Topological charges measurement of circular Bessel Gaussian beam with multiple vortex singularities via cross phase.

In this paper, we firstly propose a method to measure the topological charges (TCs) of a circular Bessel Gaussian beam with multiple vortex singularities (CBGBMVS) by utilizing cross phase. Based on theory and experiment, the cross phase is utilized to realize the TCs measurement of the CBGBMVS in free space with different situations, such as different singularity number, TCs and singularity location. Especially, the TCs measurement method is also investigated and verified in atmosphere turbulence. Our work provides an effective and convenient way to realize the TCs measurement of multiple singularities embedded in abruptly autofocusing host beams which has plenty of potential application in optical communication.