Influence of the surface roughness on the properties of Au films measured by surface plasmon resonance and x-ray reflectometry.

Thickness and refractive index of Au films thermally evaporated onto glass substrates and with an underlayer of Cr are determined from surface plasmon resonance. The results for the thickness are found to agree very well with those from X-ray reflectivity when a simple model of layers with flat interfaces is used. Plasmon propagation along thin films is influenced by radiative damping due to scattering from surface roughness. To study this influence the surface roughness of the glass substrate, Cr an Au layers are measured by X-ray reflectometry and the results used to introduce three intermediate layers with effective refractive indices and thicknesses corresponding to the roughness. Then Fresnel's equations are used to fit the reflectivity and to deduce the layer properties. It is found that the roughness affects to a great extent the optical parameters of the Au films even when it is smaller than 1 nm. In particular, the absolute value of real part of the dielectric constant decreases while its imaginary part increases when those effects are not taken into account. © 2011, Elsevier Ltd

Resonant Waveguide Imaging of Living Systems: From Evanescent to Propagative Light

For more than 50 years, resonant waveguides (RWGs) have offered highly sensitive label-free sensing platforms to monitor surface processes such as protein adsorption, affinity binding, monolayer to multilayer build-up, bacteria and more generally adherent or confined living mammalian cells and tissues. Symmetrical planar dielectric RWG sensitivity was improved by metal coating of at least one of their surfaces for surface plasmon resonance undertaking (SPRWG). However, RWG sensitivity was often obtained at the expense of spatial resolution and could not compete with other high resolution fluorescence microscopies. For years, RWGs have only rarely been combined with high-resolution microscopy. Only recently, the improvement of intensity and phase light modulation techniques and the availability of low-cost high numerical aperture lenses have drastically changed the devices and methodologies based on RWGs. We illustrate in this chapter how these different technical and methodological evolutions have offered new, versatile, and powerful imaging tools to the biological community