Ferroelectric tungsten bronze crystals and their photorefractive applications

The photorefractive properties of tungsten bronze ferroelectric crystals are reviewed with respect to host character and dopant. A classification into four groups is proposed for tungsten bronze materials based on their structural, ferroelectric and optical properties. The use of dopants is found to control the speed of response and coupling strength as well as spectral range. In particular, the availability of different crystallographic sites is shown to provide opportunities to separately adjust these properties. The best performance has been established for Ce 3+ and Cr 3+ doped SBN:60 crystals in the visible and IR regions, respectively.