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从超短脉冲光束的傍轴传输方程出发,得出了描述任意脉冲形式驱动的等衍射超短脉冲厄米高斯光束在自由空间中的解析表达式.并通过例子研究了超短脉冲厄米高斯光束的传输性质.结果表明:在传输过程中,由于群速度的空间分布不均匀性,会导致超短脉冲光束的脉冲时间延迟,并进而导致了在脉冲不同位置处光束横向分布严重偏离了厄米高斯函数.另外,在传输过程中,发现不同阶数的脉冲厄米高斯光束会发生不同次数的极化反转.并用脉冲光束的群-相速度差对这一现象进行了解释.
Starting from the paraxial transmission equation of an ultrashort pulsed beam, an analytical expression describing the free-space diffraction of an equi-diffracted ultrashort pulsed Hermite-Gaussian beam in arbitrary pulse form is obtained. The ultrashort pulsed Hermite-Gaussian The results show that due to the spatial heterogeneity of the group velocity, the pulse time delay of the ultrashort pulse beam can be delayed in the transmission process, which leads to the serious lateral distribution of the beam at different positions of the pulse. In addition, during the transmission, different orders of pulsed Hermite beams were found to undergo different degrees of polarization reversal, and this phenomenon was explained by the group-phase velocity difference of pulsed beams.