Effects of layer thickness and number of interfaces on the damage threshold of ultra violet sol gel mirrors

Previous results(1) have shown that single layers of nitric or acetic acid stabilised zirconia and silica sol-gels have very high laser induced damage thresholds (LIDT). A significant decrease in the LIDT has been found when the materials are combined in layer pairs to form ultra violet mirrors. Investigations of possible causes of the lower LIDT will be reported. The effect of the coherent intensity enhancement at interfaces was tested by measuring the LIDT at 355nm on mirrors of different wavelength tuning. Three nine pair mirrors were used. These components are for use at 355nm and the first high reflector was specified at this wavelength. The other two components were made with high reflectivity at 300nm and 400nm and lower reflectivity at 355nm to check how the intensity of the internally reflected light would affect the LIDT.