Valérie Messager

Université de Rouen Normandie | UR · Aerothermochemistry Research Complex

The genesis of special relativity is intimately related to the development of the theory of light propagation. When optical phenomena were described, there are typically two kinds of theories: (i) One based on light rays and light particles and (ii) one considering the light as waves. When diffraction and refraction were experimentally discovered,...

The genesis of special relativity is intimately related to the development of the theory of light propagation. When optical phenomena were described, there are typically two kinds of theories: (i) One based on light rays and light particles and (ii) one considering the light as waves. When diffraction and refraction were experimentally discovered,...

The genesis of special relativity is intimately related to the development of the theory of light propagation. When optical phenomena were described, there are typically two kinds of theories: (i) One based on light rays and light particles and (ii) one considering the light as waves. When diffraction and refraction were experimentally discovered,...

Objectif La présence de micro-éveils au cours du sommeil implique une fragmentation de celui-ci, et sa qualité s’en trouve diminuée : les micro-éveils déstabilisent le sommeil mais n’en interrompent pas la continuité puisqu’il n’y a pas d’éveil au sens propre. Toutefois, la survenue de micro-éveils durant un stade de sommeil retarde le passage à un...

Sleep scoring is commonly performed from electroencephalogram (EEG), electrooculogram (EOG), and electromyogram (EMG) to produce a socalled hypnogram. A neurologist thus visually encodes each epoch of 30 s into one of the sleep stages (wake, REM sleep, S1, S2, S3, S4). To avoid such a long process (about 3–4 hours) a technique for automatic sleep s...

Far-field scattering pattern at the vicinity of the criticle angle of a cloud of submillimeter bubbles (air-water)

Often considered as the last ‘encyclopedist’, Henri Poincaré died one hundred years ago. If he was a prominent man in 1900 French Society, his heritage is not so clearly recognised, particularly in France. Among his too often misunderstood works is his contribution to the theory of relativity, mainly because it is almost never presented within Poin...

We report experimental investigations on the influence of various optical effects on the far-field scattering pattern produced by a cloud of optical bubbles near the critical scattering angle. Among the effects considered, there is the change of the relative refractive index of the bubbles (gas bubbles or some liquid–liquid droplets), the influence...

Otto E. Rössler is well-known in "chaos theory" for having published one of the most often used benchmark systems producing chaotic attractors. His contribution is mostly reduced to this simple chaotic system published in 1976. Our aim is to show that a slightly earlier paper contains, in fact, much more and reveals a deep topological understanding...

The van der Pol attractor exhibits a wide variety of behavior depending on the control parameter values: limit cycles, quasiperiodic motion on a torus, mode locking, period doubling, banded chaos, boundary crises, torus wrinkling, breakup of a torus, and toroidal chaos. The organization of these phenomena with respect to each other is well describe...

We propose a new method for measuring the phase and the amplitude of a short laser pulse that is based on shearing interferometry in the spectral domain combined with time gating. The method has several features in common with spectral interferometry for direct electric-field reconstruction, in particular, fast and direct reconstruction of the phas...

We report a simple method to measure the third-order nonlinear refraction and absorption of bulk materials and waveguides. This method relies on the nonlinear evolution of the spectral intensity and width of femtosecond pulses, owing to self-phase modulation, according to a variable chirp introduced before propagation through the nonlinear sample....

We demonstrate a new technique for the direct, real-time, femtosecond scale temporal measurement based on the conversion of temporal information to the spectral domain. The potential of the method has been experimentally investigated with an optical fiber spectral compressor device, first stretching and up-chirping the pulses in a prism dispersive...

We propose and demonstrate a new and simple technique for characterization of fast third order optical nonlinearity of wave-guides and bulk materials. Z-scan method, proposed and developed or bulk materials, has been preferred by experimentalists. It investigates nonlinear spatial distortion induced on a focused laser beam. In fact the technique th...

Summary form only given. Results on third order optical nonlinearity characterization are presented using a recent technique based on nonlinear spectral evolution of femtosecond pulses The method consists in a first step of pulse stretching in a prisms line of variable dispersion; afterwards, pulses propagate across the nonlinear sample under test...

A new, simple method to measure the nonlinear refraction and absorption of bulk material and waveguides is proposed. The method relies on the evolution of the intensity and width of femtosecond-pulse spectra, owing to self-phase modulation, as a function of variable chirp and stretching introduced at the input.

Powerful computational techniques have been developed to study chaotic attractors that are generated by stretching and folding processes. These include relative rotation rates for de-termining the organization of unstable periodic orbits and simplex distortion procedures for estimating the topological entropy of these orbits. These methods are usef...