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在超短飞秒激光技术中,基于Ba F2晶体三阶非线性效应的交叉偏振波技术是目前最重要的提高脉冲时域对比度的手段之一.针对不同入射脉冲强度下入射脉冲的线性啁啾对Ba F2晶体交叉偏振波的输出特性,包括转换效率、光谱加宽和时域压缩的影响进行了详细的数值模拟和讨论.特别地,详细对比研究了非饱和及强入射脉冲情况下线性啁啾对交叉偏振波输出脉冲光谱加宽的影响.结果表明,在强入射脉冲情况下,交叉偏振波的光谱加宽量从非饱和情况下相对于零点线性啁啾时的对称结构,变得不再具有对称性,并对产生非对称性的原因进行了详细的物理解释.
In the ultra-short femtosecond laser technology, the cross-polarization technique based on the third-order nonlinearity of Ba F2 crystal is one of the most important ways to improve the contrast of the time domain of the pulse at present.Aiming at the linear chirp of the incident pulse under different incident pulse intensities, The output characteristics of cross-polarization of Ba F2 crystal, including conversion efficiency, spectral broadening and time-domain compression, are numerically simulated and discussed in detail. In particular, the linear chirp of non-saturated and strong impinging pulses Chirp on the broadening of the output pulse spectrum of the cross-polarized wave.The results show that the spectral broadening of the cross-polarized wave in the case of strong incident pulses becomes from the symmetrical structure in the non-saturated case relative to the zero linear chirp, And then have symmetry, and gave a detailed physical explanation of the causes of asymmetry.