Low optical loss nano-structured $$\mathrm{TiO }_{2}$$ TiO 2 planar waveguides by sol–gel route for photonic crystal applications

Abstract

Nano-structured \(\mathrm{TiO }_{2}\) planar waveguides were prepared by sol–gel route: titanium tetraisopropoxide was dissolved in isopropanol, and then hydrolyzed by adding a water/isopropanol mixture with a controlled hydrolysis ratio. The resulting sol was deposited by “dip-coating” on a glass substrate with a controlled withdrawal speed. The obtained films were annealed for 2 h at 350 and \(500\,^{\circ }\mathrm C \), respectively. The structural and morphological properties of the synthesized films were analyzed by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Optical properties such as refractive index, thickness, number of propagating modes, and attenuation coefficient were measured at 632.8 nm by m-lines spectroscopy as a function of the elaboration parameters. The films exhibit diffraction pattern consistent with an anatase phase and the \(\mathrm{TiO }_{2}\) planar waveguides are multimodes and demonstrate propagation losses as low as 0.3 dB/cm.