Planar parabolic refractive lenses for hard x-rays: technological aspects of fabrication

Abstract

Planar parabolic refractive lenses are becoming the key optical elements for many hard x-ray microprobe and microscopy applications at third generation synchrotron radiation sources (e.g. the ESRF), as well as they are promising candidates for future X-ray free-electron lasers. In this paper we review all technological limitations taking place during fabrication of silicon and non-silicon refractive lenses and propose some approaches to overcome these limitations in order to fabricate high performance refractive lenses in terms of aperture, gain and focal spot size etc. We propose to use low-temperature silicon bonding techniques as alternative for very deep etching. Combination of two etched silicon structures by bonding of two lenses with relief to relief doubles the lens relief depth.