All-fiber ytterbium femtosecond laser without dispersion compensation.

We report on an all-fiber femtosecond ytterbium laser without dispersion compensation consisting of all-normal dispersion fibers. Mode-locking was achieved by nonlinear polarization evolution in combination with additional amplitude modulation generated by a fiber-based spectral filter. The generated pulses were highly chirped and had a maximum pulse energy of 1.8 nJ. The output pulse duration was 7.6 ps and could be dechirped to 179 fs.