Research On Electromagnetic Resonances And Tunability Of Metamaterials

Electromagnetic phenomena originate from interactions between light and materials. We can control the characteristic(such as direction, intensity and polarization) of electromagnetic waves with some electromagnetic materials. However, the performances and functionalities of some traditional optical components or devices composed by naturally existing materials can not always satisfy or meet our requirements and demands, even can not be realized. The most important reason for that is not the limitation of the computer performance or the fabrication technique, but the limitation of materials’ electromagnetic properties. Fortunately, metamaterial as an electromagnetic-property-designable artificial material can obviously improve and broaden the performances and designable spaces of optical components. In present work, we have studied the resonance mechanism of metamaterials, and investigated its modulation mechanisms. The main research contents and findings are followings:(1) Via the Lorentz and Drude models, we describe electromagnetic properties of naturally existing materials(such as dielectrics, metals and doped semiconductors). Then, we introduce the concept of artificial materials(metamaterials), and investigate some extraction methods of electromagnetic parameters for metamaterials.(2) Via the metamaterial mass-spring model, we study metamaterials’ resonance properties, such as the resonance wavelength and resonance intensity. Results show that resonance wavelengths are determined by the effective path length of free electrons, while the resonance intensities are related to the free-electron density and electric potential difference induced by electromagnetic wave in metamaterial unit cells. We simulate and measure the resonance characteristics of some common-structural metamaterials, and verify the proposed metamaterial mass-spring model. We also investigate the electric-resonance and magnetic-resonance properties of a typical-structural split-ring-resonator(SRR) metamaterial, and study its optical anisotropy.(3) Some common theories and methods describing permittivities of three-dimensional metamaterials have been introduced and deduced. We investigate and discuss the permittivity properties of three-dimensional particle metamaterials and three-dimensional layered metamaterials. Basing on research results above, an all-semiconductor optic-circuit board at the microscale is proposed, which can severe as a band-stop and polarization-independent filter. moreover, an ultra-compact dual-metamaterial quarter-wave plate is also presented, the thickness of which is only 0.58 μm.(4) Based on the principle of modulation mechanisms, we investigate and classify currently reported tunable two-dimensional metamaterials, and propose some optimization schemes and a new type of tunable metamaterials, which are made of semiconductors. In addition, we propose an electric-tunable three-dimensional metamaterial, which possesses a higher modulation depth than those of some current electric-tunable two-dimensional metamaterials.All these researches will not only provide a foundation for future intensive research of resonances of metamaterials, but will be helpful for designs, fabrications and explorations of higher-performance and new-functional optical components and devices based on twodimensional and three-dimensional metamaterials.