Tunable spatiotemporal mode-locked conventional soliton and soliton molecule in a partial multimode linear-cavity Er-doped fiber laser

Abstract

In this letter, we have demonstrated the realization of wavelength-tunable spatiotemporal mode locking (STML) in a partial multimode fiber (MMF) laser with a linear cavity. The saturable absorption effect is attributed to both the nonlinear multimode interference (NL-MMI) and the nonlinear optical loop mirror (NOLM). The laser can deliver both the conventional solitons (CSs) and loosely bound solitons (BSs) with a tuning range from ∼1573 nm to ∼1601 nm. The evolutions of these two different STML solitons as the pump power are also given and it is found that the interaction between solitons would have notable affection on the beam distribution of the MM solitons. Furthermore, a spatial instability for the STML CSs is observed within a certain pump power range. These results contribute to our understanding of the nonlinear spatiotemporal dynamics in the MMF laser system.