Domain-Selective Enhancement of Second Harmonic Generation in Monolayer MoS2 via Ferroelectricity-Controlled Photodoping

Abstract

Abstract Hybrid heterostructures combining two-dimensional semiconductors with ferroelectric materials offer a versatile route to actively control light–matter interactions at the nanoscale. Here, we report all-optical, light-induced domain-selective control of second-harmonic generation (SHG) in monolayer molybdenum disulfide (MoS2) integrated with periodically poled lithium niobate (LiNbO3). Spatially resolved SHG imaging reveals a pronounced modulation of the nonlinear optical response of monolayer MoS2 governed by the ferroelectric domain pattern of the underlying substrate. A strong SHG contrast is observed between domains of opposite polarization, with a marked dependence on both the excitation wavelength and the incident optical power. The comparison between ferroelectric domains that either enable or do not exhibit light-driven photodoping in the MoS2 monolayer provides a direct assessment of the role of carrier density in the nonlinear optical response. We find that ferroelectric-polarization-controlled photodoping at the MoS2/LiNbO3 interface enhances the effective second-order susceptibility, χ(2), producing an increase in SHG intensity of up to ∼70% under resonant excitation conditions. Ab initio calculations corroborate that charge doping modifies the electronic band structure of MoS2 and strongly affects χ(2) in the resonant regime, providing microscopic support for the experimentally observed modulation. The results highlight the combination of light intensity and ferroelectricity as a powerful knob for band-structure modulation in 2D materials and reconfigurable nonlinear optical responses, opening pathways toward programmable frequency conversion, smart light modulators, and advanced nonlinear photonic functionalities in integrated hybrid platforms.