Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

摘要

We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>1017 W/cm2). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 1019 W/cm2. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated using time-resolved Ka spectroscopy. Measurements of the time-resolved Ka radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.