Graphene-based Metamaterials Research Articles

Terahertz and gigahertz magnetoratchets in graphene-based two-dimensional metamaterials

Terahertz and gigahertz magnetoratchets in graphene-based two-dimensional metamaterials

Sensing Based on Plasmon-Induced Transparency in H-Shaped Graphene-Based Metamaterials.

Graphene can support surface plasmon polaritons (SPPs) in the terahertz band, and graphene SPP sensors are widely used in the field of terahertz micro- and nano-optical devices. In this paper, we propose an H-shaped graphene metasurface and investigate the plasmon-induced transparency (PIT) phenomenon in the proposed structure using the finite-difference time-domain (FDTD) method. Our results show that the Fermi energy levels, as well as certain shape parameters, can effectively modulate the PIT phenomenon in the proposed structure. Interestingly, changing some of these shape parameters can excite two dips into three. In terms of sensing performance, the maximum values of sensitivity and figure of merit (FOM) are 1.4028 THz/RIU and 17.97, respectively. These results offer valuable guidance for the use of terahertz optical graphene SPP sensors.

Manipulation of Electromagnetic Waves Via Graphene-Based Coding Metamaterials for Terahertz Applications

Manipulation of Electromagnetic Waves Via Graphene-Based Coding Metamaterials for Terahertz Applications

Multi-frequency modulator of dual plasma-induced transparency in graphene-based metasurface

Graphene-based metamaterials can generate plasma-induced transparency (PIT), offering a new approach for achieving modulators with optimal modulation performance. This study presents a multi-frequency modulator based on novel monolayer graphene structure. We utilize Coupled Mode Theory (CMT) for thorough theoretical investigations, yielding theoretical values that agree well with simulation results. Moreover, we discuss the implications of the Fermi level on PIT and the influence of graphene carrier mobility on switch modulation. The research findings illustrate the successful realization of a high-performance multi-frequency modulator by indirectly controlling the phase of the dual PIT transmission spectra through an adjustable bias voltage. Notably, at a frequency of 3.93 THz, the increasing of carrier mobility enhances the modulation depth of the modulator from 89.22 % to 97.88 % and reduces the insertion loss from 0.34 dB to 0.12 dB. Hence, our research has substantial implications for designing excellent tunable terahertz optical modulator devices and contributing to the advancement of optical communication systems and optoelectronic applications.

Graphene-based polarization-insensitive metamaterials with perfect absorption for terahertz biosensing applications: Analytical approach

Graphene-based polarization-insensitive metamaterials with perfect absorption for terahertz biosensing applications: Analytical approach

3D Printed Graphene-Based Metamaterials: Guesting Multi-Functionality in One Gain.

Advanced functional materials with fascinating properties and extended structural design have greatly broadened their applications. Metamaterials, exhibiting unprecedented physical properties (mechanical, electromagnetic, acoustic, etc.), are considered frontiers of physics, material science, and engineering. With the emerging 3D printing technology, the manufacturing of metamaterials becomes much more convenient. Graphene, due to its superior properties such as large surface area, superior electrical/thermal conductivity, and outstanding mechanical properties, shows promising applications to add multi-functionality into existing metamaterials for various applications. In this review, the aim is to outline the latest developments and applications of 3D printed graphene-based metamaterials. The structure design of different types of metamaterials and the fabrication strategies for 3D printed graphene-based materials are first reviewed. Then the representative explorations of 3D printed graphene-based metamaterials and multi-functionality that can be introduced with such a combination are further discussed. Subsequently, challenges and opportunities are provided, seeking to point out future directions of 3D printed graphene-based metamaterials.

