ABSTRACT
In this paper, we propose what we believe to be a novel coupling mechanism for generating quasi-bound states in the continuum (quasi-BIC) in symmetrical metasurface structures. We demonstrate for the first time in theoretical predictions that supercell coupling can induce quasi-BIC(s). We utilize the coupled mode theory (CMT) to analyze the physical mechanism for the generation of quasi-bound states in such symmetrical structures, which result from our investigation of the coupling between sub-cells that are separated from supercells. We verify our theory by using both full-wave simulations and experiments.
ABSTRACT
Terahertz spectroscopy is a powerful tool for investigating the properties and states of biological matter. Here, a systematic investigation of the interaction of THz wave with "bright mode" resonators and "dark mode" resonators has been conducted, and a simple general principle of obtaining multiple resonant bands has been developed. By manipulating the number and positions of bright mode and dark mode resonant elements in metamaterials, we realized multi-resonant bands terahertz metamaterial structures with three electromagnetic-induced transparency in four-frequency bands. Different carbohydrates in the state of dried films were selected for detection, and the results showed that the multi-resonant bands metamaterial have high response sensitivity at the resonance frequency similar to the characteristic frequency of the biomolecule. Furthermore, by increasing the biomolecule mass in a specific frequency band, the frequency shift in glucose was found to be larger than that of maltose. The frequency shift in glucose in the fourth frequency band is larger than that of the second band, whereas maltose exhibits an opposing trend, thus enabling recognition of maltose and glucose. Our findings provide new insights into the design of functional multi-resonant bands metamaterials, as well as new strategies for developing multi-band metamaterial biosensing devices.
