A Terahertz Bandpass Filter Using a Capacitive Transition Circuit and a Spoof Surface Plasmon Polariton Waveguide

Abstract

This paper presents a novel terahertz (THz) bandpass filter (BPF) based on a spoof surface plasmon polariton (SSPP) waveguide with a center frequency of 1 THz and a 3 dB bandwidth of 0.3 THz. The proposed BPF comprises cascaded high-pass and low-pass elements. The high-pass element is a capacitive gap in the SSPP transition circuit, and the low-pass element is the SSPP waveguide itself. We find that the measurement results, including cut-off frequencies, align well with the theoretical predictions and simulations. To the authors' knowledge, the proposed SSPP BPF is the first of its kind.

Figures (10)

• Figure 1: Fabricated THz SSPP BPF on thin Si-N membrane with CPS feedlines and transition circuits for excitation and Tx/Rx PCS for THz generation and detection.
• Figure 2: Cross section of CPS feedlines on the thin Silicon Nitride membrane.
• Figure 3: CPS to SSPP transition circuit dimensions for the proposed BPF
• Figure 4: BPF Unit Cell Dispersion Curves, determining upper cut-off frequency. Unit cell dimensions: $d$ = 20 µ m, $a$ = 10 µ m, $W_0$ = 90 µ m, 21 µ m $\leq H_n \leq$ 70 µ m.
• Figure 5: Transmission response ($S_{21}$) of the SSPP BPF structure with variable $H_n$ from 28 µ m to 70 µ m when the conductor is modeled as PEC.