Optical properties of LiNbO3 with ion implantation and titanium thermal diffusion

The optical properties of LiNbO₃ single crystal with ion implantation and thermal diffusion of titanium are studied. The separate and combined effects of the two processes are compared. A titanium film was prepared on LiNbO₃ by the conventional sputtering technique and CVD (chemical vapor deposition). Thermal diffusion was achieved by annealing in a dry oxygen atmosphere at various temperatures. For a Ti film with a thickness of 20 nm, five hours are needed for complete in-diffusion. The refractive index of LiNbO₃ with in-diffused Ti can vary from 10% (12%) to 8% (10%) for N_o (N_e). The thicker the Ti film on the sample, the smaller is the light loss. An isotropic refractive index can be obtained for an Ne-implanted LiNbO₃ sample. Negative birefringence and low light loss can be achieved on samples treated by Ti thermal diffusion combined with successive Ar implantation, which is very useful for waveguide applications