Plasmon-Enhanced Second-Harmonic Generation in Atomically Thin Crystalline Silver Nanostructures

Addressing this challenge is crucial for the development of nonlinear nanophotonics. Here, we show that atomically thin, epitaxially grown crystalline silver films circumvent these restrictions through the interplay of vertical electronic quantum confinement and lateral plasmonic enhancement.

We fabricate atomically thin films that exhibit an enhanced nonlinear response associated with electronic quantum wells, and subsequently pattern them into periodic nanoribbon and nanotriangle arrays sustaining infrared localized surface plasmon resonances. Strong near-field confinement in these structures further boosts second-harmonic generation compared to unpatterned films. Precise control over nanostructure geometry enables spectral tuning of the plasmonic resonance, and consequently, the enhanced harmonic frequency.