DNG Materials Research Articles

Computing Photonic Bandgap from Dispersion Relation for TM Mode Propagation Inside Metamaterial-Based 1D PhC

Aim: Calculation of dispersion profile and photonic bandgap for negative refractive index based onedimensional photonic crystal structure. Objective: Determine mathematically the variation of first and second photonic bandgaps under angular incidence variation for the metamaterial-based 1D PhC structure for both TE and TM mode of propagations. Methods: Two lowermost photonic bandgap widths of metamaterial-based one-dimensional photonic crystal are analytically computed from the dispersion relation under the propagation of transverse electromagnetic wave along the direction of confinement. Three practically realizable double negative index materials are considered for computation of bandgaps, where air-gaps are considered along with the artificially made materials as the composite grating structure. This is a combination of negative positive indices materials, where incident angles are tailored within practical limit to calculate the variation of bandgaps, which may be quasi or complete depending on the material composition and angle of incidence. Results: Results are compared with that obtained for TE mode propagation, and are highly important for design of the all-optical filter with DNG materials.

Optimization of multilayer cylindrical cloaks using genetic algorithms and NEWUOA

The problem of minimizing the scattering from a multilayer cylindrical cloak is studied. Both TM and TE polarizations are considered. A two-stage optimization procedure using genetic algorithms and NEWUOA (new unconstrained optimization algorithm) is adopted for realizing the cloak using homogeneous isotropic layers. The layers are arranged such that they follow a repeated pattern of alternating DPS and DNG materials. The results show that a good level of invisibility can be realized using a reasonable number of layers. Maintaining the cloak performance over a finite range of frequencies without sacrificing the level of invisibility is achieved.

Effects of loss factors on zero permeability and zero permittivity gaps in 1D photonic crystal containing DNG materials

The effects of electric and magnetic loss factors on zero-= and zero-= gaps in a one-dimensional lossy photonic crystal composed of double-negative and double-positive materials are theoretically investigated by employing the characteristic matrix method. This study contradicts the previous reports as it indicates that by applying the inevitable factors of electric and magnetic losses to the double-negative material, the zero-= and zero-= gaps appear simultaneously in the transmission spectrum, being independent of the incidence angle and polarizations. Moreover, the results show that these gaps appear not only for an oblique incidence but also in the case of normal incidence, and their appearance at the normal incidence is directly related to the magnetic and electric loss factors. Besides, the results indicate that as the loss factors and angle of incidence increase, the width of both gaps also increases.

A new material classification of lossy metamaterials

The propagation constant is extended and derived for lossy metamaterials in which e 0 (ENG), e > 0 and μ < 0 (MNG), and e < 0 and μ < 0 (DNG).Regardless of the magnitudes of e and μ, DPS materials are a RH medium and DNG materials are a LH medium. However, SNG materials become a RH medium when the sign of (e × μ + e × μ) is positive and a LH medium when the sign is negative. A new diagram is proposed to classify any lossy metamaterial into either RH or LH medium. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:445–447, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25687

Three-dimensional double-negative metamaterials resonating at 13.5 GHz

A three-dimensional double-negative (DNG, epsiv < 0, mu < 0) metamaterial has been designed to operate near 13.5 GHz. The metamaterial was comprised of patterned copper split ring resonators (SRRs) and wires on a Rogers 5880 substrate. The SRRs and wires were each constructed in three orthogonal planes to give a near-isotropic response to an arbitrarily polarised EM excitation. As this material responds to radiation of arbitrary polarisation and direction, it is referred to as a 3E3H structure where all the six components of the EM tensor are present. The simulated losses in the unit cell are large (2 dB/cm), a major contribution being ohmic effects in the SRRs. For many applications, unit cells of lower dimensionality, that is, 2E2H or 1E1H, where only a restricted number of the elements of the EM tensor are needed, can perform nearly as well as 3D DNG materials, but with much lower loss, and thus may be preferred as an alternative to an isotropic 3E3H structure.

Fractional duality and metamaterials with negative permittivity and permeability

Fractional dual solutions for the source free Maxwell’s equations are determined for material with negative permittivity and permeability (DNG material). The fractional dual solutions for DNG materials are compared with the corresponding solutions for materials with positive permittivity and permeability (DPS material).