Longitudinal coherence measurements of a transient collisional x-ray laser

Abstract

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 4d1S0 --> 4p1P1 lasing transition to be approximately 400 microm (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 approximately 0.29 pm is a factor of 4 less than previously measured in quasi-steady-state x-ray laser schemes.

X-ray laser pulses at the Fourier transform limit

“…The LULI x-ray laser The fit of our theory to the Klisnick et al [9] experimental data of figure 9 is worse than for previous x-ray laser coherence measurements [7,8] figure 11 assuming ∆ν = 9.5 × 10 11…”

“…From estimates of the frequency width of the gain coefficient of x-ray lasers, x-ray laser pulses of 3 ps duration are calculated to be close to the Fourier transform limit [3,4,8]. However, there has not been a direct measurement of the frequency bandwidth of x-ray laser output alongside a measurement of the pulse duration of the same x-ray laser pulses.…”

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).…”

“…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).…”

Cohérence temporelle et largeur spectrale des lasers XUV transitoires pompés en incidence rasante

“…Il faut en effet un interféromètre XUV d'excellente qualité utilisant des technologies de pointe. Les premières expériences utilisaient ainsi des interféromètres à division d'amplitude [4,5] équipés de lames séparatrices multicouches XUV. La faible stabilité des lasers XUV et le faible taux de répétition des installations rendaient de plus difficiles la réalisation de séries de mesures de bonne qualité et a fortiori la réalisation d'études de la largeur spectrale en fonction d'un paramètre.…”