X-RAY FRAUNHOFER-DIFFRACTION PATTERNS FROM A THIN-FILM WAVE-GUIDE

We have observed the Fraunhofer diffraction pattern of x-rays exiting from the end face of a SiO2/polyimide/Si thin-film waveguide. The meas ured angular intensity distributions are in excellent agreement with t hose calculated based on the dimensions and the refractive index profi le of the guide. Our measurement confirms that, at the end face of the guide, the wavefront of a single guided mode is fully coherent in the direction normal to the guiding plane. This focused and transversely coherent x-ray beam may be used as a source for coherence-based experi ments, such as x-ray photon correlation spectroscopy. (C) 1995 America n Institute of Physics.