Effect of F2 laser power on defect formation in high-purity SiO2 glass

Laser power dependence of defect formation in synthetic SiO2 glass by F2 laser irradiation was measured. Concentration of the E′ center dissociated from the strained Si–O–Si bond was almost proportional to the F2 laser power less than ∼10 mJ cm−2 pulse−1 (∼0.5 MW cm−2). However, it increased as nearly square of the F2 laser power above the threshold. Quantum yield of formation of the E′ center by two-photon absorption of F2 laser light was ∼3 orders of magnitude larger than that of the KrF or ArF laser light, and we suggest that two-step absorption of F2 laser photons via real intermediate states dominates the formation of the E′ center.