A. Bouhelier

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.

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.

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

Excitation of surface plasmon polaritons guided mode by Rhodamine B molecules doped in a PMMA stripe.

In this Letter we show the inclusion of Rhodamine B molecules inside a dielectric-loaded surface plasmon waveguide that enables for a precise determination of its optical characteristics. The principle relies on the coupling of the fluorescence emission of the dye to plasmonic waveguided modes allowed in of the structure. Using leakage radiation microscopy in real and reciprocal spaces, we measure the propagation constant of the mode and as well as its attenuation length.

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.

Thermo-electric detection of waveguided surface plasmon propagation

The thermo-electric detection of a waveguided surface plasmon traveling along one electrode of an in-plane integrated thermocouple is demonstrated. By using a particular design of the thermocouple, the thermo-electric signal due to the losses of the plasmon mode can be separated from the non-resonant heating of the waveguide. The thermo-electric signal associated with the plasmon propagation is proportional to the power coupled into the waveguided mode and exhibits a maximum at a distance from the excitation site depending on both the heat transfer coefficient of the system and the plasmon mode damping distance.

Momentum-space spectroscopy for advanced analysis of dielectric-loaded surface plasmon polariton coupled and bent waveguides

We perform advanced radiation leakage microscopy of routing dielectric-loaded plasmonic waveguiding structures. By direct plane imaging and momentum-space spectroscopy, we analyze the energy transfer between coupled waveguides as a function of gap distance and reveal the momentum distribution of curved geometries. Specifically, we observed a clear degeneracy lift of the effective indices for strongly interacting waveguides in agreement with coupled-mode theory. We use momentum-space representations to discuss the effect of curvature on dielectric-loaded waveguides. The experimental images are successfully reproduced by a numerical and an analytical model of the mode propagating in a curved plasmonic waveguide.