Effect of post treatment on the photorefractive properties of Ru-doped lithium niobate

The effect of post treatment on the photorefractive properties of Ru-doped lithium niobate was studied. The absorption spectra examination of Ru-doped LiNbO3 crystals with different post treatments showed that the absorption coefficient at 530 nm increased after the reduced treatment was employed and the absorption edge of the reduced crystal shifted towards the infrared band. On the contrary, the trend reversed after the oxidized treatment was employed. In addition, the photorefractive properties were investigated with the two-beam coupling method conducted via a 532 nm solid state laser. It was found that the oxidized Ru:LiNbO3 had smaller exponential gain coefficient and diffraction efficiency because the charges in the shallow level were exchanged to the deep level. On the other hand, the reduced Ru:LiNbO3 crystals had larger exponential gain coefficient and diffraction efficiency due to the increase of the Ru3+ which existed in the shallow level. The response times of both oxidized and reduced Ru:LiNbO3 were longer than those of the as-grown ones. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)