Neutral particle acceleration by spatially modulated laser pulses

The velocity gain of neutral particles (atoms, molecules, etc) from laser acceleration is always small. A possible scheme to obtain a high speed neutral particle beam is multistage acceleration. However, according to previous theoretical and experimental studies, generally, lateral acceleration is larger than longitudinal acceleration. These transverse velocities destroy the expected quality of the longitudinally transmitted neutral particle beam. In order to realize multistage accelerations of neutral particle, it is necessary to restrain the beam divergence caused by lateral acceleration. How to optimize and utilize these laterally accelerated neutral particles is worthy of in-depth study. In this paper, we use a multi-mode combined laser pulse and a flattened Gaussian laser pulse to accelerate the neutral atoms. The transverse divergence of the beam is well controlled while the longitudinal acceleration is retained, which provides the possibility for improving the beam quality of neutral particles as well as the corresponding multistage acceleration.