Long-pulse laser-induced damage in an optical anti-reflective film: II. Experimental research

In order to verify the result of theoretical analysis about long-pulse flat-topped multi-Gaussian laser-induced damage in an optical anti-reflection film with HfO₂/SiO₂ composite film coating on a BK7 substrate (BK7:HfO₂/SiO₂), an experimental system was built, which carried out the experiment and analysis, focusing on the pulse-length 1.0 ms, flat-topped laser-induced damage. The result shows that the thermal effect is the main reason for damage under the long-pulse flat-topped laser. Moreover, the stripping and shedding occur because of the heating stress of the film happening at an early stage of the laser irradiation. However, the crack happens at laser irradiation termination. The correctness of the theoretical analysis results is verified. (paper)