1. Coullet, P., L. Gil, and F. Rocca, "Optical vortices," Opt. Commun., Vol. 73, 403-408, 1989.
doi:10.1016/0030-4018(89)90180-6
2. Brambilla, M., L. A. Lugiato, V. Penna, F. Prati, C. Tamm, and C. O. Weiss, "Transverse laser patterns. II. Variational principle for pattern selection, spatial multistability, and laser hydrodynamics," Phys. Rev. A, Vol. 43, 5114, 1991.
doi:10.1103/PhysRevA.43.5114
3. Bazhenov, V. Yu., M. V. Vasnetsov, and M. S. Soskin, "Laser beams with screw dislocations in the wavefronts," Pis'ma Zh. Eksp. Teor. Fiz., Vol. 52, 1037-1039, 1990.
4. Bazhenov, V. Yu., M. S. Soskin, and M. V. Vasnetsov, "Screw dislocations in light wavefronts," J. Mod. Optics, Vol. 39, 985-990, 1992.
doi:10.1080/09500349214551011
5. Allen, L., M. W. Beijersbergen, R. J. C. Spreeuw, and J. P.Woerdman, "Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes," Phys. Rev. A, Vol. 45, 8185, 1992.
doi:10.1103/PhysRevA.45.8185
6. Willner, A. E., K. Panga, H. Song, K. Zou, and H. Zhou, "Orbital angular momentum of light for communications," Appl. Phys. Rev., Vol. 8, 041312, 2021.
doi:10.1063/5.0054885
7. Willner, A. E., Y. Ren, G. Xie, Y. Yan, L. Li, Z. Zhao, J. Wang, M. Tur, A. F. Molisch, and S. Ashrafi, "Recent advances in high-capacity free-space optical and radio-frequency communications using orbital angular momentum multiplexing," Philos. Trans. A Math. Phy. Eng. Sci., Vol. 375, 20150439, 2017.
8. Cozzolino, D., D. Bacco, B. Da Lio, K. Ingerslev, Y. Ding, K. Dalgaard, P. Kristensen, M. Galili, K. Rottwitt, S. Ramachandran, and L. K. Oxenløwe, "Orbital angular momentum states enabling fiber-based high-dimensional quantum communication," Phys. Rev. App., Vol. 11, 064058, 2019.
doi:10.1103/PhysRevApplied.11.064058
9. Wang, J., S. Chen, and J. Liu, "Orbital angular momentum communications based on standard multi-mode fiber," APL Photonics, Vol. 6, 060804, 2021.
doi:10.1063/5.0049022
10. Ren, Y., L. Li, Z. Wang, et al. "Orbital angular momentum-based space division multiplexing for high-capacity underwater optical communications," Sci. Rep., Vol. 6, 33306, 2016.
doi:10.1038/srep33306
11. Yan, Y., G. Xie, M. Lavery, et al. "High-capacity millimetre-wave communications with orbital angular momentum multiplexing," Nat. Commun., Vol. 5, 4876, 2014.
doi:10.1038/ncomms5876
12. Hui, X., S. Zheng, Y. Chen, et al. "Multiplexed millimeter wave communication with dual Orbital Angular Momentum (OAM) mode antennas," Sci. Rep., Vol. 5, 10148, 2015.
doi:10.1038/srep10148
13. Allen, B., D. Simmons, T. D. Drysdale, and J. Coon, "Performance analysis of an orbital angular momentum multiplexed amplify-and-forward radio relay chain with inter-modal crosstalk," R. Soc. Open Sci., Vol. 6, 181063, 2019.
doi:10.1098/rsos.181063
14. Assimonis, S. D., M. A. B. Abbasi, and V. Fusco, "Millimeter-wave multi-mode circular antenna array for uni-cast multi-cast and OAM communication," Sci. Rep., Vol. 11, 4928, 2021.
doi:10.1038/s41598-021-83301-1
15. Mirhosseini, M., M. Malik, Z. Shi, and R. W. Boyd, "Efficient separation of the orbital angular momentum eigenstates of light," Nat. Commun., Vol. 4, 2781, 2013.
doi:10.1038/ncomms3781
16. Li, C. and S. Zhao, "Efficient separating orbital angular momentum mode with radial varying phase," Opt. Express, Vol. 5, 267-270, 2017.
17. Berkhout, G. C. G., M. P. J. Lavery, J. Courtial, M. W. Beijersbergen, and M. J. Padgett, "Efficient sorting of orbital angular momentum states of light," Phys. Rev. Lett., Vol. 105, 153601, 2010.
doi:10.1103/PhysRevLett.105.153601
18. Paroli, B., A. Cirella, I. Drebot, V. Petrillo, M. Siano, and M. A. C. Potenza, "Asymmetric lateral coherence of OAM radiation reveals topological charge and local curvature," Journal of Optics, Vol. 20, 1-10, 2018.
doi:10.1088/2040-8986/aac936
19. Paroli, B., M. Siano, and M. A. C. Potenza, "The local intrinsic curvature of wavefronts allows to detect optical vortices," Opt. Express, Vol. 27, 17550, 2019.
doi:10.1364/OE.27.017550
20. Scalcinati, L., B. Paroli, M. Zannoni, and M. A. C. Potenza, "Measurement of the local intrinsic curvature of a l = 1 radio-vortex at 30 GHz," Progress In Electromagnetic Research M, Vol. 94, 1-8, 2020.
doi:10.2528/PIERM20041407
21. Paroli, B., M. Siano, and M. A. C. Potenza, "Measuring the topological charge of orbital angular momentum radiation in single-shot by means of wavefront intrinsic curvature," Appl. Opt., Vol. 59, 5258, 2020.
doi:10.1364/AO.392341
22. Paroli, B., M. Siano, and M. A. C. Potenza, "A composite beam of radiation with orbital angular momentum allows effective local, single-shot measurement of topological charge," Opt. Commun., Vol. 459, 2020.
doi:10.1016/j.optcom.2019.125049
23. Paroli, B., M. Siano, and M. A. C. Potenza, "Dense-code free space transmission by local demultiplexing optical states of a composed vortex," Opt. Express, Vol. 29, 14412-14424, 2021.
doi:10.1364/OE.417772
24. Koksal, K., M. Babiker, V. E. Lembessis, and J. Yuan, "Chirality and helicity of linearly-polarised Laguerre-Gaussian beams of small beam waists," Opt. Commun., Vol. 490, 126907, 2021.
doi:10.1016/j.optcom.2021.126907