分析了现有光谱相位相干直接电场重构法(SPIDER)系统的一个缺点, 即需预先估计待测脉冲的特性, 来设定合适的系统参数。因而其适用范围受到一定限制, 特别是在测量啁啾脉冲时容易出现偏差。实验用SPIDER系统分别测量了钛宝石飞秒激光器输出的脉冲及其经BK7玻璃块展宽得到的啁啾脉冲, 测得啁啾脉冲的宽度为295 fs, 作剪切量修正后测得脉宽为322 fs, 后者更接近理论预期的313 fs。这表明SPIDER系统测量啁啾脉冲时, 如果色散器提供的色散量不够大, 会出现一定程度的偏差。通过补充记录两个和频脉冲的光谱, 修正实际的剪切量, 可有效减小误差, 但问题仍未完全解决。

We focus on a defect that often occurs in spectral phase interferometry for direct electric-field reconstruction(SPIDER) systems: the features of the measured pulse should be predicted properly so as to adjust suitable parameters for the phase retrieval. This defect actually makes some limitations to the applicability of these systems. Errors occur likely when chirped pulses are to be measured. To prove this, we set up a conventional SPIDER system to measure the femtosecond pulses from a Ti:sapphire laser and the chirped pulses resulted from the broadening of a BK7 glass block. The duration of the chirped pulse is 295 fs, while 322 fs is obtained after spectral shear correction. The latter is closer to theorectically predicted value of 313 fs.The experimental results show that errors do occur when the measured pulse has obvious chirp, yet not enough dispersion is offered by the broadening unit of the SPIDER system. However, this error can be decreased by calibrating the spectral shear by means of recording the spectra of the upconverted pulses.