Laser conditioning of ZrO 2:Y 2O 3/SiO 2 mirror coatings prepared by E-beam evaporation

Abstract

Laser conditioning effects of the dielectric mirror coatings with different designs were investigated. Simple quarter-wave ZrO 2:Y 2O 3/SiO 2 mirrors and half-wave SiO 2 over-coated ZrO 2:Y 2O 3/SiO 2 mirror coatings were fabricated by E-beam evaporation (EBE). The absorbance of the samples before and after laser conditioning was measured by surface thermal lensing (STL) technology and the defects density was detected under Nomarski microscope. The enhancement of the laser damage resistance was found after laser conditioning. The dependence of the laser conditioning on the coating design was also observed and the over-coated sample obtained greatest enhancement, whereas the absorbance of the samples did not change obviously. During the sub-threshold fluence raster scanning, the minor damage about defects size was found and the assumption of pre-damage mechanism, based on the functional damage concept, was put forward. The improvement of the laser induced damage threshold (LIDT) was attributed to the benign damage of the defects and the dependence on the coating design owed to the damage growth behavior of different coating designs.