[1] P. Coullet, L. Gil, F. Rocca. Optical vortices. Opt. Commun., 73, 403-408(1989).
[18] J. Wang. Advances in communications using optical vortices. Photon. Res., 4, B14-B28(2016).
[27] J. E. Curtis, D. G. Grier. Structure of optical vortices. Phys. Rev. Lett., 90, 133901(2003).
[43] V. Arrizón, U. Ruiz, R. Carrada, L. A. González. Pixelated phase computer holograms for the accurate encoding of scalar complex fields. J. Opt. Soc. Am. A, 24, 3500(2007).