Nonlinear plasmonic metasurfaces are compatible with complementary metal oxide semiconductor technology and highly promising for on-chip optical switching and modulations and nanoscale frequency conversions. However, the low nonlinear-optical response of metasurface devices limits their practical applications. To circumvent this constraint, we propose the design of a nanocavity plasmonic metasurface, in which the strong light localization in the nanocavity can be used to boost the efficiency of second-harmonic generation. Compared with the single-layer counterpart, experimental results show that the intensity of the second-harmonic waves in the nanocavity metasurface is enhanced by ∼790 times. The proposed nanocavity plasmonic metasurfaces in this work may open new routes for developing highly efficient nonlinear metacrystals for on-chip nonlinear sources, nonlinear image encryption, information processing, and so on.

非线性等离子体超表面与互补金属氧化物半导体技术兼容，非常有希望用于片上光开关和调制以及纳米级频率转换。然而，超表面器件的低非线性光学响应限制了它们的实际应用。为了规避这一限制，我们提出了纳米腔等离子体超表面的设计，其中纳米腔中的强光定位可用于提高二次谐波产生的效率。与单层对应物相比，实验结果表明，纳米腔超表面中的二次谐波强度提高了约 790 倍。