Imaging Beyond Optics
Important new information on methods for imaging the complex wave fields at the focus of x-ray zone plates without the need for conventional x-ray lenses has been obtained by researchers using the XOR beamline 2-ID at the Advanced Photon Source. The report of this discovery is the cover article for the February 2006 issue of Nature Physics, and is also the subject of a “News & Views” piece in that same issue.
“Generations of astronomers have used interferometric tests to achieve the proper shape of their mirrors before using them to image the heavens. Similar approaches are used to this day in the development of the optics for manipulating the extreme ultraviolet wavelengths (of the order of 13.5 nm) to reach the nanometre-resolution needed to fabricate the microchips of the next decade. Extending this approach still further to wavelengths beyond the ultraviolet will be vital … take full advantage of the intense, coherent X-ray beams generated by emerging radiation sources such as new-generation synchrotrons and free-electron lasers. Quiney et al. report encouraging progress in this endeavour by demonstrating an approach for measuring the focusing properties of an X-ray optical element, based on a simple measurement of the intensity far from the optic's focal plane, and using basic knowledge about the peripheral geometry of the optic. Because of the simplicity of their experimental setup, the method has no fundamental limits to its measurement resolution other than the wavelength of the X-rays used.”
— Chris Jacobsen, “Imaging at Arm’s Length,” News & Views, Nature Physics, Vol. 2, page 71.