Tunable terahertz metamaterial by using asymmetrical double split-ring resonators (ADSRRs)

Abstract

Two designs of asymmetrical double split-ring resonators (ADSRRs) with one layer and two reflective symmetric layers are presented, which are composed of Au material on Si substrate. The electromagnetic responses of ADSRRs designs exhibit a single-resonance for g = 0 μm and dual-resonance in the range of g = 2 μm to 10 μm. By changing the gap width of ADSRRs with one layer, the resonant frequencies of two devices are blue-shifted 0.11 THz from 0.67 THz to 0.78 THz at TE mode and blue-shifted 0.07 THz from 0.62 THz to 0.69 THz at TM mode. To improve and perform the active tuning of ADSRRs, two devices are designed to compose of two reflective symmetric layers with a distance between top and bottom ADSRRs. By changing this distance, the tuning range of resonance is enhanced to 0.52 THz. Furthermore, two devices with one layer and two reflective symmetric layers exhibit a switch behavior by changing incident polarization angle. The maximum modulation depth is up to 93%. Therefore, the resonant frequency of devices can be tuned by changing the distance between top and bottom reflective symmetric ADSRRs to be realized as a THz filter and by changing the incident polarization angle to be realized as a THz switch. This study promises applications in THz filters, THz switches, and other controllable metamaterial-based devices.