Terahertz absorbing properties of different metal split-ring resonators

Terahertz modulator, filters and absorbers are the key parts of terahertz application, while the metal split ring is the common structure of these applications. Comparisons of terahertz absorbing properties, which were caused by different structures of subwavelength metal split ring resonator, were studied by simulation and experiment. Two split ring resonators which had different split gap types were fabricated. By using Finite Difference Time Domain(FDTD) simulation and Optical Pump Terahertz Probe (OPTP) experimental methods, the terahertz transmittance curves of TM mode and TE mode were investigated when the electromagnetic waves were perpendicular to the samples. The analysis found that in TM mode, the frequency of the absorption peak was inversely proportional to the value of the effective inductance and the effective capacitance. But in TE mode, the similar resonance frequency of the two SRRs were caused by the same length of dipole resonance. In addition, when optical excitation power changed, the experimental result indicates that one-gap SRR is more sensitive than two-gap SRR in TM mode. As the pump light power up to 5 mW, the resonance frequency transmittance of one-gap SRR raised 80% than the pump light condition at 0 mW. But, two-gap SRR only raised 43% when the light condition changed from 0 mW to 5 mW.