  We report on an environmentally stable, Yb-doped, all-normal dispersion,
mode-locked fibre laser that is capable of creating broadband pulses with
ultra-low repetition rates. Specifically, through careful positioning of fibre
sections in an all-PM-fibre cavity mode-locked with a nonlinear amplifying loop
mirror, we achieve stable pulse trains with repetition rates as low as 506 kHz.
The pulses have several nanojules of energy and are compressible down to
ultrashort (< 500 fs) durations.
