Temperature-Dependent Plasmonic Responses from Gold Nanoparticle Dimers Linked by Double-Stranded DNA.
Lermusiaux, L., and S. Bidault.
Langmuir 34, no. 49 (2018): 14946–14953.
Résumé: © 2018 American Chemical Society. DNA is a powerful tool to assemble gold nanoparticles into discrete structures with tunable plasmonic properties for photonic or biomedical applications. Because of their photothermal properties or their use in biological media, these nanostructures can experience drastic modifications of the local temperature that can affect their morphology and, therefore, their optical responses. Using single-nanostructure spectroscopy, we demonstrate that, even with a fully stable DNA linker, gold particle dimers can undergo substantial conformational changes at temperatures larger than 50 °C and aggregate irreversibly. Such temperature-dependent resonant optical properties could find applications in imaging and in the design of nonlinear photothermal sources. Inversely, to provide fully stable DNA-templated plasmonic nanostructures at biologically relevant temperatures, we show how passivating the gold nanoparticles using amphiphilic surface chemistries renders the longitudinal plasmon resonance of gold particle dimers nearly independent of the local temperature.
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Enhancing Magnetic Light Emission with All-Dielectric Optical Nanoantennas.
Sanz-Paz, M., C. Ernandes, J. U. Esparza, G. W. Burr, N. F. Van Hulst, A. Maitre, L. Aigouy, T. Gacoin, N. Bonod, M. F. Garcia-Parajo et al.
Nano Letters 18, no. 6 (2018): 3481–3487.
Résumé: © 2018 American Chemical Society. Electric and magnetic optical fields carry the same amount of energy. Nevertheless, the efficiency with which matter interacts with electric optical fields is commonly accepted to be at least 4 orders of magnitude higher than with magnetic optical fields. Here, we experimentally demonstrate that properly designed photonic nanoantennas can selectively manipulate the magnetic versus electric emission of luminescent nanocrystals. In particular, we show selective enhancement of magnetic emission from trivalent europium-doped nanoparticles in the vicinity of a nanoantenna tailored to exhibit a magnetic resonance. Specifically, by controlling the spatial coupling between emitters and an individual nanoresonator located at the edge of a near-field optical scanning tip, we record with nanoscale precision local distributions of both magnetic and electric radiative local densities of states (LDOS). The map of the radiative LDOS reveals the modification of both the magnetic and electric quantum environments induced by the presence of the nanoantenna. This manipulation and enhancement of magnetic light-matter interaction by means of nanoantennas opens up new possibilities for the research fields of optoelectronics, chiral optics, nonlinear and nano-optics, spintronics, and metamaterials, among others.
Mots-Clés: Dielectric and plasmonic nanoantennas; magnetic and electric LDOS; magnetic dipoles; magnetic light; near-field optical microscopy
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Enhancement and Inhibition of Spontaneous Photon Emission by Resonant Silicon Nanoantennas.
Bouchet, D., M. Mivelle, J. Proust, B. Gallas, I. Ozerov, M. F. Garcia-Parajo, A. Gulinatti, I. Rech, Y. De Wilde, N. Bonod et al.
Physical Review Applied 6, no. 6 (2016).
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All-Dielectric Silicon Nanogap Antennas To Enhance the Fluorescence of Single Molecules.
Regmi, R., J. Berthelot, P. M. Winkler, M. Mivelle, J. Proust, F. Bedu, I. Ozerov, T. Begou, J. Lumeau, H. Rigneault et al.
Nano Letters 16, no. 8 (2016): 5143–5151.
Mots-Clés: All-dielectric nanophotonics; silicon resonators; optical antenna; fluorescence enhancement; Mie scattering
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Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix.
Mounaix, M., D. Andreoli, H. Defienne, G. Volpe, O. Katz, S. Gresillon, and S. Gigan.
Physical Review Letters 116, no. 25 (2016).
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Competition between Förster Resonance Energy Transfer and Donor Photodynamics in Plasmonic Dimer Nanoantennas.
