Power dependence of defect formation in SiO2 glass by F2 laser irradiation

The dependence of defect formation in a high-purity synthetic SiO2 glass on F2 laser power was studied. Above the threshold value of ∼10 mJ cm−2 pulse−1 (∼0.5 MW cm−2), the concentration of the laser-induced E′ center created by the dissociation of Si–O–Si bond increased as a function of the F2 laser power squared. The quantum yield of the E′ center formed by the high-power F2 laser irradiation was ∼3 orders of magnitude larger than that formed via two-photon absorption processes of KrF or ArF laser pulses. This strongly suggests that irradiating with the high-power F2 laser creates the E′ center via two-step absorption processes.