Mode-locked Yb-doped large-mode-area microstructure fiber laser

We report on an all-normal dispersion passively mode-locked fiber laser based on an ytterbium-doped large-mode-area microstructure fiber and featuring high-energy ultra-short pulses. Mode-locking was achieved with a high modulation depth semiconductor saturable absorber mirror (SESAM). We investigate the influence of the modulation depth of the SESAM on the laser performances. We show that, mode-locking could be achieved with a modulation of only 10%. However, the best performances in term of pulse energy are obtained with the highest modulation depth (35 %). In this case, the laser delivers 3.3 W average output power with positively-chirped 5.5 ps pulses at a center wavelength of 1033 nm. The pulse repetition rate is 46.4 MHz, which results in an energy per pulse of 71 nJ. These pulses are extra-cavity de-chirped down to 516 fs using bulk gratings. The average power of the de-chirped pulses is 2.3 W, which corresponds to a peak power of more than 96 kW.