Dynamics of Pulsed Laser Clearing of Soot Particles and its Effects on a Co-Propagating CW Laser

Directed energy (DE) systems often operate in contaminated atmospheric environments where particulates from combustion, battlefield obscurants, or environmental dust degrade beam quality through scattering and absorption. This study presents initial experimental results of a laser clearing technique that uses a nanosecond-pulsed 1064 nm Nd:YAG laser to vaporize suspended soot particulate over a 30-foot propagation path seeded by combusted rubber gasket material. The goal is to pre-condition the optical path using high energy laser pulses to clear particulates before the use of a high-energy continuous-wave (CW) or additional pulsed DE laser systems. The optical properties of moderately sized soot aggregates are shown to depend on both the complex structure of the particles and their material properties, both of which vary significantly. Imaging of CW probe and reference lasers before and after a nanosecond pulse shows a decrease in scattering along the entire beam path and indicates the occurrence of both particle vaporization and thermal blooming. Laser induced incandescence (LII) caused by the pulse reveals the presence of large soot particles within the beam path. The probe beam is imaged at rates up to 10 MHz and its response is captured immediately after the pulse, showing asymmetric deformation and localized heating along the path due to vaporization during the first 20