Optical Properties Of Manipulable Magnetic Metamaterials And The Design Of Electromagnetic Devices

With the rapid development of information technology and the advent of various artificial materials, metamaterials composed of diverse resonant building blocks have been proposed since the1960s, based on which the electromagnetic (EM) wave prop-agation can be controlled flexibly. Most importantly, metamaterials enable a lot of in-triguing and exotic EM properties not found in nature, as well as potential applications in military, communication, healthcare, energy and so on. The commercial values can also be expected. In addition, metamaterials play a crucial role on the development of electromagnetics and the relevant fields. Therefore, the investigation on metamaterials from both the theoretical and experimental points of view is of great significance.This thesis is devoted to examine the EM characteristics of metamaterials made of Mg-Mn and single crystal yttrium iron garnet (YIG) ferrite rods, respectively. Mean-while, some practical EM devices are also designed based on the novel properties. The framework and the results are as follows:In chapter one, we present a brief introduction on photonic crystals and metama-terials, including the history, EM characteristics and some possible applications.In chapter two, we present several theoretical methods which are constantly em-ployed to calculate the photonic band structure. However, these methods are not effi-cient and reliable in examining magnetic metamaterials (MMs) due to the complexity of MMs. Thereby the multiple scattering theory and the extended Mie theory are intro-duced to deal with the MM systems. In addition, MMs can be regarded as homogenous media with effective permittivity and effective magnetic permeability. Hence, we have also presented an effective-medium theory which is specially suitable to retrieve the effective constitutive parameters of MMs. With the approaches presented, we can per-form the calculations and simulations shown in the following chapters.In chapter three, by calculating the photonic band diagrams and the transmittance we investigate the optical properties of the magnetic surface plasmon (MSP) resonance in MMs consisting of Mg-Mn ferrite rods. Interestingly, the calculated results show that the MSP-based photonic band gap (PBG) can not only be manipulated by adjusting the external magnetic field (EMF), but also be robust against the perturbation of the ferrite rods. However, the bragg scattering induced PBG is inert to the EMF, and also susceptible to structured disorders. Accordingly, an optical switch with fast response is designed based on the features of the MSP resonance. Furthermore, by examining both the effective constitutive parameters retrieved and the transmittance calculated as the functions of the EMF, the designed switch are optimized so that it can realize the best switching effect.In chapter four, we demonstrate a new method to excite the unidirectional EM mode at the interface of MMs made up of single crystal YIG ferrite rods. Through calculating the photonic band diagrams and the transmittance, we find that a wide fre-quency range, within a PBG resulting from the MSP resonance, can support such non-reciprocal EM mode. We also simulate the electric field patterns for the cases when position disorder and size fluctuation are introduced in different layers of the MM slab, which suggest the excitation of the unidirectional EM mode mainly depends on the coupling of the EM energy to the first layer rods. In particular, the nonreciprocal EM mode originates from the combined function of the MSP resonance and the broken time reversal symmetry in MMs. To further reveal the mechanism for triggering the unidi-rectional EM mode, the scattering amplitudes of the systems are calculated as well so that it can be understood in a clearer manner. Finally, the unique EM characteristic can be exploited to engineer some EM waveguiding devices, such as the one-way waveg-uide and the bender, which have the immunity to the obstacles placed in the channel of the designed devices.Finally, a conclusion is summarized and the outlook is also presented in the last chapter.