Nonlinear Dispersion Relation and Out-of-Plane Second Harmonic Generation in MoSSe and WSSe Janus Monolayers

摘要

Janus transition metal dichalcogenides are an emerging class of atomicallythin materials with engineered broken mirror symmetry that gives rise tolong-lived dipolar excitons, Rashba splitting, and topologically protectedsolitons. They hold great promise as a versatile nonlinear optical platform dueto their broadband harmonic generation tunability, ease of integration onphotonic structures, and nonlinearities beyond the basal crystal plane. Here,second and third harmonic generation in MoSSe and WSSe Janus monolayersis studied. Polarization-resolved spectroscopy is used to map the fullsecond-order susceptibility tensor of MoSSe, including its out-of-planecomponents. In addition, the effective third-order susceptibility and thesecond-order nonlinear dispersion close to exciton resonances for bothMoSSe and WSSe are measured at room and cryogenic temperatures. Thiswork sets a bedrock for understanding the nonlinear optical properties ofJanus transition metal dichalcogenides and probing their use in thenext-generation on-chip multifaceted photonic devices.