Novel THz Metamaterial Designs: From Near- and Far-Field Coupling to High-Q Resonances

In this paper, we review recent research on terahertz (THz) metamaterials focusing on structures which exhibit sharp resonances with high quality factors. After a short introduction to common design concepts, near-field measurements are presented to discuss the resonant coupling and excitation mechanisms. High- Q-factor metasurfaces based on symmetric and asymmetric resonators, characterized by far-field transmission measurements, are discussed including structures with trapped and high-order resonance modes. Numerical simulations of the current distributions inside the metaatoms give insight into the resonance mechanisms. The novel structures discussed here offer intriguing properties and have potential applications in design and development of filters, thin-film sensors, and slow-light devices.