Abstract

Of trivalent rare-earth dopants only Ce³⁺ has been directly implicated in the photorefractive effect in SBN (Sr_xBa_(1−x)Nb₂O₆).^1,2 This is expected because Ce³⁺ is the most easily photoionized trivalent rare-earth. We have investigated the spectroscopy and photorefractive response of SBN doped with Ce³⁺, Pr³⁺ and Nd³⁺. Ce³⁺ shows a broad absorption extending from the band edge at about 3.2 eV (380 nm) to around 600 nm. This is assigned to a combination of 4f-5d and charge transfer absorption. In contrast, the spectrum of Pr³⁺ and Nd³⁺ consists of a number of sharp f-f absorption lines, together with a weak background, which may be due to other impurities or defects. In addition these ions have metastable excited states with lifetimes of about 100 µs.

© 1996 Optical Society of America