Time-compensated EUV and soft X-ray monochromator for ultrashort high order harmonic pulses

The optical design of a time-compensated monochromator for high-order harmonic pulses in the extreme-UV (EU-V) and soft x-ray regions is presented. The system consists of two grazing-incidence mirrors used as collimating and refocusing elements and two multilayer normal-incidence plane mirrors illuminated in parallel light that rotate along a vertical axis parallel to their planes to select the wavelength, and remain parallel to guarantee the constant direction of the exit beam: this is performed by rotating and translating, at the same time, one of the two mirrors along an axis parallel to the exit direction. The system has constant exit direction in the whole working spectral region. The pulse time duration is not altered up to few femtoseconds. A system operating in the 9-32 nm region is described.