High-Q Subterahertz Spoof Localized Surface Plasmon Resonator Implemented in CMOS Integrated Circuit

Abstract

Resonators with high quality factors (Q-factors) serve as fundamental building blocks in terahertz technology, enabling promising applications in biosensing and on-chip integrated circuits. Although array resonators excited by spatial waves enable high-Q resonance with larger physical and electrical sizes, attaining a high Q-factor in a single on-chip integrated resonator using guided wave excitation at the subwavelength scale remains a significant challenge. In this work, we propose a complementary spoof localized surface plasmon (SLSP) structure that synthetically optimizes both absorption and radiation losses, thus achieving a high Q-factor. The design incorporates a coupled SLSP configuration to enhance the mode confinement, effectively minimizing the radiation loss. The complementary structure further enables the currents to flowthrough a broader metal area, which helps to reduce the absorption loss. The proposed resonator is realized using a 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS process, and operated at 140.13 GHz with an electrical size of <inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\lambda _{0}}$ </tex-math></inline-formula>/5.1, where <inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\lambda _{0}}$ </tex-math></inline-formula> is the free space wavelength. Experimental results show that the resonator chip achieves a measured Q-factor of 21.4. This compact design offers a feasible route for miniaturized plasmonic devices using the standard CMOS platforms at terahertz frequencies.