1,721,018 research outputs found
Enhancement of Molecular Fluorescence in the UV Spectral Range Using Aluminum Nanoantennas
No full textWe investigate the fluorescence rate of a dipolar emitter coupled to Al nanoparticles of varying shapes and sizes and to dimer nanoantennas in the deep-ultraviolet (UV) spectral range, using the surface integral equation method. In particular, we show that the shape of the Al nanostructures plays a fundamental role in controlling the complex interplay between the excitation rate and the quantum yield in radiative plasmonic systems. In addition, we also investigate the role of the near-field interaction of two coupled Al nanoparticles in enhancing the fluorescence rate of the dipole. This study is important for the engineering of more efficient light-emitting nanostructures in the UV spectral range, such as Al-based material systems or light-emitting fluorophores for biodetection
First-principles nanocircuit model of open electromagnetic resonators
No full textWe derive from first principles a general circuit model for open, frequency dispersive electromagnetic resonators in the full-wave regime. This model extends the concepts of radiation impedance to the polarization current-density modes induced in open resonators by an arbitrary external excitation. Its physics-based elements offer physical insights into the scattering problem and enable efficient modeling of the resonance frequency and associated bandwidth for arbitrary scattering resonances, establishing a powerful platform for the design and optimization of nanophotonic circuits. Our findings offer compelling prospects for electromagnetic scattering and ultrafast nanophotonics, streamlining the analysis and design of nanoresonators with enhanced operational speeds, and outlining a physics-based model of their temporal dynamics
Radiative properties of diffractively-coupled optical nano-antennas with helical geometry
No full textIn this paper, using the rigorous Surface Integral Equation (SIE)
method, we study light scattering by Au nano-helices with geometrical
dimensions comparable to the wavelength of visible light and we
demonstrate that they behave as highly directional nano-antennas with
largely controllable radiation and polarization characteristics in the
optical regime. In particular, we systematically investigate the
radiation properties of helical nano-antennas with realistic Au
dispersion parameters in the visible spectral range, and we establish
general design rules that enable the engineering of directional
scattering with elliptical or circular polarization. Given the realistic
material and geometric parameters used in this work, our findings
provide novel opportunities for the engineering of chiral sensors,
filters, and components for nano-scale antennas with unprecedented beam
forming and polarization capabilities. (C) 2015 Optical Society of
Americ
Cloaking of arbitrarily shaped objects with homogeneous coatings
No full textWe present a theory for the cloaking of arbitrarily shaped objects and demonstrate electromagnetic scattering cancellation through designed homogeneous coatings. First, in the small-particle limit, we expand the dipole moment of a coated object in terms of its resonant modes. By zeroing the numerator of the resulting rational function, we accurately predict the permittivity values of the coating layer that abates the total scattered power. Then, we extend the applicability of the method beyond the small-particle limit, deriving the radiation corrections of the scattering-cancellation permittivity within a perturbation approach. Our method permits the design of invisibility cloaks for irregularly shaped devices such as complex sensors and detectors
Surface integral method for second harmonic generation in metal nanoparticles including both local-surface and nonlocal-bulk sources
No full textWe propose a numerical method, based on surface integral equations (SIE), for evaluating the second harmonic (SH) scattering by metal nanoparticles (NPs) of arbitrary shape, considering both nonlocal-bulk and local-surface SH sources, induced by the electromagnetic field at the fundamental frequency. We demonstrate that the contribution of the nonlocal-bulk sources can be taken into account through equivalent surface electric and magnetic currents. We numerically solve the SIE problem by using the Galerkin method and the Rao-Wilton-Glisson basis functions in the framework of the distribution theory. The accuracy of the proposed method is verified by comparing with the SH-Mie analytical solution. As an example of a complex-shaped particle, we investigate the SH scattering by a triangular nanoprism. This method paves the way for a better understanding of the SH generation process in arbitrarily shaped NPs and can also have a high impact on the design of novel nanoplasmonic devices with enhanced SH emission
A generalized model for the signal propagation along single- and multi-walled carbon nanotubes with arbitrary chirality
No full textThe paper presents a self-consistent semi-classical model describing the electrical behavior of carbon nanotube interconnects. The model deals with the general case of arbitrary chirality and takes rigorously into account the effects of nanotube size and chirality on its electrical parameters. The general model includes as particular cases the models currently used in literature to describe metallic carbon nanotubes with small radius. The analysis of bundles of single-walled and multi-walled carbon nanotubes is carried-out. The model is also used to derive a semi-analytical approximation for the number of equivalent conduction channels in a multi-walled carbon nanotube shell
Near-field calculation for non-spherical nanoparticle arrays in the framework of the T-matrix method
No full textOperative Approach to Quantum Electrodynamics in Dispersive Dielectric Objects Based on a Polarization Modal Expansion
Full text linkIn this paper we deal with the macroscopic electromagnetic response of a
finite size dispersive dielectric object, in unbounded space, in the framework
of quantum electrodynamics using the Heisenberg picture. We apply a Hopfield
type scheme to account for the dispersion and dissipation of the matter. We
provide a general expression of the polarization density field operator as
functions of the initial conditions of the matter field operators and of the
electromagnetic field operators. It is a linear functional whose kernel is a
linear expression of the impulse response of the dielectric object that we
obtain within the framework of classical electrodynamics. The electric field
operator is expressed as a function of the polarization density field operator
by means of the dyadic Green's function for the free space. The statistical
functions of these operators are classical functionals of the statistics of the
initial conditions of the matter field operators and of the electromagnetic
field operators, whose kernels are linear or multilinear expressions of the
impulse response of the dielectric object. We keep the polarization and the
electromagnetic field distinct to enable the treatment of the polarization and
electromagnetic fluctuations on equal footing. We expand the polarization
density field operator in terms of the static longitudinal and transverse modes
of the object to diagonalize the Coulomb and Ampere interaction energy terms of
the Hamiltonian in the Coulomb gauge. We expand the radiation fields in terms
of the transverse plane wave modes of free space. Few static longitudinal and
transverse modes are needed to calculate each element of the impulse response
matrix for dielectric objects with sizes of the order up to
where
is the susceptibility of the dielectric
Theory of coupled plasmon modes and Fano-like resonances in subwavelength metal structures
No full textIn this paper, we develop a quasielectrostatic theory describing the coupling of plasmon modes and we discuss its implications for the analysis and the design of the scattering and absorption spectra of complex metal nanostructures. In particular, we show that the interaction of bright plasmon modes determines the onset of zeros in the scattering spectra of nanoscale coupled systems. Under well-defined conditions, these zeros give rise to asymmetric scattering line shapes similar to the spectral signatures described by Ugo Fano in the context of atomic physics. We provide rigorous conditions in which Fano-like resonances occur, and we introduce a method for the direct calculation of their spectral position. In addition, we investigate the role of dark and bright modes in the power absorption near a Fano-like resonance. Our analysis demonstrates the quasielectrostatic origin of Fano-like resonances in subwavelength plasmonic structures
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