Characteristics of laser-densified and conventionally heat treated sol–gel derived silica–titania films

Thin films of various compositions in the system SiO2–TiO2 were prepared by the sol–gel method, with the effects of laser-densification and heat treatment being studied. The etch rate of the resultant coating films was found to change by a factor of almost 1000 for various heat treatment conditions in the temperature range 600∼800°C. By combining laser sintering of selected areas and chemical etching techniques, the large difference between the etch rates of densified and undensified coatings can be used to produce channel waveguide structures. The etched coatings were characterized by X-ray diffraction, Fourier transform infrared spectra and micro-Raman spectra with these studies indicating that crystallization occurs in the region of laser scanning with dimensions corresponding approximately to the width of the beam used.