Waveguide containing a backward-wave slab

We have considered theoretically the waveguide properties of a plane two-layered waveguide, whose one layer is a usual magnetodielectric (forward-wave medium), but another one is a slab of so-called backward-wave material (BW-material), whose both permittivity and permeability are negative. We have analyzed the properties of eigenwaves in this waveguide. In particular, it was found that there exist waves of both TE and TM polarizations, whose fields decay exponentially from the interface of the two slabs inside both layers, and their slow-wave factor tends to infinity at small frequencies. Thus, this waveguiding system supports super-slow waves with extremely short wavelengthes, as compared to the free-space wavelength and the cross section size. Other peculiarities of the spectrum are also discussed

Three-dimensional negative index of refraction at optical frequencies by coupling plasmonic waveguides

We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. By properly controlling coupling between adjacent waveguides, a metamaterial consisting of a one-dimensional multilayer stack exhibiting an isotropic index of -1 can be achieved at a free-space wavelength of 400 nm. The general concepts developed here may inspire new low-loss metamaterial designs operating close to the metal plasma frequency.Comment: 8 pages, 7 figure

Left-Handed Surface Waves in a Photonic Structure

It is demonstrated that an isotropic left-handed medium can be constructed as a photonic structure consisting of two dielectric materials, one with positive and another with negative dielectric permittivities epsilon. Electromagnetic waves supported by this structure are the surface waves localized at the dielectric interfaces. These surface waves can be either surface phonons or surface plasmons. Two examples of negative epsilon materials are used: silicon carbide and free-electron gas.Comment: 7 pages, two figure

Comparative Analysis of Guided Modal Properties of Double-Positive and Double-Negative Metamaterial Slab Waveguides

The guided modal properties of double-positive and double-negative metamaterial slab waveguides are numerically analyzed and compared when varying the dielectric and magnetic constants. As the cutoff frequencies of both slab waveguides remained unchanged when the absolute value of the refractive index was kept invariant, this enabled an effective comparison of the respective guided modes. Thus, the guided mode dispersion characteristics of the double-positive and double-negative slab waveguides were analyzed and compared, including several higher order modes. As a result, this comparative analysis provides greater physical insights and a better understanding of the guided modal characteristics of double-negative metamaterial slab waveguides

Guided Modes in a Waveguide Filled With a Pair of Single-Negative (SNG), Double-Negative (DNG), and/or Double-Positive (DPS) Layers

Here we present the results of our theoretical analysis for guided modes in parallel-plate waveguides filled with pairs of parallel layers made of any two of the following materials: 1) a material with negative real permittivity, but positive real permeability (epsilon-negative); 2) a material with negative real permeability, but positive real permittivity (mu-negative); 3) a material with both negative real permittivity and permeability (double-negative); and 4) a conventional material with both positive real permittivity and permeability (double-positive) in a given range of frequency. Salient properties of these guided modes are studied in terms of how these materials and their parameters are chosen to be paired, and are then compared and contrasted with those of the guided modes in conventional waveguides. Special features such as monomodality in thick waveguides and presence of TE modes with no-cutoff thickness in thin parallel-plate waveguides are highlighted and discussed. Physical insights and intuitive justifications for the mathematical findings are also presented

Rectangular Waveguide Filled with Uniaxial Medium and Negative Resistance Enhanced Composite Right/Left-Handed Transmission Line

Two wave-guiding problems are treated in this work. The first part addresses the problem of a rectangular waveguide filled with a uniaxially anisotropic or uniaxial medium. Different orientations of the optic axis of the uniaxial medium are considered and the wave transmission and modal behaviors are investigated. When the optic axis is aligned with one of the coordinate axes, i. e., x, y, or z axis, the method of wave decomposition with respect to the optic axis orientation is proposed and the complete analytic solutions are presented and compared with conventional transverse-to-z solutions. When the optic axis is tilted but lying in one of the side wall planes, TE0n or TEm0 (transverse to z) modes are shown to be supported. Furthermore, the supported hybrid wave modes in these cases are numerically found from calculations using the proposed boundary condition matrix (BCM) method. Different from the conventional spectral domain calculation methods, the numerically found hybrid wave modes are expressed as a linear combination of ordinary and extraordinary waves. The algorithm is illustrated and numerical examples are given. The validity of the solution is verified by comparing its results with those of the aligned cases that are analytically solved. The second wave-guiding structure is focused on a type of metamaterial realization. Analyses and experimental results of the negative resistance enhanced composite right/left-handed (NR-CRLH) transmission line are presented. As a demonstration of its unique amplitude and phase behaviors and its application, the detailed analysis of the structure is followed by an example of high-directivity leaky-wave antenna (LWA). In contrast to the conventional CRLH unit cell with via terminated stubs, the NR-CRLH unit cell is designed with negative-resistance (NR) terminated stub that compensates the power loss from the orthogonal direction with respect to the direction of guided-wave propagation. The NR is realized using the inverted common collector (ICC) configuration of an RF transistor, a common commercial product often seen for RF amplifier and oscillator applications. This implementation topology allows the active unit cell (AUC) to preserve all the CRLH properties including the unique dispersion relations, constant Bloch impedance in a broad operating frequency range, and bilateral operation. To highlight the advantages of the active metamaterial transmission line (TL), the NR-CRLH TL based LWA that permits the manipulation of the current distributions over the antenna surface is demonstrated. The NR-CRLH based active antenna allows the control of radiation performances including the patterns, beamwidth, and directivity. The measured results of the LWA prototype demonstrate enhanced directivity compared to the conventional CRLH LWA of the same lengths while minimally influencing all the preferable characteristics of full frequency scanning LWA