Plasmonic vortices: a review

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.