Coherent Control of Relativistic Electron Dynamics in Plasma Nanophotonics

Abstract Intense femtosecond laser pulses interacting with solids can drive electrons to relativistic energies, enabling miniaturized particle accelerators and bright extreme‐UV light sources. In‐situ space‐time control of these electrons is crucial for developing next‐generation laser‐based accelerators but remains extremely challenging. A novel approach is presented to achieve such control by manipulating the local fields driving these electrons using a nanoengineered dielectric nanopillar target. Via experiments and simulations, it is demonstrated that this sub‐femtosecond and nanometer‐scale control enables enhanced electron acceleration and control of the directionality of relativistic electrons over a wide angular range and predicts the coherent formation of sub‐femtosecond electron bunches from the nanopillars. This research bridges nanophotonics and strong‐field plasma physics, offering new opportunities for in‐situ control of high‐energy particles and advancements in plasma technology.