Thomas W. Ebbesen

University of Strasbourg, Strasburg, Alsace, France

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Publications (224)1480.27 Total impact

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    ABSTRACT: Organic semiconductors have generated considerable interest for their potential for creating inexpensive and flexible devices easily processed on a large scale. However technological applications are currently limited by the low mobility of the charge carriers associated with the disorder in these materials. Much effort over the past decades has therefore been focused on optimizing the organisation of the material or the devices to improve carrier mobility between molecules or molecular units. Here we take a radically different path to solving this problem, namely by injecting carriers into hybrid light-matter, or polaritonic, states. These are coherent states that can extend over as many as 10e5 molecules or molecular units which should thereby favour organic conductivity. To test this idea, organic semiconductors were strongly coupled to the vacuum electromagnetic field on plasmonic structures to form polaritonic states with large Rabi splittings ~ 0.7 eV. Conductivity experiments show that indeed the current does increase by an order of magnitude at resonance in the coupled state, reflecting mostly a change in mobility as revealed when the structure is gated in a transistor configuration. In practice, polaritonic conductivity is easy to implement and we therefore expect that it will be used to improve organic devices. More broadly our findings illustrate the potential of engineering the vacuum electromagnetic environment to modify and to improve properties of materials.
    09/2014;
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    ABSTRACT: The hysteresis and dynamics of the phase transition of the perovskite salt [Pb(ii)I4(2-),(C12H25NH3(+))2] is shown to be significantly modified when strongly coupled to the vacuum field inside a micro-cavity. The transition barrier is increased and the hysteresis loop is enlarged, demonstrating the potential of controlling the electromagnetic environment of a material.
    Nanoscale 06/2014; · 6.23 Impact Factor
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    ABSTRACT: The efficiency of light-matter strong coupling is tuned by precisely varying the spatial position of a thin layer of cyanine dye J-aggregates in Fabry–Perot microcavities, and their photophysical properties are determined. Placing the layer at the cavity field maximum affords an interaction energy (Rabi splitting) of 503 meV, a 62% increase over that observed if the aggregates are simply spread evenly through the cavity, placing the system in the ultrastrong coupling regime. The fluorescence quantum yield of the lowest polaritonic state P– integrated over k-space is found to be 10–2. The same value can be deduced from the 1.4 ps lifetime of P– measured by femtosecond transient absorption spectroscopy and the calculated radiative decay rate constant. Thus, the polariton decay is dominated by nonradiative processes, in contrast with what might be expected from the small effective mass of the polaritons. These findings provide a deeper understanding of hybrid light-molecule states and have implications for the modification of molecular and material properties by strong coupling.
    Journal of Physical Chemistry Letters 04/2014; 5(8):1433–1439. · 6.59 Impact Factor
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    ABSTRACT: We investigate experimentally the parameter space defining, in the visible range, the far-field diffraction properties of a single circular subwavelength aperture surrounded by periodic circular grooves milled on a metallic film. Diffraction patterns emerging from such an antenna are recorded under parallel- and perpendicular-polarized illumination at a given illumination wavelength. By monitoring the directivity and the gain of the antenna with respect to a single aperture, we point out the role played by the near-field surface plasmon excitations. The results can be analyzed through a Huygens–Fresnel model, accounting for the coherent interaction between the field radiated by the hole and the plasmonic field, propagating along the antenna surface and diffracted away in free space.
    ACS Photonics. 03/2014; 1(4):365–370.
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    ABSTRACT: Strong coupling is at the heart of optomechanics where it enables coherent quantum state transfer between light and micromechanical oscillators. Strongly coupled molecule-cavity systems have also revealed unique properties enabling even the control of chemical rates through the optical hybridization of the electronic states. Here we combine these notions to show that molecular vibrational modes of the electronic ground state can be coherently coupled with a micro-cavity mode at room temperature, given the low vibrational thermal occupation factors n_{\nu}~10^(-4) associated with molecular vibrations, and the collective coupling of a large ensemble of N molecules immersed within the cavity mode volume. This enables the enhancement of the Rabi-exchange rate {\Omega}=N^(1/2){\Omega}_0 with respect to the single oscillator coupling {\Omega}_0. Our results have consequences for chemistry, both hot and cold. Simultaneously, such coupled molecular oscillators could provide a template for an alternative approach to quantum optomechanics.
    03/2014;
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    ABSTRACT: We demonstrate experimentally how the local anisotropy of the dispersion relation of surface plasmon modes propagating over periodic metal gratings can lead to an enhancement of the figure of merit of refractive index sensors. Exploiting the possibility to acquire defocused images of the Fourier space of a highly stable leakage radiation microscope, we report a twofold increase in sensing sensitivity close to the band gap of a one-dimensional plasmonic crystal where the anisotropy of the band structure is the most important. A practical sensing resolution of O(10−6) refractive index units is demonstrated.
    Applied Physics Letters 01/2014; 104(25):251111-251111-4. · 3.79 Impact Factor
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    ABSTRACT: The thermodynamics of strong coupling between molecules and the vacuum field is analyzed and the Gibbs free energy, the enthalpy, and entropy of the coupling process are determined for the first time. The thermodynamic parameters are a function of the Rabi splitting and the microscopic solvation. The results provide a new framework for understanding light-molecule strong coupling.
    Angewandte Chemie International Edition 08/2013; · 11.34 Impact Factor
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    ABSTRACT: We exploit plasmonic and thermo-hydrodynamical forces to sort gold nanoparticles in a microfluidic environment. In the appropriate regime, the experimental data extracted from a Brownian statistical analysis of the kinetic motions are in good agreement with Mie-type theoretical evaluations of the optical forces acting on the nanoparticles in the plasmonic near field. This analysis enables us to demonstrate the importance of thermal and hydrodynamical effects in a sorting perspective. Key words: Optical sorting, metallic nanoparticles, Mie theory, thermo-hydrodynamical forces, plasmofluidics, Brownian motion.
    Nano Letters 08/2013; · 13.03 Impact Factor
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    ABSTRACT: Strongly coupled organic systems are characterized by unusually large Rabi splittings and long-lived polariton states. Here we build up a new theoretical framework to understand the dynamics of such coupled system. In particular, we show that vibrational relaxation inherent to organic materials is intrinsically non-Markovian and thus explain the otherwise counter-intuitive feature of a lifetime of the lower polariton state longer than for all other excited states.
    07/2013;
