Rapid nonlinear imaging spectroscopy for advanced material characterization

2D materials are a promising material platform for quantum information science, photovoltaics, and related device applications. However, it is important to distinguish between the intrinsic properties of these materials and properties due to extrinsic effects such as defects, inhomogeneity, or strain.

Here, we demonstrate nonlinear imaging spectroscopy of 2D materials that assesses the quality of samples through measurement of their nonlinear response, exciton dephasing, and exciton lifetimes. We use an exfoliated MoSe₂ monolayer, chemical-vapor-deposition-grown WSe₂ monolayer, and exfoliated MoSe₂/WSe₂ heterostructure as canonical examples to demonstrate these capabilities.

By comparison, we show that extracting material parameters such as four-wave mixing (FWM) intensity, dephasing times, excited state lifetimes, exciton-coupling strength, and distribution of dark/localized states allows for a more accurate assessment of the quality of a sample than current prevalent techniques, including white light microscopy, linear micro-reflectance spectroscopy, and photo-luminescence. In addition, we highlight the sensitivity of spatial and temporal coherence toward strain while coherent exciton coupling and charge transfer in these samples remain mostly unaffected.