Correlation between compositional and refractive index profiles in LiNbO3 : Zn diffused optical waveguides

Waveguides fabrication in Z- and X-cut LiNbO3 crystals by vapor zinc diffus ion has been studied by secondary ion mass spectrometry and optical measure ments. Compositional analysis bf diffused substrates shows the formation of a Zn rich superficial layer, followed by a deeper region with decreasing Z n concentration. A subsequent thermal annealing process has been performed to let zinc ions further diffuse into the substrates. The composition profi les have been correlated with the refractive index profiles, reconstructed by optical reflectivity measurements. The results and the nature of the det ected layers are discussed and correlated with previous x-ray studies obtai ned in the same samples. (C) 2000 American Institute of Physics. [S0021-897 9(00)06819-5].