Invisibility Dips of Near‐Field Energy Transport in a Spoof Plasmonic Metadimer

Abstract

Invisibility dips, i.e., minima in scattering spectrum associated with asymmetric Fano-like line-shapes, have been predicted with transformation optics in studying strong coupling between two plasmonic nanoparticles. This feature of strongly coupled plasmonic nanoparticles holds promise for sensor cloaking. It requires an extremely narrow gap between the two nanoparticles, preventing its experimental observation at optical frequencies. Here, the concept of spoof surface plasmons is used to facilitate the strong coupling between two spoof-localized-surface-plasmon (SLSP) resonators. Instead of observing in far field, the near-field energy transport is probed through the two SLSP resonators. By virtue of enhanced coupling between the two resonators stacked vertically, a spectral transmission dip with asymmetric Fano-like line-shape, similar to the far-field "invisibility dips" predicted by transformation optics, is observed. The underlying mode interference mechanism is further demonstrated by directly imaging the field maps of interfered waves that are tightly localized around the resonators. These near-field "invisibility dips" may find use in near-field sensing, on-chip switching, filters, and logical operation elements.

Programmable Controls of Multiple Modes of Spoof Surface Plasmon Polaritons to Reach Reconfigurable Plasmonic Devices

“…In order to realize similar SPPs at low frequencies, the concept of spoof surface plasmon polaritons (SSPPs) was proposed since 2004 by decorating a series of 3D periodically artificial structures on the metal surface. [8,9] Hereafter, many related works have been reported based on SSPPs, [10][11][12][13][14][15][16][17][18][19][20] which have advantages of low transmission loss, highly localized fields, low crosstalk, and so on.Recently, programmable metamaterials and metasurfaces have been developed greatly for the dynamic manipulation of electromagnetic (EM) waves, which give the possibility for a single device to possess different functionalities that can be electrically switched through field programming. [7] To integrate such a single-conductor SSPP transmission line with the conventional two-conductor microwave transmission lines efficiently, some matching transitions were proposed to make a smooth conversion between the SSPP modes and traditional guided-wave modes.…”

“…[7] To integrate such a single-conductor SSPP transmission line with the conventional two-conductor microwave transmission lines efficiently, some matching transitions were proposed to make a smooth conversion between the SSPP modes and traditional guided-wave modes. [8,9] Hereafter, many related works have been reported based on SSPPs, [10][11][12][13][14][15][16][17][18][19][20] which have advantages of low transmission loss, highly localized fields, low crosstalk, and so on.Recently, programmable metamaterials and metasurfaces have been developed greatly for the dynamic manipulation of electromagnetic (EM) waves, which give the possibility for a single device to possess different functionalities that can be electrically switched through field programming. [21][22][23][24][25][26][27] However, only a few works for the dynamic manipulation of SSPPs have been reported at both terahertz [28][29][30] and microwave [16,[31][32][33][34][35] frequencies, and that most of them are simply tunable SSPPs rather than programmable ones.…”

“…[7] To integrate such a single-conductor SSPP transmission line with the conventional two-conductor microwave transmission lines efficiently, some matching transitions were proposed to make a smooth conversion between the SSPP modes and traditional guided-wave modes. [8,9] Hereafter, many related works have been reported based on SSPPs, [10][11][12][13][14][15][16][17][18][19][20] which have advantages of low transmission loss, highly localized fields, low crosstalk, and so on.…”

Mimicking Localized Surface Plasmons with Structural Dispersion

“…To mimic the exotic properties of optical plasmons at low frequencies, the concept of spoof surface plasmon polaritons was introduced by Pendry et al in 2004 . Since then, a number of efforts have been made to realize low‐frequency plasmonics and to explore its applications . In 2012, this concept was extended to LSPs and a corrugated PEC cylinder has been shown to exhibit similar scattering characteristics as a Drude metal rod .…”

Toroidal Localized Spoof Plasmons on Compact Metadisks

“…A similar phenomenon is also experimentally demonstrated, by changing the background medium from air to oil (relative permittivity of 2.5), as shown in Figure f. The resonance frequency shifts from 4.17 GHz in the air to 3.7 GHz in the oil and the corresponding resonance frequency shift per refractive index is 0.8 GHz/refractive index unit. Therefore, the toroidal LSSPs resonator can work as a deformation sensor and to detect the refractive index changes of the surrounding medium.…”