Design of a time-compensated EUV and soft X-ray monochromator with multilayer mirrors for high-order harmonics

A time-compensated monochromator for ultrashort high-order harmonics in the EUV and soft X-ray regions is presented. The system consists of two grazin g-incidence toroidal mirrors used, respectively, as collimating and refocus ing elements and of two multilayer normal-incidence plane mirrors illuminat ed in parallel light that rotate along a vertical axis to select the operat ive wavelength, but remain parallel to guarantee the constant direction of the exit beam. This is performed by simultaneously rotating and translating one of the two mirrors along an axis parallel to the exit direction. The p ulse rime duration is not altered up to few femtoseconds.