Optically Controlled Hybrid Metasurface for Efficient Terahertz Frequency Modulation

Terahertz waves exhibit considerable application value in fields such as high-speed wireless communication, nondestructive testing, and biomedical imaging owing to their broadband transmission and low photon energy characteristics. However, existing hybrid metasurfaces integrated with active materials suffer from the inherent electromagnetic response of the structure and limited reconfigurability, making broadband frequency modulation difficult to achieve. To address these challenges, this work proposes a terahertz metasurface frequency modulation device based on a composite structure of double-opening square split-rings and metal patches, and systematically investigates how the geometric parameters and the incidence angle govern the resonance characteristics. Numerical simulations show that adjusting the structural parameters and incidence angle can produce significant resonant frequency shifts and enable flexible modulation of the number and distribution of resonant peaks. On this basis, two germanium-based optically controlled hybrid metasurface schemes are further proposed. By embedding germanium in the key structural regions, dynamic frequency regulation is numerically demonstrated under optical pumping, with a maximum tuning range of 0.8 THz, exhibiting excellent dynamic modulation performance. The proposed metasurface combines the advantages of static regulation and active modulation, offering a new insight into efficient dynamic manipulation of terahertz waves and holding great promise for high-speed wireless communication and high-sensitivity biosensing.