Integrated TiO2 resonators for visible photonics
  We demonstrate waveguide-coupled titanium dioxide (TiO2) racetrack resonators with loaded quality factors of 2x10^4 for the visible wavelengths. The structures were fabricated in sputtered TiO2 thin films on oxidized silicon substrates using standard top-down nanofabrication techniques, and passively probed in transmission measurements using a tunable red laser. Devices based on this material could serve as integrated optical elements as well as passive platforms for coupling to visible quantum emitters. 
Jennifer T. Choy, Jonathan D. B. Bradley, Parag B. Deotare, Ian B.   Burgess, Christopher C. Evans, Eric Mazur, and Marko Loncar
physics.optics