Here we bypass phase-matching constraints by patterning subwavelength 3R-MoS2 flakes to realize non-local optical resonances. By leveraging the large field confinement and high quality factors offered by our metasurface design, we are able to achieve two orders of magnitude (140×) second-harmonic generation enhancement compared with unpatterned 3R-MoS2 flakes with the same thickness, enabling single-pass second-harmonic conversion efficiencies of 0.01% over only 160-nm-thick metastructures at relevant telecom wavelengths.

This work opens new pathways towards the realization of efficient, on-chip-integrable nonlinear devices with compact footprints based on layered semiconductors, particularly relevant for integrated photonic circuitry and with potential applications in the field of quantum photonics.

Out today in Nature Photonics: Article.