Correlation between electro-optical coefficient and dielectric permittivity of BST thin films

A new measurement system of electro-optical (EO) effect and dielectric permittivity (?r) was developed to investigate the correlation between electro-optic and dielectric properties of epitaxial barium strontium titanate, Ba1-?Sr?TiO3 (BST) thin films grown on SrTiO3 (STO) substrates. The refractive index (birefringence) and the permittivity were measured as a function of DC-bias field applied using a planer electrode on the films. It was found that the tunability of birefringence was much lower than that of dielectric permittivity. The difference in the tunability was discussed from the view point polarization mechanisms.