Surface plasmon polaritons (SPPs), surface electromagnetic waves propagating along metal-dielectric interfaces, have found numerous applications in integrated photonic devices, optical storage, and optical sensing, etc. In recent years, there has been a surge of interest in the fundamental and applications of SPPs carrying orbital angular momentum, namely SPP vortices or plasmonic vortices. In this review, we summarize the fundamental concepts of plasmonic vortices, and highlight recent advances in the generation and applications of plasmonic vortices, from SPPs at lightwave frequencies to spoof SPPs at microwave and Terahertz frequencies.

The Newton’s rings are interference patterns with concentric rings, and Newton’s rings experiment is one of the most famous classic optics experiments. Here, we show that if we use a vortex beam, we can obtain generalized Newton’s rings. Unlike traditional Newton’s rings, the generalized ones are no longer concentric rings but spiral arms, and fork-shaped dislocations appear in spiral arms. More interesting, we reveal that both the number of spiral arms and the number of fork-shaped dislocations are equal to the value of topological charge of incident vortex beams. Our theoretical results are demonstrated experimentally. This novel interference pattern can be used for measuring the topological charge of vortex beams.