Tunable terahertz metamaterial by using three-dimensional double split-ring resonators

•Tunable single-band and dual-band resonances.•The maximum tuning range of dual-band resonance is 0.55 THz.•Free spectrum range (FSR) can be tuned from 0.20 THz to 0.75 THz.•Tunable and switchable single-band and dual-band resonances.•High stability to allow manufacturing tolerance for widespread applications. We present an optically tunable terahertz (THz) metamaterial by using three-dimensional double split-ring resonators (3D-DSRR), which shows superior properties in adjustability. They exhibit tunable single-band and dual-band resonances by changing height between inner and outer SRRs. The maximum tuning range of dual-band resonance is 0.55 THz from the resonance of 0.45 THz shifted to the resonance of 1.00 THz. The corresponding tuning range of free spectrum range (FSR) spanned two resonances can be tuned from 0.20 THz to 0.75 THz. By changing radius of inner SRR from 14.5 μm to 22.5 μm, the tuning range of resonance is 0.40 THz. While changing the height between inner and outer SRRs and kept the radiuses of inner and outer SRRs as constant as 22.5 μm, 3D-DSRR can be tuned to have two resonances and then merge into one resonance. 3D-DSRR shows a tunable and switchable resonance for single-band and dual-band characteristics. These characterizations are very suitable for the use of tunable multi-resonance applications. To further investigate the stability of 3D-DSRR, the rotation angles of inner and outer SRRs are modified from 0° to 180°, respectively. The corresponding resonances are identical. Such results indicate the proposed device with high stability to allow manufacturing tolerance and potentially to be used in wearable electronic devices, pressure sensors, and other fields.