Fabrication technology and applications of zone plates

The focusing properties of zone plates have a long history spanning over a century. The fabrication technology has continually improved and has made significant advances in the last decade so that zone plates now can be fabricated with the smallest zone widths of several tens of nanometers and near diffraction limited performance. This paper reports that for applications such as x-ray microscopy, these high resolution zone plates allow the possibility of observing biological samples in a natural , i.e. wet, environment with resolution an order of magnitude better than optical microscopy. In addition to microscopy, zone plates are critical to many x-ray applications where the focusing, imaging, and dispersive properties can be put to use. The key challenges for making better zone plates are to improve the efficiency and resolution while maintaining comfortable working distances and extend the wavelength range available. In order to meet these challenges, refinements in zone plate fabrication technology, better line placement distortion measurement/control techniques, and new processing ideas are under development