Revised models for the underlying physics and mitigations of laser induced filamentation damage in large aperture laser optics

The necessity for durable optics for higher laser fluences and intensities grows as new technological advancements allow for increased peak powers of laser systems. This has motivated a substantial effort in the last decades to better understand laser induced damage mechanisms and their mitigation. One major damage mechanism limitation to laser systems at high peak intensities is filamentation in fused silica glass, due to Kerr self-focusing of the light [1], that has been motivating an on-going effort for the last few decades [2]. The past studies had led to a set of simplified rules that allows for the operation of laser system below the onset point for this mechanism to take place, namely what is known as the IL rule (intensity times the collapse distance before filamenting equals some empirical constant) and the Bespalov-Talanov (BT) perturbation growth theory [3-6]. The need to increase the laser beam intensities and optimize the throughput, closer to the point where the optical propagation length in the material is comparable to the predicted filamentation distance, requires revisiting and improving our understanding of the current rule set. This is especially emphasized by the shortcomings of these two highly useful yet under-justified models for the relevant situations of large aperture beams where the contrast perturbations on the beam are the seed for the filamentations (i.e., and not whole beam collapse).