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This paper presents a theoretical study on the propagation of electromagnetic surface waves supported by the metamaterial-filled bi-layered graphene structure. The effective surface conductivity approach based upon the Kubo’s formalism is used to model the atomically thick graphene layer, while the analytical modeling of the metamaterials used the framework of causality principle-based Kramers-Kroing relations. With respect to the index of refraction, the two configurations of metamaterials have been considered—i.e., double positive (DPS) and double negative (DNG). The impedance boundary conditions (IBCs) have been employed at the interface for the computation of characteristics equations of odd and even surface modes under DPS and DNG configurations. The numerical results regarding the dispersion relations, effective mode index, and phase speed for the odd and even modes of electromagnetic surface waves supported by each configuration of structure have been presented. Further, the influence of chemical potential and thickness of metamaterial filling in parallel graphene layers on the wave propagation characteristics has been analyzed. To check the accuracy of the numerical results, special conditions were employed, which converge to the published results. The proposed work may have potential applications in plasmonic based logic designs, renewable energy devices, THz surface wave guides, and near-field communication devices.

This study examines the analytical and numerical solution of electromagnetic surface waves supported by a resistive metasurface-covered grounded metamaterial structure. To simulate the metamaterial, the Kramers–Kronig relation based on the causality principle is used, while the modeling of the resistive metasurface has been done by implementing the impedance boundary conditions. The analytical expressions for the field phasors of surface waves are developed for the transverse magnetic (TM) polarized mode and transverse electric (TE) polarized mode. The characteristic equations are computed for both modes, and the unknown propagation constant is evaluated numerically in the kernel. After computation, the dispersion curves, electric field profiles, effective mode index ($$N_{eff}$$ N eff ), and phase speeds ($$v_{p}$$ v p ) are presented for both the TM and TE polarized modes. To study the tunability of surface waves, the influence of the thickness of the metamaterial slab ($$d$$ d ), effective permittivity of the metamaterial ($$\varepsilon_{1}$$ ε 1 ), thickness of the resistive metasurface ($$t$$ t ), and effective permittivity of the metasurface ($$\varepsilon_{r}$$ ε r ) on all the numerical results has been studied. However, the geometrical parameters are found to be more sensitive to the effective mode index ($$N_{eff}$$ N eff ) and phase speed ($$v_{p}$$ v p ) of the surface waves. The results are consistent with the published results, which reflects the accuracy of the work. It is concluded that the appropriate choice of parameters can be used to achieve surface waves with the desired characteristics in the GHz range. The present work may have potential applications in surface waveguide design, surface wave speed controllers, surface communication devices, and light trapping configurations.

Integrating of ferroelectric thin films with two-dimensional materials may provide a novel and unique characteristics in the field of optoelectronics due to the coupling of their distinctive intrinsic features. A heterostructure (bismuth ferrite/zinc oxide) device is fabricated with different types of the electrode to enhance the power conversion efficiency (PCE). A single-phase multiferroic BFO thin film is grown by atomic layer deposition (ALD) method and annealed in different environments such as helium, nitrogen, and oxygen. We investigated the effect of annealing parameters and different types of electrodes on solar cell applications. We observed that the leakage current 10 orders of magnitude was reduced by decreasing in the dielectric loss. Further, the power conversion efficiency (PCE) is improved from 4.1% to 7.4% with a hybrid transparent electrode (graphene/indium tin oxide). The value of PCE is further increased at a low temperature. So, the improvement in the key parameter of bismuth ferrite thin-film evidently highlights the importance of annealing atmosphere and graphene as an electrode in BFO thin film applications in optoelectronics.

