Conformal surface plasmons propagating on ultrathin and flexible films

TLDR

Surface plasmon polaritons are subwavelength‑confined electromagnetic waves at metal–dielectric interfaces, promising for photonic circuitry but difficult to control on flexible, curved surfaces. This work introduces conformal surface plasmons, surface plasmon waves that can travel long distances on ultrathin, flexible films across a broad microwave‑to‑mid‑infrared band. The authors experimentally demonstrate CSPs on paper‑like dielectric films 600 times thinner than the wavelength, showing that the films can be bent, folded, and twisted to steer the waves. The experiments confirm that CSPs propagate over long distances in the microwave regime on these ultrathin flexible films, validating their broadband, conformal behavior.

Abstract

Surface plasmon polaritons (SPPs) are localized surface electromagnetic waves that propagate along the interface between a metal and a dielectric. Owing to their inherent subwavelength confinement, SPPs have a strong potential to become building blocks of a type of photonic circuitry built up on 2D metal surfaces; however, SPPs are difficult to control on curved surfaces conformably and flexibly to produce advanced functional devices. Here we propose the concept of conformal surface plasmons (CSPs), surface plasmon waves that can propagate on ultrathin and flexible films to long distances in a wide broadband range from microwave to mid-infrared frequencies. We present the experimental realization of these CSPs in the microwave regime on paper-like dielectric films with a thickness 600-fold smaller than the operating wavelength. The flexible paper-like films can be bent, folded, and even twisted to mold the flow of CSPs.