Recent developments in X-UV optics and X-UV diagnostics

Abstract

International audienceMetrology of XUV beams (X-ray lasers, high-harmonic generation and VUV free-electron lasers) is of crucial importance for the development of applications. We have thus developed several new optical systems enabling us to measure the optical properties of XUV beams. By use of a Michelson interferometer working as a Fourier-transform spectrometer, the line shapes of different X-ray lasers have been measured with a very high accuracy (Δλ/λ~10^-6). Achievement of the first XUV wavefront sensor has enabled us to measure the beam quality of laser-pumped as well as discharge-pumped X-ray lasers. A capillary discharge X-ray laser has demonstrated a very good wavefront allowing us to achieve an intensity as high as 3×10^14 W cm^-2 by focusing with a f=5 cm mirror. The sensor accuracy has been measured using a calibrated spherical wave generated by diffraction. The accuracy has been estimated to be as good as λ/120 at 13 nm. Commercial developments are underway. At Laboratoire drsquoOptique Appliquée, we are setting up a new beamline based on high-harmonic generation in order to start the femtosecond, coherent XUV optic

Maximizing the brilliance of high-order harmonics in a gas jet

“…of the harmonics with a Hartmann sensor for each setting [15]- [18]. We found a coincidence between the maximal photon flux and the wave front with the lowest aberrations.…”

Mo/Si multilayer-coated amplitude-division beam splitters for XUV radiation sources

“…The coated substrate in some cases has been etched from the back prior to the ML deposition leaving a window with a thin SiN or SiC membrane (30-890 nm) supporting a ML coating (Schä -fers et al, 1999;Khan Malek et al, 1989;Di Fonzo et al, 1994;Nguyen,1994;Da Silva et al, 1995b;Tinone et al, 1996;Wang et al, 2003Wang et al, , 2007. Sometimes this free membrane is coated on both sides (Zeitoun et al, 2004;Hubert et al, 2001;Smith et al, 2003). In other cases the Si substrate coated with SiN or SiC is back-etched after the ML deposition, leaving the ML on the SiN or SiC membrane (Stearns et al, 1986;Ceglio, 1989).…”

“…The BS shape was studied by means of a 4" Fizeau-type interferometer (ZYGO-GPI) (Hariharan, 1985). It is worth noting here that we qualify a BS to be of good quality (diffraction-limited) when the wavefront errors are lower than /14 r.m.s., being the radiation wavelength, according to the Marechal criterion (Zeitoun et al, 2004).…”

“…Such beam splitters based on multilayer-coated membranes (ML-BSs) are required for, for example, pump-probe experiments, parallel user operation at FELs, autocorrelation measurements to determine the time structure of FEL pulses (Mitzner et al, 2008(Mitzner et al, , 2009), online wavefront diagnostics (Zeitoun et al, 2004), ellipsometry (Kortright et al, 1992;Kimura et al, 2005), polarimetry (Schä fers et al, 1999), interferometry (Da Silva et al, 1995a;Smith et al, 2003), transmission filters (Volodin et al, 2010), Fourier transform spectroscopy (de Oliveira et al, 2011) and as output couplers for laser cavities (Stearns et al, 1986;Ceglio, 1989).…”

Limitations of Extreme Nonlinear Ultrafast Nanophotonics

“…[13]. Due to the rather low conversion efficiency of the HHG process [14,15], the optimization of HHG in terms of brilliance-or number of photons per time interval imping-ing on a sample-has been an ongoing topic in the community [16][17][18][19]. The brilliance, or brightness, of a light source is the standard when comparing photon-producing elements, and is the benchmark especially when researching light-matter interactions with low rates or cross-sections.…”