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The effect of self-excitation of radio waves in the metal–insulator–metal structure doped with metal nanowires is predicted and its theory is developed. Both the transient stage of self-excitation and the steady-state regime of self-oscillation are analyzed in a fully analytical form. The numerical estimates demonstrate that this effect can be used for diverse practical purposes, in particular, for radio frequency wireless power harvesting. These findings extend the approach developed in nano-optics to the field of electrical engineering. [ABSTRACT FROM AUTHOR]

A first-principles theoretical approach to the effective dielectric permittivity of a nanocomposite, which contains nanoinclusions dispersed in a host dielectric enclosed between two parallel metallic electrodes, is developed. The inclusions are modeled by spheroids, and their response to the external electric field is found using the point dipole approximation and Green's function approach. As a result, besides the mutual interactions between the induced dipoles, the local field in the nanocomposite contains also a contribution from the dipole field reflected from the capacitor electrodes. It is shown that the nanocomposite dielectric permittivity is determined by an average inclusion polarizability density, and its dependence on the aspect ratio and orientations of inclusions is found analytically and investigated. The theoretical predictions derived in the paper are in excellent agreement with the available experimental data and can be used for a proper design of nanocomposite capacitors. [ABSTRACT FROM AUTHOR]

A first-principles theory of electrical breakdown in nanocomposite capacitors, which considers the trapping and scattering (extinction) of electrons originating from the presence of nanoinclusions in the polymer matrix, is developed. The breakdown strength relative to its value for a neat polymer is expressed in terms of two parameters, one of which is determined by the volume density of the nanoinclusion polarizability and the other one is proportional to the electron trap surface density around an inclusion, while the effect of electron scattering is shown to be insignificant. A comparison of the theoretical predictions with diverse experimental data demonstrates an excellent agreement and suggests an effective tool for the design of nanocomposite capacitors. [ABSTRACT FROM AUTHOR]

We propose a generator of surface plasmon polaritons (SPPs) which, unlike spasers or plasmon lasers, does not require stimulated emission in the system. Its principle of operation is based on a positive feedback which an ensemble of classical oscillating dipoles experiences from a reflective surface located in its near field. The generator design includes a nanocavity between two metal surfaces which contains metal nanoparticles in its interior. The whole structure is placed onto a prism surface that allows one to detect the generated SPPs in the Kretschmann configuration. The generation process is driven by a moderate DC voltage applied between the metal covers of the cavity. Both the generation criterion and the steady-state operation of the generator are investigated. [ABSTRACT FROM AUTHOR]

Pronounced peaks in both photoluminescence and light scattering from an array of almost parallel oriented, needle-shaped organic nanoaggregates on mica are observed as a function of angle of incidence. Within the framework of a simple theoretical model, we identify those peaks as originating from the launching of normal modes in the nanofibers, both radiative and waveguiding. Quantitative information is obtained about the mode spectrum and morphology of nanoscaled objects from a simple far field scattering measurement. [ABSTRACT FROM AUTHOR]

Laser-supported, dipole-assisted self-assembly results in blue-light guiding nanostructures, namely single-crystalline nanofibers of hexaphenyl molecules. The nanofibers are up to 1 mm long, extremely well-aligned to each other and their cross sections can be tuned to span the range from nonguiding to guiding single optical modes at λ = 425.5 nm. An analytical theory for such organic waveguides can reproduce quantitatively the experimentally observed behavior. From the measured damping of propagating, vibrationally dressed excitons the imaginary part of the dielectric function of isolated nanoscaled organic aggregates is determined. [ABSTRACT FROM AUTHOR]

A fully analytical semiclassical theory of cooperative optical processes which occur in an ensemble of molecules embedded in a spherical core-shell nanoparticle is developed from first principles. Both the plasmonic Dicke effect and spaser generation are investigated for the designs in which a shell/core contains an arbitrarily large number of active molecules in the vicinity of a metallic core/shell. An essential aspect of the theory is an ab initio account of the feedback from the core/shell boundaries which significantly modifies the molecular dynamics. The theory provides rigorous, albeit simple and physically transparent, criteria for both plasmonic superradiance and surface plasmon generation. [ABSTRACT FROM AUTHOR]

The novel effect of self-excitation of surface plasmons (SESP) in a plasmonic nanocavity is predicted, and its theory is developed from first principles. It is assumed that the cavity is formed by a nanogap between two metals and contains polarizable inclusions. Basing on the dyadic Green's function of the structure, the equations for the field in the cavity are investigated. It is shown that under certain conditions the field becomes unstable that leads to its self-excitation. The threshold criterion for self-excitation as well as the frequency of self-oscillation are derived in an analytical form. The SESP effect is explained in terms of a positive feedback for the polarization of inclusions provided by the field reflected from the cavity walls. These findings suggest a principally new avenue to surface plasmon generation which does not employ stimulated emission and is different from SPASER or plasmon laser. [ABSTRACT FROM AUTHOR]

A novel type of laser spectroscopy for the investigation of the collisional dynamics of atoms in the close vicinity of a surface has been developed. The technique utilizes excitation of the vapor atoms in two crossed laser fields, one of which is directed normally to the surface, whereas the other one excites an evanescent wave propagating along the surface. The results, obtained for sodium atoms near a dielectric prism surface, are quantitatively reproduced by a rigorous theoretical approach. This new, nonintrusive method allows one to distinguish by pure optical means between different groups of atoms and to extract their two-dimensional velocity distributions.

Two-photon laser-induced fluorescence measurements of transition frequencies and lifetimes of laser-excited Na atoms are presented as a function of distance (2-3nm) to metal surfaces of different roughness. We characterized the surface roughness by fitting a Gaussian height-height correlation function to force microscopic data. An unusually small red shift of the Na transition frequency of a few hundred megahertz was observed. In the framework of a quantum-mechanical linear optical response formalism we fitted the lifetime and the frequency shift data simultaneously to obtain effective parameters of a selvedge dielectric function. In that way we are able to take into account both surface roughness and nonlocality, which in turn result in the observed small frequency shifts.