The artificially structured metamaterials has led to many potential applications in terahertz regime, but the role in adjusting the terahertz transmission still needs to be carefully investigated. Currently, designs with split ring resonator (SRR) based metamaterials can provide a promising approach for understanding the terahertz transmission characteristics. In the experiments, a SRR-based metamaterial is proposed for presenting terahertz transmission characteristics. The substrate of the metamaterial is an n-type gallium arsenide (n-GaAs) film grown over a semiinsulating GaAs wafer. Then, the metallic film, fabricated on n-GaAs, is patterned into an arrayed four-gap microstructure according to traditional ultraviolet photolithography methods. The metal film and n-GaAs film form a Schottky contact. In the experiments, the transmission frequency spectrum of the metamaterial has an obvious fluctuation in the 0.6–1.23 THz and 1.52–2.4 THz range, and the experimental results show that the frequency region of the intensive oscillatory signal essentially agrees with that of the metamaterial characteristic transmission spectrum in the 0.5–2.5 THz range. The terahertz characteristic transmission spectrum of the fabricated metamaterial are measured at the central frequency of ~0.5, ~1.0, ~1.5, ~2.0 and ~2.5 THz, thus the oscillation characteristics can be explained by dipole resonance. The measured time-domain transmission signals and corresponding frequency responses based on the metamaterial agree well with calculated results. Therefore, our research shows a potential application of the transmission adjusting roles in terahertz regime.
In order to observe more properties of an electrically resonant metamaterial-sensor, a single cubic unit of the matamaterial-sensor was simulated using the finite-element algorithm and Microwave Studios by CST. Meanwhile, an adaptive mesh refinement was used to ensure an accurate numerical solution with relatively short calculation time. In order to effectively conduct the simulation, some field monitors were also added to help the observation of electromagnetic properties of the unit. Through the electromagnetic simulation, the transmission and reflection spectra of the unit metamaterial-sensor were acquired. At the SRR gap, each kind of metamaterial-sensor structure presents an obvious resonant response at several THz frequency points. Simulation results indicated that the transmission was as low as 0.03 at ~0.79 THz. Other simulation results such as the surface current, the electric field, the electric energy density, and the power loss density, were also observed. By analyzing the simulation results, an idea to obtain the resonant strength in an indirect way was worked out and a way was found to realize the multispectral imaging in THz region.