Invisibility Cloaks And Electromagnetic Wave Manipulating Devices Designed By Transformation Optics

Thanks to the development of the micro-manufacture technology, we could now fabricate many electromagnetic (EM) and optical functional microstructures, which own lots of novel physical properties and provide the basic support for explorations of new physics and also some practical applications. These artificial microstructures could be regarded as metamaterial with the model provided by the effective medium theory (EMT). Later on, a new concept "Transformation Optics (TO)" is proposed as a powerful tool for manipulation of the EM wave and light. According to the invariance of time invariant Maxwell’s equations under the space transformations, we could design "material" with coordinate transformations, and thus manipulate the EM wave and light to satisfy our demand of new functional devices. Lots of these new functional devices, such as invisibility cloak, invisibility carpet, beam shifter and beam concentrator have been proposed with the TO method.Based on such a background, this dissertation focuses on the proposal of new and practical EM and optical functional devices, which might find applications in the areas of invisibility cloaks, invisibility carpets, antennas, and new optical lens. The main context and contributions are listed below:1. We design the beam modulation devices under the Cartesian and cylindrical coordinates, and build the invisibility cloaks and invisibility carpets with these beam modulation blocks. The beam modulation device could modulate (compress or expand) the width of incident wave in the propagation direction, and manipulate the radiation directivity. We could also design invisibility cloaks and invisibility carpets with the beam modulation devices. We study the theoretical design of such an invisibility carpet and analyze the performance with the numerical tool based on finite element method. To facilitate the fabrication, we propose methods of the coarse dissections and the multilayer dielectric approximation, and finally construct a practical invisibility carpet with only several kinds of common dielectrics. The numerical simulation results indicate that the invisibility carpet could shield objects from detection with broad band effect, and non sensitive to incident wave.2. We propose and construct invisibility carpets with spatial invariant material parameters under a specially chosen transformation. For the infrared frequency band, we propose to fabricate a silicon grating structure as the invisibility carpet, embedded in the silicon waveguide on a SOI (Silicon on insulator) wafer. And for the microwave frequency band, we fabricate a quasi three dimensional structure as the invisibility carpet, which is constructed by the FR4dielectric board and air. The proposed invisibility carpet could protect the objects under metallic bump from the outside EM detection, which is validated by both the numerical and experimental results.3. We propose two methods for the optimization of nonmagnetic invisibility cloaks. First, we use a power function as the coordinate transformation, which ensures the matching of perpendicular wave impedance and thus minimizes the scattering cross section of the whole structure. And we also propose to use piecewise power functions to increase the flexibility of coordinate transformations and finally obtain a nearly perfect nonmagnetic cloak. Secondly, we optimize the nonmagnetic cloak composed of multilayer dielectrics with the genetic algorithm (GA), with minimized scatterings in the forward and backward directions.4. We also design several other EM devices, including one kind of horn antenna with high directivity, one method of transformation from conformal antenna array to linear array with easier design, one new self focusing lens with resolution beyond Abbe limit, as well as one practical realization idea of so-called omni directional EM wave concentrator, which could be fabricated with only one kind of common dielectric.5. We propose a multi-resonance Electromagnetic Bandgap (EBG) structure to mitigate the ground bounce noise in high speed circuits. Experimental results show that the structure could suppress the ground bounce noise from500MHz to5.5GHz, a rather broad "forbidden band". We also introduce the differential signal lines to improve the signal integrity, keeping the EBG structure as the power plane.