Nondecaying surface plasmon polaritons in linear chains of silver nanospheroids

Abstract

We consider propagation of surface plasmon polaritons in linear chains of equidistant metallic nanospheroids. We show that, for suitably chosen parameters, the propagation is free of spatial decay in spite of the full account of absorptive losses in the metal.

Overcoming the adverse effects of substrate on the waveguiding properties of plasmonic nanoparticle chains

“…This geometry is characterized by a more efficient electromagnetic coupling of the neighboring spheroids and, therefore, by a more efficient SPP propagation through the waveguide. 21,22,35 More specifically, in the case of oblate spheroids, the two longer spheroid semiaxes are oriented orthogonally to the chain. In vacuum, this waveguide would have been cylindrically symmetric.…”

“…Note that we consider the same geometrical chain parameters as were used by us previously. 21 In particular, the longer semiaxes of the spheroids are always orthogonal to the chain. However, when the chain is placed close to a substrate, there are additional options for the chain arrangement, as shown in Fig.…”

“…In our previous work, we have used the additional degrees of freedom that are inherent in nonspherical particles such as oblate and prolate spheroids to solve some of these problems. [20][21][22] We have found that, generally, chains of oblate spheroids (nanodisks) whose short axes are aligned with the axis of the chain can overcome many of the existing difficulties. In particular, such waveguides are characterized by high field localization, dispersion curves of sufficient slope to form well-defined wave packets and by efficient propagation even in the presence of Ohmic losses.…”

“…Propagation and decay of SPPs in infinite or semi-infinite linear, perfectly periodic chains are well understood at present. 21,23,24 Although a perfectly periodic chain is an idealization, it was shown that weak disorder 23,25,26 does not have a dramatic effect on long-range SPP propagation. Dispersion relations and transient processes (wave packet transmission) in plasmonic chains have also been studied in detail.…”

“…19,20,[27][28][29] In particular, it was found that chains of spherical particles cannot support propagation of well-formed wave packets due to the flatness of the corresponding dispersion curves. This, in particular, has motivated our interest in chains of non-spherical particles such as prolate or oblate spheroids, 20,21 which can serve as broadband SPP waveguides. Moreover, curved chains of spheroids exhibit unique properties such as high anisotropy and polarization sensitivity.…”