The design of grating-based instruments to handle and condition coherent ultrafast\npulses in the extreme-ultraviolet is discussed. The main application of such instruments is the\nmonochromatization of high-order laser harmonics and free-electron-laser pulses in the femtosecond\ntime scale. Broad-band monochromators require the use of diffraction gratings at grazing incidence.\nA grating can be used for the spectral selection of ultrashort pulses without altering the pulse duration\nin a significant way, provided that the number of illuminated grooves is equal to the resolution.\nWe discuss here the design conditions to be fulfilled by a grating monochromator that does not\nincrease the pulse duration significantly longer than the Fourier limit.
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