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Koppens F.H.L.,ICFO - Institute of Photonic Sciences | Chang D.E.,California Institute of Technology | Garcia De Abajo F.J.,CSIC - Institute of Optics | Garcia De Abajo F.J.,University of Southampton
Nano Letters | Year: 2011

Graphene plasmons provide a suitable alternative to noble-metal plasmons because they exhibit much tighter confinement and relatively long propagation distances, with the advantage of being highly tunable via electrostatic gating. Here, we propose to use graphene plasmons as a platform for strongly enhanced light-matter interactions. Specifically, we predict unprecedented high decay rates of quantum emitters in the proximity of a carbon sheet, observable vacuum Rabi splittings, and extinction cross sections exceeding the geometrical area in graphene nanoribbons and nanodisks. Our theoretical results provide the basis for the emerging and potentially far-reaching field of graphene plasmonics, offering an ideal platform for cavity quantum electrodynamics, and supporting the possibility of single-molecule, single-plasmon devices. © 2011 American Chemical Society. Source

Garcia De Abajo F.J.,CSIC - Institute of Optics
Reviews of Modern Physics | Year: 2010

This review discusses how low-energy valence excitations created by swift electrons can render information on the optical response of structured materials with unmatched spatial resolution. Electron microscopes are capable of focusing electron beams on subnanometer spots and probing the target response either by analyzing electron energy losses or by detecting emitted radiation. Theoretical frameworks suited to calculate the probability of energy loss and light emission (cathodoluminescence) are reconsidered and compared with experimental results. More precisely, a quantum-mechanical description of the interaction between the electrons and the sample is discussed, followed by a powerful classical dielectric approach that can be applied in practice to more complex systems. The conditions are assessed under which classical and quantum-mechanical formulations are equivalent. The excitation of collective modes such as plasmons is studied in bulk materials, planar surfaces, and nanoparticles. Light emission induced by the electrons is shown to constitute an excellent probe of plasmons, combining subnanometer resolution in the position of the electron beam with nanometer resolution in the emitted wavelength. Both electron energy-loss and cathodoluminescence spectroscopies performed in a scanning mode of operation yield snapshots of plasmon modes in nanostructures with fine spatial detail as compared to other existing imaging techniques, thus providing an ideal tool for nanophotonics studies. © 2010 The American Physical Society. Source

Kuttge M.,FOM Institute for Atomic and Molecular Physics | Garcia De Abajo F.J.,CSIC - Institute of Optics | Polman A.,FOM Institute for Atomic and Molecular Physics
Nano Letters | Year: 2010

We study the resonant modes of nanoscale disk resonators sustaining metal-insulator-metal (MIM) plasmons and demonstrate the versatility of these cavities to achieve ultrasmall cavity mode volume. Ag/SiO 2/Ag MIM structures were made by thin-film deposition and focused ion beam milling with cavity diameters that ranged from d = 65-2000 nm. High-resolution two-dimensional cavity-mode field distributions were determined using cathodoluminescence imaging spectroscopy and are in good agreement with boundary element calculations. For the smallest cavities (d = 65-140 nm), the lowest order mode (m = 1, n = 1) is observed in the visible spectral range. This mode is of similar nature as the one in plasmonic particle dimers, establishing a natural connection between localized and traveling plasmon cavities. A cavity quality factor of Q = 16 is observed for the 105 nm diameter cavity, accompanied by a mode volume as small as 0.00033λ0 3. The corresponding Purcell factor is 900, making these ultrasmall disk resonators ideal candidates for studies of enhanced spontaneous emission and lasing. © 2009 American Chemical Society. Source

Toudert J.,CSIC - Institute of Optics
Nanotechnology Reviews | Year: 2014

Spectroscopic ellipsometry (SE) is a powerful technique for the characterization of materials, which is able to probe in a sensitive way their nanostructure as well as to get rich information about their dielectric properties, through the interaction of polarized light with matter. In the present trend of developing functional advanced materials of increasing complexity for a wide range of technological applications, works involving SE have flourished and have been reported in an increasing number of articles, reviews, and books. In this context, the aim of this paper is to provide for those among material scientists who are not SE specialists, a concise and updated overview of the capabilities of SE for the characterization of the so-called nano- and metamaterials, especially those presenting active functionalities. Key aspects for a reliable material characterization by SE are given: choice of the setup and measurement conditions, measurement accuracy, definition of a model, sensitivity to parameters. Also, very recent works involving SE are highlighted, especially those dealing with the development of building block materials for optimized or active plasmonics applications, the still ongoing exploration of small-size effects on the dielectric response of matter, the characterization of metamaterials, and the design of detectors with improved accuracy based on coupling of the phase sensitivity of SE with metamaterials engineering. Source

Manjavacas A.,CSIC - Institute of Optics | Abajo F.J.G.D.,CSIC - Institute of Optics | Nordlander P.,Rice University
Nano Letters | Year: 2011

We present a fully quantum mechanical approach to describe the coupling between plasmons and excitonic systems such as molecules or quantum dots. The formalism relies on Zubarev's Green functions, which allow us to go beyond the perturbative regime within the internal evolution of a plasmonic nanostructure and to fully account for quantum aspects of the optical response and Fano resonances in plasmon - excition (plexcitonic) systems. We illustrate this method with two examples consisting of an exciton-supporting quantum emitter placed either in the vicinity of a single metal nanoparticle or in the gap of a nanoparticle dimer. The optical absorption of the combined emitter - dimer structure is shown to undergo dramatic changes when the emitter excitation level is tuned across the gap-plasmon resonance. Our work opens a new avenue to deal with strongly interacting plasmon - excition hybrid systems. © 2011 American Chemical Society. Source

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