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Seojoo Lee Soojeong Baek Teun-Teun Kim Hyukjoon Cho Sangha Lee Ji-Hun Kang Bumki Min 《Advanced materials (Deerfield Beach, Fla.)》2020,32(35):2000250
Metamaterials, artificially constructed structures that mimic lattices in natural materials, have made numerous contributions to the development of unconventional optical devices. With an increasing demand for more diverse functionalities, terahertz (THz) metamaterials are also expanding their domain, from the realm of mere passive devices to the broader area where functionalized active THz devices are particularly required. A brief review on THz metamaterials is given with a focus on research conducted in the authors' group. The first part is centered on enhanced THz optical responses from tightly coupled meta-atom structures, such as high refractive index, enhanced optical activity, anomalous wavelength scaling, large phase retardation, and nondispersive polarization rotation. Next, electrically gated graphene metamaterials are reviewed with an emphasis on the functionalization of enhanced THz optical responses. Finally, the linear frequency conversion of THz waves in a rapidly time-variant THz metamaterial is briefly discussed in the more general context of spatiotemporal control of light. 相似文献
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Longqing Cong Vassili Savinov Yogesh Kumar Srivastava Song Han Ranjan Singh 《Advanced materials (Deerfield Beach, Fla.)》2018,30(40)
The interaction between microscopic particles is always a fascinating and intriguing area of science. Direct interrogation of such interactions is often difficult. Structured electromagnetic systems offer a rich toolkit for mimicking and reproducing the key dynamics that govern the microscopic interactions, and thus provides an avenue to explore and interpret the microscopic phenomena. In particular, metamaterials offer the freedom to artificially tailor light–matter coupling and to control the interaction between unit cells in the metamaterial array. Here, a terahertz metamaterial that mimics spin‐related interactions of microscopic particles in a 2D lattice via complex electromagnetic multipoles scattered within the metamaterial array is demonstrated. Fano resonances featured by distinct mode properties due to strong nearest‐neighbor interactions are discussed, which draw parallels with the 2D Ising model. Interestingly, a phase transition from single Fano resonance to hyperfine splitting of the Fano spectrum is observed by manipulating the 2D interactions without applying external magnetic or electric fields, which provides a potential multispectral platform for applications in super‐resolution imaging, biosensing, and selective thermal emission. The dynamic approach to reproduce static interaction between microscopic particles will enable more profound significance in exploring the unknown physical world by the macroscopic analogs. 相似文献
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Chen Zaichun Mohsen Rahmani Gong Yandong Chong Tow Chong Hong Minghui 《Advanced materials (Deerfield Beach, Fla.)》2012,24(23):OP143-OP147
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Terahertz Metamaterials: Electrically Controllable Molecularization of Terahertz Meta‐Atoms (Adv. Mater. 31/2018) 
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下载免费PDF全文 Hyunseung Jung Jaemok Koo Eunah Heo Boeun Cho Chihun In Wonwoo Lee Hyunwoo Jo Jeong Ho Cho Hyunyong Choi Moon Sung Kang Hojin Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(31)
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Hyunseung Jung Jaemok Koo Eunah Heo Boeun Cho Chihun In Wonwoo Lee Hyunwoo Jo Jeong Ho Cho Hyunyong Choi Moon Sung Kang Hojin Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(31)
Active control of metamaterial properties is critical for advanced terahertz (THz) applications. However, the tunability of THz properties, such as the resonance frequency and phase of the wave, remains challenging. Here, a new device design is provided for extensively tuning the resonance properties of THz metamaterials. Unlike previous approaches, the design is intended to control the electrical interconnections between the metallic unit structures of metamaterials. This strategy is referred to as the molecularization of the meta‐atoms and is accomplished by placing graphene bridges between the metallic unit structures whose conductivity is modulated by an electrolyte gating. Because of the scalable nature of the molecularization, the resonance frequency of the terahertz metamaterials can be tuned as a function of the number of meta‐atoms constituting a unit metamolecule. At the same time, the voltage‐controlled molecularization allows delicate control over the phase shift of the transmitted THz, without changing the high transmission of the materials significantly. 相似文献
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Flynn Castles Julian A. J. Fells Dmitry Isakov Stephen M. Morris Andrew A. R. Watt Patrick S. Grant 《Advanced materials (Deerfield Beach, Fla.)》2020,32(9):1904863
Although well-established textbook arguments suggest that static electric susceptibility χ(0) must be positive in “all bodies,” it has been pointed out that materials that are not in thermodynamic equilibrium are not necessarily subject to this restriction. Media with inverted populations of atomic and molecular energy levels have been predicted theoretically to exhibit a χ(0) < 0 state, however the systems envisioned require reduced temperature, reduced pressure, and an external pump laser to maintain the population inversion. Further, the existence of χ(0) < 0 has never been confirmed experimentally. Here, a completely different approach is taken to the question of χ(0) < 0 and a design concept to achieve “true” χ(0) < 0 is proposed based on active metamaterials with internal power sources. Two active metamaterial structures are fabricated that, despite still having their power sources implemented externally for reasons of practical convenience, provide evidence in support of the general concept. Effective values are readily achieved at room temperature and pressure and are tunable throughout the range of stability −1 < χ(0) < 0, resulting in experimentally-determined magnitudes that are over one thousand times greater than those predicted previously. Since χ(0) < 0 is the missing electric analog of diamagnetism, this work opens the door to new technological capabilities such as stable electrostatic levitation. 相似文献
