Related Experiment Video
Updated: Jul 15, 2026

Femtosecond Laser Filaments for Use in Sub-Diffraction-Limited Imaging and Remote Sensing
Published on: April 25, 2019
Sharper focal spot formed by higher-order radially polarized laser beams
1Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan. yk-zw@mail.tagen.tohoku.oc.jp
Abstract:
The intensity distributions near the focal point for radially polarized laser beams including higher-order transverse modes are calculated based on vector diffraction theory. For higher-order radially polarized mode beams as well as a fundamental mode (R-TEM01*) beam, the strong longitudinal component forms a sharper spot at the focal point under a high-NA focusing condition. In particular, double-ring-shaped radially polarized mode (R-TEM11*) beams can effectively reduce the focal spot size because of destructive interference between the inner and the outer rings with pi phase shift. Compared with an R-TEM01* beam focusing in a limit of NA=1, the full width at half-maximum values of the focal spot for an R-TEM11* beam are decreased by 13.6% for the longitudinal component and 25.8% for the total intensity.
Related Concept Videos
Confocal Fluorescence Microscopy
Focusing of Light in the Eye
Polar Coordinates: Problem Solving