Bidault, S., A. Devilez, P. Ghenuche, B. Stout, N. Bonod, and J. Wenger.
ACS Photonics 3, no. 5 (2016): 895–903.
Résumé: © 2016 American Chemical Society. Plasmonic optical antennas enhance and control the emission of quantum sources in the far-field. Interestingly, the antenna concept can also be applied to enhance the electric field produced by a quantum emitter in the near-field and increase the rate of Förster resonance energy transfer (FRET) between two nearby donor and acceptor dipole emitters. However, plasmonic antennas also influence numerous other photophysical processes such as the donor excitation intensity and decay dynamics and the acceptor emission yield, which compete with the observation of FRET. Understanding the balance between FRET and these processes and monitoring FRET under intense resonant optical confinement in plasmonic nanoantennas have remained challenging open questions. Here, we use DNA-driven self-assembly to accurately produce 40 and 60 nm gold nanoparticle dimer antennas containing a single FRET pair located in the center of a 14 nm gap. The spontaneous donor decay rate constants are increased by 2 orders of magnitude, creating high local densities of optical states (LDOS) to explore the link between LDOS and FRET. The antennas induce a 5-fold increase of Förster energy transfer rate constants associated with reduced transfer efficiencies, in good agreement with numerical simulations. The strong antenna-emitter interaction leads to the surprising association of an enhanced acceptor emission with a weak transfer efficiency. Our measurements exemplify the competition between radiative and nonradiative processes in complex nanophotonic systems and highlight geometrical parameters and design rules to optimize nanoantennas for nonradiative energy harvesting.
Mots-Clés: DNA self-assembly; fluorescence enhancement; FRET; gold nanoparticle; LDOS; nanoantenna; plasmonics
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Picosecond Lifetimes with High Quantum Yields from Single-Photon-Emitting Colloidal Nanostructures at Room Temperature.
Bidault, S., A. Devilez, V. Maillard, L. Lermusiaux, J. - M. Guigner, N. Bonod, and J. Wenger.
Acs Nano 10, no. 4 (2016): 4806–4815.
Mots-Clés: self-assembled nanostructures; plasmon-enhanced fluorescence; single-photon emission; fluorescence correlation spectroscopy; dark-field microscopy
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Fabrication of poly-crystalline Si-based Mie resonators via amorphous Si on SiO 2 dewetting.
Naffouti, M., T. David, A. Benkouider, L. Favre, A. Ronda, I. Berbezier, S. Bidault, N. Bonod, and M. Abbarchi.
Nanoscale 8, no. 5 (2016): 2844–2849.
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Probing Extended Modes on Disordered Plasmonic Networks by Wavefront Shaping.
Bondareff, P., G. Volpe, S. Gigan, and S. Gresillon.
ACS Photonics 2, no. 12 (2015): 1661–1662.
Résumé: © 2015 American Chemical Society. We experimentally study the optical field distribution on disordered plasmonic networks by far-field wavefront shaping. We observe nonlocal fluctuations of the field intensity mediated by plasmonic modes up to a distance of 10 μm from the excitation area. In particular we quantify the spatial extent of these fluctuations as a function of the metal filling fraction in the plasmonic network, and we identify a clear increase around percolation due to the existence of extended plasmonic modes. This paves the way toward far-field coherent control of plasmonic modes on similar disordered plasmonic networks. We expect these results to be relevant for quantum networks, coherent control, and light-matter interactions in such disordered films where long-range interactions are critical.
Mots-Clés: disorder; far-field control; leaky wave microscopy; mode extension; plasmonic networks; surface plasmon; surface wave; wavefront shaping
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Increasing the Morphological Stability of DNA-Templated Nanostructures with Surface Hydrophobicity.
Lermusiaux, L., and S. Bidault.
Small 11, no. 42 (2015): 5696–5704.
