Using short drive laser pulses to achieve net focusing forces in tailored dual grating dielectric structures

TL;DR

This paper explores how short laser pulses can be used to generate net transverse focusing forces in dielectric laser accelerator structures, potentially enabling stable relativistic electron acceleration.

Contribution

It demonstrates the use of transient short Gaussian laser pulses and optimized grating geometries to produce net focusing forces in DLA structures, which is a novel approach.

Findings

Short laser pulses induce significant net transverse forces.

Optimized grating geometries enhance focusing effects.

Phase dependence affects potential focusing lattice design.

Abstract

Laser-driven grating type DLA (Dielectric Laser Accelerator) structures have been shown to produce accelerating gradients on the order of GeV/m. In simple $\beta$-matched grating structures due to the nature of the laser induced steady-state in-channel fields the per period forces on the particles are mostly in longitudinal direction. Even though strong transverse magnetic and electric fields are present, the net focusing effect over one period at maximum energy gain is negligible in the case of relativistic electrons. Stable acceleration of realistic electron beams in a DLA channel however requires the presence of significant net transverse forces. In this work we simulate and study the effect of using the transient temporal shape of short Gaussian drive laser pulses in order to achieve suitable field configurations for potentially stable acceleration of relativistic electrons in the horizontal plane. In order to achieve this, both the laser pulse and the grating geometry are optimized. Simulations conducted with the Particle-In-Cell code VSim 7.2 are shown for both the transient and steady state/long pulse case. Finally we investigate how the drive laser phase dependence of the focusing forces could affect a potential DLA-based focusing lattice.