Silver sulfide nanoparticles as nonlinear optical modulators for Q-switching and Mode-locking at 2 m

Silver sulfide (Ag2S), as a kind of transition metal chalcogenide, has been verified to possess the ability of nonlinear modulation at 1560 nm and attracted enormous attention. However, there are few reports of pulsed lasers produced by Ag2S NPs in the 2 & mu;m band. In this work, Q-switching and mode-locking operating at 2 & mu;m were achieved firstly using Ag2S nanoparticles (NPs) as saturable absorbers (SAs). The preparation of Ag2S NPs with a size of 20 nm was realized through a hydrothermal method. Firstly, Q-switched lasers could be achieved with a central wavelength of 1940 nm using Ag2S film as SA. Interestingly, Ag2S NPs deposited onto D-shaped fiber (DF) was placed into Tm3+-doped fiber laser cavities, and the mode-locked laser with a central wavelength of 1880 nm was generated. These experimental results verified that the nonlinear optical modulators based on Ag2S NPs were necessary optical devices for ultrafast photonics.