Dynamic Antireflection and Reflectance Terahertz Modulator via Impedance Matching Using Composite Ge₂Sb₂Te₅/VO₂ Phase-Change Thin Films

Numerous functional materials have been investigated for impedance-matching-based terahertz (THz) antireflection; however, their practical utilization is significantly constrained by complex switching mechanisms, stringent excitation conditions, and challenging fabrication processes. In this study, we propose a novel method for THz wave amplitude modulation utilizing a VO₂/GST(Ge₂Sb₂Te₅) composite phase-change material interface, enabling efficient switching control and multiangle reflection modulation. By optimizing the device manufacturing process, we developed a modulation device that exhibits excellent antireflection performance at room temperature and can efficiently modulate the switching of THz signals. The unique advantages of this structure arise from the reversible phase transition properties of VO₂, which enable dynamic reflection modulation. This study goes beyond temperature-driven THz modulation by exploring the potential of current-driven dynamic control, significantly enhancing the device's modulation flexibility. Experimental results show that this composite phase-change interface structure achieves an amplitude modulation depth of 89.5% and exhibits superior reflection modulation performance across a wide angular range from 15 to 45°. Notably, the proposed structure has a broad response bandwidth spanning from 0.2 to 1.5 THz, ensuring robust performance over a wide spectrum of terahertz frequencies. This innovative structure not only offers new theoretical foundations and technical pathways for designing terahertz modulation devices but also establishes a solid foundation for expanding the application domains of terahertz technology.