Terahertz bandstop filter using varying radii split-ring resonators

In this paper, we report a proof-of-concept terahertz bandstop filter constructed from split-ring resonators. The design comprises nine split-ring resonators, organized into three groups of three same radius. The radius of the groups is 13 µm, 14 µm, and 15 µm, respectively, and are placed between the conductors of a coplanar stripline. Each group of split-ring resonators results in notch filters with different center frequencies. The combined bandstop center frequency is 1.09 THz and the -3 dB bandwidth is 0.36 THz. The transmission response of the filter is measured using a modified terahertz time-domain spectrometer and we find agreement between theory, simulation, and experiment. This work demonstrates the viability of using varying-radii split-ring resonators as sub-wavelength filter elements for terahertz systems.