On‐Chip Control of Electron Emission with an Active Terahertz Metasurface

Terahertz (THz) radiation has emerged as a powerful tool for inducing ultrafast electron emission and controlling electron beams, with applications in photonics and electron microscopy. Here, the first realization of on‐chip electron emission control using an active THz metasurface is reported. The device integrates resonant dipole antennas and bias arms on a fused silica substrate, enabling precise modulation of electron trajectories through electrostatic control. Experimental results, supported by particle‐in‐cell simulations, reveal that electron emission via Fowler–Nordheim tunneling can be dynamically steered by varying the applied bias. A positive bias suppresses emission by attracting electrons to the bias arms, while a negative bias repels them, allowing trajectory control and the emergence of new emission features. Time‐of‐flight measurements show distinct shifts in electron emission behavior, with strong correlation to bias voltage and THz field strength. This work demonstrates a practical approach to integrating ultrafast electron control into chip‐scale systems.