FRINGE FORMATION AND COHERENCE OF A SOFT-X-RAY LASER-BEAM ILLUMINATING A MACH-ZEHNDER INTERFEROMETER

We investigated the fringe visibility produced by a Mach-Zehnder inter ferometer illuminated by a collisionally pumped yttrium x-ray laser op erating at 15.5 nm. Fringe visibility varied as a function both of rel ative path delay and of relative spatial overlap of the beams. This vi sibility information was extracted quantitatively from several interfe rograms and analyzed to produce a characterization of the temporal coh erence, yielding a gain-narrowed linewidth of 1.3 pm for the 15.5-nm l aser transition and spatial coherence consistent with an effective sou rce size of approximate to 220 mu m +/- 50% at the x-ray laser output. (C) Optical Society of America