Q-switched and vector soliton pulses generation in an Er-doped fiber laser mode-locked by the PbSe-QDs saturable absorber

PbSe quantum dots (QDs) have demonstrated excellent optical properties suitable for high-performance lasers and stable pulse generation. Here, we present an all-fiber laser cavity operating at 1.5-μm with a homemade sandwiched PbSe saturable absorber (SA), which enables stable high-energy pulses both in Q-switching and mode-locking operations. Notably, we report, for the first time, the generation of polarization-locked vector solitons (PLVSs) using a PbSe-QDs-based SA in the mode-locking regime. In the Q-switching operation, the repetition rate could be tuned from 12.48 kHz to 35.25 kHz by adjusting the pump power, yielding a maximum pulse energy of 208 nJ with a pulse width of 2.81 μs at the pump power of 183 mW. This represents the best performance reported to date for PbSe-QDs SAs. In the mode-locking regime, the PbSe-QDs SA also exhibited outstanding performance in generating ultrashort pulses, producing soliton pulses with a repetition rate of 28.51 MHz, an average output power of 26.80 mW, and a pulse duration of 673 fs. Further detailed characterization confirmed that these solitons are indeed PLVSs, marking the first realization of vector solitons with the PbSe-QDs SA. Moreover, the PbSe-QDs SA demonstrated excellent long-term stability in the constant mode locking over 6 h with a power fluctuation around 0.15%. These results highlight the exceptional optical properties of PbSe QDs and unambiguously imply the potential as a high-performance SA for applications in ultrafast optics, nonlinear photonics, optical modulators and related fields.