Spatial and temporal profiles of pulsed laser-induced air plasma emissions

The laser-induced breakdown and energy deposition in air were studied using a full-width at half-maximum (FWHM) 6.5-ns pulse Nd:YAG laser. For the non-resonant breakdowns, two-dimensional spontaneous emission images were obtained with nanosecond resolution from breakdown to 10 times the FWHM of the pulse of the spatial and temporal variations of the energy deposition and plasma formation processes. The spatial emission features are compared with the predictions of the laser irradiance in the focal region that results from the focus lens aberrations. The statistical variation of the absorbed energy was determined over the energy range from below-to-approximately six times the breakdown threshold. Comparisons are made of the measured plasma wave speed with one-dimensional laser-supported radiation wave predictions. (C) 2000 Elsevier Science Ltd. All rights reserved.