Pu Haosen, Shu Jianhua, Chen Ziyang, Lin Zhili, Pu Jixiong
J Opt Soc Am A Opt Image Sci Vis. 2015 Sep 1;32(9):1717-22. doi: 10.1364/JOSAA.32.001717.
Based on the Richards-Wolf vector diffraction theory, we have derived the expressions for the electric field and the propagation velocity of femtosecond radially polarized light pulses focused by a high numerical aperture (NA) objective. The intensity distribution in the focus, wavefront spacings, and propagation velocity variation near the focus are investigated in detail by using numerical calculations. It is found that the propagation velocity of focused ultrashort light pulses changes dramatically near the focus, and the propagation velocity of the focused laser pulse is strongly dependent on the NA of an objective and the refractive index of media. Moreover, the usual propagation velocity of light pulses, as expected, decreases as the refractive index of media increases.
基于理查兹-沃尔夫矢量衍射理论，我们推导了高数值孔径（NA）物镜聚焦的飞秒径向偏振光脉冲的电场和传播速度表达式。通过数值计算详细研究了焦点处的强度分布、波前间距以及焦点附近的传播速度变化。研究发现，聚焦超短光脉冲的传播速度在焦点附近会发生显著变化，且聚焦激光脉冲的传播速度强烈依赖于物镜的数值孔径和介质的折射率。此外，正如预期的那样，光脉冲的通常传播速度会随着介质折射率的增加而降低。
