110 research outputs found
Electromagnetic forces and torques in nanoparticles irradiated by a plane wave
Optical tweezers and optical lattices are making it possible to control small
particles by means of electromagnetic forces and torques. In this context, a
method is presented in this work to calculate electromagnetic forces and
torques for arbitrarily-shaped objects in the presence of other objects
illuminated by a plane wave. The method is based upon an expansion of the
electromagnetic field in terms of multipoles around each object, which are in
turn used to derive forces and torques analytically. The calculation of
multipole coefficients are obtained numerically by means of the boundary
element method. Results are presented for both spherical and non-spherical
objects.Comment: 5 papges, 2 figure
Electron energy loss and induced photon emission in photonic crystals
The interaction of a fast electron with a photonic crystal is investigated by
solving the Maxwell equations exactly for the external field provided by the
electron in the presence of the crystal. The energy loss is obtained from the
retarding force exerted on the electron by the induced electric field. The
features of the energy loss spectra are shown to be related to the photonic
band structure of the crystal. Two different regimes are discussed: for small
lattice constants relative to the wavelength of the associated electron
excitations , an effective medium theory can be used to describe the
material; however, for the photonic band structure plays an
important role. Special attention is paid to the frequency gap regions in the
latter case.Comment: 12 pages, 7 figure
Electron iduced light emission in photonic crystals
The interaction of a fast electron with a photonic crystal is studied by
solving the Maxwell equations exactly for the external field provided by the
electron in the presence of the crystal. The polarization currents and charges
produced by the passage of the electron give rise to the emission of the
so-called Smith-Purcell radiation. The emitted light probability is obtained by
integrating the Poynting vector over planes parallel to the crystal at a large
distance from the latter. Both reflected and transmitted light components are
analyzed and related to the photonic band structure of the crystal. Emission
spectra are compared with the energy loss probability and also with the
reflectance and transmittance of the crystal.Comment: 9 pages, 3 figures, nano-7/ecoss-21 proceedings, submitted to Surface
Scienc
Plasmonic amplifier of the evanescent field of free electrons
We show experimentally for the first time that free electron evanescent fields can be amplified by a plasmonic nanolayer in much that same way as optical evanescent fields are amplified in the poor-man's super-lens
Magnetic graphene metamaterial
We predict strong magnetic response by graphene split nanorings at THz frequencies allowing to achieve tunable metamaterials with very high (>100) wavelength to unit-cell ratios, not attainable by conventional noble metals
Amplifying free-electron evanescent fields
We show experimentally for the first time that free-electron evanescent fields can be amplified by a plasmonic nanolayer in a manner analogous to the way in which optical fields are amplified in the poor-man's superlens
Light localization in quasi-periodic nano-photonics carpets
In this work we show the formation of quasi-periodic field carpets and strong localization of light in the proximity of a planar quasi-crystal array of nano-holes in metallic screen
Generating Tesla magnetic pulses in plasmonic nanostructures
Bimetallic plasmonic ring resonators illuminated by femtosecond laser pulses generate transient subpicosecond thermoelectric currents and nanoconfined Tesla-scale magnetic fields
Transmission properties of a single metallic slit: From the subwavelength regime to the geometrical-optics limit
In this work we explore the transmission properties of a single slit in a
metallic screen. We analyze the dependence of these properties on both slit
width and angle of incident radiation. We study in detail the crossover between
the subwavelength regime and the geometrical-optics limit. In the subwavelength
regime, resonant transmission linked to the excitation of waveguide resonances
is analyzed. Linewidth of these resonances and their associated electric field
intensities are controlled by just the width of the slit. More complex
transmission spectra appear when the wavelength of light is comparable to the
slit width. Rapid oscillations associated to the emergence of different
propagating modes inside the slit are the main features appearing in this
regime.Comment: Accepted for publication in Phys. Rev.
X-ray photoelectron diffraction study of ultrathin PbTiO3 films
Abstract.: Full hemispherical X-ray photoelectron diffraction (XPD) experiments have been performed to investigate at the atomic level ultrathin epitaxial c-axis oriented PbTiO3 (PTO) films grown on Nb-doped SrTiO3 substrates. Comparison between experiment and theory allows us to identify a preferential ferroelectric polarization state in a 60 Ă
-thick PTO film. Multiple scattering theory based on a cluster-model [ Phys. Rev. B , 075404 (2001)] is used to simulate the experiment
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