Fig. 1. Absorption spectra of silica glass with different hydroxyl concentrations before and after laser irradiation. The inset is an enlarged view of short dash line (except green dot line)

Fig. 2. Emission spectra of pure silica glass with different hydroxyl concentrations after irradiation, and the excitation wavelength is 248 nm

Fig. 3. Emission spectra of pure silica glass with different hydroxyl concentrations, and the excitation wavelength is 258 nm

Fig. 4. Fluorescence spectra at 650 nm center wavelength of pure silica glass with high hydroxyl concentration irradiated by ultraviolet lamp of 254 nm after femtosecond laser irradiation

Fig. 5. Fluorescence intensity variation at 650 nm centerwavelength of pure silica glass with high hydroxyl concentration irradiated by ultraviolet lamp of 254 nm with pulse duration after femtosecond laser irradiation, and the corresponding laser power is 9 mW

Fig. 6. Fluorescence intensity variation at 650 nm centerwavelength of pure silica glass with high hydroxyl concentration irradiated by ultraviolet lamp of 254 nm with laser power after femtosecond laser irradiation, and the corresponding pulse width is 253 fs

Fig. 7. Application of red fluorescence. (a) Red fluorescent two-dimensional code; (b) red fluorescent array