Studies of hot electrons and protons generated from micro droplet plasmas irradiated by ultrashort laser pulses

Abstract

In the two-dimensional simulation of the interaction of an ultrashort intense laser with droplet plasma, two hot electron jets generated by resonance absorption and emitted symmetrically with respect to the laser propagation direction are observed at a low laser field amplitude such as $a_0=0.1$. However, the emission angle of electron jets cannot be explained simply with the theory of resonance absorption for planar targets. When the laser amplitude is increased to $a_0=2$, electron bunches generated by the ponderomotive force separated by a laser period are superimposed into the hot electron jets. Accelerated ions have two groups at low laser intensities, one is anisotropic and associated with hot electron jets and the other is isotropic due to hydrodynamics expansion. At high light intensities, isotropic ion acceleration is found through Coulomb explosion.