Low Threshold and High Power Fiber Laser Passively Mode-Locked Based on PbSe Quantum Dots

PbSe quantum dots (QDs), zero-dimensional IV–VI semiconductor material, have been extensively studied in materials science, chemistry, and physics, while their applications in ultrafast optics are uncommon. Herein, PbSe QDs with an average diameter of 4.8 nm are synthesized using a hot-injection method. The nonlinear optical properties of PbSe QDs are investigated, demonstrating a modulation depth of 8.8% and a saturable intensity of 0.1 MW/cm2. Subsequently, PbSe QDs are employed as a saturable absorber (SA) in an erbium-doped fiber laser (EDFL). Ultrafast pulse with a low self-starting threshold of 5 mW is generated. Moreover, by increasing the pump power to 850 mW, the laser achieves a maximum average output power of 73 mW, accompanied by a signal-noise ratio of 66 dB, a pulse width of 0.86 ps, a spectral bandwidth of 3.45 nm, and a center wavelength of 1560 nm. This is the first demonstration, to the authors’ knowledge, of using QDs as a SA to generate ultrafast lasers with low self-starting threshold and high output power. Consequently, this study opens new possibilities for the fascinating applications of PbSe QDs in high-performance ultrafast optoelectronic devices.