Calculated performance of multilayer Laue lens based on actual layer thickness and coupled wave theory

Abstract

The multilayer Laue lens (MLL) is a promising optical element with large numerical aperture and aspect ratio in synchrotron radiation facility to focus hard x-ray to 1 nm with ideal structure. We use a new method of combining actual film thickness and the coupled wave theory to calculate focusing performance. Here, a 17.2-μm-MLL with a focal spot size of 17 nm at 10 keV is designed and fabricated by dynamical diffraction theory and direct current magnetron sputtering technology. Based on a new rate calibration and symbol layer insertion method, we calculate d-spacing of multilayer instead of individual layer thickness and change the order of two layers as a symbol so as not to damage zone plate law. The scanning electron microscope image is smoothed and binary transformed to measure the actual thickness of each layer. The full-width at half-maximum of focus spot is 18 nm, which is close to the theoretical result of 17 nm.