Résumé: © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. DNA has been extensively used as a versatile template to assemble inorganic nanoparticles into complex architectures; thanks to its programmability, stability, and long persistence length. But the geometry of self-assembled nanostructures depends on a complex combination of attractive and repulsive forces that can override the shape of a molecular scaffold. In this report, an approach to increase the morphological stability of DNA-templated gold nanoparticle (AuNP) groupings against electrostatic interactions is demonstrated by introducing hydrophobicity on the particle surface. Using single nanostructure spectroscopy, the nanometer-scale distortions of 40 nm diameter AuNP dimers are compared with different hydrophilic, amphiphilic, neutral, and negatively charged surface chemistries, when modifying the local ionic strength. It is observed that, with most ligands, a majority of studied nanostructures deform freely from a stretched geometry to touching particles when increasing the salt concentration while hydrophobicity strongly limits the dimer distortions. Furthermore, an amphiphilic surface chemistry provides DNA-linked AuNP dimers with a high long-term stability against internal aggregation.
Mots-Clés: amphiphilic ligands; darkfield microscopy; DNA nanotechnology; nanostructures; self-assembly
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Deterministic control of broadband light through a multiply scattering medium via the multispectral transmission matrix.
Andreoli, D., G. Volpe, S. Popoff, O. Katz, S. Gresillon, and S. Gigan.
Scientific reports 5 (2015): 10347.
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Widefield spectral monitoring of nanometer distance changes in DNA-templated plasmon rulers.
Lermusiaux, L., V. Maillard, and S. Bidault.
ACS Nano 9, no. 1 (2015): 978–990.
Résumé: © 2015 American Chemical Society. The nanometer-scale sensitivity of electromagnetic plasmon coupling allows the translation of minute morphological changes in nanostructures into macroscopic optical signals. We demonstrate here a widefield spectral analysis of 40 nm diameter gold nanoparticle (AuNP) dimers, linked by a short DNA double strand, using a low-cost color CCD camera and allowing a quantitative estimation of interparticle distances in a 3-20 nm range. This analysis can be extended to lower spacings and a parallel monitoring of dimer orientations by performing a simple polarization analysis. Our measurement approach is calibrated against confocal scattering spectroscopy using AuNP dimers that are distorted from a stretched geometry at low ionic strength to touching particles at high salt concentrations. We then apply it to identify dimers featuring two different conformations of the same DNA template and discuss the parallel colorimetric sensing of short sequence-specific DNA single strands using dynamic plasmon rulers.
Mots-Clés: colorimetric sensing; darkfield microscopy; DNA self-assembly; dynamic nanostructures; plasmon ruler; widefield spectroscopy
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Wafer Scale Formation of Monocrystalline Silicon-Based Mie Resonators via Silicon-on-Insulator Dewetting.
Abbarchi, M., M. Naffouti, B. Vial, A. Benkouider, L. Lermusiaux, L. Favre, A. Ronda, S. Bidault, I. Berbezier, and N. Bonod.
Acs Nano 8, no. 11 (2014): 11181–11190.
Mots-Clés: Mie resonators; thin fim dewetting; all-dielectric nanophotonics; silicon nanoparticles
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Self-Assembled Plasmonic Oligomers for Organic Photovoltaics.
Pastorelli, F., S. Bidault, J. Martorell, and N. Bonod.
Advanced Optical Materials 2, no. 2 (2014): 171–175.
Mots-Clés: organic photovoltaics; plasmonic oligomers; plasmonic solar cells; gold particles
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Selective Excitation of Single Molecules Coupled to the Bright Mode of a Plasmonic Cavity.
Busson, M. P., and S. Bidault.
Nano Letters 14, no. 1 (2014): 284–288.
Mots-Clés: Plasmon coupling; DNA self-assembly; single molecule; Purcell effect; cylindrical vector beam; radial polarization
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Reversible switching of the interparticle distance in DNA-templated gold nanoparticle dimers.
Lermusiaux, L., A. Sereda, B. Portier, E. Larquet, and S. Bidault.
ACS Nano 6, no. 12 (2012): 10992–10998.
