Progress on infrared and terahertz electro-magnetic absorptive metasurface
At present, the existence of various electromagnetic (EM) signals in the spectral space causes the electromagnetic anti-interference technology to face continuous severe challenges, due to the widely used equipments for wireless communication. The material or structural design for electromagnetic absorption through energy conversion is the main approach to cope with this appeal.
At the same time, in multiple bands from the micro & millimeter wave to the terahertz & infrared range, the electromagnetic wave absorbing technology, has been a hot topic to improve the survivability of military platforms for many years and widely used in military applications such as detection, accurate strike, stealth, etc. Typical applications of such include various new radar systems, advanced guided weapons, and so on.
However, owing to the heavy & thick structure and low efficiency of traditional absorbing materials, the ultra-light and planar absorbing metasurface with good compatibility with process integration has gradually attracted intensive attentions and become an emerging candidate for current EM absorbing technology.
As the two-dimensional (2D) version of artificial dielectric metamaterial, the metasurface is based on a periodic meta-unit with a thickness much smaller than the operating wavelength. It inherits not only the novel characteristics of perfect absorption, singular transmission & negative refraction, but also the great potential of applications due to the ultra thin and light nature, and ultimately becomes the core choice in applications of planar optical components, the emerging technologies of EM absorption and EM detection.
Dr. Shaolin Zhou’s group, from the School of Microelectronics, South China University of Technology, has been dedicated to the study of micro & nano photonic devices as well as the integration processes. Particularly, in applications of infrared and terahertz detection or sensing, this team tends to optimize the performance of the anti-reflection layer of photo-detector and further improve the merits of quantum efficiency and responsivity, by combining the advantages of ultra thin & light nature as well as good compatibility of process integration. The focus is placed on the optimization of absorbing metasurface structure and its integration with the architecture of infrared detector.
In this paper, the progresses in methodologies of design of metasurface devices in current infrared and terahertz bands are reviewed. In particular, for ultra-broadband absorption, the conventional method is to resort to a periodic meta-cell with multiple resonant units with different sizes or to the cascades of units vertically aligned in the longitudinal direction.
In recent years, the dispersion theory based on the dielectric impedance matching provides a new idea for design of broadband metasurface. Especially, the emergence and breakthroughs of catenary electromagnetics enrich the design of structural type of periodic cells as well as the ideas for broadband absorbing metasurface devices. In addition, for the dynamic tuning including switching, modulation, etc., the absorption tunable metasurface based on the integration of semiconductor, liquid crystal or phase change material has become a new trend. Namely, active tuning can be achieved by integrating the active dielectric, metasurface and the absorbing structure. However, this article is only one part of iceberg of the wide applications of meta-surface. Future progresses aim to the direction of higher structural diversity, enormously enlarged scope of applications and even simplified structural design. New phenomena and applications such as one-dimensional metamaterials and the coherent absorptive super-surfaces have been emerging.
Fig. 1 Schematic of the single-layered GMBA (gradient-metasurface-based absorber)
Fig. 2 Schematic structure of the broadband THz absorber and the simulated results. (a) Top view of the arrays; (b) Three-dimensional schematic diagram
About the Group
The microelectronics device team where Dr. Zhou’s group belongs, from the School of Microelectronics, South China University of Technology, has long been conducting researches in optoelectronic devices, MEMS, wide bandgap semiconductor devices and micro-nano optoelectronic integration processes. This is a combined and innovative group of 10 faculty members and more than 50 graduate students, with research background and interests including nanophotonics, microelectronics, vacuum electronics, MEMS, emerging micro-nano sensors & TFT display, etc. Meanwhile, members of this team establish extensive cooperation with different groups from institutions inside China and those overseas, including IOE, CAS(Institute of Optics and Electronics, Chinese Academy of Sciences), IME, CAS(Institute of Microelectronics, Chinese Academy of Sciences), HKUST, CityU, etc.
Deng Honglang, Zhou Shaolin, Cen Guanting. Progress on infrared and terahertz electro-magnetic absorptive metasurface[J]. Opto-Electronic Engineering, 2019, 46(8): 180666.