Plasmonic meta-atoms and metasurfaces Meinzer, Nina; Barnes, William L; Hooper, Ian R
Nature photonics,
12/2014, Volume:
8, Issue:
12
Journal Article
Peer reviewed
Open access
Despite the extraordinary degree of interest in optical metamaterials in recent years, the hoped-for devices and applications have, in large part, yet to emerge. It is becoming clear that the first ...generation of metamaterial-based devices will most probably arise from their two-dimensional equivalents -- metasurfaces. In this Review, we describe recent progress in the area of metasurfaces formed from plasmonic meta-atoms. In particular, we approach the subject from the perspective of the fundamental excitations supported by the meta-atoms and the interactions between them. We also identify some areas ripe for future research and indicate likely avenues for future device development.
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We present experimental evidence of sharp spectral features in the optical response of 2D arrays of gold nanorods. A simple coupled dipole model is used to describe the main features of the observed ...spectral line shape. The resonance involves an interplay between the excitation of plasmons localized on the particles and diffraction resulting from the scattering by the periodic arrangement of these particles. We investigate this interplay by varying the particle size, aspect ratio, and interparticle spacing, and observe the effect on the position, width, and intensity of the sharp spectral feature.
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Abstract In this report we use material parameters to calculate the strength of the expected Rabi splitting for a molecular resonance. As an example we focus on the molecular resonance associated ...with the C=O bond in a polymer host, specifically the stretch resonance at ∼1730 cm −1 . Two related approaches to modelling the anticipated extent of the coupling are examined, and the results compared with data from experiments available in the literature. The approaches adopted here indicate how material parameters may be used to assess the potential of a material to exhibit strong coupling, and also enable other useful parameters to be derived, including the molecular dipole moment and the vacuum cavity field strength.
Plant cell walls contain elaborate polysaccharide networks and regulate plant growth, development, mechanics, cell-cell communication and adhesion, and defense. Despite conferring rigidity to support ...plant structures, the cell wall is a dynamic extracellular matrix that is modified, reorganized, and degraded to tightly control its properties during growth and development. Far from being a terminal carbon sink, many wall polymers can be degraded and recycled by plant cells, either via direct re-incorporation by trans- glycosylation or via internalization and metabolic salvage of wall-derived sugars to produce new precur- sors for wall synthesis. However, the physiological and metabolic contributions of wall recycling to plant growth and development are largely undefined. In this review, we discuss long-standing and recent evi- dence supporting the occurrence of cell-wall recycling in plants, make predictions regarding the develop- mental processes to which wall recycling might contribute, and identify outstanding questions and emerging experimental tools that might be used to address these questions and enhance our understanding of this poorly characterized aspect of wall dynamics and metabolism.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Arrays of metallic particles may exhibit optical collective excitations known as surface lattice resonances (SLRs). These SLRs occur near the diffraction edge of the array and can be sharper than the ...plasmon resonance associated with the isolated single particle response. We have fabricated and modeled arrays of silver nanoparticles of different geometries. We show that square, hexagonal, and honeycomb arrays show similar SLRs; no one geometry shows a clear advantage over the others in terms of resonance linewidth. We investigate the nature of the coupling between the particles by looking at rectangular arrays. Our results combine experiment and modeling based on a simple coupled-dipole model.
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In computational ghost imaging, the object is illuminated with a sequence of known patterns and the scattered light is collected using a detector that has no spatial resolution. Using those patterns ...and the total intensity measurement from the detector, one can reconstruct the desired image. Here we study how the reconstructed image is modified if the patterns used for the illumination are not the same as the reconstruction patterns and show that one can choose how to illuminate the object, such that the reconstruction process behaves like a spatial filtering operation on the image. The ability to directly measure a processed image allows one to bypass the post-processing steps and thus avoid any noise amplification they imply. As a simple example we show the case of an edge-detection filter.
Nonlinear optical devices and their implementation into modern nanophotonic architectures are constrained by their usually moderate nonlinear response. Recently, epsilon-near-zero (ENZ) materials ...have been found to have a strong optical nonlinearity, which can be enhanced through the use of cavities or nano-structuring. Here, we study the pump dependent properties of the plasmon resonance in the ENZ region in a thin layer of indium tin oxide (ITO). Exciting this mode using the Kretschmann-Raether configuration, we study reflection switching properties of a 60 nm layer close to the resonant plasmon frequency. We demonstrate a thermal switching mechanism, which results in a shift in the plasmon resonance frequency of 20 THz for a TM pump intensity of 70 GW cm
. For degenerate pump and probe frequencies, we highlight an additional two-beam coupling contribution, not previously isolated in ENZ nonlinear optics studies, which leads to an overall pump induced change in reflection from 1% to 45%.
Simple analytic expressions for the polarizability of metallic nanoparticles are in wide use in the field of plasmonics, but their origins are not obvious. In this article, expressions for the ...polarizability of a particle are derived in the quasistatic limit in a manner that allows the physical origin of the terms to be clearly seen. The discussion is tutorial in nature, with particular attention given to the role of particle shape since this is a controlling factor in particle plasmon resonances.
Strong light-matter coupling occurs when the rate of energy exchange between an electromagnetic mode and a molecular ensemble exceeds competing dissipative processes. The study of strong coupling has ...been motivated by applications such as lasing and the modification of chemical processes. Here we show that strong coupling can be used to create phase singularities. Many nanophotonic structures have been designed to generate phase singularities for use in sensing and optoelectronics. We utilise the concept of cavity-free strong coupling, where electromagnetic modes sustained by a material are strong enough to strongly couple to the material's own molecular resonance, to create phase singularities in a simple thin film of organic molecules. We show that the use of photochromic molecules allows for all-optical control of phase singularities. Our results suggest what we believe to be both a new application for strong light-matter coupling and a new, simplified, more versatile means of manipulating phase singularities.
We consider a two-dimensional honeycomb lattice of metallic nanoparticles, each supporting a localized surface plasmon, and study the quantum properties of the collective plasmons resulting from the ...near-field dipolar interaction between the nanoparticles. We analytically investigate the dispersion, the effective Hamiltonian, and the eigenstates of the collective plasmons for an arbitrary orientation of the individual dipole moments. When the polarization points close to the normal to the plane, the spectrum presents Dirac cones, similar to those present in the electronic band structure of graphene. We derive the effective Dirac Hamiltonian for the collective plasmons and show that the corresponding spinor eigenstates represent Dirac-like massless bosonic excitations that present similar effects to electrons in graphene, such as a nontrivial Berry phase and the absence of backscattering off smooth inhomogeneities. We further discuss how one can manipulate the Dirac points in the Brillouin zone and open a gap in the collective plasmon dispersion by modifying the polarization of the localized surface plasmons, paving the way for a fully tunable plasmonic analogue of graphene.
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