Correlation between the 2.7 eV and 4.3 eV photoluminescence bands in silica glass

Our previous studies have reported the excitation energy dependence of the 2.7 and 4.3 eV photoluminescence (PL) bands in oxygen deficient silica glass at low temperature (～20 K). An oxygen vacancy (O₃SiSiO₃) was thought to be the origin of the two PL bands. In order to verify the origin of the 2.7 and 4.3 eV PL bands in silica glass, we measured the PL band of various thermally heat treated silica glasses. In the sample after heat treatment, we did not observe the 4.3 eV PL band, though we did observe the 2.7 eV PL band. These results suggest that these two PL bands do not have a common origin.