Photon‐Recycling Dielectric Laser Accelerator

ABSTRACT

We propose a photon‐recycling dielectric laser accelerator (DLA) system based on silicon‐on‐insulator platform. Our DLA system employs transverse‐magnetic optical mode as the primary energy source, modulated and injected into the electron‐light interaction region for long‐distance acceleration and modulation, and then recycled for the next round‐trip. We developed an adaptive inverse‐design algorithm to optimize the waveguide geometry, and identified an “optimal waveguide accelerator” with enhanced performance. Our loop recycles the residual post‐interaction optical field and reuses the photons across successive cycles, therefore enabling low‐power optical injection while sustaining high acceleration gradients for continuous electron beams. In the low‐beam‐loading regime, the recycling architecture enables high acceleration gradients with reduced external optical injection. Under an idealized high‐beam‐loading conditions, the model predicts an upper‐bound plug‐in photon‐utilization efficiency of 99.78%. Spectral analysis and electron‑beam dynamics further demonstrate that the optimized waveguide acts as a time‐gated, phase‐sensitive energy filter, selectively manipulating phase‐matched electrons within a designed energy window. Our photon‐recycling DLA therefore provides not only a platform for low‐energy electron acceleration, but also a route toward narrow energy selection combined with downstream timing or energy‐selection elements, which can be further applied to explore free‐electron quantum optics engaging with the advancing field of photonic integrated circuits.