Resonant cavity modes of circular plasmonic patch nanoantennas

Minkowski, Fred; Wang, Feng; Chakrabarty, Ayan; Wei, Qi‐Huo

doi:10.1063/1.4862430

Cited by 49 publications

(52 citation statements)

References 35 publications

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“…Similar equations were found for other plasmonic cavities, although an additional phase term was often considered 47,54,56,67,68 and more complex equations have also been studied. 60,69,70 The results of the spectral position of the TCPs given by this simple analytical model for s = 1, 2, 4, and 6 are superimposed to the calculated field enhancement in Figure 2d as black solid lines. The agreement between the positions of the TCPs as predicted from the model and the calculations is remarkable and indeed suggests a spectral decoupling of the two types of resonances.…”

Section: Acs Photonicsmentioning

confidence: 99%

The Morphology of Narrow Gaps Modifies the Plasmonic Response

et al. 2015

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ABSTRACT:The optical response of a plasmonic gapantenna is mainly determined by the Coulomb interaction of the two constituent arms of the antenna. Using rigorous calculations supported by simple analytical models, we observe how the morphology of a nanometric gap separating two metallic rods dramatically modifies the plasmonic response. In the case of rounded terminations at the gap, a conventional set of bonding modes is found that red-shifts strongly with decreasing separation. However, in the case of flat surfaces, a distinctly different situation is found with the appearance of two sets of modes: (i) strongly radiating longitudinal antenna plasmons (LAPs), which exhibit a red-shift that saturates for very narrow gaps, and (ii) transverse cavity plasmons (TCPs) confined to the gap, which are weakly radiative and strongly dependent on the separation distance between the two arms. The two sets of modes can be independently tuned, providing detailed control of both the near-and far-field response of the antenna. We illustrate these properties also with an application to larger infrared gap-antennas made of polar materials such as SiC. Finally we use the quantum corrected model (QCM) to show that the morphology of the gap has a dramatic influence on the plasmonic response also for subnanometer gaps. This effect can be crucial for the correct interpretation of charge transfer processes in metallic cavities where quantum effects such as electron tunneling are important. KEYWORDS: optical antennas, plasmonic gaps, cavity modes, antenna modes, quantum effects, quantum corrected model, plasmonic resonances, phononic resonances M etallic particles can show a strong optical response due to the excitation of resonant plasmonic modes, making light manipulation possible in structures of dimensions comparable to or smaller than the wavelength. Typical effects are the efficient emission of radiation and the concentration of the incoming light energy in small volumes, thus justifying the characterization of these metallic structures as optical antennas. 1,2 Modifications of the geometry, size, or materials 3−6 affect the optical response. In particular, the resonant modes of optical antennas consisting of two metallic particles separated by a narrow gap show significant sensitivity to the properties of the gap. 7−19 In an optical antenna, a change in geometry can simultaneously affect both the strength and wavelength of its resonances and modify both the far-and near-field response. It is usually a challenge, for example, to control the near field without affecting the far-field properties. In this theoretical work, we discuss how the coexistence 20,21 of two different and mostly spectrally decoupled types of modes in flat-gap antennas, namely, transverse cavity modes 22 and longitudinal antenna modes, 15 allows for a more flexible tuning of far-and near-field properties compared to that of the conventional spherical-gap terminations 13,17,23 The importance of the gap morphology 24 is particularly pronounced for nanometer-...

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Section: Acs Photonicsmentioning

confidence: 99%

The Morphology of Narrow Gaps Modifies the Plasmonic Response

et al. 2015

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“…1c) confirms the excitation of the resonant plasmon cavity mode in the gap areas between the top Au disk array and the bottom Au film [34]. The plasmon cavity modes in this kind of MDM structures can be precisely modified at the frequency region by tuning the structural parameters including the optical constants of the dielectric disks and the size of the plasmonic resonator based on the great efforts in this field by Wei et al [34,35]. Thereby, for the absorption peak at λ=647 nm, the main contributions are the excitation of the localized plasmon resonance of the Au disks and the plasmon cavity mode of the MDM triple-layer structure [34].…”

