Study Of The Physical Properties Of Artificial Electromagnetic Metamaterials

We know that light is an electromagnetic wave,consisting of oscillating electric and magnetic fields.Consider light passing through a plate of glass.Because visible light has a wavelength that is hundreds of times larger than the atoms of which the glass is composed,the atomic details lose importance in describing how the glass interacts with light.In practice,we can average over the atomic scale,conceptually replacing the otherwise inhomogeneous medium by a homogeneous material characterized by just two macroscopic electromagnetic parameters:the electric permittivity,ε,and the magnetic permeability,μ.From the electromagnetic point of view,we have created an artificial material,or metamaterial.Metamaterials are artificial electromagnetic materials composed by subwavelength local resonance structures of electric and/or magnetic type.In the long wavelength limit,the effective permittivity and effective permeability can be used to describe the scattering properties of the structured objects based on the effective medium theory,metamaterials,owing their properties to subwavelength details of structure rather than to their chemical composition,can be designed to have properties difficult or impossible to find in nature.The range of available wave-functional materials has been broadened by recent developments in structured media,notably photonic band gap materials and metamaterials.These media have allowed the realization of solutions to Maxwell's equations not available in naturally occurring materials,fueling the discovery of new physical phenomena and the development of devices.Progress in the design of metamaterials has been impressive.In chapter 2 first we briefly present how to design the electric response materials with negative values of the permittivity,then we focus on discussion of the fabrications of magnetic response materials and negative refractive index materials,finally we introduce the method to determine the effective permittivity and permeability from reflection and transmission coefficients.In Chapter 3,we show that all these high-impedance surfaces,no matter how complex they appear,can be modeled by a double-layer system consisting of a homogeneous anisotropic meta-material layer(with a dispersive permeabilityμ) put on top of a metal sheet,and demonstrate its validity to describe both the reflective and surface wave properties of the realistic structures.In chapter 4,we propose a method to break the size restrictions imposed strictly on conventional cavities based on the reflection phase properties of metamaterial reflectors. For instance,we design a one-dimensional subwavelength cavity and two all-dimensional subwavelength cavities.The side of the one-dimensional cavity is only 1/12 of the working wavelength,especially,which can be used to achieve the directive emission.For the smallest all-dimensional cavity the we fabricated,each dimension is only a quarter of the resonance wavelength,we also perform experiments and simulations to demonstrate their subwavelength functionalities.In chapter 5 We establish a generalized 4×4 transfer-matrix method to study the scatterings of electromagnetic waves by anisotropic metamaterials.We will first study the wave propagations inside a single layer,and then set up a transfer matrix to connect the fields belonging to different layers,and finally derive the formulas to calculate the transmission and/or reflection coefficients.we employ the generalized 4×4 transfer-matrix method to study the electromagnetic wave scatterings by several types of anisotropic metamaterials In chapter 6,with attention mainly focused on the polarization manipulation effect.We will illustrate the ideas with three examples,namely,an anisotropic interface,a single anisotropic meta-material slab,and a double-plate metamaterial reflector.We show that the polarization states of electromagnetic waves can be manipulated availably through reflections by double-plate anisotropic metamaterial reflector,and all kinds of polarizations(circular, elliptic,and linear) realizable via adjusting material parameters.In particular,we show it is possible to rotate the polarization direction of a linearly polarized EM wave by an arbitrary angle using a planar reflector of thickness much less than wavelength.Microwave experiments and finite-difference-time-domain simulations on realistic structures are performed to successfully verify all theoretical predictions.