Origin of the plasma scalds in dielectric coatings induced by 1ω laser

摘要

The plasma scalds initiated by a 1053 nm(1ω) nanosecond laser are separated from the defect-induced damage pits, which is verified as a result of the ionization wavefront with the subnanosec-ond laser. Considering the beam reflection from solid-state absorption fronts during the damage process, a theoretical scalding threshold about 6.84 J/cm~2 (12ns) based on the energy required to start an air avalanche is evaluated and agrees well with the experimental scalding threshold. The occurrence order of the initial explosion and subsequent ionization wavefront is verified to explain most of the damage morphologies caused by the 1ω laser. In addition to the significance in laser conditioning or cleaning for a high-power laser system, the results also indicate that through the occurrence of plasma scalds it is possible to mark the onset time of air plasma during laser-coating interaction.