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Updated: Jun 11, 2026

Femtosecond Laser Filaments for Use in Sub-Diffraction-Limited Imaging and Remote Sensing
Published on: April 25, 2019
Focusing of a femtosecond vortex light pulse through a high numerical aperture objective
Baosuan Chen1, Jixiong Pu, Olga Korotkova
1College of Information Science and Engineering, Huaqiao University, Quanzhou, Fujian 362021, China.
Abstract:
We investigate the focusing properties of a femtosecond vortex light pulse focused by a high numerical aperture objective. By using the Richards-Wolf vectorial diffraction method, the intensity distribution, the velocity variation and the orbital angular momentum near the focus are studied in great detail. We have discovered that the femtosecond vortex light pulse can travel at various speeds, that is, slower or faster than light with a tight focusing system. Moreover, we have found that the numerical aperture of the focusing objective and the duration of the vortex light pulse will influence the orbital angular momentum distribution in the focused field.
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