Polarization singularities: Progress, fundamental physics, and prospects

Polarization singularities, describing the points where the state of polarization is indeterminate, reveal the polarization topology in vectorial optical fields, which include two-/three-dimensional topologies such as C-points, V-points, L-lines, Mobius strips, links, and knots. Compared with the phase singularities, it has more parameters to manipulate, which bring forth a series of novel optical phenomena and potential applications. In this Perspective, the research progress and development of polarization singularities are reviewed from the mathematical description, generation, detection, propagation dynamics, and related applications. In particular, we focused on the three-dimensional spatial propagation and the topological characteristics of polarization singularities in detail and revealed some basic fundamental physical phenomena and the novel effects of polarization singularities. We aim to touch on the key research studies in this field and provide insight into the current status and the challenges to the research studies. Finally, we outline the exciting prospects for the future that are yet to be realized.