Localized and delocalized surface-plasmon-mediated light tunneling through monolayer hexagonal-close-packed metallic nanoshells

Abstract

We studied theoretically light transmission through a monolayer of hexagonal-close-packed nanoparticles consisting of a metallic shell and a dielectric core. We found that light can transmit through the dense particle assemblies via excitation of a variety of surface-plasmons ͑SPs͒. Localized SPs confined within metal nanoshells can mediate a narrow-band dispersionless transmission resonance ͑TR͒. Wide-band TRs were also observed as a result of strong near-field interparticle SP couplings, forming hybrid modes that are either localized at the nanogaps between adjacent particles or confined in the lattice pores, or distributed across the structure, each with distinct dispersion characteristics. Optical tuning strategies of these TRs are also elucidated that can allow for observation of SP anticrossing effects. DOI: 10.1103/PhysRevB.80.165401 PACS number͑s͒: 73.20.Mf, 42.25.Bs, 78.67.Bf, 78.66.Bz In the past decade, metal films perforated with a periodic array of subwavelength holes or slits attract much interest after the report of enhanced optical transmittance ͑EOT͒ by Ebbesen et al. 1 The EOT phenomenon is generally attributed to propagating surface-plasmon polaritons ͑SPPs͒, 2 which are excited by the incident light on the input side of the metal film, then evanescently tunnel to the exit side through the building up of strong electromagnetic fields above the apertures, and are finally re-emitted into optical far field. The SPP waves are Bragg scattered by the periodic apertures and thus are referred to as Bragg-type SPP modes. Although other theoretical models are also proposed, 3 many efforts have been made to study whether localized resonance modes in apertures can also bring EOT which should be independent of periodicity. 4 Individual metallic nanoparticles can support localized surface-plasmons ͑SPs͒, whose resonance frequency depends on the particle size, shape, and composition, and also on the surrounding medium. 5 At localized SP resonances, the huge electric field enhancement established on particle surface leads to a wealth of optical properties useful in surface enhanced Raman scattering, 6 optical antennas, 7 and optical tweezers.8 For regularly spaced metal nanoparticles, the interactions of particle SP resonances can result in interesting collective optical properties. Lamprecht et al. 9 and Hicks et al. 10 have shown that the lineshape of these localized SPs can be controlled via coherent dipole far-field interactions. Recently extremely narrow plasmon resonances in one-and two-dimensional ͑2D͒ arrays of metal nanoparticles have been predicted [11][12][13] and observed experimentally, 14,15 which are revealed to be due to a diffraction coupling of localized SPs with a diffracted grazing wave at a Wood anomaly. 14 With these great efforts, a clear physical picture has been established about light interaction with two-dimensional ͑2D͒ metal nanoparticle arrays, where the excitation of dipole plasmon mode and its far-field interaction are dominant. However, less is known about the optical prop...

Shaping the photoluminescence from gold nanoshells by cavity plasmons in dielectric-metal core-shell resonators

“…11,18,24,25,31,32 In the following, we will demonstrate that the modulated PL emission is spectrally tunable. It is well known that in the frame of Mie theory, the scattering coefficients corresponding to the cavity plasmons are dependent on the cavity size and also on the refractive index of the dielectric core.…”

“…2(b) that each decomposed spectrum presents a sharp absorption peak, arising from the excitation of the cavity plasmon resonance because of the phase retardation effect. 25,30,31 By comparing Fig. 2(a) and Fig.…”

Bottom-up fabrication approaches to novel plasmonic materials

“…The distributions of the electric field amplitude at the transmission resonances were also calculated and are shown in the insets of Figure 9(b). The resonances predicted at 1050 nm were rationalized to result from a partially localized SP mode (cavity mode) because the remarkable field enhancement is concentrated within the cavities [41]. The main peak at 2070 nm could arise from the excitation of a highly localized SP mode with its electric field tightly confined at the nanogaps between adjacent metallic colloidal particles [41].…”

“…The resonances predicted at 1050 nm were rationalized to result from a partially localized SP mode (cavity mode) because the remarkable field enhancement is concentrated within the cavities [41]. The main peak at 2070 nm could arise from the excitation of a highly localized SP mode with its electric field tightly confined at the nanogaps between adjacent metallic colloidal particles [41]. In addition, the mode at 1250 nm predicted in the calculation for the nanocup array could be explained as contribution from a delocalized SP mode excited in the structure because the corresponding enhanced field is not tightly confined within the nanogaps, but instead extends into the surrounding medium (i.e.…”

Shaping the fluorescence emission by cavity plasmons in dielectric-metal core-shell resonators

“…Moreover, these emission enhancements show up as verticals in the angle-resolved fluorescence spectrum, indicating highly localized nature of the cavity plasmon resonances. 34 More importantly, Fig. 2(a) demonstrates that the fluorescence emission enhanced by different cavity plasmon resonances exhibits different angular distributions.…”