Collimated particle acceleration is demonstrated by using a linearly polarized Petawatt Hermite-Gaussian (HG) laser in three-dimensional particle-in-cell simulations and experiments. The relativistic HG(1,0) mode is shown to be feasibly generated by reflecting a laser pulse off a two-dimensional π-phase-shift mirror, followed by focusing with a parabolic mirror, both compatible with existing Petawatt laser facilities. A high-quality electron beam slice accelerated by the strong longitudinal electric field near the laser axis. Furthermore, a well-collimated electron and ion beam is maintained in three dimensions by a self-generated magnetic field around the electron current. This 3D collimating acceleration mechanism driven by a 2D phase-modulated HG laser provides a promising approach for compact high-energy particle sources, with potential applications in advanced accelerators, ultrafast electron diffraction, and imaging.

electron acceleration,proton acceleration