Kuang Zhang

Material parameters characterization for arbitrary N-sided regular polygonal invisible cloak

Arbitrary N-sided regular polygonal cylindrical cloaks are proposed and designed based on the coordinate transformation theory. First, the general expressions of constitutive tensors of the N-sided regular polygonal cylindrical cloaks are derived, then there are some full-wave simulations of the cloaks that are composed of inhomogeneous and anisotropic metamaterials, which will bend incoming electromagnetic waves and guide them to propagate around the inner region; such electromagnetic waves will return to their original propagation directions without distorting the waves outside the polygonal cloak. The results of full-wave simulations validate the general expressions of constitutive tensors of the N-sided regular polygonal cylindrical cloaks we derived.

Arbitrary waveguide connector based on embedded optical transformation

Arbitrary connector for waveguides of different cross sections is proposed and designed theoretically based on the embedded optical transformation theory. First, the general expressions of constitutive tensors of the metamaterials filled in the connector are derived. Second, there are some full-wave simulations that validate the constitutive tensors derived. The results show that the connector with metamaterials inclusions with designed constitutive parameters can fulfill the reflectionless transmission of electromagnetic waves between waveguides of different cross sections. Finally, connectors of several forms are investigated parametrically, and two sets of constitutive tensors that can be physically achieved by existing metamaterials are gotten. It is believed that this study provides a feasible way to fulfill the efficient transmission of electromagnetic waves between waveguides of different cross sections.

Metamaterial analogue of electromagnetically induced transparency in two orthogonal directions

We demonstrate theoretically that the analogue of electromagnetically induced transparency (EIT) in two orthogonal directions can be achieved in a planar metamaterial consisting of spiral resonators and split ring resonators in the same plane. The metamaterial can exhibit EIT-like effect to both normally and laterally incident electromagnetic waves because of its electric and magnetic response, respectively. Full-wave numerical simulations are carried out to validate the EIT-like effect of the planar metamaterial. Absorption curves, transmission spectra, surface current distributions and effective constitutive parameters of the metamaterial illuminated by normally and laterally incident EM waves are presented. These results, showing a transparency window with extremely low absorption and strong dispersion, are in good agreement with each other.

Magnetic metamaterial analog of electromagnetically induced transparency and absorption

In this paper, it is theoretically demonstrated that the electromagnetically induced transparency (EIT) and absorption (EIA) can be achieved in a magnetic metamaterial. Unit cell of metamaterial consists of a split ring resonator and an “I” shaped cut-wire pair, which serves as a bright resonator and a dark resonator, respectively. It is found that the EIT effect in metamaterial results from the magnetic interaction between bright and dark resonators. A classical model is also introduced to describe the EIT behavior in magnetic metamaterial, and its analytical results are in good agreement with numerical results. Significantly, by controlling the space separation between resonators, we can obtain the destructive and constructive interferences, and thus observe the transition between EIT and EIA. These results may achieve potential applications on enhancing the nonlinear interaction.

Low-Loss Magnetic Metamaterial Based on Analog of Electromagnetically Induced Transparency

In this paper, a low-loss magnetic metamaterial configuration consisting of coupled radiative and dark resonators is proposed based on analog of electromagnetically induced transparency. Full-wave numerical simulations are carried out to validate the metamaterial. Absorptions curves, transmission spectrums, surface current distributions, and effective constitutive parameters for the metamaterial are presented. These results, showing a low-loss transparency window and strong dispersion in the effective permeability with negative values, are in a good agreement with each other.

Metamaterials With Tunable Negative Permeability Based on Mie Resonance

Metamaterials with tunable negative permeability are proposed and investigated theoretically in this paper. First, the model of the dielectric bilayer sphere embedded in the dielectric substrate is put forward. Second, expressions of the electromagnetic fields in the model are derived based on the Mie scattering theory, and the general formula for the effective permeability of the model is deduced via the Maxwell-Garnett theory, which is further verified through the simulation results. Finally, the tunable bandwidth of the negative permeability of the metamaterials changing with the geometrical parameters is investigated based on the full-wave simulations, and the relative mechanisms are also discussed. It is believed that the results would be helpful for the practical applications of the metamaterials, and the metamaterials with tunable negative permeability proposed in the paper would facilitate the constructions of the left-handed materials in some degree.

Waveguide connector constructed by normal layered dielectric materials based on embedded optical transformation

Based on embedded optical transformation, a connector for waveguides of the same size and different positions is proposed, fabricated and tested. Compared with previous work on reflectionless waveguide bends or tapers with minimized distortions, the connector proposed in this paper can be constructed with normal homogeneous and isotropic dielectric materials with layered structure, and the results of both the full-wave simulations and the experiments validate the design. It is believed that this study provides a feasible way to fulfill the proper transmission of electromagnetic waves between waveguides of different positions.

Total transmission and total reflection of electromagnetic waves by anisotropic epsilon-near-zero metamaterials embedded with dielectric defects

In this paper, the transmission of the electromagnetic waves in the waveguide filled with the anisotropic epsilon-near-zero (ENZ) metamaterials with dielectric cylindrical defects embedded is investigated. The anisotropy is taken into consideration, and the sandwich structure is put forward to achieve total transmission and total reflection. Despite of the anisotropy and the impedance mismatch compared with the matched impedance zero-index metamaterials, both the analytical and the numerical results show that the total reflection and the total transmission can be achieved. Furthermore, some factors that own potential effects on the transmission of the electromagnetic waves are also discussed, and it is interesting to find that the radius of the embedded dielectric cylindrical defect could greatly affect the bandwidth of total transmission and total reflection. By removing the dependence on isotropy and impedance matching, our work can facilitate the applications of the ENZ metamaterials in the waveguide.

Design, Fabrication, and Testing of Three-Dimensional Miniaturized Rectangular Cavity Resonator Based on Metamaterial

In this paper, we have demonstrated that a three-dimensional (3-D) miniaturized rectangular cavity resonator (MRCR) with simultaneously shorten electric length and electric width can be designed, fabricated and tested through extending the analysis of the metamaterial-based cavity resonator to the 3-D case. Resonance equation solutions of a rectangular cavity resonator filled with anisotropic metamaterials bilayer are explored. Results show that the resonance frequency of such a cavity resonator can be simultaneously independent on the cavity width and length when the transversal components of the permeability tensors of the filled metamaterials have opposite sign. Based on the results, a 3-D MRCR is designed, fabricated, and tested by using modified SRRs with negative transversal permeability. It is shown that the electrical length and width of the designed 3-D MRCR are simultaneously reduced to 0.2 much smaller than 0.5, which is the theoretical minimum of the electric length and width of a conventional rectangular cavity resonator.

Polarization conversion of electromagnetic waves by Faraday chiral media

The reflection of a normally incident plane wave due to the interface between vacuum and a Faradaychiral medium (FCM) supported by a perfect electric conductor was rigorously derived. Numerical results strongly indicated that arbitrary polarization conversions are realizable from the incident plane wave to the reflected plane wave by properly choosing the constitutive parameters of the FCM.