Transversal observation of the light-induced color-center concentration in photochromic glasses in stationary state

The aim of the present work is to study the dependence of the light-induced optical density, i.e., the color-center concentration, as a function of the distance traveled inside a photochromic glass body in stationary state. We propose an experimental setup that allows the direct observation of that concentration from a transversal view. In particular, we will see that for activating intensities much higher than certain threshold, the photochromic material saturates between the surface and an inflection point that happens at a constant normalized concentration of 2/3. The width of this region depends logarithmically on the activating light intensity. This fact will allow us to determine one of the photochemical constants of the material. Validation experiments are presented.