Effect of gamma irradiation on the optical spectra of undoped, Mg-doped, and Gd-doped LiNbO3 single crystals

We have measured the optical spectra of gamma-irradiated lithium niobate crystals of different compositions: nominally undoped and doped with rare-earth (Gd) and alkaline-earth (Mg) metals in the range 0.003-0.27 wt %. The difference in behavior between gamma-irradiated and vacuum-annealed nominally undoped lithium niobate single crystals has made it possible to elucidate the mechanisms underlying the formation of electronic and point defects in the crystals and to develop a model for the processes involved. The effects of gamma dose, doping level, and the nature of the dopant on the optical absorption of gamma-irradiated doped lithium niobate single crystals are analyzed.