High-quality X-ray optics characterization using advanced at-wavelength metrology*

The availability of advanced at-wavelength characterization tools and methods is critical to develop and fabricate the high-quality focusing optics required to achieve diffraction-limited focusing in many instruments deployed at modern X-ray light sources. Existing methods, such as X-ray grating-based interferometry, suffer from low sensitivity and low spatial resolution. Here, we describe a new method, based on coded phase masks and called CMMI [1], that allows one to characterize focusing optics with high sensitivity and excellent spatial resolution, which could be also used in many imaging applications. We used CMMI to characterize polymer-based lenses designed as a high-magnification objective in a full-field X-ray microscope [2]. The measured phase wavefront shows that polymeric lenses with a short focal length have phase errors and aberrations comparable to those of state-of-the-art beryllium lenses. The data can be used to fabricate phase correctors to compensate for phase aberrations and achieve near-ideal focusing.

1. Z. Qiao, X. Shi, M. J. Wojcik, L. Rebuffi, and L. Assoufid. Appl. Phys. Lett. 119, 011105 (2021).

2. Z. Qiao, X. Shi, P. Kenesei, A. Last, L. Assoufid, and Z. Islam. Rev. Sci. Instrum. 91, 113703 (2020).