Electron acceleration via vacuum bubble field in Laguerre Gaussian laser

Enhancing the flux, brightness, and density of energetic electron beams is crucial for applications such as ultrafast electron diffraction, fast ignition in confined fusion, and free-electron lasers. Laser Wakefield Acceleration (LWFA) has demonstrated potential for accelerating collimated electrons up to 10 Giga-electron volts in 'bubble-like' plasma channels. However, its reliance on the plasma environment constrains the enhancement of acceleration stability and gradients. In contrast, Direct Laser Acceleration (DLA) does not depend on plasma and can achieve efficient acceleration with traditional Gaussian lasers. Nonetheless, traditional DLA often results in uncertain and divergent electron beams due to the ponderomotive force of the Gaussian laser. To overcome these limitations, our proof-of-principle experiments achieved collimated acceleration using a left circularly polarized Laguerre Gaussian (LG) laser in a DLA mechanism. Studies revealed that a novel vacuum bubble field formed by the LG laser is critical in simultaneously concentrating and accelerating electrons. This vacuum bubble field mechanism integrates the advantages of both traditional DLA and LWFA, offering significant benefits for applications such as particle collimation, high-flux particle sources, and coherent radiation sources in new relativistic regimes.