Effects of thermal annealing on the optical characteristics of k -na + waveguides

We present a systematic study of the changes induced in the refractive-index profile of different sets of K -Na + ion-exchanged waveguides on soda-lime and BK7 substrates because of thermal annealing in the presence or absence of salt vapors. The concentration of potassium is recovered by secondary ion mass spectrometry, and the propagation losses are measured by means of the three-prism configuration.