Physics-Based Optimization of Tapered Suspended Slot Waveguides for Electron Acceleration

In this letter, we present a physics-assisted design strategy for tapered suspended slot waveguides operating at 2 mu m. The proposed methodology enables a precise control of the optical field, specifically tailored for laser-driven dielectric accelerating structures. By using calibration curves that link the silicon waveguide strips width to both the effective refractive index and the accelerating field amplitude, we ensure local phase synchronism along the propagation axis. The design was performed for an input energy of 79 keV, and validated by HFSS simulations as far as the optical field computation is concerned, and by ASTRA-code for the single-particle beam dynamics. The results show an output energy of 102 keV with the optimized structure, corresponding to 20% increase compared to the previous constant-field approach.