Two-Dimensional Violet\nPhosphorus Nanosheets with\nExcellent Nonlinear Optical Properties for Ultrafast Lasers and Laser\nProtection

The violet phosphorus is a layered semiconductor material\npossessing\na diverse range of exceptional physical properties. Until now, the\nnonlinear optical properties of violet phosphorus nanomaterials have\nbeen relatively scarce, and most of them were limited in the exploration\nof one single wavelength. In contrast, our study was based on the\nbroadband nonlinear absorption characteristics of violet phosphorus\nnanomaterials from the ultraviolet to near-infrared waveband. In this\npaper, the two-dimensional violet phosphorus nanosheets were prepared\nby using the liquid-phase exfoliation method. The broadband (from\nultraviolet to near-infrared) nonlinear optical properties of the\ntwo-dimensional violet phosphorus nanosheets were investigated by\nthe open-aperture Z-scan method. And the band gap values of the two-dimensional\nviolet phosphorus were analyzed through experimental characterization\nand density-functional theory. The experimental results show that\nthe two-dimensional VP nanosheets exhibit saturable and two-photon\nabsorption. In the ultraviolet band, the two-dimensional violet phosphorus\nnanosheets exhibit the most excellent saturable absorption properties.\nThis work had important implications in the fields of ultrafast lasers,\nmicrofabrication, nanofabrication, and optical limiting fields.