Laser-induced mirror coating damage

Laser induced damage to the coating of a precision beam-splitting mirror. This component is intended for use inside a high power laser system. The larger feature on the left is 0.14 mm long by 0.06 mm wide and about 5 microns deep. This is a good example of the type of damage to a coating that can occur due to repeated pulses from an high power laser beam interacting with the surface. In order to avoid this type of damage the optical coating quality, the surface cleanliness and the laser environment must be completely free from defects or contaminants of any kind. Defects within or on the coating surface at a submicroscopic level are not always possible to detect after coating manufacture. The only way to verify is to test under realistic conditions and determine if any damage occurs.