Tailor the Functionalities of Metasurfaces Based on a Complete Phase Diagram

Qu, Che; Ma, Shaojie; Hao, Jiaming; Qiu, Meng; Li, Xin; Xiao, Shiyi; Miao, Ziqi; Dai, Ning; He, Qiong; Sun, Shulin; Zhang, Yuanbo; Zhou, Lei

doi:10.1103/physrevlett.115.235503

Cited by 259 publications

(179 citation statements)

References 43 publications

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“…[32,33] To this end, we begin with the response of LMMs, expressed by [34] d d [32,33] To this end, we begin with the response of LMMs, expressed by [34] d d…”

mentioning

confidence: 99%

Intelligent Metamaterials Based on Nonlinearity for Magnetic Resonance Imaging

Zhao

Duan

et al. 2019

Advanced Materials

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the optical regime. [10,11] The capacity of metamaterials for electric field confinement has enabled the realization of a range of physical phenomena in metamaterials, such as electron emission [12] and phase transition in quantum materials. [13] In turn, the electric field enhancement resulting from the near-field confinement leads to nonlinear responses in metamaterials that have been harnessed to enable high harmonic generation, [14] saturable absorption, [15] phase-conjugation, [16] and optical electrifying effects, [17] among other features.In addition to confining the electric field, metamaterials are capable of interacting with and efficiently tailoring the magnetic field. The ability of metamaterials to manipulate the magnetic field has enabled their applications to inductive wireless power transfer, [18] enhancement of the magneto-optic effect, [19] high-quality sensing, [20,21] plasmonic perfect absorption, [22] and magnetic field confinement, [23,24] among others. Another important application of the capacity for magnetic field manipulation is magnetic resonance imaging (MRI), which is the focus herein. For example, negative permeability metamaterials have been employed as waveguides [25] and lenses [26] to image deep tissues using 1.5 Tesla (T) MRI systems and a cylindrical meta-atom has been developed to mitigate the field inhomogeneity in 7 T MRI systems based on the Kerker effect. [27] Recently, judiciously designed metamaterials, consisting of wire [28] or helical resonator arrays, [29] have been utilized to enhance the signal-to-noise ratio (SNR) of the MRI by amplifying the radio-frequency (RF) magnetic field strength due to their capacity for magnetic field enhancement. However, an ongoing limitation of currently available linear metamaterials (LMMs) for enhancing SNR in MRI systems reported to date is their linear nature, resulting in an amplification of the magnetic field during both RF transmission and reception phases in MRI, as shown in Figure 1a. The adoption of an LMM in MRI therefore requires modification of the RF excitation pulses during the transmission phase, [28,29] resulting in undue complications, suboptimal performance, potential safety concerns, and a substantial impediment to clinical adoption.Nonlinear metamaterials (NLMMs) yield an opportunity to construct intelligent and self-adaptive metamaterials in order to selectively enhance the magnetic field during MRI. By leveraging the voltage-dependent capacitance of a varactor diode induced by a reverse-biased p-n junction, [30,31] we developed an NLMM operating at RF frequencies. As opposed

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“…[32,33] To this end, we begin with the response of LMMs, expressed by [34] d d [32,33] To this end, we begin with the response of LMMs, expressed by [34] d d…”

mentioning

confidence: 99%

Intelligent Metamaterials Based on Nonlinearity for Magnetic Resonance Imaging

Zhao

Duan

et al. 2019

Advanced Materials

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“…The measured and simulated reflection spectra of sample B are shown in Figure 4a. [34,35] In this region, the reflection phase can cover nearly 360° range as the frequency passes through the resonance. The relaxation time extracted from the simulation is 35 fs, which is realistic for a CVD-grown monolayer graphene.…”

Section: Resultsmentioning

confidence: 99%

Electrically Tunable Perfect Terahertz Absorber Based on a Graphene Salisbury Screen Hybrid Metasurface

