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Total internal reflection fluorescence (TIRF) microscopy allows the visualization of the dynamic membrane-associated actin-like MreB filaments in live bacterial cells with high temporal resolution. This chapter describes computerized analysis methods to quantitatively characterize the dynamics and morphological properties of MreB assemblies. These include how to (1) segment bacterial cells, (2) perform single-particle tracking (SPT) of MreB filamentous structures, (3) classify their dynamic modes using mean squared displacement (MSD) analysis, and (4) measure their dimensions and orientation.

International audience; The dispersion properties of surface modes supported by metal/dielectric interfaces perforated by twodimensional arrays of subwavelength apertures are studied. An analytical surface-impedance model is derived. It provides closed-form expressions for the dispersion relation of surface modes and allows to take into account the aperture geometry and the dispersive and dissipative properties of the metal. The model predicts the dispersion relation and the mode lifetime, in quantitative agreement with fully vectorial computational results and with experimental data obtained at optical frequencies. The analysis reveals a double plasmonic band gap in the center of the Brillouin zone for a square array. It additionally clarifies the effects of various different geometrical and material parameters on the surface properties.

We report on high-accuracy angle-resolved optical transmission measurements through anisotropic 2D plasmonic crystals made of gold films with large-area rectangular arrays of nanoscale square holes, deposited on GaAs substrates. The measurements reveal the dispersion relations of air-gold and gold-GaAs surface plasmon polaritons. The crystal anisotropy induces a separation between plasmonic modes propagating in different directions. Their symmetry and dispersion properties are discussed.

International audience; The impact of the periodicity on the dispersion relation of surface modes supported by two dimensional (2D) structured metallic films is experimentally and numerically investigated between 1 and 5 μm. A coupling between modes propagating in two nearly orthogonal directions forming an angle of 77° is evidenced for a rectangular array of holes perforated in a gold film. The coupling results in a narrow band gap for nonzero wavevectors and in a coupled mode with a large density of states and a strong radiative damping. We show that the gap location in the (ω,k) space can be precisely tuned by changing the 2D period.

Subwavelength dielectric and metallic gratings embedded in vacuum can act as highly-resonant spectral filters. We review the theoretical principles for the design of symmetric dielectric and metal gratings to conceive efficient optical filters in the mid and far infrared range, and we show how both resonance width and resonance wavelength can be tuned. We describe an original process for the fabrication of free-standing SiC gratings, and we present the first samples obtained with 10 mm period. Experimental angularly resolved transmission spectra show evidences of their filtering properties.

Thin nanostructured metal films allow to control radiative and non-radiative losses of surface plasmon polariton modes without changing their group velocities. This effect is studied in plasmonic waveguides made of thin gold films drilled with very narrow slits and deposited on a GaAs substrate. The analysis is supported by high-resolution angle-resolved transmission measurements and rigorous electromagnetic calculations. We show that the excitation of air/gold and gold/GaAs surface waves leads to Fano-type resonances with specific light localization into the slits. As a result, gold/GaAs surface waves induce a modulation of radiative and non-radiative losses of air/gold surface waves. The minimum and maximum of the Fano-type resonance introduce two propagation regimes. In the radiative propagation regime, the losses due to the absorption are negligible, whereas an efficient inhibition of free-space coupling is demonstrated in low-loss propagation regime.

High-resolution angle-resolved transmission measurements are carried out through nanostructured plasmonic waveguides made of thin gold films with very narrow slits deposited on GaAs substrates. They reveal transmission intensity modulations along the air/metal surface plasmon band, due to the presence of metal/substrate surface modes. Two propagation regimes have been identified. In this plasmonic waveguide, the radiative emission can be enhanced or inhibited by a slight modification of the refractive index of the substrate (δn∕n≃1%), allowing to control the propagation regime of surface plasmon waves along the air/metal interface.

International audience; Performing label free coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) in endoscope imaging is a challenge, with huge potential clinical benefit. To date, this goal has remained inaccessible because of the inherent coherent Raman noise that is generated in the fiber itself. By developing double-clad hollow core photonic crystal fiber, we demonstrate coherent anti-Stokes Raman scattering and stimulated Raman scattering in an "endoscope-like‟ scheme. Both the excitation beams and the collected CARS and SRS signals travel through the same fiber. No CARS and SRS signals are generated within the hollow core fiber even for temporally overlapping pump and Stokes beams, leading to excellent image quality. The CARS and SRS signals generated in the sample are coupled back into a high numerical aperture multimode cladding surrounding the central photonic crystal cladding. We demonstrate this scheme by imaging molecular vibrational bonds of organic crystal deposited on a glass surface.