Une europeens Belgique), comparaison les (Allemagne, USA internationale et le France, Japon, fondee Italie, montre sur Espagne, la situation l'existence Grande-Bretagne, de certains de quelques pays europeens (Allemagne, France, Italie, Espagne, Grande-Bretagne, B lgiqu ), les USA t le apon, ontre l'exi t nce de quelq es tendances lourdes en matiere de moyens de paiement : Un clivage existe entre les pays caracterises par une part elevee de la monnaie fiduciaire dans la masse monetaire qui, au cours de la decennie, est ^1 restee de l'ordre de 30 % pour le premier groupe (Allemagne, Belgique, Espagne, Japon, USA), alors qu'elle a fortement decline pour s'etablir aux alentours de 15 % pour le second groupe (France, Italie, Grande-Bretagne). En matiere d'instruments scripturaux, des situations atypiques existent : • Les pays bipolaires ou dominent deux moyens de paiement scripturaux : * Les USA, pays a forte utilisation de cheque qui representent 84 % des reglements scripturaux avec pres de 50 milliards de cheques emis, dont 55 % par les entreprises, et de cartes (14 % des reglements). ☆ Les pays de l'Europe du Nord (Allemagne, Belgique) qui sont des pays domines par le virement et l'avis de prelevement (90 % au total) et ou le cheque et les reglements-cartes, au demeurant garantis, n'occupent qu'une place marginale (10 %). * Le Japon, pays de virement et de prelevement (70 % au total) ou la carte occupe neanmoins une place significative (19 %). • Les pays multipolaires ou la panoplie des moyens de paiement scripturaux est plus ouverte : * Les pays europeens a tradition de cheque, la France et la Grande-Bretagne, chez lesquels le cheque, largement utilise pour les reglements de particuliers, represente encore plus de la moitie des reglements scripturaux. * Les pays europeens du Sud, Italie et Espagne, qui utilisent, de maniere assez equilibree, cheque, virement, prelevement et carte.
Crater shapes and plasma plume expansion in the interaction of sharply focused laser beams with metals in air at atmospheric pressure were studied. Laser ablation efficiencies and rates of plasma expansion were obtained. The best ablation efficiency was observed with femtosecond laser pulses. It was found that for nanosecond pulses the laser beam absorption, its scattering and reflection in plasma were the limiting factors for efficient laser ablation and precise material sampling with sharply focused laser beams. The experimental results obtained were analyzed with relation to different theoretical models of laser ablation.
En Mais industrie, œuvre France, il pour s'agit notamment la moderniser gestion d'une des industrie par les moyens le systemes niveau qui de a des paiement d'echange la particularite investissements est et de devenue reglement. de ne mis une pas en industrie, notamment par le niveau des investissements mis en œuvre pour moderniser les systemes d'echange et de reglement. Mais il s'agit d'une industrie qui a la particularite de ne pas fonctionner selon la logique du prix du marche et de ne pas equilibrer globalement ses couts. En effet, les charges comme les seuils d'investissements sont de plus en plus eleves et sont loin d'etre equilibres par les recettes directes dans un environnement fortement concurrentiel et expose a la desintermediation. Les principales donnees economiques afferentes a la gestion des moyens de paiement (base 1992, en milliards de F) appellent quelques commentai-
Crater shapes and plasma plume expansion in the interaction of femtosecond, picosecond and nanosecond laser pulses with various pure metal in air and noble gases at atmospheric pressure were studied. The craters formed at the surfaces were measured by an optical microscope profilometer with 0.01 micrometers depth and 0.5 micrometers lateral resolutions. The measurements of laser plasma expansion were carried out with ICCD camera with 3 micrometers spatial and 1 ns temporal resolutions. These measurements were made in 0-100 ns time delay range and at different wavelengths in 200-850 nm optical spectral range. Laser ablation efficiencies, crater profiles, plasma plume shapes at different time delays, rates of plasma expansion in both longitudinal and transversal directions to the laser beam were obtained. Experimental results were analyzed from the point of view of different theoretical models of laser beam interaction with plasma and metals. The laser pulse duration range used in our study was of particular interest, as it includes the characteristic time of electron-phonon relaxation in solids, that is, of the order off one picosecond. Thus, we could study the different regimes of laser ablation without and with laser beam/plasma plume interaction. It was found that for nanosecond pluses the laser beam absorption, as well as its scattering and reflection in plasma, were the limiting factors for efficient laser ablation and precise material processing with sharply focused laser beams.
We present and characterize a very efficient optical device that employs the plasma mirror technique to increase the contrast of high-power laser systems. Contrast improvements higher than 10(4) with 50% transmission are shown to be routinely achieved on a typical 10 TW laser system when the pulse is reflected on two consecutive plasma mirrors. Used at the end of the laser system, this double plasma mirror preserves the spatial profile of the initial beam, is unaffected by shot-to-shot fluctuations, and is suitable for most high peak power laser systems. We use the generation of high-order harmonics as an effective test for the contrast improvement produced by the double plasma mirrors.
In this paper, we present measurements of the excited carrier density in various wide band gap oxides irradiated by short laser pulses, at intensities below and above breakdown threshold. This is achieved with the help of time resolved interferometry in the frequency domain, a technique which was successfully used to study the dynamics of photoexcited carriers in insulators. The result obtained in different experimental conditions, distance from the surface, pump intensities and duration, during or after the pump pulse, are discussed and compared to the models recently developed to explain optical breakdown.
Laser ablation of pure metals by femtosecond, picosecond and nanosecond pulses is studied in air at atmospheric pressure. Craters created after interaction of visible and UV laser pulses with the targets are investigated. The dependence of the ablation efficiency in terms of ablated volume per unit of energy on the pulse duration is discussed.
Rubidium titanyl phosphate (RTP) is widely used for electro-optical applications at low switching voltages. RTP is nonhygroscopic and does not induce piezoelectric ringing up to the megahertz range. It has large electro-optic (EO) coefficients and a high damage threshold. We present here the EO coefficient wavelength dispersion measurements in the [550,950] nm spectral range using a method based on spectral interferometry. These data are necessary for, among other things, a quantitative modelization of an EO carrier-envelope phase shifter.
