基于多台阶反射光栅的飞秒脉冲压缩装置

反射式光栅对是一种具有负色散性质的器件,可用于飞秒激光脉冲的压缩和展宽,具有无材料色散的优点。给出了一种基于多台阶反射光栅的脉冲压缩装置。该装置为倍密度光栅结构,由两个周期分别为40μm和20μm的四台阶反射式光栅组成。实验得到的衍射效率可以达到70%以上,输入脉冲经过两个光栅的衍射后会按原路返回,从而达到色散补偿的效果。利用此压缩装置,脉冲宽度为66.8 fs的输入脉冲压缩至接近傅里叶变换极限脉冲,即46.6 fs,由此证明只要多台阶光栅效率足够高,此装置就有可能成为不同于棱镜对进行飞秒脉冲腔内和腔外压缩的另一种途径。

Femtosecond Laser Pulse Compressor Based on Multi-Level Reflection Gratings

Reflection grating pairs are usually used for femtosecond pulse compressing and stretching because of its advantage of negative dispersion. In this paper, a multi-level reflection grating based pulse compressor was presented, which is also called double-line-density gratings structure. It contains two four-step reflection gratings with periods of 40 μm and 20 μm, respectively, and the compressor has the efficiency of more than 70%. The input femtosecond pulses will go back along the input direction after diffractions of the two gratings, and in this way, the positive group velocity dispersion (GVD) of the input pulses is compensated. Using this compressor, the input pulses 66.8 fs are compressed into Fourier-transform-limited ones with the bandwidth of 46.6 fs. So it is demonstrated that, with high efficiency, low density reflective grating pair is an alternative approach different from prism pair as a compressor for both inside and outside femtosecond laser cavities.