Charge transfer and the photosensitivity in single- and double-doped LiNbO3 single crystals; an optical-electron paramagnetic resonance study: II

摘要

Abstract: Transition metals in particular increase the photorefractive sensitivity. We have reported in part I of the observed enhancement for the nonlinearity of these crystals due to the single and doubly dopants. In this part, we tried to answer some of the questions about the enhancement of the photorefractive sensitivity due to gamma irradiation. The crystals were irradiated by gamma ray and the EPR spectra were obtained. A new EPR center was observed at 3420G in Mn:Fe:LiNbO3 crystals. The Degenerate four wave mixing experiment was performed for these crystals and we have observed that the intensity of the PC signal from Ni:LiNbO3 crystal was increased by almost 30 percent. By applying the Ar$+$PLU$/ laser in situ the EPR signal was decreased and the center was bleached after almost nine minutes in the case of LiNbO3:Ni and four minutes in the case of LiNbO3:Fe:Mn crystal. An interpretation for this phenomenon will be given on the light of Kuktarev model. !12