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Register a new userNon-left-handed transmission and bianisotropic effect in a [pi]-shaped metallic metamaterials
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A [pi]-shaped metallic metamaterial (geometrically, a combination medium of C-shaped resonators and continuous wires) is proposed to numerically investigate its transmission band near the resonant frequency, where otherwise it should be a negative-permeability (or negative-permittivity) stop band if either the C-shaped or continuous-wire constituent is separately considered. However, in contrast to the left-handed materials (LHMs)composed of split-ring resonators and wires as well as other metallic LHMs, this resonant transmission is a non-left-handed one as a result of the intrinsic bianisotropic effect attributed to the electrically asymmetric configuration of this [pi]-shaped metamaterial.
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Featuring dense spatial distributions of engineered metallic particles, electromagnetic metamaterials exhibit simultaneously negative values of both, dielectric permittivity and magnetic permeability, within a resonance frequency band called left-handed passband. Unusual electromagnetic properties are found resulting in promising applications such as sub-wavelength resolution imaging. State-of-the-art micro/nanomanufacturing has led to resonance frequencies reaching the visible red. The common embedding of the metal particles in plastic matrices or deposition on dielectric substrates within a small area severely limits the usefulness of the materials. Here, we use UV or X-ray lithography to build comparably large areas and quantities of the first freely-suspended matrix-free metamaterials in which the metallic structures are S-string-like with their ends held by a window-frame. In vacuo spectral characterization combined with simulation reveals left-handed passbands from 1.6 to 2.2 THz. Owing to their size, the devices can be easily handled. They offer a straightforward way of making them tunable and two-dimensionally isotropic.
Left-handed metamaterials make perfect lenses that image classical electromagnetic fields with significantly higher resolution than the diffraction limit. Here we consider the quantum physics of such devices. We show that the Casimir force of two conducting plates may turn from attraction to repulsion if a perfect lens is sandwiched between them. For optical left-handed metamaterials this repulsive force of the quantum vacuum may levitate ultra-thin mirrors.
Using detailed simulations we investigate the magnetic response of metamaterials consisting of pairs of parallel slabs or combinations of slabs with wires (including the fishnet design) as the length-scale of the structures is reduced from mm to nm. We observe the expected saturation of the magnetic resonance frequency when the structure length-scale goes to the sub-micron regime, as well as weakening of the effective permeability resonance and reduction of the spectral width of the negative permeability region. All these results are explained by using an equivalent resistor-inductor-capacitor (RLC) circuit model, taking into account the current-connected kinetic energy of the electrons inside the metallic parts through an equivalent inductance, added to the magnetic field inductance in the unit-cell. Using this model we derive simple optimization rules for achieving optical negative permeability metamaterials of improved performance. Finally, we analyze the magnetic response of the fishnet design and we explain its superior performance regarding the high attainable magnetic resonance frequency, as well as its inferior performance regarding the width of the negative permeability region.
We predict that two electron beams can develop an instability when passing through a slab of left-handed media (LHM). This instability, which is inherent only for LHM, originates from the backward Cherenkov radiation and results in a self-modulation of the beams and radiation of electromagnetic waves. These waves leave the sample via the rear surface of the slab (the beam injection plane) and form two shifted bright circles centered at the beams. A simulated spectrum of radiation has well-separated lines on top of a broad continuous spectrum, which indicates dynamical chaos in the system. The radiation intensity and its spectrum can be controlled either by the beams current or by the distance between the two beams.
In the present work, we explore soliton and rogue-like wave solutions in the transmission line analogue of a nonlinear left-handed metamaterial. The nonlinearity is expressed through a voltagedependent and symmetric capacitance motivated by the recently developed ferroelectric barium strontium titanate (BST) thin film capacitor designs. We develop both the corresponding nonlinear dynamical lattice, as well as its reduction via a multiple scales expansion to a nonlinear Schrodinger (NLS) model for the envelope of a given carrier wave. The reduced model can feature either a focusing or a defocusing nonlinearity depending on the frequency (wavenumber) of the carrier. We then consider the robustness of different types of solitary waves of the reduced model within the original nonlinear left-handed medium. We find that both bright and dark solitons persist in a suitable parametric regime, where the reduction to the NLS is valid. Additionally, for suitable initial conditions, we observe a rogue wave type of behavior, that differs significantly from the classic Peregrine rogue wave evolution, including most notably the breakup of a single Peregrine-like pattern into solutions with multiple wave peaks. Finally, we touch upon the behavior of generalized members of the family of the Peregrine solitons, namely Akhmediev breathers and Kuznetsov-Ma solitons, and explore how these evolve in the left-handed transmission line.
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