Sol-gel derived thin films of LiTaO₃ on SiO₂/Si substrates for optical waveguide applications

Thin films of lithium tantalate have been derived on SiO₂/Si substrate by sol-gel method. The sol is prepared by mixing LiOC₂H₅ and Ta(OC₂H₅)₅. The film is deposited by spin- coating and annealing at 600°C. The film is characterized by means of X-ray diffraction, atomic force microscopy, and the m-line technique. The experimental results show that the film has crystallized into the pure trigonal phase and it is microsopically continuous and uniform. The crystalline size ranges from about 33nm to 96nm. The refractive index of the film is measured to be 1.84 at the wavelength of 633nm and the film is found to support several guiding modes at this wavelength.