Tolerances of time-delay-compensated monochromators for extreme-ultraviolet ultrashort pulses

Time-delay-compensated grating monochromators for the spectral selection of extreme-ultraviolet femtosecond pulses in a broad spectral region are designed by adopting both classical diffraction and the off-plane mount. The optical design requires six optical elements: four concave mirrors and two plane gratings. I compare here the two designs in terms of the tolerances in the alignment for time-delay compensation in the femtosecond time scale. The off-plane mount is demonstrated to be far superior to the classical diffraction mount.