High-repetition-rate, stretch-lens-based actively-mode-locked femtosecond fiber laser.

We propose and demonstrate a novel actively mode-locked fiber laser based on a stretch-type time-lens. The pulse generated by this scheme has high repetition rate and large bandwidth while no nonlinearity is participated. A 10-GHz chirped pulse train with 18-ps duration and 11.6-nm bandwidth is obtained, which is then extra-cavity compressed down to 825 fs. The pulse characteristics dependent on the cavity dispersion and time-lens strength are discussed. Pulse propagation in the laser is similar with dissipative soliton in all-normal-dispersion laser. The results demonstrate that the stretch-lens inside the actively mode-locked laser can effectively broaden the spectral bandwidth, instead of the fiber nonlinearity, which can then support a high-repetition-rate "linear dissipative soliton" pulse shaping in a very compact design.