Stabilization of self-focusing instability in wide-aperture semiconductor lasers

A mechanism for the stabilization of the output of filamentary broad-area edge-emitting semiconductor lasers is analyzed experimentally and theoretically. This mechanism occurs when the carrier density is profiled in the transverse direction. The laser structure consisted of a wide-aperture edge-emitting laser diode operating in pulsed mode to avoid thermal guiding effects. The injection current profile was modified from the usual step-function case to a Lorentzian-like profile through the inclusion of a 10 mum p-type epitaxial spreading layer. The resulting nonlinear transverse mode is described and the possibility of its observation in two transverse dimensions is discussed

Le quartier de l’Arsenal à Metz (Moselle) : topographie urbaine et évolution architecturale durant l’Antiquité

International audienceThe district of the Arsenal in the south-west of the town has recently been the subject of two extensive rescure excavations over a 5,000 sq. metres area. Due to a significant amount of levelling work in the 19th century, the most revealing results concern the years between the 1st and 3rd centuries.It has, thus been possible for the first time in Metz to understand the layout of the parcels of land and its development over nearly a third of an insula. A settlement made up of distinct plots around 10 metres in size, facing the street, was followed by a larger estate in the 2nd century, totally occupied by a vast domus. The preliminary study of organic traces found in the gutters of the streets looks promising and should, above all, lead to a better understanding of the way rubbish was dealt with in the urban area. Finally the find of four streets and a ditch from a fifth one considerably adds to our knowledge of the organisation of the district. In conjunction with evidence from former excavations, it is now possible to trace an original system, seemingly different from the orthonormal network of the town centre and which cannot just be explained by the rather hilly relief of the site.Le quartier de l'Arsenal, situé au sud-ouest de la ville, a fait l'objet de deux fouilles de sauvetage récentes sur une surface cohérente de 5 000 m2. En raison d'importants travaux de nivellement au XIXe s., les résultats les plus significatifs concernent les Ier-IIIe s. Il a ainsi été possible, pour la première fois à Metz, d'appréhender le parcellaire et son évolution sur près du tiers d'un îlot. A un habitat constitué de lots distincts d'environ 10 m de large, appuyés sur la rue, succède au IIe s. une propriété plus grande, entièrement occupée par une vaste domus. L'étude à titre expérimental des traces organiques présentes dans les caniveaux de voirie s'avère prometteuse, et devrait notamment permettre de mieux comprendre la gestion des déchets en milieu urbain. Enfin la mise au jour de quatre rues et d'un fossé d'une cinquième renouvelle considérablement nos connaissances sur l'organisation du quartier. A la lumière des données de fouilles anciennes se dessine maintenant un système original, distinct du réseau vraisemblablement orthonormé du centre-ville, et que le relief assez accidenté du site ne peut à lui seul expliquer