Morphology of UV laser initiated damage in fused silica

In order to systemically investigate the morphology and microstructure induced in fused silica by UV (355 nm) laser pulses at high fluence, a suite of microscopic tools have been used, such as Nomarski optics microscope,AFM and SEM. Two types of damage are observed on the input surface of fused silica, that is, micro-pits and star-like cracks with diameters of 0.8～2.5 μm and 1.0～5.5 μm, respectively. Correspondingly, there are three types of damage on the output surface, namely micro-pits,shell-like damage and craters with diameters of 0.48～1.33 μm,4～20 μm and 12～30 μm, respectively. By comparing morphology of fused silica and laser fluence, several assumptions have been given to understand the damage initiation mechanism,especially for 1 μm scale laser initialed damage.