Phase and intensity control through diffractive optical elements in X-ray microscopy

Abstract

Diffractive optics now plays a major role in optical systems for the extreme ultraviolet and X-ray region. For example, zone plates in their different appearances are widely used for focusing X-rays, as monochromatizing condenser optics, and for high resolution imaging, particularly in X-ray microscopy. The idea in this paper is based upon a more general approach to solve optical problems by transforming a given light distribution or wave as input into the desired waveform on the output of a single X-ray optical component. In this paper we present the design, fabrication and use of novel phase diffractive optical elements (DOEs) that, besides simple focusing, can perform new optical functions in the range of X-rays. Using our own code, we calculated and fabricated through e-beam and X-ray lithography high-resolution DOEs that can generate a constant intensity on a plane (top-hat DOE) or focus a monochromatic X-ray beam into multiple spots. The possibility to introduce a specified phase shift between the generated spots, which can increase the image contrast, is demonstrated by experimental results obtained from computer simulations and experiments performed between 3 and 7.2 keV in both full-field and scanning X-ray microscopy at the ID21 beamline of the European Synchrotron Radiation Facility (ESRF).