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Ann‐Katrin U. Michel Andreas Heßler Sebastian Meyer Julian Pries Yuan Yu Thomas Kalix Martin Lewin Julian Hanss Angela De Rose Tobias W. W. Maß Matthias Wuttig Dmitry N. Chigrin Thomas Taubner 《Advanced materials (Deerfield Beach, Fla.)》2019,31(29)
Nanometer‐thick active metasurfaces (MSs) based on phase‐change materials (PCMs) enable compact photonic components, offering adjustable functionalities for the manipulation of light, such as polarization filtering, lensing, and beam steering. Commonly, they feature multiple operation states by switching the whole PCM fully between two states of drastically different optical properties. Intermediate states of the PCM are also exploited to obtain gradual resonance shifts, which are usually uniform over the whole MS and described by effective medium response. For programmable MSs, however, the ability to selectively address and switch the PCM in individual meta‐atoms is required. Here, simultaneous control of size, position, and crystallization depth of the switched phase‐change material (PCM) volume within each meta‐atom in a proof‐of‐principle MS consisting of a PCM‐covered Al–nanorod antenna array is demonstrated. By modifying optical properties locally, amplitude and light phase can be programmed at the meta‐atom scale. As this goes beyond previous effective medium concepts, it will enable small adaptive corrections to external aberrations and fabrication errors or multiple complex functionalities programmable on the same MS. 相似文献
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Jianguo Zhao Utku Gulan Takafumi Horie Naoto Ohmura Jun Han Chao Yang Jie Kong Steven Wang Ben Bin Xu 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(18)
Biological liquid crystals, a rich set of soft materials with rod‐like structures widely existing in nature, possess typical lyotropic liquid crystalline phase properties both in vitro (e.g., cellulose, peptides, and protein assemblies) and in vivo (e.g., cellular lipid membrane, packed DNA in bacteria, and aligned fibroblasts). Given the ability to undergo phase transition in response to various stimuli, numerous practices are exercised to spatially arrange biological liquid crystals. Here, a fundamental understanding of interactions between rod‐shaped biological building blocks and their orientational ordering across multiple length scales is addressed. Discussions are made with regard to the dependence of physical properties of nonmotile objects on the first‐order phase transition and the coexistence of multi‐phases in passive liquid crystalline systems. This work also focuses on how the applied physical stimuli drives the reorganization of constituent passive particles for a new steady‐state alignment. A number of recent progresses in the dynamics behaviors of active liquid crystals are presented, and particular attention is given to those self‐propelled animate elements, like the formation of motile topological defects, active turbulence, correlation of orientational ordering, and cellular functions. Finally, future implications and potential applications of the biological liquid crystalline materials are discussed. 相似文献
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Manukumara Manjappa Ankur Solanki Abhishek Kumar Tze Chien Sum Ranjan Singh 《Advanced materials (Deerfield Beach, Fla.)》2019,31(32)
Solution‐processed lead iodide (PbI2) governs the charge transport characteristics in the hybrid metal halide perovskites. Besides being a precursor in enhancing the performance of perovskite solar cells, PbI2 alone offers remarkable optical and ultrasensitive photoresponsive properties that remain largely unexplored. Here, the photophysics and the ultrafast carrier dynamics of the solution processed PbI2 thin film is probed experimentally. A PbI2 integrated metamaterial photonic device with switchable picosecond time response at extremely low photoexcitation fluences is demonstrated. Further, findings show strongly confined terahertz field induced tailoring of sensitivity and switching time of the metamaterial resonances for different thicknesses of PbI2 thin film. The approach has two far reaching consequences: the first lead‐iodide‐based ultrafast photonic device and resonantly confined electromagnetic field tailored transient nonequilibrium dynamics of PbI2 which could also be applied to a broad range of semiconductors for designing on‐chip, ultrafast, all‐optical switchable photonic devices. 相似文献
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Metamaterials: A New Ba0.6Sr0.4TiO3–Silicon Hybrid Metamaterial Device in Terahertz Regime (Small 19/2016) 下载免费PDF全文
下载免费PDF全文 Liang Wu Ting Du Ningning Xu Chunfeng Ding Hui Li Quan Sheng Ming Liu Jianquan Yao Zhiyong Wang Xiaojie Lou Weili Zhang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(19):2609-2609
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Liang Wu Ting Du Ningning Xu Chunfeng Ding Hui Li Quan Sheng Ming Liu Jianquan Yao Zhiyong Wang Xiaojie Lou Weili Zhang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(19):2610-2615
Metamaterials, offering unprecedented functionalities to manipulate electromagnetic waves, have become a research hotspot in recent years. Through the incorporation of active media, the exotic electromagnetic behavior of metamaterials can be dramatically empowered by dynamic control. Many ferroelectric materials such as BaSrTiO3 (abbreviated as BST), exhibiting strong response to external electric field, hold great promise in both microwave and terahertz tunable devices. A new active Ba0.6Sr0.4TiO3–silicon hybrid metamaterial device, namely, a SRR (square split‐ring resonator)–BaSrTiO3 thin film‐silicon three‐layer structure is fabricated and intensively studied. The active Ba0.6Sr0.4TiO3 thin film hybrid metamaterial, with nanoscale thickness, delivers a transmission contrast up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate. This work has significantly increased the low modulation rate of ferroelectric based devices in terahertz range, a major problem in this field remaining unresolved for many years. The proposed BST metamaterial is promising in developing high‐performance real world photonic devices for terahertz technology. 相似文献
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