Active terahertz frequency conversion on silicon-based time-varying metasurface

Terahertz (THz) metasurfaces have emerged as the preferred material for active devices, with numerous potential applications. However, due to a lack of materials with an ultrafast response, functional devices with fascinating time-varying phenomena remain to be explored. In this study, we experimentally investigated a time-varying THz metasurface with silicon–gold hybrid structures. The results show that the transmission spectra undergo a remarkable transformation when an optical pump is used. A transient time boundary is introduced to study the time-varying response using the sudden change in silicon conductivity in the presence of an optical pump. We observed the generation of new spectral components, and the magnitude of the converted wave is linear with the incident power. The proposed silicon-based THz time-varying metasurface paves the way for developing THz sources and nonlinear optical devices.