Thin Film Crystallinity and Substrate Materials in Atomic Graphoepitaxy of YBa2\text{}_{2}Cu3\text{}_{3}Ox\text{}_{x}

The complexity of a-/c-axis oriented growth of YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{x}$ thin films is reviewed from the viewpoint of controlling a-axis preferred thin film growth. Perfectly c-axis in-plane-aligned a-axis oriented YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{x}$ thin films, or "pure" a-axis oriented films, can be grown on the (100) face of tetragonal K$\text{}_{2}$NiF$\text{}_{4}$-type substrates by template growth process. A new growth mechanism called atomic graphoepitaxy is presented as a growth model. Transmission electron microscopy reveals that the films on a (100) SrLaGaO$\text{}_{4}$ substrate consist of domains surrounded by anti-phase and stackingfault boundaries. This domain formation can be well explained by substrate surface irregularities inherent in the SrLaGaO$\text{}_{4}$ crystal. The formation of defects in microstructures in "pure" a-axis oriented YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{x}$ thin films is also modeled based on our atomic graphoepitaxial growth model

KTN-crystal-waveguide-based electro-optic phase modulator with high performance index

An electro-optic (EO) phase modulator with a low driving voltage that uses newly developed KTa1-xNbxO3 buried waveguides is described. The waveguide layers for the core and cladding were formed using liquid phase epitaxy techniques. The propagation loss was less than 0.5 dB/cm and the polarisation-dependent loss was less than 0.1 dB/cm. The EO phase modulator had a low Vp×L value o