Compact µJ-level all-polarization maintaining femtosecond fiber source

We report on a high power, high-energy femtosecond fiber source based on direct amplification of parabolic pulses from an environmental stable passively mode-locked fiber oscillator in an Yb-doped single-polarization photonic crystal fiber. The system delivers a pulse energy of 1.2 ?J (21 W average power) at a repetition rate of 17 MHz and a pulse duration of 240 fs in a linearly polarized beam with diffraction-limited quality. The special pulse shape allows for the generation of high quality femtosecond pulses beyond nonlinearity limits, which is confirmed by numerical simulations.