Zhu Jingyuan, Zhou Siliang, He Tao, Feng Chao, Wang Zhanshan, Dong Siyu, Cheng Xinbin
Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China.
MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China.
Nanophotonics. 2025 Feb 10;14(8):1221-1229. doi: 10.1515/nanoph-2024-0622. eCollection 2025 Apr.
Littrow diffraction devices are commonly used in the laser field (e.g., laser resonators and spectrometers), where system integration requires larger incidence angles and perfect broadband efficiency. Compared to traditional diffraction devices, which struggle to manipulate light paths under large-angle incidence, metasurfaces has the potential to enhance the broadband efficiency. Despite quasi three-dimensional metasurfaces effects, only perfect anomalous reflection under normal incidence at limited wavelengths was achieved due to energy flow mismatch in the broadband Littrow configuration. Here, we propose a supercell metasurface capable of regulating broadband non-local responses. The metasurface effectively suppresses non-local responses under Littrow mounting, while providing sufficient non-local responses through strong structural coupling effects when the incidence deviates from the Littrow mounting. A large-angle broadband Littrow diffraction metasurface in the mid-infrared spectrum (3.11 µm ∼ 3.52 µm) has been successfully realized, with 99 % efficiency at Littrow angle of 70°. Our results break through the bandwidth limitations of perfect diffraction, providing robust support for the practical applications of metasurfaces in Littrow diffraction devices.
利特罗衍射器件常用于激光领域（如激光谐振器和光谱仪），在这些领域中，系统集成需要更大的入射角和完美的宽带效率。与传统衍射器件相比，传统衍射器件在大角度入射下难以操纵光路，而超表面有潜力提高宽带效率。尽管存在准三维超表面效应，但由于宽带利特罗配置中的能量流不匹配，仅在有限波长的正入射下实现了完美的异常反射。在此，我们提出一种能够调节宽带非局部响应的超胞超表面。该超表面在利特罗安装条件下有效抑制非局部响应，而当入射角偏离利特罗安装时，通过强结构耦合效应提供足够的非局部响应。已成功实现了中红外光谱（3.11 µm ∼ 3.52 µm）中的大角度宽带利特罗衍射超表面，在70°利特罗角下效率达到99 %。我们的结果突破了完美衍射的带宽限制，为超表面在利特罗衍射器件中的实际应用提供了有力支持。
