Spin‐Switchable Optics for Surface Plasmon Polaritons Utilizing Nanogroove‐Pair Array

Abstract

Manipulating surface plasmon polaritons (SPPs) in a spin‐controlled manner has opened new possibilities in various applications. Generating spin‐switchable arbitrary complex wavefronts of SPPs using subwavelength structures is highly desirable. Here, the nanogroove‐pair unit (NP), a powerful structure enabling independent amplitude and phase control for spin‐encoded SPP generation, is introduced. Through an NP‐array structure, a comprehensive design strategy for generating SPPs with predefined wavefronts is presented for both left‐ and right‐handed circular polarizations. As an example, a plasmonic lens capable of spin‐switchable focusing is designed with an exceptionally high extinction ratio. Additionally, various complex wavefronts, such as bifocusing, nondiffracting beaming, asymmetric focusing, and focal length switching, all incorporating spin‐switchable features, are presented. The proposed scheme represents a significant advancement in polarization‐controlled wavefront shaping for SPPs, offering potential for diverse applications, including plasmonic switches, particle trapping and manipulation, and polarization sensing.