High accuracy Gouy rotation measurement for the composition vortex beams using imaging technology

The rotation characteristics of the composition Laguerre–Gaussian (LG) beams during the propagation are numerically analyzed. A simple rotation angle measure method based on imaging technology is proposed and demonstrated. First, the global feature points of the composite vortex pattern is extracted by the 8-connected boundary tracking algorithm. Then, the position coordinates of each feature point are calculated by using the weighting method. The rotation angle of each feature point relative to the center point is calculated under the coordinate system. Finally, the relative rotation angles of the composite vortex pattern at different positions relative to the original position are obtained. The results show that the measurement error reaches 10[Formula: see text] for composite beams with different sizes and beam waist, which is comparable to that of the theoretical value. The proposed method can be used to effectively and accurately measure the Gouy phase of the composite LG beams. We expect the proposed method will be benefit of the further research and application of Gouy phase.