Hybrid vanadium oxide terahertz micro-ring resonator waveguide on silicon platform

Abstract Micro-ring resonators (MRRs) have demonstrated excellent performance in high-precision filtering and sensing due to their high Q-factors, compact structure, and strong frequency selectivity. However, the tunability of MRRs remains severely limited by the intrinsic response speed and range of conventional materials, especially in the terahertz (THz) frequency band. Here, we propose a hybrid vanadium oxide (VO 2 ) THz MRR waveguide on silicon platform, which consists of two VO 2 -embedded circular micro-rings separated by a rectangular waveguide. Unlike other active materials, VO 2 exhibits a unique insulator-metal transition, where its conductivity can increase by 4–5 orders of magnitude under electric, light, or thermal excitation. Simulations results show that the resonant modes of the proposed MRR waveguide can be effectively switched by tuning the conductivity of the VO 2 layer, whose mechanism is attributed to the coupling effect between the micro-rings and the central waveguide. When VO 2 is in its insulating phase, the device operates in the 1.41–1.52 THz range, which achieves a maximum extinction ratio of 39 dB at 1.465 THz with a Q-factor of 3662. The extinction ratio is continuously tunable from 1 dB to 39 dB through thermal excitation, which corresponds to a modulation depth of up to 97%. The proposed VO 2 -integrated MRR waveguide offers promising potential for real-time tunable THz components such as filters, modulators, and sensors in next-generation THz communication, imaging, and spectroscopy systems.