scholarly journals Graphene-Modulated Terahertz Metasurfaces for Selective and Active Control of Dual-Band Electromagnetic Induced Reflection (EIR) Windows

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2420
Author(s):  
Xunjun He ◽  
Chenguang Sun ◽  
Yue Wang ◽  
Guangjun Lu ◽  
Jiuxing Jiang ◽  
...  
Keyword(s):  
Active Control ◽  
Slow Light ◽  
Near Field ◽  
Dual Band ◽  
Destructive Interference ◽  
Dark Mode ◽  
Field Coupling ◽  
Control Scheme ◽  
Electrostatic Doping ◽  
Induced Transparency

Currently, metasurfaces (MSs) integrating with different active materials have been widely explored to actively manipulate the resonance intensity of multi-band electromagnetic induced transparency (EIT) windows. Unfortunately, these hybrid MSs can only realize the global control of multi-EIT windows rather than selective control. Here, a graphene-functionalized complementary terahertz MS, composed of a dipole slot and two graphene-integrated quadrupole slots with different sizes, is proposed to execute selective and active control of dual-band electromagnetic induced reflection (EIR) windows. In this structure, dual-band EIR windows arise from the destructive interference caused by the near field coupling between the bright dipole slot and dark quadrupole slot. By embedding graphene ribbons beneath two quadrupole slots, the resonance intensity of two windows can be selectively and actively modulated by adjusting Fermi energy of the corresponding graphene ribbons via electrostatic doping. The theoretical model and field distributions demonstrate that the active tuning behavior can be ascribed to the change in the damper factor of the corresponding dark mode. In addition, the active control of the group delay is further investigated to develop compact slow light devices. Therefore, the selective and active control scheme introduced here can offer new opportunities and platforms for designing multifunctional terahertz devices.

scholarly journals Optical tunable multifunctional slow light device based on double monolayer graphene grating-like metamaterial

2021 ◽  
Author(s):  
Hui Xu ◽  
Xiaojing Wang ◽  
Zhiquan Chen ◽  
Xuelei Li ◽  
Longhui He ◽  
...  
Keyword(s):  
Slow Light ◽  
Incident Light ◽  
Monolayer Graphene ◽  
Group Index ◽  
Dark Mode ◽  
Coupled Mode ◽  
Frequency Selection ◽  
Electrostatic Doping ◽  
Tunable Device ◽  
Induced Transparency

Abstract A very simple optical tunable device, which can realize multiple functions of frequency selection, reflection and slow light, is presented at the investigation. The proposed device is constructed by a periodic grating-like structure. There are two dielectrics (graphene and silicon) in a period of the equivalent grating. The incident light will strongly resonate with the graphene of electrostatic doping, forming an evanescent wave propagating along the surface of graphene, and this phenomenon is the surface plasmon. Under constructive interference of the polaritons, a unique plasmonic induced transparency phenomenon will be achieved. The induced transparency produced by this device can be well theoretically fitted by the bright and dark mode of optical equivalent cavity which can be called coupled mode theory (CMT). This theory can well analyze the influence of various modes and various losses between the function of this device. The device can use gate voltages for electrostatic doping in order to change the graphene carrier concentration and tune the optical performance of the device. Moreover, the length of the device in y-direction is will be much larger than the length of single cycle, providing some basis for realizing the fast tunable function and laying a foundation for the integration. Through a simulation and calculation, we can find that the group index and group delay of this device are as high as 515 and 0.257 picoseconds (ps) respectively, so it can provide a good construction idea for the slow light device. The proposed grating-like metamaterial structure can provide certain simulation and theoretical help for the optical tunable reflectors, absorbers, and slow light devices.

scholarly journals Dynamically Tunable Resonant Strength in Electromagnetically Induced Transparency (EIT) Analogue by Hybrid Metal-Graphene Metamaterials

