γ-Ray-induced visible/infrared optical absorption bands in pure and F-doped silica-core fibers: are they due to self-trapped holes?

Two optical fibers with high-purity, low-OH/low-Cl silica-cores, one F-doped and one not, were subjected to γ irradiation at 77 K and studied by transmission optical spectroscopy as functions of dose rate, dose, optical bleaching, ambient-temperature thermal fading, and isochronal annealing. Fractal-kinetic formalisms were used to elucidate and extrapolate the growth and decay kinetics of the induced optical absorption bands. It is shown that the isochronal annealing behaviors of bands peaking near 660 and 760 nm correlate with previously published electron-spin-resonance and electrical manifestations of self-trapped holes in amorphous silicon dioxide.