Diagnostics for the Detection and Evaluation of Laser Induced Damage

The Laser Damage and Conditioning Group at LLNL is evaluating diagnostics which will help make damage testing more efficient and reduce the risk of damage during laser conditioning. The work to date has focused on photoacoustic and scattered light measurements on 1064-nm wavelength Hf@/Si02 multilayer mirror and polarizer coatings. Both the acoustic and scatter diagnostics have resolved 10 pm diameter damage points in these coatings. Using a scanning stage, the scatter diagnostic can map both intrinsic and laser-induced scatter. Damage threshold measurements obtained using scatter diagnostics compare within experimental error with those measured using lOOx Nomarski microscopy. Scatter signals measured during laser conditioning can be used to detect damage related to nodular defects.