Published online by Cambridge University Press: 21 February 2011
This report clearly shows that the photodarkening effect in semiconductor-doped glasses comes from the color center formation of alkaline silicate glass. It also discusses the cause of response time shortening after darkening. It seems that fast and stable responses can be obtained with a specific alkaline metal composition, showing a change in the dielectric properties and also a drastic decrease in the ion conductivity based on the mixed-alkali effect. After-darkening phenomena, such as the absorption increase in all transparent region of the glass, the appearance of electron spin resonance (ESR) arising from the formation of glass color centers, and matrix glass changes observed with a field emission scanning electron microscope (FE-SEM), are distinctly shown.