Gallium Sulfide and Gallium Selenide Nanosheets for Ultrafast Lasers and Optical Limiting

Transition-metal gallium sulfide (GaS) and gallium selenide (GaSe), which belong to the binary IIIA–VIA group of compounds, have garnered significant attention, primarily due to their distinctive optoelectronic properties. In this study, GaS and GaSe nanosheets were synthesized using the liquid phase exfoliation method, and their nonlinear absorption characteristics from ultraviolet to near-infrared spectral ranges were investigated through open-aperture Z-scan measurements. The results revealed that GaS and GaSe nanosheets exhibited versatile nonlinear properties in various wavebands. Specifically, they both possessed exceptional nonlinear absorption properties in the ultraviolet band. Furthermore, GaS nanosheets exhibited superior two-photon absorption behavior at 1064 nm and outstanding saturation absorption property at 355 nm compared with the same excitation of GaSe nanosheets. These versatile nonlinear properties highlight the substantial potential of layered GaS and GaSe nanosheets in driving the progression of sophisticated nanophotonic devices, including mode-locking in the ultraviolet waveband and optical limiters in the infrared waveband.