Investigations of laser-induced damages in fused silica optics using x-ray laser interferometric microscopy

Abstract

A novel x-ray laser (XRL) application, aimed at understanding the microscopic effects involved in formation of laser-induced damage in optical materials exposed to high-power sub-ns laser pulses, is presented. Standard fused silica substrates with permanent damage threshold below 20 J/cm2, when irradiated by 438 nm laser pulses, were probed in situ by a neonlike zinc XRL at 21.2 nm. The probing beamline employed a double Lloyd’s mirror x-ray interferometer, used in conjunction with an imaging mirror to achieve magnification of ∼8. In conjunction with an array of in situ optical diagnostics, the main question addressed is whether the damage on the rear surface of the beamsplitter is transient or permanent. The second issue, examined by both the x-ray interferometric microscopy and the optical diagnostics, is whether a local rear-surface modification is associated with nonlinear effects such as self-focusing or filamentation of the damaging laser beam in the bulk.

An extreme ultraviolet interferometer suitable to generate dense interference pattern

“…The interferometer mechanical design was largely inspired by the double Lloyd mirror XUV interferometer constructed on PALS installation 23,24 . Unfortunately, due to space problems in our experimental chamber and due to much smaller robustness of our micro-positioners it was inevitable to leave the concept of common platform for both mirrors that can Si and Sc (see tab.…”