Metamaterials and Metasurfaces

Abstract

Since the proposal of metamaterials by Rodger Walser in 1999, the recent twenty years have witnessed the rapid development of various metamaterials and 2D metasurfaces in a wide range of frequency bands covering the microwave, terahertz, infrared, visible and ultraviolet. Metamaterials exhibit unusual electromagnetic properties not occurring in natural materials, such as negative refraction and hyperbolic dispersion, enabling numerous completely novel applications, including perfect imaging, invisibility cloaking, quantum effects enhancement and even the mimic of celestial mechanics. Although 3D metamaterials have experienced thriving advancement in the microwave and infrared region, the realization of low-loss optical metamaterials has been scarce. As a result of the easiness of large scale fabrication, 2D metasurfaces have attracted considerable attention in the latest 10 years. Through the generalization of Snell's law to ultra-broadband perfect absorption of light, metasurfaces have shown their great potentials in the manipulation of all the properties of electromagnetic waves. Currently, most of the commercial meta-devices are operating in the microwave regime, in the form of some kinds of metasurfaces.1 It is also believed that the first generation of practical optical meta-devices will utilize metasurface implementations.2, 3 It is a great dream of physical scientists and engineers to convert theoretical breakthroughs to revolutionary technologies and products. However, there are still some gaps between the theories and mass production for both the metamaterials and metasurfaces in the optical bands. For example, the operating bandwidth and efficiency of traditional resonant meta-devices are limited as a consequence of the strong resonance and damping of energy. In addition, the metalenses are suffering from chromatic dispersion, which limits their applications in broadband white light imaging. Besides these theoretical challenges, the large-scale fabrication of subwavelength structures with low cost and high precision is urgently required. Although it is relatively easy for the microwave community, the difficulty increases dramatically when the minimal structure dimensions scale down to tens of nanometers. In the past few years, many efforts have been devoted to solving the above problems, and many milestone results have been obtained. To promote the researches in novel metamaterials and metasurfaces, and transform prototypes to practical functional devices, Advanced Optical Materials decided to launch a special issue on this topic. The leading scientists in this field have been invited to write authoritative reviews on specified topics or share their original discoveries that break the challenges faced by the community. We hope that this could serve as a good celebration of the 20th anniversary of metamaterials and give a flavor for the current and exciting future research directions. This special issue covers a broad range of the cutting-edge research in the fields, such as dielectric metasurfaces, flat lens, light emission, polarization conversion, perfect absorption, plasmonic lithography, spin-orbit interaction, magneto-optical effects, second-harmonic generation, dispersion engineering, and dynamic manipulation. Although there are some differences in the microwave and optical engineering, there is a strong trend to combine all these technologies together, as a result of the merging of civil and military requirements. It should be noted that the field of metamaterials and metasurfaces is not limited to optics and electromagnetics. During the last few years, the spirit of metamaterials has been extended to other disciplines such as acoustics, mechanics and thermal engineering. Owing to the scope of Advanced Optical Materials, we do not consider them in this special issue. This collection comprises 12 high-quality reviews and 8 research articles written by leading experts in this field. As a result of the limited pages and preparing time, some late submissions must be treated as regular articles and not included in this special issue. We apologize for not being able to provide a more comprehensive coverage. Finally, it is a great honor for me to edit this special issue. All the colleagues who contributed their articles are appreciated. Of course, I would give special thanks to Dr. Jipei Yuan for making this special issue possible. Xiangang Luo Chengdu, 2019 Xiangang Luo is currently the director of State Key Laboratory of Optical Technologies on Nano-fabrication and Micro-engineering (SKLOTNM), and the president of the Institute of Optics and Electronics (IOE), Chinese Academy of Sciences (CAS). He received Ph.D. from Chinese Academy of Sciences in 2001. He was a Research Scientist in The Institute of Physical and Chemical Research (RIKEN) of Japan. His research interests include micro/nano-optics, plasmonics, metamaterials, catenary optics and subwavelength electromagnetics. He has published more than 300 scientific papers and 100 patents in optics and related fields. He was elected as Fellow of the Optical Society of America (OSA), International Society for Optical Engineering (SPIE), the International Academy of Photonics and Laser Engineering (IAPLE), and Chinese Optical Society.