Polarization-Insensitive, Broadband, and Tunable Terahertz Absorber Using Slotted-Square Graphene Meta-Rings

Graphene-based metamaterials are gaining popularity for developing various reconfigurable and electrically tunable optical devices – especially in terahertz (THz) and infrared (IR) bands. Therefore, in this paper, we aim to investigate the broadband metamaterial-based absorber that efficiently absorbs the THz radiation ranging from 2.2 to 4.6 THz. The proposed absorber comprises a simple meta-square ring of graphene, which possesses different slots in its structure to induce multiple plasmonic resonances. It is observed that the proposed absorber manifests above 95% absorption for the normally incident THz waves, and it also maintains its absorption value over 80% for different obliquely incident operating conditions. Furthermore, the proposed absorber shows polarization-insensitive features. In addition, the absorption characteristics regulate from 95% to 15% by adjusting the chemical potential of graphene from 1 eV to 0.1 eV. Some of the salient features of the proposed absorber is largest reported bandwidth for single layer absorber with smallest footprint without sacrificing polarization insensitivity or amplitude tunability. From the application point of view, it could provide the pathway for implementing switching, cloaking, smart absorbers, and detection phenomena in the THz range.

Patterned Graphene-Based Metamaterials for Terahertz Wave Absorption

Graphene-based metamaterials have been widely applied in optoelectronic devices, optical modulators, and chemical sensors due to the outstanding tunability and optical response in the terahertz (THz) region. Here, tunable THz metamaterial absorbers based on patterned graphene are designed, fabricated, and modulated. The proposed metamaterial absorbers are constructed by the top layer of patterned graphene arrays and the aluminum (Al) film separated by polyimide (PI). The different THz absorption spectra can be acquired by changing the patterns of graphene. In order to verify the simulation results, a series of tests were conducted by THz time-domain spectrometer (THz-TDS) systems. The proposed absorbers are able to be insensitive to the angle of the incident wave. Besides, chemical doping is applied to turn the Fermi level of graphene and the absorption performance is promoted with the increase of the Fermi level. The experimental results have been demonstrated to have associated resonant peaks with the simulation results. The aim of this paper is to exhibit a systematic study on graphene-based THz metamaterial absorbers, including the simulation and experiments. By comparing the simulation and experimental results, it is useful to clarify the relevant theories and manufacturing processes. The work will provide a further step in the development of high-performance terahertz devices, including tunable absorbers, sensors, and electro-optic switches.

Perfect terahertz absorber with dynamically tunable peak and bandwidth using graphene-based metamaterials

A graphene-based dynamic tunable terahertz (THz) perfect absorber is proposed in this paper. The absorber consists of periodic gold nanoribbons on a graphene-coated silica layer supported by a flat gold substrate, and the graphene is sandwiched between two hexagonal boron nitride (h-BN) layers. We demonstrate that the proposed structure can lead to perfect THz absorption because of strong photon localization surrounding the graphene layer of the structure. The THz absorption may be tuned continuously from 0 to 100% by controlling the chemical potential through a gate voltage. Moreover, the peak position and bandwidth of absorption spectra can be tuned by adjusting the width of the gold nanoribbons and duty ratio. The absorber can maintain high-efficiency light absorption of more than 90% at a wide range of light incidence angles of 0 to 85 deg. Using the existing technology, our design scheme is easy to realize, which will be helpful to promote the development and application of optoelectronic devices.

Graphene-Based Absorption-Transmission Multi-Functional Tunable THz Metamaterials.

The paper reports an absorption–transmission multifunctional tunable metamaterial based on graphene. Its pattern graphene layer can achieve broadband absorption, while the frequency selective layer can achieve the transmission of specific band. Furthermore, the absorption and transmission can be controlled by applying voltage to regulate the chemical potential of graphene. The analysis results show that the absorption of the metamaterial is adjustable from 22% to 99% in the 0.72 THz~1.26 THz band and the transmittance is adjustable from 80% to 95% in 2.35 THz. The metamaterial uses UV glue as the dielectric layer and PET (polyethylene terephthalate) as the flexible substrate, which has good flexibility. Moreover, the metamaterial is insensitive to incident angle and polarization angle, which is beneficial to achieve excellent conformal properties.

