Field localization in submicron-sized clusters and its effect on the ionization dynamics

Submicron-sized clusters are attractive targets in intense laser-cluster interaction experiments. The internal field in the Mie scattering regime is inhomogeneous and size-dependent. Here we investigate the field localization and its effect on ionization in submicron-sized clusters. The diffractive focusing reduces the ionization threshold of these clusters and leads to an ionization hotspot at the rear of the clusters. At a higher intensity, a skin layer of plasma at the front surface shields the field, stopping further rear side ionization. Interestingly, an unionized core with a plasma shell at a suitable condition may excite hybridization of plasmons, allowing transiently enhanced field beyond the skin depth. Control and optimization of the field localization and the resulting ionization may have practical importance for relevant laser-cluster experiments.