Résumé: We produce gold nanoparticle dimers with a surface-to-surface distance that varies reversibly by a factor of 3 when hybridizing or removing a single target DNA strand. The dimers are built on one DNA template that features a stem-loop enabling the interparticle distance change. Using electrophoresis, we reach 90% sample purities and demonstrate that this chemical process is reversible in solution at room temperature for a low molar excess of the target DNA strand. The kinetics of the reaction is asymmetric due to steric hindrance in the stem-loop opening process. Furthermore, a statistical analysis of cryo-electron microscopy measurements allows us to provide the first quantitative analysis of distance changes in chemically switchable nanoparticle assemblies. © 2012 American Chemical Society.
Mots-Clés: cryo-electron microscopy; DNA self-assembly; dynamic nanostructures; electrophoresis; gold nanoparticles; Chemical process; Cryo-electron microscopy; DNA self-assembly; DNA strands; DNA-template; Gold Nanoparticles; Interparticle distances; Molar excess; Nanoparticle assemblies; Opening process; Reversible switching; Room temperature; Stem-loop; Steric hindrances; Surface-to-surface distances; Switchable; Electron microscopes; Electrophoresis; Gold; Metal nanoparticles; Reaction kinetics; DNA; DNA; gold; metal nanoparticle; article; chemistry; dimerization; electrophoresis; Dimerization; DNA; Electrophoresis; Gold; Metal Nanoparticles
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Near-field phase analysis reveals unexpected scattering properties of optical antennas.
Rolly, B., B. Stout, S. Bidault, and N. Bonod.
In 2012 Conference on Lasers and Electro-Optics, CLEO 2012., 2012.
Résumé: We demonstrate that a thorough study of the phase between nearby dipoles offers new insights in the design of nanoantennas and in the integration of dipolar emitters into metallic nanostructures. © 2012 OSA.
Mots-Clés: Metallic nanostructure; Nanoantennas; Near-field; Optical antennas; Phase analysis; Scattering property; Lasers
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Photonic engineering of hybrid metal-organic chromophores.
Busson, M. P., B. Rolly, B. Stout, N. Bonod, J. Wenger, and S. Bidault.
Angewandte Chemie – International Edition 51, no. 44 (2012): 11083–11087.
Résumé: An aureate dye: Confined electromagnetic fields in DNA-templated gold nanoparticle dimers were tuned to engineer the fluorescence properties of organic dyes in water (see picture). Purified suspensions of hybrid metal-organic chromophores featured unprecedented photophysical properties, such as a short lifetime and low quantum yield but high brightness. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mots-Clés: DNA; fluorescence; fluorescence correlation spectroscopy; nanoparticles; self-assembly; Fluorescence Correlation Spectroscopy; Fluorescence properties; Gold Nanoparticles; High brightness; Metal-organic; Organic dye; Photonic engineering; Photophysical properties; DNA; Electromagnetic fields; Fluorescence; Fluorescence spectroscopy; Nanoparticles; Quantum yield; Self assembly; Chromophores; DNA; fluorescent dye; gold; organogold compound; article; chemistry; diffusion; dimerization; optics; solubility; Diffusion; Dimerization; DNA; Fluorescent Dyes; Gold; Optics and Photonics; Organogold Compounds; Solubility
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Accelerated single photon emission from dye molecule-driven nanoantennas assembled on DNA.
Busson, M. P., B. Rolly, B. Stout, N. Bonod, and S. Bidault.
Nature Communications 3 (2012).
Résumé: A photon interacts efficiently with an atom when its frequency corresponds exactly to the energy between two eigenstates. But at the nanoscale, homogeneous and inhomogeneous broadenings strongly hinder the ability of solid-state systems to absorb, scatter or emit light. By compensating the impedance mismatch between visible wavelengths and nanometre-sized objects, optical antennas can enhance light-matter interactions over a broad frequency range. Here we use a DNA template to introduce a single dye molecule in gold particle dimers that act as antennas for light with spontaneous emission rates enhanced by up to two orders of magnitude and single photon emission statistics. Quantitative agreement between measured rate enhancements and theoretical calculations indicate a nanometre control over the emitter-particle position while 10 billion copies of the target geometry are synthesized in parallel. Optical antennas can thus tune efficiently the photo-physical properties of nano-objects by precisely engineering their electromagnetic environment. © 2012 Macmillan Publishers Limited. All rights reserved.
