Enhanced four-wave mixing process near the excitonic resonances of bulk MoS2

Two-dimensional materials are generating great interest due to their unique electrical and optical properties. In particular, transition metal dichalcogenides such as molybdenum disulfide (MoS2) are attractive materials due to the existence of a direct band gap in the monolayer limit that can be used to enhance nonlinear optical phenomena, such as Raman spectroscopy. Here, we have investigated four-wave mixing processes in bulk MoS2 using a multiplex coherent anti-Stokes Raman spectroscopy setup. The observed four-wave mixing signal has a resonance at approximately 680 nm, corresponding to the energy of the A excitonic transition of MoS2. This resonance can be attributed to the increased third-order nonlinear susceptibility at wavelengths near the excitonic transition. This phenomenon could open the path to using MoS2 as a substrate for enhancing four-wave mixing processes such as coherent anti-Stokes Raman spectroscopy. (C) 2019 Chinese Laser Press