Chen

Tian

et al. 2019

Advanced Optical Materials

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has made realistic applications of the THz wave very limited. Among the functional THz devices, perfect absorbers are highly desirable in manipulating the THz wave in a number of important fields.In recent years, extensive efforts have been devoted to perfect THz absorption based on artificial structures, such as metasurfaces. [2][3][4] Most of these structures, however, were passive devices and incapable of real-time adjustment. Graphene, a 2D sheet of hexagonally arranged carbon atoms, has attracted much attention in the past decade due to its extraordinary electronic and optoelectronic properties. [5] As a 2D semiconductor, its electron mobility and Fermi level can be extensively controlled by external stimulants, such as gate voltage [6] and thus its surface conductivity. Therefore, graphene has been a promising candidate for active optoelectronics applications and absorber devices based on demonstrations in the microwave [7,8] and infrared [9][10][11][12][13][14][15][16][17][18] regimes. At THz frequencies, graphene-based absorbers were also experimentally realized. By integrating monolayer graphene into a classical Salisbury screen structure, perfect THz absorption was achieved. [19][20][21][22] However, the graphene Fermi level needed to realize perfect absorption was very high and the thickness of the absorbers were required to be around λ/4, which is too bulky for optical integration. A broadband, nearly perfect THz absorber based on patterned graphene was also reported [23] with a relatively small electrical tunability. Besides, theoretical works on graphene-based THz absorbers were proposed. [24][25][26][27][28][29] However, most studies mainly focused on simulations and calculations. Therefore, experimental realization of electrically tunable perfect THz absorption based on lightly-doped and low-quality graphene with deep subwavelength dimensions remains as an unsolved challenge.In this article, we experimentally demonstrate an electrically tunable perfect THz absorber by integrating a metallic grating into a graphene-based Salisbury screen structure. The measured results show that perfect absorption can be achieved with a more lightly doped chemical vapor deposition (CVD) graphene compared to that of the classical Salisbury screen absorber and the modulation depth of absorbance can reach up to 25%. Numerical simulations were performed using commercial full-wave numerical software showing a good agreement with the measurements. Furthermore, we proposed a simple Graphene, as a popular 2D semiconductor, with a carrier concentration that can be extensively tailored by external stimulants, such as electric bias and photoexcitation, is a promising candidate for active optoelectronics. An electrically tunable perfect terahertz absorber is presented by integrating a metallic grating into classical graphene Salisbury screen. The measurement shows that perfect absorption can be achieved for even lightly-doped graphene and a modulation depth up to 25% is realized. Numerical simulation and analytical model based...

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“…Such an MIM structure was widely used to design high-efficiency reflective metasurfaces at frequencies ranging from microwave to visible [22,23,44,72,79,91], simply because its metallic ground plane can help reflect all incoming waves back (thus, Equation (1) can be easily satisfied) while the phase of reflected wave can undergo a continuous −180 • to 180 • variation as frequency passes through a resonance inside the "meta-atom". Such a resonance is usually called "magnetic resonance" [14] or "gap-plasmon resonance" [22,72], and its properties are carefully analyzed in [91,92]. Therefore, tuning the geometrical parameters of such a meta-atom can efficiently modify its two reflection phases (ϕ xx and ϕ yy ) (see Figure 3b), which then offers enough freedoms to design multifunctional meta-devices.…”

Section: Multifunctional Metasurfaces Exhibiting Similar Functionalitiesmentioning

confidence: 99%

Multifunctional Metasurfaces Based on the “Merging” Concept and Anisotropic Single-Structure Meta-Atoms

Tang

Cai

et al. 2018

Applied Sciences

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Metasurfaces offer great opportunities to control electromagnetic (EM) waves, attracting intensive attention in science and engineering communities. Recently, many efforts were devoted to multifunctional metasurfaces integrating different functionalities into single flat devices. In this article, we present a concise review on the development of multifunctional metasurfaces, focusing on the design strategies proposed and functional devices realized. We first briefly review the early efforts on designing such systems, which simply combine multiple meta-structures with distinct functionalities to form multifunctional devices. To overcome the low-efficiency and functionality cross-talking issues, a new strategy was proposed, in which the meta-atoms are carefully designed single structures exhibiting polarization-controlled transmission/reflection amplitude/phase responses. Based on this new scheme, various types of multifunctional devices were realized in different frequency domains, which exhibit diversified functionalities (e.g., focusing, deflection, surface wave conversion, multi-beam emissions, etc.), for both pure-reflection and pure-transmission geometries or even in the full EM space. We conclude this review by presenting our perspectives on this fast-developing new sub-field, hoping to stimulate new research outputs that are useful in future applications.

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Tailor the Functionalities of Metasurfaces Based on a Complete Phase Diagram

Cited by 259 publications

References 43 publications

Intelligent Metamaterials Based on Nonlinearity for Magnetic Resonance Imaging

Intelligent Metamaterials Based on Nonlinearity for Magnetic Resonance Imaging

Electrically Tunable Perfect Terahertz Absorber Based on a Graphene Salisbury Screen Hybrid Metasurface

Multifunctional Metasurfaces Based on the “Merging” Concept and Anisotropic Single-Structure Meta-Atoms

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