Topology is a mathematical concept that has found numerous applications in physics. Among them, the topological nature of phase singularities of vortex fields has led to the definition of a new branch of optics known as singular optics . One of the most intriguing results in this area is the possibility to structure almost at will the phase and amplitude distributions of an optical field, with possible applications in micromanipulation and trapping of microscopic particles . This possibility is provided by the presence of phase singularity points (PSP) that are quite robust to external perturbations and involve the presence of corresponding amplitude nulls.
Barbuto, M., Alu, A., Bilotti, F., Toscano, A. (2021). Topological fields and their applications to antenna systems. In 2021 International Conference on Electromagnetics in Advanced Applications, ICEAA 2021 (pp.034-034). Institute of Electrical and Electronics Engineers Inc. [10.1109/ICEAA52647.2021.9539602].