Abstract

In this paper, we will discuss recent work that has taken place at the Laser Induced Damage Facility that is currently under development at the Institut für Technische Physik at Deutsche Forschungsanstalt für Luft- und Raumfahrt (DLR) in Stuttgart, Germany. The coatings discussed in this paper were selected for "out of band" studies to ensure that damage would proceed at fairly low levels. It is the unique nature of the damage that makes this a useful study into the mechanism of defect dominated damage. The samples were found to contain defects that were uniformly distributed through out the coating with a separation between defect sites of about 10μm. A second unique property is that the coating defect ensemble appears to be degenerate, i.e. there is a single defect type whose onset of failure takes place at a specific fluence. As higher fluence levels are attained, sets of micro-fracturing and pits form around the origional defect area that eventually coalesces into macroscopic damage. Higher fluence levels induce catastrophic coating failure on a macroscopic scale.

© 1995 Optical Society of America