Fabrication of periodic Ti:LiNbO₃ waveguides by single and double diffusion

Periodic index waveguides have been successfully fabricated by diffusing a 200-Å-thick titanium film containing a grating pattern into Y-cut LiNbO₃ substrates. Bragg deflectors with efficiencies of up to 64% have been demonstrated in devices having a grating length of 750 μm and a diffusion time of 3 h. Similar devices have also been fabricated using a double-diffusion process to obtain high grating efficiencies in deeper waveguide layers. A deflection efficiency of 60% has been measured for a device having a total diffusion time of 11 h. While the diffusion of Ti gratings also leads to the formation of a surface corrugation on the waveguides, no increase in random scattering has been observed in the periodic region. The novel method of double diffusion could prove very useful in future integration of optical devices on a single LiNbO₃ substrate.