Ponderomotive acceleration of ions: Circular versus linear polarization

Ponderomotive (or radiation pressure) acceleration is a route to the generation of high-energy ions in laser-solid interactions, which does not rely on the generation of fast electrons. It may be optimized by the use of circularly polarized (CP) laser pulses rather than linearly polarized (LP) ones, since for CP, fast electron generation is strongly inhibited, quenching competing mechanisms such as target normal sheath acceleration. We present a comparison of 1-D and 2-D particle-in-cell simulations for CP and LP, which shows the potential of CP pulses for ion acceleration. The comparison also enables us to discriminate 'pure' ponderomotive effects from those due to fast electrons, aiding the understanding of basic mechanisms of ion acceleration and surface rippling.