Uniaxial Slab Research Articles

各向异性晶体的平板负折射成像研究

各向异性晶体的平板负折射成像研究

Wide angle conoscopic interference patterns in uniaxial crystals

The fringe pattern obtained when a divergent (or convergent) beam goes through a sample of birefringent crystal between two crossed polarizers contains information that is inherent to the crystalline sample under study. The formation of fringe patterns is analyzed from distinct approaches and with different degrees of approximation considering cones of light of large numerical aperture. We obtain analytic explicit formulas of the phase shift on the screen and compare them with the exact numerical solution. The results obtained are valid for arbitrary orientation of the optical axis and are not restricted either to low birefringence or to small angles of incidence. Moreover, they enable the extraction of the main features related to the characterization of uniaxial crystal slabs, such as the optical axis tilt angle and the principal refractive indices.

Experimental Characterization of Chiral Uniaxial Bianisotropic Composites at Microwave Frequencies

This paper presents an experimental procedure for retrieving the effective constitutive parameters of chiral materials. Unlike past research that primarily deals with isotropic materials, this study considers a lossy uniaxial bianisotropic slab with a nonzero chirality along its axial direction. First, plane-wave scattering off the uniaxial slab in a free-space environment is studied analytically. This forward analysis gives insight into the problem and the choice of proper independent measurements required for the inverse process, i.e., retrieving the slab constitutive parameters from its S-parameters. Based on this analysis, three sets of co-polarized and cross-polarized S-parameters are required, including both the transmission and reflection coefficients of the slab. Given the measured scattering data, the complex permittivity, permeability, and chirality tensors are determined numerically using the results of the analytic study. To test the performance of the new retrieval method, an array of 2 × 56 long, metallic helices is designed and fabricated for operation at C-band. Having the same handedness, the helices are closely spaced and held in parallel to each other in a wooden frame in order to create an effective uni-axial chiral medium. A conventional transmission/reflection setup measures the array scattering parameters, which are fed into the retrieval process to obtain the effective parameters. The measured parameters well model the array scattering response, exhibiting a significant averaged chirality of ~0.4 over 5.5-8.7 GHz and a plasmonic behavior at ~7.1GHz.

THE REFLECTION AND TRANSMISSION OF ELECTROMAGNETIC WAVES BY A UNIAXIAL CHIRAL SLAB

The re∞ection and transmission of electromagnetic waves obliquely incident on a uniaxial chiral slab with the optical axis perpendicular to the interface have been investigated. Firstly, the formulas of the re∞ection and transmission are derived. Then numerical results for four cases of the uniaxial chiral media are presented and difierent chiral parameters are considered. Finally, the Brewster's angles and total transmission are discussed.

Metamaterial focusing device for microwave hyperthermia

AbstractThis work shows a microwave focusing device based on metamaterials which can find application in hyperthermia of tumors. The device consists of an array of split‐ring resonators placed between two parallel metal plates. Both the fields and the temperature distribution are numerically obtained in a model of breast tissue and a tumor by modeling the device as a homogeneous uniaxial slab of negative permeability placed between the two metal plates. The theoretical predictions about the field distribution have been experimentally checked by measuring the field produced by the fabricated device inside a phantom resembling the breast tissue. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2868–2872, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26434

Electromagnetic tunneling of obliquely incident waves through a single-negative slab paired with a double-positive uniaxial slab

We show that, under appropriate oblique-incidence and polarization conditions, the inherent opaqueness of a homogeneous, isotropic single-negative slab may be perfectly compensated (in the ideal lossless case) by a homogenous, anisotropic (uniaxial) double-positive slab, so that complete tunneling (with total transmission and zero phase delay) occurs. We present an analytical and numerical study aimed at deriving the basic design rules, elucidating the underlying physical mechanisms, and exploring the role of the various involved parameters.

Rainbow-like radiation from an omni-directional source placed in a uniaxial metamaterial slab

In this paper, the radiation of an omni-directional line source placed in a uniaxial metamaterial slab is experimentally presented. The anisotropic slab made of metallic symmetrical rings with dispersive permeability is investigated both theoretically and experimentally. For low value of the permeability, a directive radiation at the broadside of the slab can be obtained. Due to the excitation of the leaky wave mode supported by this structure, the emitted electromagnetic wave transmits at a greater angle from the normal of the slab as the value of permeability increases along with the frequency. Thus a rainbow-like radiation will be formed since waves of different frequencies will deflect into different directions.

