Photorefractive properties of strontium barium niobate

Photorefractive materials have been used to demonstrate a variety of nonlinear optical applications, due to their large optical nonlinearity even with weak optical beams. To date, most photorefractive devices have used barium titanate (Ba-TiO3) because it is commercially available and it has a large Pockels coefficient (r42 = 820 × 10−12 m/V). However, it is difficult to obtain single crystals of BaTiO3 with dimensions larger than (5 mm)3. Photorefractive strontium barium niobate (SrjBat-xNbaOe or SBN) single crystals have been grown with larger dimensions (20 mm)3, and SBN also has a large Pockels coefficient (r33 = 420 × 10−12 m/V). Additionally, the tungsten-bronze structure of SBN has a large number of vacant lattice sites which could potentially be occupied by dopants to provide a high density of optically active impurity states. Such impurities are a prerequisite for an optically induced nonlinearity by the photorefractive effect.