Surface plasmon-mediated far-field emission of laser dye solutions

Angle-resolved reflection and emission spectra of metal gratings consisting of sub-wavelength grooves and immersed into rhodamine B and rhodamine 19 solutions are presented. The measured reflection and emission dispersion diagrams reveal the surface plasmon polaritons positions and strong plasmon mediated emission enhancement, respectively. The same grating could be easily re-used for the characterization of different dye-molecules

Single and dual fiber nano-tip optical tweezers: trapping and analysis

An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance

Dynamical typicality of quantum expectation values

We show that the vast majority of all pure states featuring a common expectation value of some generic observable at a given time will yield very similar expectation values of the same observable at any later time. This is meant to apply to Schroedinger type dynamics in high dimensional Hilbert spaces. As a consequence individual dynamics of expectation values are then typically well described by the ensemble average. Our approach is based on the Hilbert space average method. We support the analytical investigations with numerics obtained by exact diagonalization of the full time-dependent Schroedinger equation for some pertinent, abstract Hamiltonian model. Furthermore, we discuss the implications on the applicability of projection operator methods with respect to initial states, as well as on irreversibility in general.Comment: 4 pages, 1 figure, accepted for publication in Phys. Rev. Let

Excitation of whispering gallery modes with a "point-and-play", fiber-based, optical nano-antenna

We demonstrate the excitation and detection of whispering gallery modes in optical microresonators using a "point-and-play", fiber-based, optical nano-antenna. The coupling mechanism is based on cavity-enhanced Rayleigh scattering. Collected spectra exhibit Lorentzian dips, Fano shapes, or Lorentzian peaks, with a coupling efficiency around 13\%. The spectra are characterized by the coupling gap, polarization, and fiber tip position. The coupling method is simple, low-cost and, most importantly, the \textit{Q}-factor can be maintained at $10^8$ over a wide coupling range, thereby making it suitable for metrology, sensing, or cavity quantum electrodynamics (cQED) experiments

Diffusion is capable of translating anisotropic apoptosis initiation into a homogeneous execution of cell death

<p>Abstract</p> <p>Background</p> <p>Apoptosis is an essential cell death process throughout the entire life span of all metazoans and its deregulation in humans has been implicated in many proliferative and degenerative diseases. Mitochondrial outer membrane permeabilisation (MOMP) and activation of effector caspases are key processes during apoptosis signalling. MOMP can be subject to spatial coordination in human cancer cells, resulting in intracellular waves of cytochrome-c release. To investigate the consequences of these spatial anisotropies in mitochondrial permeabilisation on subsequent effector caspase activation, we devised a mathematical reaction-diffusion model building on a set of partial differential equations.</p> <p>Results</p> <p>Reaction-diffusion modelling suggested that even if strong spatial anisotropies existed during mitochondrial cytochrome c release, these would be eliminated by free diffusion of the cytosolic proteins that instantiate the apoptosis execution network. Experimentally, rapid sampling of mitochondrial permeabilisation and effector caspase activity in individual HeLa cervical cancer cells confirmed predictions of the reaction-diffusion model and demonstrated that the signalling network of apoptosis execution could efficiently translate spatial anisotropies in mitochondrial permeabilisation into a homogeneous effector caspase response throughout the cytosol. Further systems modelling suggested that a more than 10,000-fold impaired diffusivity would be required to maintain spatial anisotropies as observed during mitochondrial permeabilisation until the time effector caspases become activated.</p> <p>Conclusions</p> <p>Multi-protein diffusion efficiently contributes to eliminating spatial asynchronies which are present during the initiation of apoptosis execution and thereby ensures homogeneous apoptosis execution throughout the entire cell body. For previously reported biological scenarios in which effector caspase activity was shown to be targeted selectively to specific subcellular regions additional mechanisms must exist that limit or spatially coordinate caspase activation and/or protect diffusing soluble caspase substrates from unwanted proteolysis.</p

Optical fiber nano-tweezers, a complementary approach for micro- and nanoparticle trapping

SPIE Structured Light, 2018, Yokohama, JapanInternational audienc

Out-of-equilibrium force measurements of dual-fiber optical tweezers

International audienc

Caractérisation de modes hybrides par spectroscopie de m-lines hémisphériques

Nous présentons la technique des m-lines hémisphériques, conçue pour l'étude de guides plans biréfringents. Un guide d'onde obtenu par implantation ionique dans un substrat de KTP orienté est caractérisé. L'indice effectif et la polarisation des modes guidés ont été mesurés en fonction de la direction de propagation. Les résultats obtenus sont en très bon accord avec le modèle théorique développé

Applications optiques de couches minces de chalcogénures

Des couches minces adhérentes d As-S, d As-Se et de Ge-As-Se dopées erbium ont été obtenues par pulvérisation cathodique RF. Une étude morphologique a montré la présence de structures homogènes pour les couches d As-S et d As-Se, et des structures colonnaires pour les couches de Ge-As-Se. La photoluminescence (PL) à 1,55 m a été détectée dans le volume sur toutes les compositions. La PL a été aussi observée en configuration guidée pour des couches d As-S. La fabrication de guides d onde canaux et de réseaux de diffraction a été entreprise par photo-dopage à l argent. La gravure humide a été également utilisée pour fabriquer des guides canaux. Un confinement de la lumière à 1,55 m a été observé.GRENOBLE1-BU Sciences (384212103) / SudocGRENOBLE INP-Phelma (381852301) / SudocSudocFranceF

Direct measurement of mode hybridization in birefringent slab waveguides by hemisphere m-line ellipsometry

The hemisphere m-line technique was used in an ellipsometric configuration to investigate the hybrid waveguide modes of a KTP ion-implanted birefringent planar waveguide. The effective index dispersion as a function of the propagation direction was measured and the polarization angles of the hybrid modes were directly measured for the first time. Special consideration was given to mode crossings in the dispersion diagram. Rotation of up to 3° of the polarization plane of the reflected beam with respect to the incident polarization was investigated. A theoretical model based on the transfer matrix approach was developed and good agreement with experimental results was obtained