主动式太赫兹超材料器件综述 下载： 1193次
Significance Recently, terahertz technology has made rapid progress in the fields of label-free analysis, cellular level imaging, chemical and biological sensing, security screening, and wireless communications. Furthermore, major advances have been made in terahertz sources, detectors, and modulators. Developing efficient modulators with natural materials is challenging due to the relatively weak interactions between terahertz waves and natural materials. Although functional modulators operating in the visible and infrared bands are mature for commercial applications, efficient, functional, and high-speed modulators are severely lacking in the technologically important terahertz band. Therefore, researchers are trying to obtain solutions that can improve light-matter interactions for terahertz applications. Metamaterials have extraordinary electromagnetic properties that show great potential to enhance local field strength significantly and improve light-matter interactions in practical terahertz modulators. The integration of metamaterials and certain active materials or techniques leads to the revolution of conventional modulators, which are named “metadevices” in this review. Metamaterials enable abundant functionalities of these devices, and integrated materials offer active responses to external stimuli. These types of hybrid metadevices lead to lower energy consumption, larger modulation depth, faster modulation speed, and more abundant functionalities due to the substantial local electric field enhancement of metamaterials. In this review, the current progress of active metadevices for terahertz applications is summarized with different approaches. In addition, the working mechanism, typical device configurations, major performance, and drawbacks are discussed.
Progress This review summarizes several typical configurations of active terahertz metadevices integrated with liquid crystals (Section 2.1), micro-electromechanical systems (MEMS, Section 2.2), semiconductors (Section 2.3), graphene (Section 2.4), phase change materials (Section 2.5), superconductors (Section 2.5), nonlinear materials (Section 2.5), and chemical reactions (Section 2.5). Electrically triggered liquid crystals integrated with metamaterials exhibit excellent terahertz modulation performance, operating in both transmission and reflection modes. Due to the great flexibility of electrical actuation, this type of metadevice can realize programmable control and operate in a complex configuration for wave deflection (
The major problem of limited modulation speed can be addressed by excluding electrical stimuli and applying an optical pump. All-optical metadevices have no theoretical limitations of modulation speed determined by the relaxation dynamics of the active materials. By integrating semiconductors (e.g., Si, Ge, GaAs, and WSe2) with metamaterials, all-optical hybrid metadevices demonstrate excellent performance for ultrafast terahertz modulation (
Conclusions and Prospects Different techniques have been discussed for hybrid metadevices with stimuli of electricity (e.g., liquid crystals, semiconductors, graphene, MEMS, and diodes/transistors), optics (e.g., semiconductors, graphene, phase change materials, and superconductors), heat (e.g., phase change materials and superconductors), forces (e.g., MEMS), and chemical reaction (e.g., Mg). Although there are certain limitations for different combinations, metadevices have made major progress toward realizing efficient terahertz modulators. With the maturity of the semiconductor industry, active metadevices with semiconductors are very attractive for programmable, fast, and efficient terahertz applications. Metadevices integrated with graphene are also attractive with easy fabrication and high efficiency that can be actuated by electrical or optical stimuli. All-optical metadevices are the solution to access faster modulation speed, and an appropriate combination of nonlinear materials and metamaterials would push modulation speeds to the GHz or even THz regime. All the approaches have pros and cons and should be utilized where most applicable.
丛龙庆. 主动式太赫兹超材料器件综述[J]. 中国激光, 2021, 48(19): 1914003. Longqing Cong. Active Terahertz Metadevices[J]. Chinese Journal of Lasers, 2021, 48(19): 1914003.