Design and Verification of a Terahertz Bandpass Filter using a Spoof Surface Plasmon Polariton Waveguide with Gapped Unit Cells

TL;DR

This paper experimentally verifies a terahertz bandpass filter using spoof surface plasmon polariton waveguides with gapped unit cells, demonstrating tunable cutoff frequencies and a center frequency around 1 THz.

Contribution

It introduces a novel SSPP-based THz BPF design with gapped unit cells, validated through fabrication and measurements, showing agreement with simulations.

Findings

Center frequency around 1 THz with 0.25 THz bandwidth.

Lower and upper cutoff frequencies at approximately 0.91 THz and 1.16 THz.

Experimental results match simulation predictions.

Abstract

This paper presents the experimental verification of a planar guided-wave terahertz (THz) spoof surface plasmon polariton (SSPP) bandpass filter (BPF) using a coplanar stripline (CPS) with internal grooves and periodic gaps. The proposed BPF operates by combining the low-pass behavior from the SSPP's band edge and the high-pass behavior from the gaps that act as series capacitors. The higher and lower cut-off frequencies can be tailored by the appropriate selection of the unit cell geometry. For demonstration, a BPF with a center frequency of approximately 1 THz and a bandwidth of 0.25 THz was designed, fabricated, and experimentally validated. The passband around 1 THz is observed in the measurements, along with the lower and higher cut-off frequencies at approximately 0.91 THz and 1.16 THz, respectively, in agreement with simulation results.