Layered iron pyrite for ultrafast photonics application

Two-dimensional (2D) transition metal dichalcogenide materials have attracted much attention in recent years due to their excellent electro-optical properties. FeS2, the ideal composition of iron pyrite, is a 2D transition metal dichalcogenide which has been potentially used in the electronic, optical, and chemical fields. On the other hand, the narrow band gap of FeS2 (approximate to 0.96 eV) makes it very suitable and promising for the ultrafast application in near-infrared regimes. However, the potential application of FeS2 in laser technology has not been explored till now. Ultrashort pulse lasers have great applications in industry and science because of its stability, ease of operation, and portability. Passively mode-locked fiber lasers using 2D materials (such as MoS2, CuS2, and WS) as saturable absorber are intensively investigated. Here, layered FeS2 has been characterized systematically. It is successfully applied in ultrafast photonics and plays a key component in the passively mode-locked laser for the first time. The single pulse can be obtained with 1.7-ps pulse duration, 1.89-nm spectral width, and fundamental repetition of 6.4 MHz at 1563 nm central wavelength. Through controlling the pump power, the evolution of the pulse train can be observed, which can be transformed from single pulse to bound states. Also, the harmonic mode-locked fiber laser is observed with the pump power high enough.