We present what we believe is a novel technique based on the moiré effect for fully diagnosing the beam quality of an x-ray laser. Using Fresnel diffraction theory, we investigated the intensity profile of the moiré pattern when a general paraxial beam illuminates a pair of Ronchi gratings in the quasi-far field. Two formulas were derived to determine the beam quality factor M2 and the effective radius of curvature Re from the moiré pattern. On the basis of the results, the far-field divergence, the waist location, and the radius can be calculated further. Finally, we verified the approach by use of numerical simulation.
© 1999 Optical Society of America
[Optical Society of America ]
(120.4120) Instrumentation, measurement, and metrology : Moire' techniques
(140.0140) Lasers and laser optics : Lasers and laser optics
(140.7240) Lasers and laser optics : UV, EUV, and X-ray lasers
(340.0340) X-ray optics : X-ray optics
Jun Yang, Dianyuan Fan, Shiji Wang, and Yuan Gu, "Technique for diagnosing x-ray laser beam quality by use of the moiré signal," J. Opt. Soc. Am. A 16, 323-330 (1999)