Broadband extreme ultraviolet multilayer mirror for supercontinuum light at a photon energy of 35-65 eV.

We have developed a broadband multilayer mirror for photon energies between 35 and 65 eV. This extreme ultraviolet (EUV) mirror has an almost flat reflectivity profile at normal incidence, and the average reflectivity is 8%. The bandwidth of this mirror is 30 eV centered around 50 eV, 1.5 times broader than conventional multilayer mirrors in this energy region. This new mirror can be used in a variety of applications using supercontinuum EUV light sources including attosecond metrology.