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To investigate the sensing properties of the Faraday effect in graphene in terahertz (THz), we consider the modulations of Dirac gaps in graphene when gas molecules are adsorbed to its surface. Here, the effect of the associated bandgap opening in graphene's spectrum on the sensing properties of the Faraday rotation (FR) in a 1D photonic graphene-based sensor with a microcavity defect channel covered by two graphene layers. Our proposed model introduces an optical contact-free mechanism for detecting low-concentration molecules attached to graphene's surface. We also show that FR angles could reveal reversal signs for a different amount of surface transfer doping. Finally, the effect of increasing the temperature on the Faraday effect at a certain opening gap in graphene's spectrum is investigated. Interestingly, stronger FR effect it was observed at higher temperatures. Our results could open the path for development of contact-free sensing applications in THz region. • Terahertz (THz) sensing of low-concentration molecules based on Faraday effect is introduced. • Effect of the energy bandgap of graphene on Faraday effect is investigated. • Faraday angle in a 1D photonic graphene-based sensor with a microcavity defect channel covered by two graphene layers is measured. [ABSTRACT FROM AUTHOR]

We investigate the effect of a perpendicular static magnetic field on the optical bandgap of a one-dimensional (1D) graphene-dielectric photonic crystal in order to examine the possibility of reaching a rich tunable photonic bandgap. The solution of the wave equation in the presence of the anisotropic Hall situation suggests two decoupled circularly polarized wave each exhibiting different degrees of bandgap tunability. It is also numerically demonstrated that applying different values of field intensity lead to perceptible changes in photonic bandgap of such a structure. Finally, the effect of opening a finite electronic gap in the spectrum of graphene on the optical dispersion solution of such a 1D photonic crystal is reported. It is shown that increasing the value of the electronic gap results in the shrinkage of the associated photonic bandgaps. [ABSTRACT FROM AUTHOR]

The existence of a photonic bandgap in the visible range of light spectrum corresponding to a 1D graphene-based photonic crystal which recently has been proposed and is formed by embedding alternatively graphene layers into a dielectric background is investigated in this paper. By the use of the complete form of optical conductivity for the full expression of the tight-binding Hamiltonian of graphene layer, we numerically demonstrate an appeared bandgap in the visible region of the spectrum which can open up new route for further high-frequency applications of graphene-based photonic devices. It is revealed that the associated bandgap could be altered by changing the hopping energy and the amount of chemical potential leading to broadening the forbidden frequency regions with further increasing. Finally, it is also shown that the tunability feature of the photonic bandgap could be affected by changing the hopping energy. [ABSTRACT FROM AUTHOR]

• The existence of SPRs for graphene in the visible domain a 1D truncated PC was shown. • We demonstrated the effect of the chemical potential and hopping parameter on the dip modulations of SPRs. • We showed that the changes in the refractive index of the sensing medium affects SPRs in the visible domain. Visible surface plasmon resonances (SPRs) could be excited by TE wave polarization in one-dimensional photonic crystals (PCs) coated by a graphene layer under the Kretschmann configuration. In this work, the plasmonic Bloch wave properties beyond Dirac points in a one-dimensional graphene-based photonic sensing structure have been numerically studied. We demonstrate that emergent plasmonic dips in the reflectance spectra of the suggested photonic device in the visible region exhibit tunable characteristics upon modulation of the chemical potential and the hopping parameter. The sensitivity of the sensor in the visible domain has been numerically evaluated and also was compared with those considering the surface plasmon resonances in the terahertz regime. [ABSTRACT FROM AUTHOR]

The presence of two defect layers in a one-dimensional photonic crystal which could be described numerically by the transfer matrix model becomes important when two defects modes might be controlled by the number of the middle layers. In this work, we compute the transmission spectra of a 1D photonic crystal with two graphene-based defect layers in the presence of an applied constant magnetic field. It is observed that an additional defect mode shows up at the lower edge of the photonic bandgap of the optical structure which could to be tuned by the Fermi energy, the intensity of the magnetic field and also the number of the layers between the defects. In addition, we investigated the effect of decreasing the number of middle layers on the transmission spectra of the photonic device. • We proved the existence of two defect modes with different properties. • We demonstrate that left and right handed defect modes exhibit a step-like transmission map. • We show that the middle layers between two defects affect the lower-edge defect modes. [ABSTRACT FROM AUTHOR]