Effect of SiOH and SiCl on ArF-excimer laser-induced absorption in soot-remelted silica

Abstract

Characteristics of ArF-excimer laser-induced absorption in various types of fused silica synthesized by the vapor-phase axial deposition-soot remelting method were investigated. Fused silica containing 2−6×1018 cm−3 of OH and no Cl shows an absorption band at 5.8 eV ascribed to the E′ center (≡ Si ⋅) and an absorption band at 4.8 eV ascribed to oxygen related centers. A sample containing about 3×1019 cm−3 of Cl and no OH shows only the 5.8 eV band. An OH- and Cl-free silica had a preexisting absorption band at 5.0 eV ascribed to an oxygen deficient center (ODC; ≡ Si ⋅⋅⋅ Si ≡) and a weak band at 5.8 eV; the 5.0 eV band changed into a 5.8 eV band by irradiating it with the ArF laser. These phenomena can be interpreted as follows: typical silica glasses are considerably deformed from the ideal network and terminal groups such as Si–OH and Si–Cl reduce some amount of highly strained bonds in the glass network. In the sample containing a considerable amount of Cl and no OH, Si–Cl could be the major precursor of the E′ center because only a weak 5.8 eV band is observed. In silica containing a relatively small amount of OH and no Cl, bond breakage is the major process by which laser induced defects are produced.