Chirped mirrors with low dispersion ripple

We demonstrate a chirped dielectric multilayer mirror (CM) with controlled reflectivity and dispersion in the wavelength range 760–840 nm. It exhibits a reflectivity of >99.9% and a mean group delay dispersion (GDD) of about -30 fs2 with a theoretical GDD ripple of less than 0.5 fs2 in the working spectral range. Deviations of the measured GDD from the calculated one are restricted to less than ± 3 fs2, limited by our measurement system. Simulations reveal that a dispersive delay line composed of 120 bounces off these mirrors introduces negligible distortion to a femtosecond pulse and largely preserves its contrast. The mirrors constitute an ideal tool for precision intracavity or extracavity dispersion control in the range of several thousand fs2, particularly if pulses with high contrast are to be generated.