Longitudinal and transverse frictional drag in graphene/ LaAlO3/SrTiO3 heterostructures

Heterostructures composed of different layered materials provide novel opportunities to investigate the electronic correlations between them. Here we investigate frictional drag between graphene and ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ (LAO/STO) heterostructures. The LAO/STO layer underneath the graphene is rendered conductive using conductive atomic force microscope (c-AFM) lithography, creating a two-layer system in which the LAO serves as an ultrathin ($<$2 nm) insulating barrier. By sourcing current in both the STO layer and graphene layer, Coulomb drag is studied in a wide range, from an STO superconducting region to a graphene quantum Hall region. Pronounced fluctuations in the frictional drag resistance are observed when the STO is superconducting. A large enhancement of drag resistance is observed when the STO becomes superconducting. Pronounced stripelike oscillations in the frictional drag appear in the quantum Hall region, both along the main channel and the transverse (Hall) configuration. The behavior is consistent with numerical simulations that model energy and momentum transfer from the STO layer to the graphene layer. These help to create a platform for graphene-based metamaterials using the programmable LAO/STO interface.

Tunable terahertz filter/antenna-sensor using graphene-based metamaterials

In this paper, a novel tunable graphene-based bandstop filter/antenna-sensor is presented. This structure is an integrated module that can be used to combine filtering and high-gain radiation performance. The initial design of the unit cell consists of four U-shaped stubs loaded, resembling the arms of a ring and a sensing layer in the substrate. The reflection and transmission spectra are obtained for various graphene’s chemical potentials and refractive index of sensing layer (Ns) of structure in the range of 1.3–1.6 THz. The proposed structure exhibits the attributes of both dual-band filter and single-band antenna-sensor. The conductivity of graphene and its structural parameters are studied to optimize the component performance. In filtering mode, the first bandstop is from 1.23 to 1.6 THz equal to 26% of fractional bandwidth (FBW) at 1.415 THz. The second stopband is centered at 3.12 THz with FBW of 14% for Ns = 1.6 and 0.6 eV chemical potential. In the antenna mode, a single band of the antenna-sensor is centered at 1.95 THz for the same Ns and same chemical potential. It is shown that a sensitivity of 0.145 THz/RIU is achieved at Ns = 1.5 and chemical potential of 0.6 eV. Additionally, the performance of the proposed filter/antenna-sensor module is investigated for different wave polarizations and oblique angles.

Using tunable inter-resonator coupling to reshape the mid-infrared absorption spectrum of graphene-based metamaterials

We explore the use of tunable inter-resonator coupling to reshape the spectral absorptivity of a graphene-based metamaterial. The metamaterial comprises of a periodic array of coupled metal-insulator-metal resonators, with two resonators per unit cell. One resonator supports a bright mode, and the other a dark mode. We use coupled-mode theory to show that, by tuning the resonant wavelength of the bright mode through the dark mode, the spectrum can be reconfigured from a single-peak shape to a split-peak shape. We then propose specific, realistic device geometries to allow realization of this concept.

Spatial Dissipative Solitons in Graphene-Based Active Random Metamaterials

We investigate dissipative nonlinear dynamics in graphene-based active metamaterials composed of randomly dispersed graphene nanoflakes embedded within an externally pumped gain medium. We observe that graphene saturable nonlinearity produces a subcritical bifurcation of nonlinear modes, enabling self-organization of the emitted radiation into several dissipative soliton structures with distinct topological charges. We systematically investigate the existence domains of such nonlinear waves and their spatial dynamics, finding that soliton vortices are unstable, thus enabling self-organization into single dissipative structures with vanishing topological charge, independently of the shape of the graphene nanoflakes. Our results shed light on self-organization of coherent radiation structures in disordered systems and are relevant for future cavity-free lasers and amplifier designs.

Graphene-based plasmonic metamaterial for terahertz laser transistors

Abstract This paper reviews recent advances in the research and development of graphene-based plasmonic metamaterials for terahertz (THz) laser transistors. The authors’ theoretical discovery on THz laser transistors in 2007 was realized as a distributed-feedback dual-gate graphene-channel field-effect transistor (DFB-DG-GFET) in 2018, demonstrating ∼0.1 µW single-mode emission at 5.2 THz and ∼80 µW amplified spontaneous 1–7.6 THz emission at 100 K. To realize room-temperature, dry-cell-battery operating intense THz lasing with fast direct modulation, various approaches based on graphene plasmonic metamaterials are investigated and introduced as real device implementations, including (i) replacement of the laser photonic cavity with plasmonic cavity enormously improving the THz photon field confinement with larger gain overlapping, (ii) introduction of THz amplification of stimulated emission via current-driven graphene Dirac plasmons (GDPs), and (iii) controlling the parity and time-reversal symmetry of GDPs enabling ultrafast direct gain-switch modulation. Possible real device structures and design constraints are discussed and addressed toward coherent light sources applicable to future 6G- and 7G-class THz wireless communication systems.

