Bragg modulational instability induced by a dynamic grating in an optical fiber

By means of a dynamic Bragg grating obtained through cross-phase modulation with a beating wave in a highly birefringent fiber, we perform a detailed experimental study of Bragg modulational instability.     

Noise-like pulses generated at high harmonics in a partially-mode-locked km-long Raman fiber laser

We present a 5-km-long Raman fiber laser that delivers pulses at high harmonics of the fundamental cavity repetition rate, up to 1 GHz. The observed nanosecond pulses that propagate in an anomalous dispersion regime possess a complex noise-like structure with a coherence time of around 1 picosecond.     

Homogenization of variational problems in manifold valued <Emphasis Type="Italic">BV</Emphasis>-spaces

This paper extends the result of Babadjian and Millot (preprint, 2008) on the homogenization of integral functionals with linear growth defined for Sobolev maps taking values in a given manifold. Through a Γ-convergence analysis, we identify the homogenized energy in the space of functions of bounded variation. It turns out to be finite for BV-maps with values in the manifold. The bulk and Cantor parts of the energy involve the tangential homogenized density introduced in Babadjian and Millot (preprint, 2008), while the jump part involves an homogenized surface density given by a geodesic type problem on the manifold.     

Active Mamyshev regenerator

In this contribution, we numerically and experimentally investigate the extension of the so-called Mamyshev regenerator with the implementation of an additional Raman gain. We evaluate the potential efficiency and advantages of this new active Mamyshev regenerator at 40 Gbps and we highlight a strong reduction of the working power as well as a large improvement of the available output power.     

Chemical and strontium isotope characterization of rainwater in France: influence of sources and hydrogeochemical implications

Strontium isotope ratios and Ca2+, Na+, K+, Mg2+, Cl-, SO4(2-), NO3- and Sr2+ concentrations were measured in rainwater samples collected in four stations in France (Brest, Dax, Orleans and Clermont-Ferrand) over a period of 1 year. Each sample represented a monthly series of rain events. The chemical composition and the 87Sr/86Sr ratios of the rainwater samples varied considerably. Using Na concentrations as an indicator of marine origin, the proportion of marine and crustal elements was estimated from elemental ratios. Strontium isotopes were used to characterize the different sources using data from the four stations and the literature. Such sources include sea salts, crustal sources (carbonates, silicates and volcanic rocks) and anthropogenic sources (fertilizers, automobile exhausts, incinerators and urban heating).     

Shot-by-shot frequency calibration of CARS spectra: Application to the measurement of the collisional line shift in oxygen

A technique using a Fabry-Perot interferometer has been developed to calibrate high-resolution spectra obtained by Coherent Anti-Stokes Raman Spectroscopy (CARS). This technique was used to measure simultaneously the Raman frequency and the Raman signal at each laser shot. We demonstrate the accuracy of the method by measuring theQ(15) line shifts of molecular oxygen due to collisions with oxygen and water vapour.     

The quantitative measurement of electromigration in CeO2−x

We present an experimental device for the measurement of electromigration in a non stoichiometric oxide which is composed principally of two symmetrical electrolytic cells: CeO_2?x-(ZrO₂, Y₂O₃)-CeO_2?x+? and which permits one to analyse the variation of the oxygen composition at the extremities of a CeO_2?x sample subjected to an electric field.The quantitative measurement of the effective charge and ionic transport numbers are discussed in terms of the reduction or elimination of such undesirable but inherent effects as the exchanges of oxygen between the sample and its neighbourhood and of the heat associated with the electrical current.