Efficient formation and tunability of optical scattering directivity of surface waves by a linear array of nanoantennas on a metallic film

Abstract

Photonic spin Hall effect (PSHE) related to spin–orbit interaction of light leads to spin-momentum locking of longitudinal-spin photons of a pump beam into transverse-spin photons of an inherently circularly polarized surface wave like surface plasmon polaritons (SPPs). An excited nanoparticle (NP) above a metal–dielectric interface optically couples pump beam photons into the SPP photons, though an array of NPs may provide a desired and remarkable scattering directivity pattern (SDP). Here we show how a linear array of alike nanoantennas illuminated by an optical beam with different wave polarizations and incidence directions forms the unique SDPs, and we show how the PSHE affects the propagation direction of the scattered SPPs and their SDPs. The scattering patterns for the excited surface wave with remarkable tunability and functionality are studied in two principle cases, namely, broadside and endfire, in which the PSHE may efficiently emerge. The theoretical results developed based on Green’s tensor approach accompanied by the mode-matching technique and quasistatic modeling are in good agreement with the computational results. In this way, the crucial parameters’ effects on the SDPs, such as the elements’ spacing and number in the array, are thoroughly investigated. The reported results pave the way to adaptively engineer the scattering formation of the SPP-type waves for surface optics and photonics applications.