331 research outputs found
Molecule Non-Radiative Coupling to a Metallic Nanosphere: An Optical Theorem Treatment
The non-radiative coupling of a molecule to a metallic spherical particle is approximated by a sum involving particle quasistatic polarizabilities. We demonstrate that energy transfer from molecule to particle satisfies the optical theorem if size effects corrections are properly introduced into the quasistatic polarizabilities. We hope that this simplified model gives valuable information on the coupling mechanism between molecule and metallic nanos-tructures available for, e.g., surface enhanced spectroscopy signal analysis
Mie plasmons: modes volumes, quality factors and coupling strengths (Purcell factor) to a dipolar emitter
Using either quasi-static approximation or exact Mie expansion, we
characterize the localized surface plasmons supported by a metallic spherical
nanoparticle. We estimate the quality factor and define the effective
volume of the mode in a such a way that coupling strength with a
neighbouring dipolar emitter is proportional to the ratio (Purcell
factor). The role of Joule losses, far-field scattering and mode confinement in
the coupling mechanism are introduced and discussed with simple physical
understanding, with particular attention paid to energy conservation.Comment: (in press) International Journal of Optics (2011
Purcell factor for point-like dipolar emitter coupling to 2D-plasmonic waveguides
We theoretically investigate the spontaneous emission of a point--like
dipolar emitter located near a two--dimensional (2D) plasmonic waveguide of
arbitrary form. We invoke an explicite link with the density of modes of the
waveguide describing the electromagnetic channels into which the emitter can
couple. We obtain a closed form expression for the coupling to propagative
plasmon, extending thus the Purcell factor to plasmonic configurations.
Radiative and non-radiative contributions to the spontaneous emission are also
discussed in details
Near-field properties of plasmonic nanostructures with high aspect ratio
Using the Green's dyad technique based on cuboidal meshing, we compute the
electromagnetic field scattered by metal nanorods with high aspect ratio. We
investigate the effect of the meshing shape on the numerical simulations. We
observe that discretizing the object with cells with aspect ratios similar to
the object's aspect ratio improves the computations, without degrading the
convergency. We also compare our numerical simulations to finite element method
and discuss further possible improvements
Mode-selective quantization and multimodal effective models for spherically layered systems
We propose a geometry-specific, mode-selective quantization scheme in coupled
field-emitter systems which makes it easy to include material and geometrical
properties, intrinsic losses as well as the positions of an arbitrary number of
quantum emitters. The method is presented through the example of a spherically
symmetric, non-magnetic, arbitrarily layered system. We follow it up by a
framework to project the system on simpler, effective cavity QED models.
Maintaining a well-defined connection to the original quantization, we derive
the emerging effective quantities from the full, mode-selective model in a
mathematically consistent way. We discuss the uses and limitations of these
effective models
Pre-determining the location of electromigrated gaps by nonlinear optical imaging
In this paper we describe a nonlinear imaging method employed to spatially
map the occurrence of constrictions occurring on an electrically-stressed gold
nanowire. The approach consists at measuring the influence of a tightly focused
ultrafast pulsed laser on the electronic transport in the nanowire. We found
that structural defects distributed along the nanowire are efficient nonlinear
optical sources of radiation and that the differential conductance is
significantly decreased when the laser is incident on such electrically-induced
morphological changes. This imaging technique is applied to pre-determined the
location of the electrical failure before it occurs.Comment: 3 figure
Molecular quenching and relaxation in a plasmonic tunable system
Molecular fluorescence decay is significantly modified when the emitting molecule is located near a plasmonic structure. When the lateral sizes of such structures are reduced to nanometer-scale cross sections, they can be used to accurately control and amplify the emission rate. In this Rapid Communication, we extend Green's dyadic method to quantitatively investigate both radiative and nonradiative decay channels experienced by a single fluorescent molecule confined in an adjustable dielectric-metal nanogap. The technique produces data in excellent agreement with current experimental work
- âŠ