Hai-Ying Yao

Bio: Hai-Ying Yao is an academic researcher from National University of Singapore. The author has contributed to research in topics: Metamaterial & Negative refraction. The author has an hindex of 11, co-authored 20 publications receiving 340 citations.

Backward waves in magnetoelectrically chiral media: Propagation, impedance, and negative refraction

Abstract: Magnetoelectrically chiral media are studied in this paper as potential materials to realize double negative materials and negative refractive characteristics. The behaviors of the negative refractive index, the backward eigenwaves, and the impedance of these eigenmodes of this particular type of chiral media are examined in detail. We consider longitudinal and transverse propagation separately. Among the wave numbers obtained, we find that two of them are backward propagating waves in certain frequency bands. The helicity and polarization states are shown. We further study the impedance of these backward eigenmodes, which have potential applications in impedance matching, subwavelength resonator cavities and high-directivity antennas. Due to the off-diagonal gyrotropic parameters, a negative refractive index can be achieved when the material parameters and frequency are properly chosen. A study of the zero index of refraction for magnetoelectrically chiral media is carried out, and potential applications are proposed.

Routes to left-handed materials by magnetoelectric couplings

Abstract: Magnetoelectric materials, which couple electric fields with magnetic fields, are intensively studied for physical realization and potential synthesis of left-handed materials (LHM). Both isotropic and anisotropic magnetoelectric materials are the realization of backward waves and/or negative refraction within certain frequency bands. Since the magnetoelectric coupling (scalar or tensorial) parameters may significantly reduce the refractive indices and even cause the anisotropic nihility, left-handed materials can be realized without requiring the resonances of the permittivity and permeability. Wave-field theorem is thus applied to obtain the effective parameters in their equivalent isotropic counterparts, and dispersion models associated with mixing rules are considered as an alternative important factor to achieve LHM.

Left-handed material effects on waves modes and resonant frequencies: filled waveguide structures and substrate-loaded patch antennas

Abstract: In this paper, we apply the Double Negative Material in some basic applications, including waveguide, rectangular patch antenna and disc patch antenna. By analyzing theoretically we find that the sizes of these equipments can be greatly reduced by using multi-block (which may include both double positive and double negative material) dielectric materials. In addition, the sizes of patch antennas are no longer proportional to the working frequency but roughly to the ratio of the thicknesses of dielectric slabs. Still some new modes in both waveguide and patch antennas are found, and by working at the new modes the bandwidth of the patch antenna can be dramatically increased.

Extraction of Constitutive Relation Tensor Parameters of SRR Structures using Transmission Line Theory

Abstract: In this paper, the transmission line theory is utilized to characterize the metamaterials comprising of microscopic elements of a periodic array, specifically, the traditional split-ring resonators (SRRs), as an example. The bianisotropic property of the metamaterials is characterized in a new way different from the existing wave methods. As evident from both simulations and experiments, the SRR array structure is found to be quite lossy even though it is made of very good conductor or even perfect conductor as in simulation. With the present characterization, we are able to explain physically very well on how or why the energy gets lost in this structure. Finally, the theoretical result is compared with numerical simulation data obtained based on quasi-static Lorentz theory to further verify our analysis.

On the constitutive relations of G-chiral media and the possibility to realize negative-index media

Abstract: Gyro-chiral (G-chiral) media of different constitutive relations are studied as potential materials to realize the negative-index material (NIM). G-chiral media are believed to have advantages over chiral media: negative refractive index and backward waves can be achieved without requiring the permittivity and permeability to be quite small at working frequency. The gyrotropic parameters favor the realization of NIM far off the resonances of the permittivity and permeability. The possibility of obtaining backward waves and negative refractive index under Post's and Tellegen's relations are discussed. Moreover, the mapping and comparison of G-chiral media of these two relations have been studied. It is found that the Tellegen's relations are more suitable to describing the G-chiral media so as to realize NIM by this kind of medium. Therefore, this paper not only provides an alternative way to achieve NIM from the G-chiral medium but also discusses the constitutive relation's effects on backward wave propagation and refractive indices. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:2534–2538, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21981

Magnetoelectric and multiferroic media

Abstract: The last decade has witnessed a significant growth of research into materials with coupled magnetic and electric properties. Reviewed here are the main types and mechanisms of magnetoelectric interactions and conditions of their origin. Special attention is given to potentially practical materials that display magnetoelectric properties at room temperature. Example applications of magnetoelectric materials and multiferroics in information and energy saving technologies are discussed.

Chiral metamaterials: simulations and experiments

Abstract: Electromagnetic metamaterials are composed of periodically arranged artificial structures. They show peculiar properties, such as negative refraction and super-lensing, which are not seen in natural materials. The conventional metamaterials require both negativeand negative μ to achieve negative refraction. Chiral metamaterial is a new class of metamaterials offering a simpler route to negative refraction. In this paper, we briefly review the history of metamaterials and the developments on chiral metamaterials. We study the wave propagation properties in chiral metamaterials and show that negative refraction can be realized in chiral metamaterials with a strong chirality, with neithernor μ negative required. We have developed a retrieval procedure, adopting a uniaxial bi-isotropic model to calculate the effective parameters such as n±, κ, � and μ of the chiral metamaterials. Our work on the design, numerical calculations and experimental measurements of chiral metamaterials is introduced. Strong chiral behaviors such as optical activity and circular dichroism are observed and negative refraction is obtained for circularly polarized waves in these chiral metamaterials. We show that 3D isotropic chiral metamaterials can eventually be realized.

Chiral metamaterials: simulations and experiments

Abstract: Electromagnetic metamaterials are composed of periodically arranged artificial structures. They show peculiar properties, such as negative refraction and super-lensing, which are not seen in natural materials. The conventional metamaterials require both negative ∈ and negative μ to achieve negative refraction. Chiral metamaterial is a new class of metamaterials offering a simpler route to negative refraction. In this paper, we briefly review the history of metamaterials and the developments on chiral metamaterials. We study the wave propagation properties in chiral metamaterials and show that negative refraction can be realized in chiral metamaterials with a strong chirality, with neither ∈ nor μ negative required. We have developed a retrieval procedure, adopting a uniaxial bi-isotropic model to calculate the effective parameters such as n ± , K, ∈ and μ of the chiral metamaterials. Our work on the design, numerical calculations and experimental measurements of chiral metamaterials is introduced. Strong chiral behaviors such as optical activity and circular dichroism are observed and negative refraction is obtained for circularly polarized waves in these chiral metamaterials. We show that 3D isotropic chiral metamaterials can eventually be realized.

Variable metamaterial apparatus

Abstract: Artificial materials, such as metamaterials, include adjustable properties. In some approaches the properties are adjustable according to active feedback of interaction with electromagnetic waves.

A broadband and high-gain metamaterial microstrip antenna

Abstract: A broad bandwidth and high gain rectangular patch antenna was specifically designed in this paper using planar-patterned metamaterial concepts. Based on an ordinary patch antenna, the antenna has isolated triangle gaps and crossed strip-line gaps etched on the metal patch and ground plane, respectively. Demonstrated to have left-handed characteristics, the patterned metal patch and finite ground plane form a coupled capacitive-inductive circuit of negative index metamaterial. It is shown to have great impact on the antenna performance enhancement in terms of the bandwidth significantly broadened from a few hundred megahertz to a few gigahertz, and also in terms of high efficiency, low loss, and low voltage standing wave ratio. Experimental data show a reasonably good agreement between the simulation and measured results. This antenna has strong radiation in the horizontal direction for some specific applications within the entire band.