Radioluminescence of silver halide optical fibers

The radioluminescence of mixed Ag halide optical fibers (AgCl_xBr_1-x, where 0 < x < 1) is investigated in the range 20-200°C. The main feature in the emission spectrum of the Cl-rich fibers is a broad band centered at 520 nm, which behaves as exp(E/kT), with E ≈0.06 eV. It indicates a competition between nonradiative processes and radiative recombinations of electrons with self-trapped holes. In the Br-rich samples the emission is mainly in the 600-700-nm range and is ascribed to holes trapped at Ag vacancies near divalent and trivalent cationic impurities. An intense new band in the infrared appears in some of the Cl-rich fibers and in all the Br-rich fibers following annealing at 250°C. It is ascribed to the migration of cationic impurities, or of the Ag vacancies that charge compensate them, and to the formation of new complex point defects.