Ferroelectric thin film photonic crystal waveguide and its electro-optic properties

The electro-optical properties of a tunable photonic crystal (PhC) thin film waveguide structure are simulated using a 2D finite difference time domain (FDTD) method. For a 2D PhC consisting of a square lattice array, the dependence of the bandgap on the air hole radius, lattice constant and filling factor are calculated. For the simulation ferroelectric barium titanate (BTO) PhC is chosen as the nonlinear medium. The calculated spectral range of the PhC waveguide is 187-207THz with a bandwidth of 20THz. A tunable superlattice PhC wide band filter was designed and its properties simulated. The passband center frequency decreases linearly with applied voltage over the frequency range of 187-194THz. Due to the large electro-optic coefficient of BTO, the calculated tunability df_c/dV is -0.18 THzV^-1. Simulation indicates that the proposed PhC superlattice structure has significant advantages over conventional devices including both a much reduced size (24 × 4νm²) and large tunability of the bandgap required for future medium scale photonic integrated circuits.