Effect of titania content on the optical properties of dye-doped hybrid sol–gel coatings

Sol–gel waveguides have been realized using a mixture of zirconium and titanium alkoxides with 3-Glycidoxypropyltrimethoxysilane (Glymo) as organic modifier. The molar ratio metal (Ti,Zr)/Glymo was 70/30 in order to obtain a material with high refractive index. Coumarin30 dye was added into the matrix during the synthesis with a concentration 2 × 10−2 M. Optical properties have been investigated by spectroscopic ellipsometry and UV–visible absorption measurements. Crack free 600 nm thick coatings were obtained with refractive index in the range 1.56–1.66, increasing with the Ti-content. Steady-state and time-resolved fluorescence measurements evidenced an almost linear decrease of the Coumarin30 fluorescence efficiency as Ti-content increases. Such a behaviour can be related to an excited state quenching mechanism. (Zr0.5–Ti0.5)70/Glymo30 coating could be considered a fair trade-off between waveguiding performance (n = 1.61; 3.2 dB/cm) and Coumarin30 fluorescence efficiency.