Design of multiband terahertz filter

Based on the different resonant responses to the electromagnetic fields produced by different sizes of square closed-ring resonator (CRR)，a terahertz(THz) multiband filter comprised of 6 CRRs was proposed. By utilizing the finite-difference time-domain method (FDTD),the transmission characteristic of the filter was studied.It is found that the filter can produce six-band filtering performance when the electromagnetic(EM) wave is incident to the plane of the resonant ring normally or obliquely, and the filtering performance of the THz filter is independent to the variation of the incident angle of EM wave due to the symmetry of square closed-ring resonator. This design increases the number of the filtering band so as to improve the frequency sensitivity. The proposed method can provide a theoretical tool to perform multiple angles sensors, THz communication technologies and so on.