# Method for Computationally Efficient Design of Dielectric Laser Accelerators

## TL;DR

This paper introduces an efficient adjoint variable method for optimizing dielectric laser accelerator structures, significantly improving their acceleration gradients with minimal simulations.

## Contribution

It applies the adjoint variable method to dielectric laser accelerators, enabling rapid optimization of structures for higher acceleration gradients.

## Key findings

- Optimized structures show greatly improved acceleration gradients.
- Only two electromagnetic simulations are needed for sensitivity analysis.
- Numerical optimization yields fabricable, high-performance accelerator designs.

## Abstract

Dielectric microstructures have generated much interest in recent years as a means of accelerating charged particles when powered by solid state lasers. The acceleration gradient (or particle energy gain per unit length) is an important figure of merit. To design structures with high acceleration gradients, we explore the adjoint variable method, a highly efficient technique used to compute the sensitivity of an objective with respect to a large number of parameters. With this formalism, the sensitivity of the acceleration gradient of a dielectric structure with respect to its entire spatial permittivity distribution is calculated by the use of only two full-field electromagnetic simulations, the original and adjoint. The adjoint simulation corresponds physically to the reciprocal situation of a point charge moving through the accelerator gap and radiating. Using this formalism, we perform numerical optimizations aimed at maximizing acceleration gradients, which generate fabricable structures of greatly improved performance in comparison to previously examined geometries.