Mots-Clés: atto647n dye; dimer; DNA; fluorescent dye; gold nanoparticle; unclassified drug; coloring agent; nanomaterial; antenna; article; calculation; DNA template; electromagnetic field; energy conversion; energy transfer; fluorescence; geometry; light; light harvesting system; nanoantenna; particle size; photochemistry; photon; bioengineering; chemistry; methodology; nanotechnology; Bioengineering; Coloring Agents; DNA; Nanostructures; Nanotechnology; Photons
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Promoting magnetic dipolar transition in trivalent lanthanide ions with lossless Mie resonances.
Rolly, B., B. Bebey, S. Bidault, B. Stout, and N. Bonod.
Physical Review B – Condensed Matter and Materials Physics 85, no. 24 (2012).
Résumé: Mie resonances in dielectric particles can increase the local optical density of states (LDOS) associated with either electric or magnetic transition rates in nearby quantum emitters without ohmic losses. Their rather large quality factors compensate their low field confinement as compared to the plasmon resonances of metallic nanostructures for which nonradiative decay channels dominate. We show theoretically that near-infrared quadrupolar magnetic resonances in silicon particles can preferentially promote magnetic versus electric radiative deexcitation in trivalent erbium ions at 1.54 μm. The distance dependent interaction between magnetic (electric) dipole emitters and induced magnetic or electric dipoles and quadrupoles is derived analytically and compared to quasiexact full-field calculations based on Mie theory. We discuss how near-field coupling between nearby particles can further enhance the magnetic LDOS and compensate for the weak refractive index contrasts between dielectric particles and a typical host matrix for the lanthanide ions. © 2012 American Physical Society.
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Digital heterodyne holography reveals the non-quasi-static scattering behaviour of transversally coupled nanodisk pairs.
Suck, S. Y., S. Bidault, N. Bonod, S. Collin, N. Bardou, Y. De Wilde, and G. Tessier.
International Journal of Optics 2012 (2012).
Résumé: We reconstruct the full three-dimensional scattering pattern of longitudinal and transverse modes in pairs of coupled gold nanodisks using digital heterodyne holography. Near-field simulations prove that, in our experimental conditions, the induced dipoles in the longitudinal mode are in phase while they are nearly in opposite phase for the transverse mode. The scattering efficiency of the two modes is of the same order of magnitude, which goes against the common belief that antisymmetric transverse modes are dark. The analysis of the reconstructed hologram in the Fourier plane allows us to estimate the angular scattering pattern for both excited modes. In particular, the antisymmetric transverse mode scatters light mostly into one half-plane, demonstrating that the quasi-static approximation breaks down in nanodisk pairs even for an interparticle distance lower than 4. Copyright © 2012 Sarah Y. Suck et al.
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Water-based assembly and purification of plasmon-coupled gold nanoparticle dimers and trimers.
Bidault, S., and A. Polman.
International Journal of Optics 2012 (2012).
Résumé: We describe a simple one-pot water-based scheme to produce gold nanoparticle groupings with short interparticle spacings. This approach combines a cross-linking molecule and a hydrophilic passivation layer to control the level of induced aggregation. Suspensions of dimers and trimers are readily obtained using a single electrophoretic purification step. The final interparticle spacings allow efficient coupling of the particle plasmon modes as verified in extinction spectroscopy. Copyright © 2012 Sébastien Bidault and Albert Polman.
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Optical and topological characterization of gold nanoparticle dimers linked by a single DNA double strand.
Busson, M. P., B. Rolly, B. Stout, N. Bonod, E. Larquet, A. Polman, and S. Bidault.
Nano Letters 11, no. 11 (2011): 5060–5065.
