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Da Pieve F.,Vrije Universiteit Brussel | Kruger P.,Laboratory Interdisciplinaire Carnot de Bourgogne
Physical Review Letters | Year: 2013

A first principles approach for spin- and angle-resolved resonant photoemission is developed within multiple scattering theory and applied to a Cr(110) surface at the 2p-3d resonance. The resonant photocurrent from this nonferromagnetic system is found to be strongly spin polarized by circularly polarized light, in agreement with experiments on antiferromagnetic and magnetically disordered systems. By comparing the antiferromagnetic and Pauli-paramagnetic phases of Cr, we explicitly show that the spin polarization of the photocurrent is independent of the existence of local magnetic moments, solving a long-standing debate on the origin of such polarization. New spin polarization effects are predicted for the paramagnetic phase even with unpolarized light, opening new directions for full mapping of spin interactions in macroscopically nonmagnetic or nanostructured systems. © 2013 American Physical Society. Source


Chevalier S.,Laboratory Interdisciplinaire Carnot de Bourgogne
Materials and Corrosion | Year: 2014

Materials able to form protective chromia, Cr2O3, are most of time good candidates to be used at high temperatures in oxidizing atmospheres. Minor element additions are necessary to increase their mechanical or chemical properties. Among them, the reactive elements (RE) are highly efficient to improve the high temperature oxidation behavior of alloys.Their addition in small quantity is enough to greatly decrease the oxidation rates, but above all to drastically increase the oxide scale adherence to the basematerials.Thatwas the key point of what observed Pfeil 75 years ago. Since that date, many results have been published, many theories have been proposed, and many discussions have been engaged. Until now, the reasons why RE are so efficient are not fully understood, several hypotheses have been proposed in order to explain their beneficial effect on the oxide scale formation. According to the large amounts of published papers on this topic, there is probably no single theory envisageable to explain their role, whatever their nature, the tested materials and then the native oxide scale, as well as the nature of the oxidizing atmosphere.The decrease of the oxidation rate and the improvement of the oxide layer adherence are the final results due to RE additions. Generally, RE additions favor the nucleation and the growth of scales. They decrease the oxide grain size, and consequently could change scale plasticity and creep, which can modify the growth and/or thermal stresses generated within the scale during its growth or its cooling to room temperature. They prevent the detrimental sulfur effect and suppress dislocation climb in the metal and, then, limit cation transport (poisoned interface model). 75th Pfeil's patent anniversary seems good to make a pause in order to analyze what we really understood on the reactive element effect in chromia-forming materials. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Finot C.,Laboratory Interdisciplinaire Carnot de Bourgogne
Optics Letters | Year: 2015

We show that the amplitude and phase shaping of only four sidebands of the optical spectrum is sufficient to synthesize parabolic, triangular, or flat-top pulse trains at high repetition rates. Selection of the symmetric carriersuppressed waveform is easily achieved by changing the phase difference between the inner and outer spectral lines. Experiments carried out at a repetition rate of 40 GHz confirm the high quality of the intensity profiles that are obtained. © 2015 Optical Society of America. Source


Boscolo S.,Aston University | Finot C.,Laboratory Interdisciplinaire Carnot de Bourgogne | Karakuzu H.,Aston University | Petropoulos P.,University of Southampton
Optics Letters | Year: 2014

We numerically show the possibility of pulse shaping in a passively mode-locked fiber laser by inclusion of a spectral filter into the laser cavity. Depending on the amplitude transfer function of the filter, we are able to achieve various regimes of advanced temporal waveform generation, including ones featuring bright and dark parabolic-, flat-top-, triangular- and saw-tooth-profiled pulses. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for controlling the dynamics of mode-locked fiber lasers. © 2014 Optical Society of America. Source


Millot G.,Laboratory Interdisciplinaire Carnot de Bourgogne | Wabnitz S.,University of Brescia
Journal of the Optical Society of America B: Optical Physics | Year: 2014

We review polarization stabilization techniques based on the polarization attraction effect in low-birefringence fibers. Polarization attraction or pulling may be based on cross-polarization modulation, on parametric amplification, and on Raman or Brillouin scattering. We also review methods for laser frequency conversion based on polarization modulation instabilities in low-and high-birefringence fibers, and photonic crystal fibers. Polarization instabilities in nonlinear fibers may also be exploited for sensing applications. © 2014 Optical Society of America. Source

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