Semi-infinite Dielectric Medium Research Articles

Comprehensive Multimode Reflection Analysis of a Dielectric-Loaded Rectangular Waveguide Terminated by Semi-Infinite Dielectric Media

This article presents a comprehensive multimode reflection analysis of a dielectric-loaded rectangular waveguide terminated by semiinfinite dielectric media. A Fourier-based analysis approach is extended for different incident modes of the waveguide to calculate the amplitude coefficients of the reflected modes when the flange or the waveguide walls have different finite conductivities. We calculate the complex propagation constant using the method of perturbation of the boundary conditions. The modal scattering parameters are defined based on the voltage wave normalized amplitudes to be valid for both propagating and evanescent fields. The inclusion of coupled and noncoupled modes in the solution is evaluated in terms of calculation time and the accuracy of the results. An algorithm is presented to calculate the reflection coefficient of variations in terms of the coupled modes included in the solution. It is shown that these variations are dependent on the operating frequency and dielectric properties used in the geometry. Our results are compared with 3-D full-wave simulations, and an excellent agreement is achieved over a wide frequency range by using the primary coupled modes in the solution. The modal aperture admittance is calculated for different modes to show the coupled modes’ effect on the results. Also, the proposed algorithm is modified to find the effective coupled modes much faster. These modes are used to obtain accurate results for different dielectric-loaded structures.

A kinetic treatment of surface plasmon polaritons in the Voigt configuration

The study of microscopic effects on the dispersion of surface magnetoplasmon polaritons is important. We use the collisionless Vlasov equation and Maxwell’s equations to evaluate the dielectric tensor for evaluating the dispersion relations of surface magnetoplasmon polaritons. We treat the case in the Voigt geometry assuming a semi-infinite dielectric medium. The direction of the magnetic field is considered parallel to the surface and perpendicular to the propagation vector k. The analysis shows the influence of additional microscopic kinetic effects. Standard Drude model results are retrieved in the absence of these effects.

Effect of Uniform Strain on Graphene Surface Plasmon Excitations

This paper reports a study of the reflectance of the optical sensors based on graphene under uniform strain. Assuming the graphene layer is surrounded by two different semi-infinite dielectric media, the generalized Fresnel coefficients are derived as a function of usual quantities (e.g., dielectric constants, incident angles, and strain) and anisotropic optical conductivity. The strain not only changes the electronic band structure but also can be employed to tune the electronic collective excitations (plasmons) and thus the optical reflectance of graphene monolayers. One of the most common techniques for plasmon excitation is the Kretschmann configuration. It is based on the observation of a sharp minimum in the reflection coefficient versus the angle (or wavelength) curve. Because strain induces anisotropy in graphene optical conductivity the strain-dependent orientation plays an important role to manipulate the variation of graphene plasmon energy, which may be useful to synchronize graphene properties in plasmonic devices to enhance light-matter interactions.

Антиклассическое приближение в задаче об отражении электромагнитной волны от неоднородной среды

Expressions are derived for the reflection coefficients of electromagnetic waves with "p" and "s" type polarizations from a semi-infinite dielectric medium having an inhomogeneous layer. The influence of the layer was taken into account by the method of perturbation theory in a quadratic approximation of the layer thickness. A method is proposed for converting expressions derived using perturbation theory into other expressions that give more accurate values of the reflection coefficient. The angular dependences of the reflection coefficient obtained by the developed method are compared with those obtained by the numerical solution of electrodynamic equations. Requirements for the layer characteristics are formulated to minimize the error of the analytical solution.

Three-dimensional electric potential induced by a point singularity in a multilayered dielectric medium

A simple and effective method is proposed to derive the three-dimensional electric potential induced by a point singularity of any type in an N-phase dielectric medium composed of N−2 intermediate dielectric layers of equal thickness encased in two semi-infinite dielectric media. The point singularity can include a point charge or a point electric dipole. The original boundary value problem for the N-phase medium is reduced to the determination of a single unknown three-dimensional harmonic function through satisfaction of the continuity conditions across all of the N−1 perfect planar interfaces. The single harmonic function can be completely determined after analytically solving the resulting linear recurrence relations, which are independent of the type and the specific location of the singularity. When the singularity is a point charge, we obtain the self-energy of the point charge expressed in terms of a single function and the Coulomb force on the point charge expressed in terms of the negative derivative of this function.

Tunable surface waves in nonlinear graphene-based one-dimensional-photonic crystal

The nonlinear TE surface waves guided by an interface of a semi-infinite Kerr-type dielectric medium and a one-dimensional graphene-based photonic crystal have been investigated using the transfer-matrix method. It is shown that increasing the intensity of the incident beam drastically changes dispersion behavior inside the graphene-induced photonic band gap as a result of nonlinearity. Also regarding the simulation results, it reveals that the peculiar dispersion that is governed by a nonlinear structure appeared to be tuned by graphene conductivity via an external electric field. Applying such an electric field makes it possible to easily tune the nonlinear surface waves at the desired frequency only by adjusting the chemical potential of the graphene. Also, it is shown that for application purposes, the results of studies can be applied to the case in which graphene nanolayers are embedded by identical dielectric constant, i.e., zero permittivity contrast of dielectric.

