Aperiodic normal-incidence antimony-based multilayer mirrors in the 8 - 13-nm spectral range

摘要

The optical properties of several materials were analysed from the standpoint of fabrication of broadband normal-incidence multilayer mirrors possessing maximal uniform reriectivity in the 8 - 13-nm range. By solving the inverse problem of multilayer optics we show that aperiodic Sb/(B_4C, Sc, Si) multilayer structures optimised for max- imum uniform reriectivity in the 8 - 13-nm range are able to afford a normal-incidence reriectivity R ～ 10% throughout this range. The best results are exhibited by the pair Sb/B _4C, for which the average reriection coefficient amounts to about 13 %. The dependence of optimisation result on the program- mable limitation on the minimal layer thickness in the multilayer structure was numerically investigated. An empirical rule was established whereby setting the lower bound for a layer thickness at a level ～ γ_(min)=4 (in this case, γ_(min) . 8 nm) does not result in an appreciable lowering of attainable uniform reriectivity.