Surface plasmon lifetime in metal nanoshells

The lifetime of localized surface plasmon plays an important role in many aspects of plasmonics and its applications. In small metal nanostructures, the dominant mechanism restricting plasmon lifetime is size-dependent Landau damping. We performed quantum-mechanical calculations of Landau damping for the bright surface plasmon mode in a metal nanoshell. In contrast to the conventional model based on the electron surface scattering, we found that the damping rate decreases as the nanoshell thickness is reduced. The origin of this behavior is traced to the spatial distribution of plasmon local field inside the metal shell. We also found that, due to interference of electron scattering amplitudes from nanoshell's two metal surfaces, the damping rate exhibits pronounced quantum beats with changing shell thickness.Comment: 9 pages, 4 Figure

Theory of plasmon-enhanced high-harmonic generation in the vicinity of metal nanostructures in noble gases

We present a semiclassical model for plasmon-enhanced high-harmonic generation (HHG) in the vicinity of metal nanostructures. We show that both the inhomogeneity of the enhanced local fields and electron absorption by the metal surface play an important role in the HHG process and lead to the generation of even harmonics and to a significantly increased cutoff. For the examples of silver-coated nanocones and bowtie antennas we predict that the required intensity reduces by up to three orders of magnitudes and the HHG cutoff increases by more than a factor of two. The study of the enhanced high-harmonic generation is connected with a finite-element simulation of the electric field enhancement due to the excitation of the plasmonic modes.Comment: 4 figure

The LYRA Instrument Onboard PROBA2: Description and In-Flight Performance

The Large Yield Radiometer (LYRA) is an XUV-EUV-MUV (soft X-ray to mid-ultraviolet) solar radiometer onboard the European Space Agency PROBA2 mission that was launched in November 2009. LYRA acquires solar irradiance measurements at a high cadence (nominally 20 Hz) in four broad spectral channels, from soft X-ray to MUV, that have been chosen for their relevance to solar physics, space weather and aeronomy. In this article, we briefly review the design of the instrument, give an overview of the data products distributed through the instrument website, and describe the way that data are calibrated. We also briefly present a summary of the main fields of research currently under investigation by the LYRA consortium

Nanoplasmonic Renormalization and Enhancement of Coulomb Interactions

Nanostructured plasmonic metal systems are known to enhance greatly variety of radiative and nonradiative optical processes, both linear and nonlinear, which are due to the interaction of an electron in a molecule or semiconductor with the enhanced local optical field of the surface plasmons. Principally different are numerous many-body phenomena that are due to the Coulomb interaction between charged particles: carriers (electrons and holes) and ions. These include carrier-carrier or carrier-ion scattering, energy and momentum transfer (including the drag effect), thermal equilibration, exciton formation, impact ionization, Auger effects, etc. It is not widely recognized that these and other many-body effects can also be modified and enhanced by the surface-plasmon local fields. A special but extremely important class of such many-body phenomena is constituted by chemical reactions at metal surfaces, including catalytic reactions. Here, we propose a general and powerful theory of the plasmonic enhancement of the many-body phenomena resulting in a closed expression for the surface plasmon-dressed Coulomb interaction. We illustrate this theory by computing this dressed interaction explicitly for an important example of metal-dielectric nanoshells, which exhibits a reach resonant behavior in both the magnitude and phase. This interaction is used to describe the nanoplasmonic-enhanced Foerster energy transfer between nanocrystal quantum dots in the proximity of a plasmonic nanoshell. Catalysis at nanostructured metal surfaces, nonlocal carrier scattering and surface-enhanced Raman scattering are discussed among other effects and applications where the nanoplasmonic renormalization of the Coulomb interaction may be of principal importance

Spectroscopic studies of fractal aggregates of silver nanospheres undergoing local restructuring

We present an experimental spectroscopic study of large random colloidal aggregates of silver nanoparticles undergoing local restructuring. We argue that such well-known phenomena as strong fluctuation of local electromagnetic fields, appearance of "hot spots" and enhancement of nonlinear optical responses depend on the local structure on the scales of several nanosphere diameters, rather that the large-scale fractal geometry of the sample.Comment: 3.5 pages, submitted to J. Chem. Phy

Mesoscopic Cooperative Emission From a Disordered System

We study theoretically the cooperative light emission from a system of $N\gg 1$ classical oscillators confined within a volume with spatial scale, $L$, much smaller than the radiation wavelength, $\lambda_0=2\pi c/\omega_0$. We assume that the oscillators frequencies are randomly distributed around a central frequency, $\omega_0$, with some characteristic width, $\Omega\ll\omega_0$. In the absence of disorder, that is $\Omega=0$, the cooperative emission spectrum is composed of a narrow subradiant peak superimposed on a wide superradiant band. When $\Omega\neq 0$, we demonstrate that if $N$ is large enough, the subradiant peak is not simply broadened by the disorder but rather splits into a system of random narrow peaks. We estimate the spectral width of these peaks as a function of $N, L, \Omega$, and $\lambda_0$. We also estimate the amplitude of this mesoscopic structure in the emission spectrum.Comment: 25 pages including 6 figure

Hot-electron nanoscopy using adiabatic compression of surface plasmons

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Concave Plasmonic Particles: Broad-Band Geometrical Tunability in the Near Infra-Red

Optical resonances spanning the Near and Short Infra-Red spectral regime were exhibited experimentally by arrays of plasmonic nano-particles with concave cross-section. The concavity of the particle was shown to be the key ingredient for enabling the broad band tunability of the resonance frequency, even for particles with dimensional aspect ratios of order unity. The atypical flexibility of setting the resonance wavelength is shown to stem from a unique interplay of local geometry with surface charge distributions