Nonlinear optical properties and ultrafast carrier dynamics of ultrathin ReSe₂

Rhenium diselenide (ReSe₂) has shown great application potential in the field of optical devices because of its excellent optoelectronic properties. In this study, we systematically investigated the nonlinear optical absorption properties of mono- and bi-layer ReSe₂ and the ultrafast carrier dynamics process in the ultraviolet to near-infrared spectral range as the essential foundational groundwork for harnessing the potential of ultrathin ReSe₂-based optoelectronic devices. We found that ReSe₂ has excellent nonlinear absorption performance and a low saturation absorption intensity that is better than that of many semiconductor materials. Meanwhile, pump–probe and transient absorption technology revealed the underlying dynamic mechanisms, including bandgap renormalization and Auger recombination.