Discrete Radiative Modes in Plasmonic Nonlocal Flat Surfaces

This paper provides a comprehensive study of the nonlocality-influenced radiative modes above the light line in the plasmonic nonlocal flat surface, including the plasmonic/dielectric interface, ultrathin plasmonic slab, and plasmonic/dielectric multilayer. We demonstrate that material nonlocality arising from the longitudinal plasmon wave excited in plasmonic material dramatically alters the radiative mode above the light line, leading to the splitting of the Brewster mode in the dispersion relation diagram of the plasmonic slab. And material nonlocality together with structural nonlocality reveals novel discrete radiative modes in the high-frequency regime in the plasmonic/dielectric multilayer at subwavelength scales. Our results highlight the impact of material nonlocality and structural nonlocality on radiative modes in plasmonic flat structures and might contribute to new ideas in optical device design.