New Artificial Electromagnetic Medium Of Transmission And Coupling Mechanism

As we know everything in the world were made of atoms. In principle there's no such homogeneous medium in world even the vacuum. But we still consider lots of things as a homogeneous medium. For example we consider water as a homogeneous so that we employed Bernoulli equations in such system to study how the force acts on a ship in water. We consider a glass as a homogeneous medium to study how the light passes through it, to calculate the value of reflectivity. The reason we can do so is that the scale that we consider about, in electromagnetic system is the wavelength in such medium, is hundreds times larger than the scale of atoms of system composed, so that the detail of atoms structure is neglectable, only consider of properties of system behavior in global scale.Certainly sometimes we must consider the differences of things at some places between other places even atoms are very small. For example, the second harmonic coefficient in side a metal (bulk) is vanishing for every point we consider of in side the metal has inversion symmetry. How ever things changed if we look at the surface of a metal, because there's no inversion symmetry at such region. This is because the symmetry is a very important properties of syslem that we can not treat it easily by average it or neglect it. Here we must point out is that the magnetism of Split-Ring Resonator (SRR) is due the geometric symmetry broken by a split. So it can exhibition in large scale.If we amplify the concept of atom. consider microstructures as artificial atoms, than we can manufacture any materials possess any properties we needed as god did. Certainly here the "any" should be restricted by the order of nature. Metamaterial is such an artificial material to extend the electromagnetic properties in nature. Based on conception of effective medium, progress in study or design of metamaterials has been impressive. In chapter 1, first we look back the history of metamaterials briefly, than we will show you some typical progresses we have on it.In chapter 2, we show that a metallic waveguide behaves as an electric (magnetic) plasma for transverse-electric (transverse-magnetic) polarized electromagnetic (EM) waves at frequencies below cut-off value. Inserting anisotropic resonance structures of either electric or magnetic type into a waveguide, we find extraordinary transmissions of EM waves with different polarizations through the waveguide at frequencies well below the waveguide's cut-off value, following two different mechanisms. Microwave experiments, in excellent agreements with finite-difference-time-domain simulations, are performed to successfully demonstrate all theoretical predictions.In chapter 3, we established a generalized tight-binding method (TBM) to study the coupling effects in metamaterials. All parameters involved in our theory can be calculated from first principles, and the theory is applicable to general photonic systems with both dielectric and magnetic materials. As the illustration, we applied the theory to study cutoff waveguides loaded with resonant electric/magnetic metamaterials. We not only accurately computed the coupling strengths between two resonant metamaterials, but also revealed a number of interesting coupling-induced phenomena. Microwave experiments and full-wave numerical simulations were performed to successfully verify all predictions drawn from the TBM.Finally I will give a conclusion in chapter 4.