Van der Waals interactions across stratified media

Working at the Lifshitz level, we investigate the van der Waals interactions across a series of layers with a periodic motif. We derive the complete form of the van der Waals interaction as an explicit function of the number of periodic layers. We then compare our result with an approximation based on an anisotropic-continuum representation of the stratified medium. Satisfactory agreement between discrete-layer and continuum models is reached only for thicknesses of ten or more layers.Comment: 9 pages and 4 figure

Nonlinear localized waves in a periodic medium

We analyze the existence and stability of nonlinear localized waves in a periodic medium described by the Kronig-Penney model with a nonlinear defect. We demonstrate the existence of a novel type of stable nonlinear band-gap localized states, and also reveal an important physical mechanism of the oscillatory wave instabilities associated with the band-gap resonances.Comment: 4 pages, 5 figure

Dielectric multilayer waveguides for TE and TM mode matching

We analyse theoretically for the first time to our knowledge the perfect phase matching of guided TE and TM modes with a multilayer waveguide composed of linear isotropic dielectric materials. Alongside strict investigation into dispersion relations for multilayer systems, we give an explicit qualitative explanation for the phenomenon of mode matching on the basis of the standard one-dimensional homogenization technique, and discuss the minimum number of layers and the refractive index profile for the proposed device scheme. Direct applications of the scheme include polarization-insensitive, intermodal dispersion-free planar propagation, efficient fibre-to-planar waveguide coupling and, potentially, mode filtering. As a self-sufficient result, we present compact analytical expressions for the mode dispersion in a finite, N-period, three-layer dielectric superlattice.Comment: 13 pages with figure

The Casimir force and the quantum theory of lossy optical cavities

We present a new derivation of the Casimir force between two parallel plane mirrors at zero temperature. The two mirrors and the cavity they enclose are treated as quantum optical networks. They are in general lossy and characterized by frequency dependent reflection amplitudes. The additional fluctuations accompanying losses are deduced from expressions of the optical theorem. A general proof is given for the theorem relating the spectral density inside the cavity to the reflection amplitudes seen by the inner fields. This density determines the vacuum radiation pressure and, therefore, the Casimir force. The force is obtained as an integral over the real frequencies, including the contribution of evanescent waves besides that of ordinary waves, and, then, as an integral over imaginary frequencies. The demonstration relies only on general properties obeyed by real mirrors which also enforce general constraints for the variation of the Casimir force.Comment: 18 pages, 6 figures, minor amendment

Les applications des couches minces en polarimétrie

A thin transparent film on glass is used in order to get reflecting or transmitting polarizers. The former case is the analogous of Brewster's reflection. One can get a very luminous and almost achromatic polarizer by using a high index film. In the later case, we use a device similar to the pile of plates. Two plates of glass covered with titanium dioxyde on both sides give a degree of polarization of 99,7 per 100

RÉSULTATS RÉCENTS OBTENUS EN SPECTROSCOPIE DES MÉTAUX ET ALLIAGES

Exposé général de certains résultats récents concernant les relations entre la structure électronique et les propriétés optiques des métaux et alliages. Les principaux problèmes discutés sont les suivants : 1° absorption due aux électrons de conduction ; 2° absorption par transitions interbandes ; 3° oscillations de plasma ; 4° absorption dans les alliages. La discussion relative aux oscillations de plasma est très brève, car un exposé d'ensemble sur la question a déjà paru dans le Journal de Physique [38].General report on some recent results bearing on electronic structure and optical properties of metals and alloys. The main problems discussed are : 1) absorption due to conduction electrons ; 2) absorption by interband transitions ; 3) plasma oscillations ; 4) absorption in alloys. The discussion on plasma oscillations is very short, a general survey of this question has already been published in the Journal de Physique [38]

La détermination de l'indice et de l'épaisseur des couches minces transparentes

Spectrophotometric methods : normal and oblique incidence. New rapid method for the measurement of the refractive indices. Results obtained on thin films of various materials. Polarimetric methods; formula allowing a rapid calculation for films of optical thickness greater than λ/4