Megawatt single mode femtosecond erbium fiber laser

High power femtosecond fiber laser systems typically rely on self-similar amplification, large scale chirped pulse amplification (CPA), or higher-order soliton pulse compression. In any of these system architectures the control or minimization of fiber nonlinearities is paramount. To date, the scalability of Er fiber lasers in particular has been limited due to their intrinsic anomalous dispersion (limiting self-similar amplification) and their small gain bandwidth (limiting CPA) whereas higher-order soliton compression generally limits pulse quality. Here, we address these limitations by enabling highly nonlinear pulse propagation in Er fiber amplifiers with minimal pulse distortions based on adaptive control of the input pulse. Though the system is subject to high levels of self-phase modulation, the output pulse quality remains high, moreover, the output bandwidth is greatly increased, easily surpassing the bandwidth limitation of classical CPA systems. Adaptive control is enabled via a compact adaptive chirped fiber Bragg grating (FBG) pulse shaper/stretcher, paired with a matched, static FBG compressor. We generate 110 nJ pulses, with a FWHM of 62 fs in a single mode Er fiber amplification system at a repetition rate of 99.8 MHz, corresponding to an average power of 11.0 W. This corresponds to a maximum peak power of 1.4 MW, which should yield focused intensities above 1 TW/cm2, providing the high intensity and repetition rate needed to combine strong-field effects such as high harmonic generation in solids with the precision of frequency combs. At a lower 25 MHz repetition rate, we reach 340 nJ, 63 fs.