Theoretical analysis on the optical characteristics of pure and N-doped Ta2O5 2D photonic crystals with honeycomb lattice

Density functional theory (DFT) is performed on the structural and optical properties of undoped and N-doped Ta2O5. The optimized lattice constants of β-Ta2O5 are in good agreement with the experimental values. When O is replaced by N in Ta2O5, the substitutional doping of N in Ta2O5 clearly increases the refractive indices. The propagation of acoustic wave in two-dimensional (2D) photonic crystal of a honeycomb structure of air cylinder is investigated by the plane wave expansion method (PWEM). Our numerical results show that Ta2O5 has incomplete band gaps, indicating that only the TE mode appears. Ta2O4.5N0.5 is more suitable for background material. When a=338nm, r/a=0.46, and Δ=0.022 (ωa/2πc), a complete band gap appears in the red light range.