Abdelraouf Omar A M, Wang Ziyu, Liu Hailong, Dong Zhaogang, Wang Qian, Ye Ming, Wang Xiao Renshaw, Wang Qi Jie, Liu Hong
School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore.
ACS Nano. 2022 Sep 27;16(9):13339-13369. doi: 10.1021/acsnano.2c04628. Epub 2022 Aug 17.
Metasurfaces, a two-dimensional (2D) form of metamaterials constituted by planar meta-atoms, exhibit exotic abilities to tailor electromagnetic (EM) waves freely. Over the past decade, tremendous efforts have been made to develop various active materials and incorporate them into functional devices for practical applications, pushing the research of tunable metasurfaces to the forefront of nanophotonics. Those active materials include phase change materials (PCMs), semiconductors, transparent conducting oxides (TCOs), ferroelectrics, liquid crystals (LCs), atomically thin material, , and enable intriguing performances such as fast switching speed, large modulation depth, ultracompactness, and significant contrast of optical properties under external stimuli. Integration of such materials offers substantial tunability to the conventional passive nanophotonic platforms. Tunable metasurfaces with multifunctionalities triggered by various external stimuli bring in rich degrees of freedom in terms of material choices and device designs to dynamically manipulate and control EM waves on demand. This field has recently flourished with the burgeoning development of physics and design methodologies, particularly those assisted by the emerging machine learning (ML) algorithms. This review outlines recent advances in tunable metasurfaces in terms of the active materials and tuning mechanisms, design methodologies, and practical applications. We conclude this review paper by providing future perspectives in this vibrant and fast-growing research field.
超表面是由平面超原子构成的二维超材料形式，展现出自由调控电磁波的奇特能力。在过去十年中，人们付出了巨大努力来开发各种活性材料，并将其纳入功能性器件以用于实际应用，从而将可调谐超表面的研究推向了纳米光子学的前沿。这些活性材料包括相变材料（PCM）、半导体、透明导电氧化物（TCO）、铁电体、液晶（LC）、原子级薄材料等，并能在外部刺激下实现诸如快速开关速度、大调制度深度、超紧凑性以及显著的光学性质对比度等引人入胜的性能。这类材料的集成赋予了传统无源纳米光子平台极大的可调谐性。由各种外部刺激触发的具有多功能性的可调谐超表面，在材料选择和器件设计方面带来了丰富的自由度，从而能够按需动态地操纵和控制电磁波。随着物理学和设计方法，特别是那些借助新兴机器学习（ML）算法的方法的蓬勃发展，该领域最近蓬勃兴起。本文综述了可调谐超表面在活性材料与调谐机制、设计方法以及实际应用方面的最新进展。我们通过展望这个充满活力且快速发展的研究领域的未来，来结束这篇综述文章。
