Difference Frequency Generation from AA‐Stacked WS₂ Coupled with Dual‐Resonant Au Nanocavity

Abstract Difference frequency generation (DFG), underlying on second‐order nonlinear optical effect, is a parametric down‐conversion process that is widely used to generate and amplify broadband signals. It leads to the wide applications in tunable laser systems and infrared sources, as well as quantum light sources. However, it is still challenging to realize the widely tunable, ultra‐compact, and efficient DFG light sources in nanoscales. Here, a boosting DFG from AA‐stacked WS 2 coupled with a tunable dual‐resonant nanocavity, which is composed of Au nanodisk arrays and TiO 2 /Au film, is experimentally demonstrated. In this nanocavity, the Fabry‐Perot mode and localized surface plasmon resonance mode can be independently tuned to match well with the pump (515 nm) and the signal (750–900 nm) wavelength in DFG, respectively. Over two order‐of‐magnitude enhancement of DFG is successfully achieved ranging from 1200 to 1650 nm (e.g., 812 at 1445 nm). This work proposes a dual‐resonance hybrid nanocavity and shines the way to the DFG enhancement in transitional metal dichalcogenides, expanding the prospects in subwavelength coherent light sources and other optoelectronic devices.