Tension effect on the absorbance of a graphene layer

The effect of uniform planar tension on the absorbance of a graphene layer located between air and a semi-infinite dielectric medium has been investigated. The results show that the magnitude of the Van Hove peaks in the absorbance of the graphene depends on the tension direction, the strain modulus and the angle between the tension direction and the tangential electric field. While, the frequency location of the Van Hove peaks only depends on the tension direction and the strain modulus and is independent from the angle between the tension direction and the tangential electric field. When the tangential electric field is perpendicular to one of the vectors connecting a given carbon atom to its nearest neighbours, the related peak disappears. While, for the tangential electric field parallel to those vectors, the related peak acquires its largest value. Moreover, it is shown that the absorbance of the graphene layer at the low photon energies doesn’t noticeably depend on the tension direction, the strain modulus and the angle between the tension direction and the tangential electric field.

Multibeam interferometric optical tweezers

Using the interference of N collimated laser beams, optical lattices with N-fold rotational symmetry are generated over the interface of two semi-infinite dielectric media. The interaction of small dielectric particles with these interference patterns is investigated using Rayleigh approximation. The polarization state of the interfering beams considerably influences the interference patterns and potential landscapes. Therefore, both parallel and perpendicular polarized interfering beams are considered and the corresponding potential profiles are compared and analyzed. We also study how the number of interfering waves, incident and azimuth angles, and initial phases of the incident beams influence optical lattices and potential profiles. It is found that the ring-shaped patterns with good confinement properties can be achieved by increasing the number of incident beams. In addition, by increasing the number of incident beams one can make an optical trap with sharper intensity gradient and deeper potential well, which is an advantage for trapping small Rayleigh particles. The lattices resulting from the interference of N incident waves with different incident angles are also investigated. Furthermore, the effects of changing the azimuth angles between two adjacent incident wave vectors on the intensity patterns are studied. The proposed configuration and the numerical results can find numerous applications in particle arrangement, particle sorting, and the creation of quasicrystals. We believe that interference approaches have many potential capabilities for molding light wavefronts and creating multiple traps with sophisticated patterns.

Experimental and numerical studies of the scattering of light from a two-dimensional randomly rough interface in the presence of total internal reflection: optical Yoneda peaks.

The scattering of polarized light from a dielectric film sandwiched between two different semi-infinite dielectric media is studied experimentally and theoretically. The illuminated interface is planar, while the back interface is a two-dimensional randomly rough interface. We consider here only the case in which the medium of incidence is optically more dense than the substrate, in which case effects due to the presence of a critical angle for total internal reflection occur. A reduced Rayleigh equation for the scattering amplitudes is solved by a rigorous, purely numerical, nonperturbative approach. The solutions are used to calculate the reflectivity of the structure and the mean differential reflection coefficient. Optical analogues of Yoneda peaks are present in the results obtained. The computational results are compared with experimental data for the in-plane mean differential reflection coefficient, and good agreement between theory and experiment is found.

Interference effects in the plasmon fields excited by a diatomic molecule

We study the fluctuations of the plasmon field associated to the wake potential generated by a dimer formed by two identical charged particles (such as two nuclei of the ionized hydrogen molecule) traveling through a semiinfinite dielectric medium. We use coherent states to describe bulk and surface plasmons as wave packets that raise fluctuations in the electronic density of the material. We analyze different configurations of interest, taking into account various trajectories and orientations of the dimer.

Fluctuation of electronic density in the plasmon fields excited by a diatomic molecule

We study the fluctuations of the electronic density due to plasmon field associated to the wake potential generated by a dimer formed by two identical charged particles (such as two nuclei of the ionized hydrogen molecule) traveling through a semi-infinite dielectric medium. We use coherent states to describe plasmons as wave packets that raise fluctuations in the electronic density of the material. We analyze different configurations of interest, regarding the geometry of the surface and the orientation of the dimer.

Interaction of Bessel Light Beams with Epsilon-near-zero Metamaterials

The article explores possibilities and conditions of generation of a new type of diffraction-free needle-like field Bessel plasmon polaritons (BPPs) with super narrow cone angle in an epsilon-near-zero metamaterial, surrounded by semi-infinite dielectric media. Correct analytical expressions are obtained and analyzed in detail for the electric and magnetic fields of BPPs formed inside and outside the metamateral slab.

