Terahertz metasurfaces with high Q-factors

We propose asymmetric D-split resonators as unit cells for high Q metasurfaces. In such resonators, current trapped modes lead to in-phase oscillations of antisymmetric currents. Thus, radiation losses are suppressed, enabling Q-factors beyond the ones obtainable in symmetric designs. We compare the proposed structure against both asymmetric and symmetric split ring metasurfaces and find an improvement in terms of Q by a factor of two and ten, respectively. Transmission measurements in a terahertz spectrometer provide experimental proof of the high Q-factors and agree well with numerical simulations. In the future, asymmetric D-split metasurfaces could be employed as high-performance sensors or filters.