A terahertz stop band filter based on two parallel metallic surfaces textured with groove arrays

In this paper, a compact terahertz stop band filter is presented, which consists of two parallel metallic surfaces corrugated with rectangular groove arrays of period a. When a metallic surface is periodically corrugated, surface electromagnetic modes can be excited by incident terahertz waves. These modes are surface plasmon polaritons with an effective plasma frequency controlled entirely by the surface geometry. Because of the corrugated grooves and geometry induced highly confined surface plasmon polaritons, the fundamental mode of the parallel metallic plates splits into two modes and there is a band gap between the two modes. The band stop filtering functionality is realized by rejecting all frequencies in the gap. Simulation results calculated by finite element method show that the proposed structure has a band gap ranging from 0.315c/a to 0.350c/a for groove depth d = 0.5a, groove width l = 0.5a and gap width of the two parallel metallic surfaces w = 2a. Transmission spectra also show zero transmission within the band gap region where no guided modes are supported. By varying the gap width w and groove depth d, different filtering bandwidths with different center frequencies can be achieved.