Abstract

Despite the many important potential applications for photorefractive BaTiO₃¹, the precise nature and the depth of the photorefractive trapping centers has yet to be positively identified. In one study², a correlation was noted between the iron concentration as measured with EPR, the photorefractive trap density determined by two-beam coupling versus grating wavevector measurements, and the optical absorption coefficient. This tentatively identified iron as the photorefractive center in commercially-grown, nominally undoped crystals. More recently, high photorefractive gains were reported in nominally iron-free BaTiO₃ crystals³, and evidence was presented^3,4 that, in purposely iron-doped crystals, the most common valence states for iron are Fe⁺³ and Fe⁺⁴.

© 1990 Optical Society of America