On the Temperature-Dependent Photorefractive Effects in BaTiO3

In a recent letter Rytz et al[1] reported results of two-wave mixing experiments performed on BaTiO3 crystals in the temperature range between 20° and 120°C. They observed a large decrease in the density of empty traps as well as a significant decrease in the response time at elevated temperatures. The physical mechanism for the observed effects was not well understood. In this paper we show that the temperature variation in the empty trap concentration is accounted for by secondary photorefractive centers and discuss the possible influence of these traps on the hole mobility.