Realization of a multi-band terahertz metamaterial absorber using two identical split rings having opposite opening directions connected by a rectangular patch.

A multi-band metamaterial absorber in the terahertz regime using a periodically arranged surface structure placed on an ultra-thin insulating dielectric slab backed by a metallic ground plane is demonstrated in this paper. Its surface structure consists of two identical split rings having opposite opening directions connected by a rectangular patch. The surface structure can have a strong electromagnetic interaction with incident terahertz waves, thereby generating two localized resonance absorption peaks with different frequencies, and the superposition effect of these two absorption peaks gives rise to dual-band absorption. With the aid of the near-field distributions of the two absorption peaks, the physical mechanism of the dual-band absorption is revealed. The dimension changes of the surface structure, including the split rings and the rectangular patch, play a key role in controlling and adjusting the resonance performance of dual-band absorption. Further optimization of the surface structure without increasing the number of sub-resonators provides the ability to increase the number of absorption peaks, which is different from prior multi-band absorption devices that typically require more sub-resonators in their surface structures. Multi-band metamaterial absorbers designed in this paper should have great application prospects in the field of terahertz absorption.