Reversed ellipsoidal troughs sculpted in plasmonic multilayer nanomembranes

Abstract

Nanomembranes represent a versatile novel building block in micro- and nanoelectromechanical systems, inspired by biological cell membranes. If built as quasi-2D multilayer metal-dielectric nanocomposites, they represent a natural choice for the use in plasmonics and optical metamaterials, ensuring a new degree of design freedom and thus a number of new applications. In this contribution we consider surface sculpting of two types of three-layer nanomembranes – metal-insulator-metal (MIM) and insulator-metal-insulator (IMI) structures. The geometry we analyze represents troughs with ellipsoidal profiles sculpted in the multilayer nanomembranes, simultaneously acting as plasmonic waveguides and ensuring tailoring of frequency dispersion of the plasmonic nanomembranes. We determine frequency dispersions of the scattering parameters for the simulated nanomembranes, as well as the spatial ditribution of the optical near fields in and around them, both evanescent (plasmon-polariton based) and propagating. To this purpose we utilize finite element method simulations. The obtained results show that our IMI structures exhibit a behavior similar to that of the EOT arrays, resulting in optical transparency of the structure for resonant plasmonic modes. On the other hand, MIM structures offer an excellent confinement of electromagnetic radiation within the dielectric layer. We conclude that both MIM and IMI channels allow for additional degrees of freedom in customization the nanomembrane evanescent fields, making a way to numerous potential applications.