Ab initio theory of Fano resonances in plasmonic nanostructures and metamaterials

An ab initio theory for Fano resonances in plasmonic nanostructures and metamaterials is developed using Feshbach formalism. It reveals the role played by the electromagnetic modes and material losses in the system, and enables the engineering of Fano resonances in arbitrary geometries. A general formula for the asymmetric resonance in a non-conservative system is derived. The influence of the electromagnetic interactions on the resonance line shape is discussed and it is shown that intrinsic losses drive the resonance contrast, while its width is mostly determined by the coupling strength between the non-radiative mode and the continuum. The analytical model is in perfect agreement with numerical simulations.Comment: 13 pages, 5 figure

Low-energy photoelectron transmission through aerosol overlayers

The transmission of low-energy (<1.8eV) photoelectrons through the shell of core-shell aerosol particles is studied for liquid squalane, squalene, and DEHS shells. The photoelectrons are exclusively formed in the core of the particles by two-photon ionization. The total photoelectron yield recorded as a function of shell thickness (1-80nm) shows a bi-exponential attenuation. For all substances, the damping parameter for shell thicknesses below 15nm lies between 8 and 9nm, and is tentatively assigned to the electron attenuation length at electron kinetic energies of ~0.5-1eV. The significantly larger damping parameters for thick shells (> 20nm) are presumably a consequence of distorted core-shell structures. A first comparison of aerosol and traditional thin film overlayer methods is provided

Tungsten nuclear rocket, phase II, part 1 Final report, Jan. 16 - Jun. 15, 1966

Critical experiments and nuclear analyses of tungsten water moderated nuclear rocket reacto

Near-field enhancement and sub-wavelength imaging in the optical region using a pair of two-dimensional arrays of metal nanospheres

Near-field enhancement and sub-wavelength imaging properties of a system comprising a coupled pair of two-dimensional arrays of resonant nanospheres are studied. The concept of using two coupled material sheets possessing surface mode resonances for evanescent field enhancement is already well established in the microwave region. This paper shows that the same principles can be applied also in the optical region, where the performance of the resonant sheets can be realized with the use of metallic nanoparticles. In this paper we present design of such structures and study the electric field distributions in the image plane of such superlens.Comment: 15 pages, 9 figure

Thermalization via Heat Radiation of an Individual Object Thinner than the Thermal Wavelength

Modeling and investigating the thermalization of microscopic objects with arbitrary shape from first principles is of fundamental interest and may lead to technical applications. Here, we study, over a large temperature range, the thermalization dynamics due to far-field heat radiation of an individual, deterministically produced silica fiber with a predetermined shape and a diameter smaller than the thermal wavelength. The temperature change of the subwavelength-diameter fiber is determined through a measurement of its optical path length in conjunction with an ab initio thermodynamic model of the fiber structure. Our results show excellent agreement with a theoretical model that considers heat radiation as a volumetric effect and takes the emitter shape and size relative to the emission wavelength into account

Varying the effective refractive index to measure optical transport in random media

We introduce a new approach for measuring both the effective medium and the transport properties of light propagation in heterogeneous media. Our method utilizes the conceptual equivalence of frequency variation with a change in the effective index of refraction. Experimentally, we measure intensity correlations via spectrally resolved refractive index tuning, controlling the latter via changes in the ambient pressure. Our experimental results perfectly match a generalized transport theory that incorporates the effective medium and predicts a precise value for the diffusion constant. Thus, we directly confirm the applicability of the effective medium concept in strongly scattering materials.Comment: 5 pages, 5 figure

Multidimensional optical fractionation with holographic verification

The trajectories of colloidal particles driven through a periodic potential energy landscape can become kinetically locked in to directions dictated by the landscape's symmetries. When the landscape is realized with forces exerted by a structured light field, the path a given particle follows has been predicted to depend exquisitely sensitively on such properties as the particle's size and refractive index These predictions, however, have not been tested experimentally. Here, we describe measurements of colloidal silica spheres' transport through arrays of holographic optical traps that use holographic video microscopy to track individual spheres' motions in three dimensions and simultaneously to measure each sphere's radius and refractive index with part-per-thousand resolution. These measurements confirm previously untested predictions for the threshold of kinetically locked-in transport, and demonstrate the ability of optical fractionation to sort colloidal spheres with part-per-thousand resolution on multiple characteristics simultaneously.Comment: 4 pages, 2 figures. Accepted for publication in Physical Review Letter

Epsilons Near Zero limits in the Mie scattering theory

The classical Mie theory - electromagnetic radiation scattering by the homogeneous spherical particles - is considered in the epsilon near zero limits separately for the materials of the particles and the surrounding medium. The maxima of a scattered transverse electrical (TE) field for the surrounding medium materials with the epsilon near zero limits are revealed. The effective multipole polarizabilities of the corresponding scattering particles are investigated. The possibility to achieve magnetic dipole resonance and accordingly to construct metamaterials with negative refractive index for the aggregates spherical particles in surrounding medium with the epsilon near zero limits is considered.Comment: 8 pages, 6 figure

Light trapping and guidance in plasmonic nanocrystals

We illustrate the possibility of light trapping and funneling in periodic arrays of metallic nanoparticles. A controllable minimum in the transmission spectra of such constructs arises from a collective plasmon resonance phenomenon, where an incident plane wave sharply localizes in the vertical direction, remaining delocalized in the direction parallel to the crystal plane. Using hybrid arrays of different structures or different materials, we apply the trapping effect to structure the eigen-mode spectrum, introduce overlapping resonances, and hence direct the light in space in a wavelength-sensitive fashion

Modeling of Isotropic Backward-Wave Materials Composed of Resonant Spheres

A possibility to realize isotropic artificial backward-wave materials is theoretically analyzed. An improved mixing rule for the effective permittivity of a composite material consisting of two sets of resonant dielectric spheres in a homogeneous background is presented. The equations are validated using the Mie theory and numerical simulations. The effect of a statistical distribution of sphere sizes on the increasing of losses in the operating frequency band is discussed and some examples are shown.Comment: 15 pages, 7 figure