Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

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Plasmonics: Fundamentals and Applications

The unprecedented ability of nanometallic (that is, plasmonic) structures to concentrate light into deep-subwavelength volumes has propelled their use in a vast array of nanophotonics technologies and research endeavours. Plasmonic light concentrators can elegantly interface diffraction-limited dielectric optical components with nanophotonic structures. Passive and active plasmonic devices provide new pathways to generate, guide, modulate and detect light with structures that are similar in size to state-of-the-art electronic devices. With the ability to produce highly confined optical fields, the conventional rules for light-matter interactions need to be re-examined, and researchers are venturing into new regimes of optical physics. In this review we will discuss the basic concepts behind plasmonics-enabled light concentration and manipulation, make an attempt to capture the wide range of activities and excitement in this area, and speculate on possible future directions.

/pdf/plasmonics-for-extreme-light-concentration-and-manipulation-25m55spiva.pdf

Plasmonics for extreme light concentration and manipulation.

Cell membranes display a tremendous complexity of lipids and proteins designed to perform the functions cells require. To coordinate these functions, the membrane is able to laterally segregate its constituents. This capability is based on dynamic liquid-liquid immiscibility and underlies the raft concept of membrane subcompartmentalization. Lipid rafts are fluctuating nanoscale assemblies of sphingolipid, cholesterol, and proteins that can be stabilized to coalesce, forming platforms that function in membrane signaling and trafficking. Here we review the evidence for how this principle combines the potential for sphingolipid-cholesterol self-assembly with protein specificity to selectively focus membrane bioactivity.

/pdf/lipid-rafts-as-a-membrane-organizing-principle-3mxewaemed.pdf

Lipid Rafts As a Membrane-Organizing Principle

We present single-molecule, real-time sequencing data obtained from a DNA polymerase performing uninterrupted template-directed synthesis using four distinguishable fluorescently labeled deoxyribonucleoside triphosphates (dNTPs). We detected the temporal order of their enzymatic incorporation into a growing DNA strand with zero-mode waveguide nanostructure arrays, which provide optical observation volume confinement and enable parallel, simultaneous detection of thousands of single-molecule sequencing reactions. Conjugation of fluorophores to the terminal phosphate moiety of the dNTPs allows continuous observation of DNA synthesis over thousands of bases without steric hindrance. The data report directly on polymerase dynamics, revealing distinct polymerization states and pause sites corresponding to DNA secondary structure. Sequence data were aligned with the known reference sequence to assay biophysical parameters of polymerization for each template position. Consensus sequences were generated from the single-molecule reads at 15-fold coverage, showing a median accuracy of 99.3%, with no systematic error beyond fluorophore-dependent error rates.

/pdf/real-time-dna-sequencing-from-single-polymerase-molecules-3o0n2kc430.pdf

Real-Time DNA Sequencing from Single Polymerase Molecules

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

We present and model a dark-field illumination scheme for coherent anti-Stokes Raman scattering (DF-CARS) that highlights the interfaces of an object with chemical sensitivity. The proposed DF-CARS scheme uses dedicated arrangements of the pump kp1, Stokes kS and probe kp2 beams’ k-wave-vectors to address the sample’s interfaces along the x, y or z axis. The arrangements of the incident k-wave-vectors are derived from the Ewald sphere representation of the outgoing anti-Stokes radiation and the effective CARS excitation wave-vector keff = kp1 + kp2 − kS under the intention to avoid probing the object frequency K(0,0,0), i.e., the contribution of a homogeneous sample (dark-field configuration). We suggest a possible experimental realization using simple masks placed in the back pupil of the excitation microscope objective lens. Applying a full vectorial model, the proposed experimental implementation is numerically investigated on grounds of the Debye-Wolff integral and dynadic Green function to confirm the predicted chemical interface contrast.

Laser scanning dark-field coherent anti-Stokes Raman scattering (DF-CARS): a numerical study

In vivo quantitative molecular absorption of glycerol in human skin using coherent anti-Stokes Raman scattering (CARS) and two-photon auto-fluorescence (Conference Presentation)

Amyloid fibrils are proteins misfolding structures that involve a beta-sheet structure and are associated with the pathologies of various neurodegenerative diseases. We show that Thioflavine-T and Congo Red, two major dyes used to image fibrils by fluorescence assays, can provide deep structural information when probed by means of polarization resolved fluorescence microscopy [1]. This technique allows indeed to retrieve simultaneously both mean orientation and orientation dispersion of the dye, used here as a reporter of the fibril structure [2].

Polymorphism of amyloid fibrils monitored by polarization resolved microscopy

Probing molecular order of lipid reporters di-8-ANEPQ in cell plasma membrane by fluorescence polarimetry imaging

L'architecture et la dynamique des molecules formant la membrane cellulaire sont des elements-cles de la comprehension des mecanismes qui gouvernent l'activite cellulaire. Des resultats recents dans notre equipe [1] ont montre que la spectroscopie de correlation de fluorescence (FCS) etait une approche pertinente dans ce contexte. Elle a permis notamment de quantifier in-vivo des structures membranaires [2], mesure inaccessible en microscopie conventionnelle. Nous proposons d'etendre cette technique a l'etude spatio-temporelle de la cellule au cours d'un evenement de signalisation. Dans un tel etat transitoire, il est raisonnable de penser que la perturbation apportee ne sera pas distribuee uniformement sur l'ensemble de la cellule mais localisee initialement aux regions activees, pour ensuite cheminer progressivement vers le noyau. Aussi, afin de garantir la meilleure description tant spatiale que temporelle, la nouvelle experience que nous developpons utilise deux points de mesure independants pouvant etre positionnes arbitrairement par l'experimentateur dans la cellule a etudier. Ces deux points peuvent etre utilises soit pour mener deux mesures distantes simultanees, soit pour etudier les correlations temporelles entre regions cellulaires voisines. Nous presentons une serie complete de procedures permettant de mesurer en temps reel les positions relatives de ces deux points, parametre cle de notre methode. Dans, le plan, une methode d'imagerie reciproque permet de mesurer les positions avec une precision de l'ordre de 50 nm. En profondeur, une procedure automatique de balayage longitudinal permet, a meme l'echantillon, de mesurer des differences de profondeur a 500 nm pres. En definitive, l'espace total accessible par les deux points de mesure, couvre plusieurs dizaines de microns dans le plan et une dizaine de microns en profondeur. Sur ces dimensions compatibles avec les echelles cellulaires, des mesures de FCS en solution ont confirme la bonne homogeneite des conditions de mesure (volume confocal et taux de comptage par molecule). Differents modes de balayages sont en outre possibles pour chaque point de mesure, permettant de completer les mesures ponctuelles par l'acquisition d'images ou de signaux mesures sur des trajectoires arbitraires. Actuellement equipee d'un laser continu, l'experience accueillera prochainement un laser impulsionnel Sa :Ti accordable, qui permettra, par excitation a deux photons, d'etendre la gamme de marqueurs fluorescents accessibles, et donnera acces a des nouveaux types de contrastes non-lineaires, comme la generation de second harmonique.

Hervé Rigneault

Papers

Laser scanning dark-field coherent anti-Stokes Raman scattering (DF-CARS): a numerical study

In vivo quantitative molecular absorption of glycerol in human skin using coherent anti-Stokes Raman scattering (CARS) and two-photon auto-fluorescence (Conference Presentation)

Polymorphism of amyloid fibrils monitored by polarization resolved microscopy

Probing molecular order of lipid reporters di-8-ANEPQ in cell plasma membrane by fluorescence polarimetry imaging

Two-volume fluorescence correlation spectroscopy for in-situ studies of cell signaling events