On-chip terahertz bandpass filter based on substrate integrated plasmonic waveguide

Abstract In this paper, we propose and demonstrate a terahertz bandpass filter based on substrate integrated plasmonic waveguide (SIPW) using the standard 0.25-μm InP DHBT fabrication process. In this design, a Yagi-Uda antenna-like subwavelength array with effective asymptotic frequency reduction, is etched on the top metal layer of substrate integrated waveguide (SIW) to support a spoof surface plasmon polaritons (SSPPs) mode. The bandpass transmission with unique dispersion characteristics of the SIPW can be easily engineered by tuning the SIW and the SSPPs geometric parameters to independently adjust the low-cutoff and high-cutoff frequency, respectively. The simulated results show that, from the frequency range of 208 GHz to 265 GHz, the transmission coefficients is less than 2 dB, and the in-band reflection coefficients is better than 20 dB. To further verify the proposed design, a similar bandpass filter with geometry size scaled up operating in microwave frequency range is fabricated and measured. The measured results show that the great bandpass features and high-efficiency propagation are validated. In the passband of 13.5 GHz to 18.4 GHz, the reflection coefficients is better than 10 dB and the maximal transmission coefficients is 2 dB. Our work presents a novel 0.25-μm InP DHBT-based bandpass filter with dimensions of 900 μm × 285 μm in the terahertz range using SIPW for the first time, which may have extensive potential applications in integrated terahertz plasmonic devices.