PbS Nanoparticles for Ultrashort Pulse Generation in Optical Communication Region

Lead sulfide (PbS) has attracted great attention due to its unique electronic, optical, and chemical properties. In particular, the narrow bandgap of PbS (approximate to 0.37 eV) makes it very suitable for the ultrafast application in optical communication or even longer wavelength region. In this work, PbS nanoparticles' (NPs) dispersion without any polymer is utilized as saturable absorber (SA) to generate ultrafast pulse in a fiber ring laser for the first time. The characterization and nonlinear properties of PbS NPs are investigated experimentally. PbS NPs are deposited on a flange to compose a nonlinear device. The nonlinear absorption is measured by a power-dependent method with a modulation depth of 12.2%. Most importantly, PbS NPs can be applied for the ultrafast photonics applications. A compact mode-locked fiber laser with 1.01 ps pulse duration, 2.93 nm spectral width, and 3.97 MHz repetition rate at 1533 nm is successfully achieved with long time stability. The output laser is detected with a good stability for more than 1 month without any degradation. This work can demonstrate that the PbS NPs' dispersion is indeed a new and excellent photonics material for SA photonics, photoconductive detection, and optical modulator, etc.