A study of measurement method of optical vortex in the far field region using Shack-Hartmann wavefront sensor

摘要

Measurement of optical vortices (OVs) is important to many advanced applications of OV beams. An OV beam usually has annular intensity distribution, thus, the measurement of OV suffers problems such as less measurement points and extremely non-uniformity in the intensity distribution. In this paper, we propose a new method to solve those problems and precisely characterize OVs. Our approach is to find a circle extracted from the annulus that contains significant part of information and can best express the annulus pattern. Then just with the measurement data on the circle we determine the position and topological charge (TC) of OV beam. The experimental results show our new method possesses high precision even within large TC range, from -20 to 20. For position measurement, the maximum root mean square error is lower than 0.2 in unit of lenslet size, while for TC measurement, the measured TCs are nearly all identical with theoretical TCs after being rounded.