Laser conditioning of UV anti-reflective optical coatings for applications in aerospace

In this work we study the effect of laser conditioning on laser-induced damage of ion-beam sputtered, anti-reflection coated laser optics with ns-pulsed laser radiation at a wavelength of 355 nm. With respect to applications in aerospace, measurements were performed under high vacuum. At laser fluences below 20 J/cm(2), laser-induced damage appears as pin-point damage (small explosion pits with sizes in the range of 1 lam), sometimes referred to as "grey haze". We find that ramped laser conditioning is an effective tool to reduce not only the abundance but also the average size of pin-point damage at laser fluences exceeding the optic's unconditioned laser-induced damage threshold. We discuss our results in the context of the small absorber model for damage crater formation.