Novel diffractive optics for x-ray beam shaping

Abstract

In our days, there is an increased interest for extreme ultraviolet and x-ray microscopy, which is mainly due to the availability of nearly ideal optical sources for diffractive optics. Synchrotrons of the latest generation and free electron lasers (in the near future) are sources that can produce x-ray beams with low divergence, whose wavelength can be tuned over a range of several keV and whose spectrum can be monochromatised within a band pass Δλ/λ< 10-4. In this paper we present the design, fabrication and use of novel diffractive optical elements that, beyond simple focusing, can perform new optical functions in the range of soft X-rays: multi-focusing in single or multiple focal planes and beam shaping of a generic monochromatic beam into a desired continuous geometrical pattern. The design is based on scalar diffraction approaches using iterative or direct algorithms to calculate the optical function. Diffractive optical elements with 100x100 microns size and 100 nanometers resolution have been fabricated using e-beam lithography and their optical functions have been tested in differential interference contrast microscopy. We suggest their use also in mask-less lithography and chemical vapor deposition induced by extreme ultraviolet and x-ray radiation.