Laser conditioning methods for hafnia silica multilayer high-reflective coatings

Single-step and multi-step laser conditioning methods for HfO2/SiO2 multilayer high-reflective (HR) coatings prepared by electron-beam evaporation were introduced, with the use of different beam increment between pulses. In order not to damage the coating, the maximum conditioning fluence can not exceed 90% of its unconditioned laser induced damage threshold (LIDT). The LIDT enhancement of the coating after single-step conditioning is more than that after multi-step conditioning under the same conditioning efficiency. After two-step laser conditioning with a beam increment between pulses equal to the beam diameter at 98.4% of the peak intensity, the LIDT of the coating attains 181% of that of the unconditioned coating. The starting material composition for the hafnia layers has a direct impact on the concentration of defects imbedded in the coating, it is believed that coatings deposited from hafnium have defect-seeds at a significantly lower density.