Submicrometer-wide amorphous and polycrystalline anatase TiO2 waveguides for microphotonic devices

We demonstrate amorphous and polycrystalline anatase TiO2 thin films and submicrometer-wide waveguides with promising optical properties for microphotonic devices. We deposit both amorphous and polycrystalline anatase TiO2 using reactive sputtering and define waveguides using electron-beam lithography and reactive ion etching. For the amorphous TiO2, we obtain propagation losses of 0.12 +/- 0.02 dB/mm at 633 nm and 0.04 +/- 0.01 dB/mm at 1550 nm in thin films and 2.6 +/- 0.5 dB/mm at 633 nm and 0.4 +/- 0.2 dB/mm at 1550 nm in waveguides. Using single-mode amorphous TiO2 waveguides, we characterize microphotonic features including microbends and optical couplers. We show transmission of 780-nm light through microbends having radii down to 2 mu m and variable signal splitting in microphotonic couplers with coupling lengths of 10 mu m. (C) 2012 Optical Society of America