Nonlinear van der Waals Metasurfaces with Resonantly Enhanced Light Generation.

Ling, Haonan; Tang, Yuankai; Tian, Xinyu; Shafirin, Pavel; Hossain, Mozakkar; Vabishchevich, Polina P; Harutyunyan, Hayk; Davoyan, Artur R · Nano Lett · 2025

basic_science · Level V

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Abstract

Efficient nonlinear wave mixing is of paramount importance for a wide range of applications. However, weak optical nonlinearities pose significant challenges for accessing nonlinear light-matter interaction in compact systems. Here, we experimentally study second harmonic generation in deeply subwavelength 3R-MoS<sub>2</sub> metasurfaces (<λ/13 thick). Our measurements, supported by theoretical analysis, reveal a complex interplay and coupling between geometric resonances, optical extinction, and exciton-driven strong nonlinear susceptibility dispersion. We further demonstrate >150-fold enhancement in second harmonic signal at 740 nm mediated by the A exciton resonance. Additionally, our theoretical studies predict an enhancement of more than 10<sup>6</sup> in second harmonic generation in <100 nm thick structures exhibiting bound states in the continuum resonance. These findings provide insight into accessing and harnessing the unprecedented 3R-MoS<sub>2</sub> nonlinearities at a subwavelength scale, paving the way to ultracompact nonlinear photonic devices.