e + e phase matching. The maximum non-linear coefficient d33 (27.4 pm / In the experiment, the tuning range of mid infrared wavelength is 2.7 ~ 4.8μm. When the pumping power is 23 W and the frequency is 7 kHz, the laser output power exceeds 3.2 W at a wavelength of 3.7 μm and the slope efficiency exceeds 18% Corresponding idler light wavelength 1.49μm output power of about 8 W, equivalent to the conversion slope efficiency of about 63%. Experimental results and theoretical analysis are basically the same.