Programmable Ultrafast Temporal Responses in Terahertz Metasurfaces Via Spatial Defect Engineering

Space and time are two fundamental aspects of light‐matter interactions. Spatially selective control of light‐matter interactions led to the advent of “metamaterials”, enabling plethora of exotic electromagnetic phenomena, novel functionalities, and highly efficient electromagnetic devices. However, control over the temporal domain, especially at ultrafast timescales is still lacking, as it is primarily dictated by the charge‐carrier dynamics of naturally occurring photoactive material that is embedded within the metasurface geometry. Here, we present a versatile and scalable platform for full control of ultrafast temporal response, enabled by synergistic integration of spatially selective defect engineering in a silicon substrate, photoexcitation properties of silicon, and terahertz metasurface design. We have experimentally demonstrated– (i) modification of the temporal response of the metasurface by over four orders of magnitude, (ii) designer dynamics showing dual temporal components with varying proportions, and (iii) metadynamics, i.e., temporal response beyond that of defect‐engineered silicon material. The proposed platform will enable the exploration of novel temporal manipulation of light‐matter interactions for fostering technological innovations in next‐generation photonics and wireless communication systems.