2025-04-01 ハーバード大学
ハーバード大学ジョン・A・ポールソン工学・応用科学部（SEAS）の研究者たちは、チタン酸化物ナノ構造を二層に積み重ねた新しいビレイヤーメタサーフェスを開発しました。この構造により、光の波長、位相、偏光などの特性を高精度に制御することが可能となり、従来の単層メタサーフェスでは難しかった多機能性と高性能を実現しています。このビレイヤーメタサーフェスは、イメージングシステム、拡張現実（AR）、分光学、通信など、多岐にわたる分野での応用が期待されています。研究成果は『Nature Communications』誌に掲載されました。
＜関連情報＞
- https://seas.harvard.edu/news/2025/04/doubling-down-metasurfaces
- https://www.nature.com/articles/s41467-025-58205-7
可視光における自立二層メタサーフェス Free-standing bilayer metasurfaces in the visible
Ahmed H. Dorrah,Joon-Suh Park,Alfonso Palmieri & Federico Capasso
Nature Communications Published:01 April 2025
DOI:https://doi.org/10.1038/s41467-025-58205-7
Abstract
Multi-layered meta-optics have enabled complex wavefront shaping beyond their single layer counterpart owing to the additional design variables afforded by each plane. For instance, lossless complex amplitude modulation, generalized polarization transformations, and wide field of view are key attributes that fundamentally require multi-plane wavefront matching. Nevertheless, existing embodiments of bilayer metasurfaces have relied on configurations which suffer from Fresnel reflections, low mode confinement, or undesired resonances which compromise the intended response. Here, we introduce bilayer metasurfaces made of free-standing meta-atoms working in the visible spectrum. We demonstrate their use in wavefront shaping of linearly polarized light using pure geometric phase with diffraction efficiency of 80% — expanding previous literature on Pancharatnam-Berry phase metasurfaces which rely on circularly or elliptically polarized illumination. The fabrication relies on a two-step lithography and selective development processes which yield free standing, bilayer stacked metasurfaces, of 1200 nm total thickness. The metasurfaces comprise TiO2 nanofins with vertical sidewalls. Our work advances the nanofabrication of compound meta-optics and inspires new directions in wavefront shaping, metasurface integration, and polarization control.
