Preparing optical thick films for planar waveguides with single spin-coating processes

With the help of methylcellulose, an organic binder, SiO2/TiO2/methylcellulose hybrid thick films were prepared by a sol–gel technique with single spin-coating processes. After annealing at 70 °C for an hour, 2.5-μm crack-free and dense organic–inorganic hybrid optical films with a refractive index of 1.537 were achieved. Optical losses of waveguides made up of these films and ordinary slide glass substrates are around 0.3 dB/cm at 650 nm. To characterize the novel hybrid material more and to predict its potential applications, films annealed from 70 to 800 °C were investigated by scanning electron microscopy, UV-VIS spectrophotometry, thermal gravimetric analysis, Fourier-transform infrared spectroscopy and X-ray diffraction.