Electrically tunable optical filters based on barium strontium titanate for the telecom range

We report on the telecom-band implementation of a substrate-transferred Ba_0.8Sr_0.2TiO₃ (BST)-based electrooptically tunable Fabry-Perot band-pass filter and investigate the influence of electrodes solely on the top surface of the electro-optic layer versus lateral electrode configurations on the electric-field distribution within the active layer. Numerical simulations show that lateral electrodes increase the effective bias-field strength within the BST film by approximately 28%, as quantified by the average surface-integrated squared electric field over the optically active BST area. These results suggest that lateral electrodes can improve the electro-optic actuation efficiency of BST-based tunable filters in the telecom range.