Reconfigurable second-harmonic generation via plasmonic nanoslits counteracting strain-induced suppression in monolayer MoS₂.

Abstract

Second-harmonic generation (SHG) in monolayer transition-metal dichalcogenides is highly sensitive to mechanical strain, often leading to signal suppression under deformation. Here, we demonstrate reconfigurable SHG in monolayer MoS₂ integrated with plasmonic nanoslits, where localized plasmonic fields counteract strain-induced suppression. The plasmonic nanoslits induce strong spatially localized field enhancement, yielding an SHG enhancement of up to 8000, estimated by normalizing the signal to the illumination area, relative to MoS₂ on unpatterned Au films. Applying 1.2% compressive strain increases the SHG intensity by approximately threefold relative to the unstrained state, demonstrating effective strain-enabled modulation. Upon mechanical bending, the SHG response is reversibly modulated and remains stable after an initial preconditioning regime, retaining more than 95% of its initial intensity over repeated bending cycles. This strain-adaptive platform demonstrates robust cycling stability and provides a previously unexplored strategy for dynamically reconfigurable nonlinear metasurfaces, enabling applications in wearable sensors, tunable modulators, and compact frequency converters.