Femtosecond fiber laser at 780 nm for two-photon autofluorescenc...

We present an Er-doped fiber (Er:fiber)-based femtosecond laser at 780?nm with 256?MHz repetition rate, 191?fs pulse duration, and over 1?W average power. Apart from the careful third-order dispersion management, we introduce moderate self-phase modulation to broaden the output spectrum of the Er:fiber amplifier and achieve 193 fs pulse duration and 2.43?W average power. Over 40% frequency doubling efficiency is obtained by a periodically poled lithium niobate crystal. Delivering through a hollo