Optic-axis and voltage-controlled polarization splitting and tunability in BaTiO3 defect-based 1D photonic crystals for filtering applications

In the present work, we investigate the interplay between the coupling and decoupling between the co-polarized and cross-polarized TE/TM modes under the influence of applied voltage and optic axis orientation in anisotropic uniaxial 1D photonic crystals. The proposed structure comprises silicon dioxide and titanium dioxide as the periodic layers and barium titanate as the defect material. This theoretical work demonstrates that polarized TE input light splits into TE and TM output light, and similarly polarized TM light splits into TM and TE light at certain optic axis angles. The voltage applied across the defect affects the coupling and compensates for the effect of the optic axis angle on the mode splitting. Furthermore, the applied voltage introduces tunability in the TM modes, whereas the incident angle provides tunability for all the modes. At the optic axis angle of 45°, the splitting modes have symmetry in their transmission. When the voltage is applied to 40 V or greater, the coupling modes diminish. We believe the present work strengthens the engineered applications of 1D photonic crystals for tunable and high-resolution filtering applications, with the possibility of extension to 2D and 3D photonic crystals.