Nonlinear Resonance Modulation in Single‐Crystalline VO ₂ ‐Integrated Si Ring Resonator

The metal‐insulator transition (MIT) in VO 2 , accompanied by a significant refractive index modulation, has attracted considerable attention for the development of Si‐based photonic integrated circuits. Previous approaches to integrating VO 2 films into Si photonics, however, have been limited by the loss of a steep transition due to structural and chemical disorders in VO 2 films on Si. Herein, we demonstrate steep modulation of optical resonance in VO 2 –Si hybrid modulators at telecom wavelengths using heterogeneous integration of single‐crystalline VO 2 films on Si. Based on theoretical simulations, we confirmed that nonlinear optical modulation occurs in the resonant wavelength (λ res ) by a steep phase transition in the epitaxial VO 2 films integrated on Si ring resonators. Interestingly, the unprecedented figure of merit for optical modulation strength (BM = 0.6) and transition sharpness ( = 1.65 ) were achieved in our hybrid ring resonator, which outperforms previous results using polycrystalline VO 2 –Si ring resonators. These findings highlight the potential of phase‐transforming materials for silicon photonics and offer a novel strategy for the unrestricted integration of high‐quality functional materials onto mature Si photonics platforms, advancing next‐generation optical communication and computing systems.