中红外超表面的成像和检测原理及应用进展（特邀）

中红外波段包含两个大气窗口及分子指纹区，在红外成像与物质检测方面具有重要应用。传统中红外光学器件在成像方面受材料、加工等限制成本昂贵、加工复杂；在检测方面，受分子吸收截面小的限制，检测灵敏度低，对微量化学物质检测具有较大挑战。超表面是由亚波长尺度的人造单元构成的二维结构阵列，具有体积小、易集成、调控自由度高等特点，能够为制造低成本、轻型化、集成化的中红外光学器件提供一种新的实现方案。表面增强红外吸收能够有效增强分子振动信号，提高检测灵敏度。文章介绍了中红外超表面在电磁波调控方面的机理及其中红外检测应用的原理。着重整理了超表面结构在中红外波段的成像与检测领域的研究进展，包括偏振成像、可调及可重构超表面、其他特殊功能以及用于检测的基于等离子体激元或连续体束缚态原理的使用金、银、铝、石墨烯、硅、锗等材料的超表面结构。

Principles and application progress of mid-infrared metasurfaces in imaging and detection (Invited)

The mid-infrared band contains two atmospheric windows as well as the molecular fingerprint region, and therefore has important applications in infrared imaging and detection. Conventional mid-infrared optics are expensive and need complicated fabrications limited by the material and processing technology in imaging. In terms of the detection, limited by the small molecular absorption cross-section, the sensitivity is extremely low and there is a great challenge for the trace chemical detection. Metasurfaces are two-dimensional arrays composed of artificial building blocks at the subwavelength scale. They have the characteristics of small size, easy integration and high degree of freedom, which may provide a new implementation scheme for manufacturing the low-cost, light-weight and integrated mid-infrared optical devices. Surface-enhanced infrared absorption can effectively enhance molecular vibration signals and improve the detection sensitivity. In this review, the mechanism of mid-infrared metasurfaces in electromagnetic wave regulation and the principals of mid-infrared detection applications are introduced. The research progress in the imaging and detection of mid-infrared metasurfaces is sorted out, including the polarization imaging, tunable and reconfigurable metasurfaces, other special functions and metasurface structures using gold, silver, aluminum, graphene, silicon, germanium and other materials based on plasmon or bound states in the continuum principles for the detection.