Secondary ion mass spectrometry and optical characterization of ion exchanged waveguides subjected to thermal annealing

In this paper, the experimental investigation of the effect of thermal annealing on the optical characteristics of Na/sup +/-K/sup +/ ion exchanged BK7 glass waveguides is reported. We have observed that the process of thermal annealing causes a variation of the refractive index profile from complementary error function to Gaussian shape already after a few annealing hours. The change is more stringent in the waveguides diffused for 5 and 10 hours and subjected to subsequent annealing. In these cases the refractive index profile exhibits a step-like change which adds to the Gaussian variation.