Controllable nonlinear optical properties of different-sized iron phosphorus trichalcogenide (FePS3) nanosheets

Two-dimensional iron phosphorus trichalcogenide (FePS 3 ) has attracted significant attention for its use in electricity, magnetism and optical fields due to its outstanding physical and chemical properties. Herein, FePS 3 was prepared using the chemical vapor transportation (CVT) method and then exfoliated by using fast electrochemical exfoliation. After gradient centrifugation, FePS 3 nanosheets with thicknesses ranging from 1.5 to 20 nm and lateral dimensions of 0.5–3 μm were obtained. By utilizing the spatial self-phase modulation (SSPM) effect, the relationships between the nonlinear refractive index and the size of the FePS 3 nanosheets were investigated in detail which revealed that the nonlinear refractive index can be effectively controlled by the size of the FePS 3 nanosheets. It is worth noting that the optimal FePS 3 nanosheets (3–5 layers thick and ∼1 μm in lateral dimensions) displayed the highest nonlinear refractive index of ∼10 −5  cm 2  W −1 . This work demonstrates the potential that FePS 3 nanosheets have for use in nonlinear optics or nonlinear optical devices.