Single-polarization large-mode-area fiber laser mode-locked with a nonlinear amplifying loop mirror.

The generation of high-power ultrashort pulses from a passively mode-locked fiber laser is reported based on the combination of a single-polarization large-mode-area (LMA) photonic crystal fiber with a nonlinear amplifying loop mirror design. The introduction of a non-reciprocal phase shift in the loop mirror enables self-starting of the mode-locked laser, while the polarizing LMA fiber supports environmentally stable high-power operation. Mode locking in the soliton-like, stretched-pulse, and all-normal-dispersion regime is characterized. The laser generates stable pulses with up to 2 W average power at a 72 MHz repetition rate, corresponding to a single-pulse energy of 28 nJ. The output pulses are dechirped to a near transform-limited duration of 152 fs. The proposed fiber oscillator presents an alternative approach to high-power ultrafast laser sources, along with environmental stability.