Graphene Nanoribbon Resonators Research Articles

Tunable graphene quadrupole dark mode based ultranarrow Fano resonance in asymmetric hybrid metamaterial

We numerically demonstrate the ultranarrow high-order Fano resonance generated by the plasmonic coupling between graphene quadrupole dark mode and metallic bright magnetic dipole mode due to structural symmetry breaking effect in asymmetric hybrid metamaterials, consisting of periodic arrays of graphene nanoribbon and gold split-ring resonators. The graphene quadrupole Fano curve presents an ultranarrow lineshape with quality (Q) factor of 40. The proposed metamaterial shows the obvious dependence of the structural parameters and Fermi energy. Our designed asymmetric hybrid metamaterials shows a high sensitivity of 4.2μm/RIU and figure of merit (FOM) of 30, which could pave way for in label-free biomedical sensing.

Effect of built-in tension due to variation in temperature on natural frequency of graphene nano ribbon resonator

Miniaturization of the devices at nano scale has evolved new dimension in the sector of science and engineering as far as atomic level sensing is concerned. Such miniaturization has become possible due to state of the art manufacturing techniques. Various materials have been implemented for manufacturing of nano sized resonators. Out of these materials, graphene has drawn attention of researchers across all sectors of science and engineering due to its outstanding mechanical and electrical properties. Structural point of view, it is a thin, monolayer, two dimensional material, still it can be deformed up to 25% higher than other materials which makes it preferred material for design and fabrication of nano resonator. Despite exhibiting excellent properties, graphene, in its pristine form is non-piezoelectric due to symmetry of carbon atoms. To induce piezoelectricity into pristine graphene, symmetry of graphene structure must be broken by applying mechanism in the form of point or line defect, adatoms or strain due to mechanical/thermal load. The application of thermal loading will affect the natural frequency of the nano resonator. The paper deals with the effect of built-in tension due to variation in temperature on natural frequency of graphene nano ribbon (GNR) resonator. The size of GNR is as follows: Length = 1000 nm, Width = 100 nm and Thickness = 0.335 nm. Doubly clamped configurations is considered for GNR resonator. The range of temperature is considered from 300 K to 200 K. The obtained results depict that as the temperature varies, the built-in tension varies and so is the fundamental mode of frequency of GNR.

Graphene-based wavelength demultiplexing structure.

A wavelength demultiplexing (WDM) structure based on graphene nanoribbon resonators is proposed and simulated using the finite-difference time-domain (FDTD) method. Based on a simple structure, the demultiplexing wavelength and transmission characteristics of the WDM can be tuned by adjusting the length of the resonator, the nanoribbon width, or the chemical potential of graphene within a relative broadband frequency range. Moreover, the mechanism of the proposed WDM structure is analyzed in detail using the theory of Fabry-Perot (F-P) resonance and temporal coupled-mode theory. The proposed structure has promising potential in the field of ultracompact WDM systems in highly integrated optical circuits.

Frequency-tunable logic gates in graphene nano-waveguides

In this study, simple basic plasmonic logic gates of XOR, OR, and NOT based on graphene nano-ribbon resonators coupled to properly designed arrangements of nano-waveguides, as input and output logic ports, are demonstrated. The operation of the structures as frequency selective components is based on the propagation of edge modes in nano-waveguides and coupling to nano-ribbon resonators located in appropriate locations. The gates performance is investigated through analytic approaches and verified numerically using the finite difference time domain method. Typical extinction ratio of about 8 dB between ON and OFF logic states has been attained. According to the fantastic feature of voltage-dependent chemical potential of graphene conductivity, the characteristics of the structures can be actively manipulated. These sub-wavelength plasmonic components can be employed extensively in terahertz demanded applications.

Room temperature optical mass sensor with an artificial molecular structure based on surface plasmon optomechanics

We propose an optical weighing technique with a sensitivity down to a single atom through the coupling between a surface plasmon and a suspended graphene nanoribbon resonator. The mass is determined via the vibrational frequency shift on the probe absorption spectrum while the atom attaches to the nanoribbon surface. We provide methods to separate out the signals of the ultralow frequency vibrational modes from the strong Rayleigh background, first based on the quantum coupling with a pump-probe scheme. Owing to the spectral enhancement in the surface plasmon and the ultralight mass of the nanoribbon, this scheme results in a narrow linewidth (∼GHz) and ultrahigh mass sensitivity (∼30 yg). Benefitting from the low noises, our optical mass sensor can be achieved at room temperature and reach ultrahigh time resolution.

Phase-coupled plasmon-induced transparency in integrated metal–dielectric–graphene–dielectric waveguide

We theoretically and numerically investigate the phase-coupled plasmon-induced transparency effect in graphene plasmonic systems that consist of multiple cascade graphene nanoribbon resonators side-coupled to the bus waveguide. The formation of a transparency window is attributed to the superposition of the detuned resonances in graphene nanoribbons. The gap width between the metal and the graphene provides a new degree of freedom for controlling the round-trip phase accumulated in the bus waveguide, which determines the evolution of the transparency window in terms of intensity and symmetry. Our ultracompact configuration can realize slow light with group indices over 250 as well as retain high transmission intensity.