A theoretical investigation has been carried out on the propagation of hybrid surface waves supported by a chiral loaded resistive metasurface. The canonical boundary-value problem approach is used in the analytical modeling of this problem. To simulate the resistive metasurface, an impedance boundary condition is applied at the chiral-resistive metasurface interface. The characteristics equation was solved numerically in the kernel for computing the unknown value of the propagation constant ( $$\beta $$ ) against its respective frequency ( $$\omega $$ ). The numerical results reveal that the chiral loaded resistive metasurface supports the upper and lower hybrid surface modes in the GHz range. The propagation bandgap between the upper and lower hybrid surface modes is highly sensitive to the chiral strength (ξ), and the propagation bandgap can be tuned with the variation of chirality. The surface wave characteristics i.e., the dispersion curve, effective mode index ( $${N}_{\mathrm{eff}}$$ ), field profiles, and phase speeds ( $${v}_{p}$$ ), have been computed numerically for both the upper and lower hybrid surface modes. The influence of chirality (ξ), thickness ( $$t$$ ), permittivity of chiral medium ( $${\varepsilon }_{c}$$ ), and the permittivity of resistive metasurface ( $${\varepsilon }_{r}$$ ) on the resonance frequency, confinement, and phase speed of surface waves have been analyzed and their tunability has been discussed. The results’ validity has been checked under special conditions and the numerical results converge to the published results. The presented numerical results may have potential applications in chip chiral sensing, enantiomeric detection, biochemical sensing, metasurface designing, and near-field hybrid surface communication devices.

Theoretical investigations are carried out to study hybrid SPP wave propagation along the Chiral-Graphene-Metal (CGM) interface. The Kubo formulism is used for the physical modeling of single-layer graphene and the impedance boundary conditions approach is applied at the CGM interface to compute the dispersion relationship for hybrid SPP waves. It is demonstrated that the chirality (ξ) and chemical potential (μc) parameters can be used to modulate the resonance surface plasmon frequencies of the upper and lower propagating modes. Furthermore, the propagation bandgap between the upper and the lower modes can be tuned by changing the chirality parameter. The effect of the chemical potential (μc)and the relaxation time (τ) on the normalized propagation constant, propagation length, and the effective refractive index is studied. The present work may have potential applications in optical and chiral sensing in the terahertz frequency range.

Terahertz (THz) wave interaction from graphene coated metamaterial cylinder has been investigated analytically and numerically. The analytical formulation of electromagnetic fields is being modeled in the frame work of Mie theory while the modeling of the graphene is done by random phase approximation method. The causality principle based Kramer-Kroing relations are used to simulate the DNG metamaterial, while the DPS metamaterial is modeled by the Drude relations of SiO2. The analytical formulation is developed for both parallel and perpendicular polarized waves. The impedance boundary conditions (IBC) approach is used to model the infinitely thin graphene coating on metamaterial cylinder. Further the IBC at the interface of graphene layer and metamaterial cylinder are applied to compute the unknown scattering coefficients. The efficiency factors i.e., scattering efficiency (Qsca), extinction efficiency (Qexc) & absorption efficiency (Qabs) and bistatic radar cross section (RCS) have been computed analytically as well as numerically for both micro and nano cores. The influence of graphene parameters i.e., chemical potential (μc) & scattering rate (τ1) and size of metamaterial cylinder (R) on the scattering efficiency (Qsca) and extinction efficiency (Qexc) has been analyzed for DPS and DNG cores. It is observed that the in the nano regime, for perpendicularly polarized wave, graphene coated metamaterial cylinder supports the localized surface plasmon resonance (LSPR) modes and LSPR is found sensitive to the change in the graphene parameters and core size. However, it is reported that the parallel polarized wave has same response towards the DPS and DNG cores in the nano regime. It is concluded that under suitable parameters the graphene coating may provide extraordinary degree of freedom to actively control the THz interactions i.e., scattering efficiency, extinction efficiency and bistatic RCS. The present work may have potential applications in designing and manufacturing of Electromagnetic invisibility, cloaking and target protection devices for THz region. Keywords: Scattering, Absorption, Metamaterials, Graphene, Cylinder, Eco width, Radar Cross Section (RCS), Efficiency Factors, Surface Plasmon Resonance

