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本文在光脉冲近似为双曲正割函数下，运用有限傅里叶变换法（ＦＦＴ）对飞秒脉冲二次谐波自相关测量系统中主要由倍频晶体引起的三阶色散效应进行了数值计算和分析．指出当光脉冲的半高宽（ＦＷＨＭ）接近或小于１０ｆｓ时，脉冲才有明显的展宽效应，脉冲的展宽倍数与晶体的长度成递增关系，脉冲的前沿也出现了弛豫振荡结构的畸变现象，计算同时给出能基本消除三阶色散的展宽效应的倍频晶体的最大厚度，讨论了三阶色散对光脉冲频谱的影响
In this paper, under the optical pulse approximate hyperbolic secant function, the third-order dispersion effect mainly caused by frequency doubling crystal in the measurement system of femtosecond pulse second-harmonic autocorrelation is studied by finite Fourier transform (FFT) Calculate and analyze. It is pointed out that when the full width at half maximum (FWHM) of the light pulse is close to or less than 10fs, the pulse broadens the effect obviously. The broadening ratio of the pulse has an increasing relationship with the length of the crystal, and the leading edge of the pulse also appears the distortion of the relaxation oscillation structure , The maximum thickness of the frequency doubling crystal with the broadening effect that can basically eliminate the third-order dispersion is calculated, and the influence of the third-order dispersion on the optical pulse spectrum is discussed