DETERMINATION OF ION-EXCHANGED CHANNEL WAVE-GUIDE PROFILE PARAMETERS BY MODE-INDEX MEASUREMENTS

We report a method for characterizing ion-exchanged channel waveguides in terms of the diffusion depth, width, and surface-index change from mode-index measurements. The method is then used to study the effect of the diffusion time and the mask width on these parameters in K+-Na-exchanged guides in BK7 glass. It is observed that the mask width aff ects the waveguide dimensions in ways not reported in earlier studies. Our results reveal that the diffusion depth depends on the mask openi ng and saturates with time to a maximum value for a given mask width. The lateral-diffusion rate and the side diffusion beneath the mask. ar e independent of the mask width, which indicates that the lateral elec tric field associated with the metallic mask plays an important role i n such diffusion. We discuss the implications of this behavior to mode ling and fabricating integrated optical devices.