Beam modulation caused by the plasma scalds in the multilayer dielectric films

Abstract

The near-field phase modulation (NFPM) caused by the plasma scalds is investigated with a newly proposed mixed overcoat layer model. Based on the NFPM, the far-field intensity modulation (FFIM) is calculated and discussed with the scalar diffraction theory. The results indicate that both the NFPM and FFIM are sensitive to the scalding depth. A feature curve is developed to analyze the NFPM for arbitrary scalding depth. The modulation can be ignored when the scalding depth is less than the first feature point in the feature curve. Even though the diffraction intensity in the Fresnel region can be enhanced dozens of times, the FFIM in the Fraunhofer region can recover gradually if the scalding depth is below a critical value. The preliminary experimental results are consistent with the theoretical prediction.

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

“…Therefore, the plasma scalds may induce serious damage on downstream optics or weaken transmissive fluence. 5,6 The typical morphology of the plasma scalds was first reported by Genin and Stolz,7 and then characterized in detail by our group. 4 The occurrence of plasma scalds has been widely recognized as the typical damage morphology of 1x pulse in air and has continued to attract many researchers in recent years.…”