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 4dS<sub>0</sub><sup>1</sup>→4pP<sub>1</sub><sup>1</sup> lasing transition to be ~400μm (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 ~0.29pm is a factor of 4 less than previously measured in quasi-steady-state x-ray laser schemes.
© 2003 Optical Society of America
(030.1640) Coherence and statistical optics : Coherence
(140.7240) Lasers and laser optics : UV, EUV, and X-ray lasers
(300.3700) Spectroscopy : Linewidth
(300.6360) Spectroscopy : Spectroscopy, laser
Raymond F. Smith, James Dunn, James R. Hunter, Joseph Nilsen, Sebastien Hubert, Sylvie Jacquemot, Christian Remond, Remy Marmoret, Marta Fajardo, Philippe Zeitoun, Laurent Vanbostal, Ciaran L.S. Lewis, Marie Francoise Ravet, and Franck Delmotte, "Longitudinal coherence measurements of a transient collisional x-ray laser," Opt. Lett. 28, 2261-2263 (2003)