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

摘要

Atomic layer deposition (ALD) enables coating complex shaped substrates with excellent uniformity along the surfaceof the optic. Recently developed nanoporous SiO_2 layers have been applied as single layer antireflection coatings onfused silica substrates at both 1064 nm and 532 nm wavelengths. The LIDT in the nanosecond regime at both 1064 nmand 532 nm of these nanoporous SiO_2 coatings as well as the bare substrates were investigated. The stability of thecoatings 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 nosignificant pulse dependence. At 532 nm wavelength, the 0%-LIDT value is between 60 J/cm~2 and 70 J/cm~2, which iscomparable to the values measured on uncoated substrates (80 J/cm~2). In case of 1064 nm the 0%-LIDT is only between40 J/cm~2 and 50 J/cm~2 (uncoated substrate: 100 J/cm~2) which is attributed to generated defects during the fabricationprocess.