Optimal laser pulse energy partitioning for air ionization
  We investigate the pulse partitioning of a 6.3 mJ, 450 fs pulse at 1030 nm to produce plasma channels. At such moderate energies, splitting the energy into several sub-pulses reduces the ionization efficiency and thus does not extend the plasma lifetime. We numerically show that when sufficient energy to produce multifilamentation is available, splitting the pulse temporally in a pulse train increases the gas temperature compared to a filament bundle of the same energy. This could improve the mean free path of the free electrons, therefore enhancing the efficiency of discharge triggering. 
Elise Schubert, Jean-Gabriel Brisset, Mary Matthews, Antoine Courjaud,   J\'er\^ome Kasparian, Jean-Pierre Wolf
physics.plasm-ph physics.optics