Grating monochromators for the spectral selection of femtosecond extreme-ultraviolet pulses

The design of grating monochromators for the spectral selection of extreme-ultraviolet femtosecond pulses without altering significantly the pulse time duration is discussed here. Time-preserving monochromators are realized in a single-grating configuration if the number of illuminated grooves is minimum for a given spectral resolution; therefore the grating time response is close to the Fourier limit for such a resolution. The classical-diffraction mount and the off-plane mount are compared for applications in the extreme-ultraviolet region—the classical mount should be preferred for monochromators with time responses in the 100–200 fs range, while the off-plane mount gives responses in the 10–50 fs range, and is therefore suitable to realize femtosecond time-preserving monochromators.