Steering Nonlinear Chiral Valley Photons Through Optical Orbit–Orbit Coupling

Abstract

Two-dimensional transition metal dichalcogenides feature a direct tunable bandgap and robust spin-valley coupling, offering an additional valley degree of freedom for information carriers. While optical spin-orbit coupling has traditionally facilitated valley manipulation, on-chip control of nonlinear valley photons remains elusive. Here, the directional coupling of nonlinear chiral valley photons through optical orbit-orbit coupling in monolayer tungsten disulfide at room temperature is demonstrated. The chirality of nonlinear valley photons is governed by the spin angular momentum of the pump light, adhering to nonlinear selection rules. Importantly, the coupling direction is controlled by the orbital angular momentum of the pump light, facilitated by the orbital momentum flux. This approach not only provides a novel method for manipulating the valley degree of freedom but also enhances the flexibility of directing valley photon emission and on-chip routing. These developments hold promising prospects for advanced valley optoelectronic devices.