Evaluation of UV absorption coefficient in laser-modified fused silica

Laser-induced damage in transparent dielectrics leads to the formation of laser-modified material as a result of exposure to extreme localized temperatures and pressures. In this work, an infrared thermal imaging system in combination with a fluorescence microscope is used to map the dynamics of the local surface temperature and fluorescence intensity under cw, UV excitation of laser-modified fused silica within a damage site. The energy deposited via linear absorption mechanisms and the absorption coefficient of the modified material are estimated based on a thermal diffusion model. In addition, irreversible changes in the absorption following extended laser exposure were observed.