title: Scalable process for mitigation of laser-damaged potassium dihydrogen phosphate crystal optic surfaces with removal of damaged antireflective coating.
abstract: We investigate an approach for the recycling of laser-damaged large-aperture deuterated potassium dihydrogen phosphate (DKDP) crystals used for optical switching (KDP) and for frequency conversion (DKDP) in megajoule-class high-power laser systems. The approach consists of micromachining the surface laser damage sites (mitigation), combined with multiple soaks and ultrasonication steps in a coating solvent to remove, synergistically, both the highly adherent machining debris and the laser-damage-affected antireflection coating. We identify features of the laser-damage-affected coating, such as the "solvent-persistent" coating and the "burned-in" coating, that are difficult to remove by conventional approaches without damaging the surface. We also provide a solution to the erosion problem identified in this work when colloidal coatings are processed during ultrasonication. Finally, we provide a proof of principle of the approach by testing the full process that includes laser damage mitigation of DKDP test parts, coat stripping, reapplication of a new antireflective coat, and a laser damage test demonstrating performance up to at least 12  J/cm2at UV wavelengths, which is well above current requirements. This approach ultimately provides a potential path to a scalable recycling loop for the management of optics in large, high-power laser systems that can reduce cost and extend lifetime of highly valuable and difficult to grow large DKDP crystals.
authors.forename: S
authors.initials: S
authors.lastname: Elhadj
authors.forename: W A
authors.initials: WA
authors.lastname: Steele
authors.forename: D S
authors.initials: DS
authors.lastname: VanBlarcom
authors.forename: R A
authors.initials: RA
authors.lastname: Hawley
authors.forename: K I
authors.initials: KI
authors.lastname: Schaffers
authors.forename: P
authors.initials: P
authors.lastname: Geraghty