Research On Double Split Ring Resonator In The Terahertz Region

Terahertz(THz) is a specific frequency range, and THz frequency range usually is in0.1THz-10THz (30um～3mm). THz wave is far- infrared band between the microwave and infrared bands. With the development of ultrafast laser technology, THz wave is have been extensively applied by people many years in a great many domain, such as biochemistry, communications, imaging and astronomy. With the development of micro-processing technology, the research of metamaterials is becoming more extensive and in-depth. For various electromagnetic frequency bands, a lot of modulators, filters, wave plates and lenses are made by people. In this paper, we combine the THz wave and metamaterials, studying the spectral characteristics of splits ring resonators (SRRs). The work focuses on the discussion about the research of SRRs based on polyimide substrate in THz bands and the research of the orientation dependence of THz detection in ZnTe.The first part is a research of double splits ring resonator, and the innovation point is based on polyimide substrate. Frist, we design an asymmetric and symmetric double splits ring resonators (DSRRs), and discuss the property of transmission and reflection about them. We find both the resonance intensities and resonance peak are modulated in the asymmetric and symmetric DSRRs, and the result of transmission and reflection trends a consistency. When the two gaps are away from the center in opposite direction, a giant amplitude modulation is observed and the resonant frequencies are observed red shifting. When the two gaps are away from the center in same direction, the resonant amplitude and resonant frequencies are unchanged. Second, we discuss the property of transmission by changing the THz angle of incidence and curvature of the sample. We find he resonant amplitude and resonant frequencies are unchanged. Third, we make a wide band filter by adding two sample together, and the50% of bandwidth can be achieved180GHz. In order to better study the polarization properties of metamaterials by time-domain spectroscopy system (THz-TDS) and apply them more extensive, we should have a in-depth understanding of polarization detection properties. The second part is that the electro-optic crystal (ZnTe) polarization detection characteristics in the terahertz time-domain spectroscopy system were investigated. The results show that the differential current associates with three factors which are direction of crystal axis, THz polarization direction and probe light polarization direction. According to theoretical analysis, the differential current is relevant to the angle (α) between the THz polarization and the crystal axis and the angle (φ) between the probe-beam polarization and the crystal axis. In the case of α=φ,α=φ+π/2,α=φ+π/4, the experimental results agree well with the calculation results.