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. This study can broaden the horizons of material science and propel the development of different applications of ReSe₂.