Antireflection Coating at Metamaterial Waveguide Structure by Using Superlattices (LANS)

The characteristics of electromagnetic wave reflection and transmission by multilayered structures consisting of a pair of left-handed material (LHM) and superlattices (LANS) slabs inserted between two semi-infinite dielectric media are investigated for photovoltaic and solar energy applications. Maxwell’s equations are used to determine the electric and magnetic fields of the perpendicular polarized wave incident at each layer. Snell’s law is applied and the boundary conditions are imposed at each layer interface to calculate the reflected and transmitted coefficients of the structure. The reflected, transmitted powers are determined using these coefficients by a recursive method. The reflected and transmitted powers are computed in both visible and microwave spectral band with the appropriate LHM for each band and appropriate location of LANS in the structure. They are illustrated as a function of the incident wavelength, angle of incidence, magnetic fraction of LANS and thickness of the slabs with the emphasis on the appropriate refractive indices. I found that, zero reflectance and maximum transmittance of the incident powers are achieved for visible spectral band at a single frequency if LHM and LANS have the same refractive index of opposite signs with the same width and more magnetic material of LANS while the reflected power is zero for less magnetic material of LANS in the microwave spectral band which realizes antireflection coating in this structure.

Ultrahigh refractive index sensitivity of TE-polarized electromagnetic waves in graphene at the interface between two dielectric media

The behavior of the TE and TM electromagnetic waves in graphene at the interface between two semi-infinite dielectric media is studied. The dramatic influence on the TE waves propagation even at very small changes in the optical contrast between the two dielectric media is predicted. Frequencies of the TE waves are found to lie only in the window determined by the contrast. We consider this effect in connection with the design of graphene-based optical gas sensor. Near the frequency, where the imaginary part of the conductivity of graphene becomes zero, ultrahigh refractive index sensitivity and very low detection limit are revealed. The considered graphene-based optical gas sensor outperforms characteristics of modern volume refractive index sensors by several orders of magnitude.

Tunable hybrid surface waves supported by a graphene layer

We study electromagnetic waves localized near the surface of a semi-infinite dielectric medium covered by a graphene layer in the presence of a strong external magnetic field. We demonstrate that a novel type of hybrid TE-TM polarized surface plasmons can propagate along the graphene layer. We analyze the effect of the Hall conductivity on the polarization properties of these hybrid surface waves and suggest a possibility to tune the graphene plasmons by the external magnetic field.

Finite-difference time-domain and near-field-to-far-field transformation in the spectral domain: application to scattering objects with complex shapes in the vicinity of a semi-infinite dielectric medium

We present the study of a spectral-domain near-field-to-far-field (NFTFF) transformation, taking into account an interface in the vicinity of a particle. This technique is associated with a three-dimensional finite-difference time-domain (FDTD) model, which solves the Maxwell equations in the time domain. Moreover, material properties are considered with the use of dispersion models. First, particular attention is paid to the description of the modeling, especially concerning the NFTFF transformation using the dyadic Green tensors. Second, several simulation cases are considered to evaluate the ability of the developed technique to model the scattering by different kinds of "particles/interface" configurations and for various illuminating waves. Then validation test cases are used in order to assess the model accuracy through comparisons with T-matrix simulations. Finally, perspectives to this work and its application to near-field detection devices are discussed.

Optical antireflection of a medium by nanocrystal layers

Optical properties of a semi-infinite dielectric medium comprising a monolayer quasi-crystal of nanoparticles are considered. It is shown that imbedding a single layer of nano-objects regularly distributed in space under certain conditions may provide close to 100 % transmission of the medium in a wide spectral range.

Effect of negative permittivity and permeability on the transmission of electromagnetic waves through a structure containing left-handed material

We investigate the characteristics of electromagnetic wave reflection and transmission by multilayered structures consisting of a pair of left-handed material (LHM) and dielectric slabs inserted between two semi-infinite dielectric media. The theoretical aspect is based on Maxwell's equations and matching the boundary conditions for the electric and magnetic fields of the incident waves at each layer interface. We calculate the reflected and transmitted powers of the multilayered structure taking into account the widths of the slabs and the frequency dependence of permittivity and permeability of the LHM. The obtained results satisfy the law of conservation of energy. We show that if the semi-infinite dielectric media have the same refractive index and the slabs have the same width, then the reflected (and transmitted) powers can be minimized (and maximized) and the powers-frequency curves show no ripple. On the other hand if the semi-infinite dielectric media have different values of refractive indices and the slabs have different widths, then under certain conditions the situation of minimum and maximum values of the mentioned powers will be reversed.

Effects of Loss Factor on Plane Wave Propagation through a Left-Handed Material Slab

This article presents a theoretical and numerical discussion of the reflection and transmission analysis through a lossy left-handed material slab embedded between two semi-infinite dielectric media. The properties of the lossy left-handed material are given in detail and the required equations for the electromagnetic plane wave propagation are derived to solve the problem. The main important contribution of this article is the characterization of left-handed material that is different from its counterpart known in the literature. After introducing the left-handed material slab, the analytical solution is found for the powers carried by an electromagnetic wave. Then, the reflected, the transmitted, and the loss power are computed in terms of the incidence angle, the frequency, and the slab thickness in the numerical results with the emphasis on the loss factor.

Acoustic surface plasmons in a finite p-n junction

It is demonstrated that acoustic surface plasmons obeying a linear dispersion relation can exist in a finite p-n junction confined between semi-infinite dielectric media. The conditions of propagation of such plasmons are considered.