周期极化LiNbO_3脉冲走离效应分析

Numerical analyses on walk-off effect in periodically poled lithium niobate

建立了包含高阶群速色散的OPCPA数值模拟程序,并以准相位匹配的周期极化的LiNbO3(PPLN)参量放大器为例,在信号光是中心波长1 053 nm,脉宽100 fs的飞秒脉冲经展宽器展宽800 ps的啁啾脉冲,输入能量约0.6 nJ,泵浦光波长527 nm,脉宽3 ns,初始输入泵浦光强300 MW/cm2,PPLN晶体的非共线角1.49°,极化周期9.7μm的条件下,对OPCPA过程前级的高阶群速色散引起的走离效应对泵浦光、信号光频谱和脉冲形状的影响等具体特性进行了数值模拟。结果表明:在合适的晶体长度下,高阶群速色散对参量转换效率的影响不大,但它对输出信号光的时间波形和频谱有较大影响,会引起脉冲时间形状畸变和频谱漂移。

This paper presents our numerical analyses on the walk-off effect in periodically poled lithium niobate（PPLN） for optical parametric chirped pulse amplification in the front-stage of PW laser system with our simulation program. Under the 527 nm, 3 ns and 300 MW/cm2 pumping condition, using 1 053 nm, 0. 6 nJ stretched pulse（from 100 fs to 800 ps） as signal, our analyses show that the high-order group velocity in the parametric process has little effect on the conversion coefficiency, but it distorts both the temporal and spectral profiles of the output signal pulse, thus degrades the pulse contrast of the amplified signal through a PPLN with a poled period of 9.7 μm.