Anne-Laure Helbert

Tunable angular-dependent second-harmonic generation in glass by controlling femtosecond laser polarization

Mastering second-harmonic generation (SHG) in glasses is essential for achieving second-order nonlinear devices. Three-dimensional SHG patterns with controllable angular dependence were achieved in Li2O-Nb2O5-SiO2 glass by femtosecond laser irradiation. Electron backscatter diffraction indicated that the angular dependence was associated with preferential nanocrystal orientation: crystal polar axes are distributed within a plane perpendicular to the incident laser polarization direction. An orientation mechanism based on the application of laser-induced torques on the nanocrystal electric dipole was proposed. This work may pave the way to design devices such as frequency agile lasers based on electro-optical waveguides.

Multiscale modeling of a low magnetostrictive Fe-27wt%Co-0.5wt%Cr alloy

The present paper deals with the improvement of a multi-scale approach describing the magneto-mechanical coupling of Fe-27wt%Co-0.5wt%Cr alloy. The magnetostriction behavior is demonstrated as very different (low magnetostriction vs. high magnetostriction) when this material is submitted to two different final annealing conditions after cold rolling. The numerical data obtained from a multi-scale approach are in accordance with experimental data corresponding to the high magnetostriction level material. A bi-domain structure hypothesis is employed to explain the low magnetostriction behavior, in accordance with the effect of an applied tensile stress. A modification of the multiscale approach is proposed to match this result.

Magnetostrictive and magnetic effects in Fe-27%Co laminations

The present paper deals with the characterization of the magnetostriction of the Fe-27%Co alloy. When this alloy is annealed in the ferritic domain (between 700°C and 940°C) and submitted to a slow cooling, it exhibits a low and isotropic magnetostriction over a wide induction range (±1.5T). One reason that can explain this phenomenon is a high temperature selection of magnetic bi-domains preferentially oriented in the rolling plane. As soon as this material is annealed in the austenitic domain or quenched from the ferritic domain, the low and isotropic magnetostriction disappears giving way to a classical quadratic magnetostrictive behavior.