Silica-titania planar waveguides were prepared via the sol-gel method from
acid-catalyzed solutions of firstly, y-Glycidoxypropyltrimethoxysilane mixe
d with tetrapropylorthotitanate (labeled as GT), and secondly, y-Glycidoxyp
ropyltrimethoxysilane mixed with both tetrapropylorthotitanate and tetraeth
oxysilane (labeled as GTT). Atomic force microscopy, thermal gravimetric an
alysis, differential thermal analysis, UV-visible spectroscopy, Fourier tra
nsform infrared spectroscopy, and Raman spectroscopy were used to study the
structural and optical properties of the waveguide films prepared from the
two types of sols. The obtained results showed that in both cases, crack-f
ree and highly transparent silica-titania films with a thickness of more th
an 0.5 mu m could be obtained by a single spin-coating process after a heat
treatment at 500 degrees C. The GT derived films showed more shrinkage and
a higher refractive index after annealing as compared to the GTT derived f
ilms. When such films were deposited on a silica-on-silicon substrate to ac
t as a surface planar waveguide, the light propagation loss was measured to
be about 0.9 dB/cm and 1.3 dB/cm respectively. Raman spectroscopy results
indicated that the GTT derived waveguide films with 0.5 molar titanium cont
ent contained amorphous carbon phase after being heated at above 500 degree
s C in air directly.