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 171 ◽  
Author(s):  
Chaode Lao ◽  
Yaoyao Liang ◽  
Xianjun Wang ◽  
Haihua Fan ◽  
Faqiang Wang ◽  
...  
Keyword(s):  
Optical Networks ◽  
Electromagnetically Induced Transparency ◽  
Near Field ◽  
Monolayer Graphene ◽  
Dark Mode ◽  
Resonance Strength ◽  
Field Coupling ◽  
Terahertz Communications ◽  
Unit Cells ◽  
Induced Transparency

In this paper, a novel method to realize a dynamically tunable analogue of EIT for the resonance strength rather than the resonance frequency is proposed in the terahertz spectrum. The introduced method is composed of a metal EIT-like structure, in which a distinct EIT phenomenon resulting from the near field coupling between bright and dark mode resonators can be obtained, as well as an integrated monolayer graphene ribbon under the dark mode resonator that can continuously adjust the resonance strength of transparency peak by changing the Fermi level of the graphene. Comparing structures that need to be modulated individually for each unit cell of the metamaterials, the proposed modulation mechanism was convenient for achieving synchronous operations for all unit cells. This work demonstrates a new platform of modulating the EIT analogue and paves the way to design terahertz functional devices which meet the needs of optical networks and terahertz communications.

scholarly journals Experimental Demonstration of Electromagnetically Induced Transparency in a Conductively Coupled Flexible Metamaterial with Cheap Aluminum Foil

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Jie Hu ◽  
Tingting Lang ◽  
Weihang Xu ◽  
Jianjun Liu ◽  
Zhi Hong
Keyword(s):  
Electromagnetically Induced Transparency ◽  
Near Field ◽  
Surface Current ◽  
Aluminum Foil ◽  
Ring Resonators ◽  
Dark Mode ◽  
Field Coupling ◽  
New Ideas ◽  
Induced Transparency ◽  
Bright Mode

AbstractWe propose a conductively coupled terahertz metallic metamaterial exhibiting analog of electromagnetically induced transparency (EIT), in which the bright and dark mode antennae interact via surface currents rather than near-field coupling. Aluminum foil, which is very cheap and often used in food package, is used to fabricate our metamaterials. Thus, our metamaterials are also flexible metamaterials. In our design, aluminum bar resonators and aluminum split ring resonators (SRRs) are connected (rather than separated) in the form of a fork-shaped structure. We conduct a numerical simulation and an experiment to analyze the mechanism of the proposed metamaterial. The surface current due to LSP resonance (bright mode) flows along different paths, and a potential difference is generated at the split gaps of the SRRs. Thus, an LC resonance (dark mode) is induced, and the bright mode is suppressed, resulting in EIT. The EIT-like phenomenon exhibited by the metamaterial is induced by surface conducting currents, which may provide new ideas for the design of EIT metamaterials. Moreover, the process of fabricating microstructures on flexible substrates can provide a reference for producing flexible microstructures in the future.

scholarly journals Analog of multiple electromagnetically induced transparency using double-layered metasurfaces

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Siyuan Liu ◽  
Zhixia Xu ◽  
Xiaoxing Yin ◽  
Hongxin Zhao
Keyword(s):  
Electromagnetically Induced Transparency ◽  
Near Field ◽  
Localized Surface Plasmons ◽  
Dark Mode ◽  
Field Coupling ◽  
Double Peaks ◽  
Resonant Modes ◽  
Physical Essence ◽  
Induced Transparency ◽  
Mode A

Abstract We reported an analog of electromagnetically induced transparency (A-EIT) featured by double transparent peaks in the spectrum. The A-EIT is realized by double-layered metasurface which consists of spoof localized surface plasmons (S-LSP) and cut-wire (CW)-square rings (SR) hybrid. Electric and magnetic S-LSP are excited as bright and dark modes respectively then couple with resonant modes of CW and SR simultaneously to achieve multiple A-EIT. Two bright modes of the electric S-LSP and SR are excited by external electric field directly that produce a bright-bright mode A-EIT. Moreover, the magnetic S-LSP, which cannot be excited by external field directly, is excited through near field coupling from CW, inducing another bright-dark mode A-EIT. Theoretical analysis with corresponding experiment in microwave band are introduced for better insights into physical essence of the double-peaks A-EIT.

