An Analysis of Temporal Diffraction of a Chirped Femtosecond Laser Pulse by a Circle Aperture

An equation is put forward to calculate the temporal diffraction intensity distribution of a chirped femtosecond laser pulse when it incites a circle aperture. In the aperture central direction an analytic expression is given to calculate the temporal intensity distribution. Many factors such as the width of the laser pulse, the radius of the circle aperture, the Fresnel number at central frequency, time and the chirped coefficient of the laser pulse affect the temporal intensity. Number calculation shows that if the width of laser pulse is within a few tens of femtoseconds and Fresnel number at central frequency is much than twenty, the temporal diffraction intensity outline is not a Gaussian curve. While when the Fresnel number is less than ten and the chirped coefficient is small, the temporal intensity is an approximate Gaussian curve. If the chirped coefficient is large, the temporal intensity is not Gaussian distribution.