Simulation of terahertz transmission modulation based on nested metal resonator metamaterials

Metamaterials has shown outstanding flexibility and functionality in optics and electromagnetics, which attracted plenty of interest. Nested ring resonators have a wide range of applications in terahertz (THz) spectroscopy, sensing and communication. Hence, we design a kind of metamaterials structure which can modulate THz transmission and resonance. It consists of a circular split ring resonator (CSRR) inside a closed square ring resonator. The single CSRR has an inductive-capacitive (LC) resonance and the single closed square ring resonator has a dipole resonance. After nesting two resonators, the resonance mode is changed from single mode to double modes. The results show that the amplitude transmission of non-resonant region is related to the gap opening and the asymmetry of structure. The amplitude transmission of resonance region depends on the conductivity of substrate. With the gap opening of CSRR increases, the amplitude transmission of non-resonant region increase. Meanwhile, the frequency of resonance has an obvious blue-shift. With the bottom edge distance of the two resonators decreases(the asymmetry increases), the amplitude transmission of the non-resonant region increases gradually and the low frequency of resonance has a red-shift and the high frequency of resonance has a blue-shift. To further analyze the influence of conductivity of substrate on amplitude transmission, we change the conductivity of substrate during the simulation. The results demonstrate that with the conductivity of the substrate increases, the resonance absorption peak decreases until disappears, the amplitude transmission of the non-resonant region decreases. Our results may have the potential applications in THz modulator.