Dual-gratings with a Bragg reflector for dielectric laser-driven accelerators

Abstract

The acceleration of a beam of electrons has been observed in a dielectric laser-driven accelerator with a gradient of 300 MV/m. It opens the way to building a particle accelerator “on a chip” much more cheaply than a conventional one. This paper investigates numerically an efficient dielectric laser-driven accelerating structure, based on dual-gratings with a Bragg reflector. The design of the structure boosts the accelerating field in the channel, thereby increasing the accelerating gradient by more than 70% compared to bare dual-gratings, from analytical calculations. This is supported by two-dimensional (2D) particle-in-cell simulations, where a 50 MeV electron bunch is loaded into an optimized 100-period structure to interact with a 100 fs pulsed laser having a peak field of 2 GV/m. It demonstrates a loaded accelerating gradient of 1.48 ± 0.10 GV/m, which is (85 ± 26)% higher than that of bare dual-gratings. In addition, studies of the diffraction effect show that the optimized structure should be fabricated with a vertical size of J/wx ≥ 0.20 in order to generate an acceptable accelerating performance.