Résumé: We demonstrate that symmetric or asymmetric gold nanoparticle dimers with substantial scattering cross sections and plasmon coupling can be produced with a perfectly controlled chemical environment and a high purity using a single DNA linker as short as 7 nm. A statistical analysis of the optical properties and morphology of single dimers is performed using darkfield and cryo-electron microscopies. These results, correlated to Mie theory calculations, indicate that the particle dimers are stretched in water by electrostatic interactions. © 2011 American Chemical Society.
Mots-Clés: Chemical environment; Cryo-electron microscopy; Dark-field; DNA Double strands; DNA linkers; Gold Nanoparticles; High purity; Mie theory; Plasmon coupling; Scattering cross section; Nanoparticles; Optical properties; Dimers
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On the phase of the electric field in optical antennas.
Rolly, B., B. Stout, S. Bidault, and N. Bonod.
In AIP Conference Proceedings, 88–90. Vol. 1398., 2011.
Résumé: We study the phase of the electric field in the vicinity of two electric dipoles transversely coupled in two fundamental cases: a nanogap antenna illuminated from the far field and a directive antenna made of a single metallic particle coupled to an electric source dipole. We will link the scattering efficiency of the dimer (first case) and the directivity of the particle antenna (second case) to the relative phase of the two dipoles. The strong distance dependence of this phase term produces two unexpected effects: the bonding transverse mode can be the brightest mode of a nanogap antenna; and the emission directivity offered by a metallic particle can be tuned by varying the emitter/particle distance at a strongly sub-wavelength scale. © 2011 American Institute of Physics.
Mots-Clés: electric dipole radiation; light scattering; nano-optics; Nanoantennas; near field; plasmonics
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Crucial role of the emitter-particle distance on the directivity of optical antennas.
Rolly, B., B. Stout, S. Bidault, and N. Bonod.
Optics Letters 36, no. 17 (2011): 3368–3370.
Résumé: We demonstrate that the reflecting properties of a single particle nanoantenna can be extremely sensitive to its distance from a quantum emitter at frequencies lower than the plasmon resonance. The phenomenon is shown to arise from rapid phase variations of the emitter field at short distances associated with a phase of the antenna particle polarizability lower than π/4. © 2011 Optical Society of America.
Mots-Clés: Directivity; Nanoantennas; Optical antennas; Phase variation; Plasmon resonances; Polarizabilities; Short distances; Single particle; Antennas
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Ultracompact and unidirectional metallic antennas.
Bonod, N., A. Devilez, B. Rolly, S. Bidault, and B. Stout.
Physical Review B – Condensed Matter and Materials Physics 82, no. 11 (2010).
Résumé: We investigate the angular redistribution of light radiated by a single emitter located in the vicinity of dipolar silver nanoparticles. We point out the fundamental role of the phase differences introduced by the optical path difference between the emitter and the particle and demonstrate that the polarizability of the metallic nanoparticle alone cannot predict the emission directionality. In particular, we show that collective or reflective properties of single nanoparticles can be controlled by tuning the distance of a single emitter at a λ/30 scale. These results enable us to design unidirectional and ultracompact nanoantennas composed of just two coupled nanoparticles separated by a distance achievable with biological linkers. © 2010 The American Physical Society.
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Nanoparticle for active plasmonic device.
Delahaye, J., S. Gresillon, and E. Fort.
In Proceedings of SPIE – The International Society for Optical Engineering. Vol. 7608., 2010.
Résumé: Active plasmonic devices are much promising for optical devices and circuits at the nanoscale. We show that single nanoparticles coupled to metallic surfaces are good candidates for integrated components with nanometric dimensions. The localized plasmon of the nanoparticle launches propagating surface plasmons in the metallic thin film. Direct particle observation using leaky wave microscope geometry permits easy detection through the interference of the direct transmitted excitation light and the surface plasmon leaky mode. Investigations of the optical response of a nanoparticle deposited on metallic thin metal films reveals unexpectedly high transmission of light associated to contrast inversion in the images. © 2010 Copyright SPIE – The International Society for Optical Engineering.