scholarly journals Electromagnetically Induced Transparency-Like Effect by Dark-Dark Mode Coupling

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1350
Author(s):  
Qiao Wang ◽  
Kaili Kuang ◽  
Huixuan Gao ◽  
Shuwen Chu ◽  
Li Yu ◽  
...  
Keyword(s):  
Mode Coupling ◽  
Slow Light ◽  
Electromagnetically Induced Transparency ◽  
Research Area ◽  
Destructive Interference ◽  
Dark Mode ◽  
Metal Grating ◽  
Layer 4 ◽  
Induced Transparency ◽  
Waveguide Resonance

Electromagnetically induced transparency-like (EIT-like) effect is a promising research area for applications of slow light, sensing and metamaterials. The EIT-like effect is generally formed by the destructive interference of bright-dark mode coupling and bright-bright mode coupling. There are seldom reports about EIT-like effect realized by the coupling of two dark modes. In this paper, we numerically and theoretically demonstrated that the EIT-like effect is achieved through dark-dark mode coupling of two waveguide resonances in a compound nanosystem with metal grating and multilayer structure. If we introduce |1〉, | 2 〉 and | 3 〉 to represent the surface plasmon polaritons (SPPs) resonance, waveguide resonance in layer 2, and waveguide resonance in layer 4, the destructive interference occurs between two pathways of | 0 〉 → | 1 〉 → | 2 〉 and | 0 〉 → | 1 〉 → | 2 〉 → | 3 〉 → | 2 〉 , where | 0 〉 is the ground state without excitation. Our work will stimulate more studies on EIT-like effect with dark-dark mode coupling in other systems.

scholarly journals Independently tunable electromagnetically induced transparency effect and dispersion in a multi-band terahertz metamaterial

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Rakesh Sarkar ◽  
Dipa Ghindani ◽  
Koijam Monika Devi ◽  
S. S. Prabhu ◽  
Amir Ahmad ◽  
...  
Keyword(s):  
Slow Light ◽  
Electromagnetically Induced Transparency ◽  
Near Field ◽  
The Other ◽  
Transmission Spectra ◽  
Field Coupling ◽  
Induced Transparency ◽  
Coupled Harmonic Oscillator ◽  
Bright Mode ◽  
Multi Band

AbstractIn this article, we experimentally and numerically investigate a planar terahertz metamaterial (MM) geometry capable of exhibiting independently tunable multi-band electromagnetically induced transparency effect (EIT). The MM structure exhibits multi-band EIT effect due to the strong near field coupling between the bright mode of the cut-wire (CW) and dark modes of pair of asymmetric double C resonators (DCRs). The configuration allows us to independently tune the transparency windows which is challenging task in multiband EIT effect. The independent modulation is achieved by displacing one DCR with respect to the CW, while keeping the other asymmetric DCR fixed. We further examine steep dispersive behavior of the transmission spectra within the transparency windows and analyze slow light properties. A coupled harmonic oscillator based theoretical model is employed to elucidate as well as understand the experimental and numerical observations. The study can be highly significant in the development of multi-band slow light devices, buffers and modulators.

scholarly journals Hybrid Metal Graphene-Based Tunable Plasmon-Induced Transparency in Terahertz Metasurface

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 385 ◽  
Author(s):  
Xianjun Wang ◽  
Hongyun Meng ◽  
Shuying Deng ◽  
Chaode Lao ◽  
Zhongchao Wei ◽  
...  
Keyword(s):  
Near Field ◽  
Contrast Ratio ◽  
Polarization Vector ◽  
Ring Resonators ◽  
Periodic Lattice ◽  
Destructive Interference ◽  
Dark Mode ◽  
Practical Applications ◽  
Induced Transparency ◽  
Plasmon Induced Transparency

