Simulation of DLA grating structures in the frequency domain

Abstract

Dielectric laser accelerators (DLA) driven by ultrashort laser pulses can reach orders of magnitude larger gradients than contemporary RF electron accelerators. A new implemented field solver based on the finite element method in the frequency domain allows the efficient calculation of the structure constant, i.e. the ratio of energy gain to laser peak amplitude. We present the maximization of this ratio as a parameter study looking at a single grating period only. Based on this optimized shape the entire design of a beta-matched grating is completed in an iterative process. The period length of a beta-matched grating increases due to the increasing velocity of the electron when a subrelativistic beam is accelerated. The determination of the optimal length of each grating period thus requires the knowledge of the energy gain within all so far crossed periods. Furthermore, we outline to reverse the excitation in the presented solver for beam coupling impedance calculations and an estimation of the beam loading intensity limit.