On-chip microwave oscillator in deep-subwavelength scale based on spoof plasmonic skyrmions

Exploring wave-matter interactions at extreme electromagnetic (EM) scales has long been a focal topic in multidisciplinary research, but deep-subwavelength field localization remains a persistent challenge. Here, we demonstrate an on-chip microwave oscillator with an electrical size of λ ₀/865 (λ ₀ is the operating wavelength) and a mode volume of 2.97 × 10^-11 λ ₀ ³ using the 0.18 μm complementary metal-oxide-semiconductor (CMOS) process. The physical insight is based on a spoof plasmonic skyrmion resonator realized by square spiral metal lines, which simultaneously functions as a frequency selector and an energy storage element for EM signal generation. A strongly-coupled excitation structure is proposed to efficiently concentrate EM energy into the deep-subwavelength resonance structure, and a complementary cross-coupled pair is employed to compensate for the high material loss resulting from the extreme energy concentration. This work paves the way for integrating the skyrmion resonances into the CMOS chips in extremely deep-subwavelength scale, and holds great promise for miniaturized integrated circuits and systems.