Artificial BaTiO3 - SrTiO3 superlattices with stacking periodicity varying between 27 and 1670 Å in separate films were grown on MgO substrates by pulsed laser deposition. Both the static and active optical properties were found to be sensitive on the stacking periodicity. Birefringence decreased with increasing individual layer thickness due to relaxation of the interface originated stress. The electro-optic response also showed a layer thickness dependence, reaching a maximum at an individual layer thickness of 13 unit cells.
Hiltunen, J., Lappalainen, J., Puustinen, J., Lantto, V., & Tuller, H. L. (2008). Size-dependent optical properties of BaTiO3 - SrTiO3 superlattices. Optics Express, 16(11), 8219 - 8228. https://doi.org/10.1364/OE.16.008219