Section: Resultsmentioning

confidence: 56%

Improving Plasmon Sensing Performance by Exploiting the Spatially Confined Field

Liu

et al. 2015

Plasmonics

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A universal method for improving sensing performance has been computationally studied based on a common triple-layer metal-dielectric-metal (MDM) plasmonic perfect absorber (PA). Calculation results show that the originally idled resonant optical field in the middle dielectric spacer can be exploited to enhance the sensing capability via etching the dielectric spacer to open a channel for analyte. By comparing with the sensitivity (S) of the common PA-based sensor, an enhancement factor up to 5.0 can be achieved for an etched PA-based sensor. Moreover, in order to maintain the mechanical stability of the structure, a modified PA-based sensor platform with a solid support for the suspended plasmonic disks array was further employed to study the sensing properties. In comparison with the referenced sensor without suspension technique, all the three sensing factors of the S, the figure of merit (FOM), and the spectral intensity difference related figure of merit (FOM*) are noticeably improved with the enhancement factors up to 2.5, 3, and 57, respectively. In addition, since there is no special dealing with the structure except the need of hollowing the dielectric spacer to open the sensing channel for the analysis, the predicted method profiles itself as a simple and universal strategy to improve the sensing performance of a wide variety of nanoplasmonic sensors.

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“…[31][32][33][34][35][36][37][38] The field patterns of the resonance modes in a CMDMR are similar to the whispering gallery modes (WGM) in a high-refractive-index dielectric disk. Therefore, these modes are known as WGM-like plasmonic cavity modes in the literature.…”

Section: -30mentioning

confidence: 79%

“…can be applied as an approximation, as reported in Ref. [36]. In the meantime, we expect the Dirichlet boundary condition, ( ) 0 z ER , to be appropriate in the coated case (the closed cavity).…”

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confidence: 99%

Core–Shell-Structured Dielectric–Metal Circular Nanodisk Antenna: Gap Plasmon Assisted Magnetic Toroid-like Cavity Modes

et al. 2014

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Plasmonic nanoantennas, the properties of which are essentially determined by their resonance modes, are of interest both fundamentally and for various applications. Antennas with various shapes, geometries and compositions have been demonstrated, each possessing unique properties and potential applications. Here, we propose the use of a sidewall coating as an additional degree of freedom to manipulate plasmonic gap cavity modes in strongly coupled metallic nanodisks. It is demonstrated that for a dielectric middle layer with a thickness of a few tens of nanometers and a sidewall plasmonic coating of more than ten nanometers, the usual optical magnetic resonance modes are eliminated, and only magnetic toroid-like modes are sustainable in the infrared and visible regime. All of these deep-subwavelength modes can be interpreted as an interference effect from the gap surface plasmon polaritons. Our results will be useful in nanoantenna design, high-Q cavity sensing, structured light-beam generation, and photon emission engineering. KEYWORDS: Plasmonics, nanoantenna, toroidal mode, optical magnetic resonance 3Surface plasmon polaritons (SPPs) are known as the collective oscillations of conductive electrons at metallic nanostructures and their interfaces.1,2 When the optical field couples with the SPPs in plasmonic nanostructures, some fascinating features and applications arise, such as strong local field enhancement, 3-5 imaging beyond the diffraction limit, 6-10 and extraordinary transmission through periodic arrays of subwavelength holes in optically thick metallic films. 11,12Indeed, any plasmonic nanostructure can be regarded as an optical nanoantenna or plasmonic resonator because of its ability to radiate and collect light, similar to the behavior of RF antennas in the microwave regime. 28-30Recently, circular metal-dielectric-metal resonators (CMDMRs) have been studied as plasmonic microcavities for various applications because of their extremely high Q factor and low modal volume. [31][32][33][34][35][36][37][38] The field patterns of the resonance modes in a CMDMR are similar to the whispering gallery modes (WGM) in a high-refractive-index dielectric disk. Therefore, these modes are known as WGM-like plasmonic cavity modes in the literature. 34,35 More notably, the in-plane magnetic field of one of the basic resonance modes in a CMDMR possesses a vortex distribution and has been interpreted as a predominant magnetic toroidal dipole. 37,38 This behavior is essentially enabled by the plasmon-resonance-induced displacement currents, which can overcome the saturation of the conduction current and promote the optical magnetic resonance from the terahertz up to the visible regime. In this work, we demonstrate that adding a sidewall metallic coating to a CMDMR can strongly affect the mode pattern and the optical characteristics of the cavity modes. Intuitively, the sidewall coating transforms the CMDMR from a sandwiched structure into a core-shell This mode is, in fact, a typical magnetic toroidal dip...

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Resonant cavity modes of circular plasmonic patch nanoantennas

Cited by 49 publications

References 35 publications

The Morphology of Narrow Gaps Modifies the Plasmonic Response

The Morphology of Narrow Gaps Modifies the Plasmonic Response

Improving Plasmon Sensing Performance by Exploiting the Spatially Confined Field

Core–Shell-Structured Dielectric–Metal Circular Nanodisk Antenna: Gap Plasmon Assisted Magnetic Toroid-like Cavity Modes

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