The active tuning of surface waves supported by left-handed materials (LHMs) is a major challenge for their practical applications and usability, and graphene has been proposed as an agent for the active tuning of surface waves. In this study, tunable surface waves supported by graphene-layered LHM structures are investigated theoretically. The analytical and numerical results are computed for transverse electric (TE) and transverse magnetic (TM)-polarized surface waves. According to the spectral range, two configurations of LHMs (i.e., gigahertz (GHz)-LHM and terahertz (THz)-LHM) are discussed. The physical modeling of graphene is done using the conductivity model based on random phase approximation-based Kubo formalism. The split ring resonator (SRR) model and Kramers–Kronig relations-based causality principle are used for the physical realization of LHMs. To simulate the graphene-layered LHM interface, impedance boundary conditions (IBCs) are applied. Numerical results are computed for dispersion curves, effective wave numbers, and field profiles of surface waves supported by graphene-covered GHz-LHM and THz-LHM. The influence of graphene parameters on the resonance frequency, dispersion curves, and confinement characteristics of surface waves is analyzed for both configurations of LHMs. It is concluded that the graphene-covered GHz-LHM structure supports the tunable surface waves as surface plasmon polaritons (SPPs) support TM-polarized waves. However, with the TE-polarized surface wave, the structure supports the surface polaritons, which do not depend upon the graphene parameters. For the case of the graphene-covered THz-LHM structure, it is concluded that the structure supports the plasmon modes for both polarized waves and the resonance frequency ranges from THz to infrared (IR). The confinement of the TE-polarized surface waves on the graphene layer can be enhanced up to fourfold as compared to the suspended monolayer graphene by using a THz-LHM substrate. Further, the numerical results are found to be consistent with the literature under special conditions. The proposed graphene-layered LHM structure may have potential uses in the active tuning of surface waves, near-field communication and imaging devices, surface waveguide design, and LHM-based metasurfaces.

In-depth analysis of hybrid SPP wave propagation at the Chiral–Graphene–Dielectric (CGD) interface is carried out. The single-layer graphene is modeled using Kubo formulism and the impedance matching boundary conditions are utilized to derive the dispersion relation. TM-TE decoupled modes at the CGD interface are shown. The effective mode index and propagation length of hybrid plasmon modes are found to be sensitive to chiral strength (ξ), chemical potential (μc), radius of waveguide, and refractive index of chiral (nc). It is observed that the cutoff values of chiral strength and radius promote Goos–Henchen effect at CGD interface. The present work may have potential applications for on-chip optical, chiral sensing and enantiomeric detection and renewable energy technologies in the terahertz frequency regime.

Bismuth ferrite is a multiferroic material which shows high magnetization and polarization at room temperature. In present work, the effect of Oxygen (O) vacancies on magnetic properties of bismuth ferrite nanoparticles is studied. Bismuth ferrite nanoparticles (BiFeO3) were synthesized by solution evaporation method (SEM) at room temperature. The sample was annealed under two different atmospheres such as in air and oxygen, to check the effect of O-vacancies on magnetic properties. The average crystallite size of Bismuth ferrite nanoparticles (NPs) as calculated by X-ray diffraction (XRD) falls in the range of 23–32 nm and 26–39 nm for the case of air and oxygen respectively. The crystallite size of bismuth ferrite nanoparticles increases as the temperature was varied from 450 °C to 650 °C. Further the influence of annealing temperature on the magnetic properties of the bismuth ferrite nanoparticles was also observed. It was concluded that the magnetic properties of Bismuth ferrite nanoparticles are directly interconnected to annealing atmosphere and annealing temperature. The magnetic properties were increased in the case of oxygen annealing, which actually leads in our case to an improvement of the crystallinity.

Theoretical investigation has been carried out to study the scattering and transmission of electromagnetic energy from isotropic plasma coated circular nihility cylinder. The physical modeling of the problem is done in frame work of classical scattering theory. All the fields are expanded in terms of cylindrical vector wave functions (CVWFs). The analytical as well as numerical solution for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations is presented. The unknown scattering coefficients are computed by implementing the boundary conditions at each interface (free space/plasma and plasma/nihility). The influence of plasma parameters i.e., plasma density (ND) and effective collision frequency (v) on the bistatic echo width is analyzed and it is concluded that the plasma coating can be used to control and tune the scattering amplitude. Further it is also concluded that for the case ω > ωp the scattering amplitude is much less than for the case ω < ωp. Under special conditions, the results of present work compared with the published literature and good agreement is found.