Tungsten has been continuously excavated and explored to further its applications in the field of industrial and military, as a group ⅥB transition metal with an atomic number of 74....

Manganese (Mn), atomic number 25, belongs to Group VIIB in the Periodic Table and has high melting and boiling points. The hardness of Mn is slightly lower than that of iron, which exists widely in nature. Unlike the main-group elements, there is a paucity of research into the nonlinear optics of the subgroup elements. In this work, the broadband nonlinear absorption (NLA) properties of Mn nanosheets with average thicknesses of 5.0−11.0 nm were systematically analyzed using an open-aperture Z-scan technique for the first time as far as we know. The results show that Mn nanosheets exhibit excellent two-photon absorption (TPA) effects, i.e., optical-limiting (OL) behavior at the three wavelengths of 1064, 532, and 355 nm. In particular, the large TPA coefficient β of Mn nanosheets at 355 nm confirms the superior OL property in the ultraviolet region, which is promising for a wide range of applications in precision instrument and eye protection. This work will focus more on the NLA properties of transition metals.

Selenium (Se) is located in the fourth period of the periodic table in group VIA (element 34). In this experiment, three different solvents (isopropyl alcohol, N-methyl-2-pyrrolidone, and ethanol) were used to prepare the two-dimensional (2D) Se nanosheets, which were manufactured by the liquid phase exfoliation (LPE) method with a thickness of 3.35 ~ 4.64 nm and a transverse scale of several hundred nanometers. The nonlinear absorption (NLA) properties at 355, 532, and 1064 nm were studied using the open aperture Z-scan technique. Final results showed that Se nanosheets exhibited optical limiting (OL) effect in all three wavebands and three solvents, and had large two-photon absorption coefficients, especially in ultraviolet (UV) waveband. Which proved that Se nanosheets had great potential application as excellent OL materials in UV waveband. Our research broadens the path for the semiconductor field of Se, inspires the application of Se in nonlinear optics field.

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