A Terahertz On-Chip Lowpass Filter Based on Spoof Surface Plasmon Polaritons

A new silicon germanium (SiGe)-based D-band lowpass filter (LPF) is proposed utilizing on-chip spoof surface plasmon polaritons (SSPPs). By analyzing the unique dispersion characteristics, the cutoff frequency of this on-chip SSPP-based LPF can be easily controlled by adjusting the width of the SSPP unit cell. Then, it can be further fine-tuned by modifying the length of the stub slot in the unit cell. For demonstration, an example of the proposed LPF is fabricated and experimentally tested, whose simulated and measured results are in good agreement. The measured cutoff frequency of the fabricated LPF prototype is 160 GHz. Due to its strong field confinement and flexibly tunable characteristics, the proposed on-chip SSPP structure is attractive for the applications in terahertz plasmonic devices and circuits.