Extending the range of hyperbolic metamaterials for THz electromagnetic waves through scaling methods

<p>Layered hyperbolic metamaterials (HMMs) are usually fabricated with extremely thin metallic and dielectric layers at a high THz working frequency range. However, the size and high working frequency have restricted the development and applications of layered HMMs. The small scale of HMMs and high losses of metallic layers in HMMs have also limited the cosmology applications of HMMs. This thesis has developed a novel scaling method that substitutes metals with dielectrics to perform the "metallic layer” function. The scaling of the HMM in this thesis thickens the thickness of each layer of the layered HMM.</p> <p>To evaluate the new methods (substitutions), the definition of permittivities and the reason why layered systems are effectively equivalent to uniaxial crystals have been rigorously reviewed. The cosmology related metamaterials theories have also been analysed. According to fundamental and cosmology-related theories, the possibility of not requiring metallic layers necessary for HMMs has been discovered. To explore the scaling methods details, all the essential properties and variables of HMMs have been analysed. It is concluded that the materials choices for HMMs are the most important.</p> <p>The main novelty in this thesis is feasible of a new scaling method that has been proved in theory, by simulations and by measurements. The “long wave” condition and losses were the main restriction for scaling. Dielectrics with negative permittivity were found to be the best substitutes for metals. These dielectrics also bring many advantages to HMMs, such as longer working wavelength (far infrared) range, lower losses, easier fabrication process, lower cost, and avoiding non-local effects. The polarisation and optical analysis in HMMs have been extended. The simulations have been carried out, which agree with the optical analysis. Some initial multi-layer and some single-layer samples have been fabricated using spin coating and measured at Terahertz frequencies. The results match the predictions and strongly indicate the feasibility of this scaling method.</p>