Electromagnetically Induced Transparency In Metamaterials

Recently, many novel electromagnetic properties, such as artificial magnetism, negative refraction and optical cloaking, emerge along with metamaterials. These new phenomena cannot happen naturally. Research on the topic of metamaterials will not only deepen our understanding of wave propagation in artificial structures,but open new perspective for manipulating electromagnetic waves. Eventually,photons will become the next-generation information carrier instead of electrons.Electromagnetically induced transparency (EIT) was first found in three-level atomic system in1980s. From then on, EIT is one of most important fields in quantum optics. Theoretical and experimental studies have found that EIT is a quantum interference effect. Under the condition of EIT, The atomic medium exhibits unique optical properties:high transmission, steep dispersion and enhanced nonlinearity. Based on these unique properties, the EIT effect has very useful application in light speed reduction, optical quantum storage, generation of nonclassical light, realization the entanglement between light and atoms. However, because of the relatively high requirements of EIT in three-level atomic system on the physical environment (for example, often requires very low temperatures), the experiment is very difficult to achieve. With the proposal of metamaterial, it was found that we can take advantage of the idea of "artificial atoms" to achieve EIT.This thesis focuses on the classical analog of EIT in Metamaterials.In the second chapter, We combine the two "magnetic artificial atoms" to form a "magnetic molecular". We array the "magnetic moleculars" to construct a magnetic metamaterial. Due to destructive interference of the local magnetic field, EIT effect appears in this system. We give a qualitative physical explanation by the perspective of an analog three-level atomic system. At the same time, we give a quantitative interpretation with the magnetic susceptibility. In the transparent window, the group index is about6. which is much smaller than the one in plasmon system. This is becaus the magnetic resonance is much weaker than the electric resonance, which results in much weaker dispersion in a magnetic metamaterial. From the relationship between the group refractive index and the refractive index, we can find that, the group refractive index and the dispersion in refractive index are positively correlated.In the third chapter, We design a metal rod structure and two different Split-ring resonators (SRRs). With FDTD method, we adjust their size to make them to have resonant modes at the same frequency. We combine the metal rod with the two SRRs respectively, as a result, two different single-mode EIT-like metamaterials are formed. Further, we put these three structures together to get a dual-mode EIT-like metamaterial. Finally, we fabricated the structures with optical etching method. We measure the optical response of our samples with terahertz time domain spectroscopy. The finding provides scientific basics for developing new electromagnetic materials as well as opening new perspective in manipulating the electromagnetic waves.