Design of ultrabroadband double-chirped mirror pairs for ultrafast lasers

According to the requirements for design and manufacture, we choose double-chirped method for designing the initial structure of the chirped coatings, and analyze the dependencs of reflectivity and group delay dispersion on the parameters of coatings such as the double-chirped modulation factor and the the proportion of double-chirped layers on the total thin film stack. Further more, we establish their optimal values. Based on the analysis, a chirped mirror pair, whose reflectivity is more than 99.5% and average group delay dispersion is -40 fs 2 with a residual ripple of less than ± 20 fs 2 in a wavelength range of 600 nm-1050 nm, is demonstrated, which is to be used in the Ti: Sapphire femtosecond laser system for dispersion compensation.