Studies of metamaterial structures

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The impact of natural modes in plasmonic imaging

Plasmonic imaging is crucial for understanding cellular behaviours for biological sciences, where is used to image and track organelles in cells, such as DNA and virus molecules. Due to the fast dynamics of the intra-cellular processes, it is essential to keep the cells under their native states (i.e. label-free), establishing plasmonic imaging as one of the most powerful tools for studying biological samples. In this article, a theoretical model is presented that accurately predicts the properties of a plasmonic image, paving the route towards the characterization of an imaged nano-object. It is shown that natural modes are not only excited, but actually dominate the intensity and shape of the observed plasmonic image. Hence, the proposed model explains the dynamics forming the plasmonic image and can be used to extract spectroscopy information from current plasmonic imaging techniques

Subradiant entanglement in plasmonic nanocavities

Plasmonic nanocavities are known for their extreme field enhancement and sub-wavelength light confinement in gaps of just a few nanometers. Pairing this with the ability to host quantum emitters, they form highly promising platforms for controlling and engineering quantum states at room temperature. Here, we show how sub-radiant entangled states emerge between two or more quantum emitters within plasmonic nanocavities. We develop a theoretical description that directly links quantum variables to experimentally measurable quantities, such as the extinction cross-section. We show that the lossy nature of plasmonic nanocavities aids the emergence of sub-radiant entangled states between quantum emitters, persisting for 100 times longer than the plasmonic excitation. This work paves the way towards designing and engineering quantum entangled states in ambient conditions with plasmonic nanocavities, for potential applications as rapid quantum memories, quantum communications and quantum sensors

Analytic theory of optical nanoplasmonic metamaterials

Recent advances in nano-fabrication techniques allow for the manufacture of optical metamaterials, bringing their unique and extra-ordinary properties to the visible regime and beyond. However, an analytical description of optical nano-plasmonic metamaterials is challenging due to the characteristic optical behaviour of metals. Here we present an analytical theory that allows to bring established microwave metamaterials models to optical wavelengths. This method is implemented for nano-scaled plasmonic wire-mesh and tri-helical metamaterials, and we obtain an accurate prediction for their dispersive behaviour at optical and near-IR wavelengths

Optical nano-woodpiles: large-area metallic photonic crystals and metamaterials.

Metallic woodpile photonic crystals and metamaterials operating across the visible spectrum are extremely difficult to construct over large areas, because of the intricate three-dimensional nanostructures and sub-50 nm features demanded. Previous routes use electron-beam lithography or direct laser writing but widespread application is restricted by their expense and low throughput. Scalable approaches including soft lithography, colloidal self-assembly, and interference holography, produce structures limited in feature size, material durability, or geometry. By multiply stacking gold nanowire flexible gratings, we demonstrate a scalable high-fidelity approach for fabricating flexible metallic woodpile photonic crystals, with features down to 10 nm produced in bulk and at low cost. Control of stacking sequence, asymmetry, and orientation elicits great control, with visible-wavelength band-gap reflections exceeding 60%, and with strong induced chirality. Such flexible and stretchable architectures can produce metamaterials with refractive index near zero, and are easily tuned across the IR and visible ranges.We acknowledge financial support from EPSRC grant EP/G060649/1, EP/I012060/1, EP/L027151/1, ERC grants LINASS 320503 and 3DIMAGE 291522, EU FP7 280478, and the Leverhulme Trust and Rolls-Royce plc.This is the final version of the article, originally published in Scientific Reports 5, Article number: 8313. DOI: 10.1038/srep08313

Spatiotemporal Dynamics and Control of Strong Coupling in Plasmonic Nanocavities

© 2017 American Chemical Society. In the light-matter strong coupling regime, the excited state of quantum emitters is inextricably linked to a photonic mode, leading to hybrid states that are part light and part matter. Recently, there has been a huge effort to realize strong coupling with nanoplasmonics, since it provides a versatile environment to study and control molecules in ambient conditions. Among the most promising designs are plasmonic nanocavities that confine light to unprecedentedly small volumes. Such nanocavities, though, support multiple types of modes, with different field profiles and radiative decay rates (bright and dark modes). Here, we show theoretically that the different nature of these modes leads to mode beating within the nanocavity and the Rabi oscillations, which alters the spatiotemporal dynamics of the hybrid system. By specifically designing the illumination setup, we decompose and control the dark and bright plasmon mode excitation and therefore their coupling with quantum emitters. Hence, this work opens new routes for dynam ically dressing emitters, to tailor their hybrid states with external radiation