Ellipsoidal mirror for two-dimensional 100-nm focusing in hard X-ray region

• Published in: Scientific reports Vol. 7; no. 1; pp. 16408 - 9
• Main Authors: Yumoto, Hirokatsu, Koyama, Takahisa, Matsuyama, Satoshi, Kohmura, Yoshiki, Yamauchi, Kazuto, Ishikawa, Tetsuya, Ohashi, Haruhiko
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.11.2017; Nature Publishing Group
• Subjects: 639/166/988; 639/624/1107/328; 639/925/930/2735; Humanities and Social Sciences; Laser radiation; Manufacturing industry; Microscopy; Mirrors; multidisciplinary; Optics; Science; Science (multidisciplinary); X-rays
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-16468-1

Cutting-edge hard X-ray microscopy strongly depends on sophisticated focusing optics and ultrabright X-ray sources at synchrotron-radiation and X-ray free-electron laser (XFEL) facilities. These facilities typically provide two-dimensional nanofocusing X-ray beams by combining one-dimensional focusing mirrors. However, single-reflecting two-dimensional focusing mirrors with an ellipsoidal surface, which are well-known to possess high efficiency, have limited microfocusing applications. In this paper, we present an ultrahigh-precision ellipsoidal mirror for two-dimensional X-ray nanofocusing by overcoming the difficulties faced in the manufacturing process of its aspherical surface, including the surface-processing methods and surface metrology. The developed mirror has nanoscale accuracy, and it achieves focus size of 85 nm × 125 nm (full width at half maximum) using 7-keV X-rays. Two-dimensional focus was demonstrated in the same focal plane by resolving 50-nm test structures by scanning X-ray microscopy using a focusing beam. These achievements represent an important first step toward realizing two-dimensional aspherical mirrors with complex designs, in addition to ultralow loss and unprecedented small focusing property for extensive optical applications in synchrotron-radiation and XFEL facilities as well as in other scientific fields that require ultraprecision optical surfaces.