A new perspective on materials for plasmonics

Surface plasmon polaritons are electromagnetic waves propagating on the surface of a metal. Thanks to subwavelength confinement to the surface, they can concentrate optical energy on the micrometer or even nanometer scale, enabling new applications in bio-sensing, optical interconnects, and nonlinear optics, where small footprint and strong field concentration is of the essence. The major obstacle in developing plasmonic applications is dissipative loss, which limits the propagation length of surface plasmons and broadens the bandwidth of surface-plasmon resonances. Here we present a new analysis of plasmonic materials and geometries that fully considers the trade-off between the propagation length and the degree of confinement of surface plasmon polaritons and allows a fair comparison between different substrates.