Photonic crystal structures in titanium dioxide (TiO2) and their optimal design.

We propose photonic crystal (PhC) structures in titanium dioxide (TiO2) material which is suitable for micro-nano structure optical device engineering and is a good candidate for visible light application. To provide a guideline for designing TiO2 based PhC, the comprehensive optical band gap maps of both the two-dimensional and three-dimensional structures are computed using the planewave expansion method. For 2D structures, besides the ideal infinite high 2D PhC and conventional air-bridge type slab, we also propose a "sandwich-type" PhC for better robustness and easier fabrication. The optimal thicknesses of both types of PhC slabs are investigated. In 3D PhC, we calculate the Yablonovite structure and its reverse which are made possible recently in our fabrication. For the first time to our knowledge, the computation results indicate that the reversed Yablonovite structure also shows a complete band gap characteristic, although it is smaller compared to that of the normal Yablonovite. The dependence of band gap width on the filling ratio and drilling angles for both types of Yablonovite structures are investigated.