All-optical valley regulator based on nonlinear parametric scattering in monolayer transition metal dichalcogenides...

In the field of valleytronics, significant advancements have been made in valley manipulation in linear optical processes. However, the exploration of relevant nonlinearity is crucial for developing coherent optical sources and signal processing in on-chip photonic devices, yet it remains relatively underexplored. Here we demonstrate all-optical valley regulation by leveraging nonlinear parametric scattering processes within monolayer transition metal dichalcogenides embedded in a semiconductor microcavity. Specifically, by utilizing three excitation laser beams (signal, pump, and idler lasers), we observe that the signals from both valleys can be synchronously amplified or suppressed by adjusting the phase of the pump laser. Remarkably, we can independently and effectively control the signals from each valley, with the amplification or suppression of either valley being regulated by the degree of circular polarization or phase difference between circularly polarized components of the pump laser. These advancements in all-optical valley manipulation deepen the understanding of nonlinear optical processes and thus facilitate their potential applications in opto-valleytronic devices.