Engineering thermally tunable interface states in 1D topological photonic crystals with a phase-change VO 2 layer

We present a dynamically tunable one-dimensional topological photonic crystal that integrates a phase-change material, vanadium dioxide, at the interface between two topologically distinct dielectric multilayer stacks with ABBA and BAAB configurations. These arrangements exhibit contrasting Zak phases, resulting in a topologically protected interface state within a shared photonic band gap. By introducing a thermally switchable vanadium dioxide layer, we achieve active control over this interface mode through the material's reversible insulator-to-metal transition. Using the transfer matrix method, we systematically analyze the transmission, reflection, and absorption spectra under varying conditions, including vanadium dioxide phase, thickness, incident angle, polarization, and unit cell number. Our results demonstrate that the interface state's spectral position, intensity, and confinement can be modulated in real time, enabling precise control over light propagation. This expanded tunability highlights the potential of vanadium dioxide-integrated topological photonic crystals for reconfigurable, robust, and multifunctional photonic applications in sensing, logic, and optical communication across near-infrared and terahertz regimes.