频率啁啾对飞秒激光脉冲干涉场的影响

Influence of frequency chirp on interference field of femtosecond laser pulses

对具有频率啁啾的飞秒脉冲的干涉场分布特性进行了研究。分别模拟了物光存在啁啾、参考光存在啁啾以及物光与参考光均存在啁啾3种情况下高斯飞秒脉冲的干涉图,并从干涉图中提取了载频相位。通过对提取的载频相位分析,研究了频率啁啾对干涉场的影响。结果表明,脉冲的频率啁啾将导致干涉条纹对比度的下降和条纹周期的改变。当物光和参考光仅有一束存在啁啾时,干涉场条纹的对比度整体下降,并且条纹周期发生线性改变;当物光与参考光同时具有相同的频率啁啾时,位于干涉场边缘的条纹的衬比度会严重下降,这将导致干涉场的有效记录区域减小。本文研究对于飞秒数字全息的实验控制和数字重构精度均具有重要的参考价值。

The interference fringe pattern of Gaussian distributed femtosecond laser pulses with fre- quency chirping is studied in this paper. Holograms in three cases of only object pulse with frequency chirping, reference pulse with frequency chirping and the two pulses with the same frequency chirping to- gether are simulated respectively and the carrier phases are reconstructed from the holograms. By analy- zing the spatial distribution characteristics of the reconstructed carrier frequency, the influence of the fre- quency chirping on the interference fringe pattern is studied. The computer simulation results show that the frequency chirping of pulses will result in the decrease of the contrast of the interference fringe and the change of the period of the interference fringe. When only object beam or reference beam has the fre- quency chirping,the contrast of the whole hologram will decrease and the fringe period will change line- arly^when both object beam and reference beam have the same frequency chirping, the contrast of fringe area of the interference field will decrease seriously, which will result in the sharp decrease of effective recorded area of the interference field. The research is very important for the experiment performance of femtosecond laser pulses digital holography or interference and the precision of digital reconstruction in phase measurement.