Interferometry Based EUV Spectrometer

A compact and wavelength-calibration-free interferometric scheme was numerically and experimentally investigated using an extreme ultraviolet (EUV) source generated by a laser-produced plasma. A Michelson-type interferometer with a common path, formed by a Si/Mo-multilayer-based beam splitter and mirror, was utilized to achieve system compactness. Based on the Wiener-Khinchin theorem, an accurate EUV spectrum was obtained by numerically analyzing the measured signal autocorrelation without performing wavelength calibration. The achieved spectral resolution of 30 pm was comparable to those of flat-field spectrometers. Various high-oxidation states of Sn and the residual O in the vacuum chamber were also successfully identified.