Influence of impurity iron ions on nonlinear coloration of alkali-silicate glasses

A study was made of the role of iron impurity ions in the formation and decay of colour centres in alkali-silicate glasses in the course of multiphoton absorption of laser radiation. An increase in the concentration of Fe₂O₃ enhanced the residual absorption by stable hole colour centres and reduced considerably the lifetime of unstable electron colour centres. Repeated irradiation of glasses containing a small amount of the impurity increased the residual absorption, whereas the induced absorption (measured immediately after the action of a radiation pulse) did not change from one pulse to the next and was governed solely by the radiation power density. An increase in the Fe₂O₃ concentration destroyed this effect.