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In femtosecond lasers,solid-state gain media and other optical components(such as output couplers)always introduce a certain amount of frequency-dependant positive dispersion in the cavity.Femtosecond-pulse generation mainly depends on the performance of dispersion compensation in the cavity.Multilayer thin film mirrors(Gires-Tournois mirrors and chirped mirrors)are employed to compensate the dispersion of materials used in femtosecond(fs)lasers for generating gain such as Ti:sapphire,Cr:LiSAF and Cr:LiCAF,which enables the intracavity dispersion being controlled.Besides,low-dispersion output couplers will be demanded.In this paper,a low-dispersion output coupler which is designed with similar design method of chirped mirrors is reported.The initial layer thickness of the output coupler relies on the superimposing a quasi-periodic modulation on a linear variation of the optical thickness of the layers.It is composed of 40 alternating Ta2O5 and SiO2 layers whose thicknesses are obtained by computer optimization to minimize group delay dispersion.The optimized output coupler exhibits continuous low transmittance of 2%and nearly zero group delay dispersion from the wavelength of 750nm to the wavelength of 900nm,which can meet the need of Cr:LiSAF lasers.