GROUNDED UNIAXIAL MATERIAL SLABS AS MAGNETIC CONDUCTORS

The objective of this paper is all-angle artiflcial magnetic conductor, i.e., artiflcial magnetic conductor that has stable magnetic- wall efiect with respect to the incidence angle. Furthermore, we seek for a design that would be easy for manufacturing. In order to achieve this we use grounded uniaxial material slabs and we do not constrict ourselves to naturally available materials. Instead, we assume that the desired parameters can be synthesized using the emerging artiflcial electromagnetic materials. It is found that it is possible to have an all-angle magnetic-wall efiect for both TE and TM polarization. Especially for the TM flelds the structure would be easily manufacturable. The proposed structure has similar appearance as more well-known artiflcial impedance surfaces, but the design parameters and the physical properties behind the magnetic wall efiect are novel. The performance of the proposed artiflcial magnetic conductor is verifled with numerical simulations. This paper introduces a new approach how to obtain a magnetic-wall efiect. It is possible to use this this approach also together with other ways of obtaining the magnetic-wall efiect for dual-band operation.

Reflection and transmission of weakly inhomogeneous anisotropic and bianisotropic layers calculated by perturbation method

With the use of perturbation theory the zero- and higher-order approximations are obtained for characteristic matrices, reflection and transmission operators, scalar reflectance and transmittance of monochromatic electromagnetic waves impinging on a transparent weakly inhomogeneous stratified bianisotropic medium. The proposed procedure of perturbation series formation enables finding the corrections to the reflection and transmission factors in closed form for specified coordinate dependencies for the material tensors of the bianisotropic layers. The general expressions obtained are applied to calculate the first-order corrections for normal incident light on (i) a twisted uniaxial slab, (ii) an isotropic medium with arbitrary inhomogeneity profile and (iii) a one-dimensional photonic crystal with arbitrary number of layers. Exact and approximate solutions of the wave equations are numerically compared.

Uniaxial crystal slabs as amphoteric-reflecting media

Amphoteric-refracting properties of uniaxial crystals have been both theoretically studied and experimentally observed. In this paper, the theoretical analysis of the amphoteric-refracting property for uniaxial crystals is extended to reflection of light on the basis of previous studies. Theoretical prediction and experimental observation of amphoteric-reflecting properties at the second planar interface of uniaxial crystal slabs are presented. Three possible phenomena relating to combinations of the refraction and the reflection at the second planar interface are discussed: negative refraction with negative reflection, positive refraction with positive reflection, and positive refraction with negative reflection. It is found that negative reflections can occur at a wide angular range in uniaxial crystals by orienting the crystals with their optical axes at a certain angle ${\ensuremath{\theta}}_{0}$ to the normal of the planar interfaces. The maximum angular range for the incident light to yield negative reflections depends on the refractive indices ${n}_{o}$ and ${n}_{e}$. Optical measurements on a $\mathrm{Y}\mathrm{V}{\mathrm{O}}_{4}$ crystal give good agreement with the theoretical prediction.

VECTOR CIRCUIT THEORY FOR SPATIALLY DISPERSIVE UNIAXIAL MAGNETO-DIELECTRIC SLABS

We present a general dyadic vector circuit formalism, applicable for uniaxial magneto-dielectric slabs, with strong spatial dispersion explicitly taken into account. This formalism extends the vector circuit theory, previously introduced only for isotropic and chiral slabs. Here we assume that the problem geometry imposes strong spatial dispersion only in the plane, parallel to the slab interfaces. The difference arising from taking into account spatial dispersion along the normal to the interface is briefly discussed. We derive general dyadic impedance and admittance matrices, and calculate corresponding transmission and reflection coefficients for arbitrary plane wave incidence. As a practical example, we consider a metamaterial slab built of conducting wires and split-ring resonators, and show that neglecting spatial dispersion and uniaxial nature in this structure leads to dramatic errors in calculation of transmission characteristics.

