Two-Dimensional Ferroelectric Photonic Crystal Waveguides: Simulation, Fabrication, and Optical Characterization

The optical properties of two dimensional photonic crystal (PhC) waveguides were investigated using ferroelectric barium titanate (BTO) thin films as the optical medium. The photonic band structure was calculated using a 2-D finite difference time domain (FDTD) method; a broad band gap is observed that results from the high refractive index contrast. The simulated transmission spectra indicate the stop band of PhC is mainly determined by three parameters: lattice constant, refractive index contrast, and waveguide mode order. From transmission measurements the PhC with a lattice constant a = 420 nm shows a strong light dispersion and the other PhC with a = 450 nm shows a 120-nm broad stop band. Strong localization of visible light within the PhC cavities is demonstrated from the light scattering images. The observed strong light confinement and its spatial intensity profile due to resonance agree with the calculated profiles. From polarized optical microscopy we discovered the scattered light wavelength was highly sensitive to magnitude of the lattice constant. The optical scattering properties indicate BTO PhC can potentially serve as micrometer size electro-optically tunable switches and color filters.