Diffraction limited X-ray optics: technology, metrology, applications

Progress in the fabrication technology of normal incidence multilayer interference mirrors permits the traditional optical methods of microscopy, astronomy, and lithography to be transferred to the vacuum ultraviolet (VUV, wavelength: 10–200 nm) and the long-wavelength part of the soft X-ray (SXR, wavelength: 2–10 nm) ranges. Due to the short wavelength and properties of interaction with the substance, the radiation of these ranges provides unique opportunities in nanophysics, nanotechnology, and nanodiagnostics of matter. To use the potential of a short wavelength in full, diffraction-limited optical elements are required. Compared to traditional optical elements, their accuracy must be at least two orders of magnitude higher. The article provides an analysis of the real capabilities of traditional methods of making and studying precision optical elements and reports on the methods of fabrication and characterization of diffraction-limited optics for the VUV and SXR ranges developed at IPM RAS. Examples of the use of these optical elements for the tasks of extraterrestrial astronomy, X-ray microscopy, and lithography are given.