B4C/W multilayer mirrors designed for an x-ray beamline at the MEGAJOULE facility are susceptible to x-ray damage. The OCTAL laser was implemented to generate a gold plasma with a continuous x-ray spectrum (0.1 to 1.5 keV) used to irradiate the mirror. The fluence on the sample is 0.05 J/cm2 per shot. The pulse duration is about 1 ns. The temporally integrated spectrum reflected by the mirror is analyzed by a bent crystal spectrometer and recorded on photographic film. The spectral analysis suggests that an increase of the mean period of the multilayer happens during the second shot. This expansion is estimated to be 5% with respect to the unexposed mirror. After the second shot, destruction of the multilayer coating in the central part of the sample and irreversible damages in the other part characterized by a decrease of Bragg reflectivity have been observed.
Résumé: Le principe de la diffraction par un réseau lamellaire gravé dans miroir multicouche est exposé. Un tel réseau a été réalisé en combinant les techniques de dépôt de couches minces, de lithographie électronique et de "gravure plasma". Une application originale de ce dispositif, appelée "polychromateur", est présentée.
RESEAUX LAMELLAIRES GRAVES DANS UNE STRUCTURE MULTICOUCHELes réseaux lamellaires gravés dans des structures multicouches constituent un système doublement périodique présentant une périodicité en profondeur correspondant à l'empilement multicouche et une périodicité latérale correspondant à la gravure. Un réseau lamellaire est Article published by EDP Sciences and available at http://www.annphys.org or http://dx
Advanced manufacture of DWDM multidielectric narrow-band optical filters designed for broadband technologies are presented and discussed. Three-cavity structures of 2 nm half-maximum bandwidth pass-band filters in the 1550 nm range with more than 94% at peak transmission and 4 nm width at 20 dB of attenuation is presented. It has been designed for 400 GHz channel spacing.
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