A SECONDARY-ION-MASS SPECTROMETRY STUDY OF MAGNESIUM DIFFUSION IN LITHIUM-NIOBATE

A detailed study of magnesium indiffusion in lithium niobate (LiNbO 3) crystal is presented. The aim of the work was to obtain a comprehensive understanding of the diffusion process as a function of film thickness, temperature, diffusion time, crystal cut-direction. The secondary-ion-mass spectrometry technique was employed to obtain magnesium concentration depth profiles. Our results show that the strongest factor that controls the diffusion process is the temperature. A noticeable increase of the diffusion coefficient is observed with increasing temperature. The diffusion time has a small effect on the diffusion coefficient, but if the former is less than a certain value, the deposited MgO film does not diffuse completely. On the other hand, if it is quite long it will enter into the annealing regime. Diffusion parameters to realize buried waveguides (which reduce the coupling loss between single-mode fibers and diffused waveguides) have also been derived. The present studies could be important in consideration of the synthesis of LiNbO3 optical devices with improved optical qualities. © 1994 American Institute of Physics.