Tunable Terahertz Free Spectra Range Using Electric Split-Ring Metamaterial

Abstract

A design of electric split-ring metamaterial (eSRM) with tunable terahertz (THz) free spectra range (FSR) characteristic is presented. The proposed eSRM is composed of double semicircle-shaped ring resonators with two connected metallic bars. By changing the radius of the semicircle-shaped ring resonators, the tuning ranges of FSR are 0.187 THz and 0.024 THz in transverse electric (TE) and transverse magnetic (TM) modes, respectively, which indicates eSRM could operate stably in TE and TM modes. Furthermore, eSRM exhibits switching and polarization-dependent characteristics by exploiting comb driver to control the distances between ring resonators along ${x}$ -and ${y}$ -axis directions. The electromagnetic responses could be tuned and switched between dual- and quad-resonance in both TE and TM modes. eSRM shows polarization angle-sensitive characteristic and the corresponding FSR could be tuned from 919 GHz to 336 GHz by changing the polarization angle of incident THz wave. In view of the above optical characteristics of eSRM, it is used for the sensing application exposed on different surrounding refraction index. The sensitivity, quality factor (Q-factor), and figure of merit (FOM) are calculated. The sensitivity is 0.457 THz/RIU and the average Q-factor and FOM are 40.65 and 35.47, respectively. These results indicate the proposed eSRM could be used in widespread applications, such as dual-/quad-resonance switches, polarization switches, and high-efficient environmental sensors. [2021-0006]