Tunable spectral splitting in nanoscale graphene waveguide with coupled resonators

We propose and investigate a graphene-based resonator-coupled waveguide system comprising input/output graphene sheet bus waveguides and two graphene nanoribbon (GNR) resonators for bandpass spectral splitting. The system is composed of two graphene sheet waveguides and two GNRs located at the same side of the waveguides with different distances. The coupling between two GNRs results in the electromagnetically induced transparency effect and the bandpass spectral splitting. Moreover, benefiting from the chemical-potential-dependent optical properties of graphene, both the spectral symmetry and operation frequency can be dynamically adjusted, separately. The structure can find potential applications for integrated tunable functional devices such as filters and modulators.

Manipulation of slow and superluminal light based on a graphene nanoribbon resonator

We theoretically investigate the phenomena of slow and superluminal light based on a doubly clamped Z-shaped graphene nanoribbon (GNR) nanomechanical resonator driven by two-tone fields. Superluminal and ultraslow probe light without absorption can be obtained via manipulating the pump laser on- and off-resonant with the exciton frequency, respectively. The results indicate that the above phenomena cannot occur without the coupling between graphene resonator and excition in the system. Further, the all-optical schemes for determining the graphene resonator frequency and the coupling strength of excition-resonator in the Z-shaped GNR system are also proposed. The all-optical device based on graphene resonator may have potential application in optical networks and engineering in nanoscale.

Molecular Dynamics Study on Vibrational Properties of Graphene Nanoribbon Resonator

The vibrational properties of nanoelectromechanical system (NMES) resonator based on the defect-free graphene nanoribbon are investigated via classic molecular dynamics simulations. The graphene nanoribbons show ultrahigh fundamental resonant frequencies which can reach 189.6 GHz. The resonant frequencies increase non-monotonically with increasing externally applied force. When the external forces are between 15.912 nN and 44.2 nN, the resonant frequencies of the graphene nanoribbons remain constant at 132.9 GHz. And when the external stress is greater than 44.2 nN, the resonant frequencies show an incremental variation tendency. Temperature has a little influence on resonant frequencies. When the temperature is greater than 75 K, the resonant frequencies of the graphene nanoribbons remain constant at 132.9 GHz. The resonant characteristics of graphene nanoribbons are insensitive to the chirality. The resonant frequencies of the graphene nanoribbon exhibit significant decrease as the length-width ratio increases.

A wavelength demultiplexing structure based on graphene nanoribbon resonators

A wavelength demultiplexing (WDM) structure based on graphene nanoribbon resonators is proposed and numerically investigated by the finite-difference time-domain (FDTD) method. The demultiplexing wavelength can be easily derived by adjusting the length of the resonator, which is accurately explained by the Fabry–Perot (F–P) resonant theory. Meanwhile, the transmission characteristics of the WDM structure are influenced by the coupling distance between the resonator and drop/bus waveguides, and the performance of the WDM device is analyzed at different nanoribbon width and chemical potential. In addition, in order to improve the transmission efficiency from the drop waveguide, a reflection structure is introduced at the end of the bus waveguide. The exact mechanism for the WDM structure is analyzed in detail using the temporal coupled-mode theory. The proposed structure will have potential applications in the field of ultra-compact WDM systems in highly integrated optical circuits.

Developing accelerometer based on graphene nanoribbon resonators

We investigated an ultrahigh sensitive accelerometer based on graphene nanoribbon resonators. Sensing acceleration can be made by their resonance frequency shift and/or their capacitance change. Schematics and the static properties were introduced and the dynamic properties were investigated via classical molecular dynamics simulation. As the acceleration increased, the oscillations of the deflections were going dramatically faster and the mean deflections increased, then the capacitance continually varied with large amplitudes and the resonance frequencies linearly increased in a log–log scale by power regression. The energy loss decreased with increasing time, and the average quality factors were dramatically reduced with increasing acceleration.

Molecular dynamics study on vibrational properties of graphene nanoribbon resonator under tensile loading

We investigated the tension and strain energy variations as a function of the axial strain in static conditions in graphene nanoribbon resonators and the resonance frequency change with tensile loading in dynamic conditions via classical molecular dynamics simulations. This theoretical study presents the application of graphene nanoribbon resonators tuned by tensile loading as ultrahigh frequency devices. The non-linear mechanical properties of the resonators were found, and for small axial strains, the mechanical properties of the graphene nanoribbon, such as strain-energy vs. axial-strain and frequency vs. strain or tension, were estimated by the classical continuum theory. The resonance frequencies increased with increasing axial strain, and such a relation could be regressed by a linearly increasing line on a log–log scale. The increasing resonance frequency due to increasing tension could be regressed by a square root function.

Nanomechanical displacement detection using coherent transport in graphene nanoribbon resonators

Graphene nanoribbons provide an opportunity to integrate phase-coherent transport phenomena with nanoelectromechanical systems (NEMS). Due to the strain induced by a deflection in a graphene nanoribbon resonator, coherent electron transport and mechanical deformations couple. This coupling can be used for sensitive displacement detection in both armchair and zigzag graphene nanoribbon NEMS. Here it is shown that for ordered as well as disordered ribbon systems of length $L$, a strain $\ensuremath{\epsilon}\ensuremath{\sim}{(w/L)}^{2}$ due to a deflection $w$ leads to a relative change in conductance $\ensuremath{\delta}G/G\ensuremath{\sim}({w}^{2}/{a}_{0}L)$, where ${a}_{0}\ensuremath{\approx}1.4$ \AA{}.