Equivalent wavelength design method for dielectric laser accelerators under oblique laser incidence

Abstract

Abstract

Dielectric laser accelerators (DLAs) offer a promising route toward compact particle acceleration but have predominantly relied on normal-incidence laser illumination, limiting their integration into systems where normal laser access is geometrically constrained. In this paper, we propose a generalized design method for DLAs illuminated by an obliquely incident laser. By deriving the modified phase-matching condition and introducing the concept of an equivalent wavelength, we transform the oblique-incidence design into an equivalent normal-incidence configuration, significantly simplifying numerical simulations and structural optimization. Using the equivalent wavelength method, we designed both grating DLA and inverse design DLA separately. Experimentally, the grating DLA with a period of 960 nm was fabricated and driven by a 1030 nm laser incident at 21.6 deg. For 200 keV electrons, we measured the maximum energy gain of 1.6 keV and the maximum acceleration gradient of 125 MeV/m with a 9.6 μm length. Furthermore, the simulation results reveal that the inverse-designed DLA can achieve a maximum energy gain of 7.5 keV, exceeding the 5.97 keV obtained from the grating DLA structure. This equivalent wavelength design method can simplify the simulation model and improve design optimization efficiency.