Mots-Clés: Leaky wave; Metal particle; Microscopy; Plasmon; Polariton; Excitation light; High transmission; Leaky modes; Leaky waves; Metal particle; Metallic surface; Metallic thin films; Nano scale; Nanometric dimensions; Optical response; Plasmon-polaritons; Plasmonic devices; Single nanoparticle; Surface plasmons; Thin metal films; Light transmission; Metallic compounds; Nanoparticles; Nanophotonics; Nanotechnology; Optical data storage; Optical instruments; Phonons; Photons; Quantum theory; Plasmons
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Fluorescence correlation spectroscopy on nano-fakir surfaces.
Delahaye, J., S. Gresillon, S. Lévêque-Fort, N. Sojic, and E. Fort.
In Progress in Biomedical Optics and Imaging – Proceedings of SPIE. Vol. 7571., 2010.
Résumé: Single biomolecule behaviour can reveal crucial information about processes not accessible by ensemble measurements. It thus represents a real biotechnological challenge. Common optical microscopy approaches require pico- to nano-molar concentrations in order to isolate an individual molecule in the observation volume. However, biologically relevant conditions often involve micromolar concentrations, which impose a drastic reduction of the conventional observation volume by at least three orders of magnitude. This confinement is also crucial for mapping sub-wavelength heterogeneities in cells, which play an important role in many biological processes. We propose an original approach, which couples Fluorescence Correlation Spectroscopy (FCS), a powerful tool to retrieve essential information on single molecular behaviour, and nano-fakir substrates with strong field enhancements and confinements at their surface. These electromagnetic singularities at nanometer scale, called “hotspots”, are the result of the unique optical properties of surface plasmons. They provide an elegant means for studying single-molecule dynamics at high concentrations by reducing dramatically the excitation volume and enhancing the fluorophore signal by several orders of magnitude. The nano-fakir substrates used are obtained from etching optical fiber bundles followed by sputtering of a gold thin-film. It allows one to design reproducible arrays of nanotips. © 2010 Copyright SPIE – The International Society for Optical Engineering.
Mots-Clés: Electromagnetic enhancement; Fluorescence correlation spectroscopy; Surface plasmon; Biological process; Electromagnetic enhancement; Fluorescence Correlation Spectroscopy; High concentration; Hotspots; In-cell; Micromolar concentration; Molar concentration; Nano-meter scale; Optical fiber bundle; Orders of magnitude; Single-molecule dynamics; Strong field enhancement; Sub-wavelength; Surface plasmons; Three orders of magnitude; Electromagnetism; Fluorescence; Fluorescence spectroscopy; Molecules; Optical data storage; Optical fibers; Optical microscopy; Plasmons; Optical properties
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Direct observation of locally enhanced electromagnetic field.
Gadenne, P., X. Quelin, S. Ducourtieux, Samuel Gresillon, L. Aigouy, J. - C. Rivoal, V. Shalaev, and A. Sarychev.
Physica B: Condensed Matter 279, no. 1-3 (2000): 52–55.
Résumé: Surface enhanced Raman scattering and other nonlinear enhanced optical effects are well known to be induced by the surface of discontinuous or rough metal thin films. In the percolating range of concentration, theoretical calculations lead to locally enhanced field distributions at the surface of the films, due to huge fluctuations close to the phase transition threshold. Using a scanning near-field optical microscope (SNOM) of extremely high lateral resolution (10 nm), we have been able to record the field distribution close to the surface of discontinuous gold films in both transmission and reflection modes. We report here the direct observations, at a scale much shorter than the wavelength, of the giant field peaks, the so-called `hot spots'. Their intensities and spatial distribution are found in good agreement with the theoretical predictions.
Mots-Clés: Electromagnetic fields; Gold; Light reflection; Light transmission; Optical microscopy; Percolation (solid state); Raman scattering; Thin films; Anderson localization; Scanning near-field optical microscopes (SNOM); Surface enhanced Raman scattering (SERS); Surface plasmon modes; Metallic films
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