Efficiently accelerated free electrons by metallic laser accelerator

Abstract Strong electron-photon (e-p) interactions occurring in a dielectric laser accelerator provide the potential for development of a compact electron accelerator, and certain critical features of the p-e interactions can be characterized well using ultrafast electron microscopy. Theoretically, metallic materials with notable surface plasmon-field enhancements can possibly generate a high electron acceleration capability. Herein, we present a design for metallic material-based on-chip laser-driven accelerators that show a remarkable electron acceleration capability, as demonstrated in ultrafast electron microscopy investigations. Under phase-matching conditions, efficient and continuous acceleration of free electrons on a periodic nanostructure is achieved. Momentum transfer via inelastic scattering is also studied in association with the electron beam acceleration. Importantly, an asymmetric spectral structure where the vast majority of the electrons are in the energy-gain states has been obtained in a periodic bowtie-structure accelerator. The nonlinear optical effects are found to promote the p-e interactions efficiently and improve the acceleration gradient to be as high as 0.335 GV/m. This demonstrates that a prototype metallic laser accelerator could provide a new way to develop compact accelerators on chip.