Electro-optical effect in BaTiO3 for tuning of narrow-band optical reflection filter

We present a numerical study of tuning properties of a narrow-band optical filter based on the electro-optical (E-O) effect in BaTiO₃ crystal layer. The filtering is due to the resonant waveguide mode excitation by using of subwavelength grating. In order to achieve polarization independence we introduce a structure having two-dimensional periodicity. Additional substructures inside each period are used in order to increase the angular tolerances of the filter. A peak reflection exceeding 90% within a spectral interval of 0.1 nm is obtained for the most optimal configuration. By taking into account the linear E-O (Pockels) effect only, the tuning range of 33 nm can be achieved for an applied external electric field that does not exceed 1.5×10⁷ V/m. This shift is multiplied by three (97 nm) when also taking into account the quadratic E-O effect.