Applications Of Layered Structures: Transformed Media Devices And1D Tunable Microwave Photonic Crystals

Electromagnetic matematerials (MTMs) science has become a new subdiscipline within physics(especially electromagnetism and materials science). It is broadly defined as artificial effectivelyhomogeneous electromagnetic structures with unusual properties not readily available in nature,such as left-handed material (LHM), electromagnetic band gap (EBG) structure, artificial magneticconductor (AMC),ect.. Since2006, transformation optics has aroused a lot scientific interests for itsunprecedented flexibility in manipulating electromagnetic waves propagation, which also has beena powerful tool in designing of MTMs.In this dissertation, we study the electromagnetic properties of layered isotropic materialstructures. In fact, the size of an effectively homogeneous structure cell of matter is the key point ofits behavior. In sub-wavelength scale, that is to say that the cell size is much smaller than theguided wavelength (at lest smaller than a quarter of wavelength), layered isotropic materialstructures behave a single isotropic material based on the effective medium theory. However, thecell size is in the scale of wavelength, the electromagnetic properties should be determined bydiffraction and interference, such as the phenomenon electromagnetic band gap. Therefore, in ourfirst work, we have mapped the parameters of the layered isotropic structures in sub-wavelengthscale into the desired parameters of transformation media devices. In another work, we applieddispersive media to the constituents of periodical cell of the microwave photonic crystal andinvestigated the electromagnetic properties by the tunable factors of the composing dispersivematerials. The main innovations of this dissertation could be summarized as:1. First of all, we investigated the arbitrary polygonal plane ground cloaks. The ideal parametersof the curved structural plane ground cloak could be obtained based on the theory coordinatetransformation and the invariance of Maxwell’s equations. In order to obtain the parameters ofthe cloak with invariance in real space, the curved structural plane ground cloak could besimplified as polygonal carpet cloak, which is composed of several blocks and each block hasinvariable anisotropic parameters. Based on the theory of effective medium, parallel layeredisotropic structure could mimic the parameters desired by polygonal carpet cloaks. Furthermore,we combined and optimized the parameters for TE and TM waves to realize the invisibility forhybrid incoming detective wave.2. In second, we investigated three microwave illusion devices. We firstly applied concentric layered isotropic material structures to mimic the cylindrical anisotropic shrinking device,which can make any object enclosed smaller than its real size. Considering the inverse problemof the shrinking device, we proposed an amplifying device, which can make an object locatedin its core region larger than its real size. Then we utilize radially symmetrical layeredstructures to imitate the performance of the amplifying device. At last, we presented ashortening device and lengthening device in one-dimensional space. Such illusion devices canbe realized by a pair of perpendicular grating structures.3. Thirdly, we investigated controlling of the electromagnetic scattering of a cavity or troughlocated under an infinite perfect electrical conducting (PEC) plane. By filling the cavity withproperly designed transformation medium, the scattering of the cavity can be modulated intospecular direction, which can effectively reduce the radar section cross of the cavity. As theinverse problem, we also design a transformation coating for a standard PEC pane to mimic thescattering of an empty cavity, which can lead the detector make a mistake. The real and virtualcavity could be simplified as polygonal shape and their parameters also can be realized by theparallel layered isotropic structure. In the following, we designed a v-shaped camouflage cloak,which can camouflage an arbitrary object by mimicking electromagnetic scattering of an emptyv-shaped cavity under a PEC plane ground.4. At last, we analyzed the properties of two kinds of microwave photonic crystals by FDTDmethods. We firstly induced and proposed three kinds of FDTD approaches for differentdispersive materials, including unmagnetized plasma, superconductor and biological tissues. Inthe following, we presented a tunable narrowband filter which can be formed when a plasmadefect is introduced in one-dimensional dielectric-air microwave photonic crystal and itstunable narrow-pass band is calculated by PLJERC-FDTD method. At last, based on SO-FDTDmethod, we have calculated the low-frequency stop band of the superconductor-dielectricsuperlattice, which can be tuned by adjusting the temperature, London penetration depth ofsuperconductor constituent.