Tunable strontium titanate terahertz all-dielectric metamaterials

Based on SrTiO₃ (STO) elliptical metamaterials (MMs) structures, the tunable propagation properties have been systematically investigated in the THz regime, including the effects of temperatures, incident angles, operation frequencies, and graphene Fermi levels. The results reveal that STO MMs manifest excellent thermally tunable properties, e.g. the amplitude and frequencies modulation depths are larger than 95.3% and 21.8% if temperature varies in the range of 70–320 K. The incident angles affect the resonant curves significantly, the amplitude modulation depth approximates 90% by changing the polarization angles, and the Q-factor reaches more than 20. The tunable Fano resonances can be achieved by utilizing a symmetrical STO-graphene structure. If the graphene Fermi level changes in the range of 0.3–1.0 eV, the amplitude modulation depth of transmission curve is more than 80%. The results are very helpful to understand the resonant mechanisms of ferroelectric MMs and design novel high Q-factor devices in the future, e.g. sensors, modulators, and filters. (paper)