Origins of a damage-induced green photoluminescence band in fused silica revealed by time-resolved photoluminescence spectroscopy

Abstract

With combined lifetime and intensity spectra in time-resolved photoluminescence (PL) spectroscopy, the origins of a green PL band consisting of a 2.39eV-band with lifetime ~10μs and a 2.25eV-band with lifetime ~50μs, of high-purity fused silica under ArF excimer laser (6.4eV) excitation were revealed. The 2.39eV PL defects from the surface were annealed due to the deoxidation of the dioxasilyrane group ( = SiO2). The 2.25eV PL defects from bulk showed a UV induced growth. Mechanical and laser damage induced growth of the 2.25eV PL band confirmed that it was due to physical disorder from bending of Si-O-Si bonds. Theoretical calculations further assigned the 2.25eV PL band to silanone groups ( = Si = O), which can be created by relaxation process of strained Si-O bonds in SiO2 network.