Narrowband Mg/SiC multilayer mirror working as high-harmonic selector at 30.4 nm wavelength

Abstract

Abstract Multilayers (MLs) are a good choice for high-harmonic generation (HHG) sources for selecting single-wavelength radiation. MLs working around 30.4 nm with a significantly reduced bandwidth based on high Bragg order reflection have been designed and fabricated. The narrowband MLs were characterized using grazing incidence x-ray reflectometry, extreme ultraviolet reflectivity, and intrinsic stress measurements. The results indicate that Mg/SiC MLs designed with 3rd Bragg order have narrowest bandwidth of 0.71 nm (full width half maximum) with a spectral resolution (λ/Δλ) of 42, and reflectance of 30% under near normal incidence geometry. Based on these results, the simulation of narrowband MLs working at large incident angles demonstrates that 3rd Bragg order ML has a better spectral selectivity compared with 1st Bragg order ML for HHG sources.