Enhanced Q-factor in Optimally Coupled Macrocell THz Metamaterials: Effect of Spatial Arrangement

We present a study of a novel coupling scheme based on the use of two traditional single-gap split ring resonators (SRRs) and two asymmetric double-gap split ring resonators (ASRs) that have different spatial arrangements. Each unit cell consists of two resonator elements. In particular, the two-SRR and two-ASR unit cells are arranged in vertical, horizontal, and diagonal configurations to form a terahertz (THz) macrocell in a large metamaterial (MTM) array. Surprisingly, our results show that the diagonal arrangement in both types of resonators exhibits a strong resonance enhancement, leading to significant improvement in the quality factor (Q-factor) of SRRs and ASRs. Numerical simulations reveal stronger currents being excited for the diagonal macrocell of both types of MTM resonators. This observation is mainly due to optimal coupling between the resonators in the diagonal arrangement that causes subradiant scattering and reduced radiation damping. This coupling scheme could be easily implemented in MTMs across most part of the electromagnetic spectrum in order to minimize undesired radiation losses. We further investigate the effect of mutual interaction on the transmission and the Q-factor of the fundamental resonances in three different kinds of spatial arrangements.