Monolithic X-ray achromat

Abstract

X-ray imaging techniques employing diffractive and refractive lenses face the challenge of chromatic aberration if X-ray beams with a broad photon energy range are used. Recent advances combining a compound refractive lens and a Fresnel zone plate have enabled the development of achromatic lenses for X-rays, which exhibit a constant focal length over a wider range of photon energies. However, in this first demonstration, the potential of the achromatic X-ray lens was limited by the challenging task of aligning the two individual separate components. In this investigation, we designed, fabricated, and characterized monolithic X-ray achromatic lenses by integrating a Fresnel zone plate and a compound refractive lens onto a single substrate. This innovative approach inherently achieves precise alignment during fabrication, greatly simplifying and stabilizing the alignment for the X-ray imaging setups. Benefiting from an increased numerical aperture, the reported monolithic lens demonstrated state-of-the-art achromatic focusing down to approximately 200 nm for photon energies ranging from 6.6 keV to 7.7 keV. With these advancements, we present the first successful application of an achromatic lens in scanning and full-field transmission X-ray microscopy, as well as fluorescence spectroscopy, highlighting its potential for broad adoption across diverse X-ray imaging applications.