G. Colas des Francs

Surface plasmon interference excited by tightly focused laser beams.

We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons.

Polymer-metal waveguides characterization by Fourier plane leakage radiation microscopy

The guiding properties of polymer waveguides on a thin gold film are investigated in the optical regime. The details of propagation in the waveguides are studied simultaneously in the object and Fourier planes, providing direct measurement of both the real and imaginary parts of the effective index of the guided mode. A fair agreement between theoretical analysis provided by the differential method and experimental leakage radiation microscopy data is shown. All these tools bring valuable information for designing and understanding such devices.

Dielectric-loaded surface plasmon polariton waveguides on a finite-width metal strip

We investigate the guiding properties of a dielectric-loaded surface plasmon polariton waveguide on a finite-width metal strip. The guided mode is characterized by leakage radiation microscopy for different metal strip widths. We show a strong mode attenuation for metal strip widths below 1.75 μm at telecom wavelength λ=1.55 μm. We estimate the minimal width using numerical methods and propose an original interpretation. Good agreement with the measured data is achieved. The determination of this critical width is a prerequisite for designing miniaturized plasmonics devices.

Coupling distance between Eu3+ emitters and Ag nanoparticles

Emission by rare earth emitters has been experimentally investigated based on their position relative to metallic nanoparticles by using Ag/Y2O3/Eu:Y2O3/Y2O3/Ag multilayer samples on- or off-plasmon resonance. Comparison with simple models revealed two different coupling regimes at short and long distances. The optimal coupling distance was determined.

Optical gain, spontaneous and stimulated emission of surface plasmon polaritons in confined plasmonic waveguide.

We develop a theoretical model to compute the local density of states in a confined plasmonic waveguide. Based on this model, we derive a simple formula with a clear physical interpretation for the lifetime modification of emitters embedded in the waveguide. The gain distribution within the active medium is then computed following the formalism developed in a recent work [Phys. Rev. B 78, 161401 (2008)], by taking rigorously into account the pump irradiance and emitters lifetime modifications in the system. We finally apply this formalism to describe gain-assisted propagation in a dielectric-loaded surface plasmon polariton waveguide.

Metal enhanced fluorescence in rare earth doped plasmonic core-shell nanoparticles

We theoretically and numerically investigate metal enhanced fluorescence of plasmonic core-shell nanoparticles doped with rare earth (RE) ions. Particle shape and size are engineered to maximize the average enhancement factor (AEF) of the overall doped shell. We show that the highest enhancement (11 in the visible and 7 in the near-infrared) is achieved by tuning either the dipolar or the quadrupolar particle resonance to the rare earth ions excitation wavelength. Additionally, the calculated AEFs are compared to experimental data reported in the literature, obtained in similar conditions (plasmon mediated enhancement) or when a metal-RE energy transfer mechanism is involved.

Leakage radiation microscopy of surface plasmon coupled emission: investigation of gain‐assisted propagation in an integrated plasmonic waveguide

Using a single‐mode dielectric‐loaded surface plasmon polariton waveguide doped with quantum dots, we were able to slightly increase the propagation length of the mode by stimulated emission of plasmon. We analyse the amplification phenomenon in the visible range by combining leakage radiation microscopy and surface plasmon coupled emission techniques.

Purcell factor for a point-like dipolar emitter coupled to a two-dimensional plasmonic waveguide

(Received 1 June 2011; published 11 August 2011)We theoretically investigate the spontaneous emission of a point-like dipolar emitter located near a two-dimensional plasmonic waveguide of arbitrary form. We invoke an explicit link with the density of modes of thewaveguide describing the electromagnetic channels into which the emitter can couple. We obtain a closed formexpressionforthecouplingtopropagativeplasmon,extendingthusthePurcellfactortoplasmonicconfigurations.Radiative and nonradiative contributions to the spontaneous emission are also discussed in detail.DOI: 10.1103/PhysRevB.84.073403 PACS number(s): 42

Resonance quality, radiative/ohmic losses and modal volume of Mie plasmons

Molecular sytems are efficiently coupled to metal nanoparticles via the excitation of localized surface plasmons-polaritons (SPPs). The coupling strength between SPP and emitters can be estimated from the ratio Q/V where Q and V refer to the mode quality factor and effective volume, respectively. In this letter, we investigate in details the properties of Mie plasmons supported by a metallic nanosphere (Q-factor, radiative and ohmic losses, modal volume). We particularly focus on the difficulty to unambiguously define the modal volumes of localized SPPs. This leads us to propose two definitions; the first one is based on Purcell factor for a dipolar emitter in close proximity to the metallic nanoparticle and the second one is adapted from cavity quantum electrodynamics concept (cQED). This work brings simple hand tools to characterize the main properties of localized SPPs and will be helpful in designing optical nanosources. It also makes a bridge between cQED and quantum plasmonics.

High-resolution mapping of the optical near-field components at a triangular nano-aperture

A triangular nano-aperture in an aluminum film was used as a probe in a scanning near-field optical microscope (SNOM) to image single fluorescent molecules with an optical resolution down to 30 nm. The differently oriented molecules were employed as point detectors to map the vectorial components of the electric field distribution at the illuminated triangular aperture. The good agreement of the experimental results with numerical simulations enabled us to determine both the field map at a triangular aperture and the exact orientations of the probing molecules.