Design of a tunable high Q photonic band edge cavity on ferroelectric Barium Titanate

A band edge cavity on ferroelectric Barium Titanate is proposed. The cavity is designed by inserting a Photonic Crystal (PhC) within another PhC, so that the band edge of the core PhC falls within the band-gap of the outer PhC, which supports the slow light modes of the inner PC. The PhCs are selected based on their band diagram which is calculated by Plane Wave Expansion (PWE) method. The spectral purity, spatial and time confinement of the cavity are then studied using Finite Domain Time Difference (FDTD) method. The frequency spectrum of the designed cavity is calculated from the time response of the cavity. At the resonant wavelengths, the field profile and quality factors (Q) are calculated. The dispersive and absorptive nature of BaTiO₃ is included in the calculation. It is found that the proposed cavity can sustain three high Q comparable modes. It has also been found that the tunability of the proposed band edge cavity is weaker compared to that of a photonic band-gap defect cavity.