Laser-induced damage threshold of nanoporous single-layer ALD antireflective coatings

Atomic layer deposition (ALD) enables coating complex shaped substrates with excellent uniformity along the surface of the optic. Recently developed nanoporous SiO2 layers have been applied as single layer antireflection coatings on fused silica substrates at both 1064 nm and 532 nm wavelengths. The LIDT in the nanosecond regime at both 1064 nm and 532 nm of these nanoporous SiO2 coatings as well as the bare substrates were investigated. The stability of the coatings with respect to LIDT has been evaluated under normal atmospheric conditions, dry air with relative humidity < 10% and nitrogen atmosphere. The multiple pulse damage characteristic for 5000 shots showed in all cases no significant pulse dependence. At 532 nm wavelength, the 0%-LIDT value is between 60 J/cm² and 70 J/cm², which is comparable to the values measured on uncoated substrates (80 J/cm²). In case of 1064 nm the 0%-LIDT is only between 40 J/cm² and 50 J/cm2 (uncoated substrate: 100 J/cm²) which is attributed to generated defects during the fabrication process.