Electrical Control of Interband Resonant Nonlinear Optics in Monolayer MoS2

Monolayer transition-metal dichalcogenides show strong optical nonlinearity with great potential for various emerging applications. Here we demonstrate the gate-tunable interband resonant four-wave mixing and sum-frequency generation in monolayer MoS2. Up to 80% modulation depth in four-wave mixing is achieved when the generated signal is resonant with the A exciton at room temperature, corresponding to an effective third-order optical nonlinearity vertical bar chi(()(3))(eff)vertical bar tuning from (similar to 12.0 to 5.45) x 10(-18) m(2)/V-2. The tunability of the effective second-order optical nonlinearity vertical bar chi(()(2))(eff)vertical bar at 440 nm C-exciton resonance wavelength is also demonstrated from (similar to 11.6 to 7.40) x 10(-9) m/V with sum-frequency generation. Such a large tunability in optical nonlinearities arises from the strong excitonic charging effect in monolayer transition-metal dichalcogenides, which allows for the electrical control of the interband excitonic transitions and thus nonlinear optical responses for future on-chip nonlinear optoelectronics.