A thin-film reflecting interference filter has been designed and constructed for the purpose of suppressing grating harmonics when monochromatizing synchrotron radiation. It consists of a layer of Si evaporated onto a substrate and makes use of interference between wave fronts reflected from the layer-substrate and vacuum-layer interfaces to suppress higher harmonics. The filter has proved useful over the fundamental wavelength range of 400–1200 Å (~30-10 eV), maintaining a rejection ratio of fundamental to second harmonic exceeding 60. Calculations and measurements are presented, and the reflecting interference filter is compared with a critical-angle mirror used for the same purpose.
© 1994 Optical Society of America
W. R. Hunter and J. P. Long, "Thin-film interference mirror to suppress grating harmonics in vacuum-ultraviolet radiation," Appl. Opt. 33, 1264-1269 (1994)