Broadside Coupled Resonators for Real-time Tunable Metamaterials*

Metamaterials based on broadside coupled split ring resonators (BC-SRRs) exhibit large tunability induced by modulating the coupling that arises from mutual capacitance and inductance. We design and fabricate a real-time tunable terahertz metamaterial by integrating BC-SRRs with comb-drive actuators, and characterize the dynamic response using terahertz time domain spectroscopy. The experimental results reveal that we can control the amplitude and phase of the transmission coefficient dynamically by driving the comb-drive actuators. We also observe remarkable modulation in the group delay. A two-port resonator model, derived from coupled mode theory, can analytically explain the experimental results and unveils the critical role of coupling between BC-SRRs. The results demonstrate that the propagation of electromagnetic waves can be dynamically controlled through modulating coupled resonators in metamaterials.