Overcoming High-Quality Limitations in Plasmonic Metasurfaces for Ultrasensitive Terahertz Applications
Ziheng Ren, Yuze Hu, Weibao He, Shun Wan, Siyang Hu, Zhongyi Yu, Xiang’ai Cheng, Zhongjie Xu, Tian Jiang
Abstract
In photonics, achieving high-quality ( Q ) resonance is crucial for high-sensitivity devices used in applications, such as switching, sensing, and lasing. However, high- Q resonances are highly susceptible to internal losses of plasmonic devices, impeding their integration into broader systems across terahertz and visible light bands. Here, we overcome this challenge by proposing a low- Q plasmonic metasurface for ultrasensitive terahertz (THz) switching and sensing. Theoretically, we reveal an approach to constructing a low- Q resonator possessing high sensitivity to nonradiative losses. Leveraging this mechanism, we design a highly sensitive plasmonic metasurface induced by strong coupling between a quasi-bound state in the continuum and a dipole mode. By hybridizing with the germanium layer, the metadevice exhibits an ultralow pump threshold of 192 μJ/cm 2 and an ultrafast switching cycle time of 7 ps. Furthermore, it also shows a high sensitivity of 224 GHz/RIU in refractive index sensing. The proposed paradigm of constructing low- Q and high-sensitivity photonic devices can be applied to biosensing, wide-band filters, and sensitive modulators.