In this paper, we look at the work of a classical plasmon-induced transparency (PIT) based on metasurface, including a periodic lattice with a cut wire (CW) and a pair of symmetry split ring resonators (SSR). Destructive interference of the ‘bright-dark’ mode originated from the CW and a pair of SSRs and resulted in a pronounced transparency peak at 1.148 THz, with 85% spectral contrast ratio. In the simulation, the effects of the relative distance between the CW and the SSR pair resonator, as well as the vertical distance of the split gap, on the coupling strength of the PIT effect, have been investigated. Furthermore, we introduce a continuous graphene strip monolayer into the metamaterial and by manipulating the Fermi level of the graphene we see a complete modulation of the amplitude and line shape of the PIT transparency peak. The near-field couplings in the relative mode resonators are quantitatively understood by coupled harmonic oscillator model, which indicates that the modulation of the PIT effect result from the variation of the damping rate in the dark mode. The transmitted electric field distributions with polarization vector clearly confirmed this conclusion. Finally, a group delay t g of 5.4 ps within the transparency window is achieved. We believe that this design has practical applications in terahertz (THz) functional devices and slow light devices.

scholarly journals Dual-Tunable Polarization Insensitive Electromagnetically Induced Transparency in Metamaterials

2021 ◽  
Author(s):  
Renxia Ning ◽  
Zhiqiang Xiao ◽  
Zhenhai Chen ◽  
Wei Huang
Keyword(s):  
Vanadium Dioxide ◽  
Mode Coupling ◽  
Slow Light ◽  
Chemical Potential ◽  
Electromagnetically Induced Transparency ◽  
Dark Mode ◽  
Potential Applications ◽  
Polarization Insensitive ◽  
Terahertz Devices ◽  
Induced Transparency

AbstractA multilayer structure of a square ring of graphene with nesting vanadium dioxide (VO2) was investigated in this study. This structure exhibits electromagnetically induced transparency (EIT), which stems from a bright mode coupling with a dark mode. The permittivity values of graphene and VO2 can be modulated via chemical potential and temperature, respectively. The EIT effect can be tuned based on the chemical potential of graphene and temperature of VO2, resulting in a dual-tunable EIT effect. Simulation results confirmed that this dual-tunable EIT phenomenon is insensitive to polarization. These results may have potential applications in terahertz devices, such as slow light devices, switching devices, and sensors.

scholarly journals Dual-Mode On-to-Off Modulation of Plasmon-Induced Transparency and Coupling Effect in Patterned Graphene-Based Terahertz Metasurface

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Zhimin Liu ◽  
Enduo Gao ◽  
Zhenbin Zhang ◽  
Hongjian Li ◽  
Hui Xu ◽  
...  
Keyword(s):  
Slow Light ◽  
Coupling Effect ◽  
Structural Parameters ◽  
Fdtd Simulation ◽  
Destructive Interference ◽  
Dual Mode ◽  
Coupled Mode ◽  
Induced Transparency ◽  
Difference Time ◽  
Plasmon Induced Transparency

AbstractThe plasmon-induced transparency (PIT), which is destructive interference between the superradiation mode and the subradiation mode, is studied in patterned graphene-based terahertz metasurface composed of graphene ribbons and graphene strips. As the results of finite-difference time-domain (FDTD) simulation and coupled-mode theory (CMT) fitting, the PIT can be dynamically modulated by the dual-mode. The left (right) transmission dip is mainly tailored by the gate voltage applied to graphene ribbons (stripes), respectively, meaning a dual-mode on-to-off modulator is realized. Surprisingly, an absorbance of 50% and slow-light property of 0.7 ps are also achieved, demonstrating the proposed PIT metasurface has important applications in absorption and slow-light. In addition, coupling effects between the graphene ribbons and the graphene strips in PIT metasurface with different structural parameters also are studied in detail. Thus, the proposed structure provides a new basis for the dual-mode on-to-off multi-function modulators.

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