Surface Conductivity Model Of Graphene Research Articles

Numerical analysis of optical phase modulator operating at 2 μm wavelength using graphene/III–V hybrid metal-oxide-semiconductor capacitor

We propose an optical phase modulator with a hybrid metal-oxide-semiconductor (MOS) capacitor, consisting of single-layer graphene and III–V semiconductor waveguide. The proposed modulator is numerically analyzed in conjunction with the surface conductivity model of graphene. Since the absorption of graphene at a 2 μm wavelength can be suppressed by modulating the chemical potential of graphene with the practical gate bias, the phase modulation efficiency is predicted to be 0.051 V·cm with a total insertion loss of 0.85 dB when an n-InGaAs waveguide is used, showing the feasibility of the low-loss, high-efficiency graphene/III–V hybrid MOS optical phase modulator, which is useful in the future 2 μm optical fiber communication band.

基于石墨烯的光学控制窄带太赫兹开关

This paper proposes an optically controlled terahertz switcher based on cross-shaped metal resonators metasurface covered by monolayer graphene. The spectral characteristics of proposed composite structure were calculated using the surface conductivity model of graphene and the finite element method. The modeling demonstrated the appearance of a narrowband resonant dip in the transmission spectrum with a modulation depth of 36.8% and a Q-factor of 250 after the optical pump intensity achieving to 0.2 W/mm2. In addition, the modulation depth of such a dip can be slightly tuned by varying value of the pump intensity. Thus, the design of the optically tunable terahertz switcher may contribute to the development of functional components for terahertz communication applications.

Erratum: “Dyadic Green's functions and guided surface waves for a surface conductivity model of graphene” [J. Appl. Phys. 103, 064302 (2008)

Erratum: “Dyadic Green's functions and guided surface waves for a surface conductivity model of graphene” [J. Appl. Phys. 103, 064302 (2008)

Excitation of discrete and continuous spectrum for a surface conductivity model of graphene

Excitation of the discrete (surface-wave/plasmon propagation mode) and continuous (radiation modes) spectrum by a point current source in the vicinity of graphene is examined. The graphene is represented by an infinitesimally thin, local, and isotropic two-sided conductivity surface. The dynamic electric field due to the point source is obtained by complex-plane analysis of Sommerfeld integrals, and is decomposed into physically relevant contributions. Frequencies considered are in the GHz through mid-THz range. As expected, the TM discrete surface wave (surface plasmon) can dominate the response along the graphene layer, although this depends on the source and observation point location and frequency. In particular, the TM discrete mode can provide the strongest contribution to the total electric field in the upper GHz and low THz range, where the surface conductivity is dominated by its imaginary part and the graphene acts as a reactive (inductive) sheet.

Dyadic Green’s functions and guided surface waves for a surface conductivity model of graphene

An exact solution is obtained for the electromagnetic field due to an electric current in the presence of a surface conductivity model of graphene. The graphene is represented by an infinitesimally thin, local, and isotropic two-sided conductivity surface. The field is obtained in terms of dyadic Green’s functions represented as Sommerfeld integrals. The solution of plane wave reflection and transmission is presented, and surface wave propagation along graphene is studied via the poles of the Sommerfeld integrals. For isolated graphene characterized by complex surface conductivity σ=σ′+jσ″, a proper transverse-electric surface wave exists if and only if σ″>0 (associated with interband conductivity), and a proper transverse-magnetic surface wave exists for σ″<0 (associated with intraband conductivity). By tuning the chemical potential at infrared frequencies, the sign of σ″ can be varied, allowing for some control over surface wave properties.