Long-range higher-order surface-plasmon polaritons

Abstract

Besides the two fundamental symmetric and antisymmetric modes, a thin metal slab surrounded by a dielectric medium supports an infinite number of other modes whose propagation distances, however, are extremely short. We show that such a higher-order mode, normally not regarded to be useful, can turn into a long-range surfaceplasmon polariton in circumstances where the fundamental long-range mode does not exist and the propagation length of the single-interface surface-plasmon polariton is negligible. This transition, which is an electromagnetic near-field phenomenon not previously observed, occurs with a broad range of bandwidths and materials, especially in the context of high-index semiconductors. The long-range behavior of the higher-order surface-plasmon polaritons does not originate from the coupling between the polaritons supported by the individual boundaries, and in some situations it comes with increased field confinement, which is the opposite of what occurs for the fundamental long-range surface mode. Our results, which follow from rigorous electromagnetic theory, provide deeper insight into the foundations of thin-film plasmonics and suggest avenues for enhanced properties of nanophotonic devices involving modern polaritonic media.

Multiphoton Photoemission Microscopy of High-Order Plasmonic Resonances at the Ag/Vacuum and Ag/Si Interfaces of Epitaxial Silver Nanowires

“…Nevertheless, in wavelength size structures Fabry–Perot modes can modulate the PEEM intensities . Although localized high-order plasmonic modes are usually neglected in the literature due to very short propagation lengths, the results of Norrman et al show the possibility of the transition of higher order modes into dominant modes with long propagation lengths. An estimation for the existence of higher order modes, ε r 1 ≤ ε r 2 , where ε r 1 and ε r 2 denote relative permittivity of the metallic slab and the surrounding media, respectively, is indeed fulfilled for our Ag/Si structure.…”

Surface-plasmon polariton solutions at a lossy slab in a symmetric surrounding

“…In this work, we construct a unified theoretical framework and identification of all possible SPP solutions at an absorptive slab in a symmetric, lossless dielectric surrounding [13]. In addition to the ones found in literature, sets of completely new mode solutions are presented.…”

Excitation of “forbidden” guided-wave plasmon polariton modes via direct reflectance using a low refractive index polymer coupling layer

“…Specifically, the energy of a SPP is typically concentrated within approximately one skin depth of the metal-dielectric interface, resulting in large Ohmic losses within the metal layer. Progress has been made in increasing the propagation length of SPP modes through strategic structural designs that move more of the electric field away from the metal film [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. However, this comes at the cost of structural complexity, and the useful range of a typical plasmonic excitation remains in the micrometer range.…”

“…One approach that has been demonstrated to improve propagation lengths in an applications-relevant geometry is the use of structures that support Long-Range Surface Plasmon Polariton (LRSPP) modes [19,[37][38][39][40][41][42][43]. In contrast to traditional SPPs accessed using the Kretschmann configuration, LRSPPs are accessed by inserting a dielectric spacer layer with a refractive index as close as possible to that of the external dielectric layer (on the side of the waveguide opposite that of the prism, typically air or water) between the prism and the metal film (Fig 1c).…”