THERMAL ANNEALING OF K-NA+ ION-EXCHANGED WAVE-GUIDES()

The process of thermal annealing of K+-Na+ ion-exchanged waveguides in soda lime glass is characterized and compared with a simple theoretic al model. The discrepancies between theory and experiments in the case of initially thick guides disappear if the existence of a stress-indu ced contribution to the refractive index is assumed that is not propor tional to the concentration of the doping ions. The results obtained f or initially thin guides are exploited for the design of annealed sing le-mode channel waveguides: 0.4-dB coupling losses with commercial sin gle-mode fibers at lambda = 1.321 mu m were measured.