Sub-250 fs passively mode-locked ultralong ring fibre oscillators

Abstract

We report the experimental demonstration of a simple passive ultrafast harmonically mode-locked ultralong ring fibre laser architecture using InN-based semiconductor saturable absorber mirrors (SESAMs) that allows for the generation of high peak power ultrashort pulses without the need for external amplification stages. Fundamental mode-locking of the resonator in 1.67 to 2.37 km rings, emitting at 1.56 μm results in pulse widths below 250 fs, with repetition rates between 87 and 124 kHz, pulse energies above 200 nJ and peak powers between 1.0 and 1.27 MW, that could meet the requirements for high peak power demanding applications such as materials processing without additional amplification or compression stages.