Space-Time Wavefront Synchronized Terahertz Metasurface

Wireless communications demand high data rates, low latency, and ultra-reliable performance for future applications. This necessitates the development of high-speed, and programmable arrays across the spatial, temporal, and wave domains to compensate for path loss, extend spectral links, and expand spatial coverage. The current works face several challenges, including slow switch speed, narrow bandwidth, and constrained dual-space coverage in unconnected transmission-reflection integrated links. Here, we demonstrate two types of terahertz metasurfaces from the angle of energy-time and frequency-time functions, respectively, both have the ps-scale modulation speed under pulsed light excitations, and the space-time synchronized transmission and reflection links. In these devices, the terahertz wavefront can be modulated for energy covering 81.4% bandwidth using pump light with fluence of 100 µJ/cm², exhibiting dual-space synchronization with up to 92.2% similarity in holographic experiments. Our space-time ultrafast modulations enable dynamic beam steering, achieving over 88.6% modulation depth with a 4 × 42° field-of-view. Further, ultrafast beam steering with 21.8° dynamic range is experimentally characterized for the first time within a single pump pulse duration, approximately 250 ps. This novel scheme holds promise for the active manipulation of terahertz signals, which is crucial for photonics-terahertz systems in next-generation communications by smart structure materials.