啁啾体布拉格光栅的脉冲响应特性

Impulse Response Characteristics of Chirped Volume Bragg Gratings

基于矩阵法,构建超短脉冲经啁啾体布拉格光栅(CVBG)衍射的频域和时域响应分析模型。针对百飞秒(fs)级光纤啁啾脉冲放大(FCPA)系统对于CVBG的带宽要求,系统研究衍射带宽对CVBG的脉冲展宽及压缩效应的影响及宽带CVBG对于不同啁啾参数输入脉冲的脉冲响应特性。研究结果表明:CVBG的衍射带宽随其啁啾率和厚度增大而线性增大;当CVBG的衍射带宽小于入射脉冲的频谱宽度时,频谱成分的剪切会导致展宽脉冲的变形并使压缩脉冲相对于入射脉冲而展宽;为实现100 fs脉冲的展宽-压缩对易性,须保证CVBG衍射带宽不小于60 nm。设计中对单块厚度为40 mm的宽带CVBG先展宽再压缩,得到频谱宽度为16.64 nm的线性啁啾脉冲,输出脉冲均无限接近傅里叶变换受限(FTL)脉冲且衍射效率高达84%,这为百fs级CVBG脉冲压缩器的实现提供了理论参考及指导。

In this work, the frequency domain and time domain response analysis model of ultrashort pulses via chirped volume Bragg grating(CVBG) is constructed based on the matrix method. Aiming at the bandwidth requirement of CVBG for the hundred-femtosecond(fs) fiber chirped pulse amplification(FCPA) system, we systematically study the influence of the diffraction bandwidth on the pulse stretching and compression effect of CVBG and the impulse response characteristics of the broadband CVBG to incident pulse with different chirp parameters. The results show that the diffraction bandwidth of CVBG increases linearly with the increasing chirp rate and thickness. When the diffraction bandwidth of CVBG is smaller than that of the incident pulse, the shearing of the spectral components will cause distortion of the stretched pulse and broadening of the compressed pulse with respect to the incident pulse. To achieve stretching-compression reciprocity of the one-hundred-femtosecond pulse, it is necessary to ensure the diffraction bandwidth of CVBG no less than 60 nm. As designed, a broadband CVBG with 40 mm thickness is stretched first and then compressed, and linear chirp pulses with a spectral width of 16.64 nm are obtained. All of the output pulses are infinitely close to the Fourier transform constrained(FTL) pulse and the diffraction efficiency is as high as 84%, which provides a theoretical reference for the implementation of the fs CVBG pulse compressor.