Analysis of diffraction from a uniaxial chiral slab with a two‐dimensional array of patches

AbstractDiffraction from a uniaxial chiral slab with a two‐dimensional periodic array of conducting patches is analyzed by the matrix‐based approach. Equatorial anisotropy is assumed for the chirality and permittivity whose optical axis is parallel to the plane of incidence. In the analysis, the total fields are given by the superposition of the current‐dependent scattering fields, which are expanded in terms of the two‐dimensional space harmonics and the incidence fields. The coupled mode equations for the equatorial uniaxial chiral media give the general solutions of fields as superpositions of elliptically polarized eigenmodes. The unknown currents on the patches are determined by applying the method of moments to the boundary conditions of the conducting array. In the numerical computations, the polarization characteristics of diffracted waves are investigated considering the design parameters. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(3): 1–8, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10293

Analysis of Diffraction from a Uniaxial Chiral Slab with a Two-Dimensional Array of Patches.

Diffraction from a uniaxial chiral slab with a two-dimensional periodic array of conducting patches is analyzed by the 4 × 4 matrix-based approach. Equitorial anisotropy is assumed for the chirality whose optical axis is parallel to the plane of incidence. In the analysis, the total fields are given by the superposition of the current-dependent scattered fields which are expanded in terms of the two-dimensional space harmonics and the primary fields. The coupled mode equations for the equitorial uniaxial chiral media give the general solutions of fields as the superposition of elliptically-polarized eigen modes. The unknown currents on the patches are determined by applying Moment method to the boundary condition of the conducting array. In the numerical computations, the polarization characteristics of diffracted waves are investigated considering the design parameters.

Artificial Uniaxial Bianisotropic Media at Oblique Incidence of Electromagnetic Waves

The response of uniaxial bianisotropic slabs to obliquely incident electromagnetic waves is studied, and the exact solution of this boundary-value problem is derived. This includes the calculation of all characteristics of reflected and transmitted waves. The study is relevant to recent experimental studies of arrays of parallel spirals. The present theory gives an analytical model of such artificial bianisotropic media.

Radiative transfer in a plane parallel slab of anisotropic uniaxial semi-transparent medium

The apparent emissivities emerging from an absorbing–emitting grey semi-transparent uniaxial crystal slab, and the temperature and radiative flux fields inside a crystal slab bounded by two black or transparent interfaces at radiative–conductive coupling have been determined with the help of a ray-tracing technique. The exact expressions of the temperature field and the radiative flux field for positive and negative uniaxial crystals have been obtained. Results display a strong influence of the crystal's positivity on the temperature and flux fields when the two boundary surfaces are transparent.

Uniqueness in a frequency-domain inverse problem of a stratified uniaxial bianisotropic medium

An inverse problem for a stratified uniaxial bianisotropic slab is considered in the frequency domain. The problem is treated as an analytic factorization problem in the frequency complex plane. Uniqueness in the parameter reconstruction is discussed and illustrated under a particular choice of a priori information.

Reply to comment on `Reflection and transmission by a uniaxial bi-anisotropic slab under normal incidence of plane waves

This is a reply to the preceding comment by Weiglhofer and Lakhtakia on `Reflection and transmission by a uniaxial bi-anisotropic slab under normal incidence of plane waves' (1998 J. Phys. D: Appl. Phys. 31 2458).

Comment on `Reflection and transmission by a uniaxial bi-anisotropic slab under normal incidence of plane waves

In the detailed numerical study reported in `Reflection and transmission by a uniaxial bi-anisotropic slab under normal incidence of plane waves' by Semchenko et al (1998 J. Phys. D: Appl. Phys. 31 2458), most of the presented results pertain to regions of the constitutive parameter space where, according to the Post constraint, physical materials do not have electromagnetically recognizable existence.

Plane wave propagation through a uniaxial chiral slab and transmission coefficient

Plane wave propagation through a uniaxial chiral slab and transmission coefficient

Plane wave propagation through a uniaxial chiral slab and transmission coefficient

Plane wave propagation through a uniaxial chiral slab and transmission coefficient