Affiliated with the
Communication & Space
Sciences Laboratory

Novel Electromagnetic Metamaterials

Chiral Metamaterials



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..: References :..

1-) BROADBAND EQUIVALENT CIRCUIT MODELS FOR CANONICAL CHIRAL ELEMENTS
by B. R. Long and D. H. Werner
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ABSTRACT: This article introduces broadband equivalent circuit models for both series-connected and parallel-connected canonical chiral elements. Each connection method results in a different terminal impedance behavior and therefore requires a different equivalent circuit model. These equivalent circuit models have a variety of applications including allowing for convenient analysis of chiral antennas as well as meta-materials composed of passively or actively loaded chiral elements.


2 -) Interaction of Electromagnetic Waves With 3-D Arbitrarily Shaped Homogeneous Chiral Targets in the Presence of a Lossy Half Space
by Xiande Wang, Douglas H. Werner, Le-Wei Li, Yeow-Beng Gan
IEEE Transactions on Antennas and Propagation, Vol. 55, No. 12, December 2007

ABSTRACT: The interaction of electromagnetic waves with an arbitrarily shaped three-dimensional (3-D) homogeneous chiral object located above a lossy half space is investigated using the method of moments (MoM) via the coupled mixed potential integral equations (MPIEs). Based on the surface equivalence principle, the equivalent surface electric and magnetic currents are used to replace the homogeneous chiral target in the presence of the half space. Two coupled MPIEs are developed for the unknown equivalent surface electric and magnetic currents by utilizing the continuity condition of the tangential total electric and magnetic field components on the chiral body’s surface. The well-known Galerkin procedure with Rao-Wilton-Glisson (RWG) basis functions is applied to solve this problem. The spatial domain half-space Green’s functions are obtained from the corresponding spectral domain Green’s functions via the discrete complex image method (DCIM) combined with the generalized-pencil of function (GPOF) technique. The reciprocity theorem is employed to calculate the far-zone scattered field. Numerical results are presented for characterizing electromagnetic scattering by a 3-D arbitrarily shaped homogenous chiral object located above a lossy half space so as to demonstrate the accuracy and efficiency of the proposed technique.




3 -) A Novel Dispersive FDTD Formulation for Modeling Transient Propagation in Chiral Metamaterials
Alkim Akyurtlu, and Douglas H. Werner,
IEEE Transactions on Antennas and Propagation, Vol. 52, No. 9, September 2004

ABSTRACT: Chiral media engineered for applications at microwave frequencies can be described as metamaterials composed of randomly oriented helices (with sizes typically less than a wavelength) embedded within an achiral background that is characterized by its permittivity and permeability. Chiral metamaterials embody properties of magnetoelectric coupling and polarization rotation. Chiral media are also highly dispersive and no effective full-wave time domain formulation has been available to simulate transient propagation through such an important class of metamaterials. A new finite-difference time-domain (FDTD) technique is introduced in this paper to model the interaction of an electromagnetic wave with isotropic dispersive chiral metamaterials, based on the implementation of a wavefield decomposition technique in conjunction with the piecewise-linear recursive convolution method. This formulation represents the first of its kind in the FDTD community. The FDTD model is validated by considering a one-dimensional example and comparing the simulations with available analytical results. Moreover, the FDTD technique is also used to investigate the propagation of electromagnetic waves through multilayered metamaterial slabs that include dispersive chiral and double-negative media. Hence, this model enables the investigation of complex dispersive metamaterials with magnetoelectric coupling and double-negative behavior as well as facilitates the exploitation of their unique properties for a variety of possible applications.




4 -) Optical planar chiral metamaterial designs for strong circular dichroism and polarization rotation
Do-Hoon Kwon, Pingjuan L. Werner, and Douglas H.Werner,
Optics Express, Vol. 16, Issue 16, pp. 11802-11807, July 23, 2008.

ABSTRACT: Planar chiral metamaterials comprising double-layer dielectricmetal- dielectric resonant structures in the shape of a gammadion are presented in the near-infrared regime. The unit cell of the doubly-periodic metamaterial design is optimized using the genetic algorithm for maximum circular dichroism and for maximum optical activity. A circular dichroism value in excess of 50% is predicted for the optimized design. Maximum polarization rotatory powers in terms of the minimum allowed transmittances are also obtained and presented.
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5 -) Material parameter retrieval procedure for general bi-isotropic metamaterials and its application to optical chiral negative-index metamaterial design
Do-Hoon Kwon, Douglas H. Werner, Alexander V. Kildishev, and Vladimir M. Shalaev
Optics Express, Vol. 16, Issue 16, pp. 11822-11829, July 23, 2008.

ABSTRACT: A chiral optical negative-index metamaterial design of doubly periodic construction for the near-infrared spectrum is presented. The chirality is realized by incorporating sub-wavelength planar silver-aluminasilver resonators and arranging them in a left-handed helical (i.e., stair-step) configuration as a wave propagates through the metamaterial. An effective material parameter retrieval procedure is developed for general bi-isotropic metamaterials. A numerical design example is presented and the retrieved effective material parameters exhibiting a negative index of refraction are provided.
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6-) An Active Metamaterial Platform for Chiral Responsive Optoelectronics
by L. Kang, S. Lan, Y. Cui, S. P. Rodrigues, Y. Liu, D. H. Werner, and W. Cai
Advanced Materials, Vol. 27, pp. 4377–4383, June 19 2015

ABSTRACT: Chiral-selective non-linear optics and optoelectronic signal generation are demonstrated in an electrically active photonic metamaterial. The metamaterial reveals significant chiroptical responses in both harmonic generation and the photon drag effect, correlated to the resonance behavior in the linear regime. The multifunctional chiral metamaterial with dual electrical and optical functionality enables transduction of chiroptical responses to electrical signals for integrated photonics.


7-) Handedness Dependent Electromagnetically Induced Transparency in Hybrid Chiral Metamaterials
by L. Kang, Z. H. Jiang, T. Yue, and D. H. Werner
Scientific Reports, Vol.5, pp.12224/1-11, July 2015.

ABSTRACT: We provide the first experimental demonstration of the handedness dependent electromagnetically induced transparency (EIT) in chiral metamaterials during the interaction with circularly polarized waves. The observed chiral-sensitive EIT phenomena arise from the coherent excitation of a nonradiative mode in the component split ring resonators (SRRs) produced by the corresponding Born−Kuhn type (radiative) resonators that are responsible for the pronounced chirality. The coherent coupling, which is dominated by the bonding and antibonding resonances of the Born−Kuhn type resonators, leads to an extremely steep dispersion for a circularly polarized wave of predefined handedness. Accordingly, retrieved effective medium parameters from simulated results further reveal a difference of 80 in the group indices for left- and right-handed circularly polarized waves at frequencies within the EIT window, which can potentially result in handedness-sensitive pulse delays. These chiral metamaterials which enable a handedness dependent EIT effect may provide more degrees of freedom for designing circular polarization based communication devices.


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