X-ray-ultraviolet beam splitters for the Michelson interferometer

International audienceWith the aim of realizing a Michelson interferometer working at 13.9 nm, we have developed a symmetrical beam splitter with multilayers deposited on the front and back sides of a silicon nitride membrane. On the basis of the experimental optical properties of the membrane, simulations have been performed to define the multilayer structure that provides the highest reflectivity-transmission product. Optimized Mo-Si multilayers have been successfully deposited on both sides of the membrane by use of the ion-beam sputtering technique, with a thickness-period reproducibility of 0.1 nm. Measurements by means of synchrotron radiation at 13.9 nm and at an angle of 45° provide a reflectivity of 14.2% and a transmission of 15.2% for a 60% s-polarized light, close to the simulated values. Such a beam splitter has been used for x-ray laser Michelson interferometry at 13.9 nm. The first interferogram is discussed

Study of XUV beam splitter flatness for use on a Michelson interferometer

International audienceA XUV Michelson interferometer has been developed by LIXAM/CEA/LCFIO and has been tested as a Fourier-transform spectrometer for measurement of X-ray laser line shape. The observed strong deformation of the interference fringes limited the interest of such an interferometer for plasma probing. Because the fringe deformation was coming from a distortion of the beam splitter (5 × 5 mm^2 open aperture, about 150 nm thick), several parameters of the multilayer deposition used for the beam splitter fabrication have been recently optimized. The flatness has been improved from 80 nm rms obtained by using the ion beam sputtering technique, to 20 nm rms by using the magnetron sputtering technique. Over 3 × 3 mm^2, the beam splitter has a flatness better than 4 nm rms

Longitudinal coherence measurements of a transient collisional x-ray laser

We present what is to our knowledge the first longitudinal coherence measurement of a transient inversion collisional x-ray laser. We investigated the picosecond output of a Ni-like Pd x-ray laser at 14.68 nm generated by the COMET laser facility at the Lawrence Livermore National Laboratory. Interference fringes were generated with a Michelson interferometer setup in which a thin multilayer membrane was used as a beam splitter. We determined the longitudinal coherence for the 4d 1 S0! 4p 1 P1 lasing transition to be �400 mm (1�e half-width) by changing the length of one interferometer arm and measuring the resultant variation in fringe visibility. The inferred gain-narrowed linewidth of �0.29 pm is a factor of 4 less than previously measured in quasi-steady-state x-ray laser schemes. © 2003 Optical Society of America OCIS codes: 140.7240, 030.1640, 300.3700, 300.6360. The rapid development of x-ray lasers combined with the availability of optics in the extreme ultraviolet has led to several applications, such as in interferometry1 and holography, 2 that depend on the coherence properties of the source pulse. In amplitude division interferometry, if the phase fronts of the two arms spatially overlap and are copropagated and if the arm length