Fabrication of inorganic–organic hybrid films for optical waveguide

Inorganic–organic hybrid guiding and buffer layers for optical waveguides were synthesized by the sol–gel process. An acid-catalyzed solution of 3-(trimethoxysilyl)propylmethacrylate and tetraethylorthosilicate was used as a precursor to produce thick films by spin-coating. Incorporation of a UV-sensitive functional group leads to the fabrication of the photo-patternable guiding layer. High-resolution patterned films with 8 μm linewidth were obtained using a conventional photo-lithography. Furthermore, the amount of phenyltrimethoxysilane added as a refractive index modifier varied in order to control the refractive index of the underlying buffer layer. The refractive index variations and structural changes of these inorganic–organic hybrid films as a function of the processing conditions were analyzed using the prism coupling technique and a Fourier transform infrared spectrometer. We have produced optically transparent films at above 500 nm with a propagation loss of 0.84 and 1.49 dB/cm at 1310 and 1550 nm, respectively.