High-Power Mode-Locked Fiber Laser Using Lead Sulfide Quantum Dots Saturable Absorber

The discovery of different types of nanomaterials including the one-dimensional and two-dimensional materials used as saturable absorbers (SAs) in the applications of ultrafast lasers in recent years increases the ultrafast laser design flexibility and boosts the laser performances. A major research avenue is to explore the potential of nanomaterials for further enhancing the performances of ultrafast lasers in terms of pulse power. To this aim, in this study, using a hot-injection method and drop-coating technology, a fiber-based lead sulfide quantum dot (PbS QD) is synthesized, and its potential as a SA for the generation of higher-power pulses is demonstrated in an erbium-doped fiber laser (EDFL). Experimental results show that the optical damage threshold of the SA is greater than 152.6 mJ/cm ² , and the modulation depth is up to 29.5%. The implementation of the PbS QD as a SA placed in an EDFL enables the laser to yield 2.84 ps ultrashort pulses with an average output power of 59.4 mW at a repetition rate of 6.97 MHz. To the best of our knowledge, it is the highest average output power obtained in ultrafast fiber lasers mode-locked by zero-dimensional QD materials. The results suggest the great potential of PbS QDs in the application that requires the generation of high-power pulses in ultrafast lasers.