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arXiv · 2607.08430

Doubly resonant enhancement of second-harmonic generation with in-plane phase matching in plasmonic metasurfaces on an AlInP slab waveguide

Timo Stolt·Huayu Bai·Seyed Ahmad Shahahmadi·Jani Oksanen·Andriy Shevchenko·Radoslaw Kolkowski
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Abstract

Nonlinear metasurfaces have attracted significant interest by offering the possibility to circumvent conventional phase-matching requirements of bulk nonlinear crystals, opening the way to efficient frequency conversion over ultrashort propagation distances. Here, we experimentally demonstrate metasurfaces in which second-harmonic generation is strongly enhanced by in-plane phase matching of high-Q guided-mode resonances. To achieve this enhancement, we use hybrid metasurfaces composed of periodic arrays of gold nanodiscs on a slab waveguide made of aluminum indium phosphide (AlInP) - a low-loss epitaxial III-V semiconductor material. The metasurfaces are found to exhibit guided-mode resonances with Q factors exceeding 400 and 900 at the visible and near-infrared wavelengths, respectively, demonstrating the unique capabilities of hybrid metal-dielectric structures to support high-Q resonances despite the presence of lossy plasmonic components. Moreover, our frequency and momentum-resolved measurements demonstrate a two-orders-of-magnitude enhancement of second-harmonic generation at doubly resonant conditions. We reproduce the experimental results using numerical simulations, showing that the in-plane phase matching and spatial mode overlap are the main factors governing the enhancement. Our findings demonstrate a promising strategy to realize efficient metasurface-based frequency converters, enabling their potential applications in compact photonic systems.

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Timo Stolt, Huayu Bai, Seyed Ahmad Shahahmadi, Jani Oksanen, Andriy Shevchenko, Radoslaw Kolkowski. 2026-07-09. Doubly resonant enhancement of second-harmonic generation with in-plane phase matching in plasmonic metasurfaces on an AlInP slab waveguide. https://arxiv.org/abs/2607.08430

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