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    ABSTRACT: Optical forces take on a specific form when involving chiral light fields interacting with chiral objects. We show that optical chirality density and flow can have mechanical effects through reactive and dissipative components of chiral forces exerted on chiral dipoles. Remarkably, these force components are directly related to standard observables: optical rotation and circular dichroism, respectively. As a consequence, resulting forces and torques are dependent on the enantiomeric form of the chiral dipole. This leads to promising strategies for the mechanical separation of chiral objects using chiral light forces.
    New Journal of Physics 06/2013; · 4.06 Impact Factor
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    ABSTRACT: We calculate the optical force and torque applied to an electric dipole by a spinning light field. We prove that the dissipative part of the force depends on the orbital energy flow of the field only, while the spin energy flow is involved in the applied torque. The resulting change in the optical force is detailed for different experimentally relevant configurations, and we show in particular how this change is critical when surface plasmon modes are involved.
    Physical Review A 06/2013; 88(3). · 3.04 Impact Factor
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    ABSTRACT: The strong coupling of porphyrin J-aggregates to plasmonic nanostructures of different symmetry is investigated. The nanostructures of higher symmetry show the strongest interaction with the molecular layer, suggesting that surface plasmon mode degeneracy plays an important role in the coupling efficiency. At high coupling strengths a new, weakly dispersive mode appears which has recently been predicted theoretically to be due to long-range energy transfer between molecules mediated by surface plasmons. These findings point to new ways for optimizing strong coupling and thereby realize its full potential for molecular and material science.
    ChemPhysChem 04/2013; · 3.35 Impact Factor
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    ABSTRACT: The tuning of the molecular material work-function via strong coupling with vacuum electromagnetic fields is demonstrated. Kelvin probe microscopy extracts the surface potential (SP) changes of a photochromic molecular film on plasmonic hole arrays and inside Fabry-Perot cavities. Modulating the optical cavity resonance or the photochromic film effectively tunes the work-function, suggesting a new tool for tailoring material properties.
    Advanced Materials 03/2013; · 14.83 Impact Factor
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    ABSTRACT: We demonstrate that nanostructures carefully designed on both sides of a thin suspended metallic membrane couple light into a chiral near field and transmit vortex beams through a central aperture that connects the two sides of the membrane. We show how far-field orbital angular momentum (OAM) indices can be tailored through nanostructure designs. We reveal the crucial importance of OAM selection rules imposed by the central aperture and derive OAM summation rules in perfect agreement with experimental data.
    Physical Review Letters 02/2013; 110(20). · 7.73 Impact Factor
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    ABSTRACT: We present a comprehensive experimental study of the photophysical properties of a molecule-cavity system under strong coupling conditions, using steady-state and femtosecond time-resolved emission and absorption techniques to selectively excite the lower and upper polaritons as well as the reservoir of uncoupled molecules. Our results demonstrate the complex decay routes in such hybrid systems and that, contrary to expectations, the lower polariton is intrinsically long-lived.
    ChemPhysChem 12/2012; · 3.35 Impact Factor
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    ABSTRACT: The excitation of surface plasmons on an elliptical grating followed by the transmission through a subwavelength aperture can modify the polarization state of the incoming light. The combined effect of the elliptical grooves and a slightly elliptical central hole allows to fully control the birefringence and retardation of the structure, providing a simple approach for polarization state design by the geometry of the structure. From this combination, a perfect plasmonic quarter-wave plate is obtained.
    Applied Physics Letters 11/2012; 101(20). · 3.79 Impact Factor
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    ABSTRACT: Fluorescence spectroscopy is widely used to probe the electromagnetic intensity amplification on optical antennas, yet measuring the excitation intensity amplification is a challenge, as the detected fluorescence signal is an intricate combination of excitation and emission. Here, we describe a novel approach to quantify the electromagnetic amplification in aperture antennas by taking advantage of the intrinsic non linear properties of the fluorescence process. Experimental measurements of the fundamental f and second harmonic 2f amplitudes of the fluorescence signal upon excitation modulation are used to quantify the electromagnetic intensity amplification with plasmonic aperture antennas.
    Optics Express 07/2012; 20(16):18085-90. · 3.55 Impact Factor
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    ABSTRACT: Photonic crystals (PC) have demonstrated unique features that have renewed the fields of classical and quantum optics. Although holding great promises, associated mechanical effects have proven challenging to observe. We demonstrate for the first time that one of the most salient properties of PC, namely negative refraction, can induce specific forces on metal nanoparticles. By integrating a periodically patterned metal film in a fluidic cell, we show that near-field optical forces associated with negatively refracted surface plasmons are capable of controlling particle trajectories. Coupling particle motions to PC band structures draws new approaches and strategies for parallel and high resolution all-optical control of particle flows with applications for micro- and nanofluidic systems.
    Nano Letters 07/2012; 12(8):4329-32. · 13.03 Impact Factor
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    ABSTRACT: We investigate both experimentally and theoretically the far-field diffraction patterns of single circular apertures as a function of their diameters d and at a given illumination wavelength λ. We observe the transition between the well-known pseudoscalar regime of large holes (d≫λ) and the less-known vectorial regime of subwavelength ones (d≪λ). Four different diffraction regimes are identified for different d/λ regions, each one with its polarization dependence. A thorough comparison with a theoretical model, which takes into account both finite hole size and the dielectric properties of the metal, allows us to explain and understand the physical processes leading to this behavior. Our results reveal the subtle interplay between two competing factors, one related to polarization symmetries associated with surface-plasmon excitations and the other originating in the coupling of the field to the waveguide mode of the aperture.
    Physical Review Letters 07/2012; 109(2):023901. · 7.73 Impact Factor
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    ABSTRACT: We examine, both experimentally and theoretically, an interaction of tightly focused polarized light with a slit on a metal surface supporting plasmon-polariton modes. Remarkably, this simple system can be highly sensitive to the polarization of the incident light and offers a perfect quantum weak measurement tool with a built-in postselection in the plasmon-polariton mode. We observe the plasmonic spin Hall effect in both coordinate and momentum spaces which is interpreted as weak measurements of the helicity of light with real and imaginary weak values determined by the input polarization. Our experiment combines the advantages of (i) quantum weak measurements, (ii) near-field plasmonic systems, and (iii) high-numerical aperture microscopy in employing the spin-orbit interaction of light and probing light chirality.
    Physical Review Letters 07/2012; 109(1):013901. · 7.73 Impact Factor