Frequency-dependent ultrasensitive terahertz dynamic modulation at the Dirac point on graphene-based metal and all-dielectric metamaterials

The development of terahertz (THz) technology is creating a demand for devices that can modulate THz beams. Here, we report the design and characterization of three THz modulators. One uses graphene and a metal-microstructure-integrated metamaterial, another uses a bare graphene film, and the third uses graphene-based all-dielectric metamaterials. Ultrasensitive dynamic THz modulation is achieved by shifting the quasi-Fermi level between the Dirac point, the conduction band, and the valence of graphene via continuous-wave optical illumination or bias voltages. When the Fermi level is close to the Dirac point, the modulation is ultrasensitive to the external stimuli. The modulation depth can reach the maximum value of 346% in the current public publication, breaking through the bottleneck of modulation inefficiency, and is expected to realize practical applications for the first time. For the range 0.2–2 THz, the modulation depth initially increases, then decreases. These results will enable potential designs for ultrasensitive THz devices.

Adsorption of graphene-based metamaterials and its application in detection of heavy metal ions

We propose a graphene-based terahertz metamaterial approach to the detection of heavy metal ions (HMIs). Theoretical calculations and numerical simulations show that the amplitude and phase of electromagnetically induced transparency/reflection resonance of the devices depending on the concentration and type of the HMI in the solution. By changing the bias voltage, the devices can be easily adjusted to their linear working regime for enhanced response speed and performance. By adding specific functional groups to the graphene, the devices may even recognize one specific HMI out of many due to selective adsorption. The proposed concept and discussed method can be helpful to design highly sensitive, fast, and reusable HMI detectors.

Actively tunable and switchable electromagnetically induced transparency in hybrid metal-graphene metamaterials

Active control of the electromagnetically induced transparency (EIT) is highly desirable for advanced terahertz (THz) device applications. Currently, the EIT peak positions in the graphene-based metamaterials have been actively controlled by tailoring Fermi energy of graphene via electric doping. However, there is still a considerable challenge to realize active strength modulation of the EIT peak without frequency shifting. Here, a hybrid metal-graphene structure, consisting of the metal-based EIT metamaterial and patterning graphenes, is proposed at the THz frequencies. Through changing Fermi energy of graphene, the EIT peak strength can exhibit both active modulation and on-to-off switch without frequency shifting. Moreover, theoretical model and field distributions discover that the active response can be attributed to the increasing damping rate of the dark mode caused by the controllable conductivity of graphene. In addition, the controllable group delay is also achieved for the slow light applications. Therefore, this work provides the possibility for designing compact slow light devices in the information processing and telecommunication applications.

A tunable broadband graphene-based metamaterial absorber in the far-infrared region

This paper reports a new design of a broadband absorber composed of graphene, dielectric, and gold layers. The designed absorber has four absorbent modes close to each other, which results in the formation of broadband absorption. The relative bandwidth, a key parameter to assess the bandwidth improvement, shows a significant increase in the proposed design compared to similar structures published in recent years. The numerical results also reveal this metamaterial absorber can be used for applications in the far-infrared frequency range due to choosing optimized dimensions and the graphene Fermi level. Unlike other graphene-based metamaterials, which require complicated structures to be able to attain broadband absorption, the physical structure of the proposed design has a relatively simple fabrication process. For further investigations, the effect of split geometry on the absorption spectrum is studied. Also, the use of graphene in this metamaterial absorber provides dynamic adjustability through electrostatic doping in order to tune the amount of absorption. This characteristic has been studied by changing the graphene Fermi level. This feature can be widely used in electro-absorption switches and modulators.

Withdrawal Notice: New Matter Properties and Applications based on Hybrid Graphene-based Metamaterials

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