We have prepared the graphene/MoS2 heterostructure by a hydrothermal method, and presented its nonlinear absorption parameters and application as a nonlinear optical modulator in the mid-infrared region. Using the nonlinear optical modulator, stable passively Q-switched operation of an Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser at ～2.8 μm can be obtained. The Q-switched Er3+-doped ZBLAN fiber laser can yield per-pulse energy up to 2.2 μJ with the corresponding pulse width and pulse repetition rate of 1.9 μs and 45 kHz, respectively. Our results indicate that the graphene/MoS2 heterostructure can be a robust optical modulator for pulsed lasers in the mid-infrared spectral range.

We experimentally investigated the nonlinear optical response in few-layer oxidized black phosphorus (OBP) by the femtosecond Z-scan measurement technique, and found that OBP not only possesses strong ultrafast saturable absorption but also a nonlinear self-defocusing effect that is absent in black phosphorus (BP). The saturable absorption property originates mainly from the direct band structure, which is still maintained in OBP. The emergence of self-defocusing might originate from the combined consequences of the oxygen-induced defects in BP. Our experimental findings might constitute the first experimental evidence on how to dynamically tuneits nonlinear property, offering an inroad in tailoring its optical properties through chemical modification (oxidation, introducing defects, etc.). The versatile ultrafast nonlinear optical properties (saturable absorption and self-defocusing) imply a significant potential of the layered OBP in the development of unprecedentedoptoelectronic devices, such as mode lockers, optical switches, laser beam shapers, and wavelength converters.China Postdoctoral Science Foundation (2015M580731); Science and Technology Planning Project of Guangdong Province (2016B050501005).