Publication Stats

19k Citations
1,480.27 Total Impact Points

Institutions

  • 2001–2014
    • University of Strasbourg
      • Institut de science et d'ingénierie supramoléculaires (ISIS)
      Strasburg, Alsace, France
  • 2013
    • Weizmann Institute of Science
      Israel
  • 2005–2013
    • French National Centre for Scientific Research
      • Institut Fresnel
      Lutetia Parisorum, Île-de-France, France
  • 2012
    • University of Southern Denmark
      • Department of Technology and Innovation
      Copenhagen, Capital Region, Denmark
    • Tel Aviv University
      Tell Afif, Tel Aviv, Israel
  • 2011
    • Ecole Centrale Marseille
      Marsiglia, Provence-Alpes-Côte d'Azur, France
    • Karl-Franzens-Universität Graz
      • Institute of Physics
      Graz, Styria, Austria
  • 2007–2011
    • Aix-Marseille Université
      • Institut Fresnel (UMR 7249 FRESNEL)
      Marseille, Provence-Alpes-Cote d'Azur, France
    • Technische Universität Dortmund
      • Chair of Experimental Physics II
      Dortmund, North Rhine-Westphalia, Germany
  • 2001–2011
    • University of Zaragoza
      • Departamento de Física de la Materia Condensada
      Zaragoza, Aragon, Spain
  • 2005–2010
    • Aalborg University
      • Department of Physics and Nanotechnology
      Aalborg, Region North Jutland, Denmark
  • 2006
    • University of Notre Dame
      South Bend, Indiana, United States
  • 2004
    • Tokyo Institute of Technology
      Edo, Tōkyō, Japan
  • 2003–2004
    • University of Exeter
      Exeter, England, United Kingdom
    • Universidad Autónoma de Madrid
      • Department of Condensed Matter Physics
      Madrid, Madrid, Spain
  • 2002
    • Rensselaer Polytechnic Institute
      • Department of Materials Science and Engineering
      New York City, NY, United States