Green luminescence in silica glass: A possible indicator of subsurface fracture

Abstract : We investigate the nature of defects triggering laser damage in fused silica in subsurface fractures in nanosecond near ultraviolet regime. Mechanical, laser induced surface flaws as well as pristine silica surface were characterized by optical microscopy and luminescence confocal microscopy before and after acid etching. In all cases, photoluminescence decreases with etching time assessing the existence of defects close to the surface. Spectral analysis of the evolution of these signals during etching allows new interpretations of the nature of precursors inducing damage. Green luminescence around 2.25 eV is seen as a potential subsurface fracture indicator leading to laser damage.