Experiment on terahertz metasurfaces of metal split ring resonators with bound state in the continuum

A bound state in the continuum (BIC) is a wave that coexists with a continuous wave but remains localized. In the terahertz band, BIC can design devices with an ultra-high mass factor (Q factor), which is of great value for terahertz science and technology, so we designed a terahertz BIC metasurface structure composed of metal split ring resonators (SRRs). According to the symmetric protection principle of superlattice mode, the leakage process of BIC states to the far field is studied by changing the gap width of SRR. By introducing multiple SRRs and changing their arrangement, we obtain three superlattice modes and BIC states. The leakage of BIC states into the far field is observed experimentally, which means that observable quasi-BIC patterns are formed. We verify a feasible method that allows for flexible design and implementation of BIC.