ABSTRACT
This chapter describes an additional optical phenomenon related to the photochromic effect, or more precisely, to glasses that contain a thermally developed Ag halide phase. This photoadaption was initially observed when certain photochromic glass compositions that were exposed to ultraviolet (UV) light and then exposed to light of a wavelength that was within the UV-induced absorption band resulted in a color modification. The exposure of such glasses to ultraviolet light causes a broad absorption to develop through the visible wavelength range. The photo-induced optical anisotropy is produced in the glasses by exposing ultraviolet-darkened glass to visible light. The glasses in which a dichroic state is induced by the polarized optical bleaching process would remain dichroic as long as they were in a darkened state. Glass in a polarized state was left to fade to apparent clarity and then redarkened with UV light alone, and the prior polarization state is recovered.
