Single- and multi-soliton generation in figure-eight mode-locked fibre laser with two active media

We present a study of generation of a figure-eight mode-locked all-PM fibre laser having two independently pumped active media in each loop of the cavity under varied power level of both pump sources. Controllable and reproducible generation of 1- to 7-picosecond solitons per cavity round trip is demonstrated, as well as the possibility of soliton peak power and energy adjustment in a pre-determined passively mode-locked regime. Salient features are identified of transition among regimes with different soliton count, including those generating Raman solitons. The studied all-fibre laser system makes it possible to reproducibly generate pre-determined soliton molecules with variable energy. Such a fibre-optical system may be widely used as a seed generator of electronically controlled bursts of picosecond solitons with nanosecond inter-pulse delays.