First-principles analysis of optical absorption edge in pure and fluorine-doped SiO2 glass

We have carried out a “band-resolved” analysis of the optical absorption spectra of pure and fluorine-doped SiO2 glass by using the first-principles method, where dominant orbitals involved in the absorption spectra can be analyzed. We found that heavily strained bonds in three-membered ring structures affect the fundamental absorption edge and that the heavy strain is released by opening a ring structure with fluorine doping.