Assessment of ion exchanged channel waveguides in glass using interference microscopy

The use of an interference microscope in the assessment of channel waveguides formed by ion exchange in glass is presented. In the particular mode of operation discussed, light is passed through the guide parallel to the surface normal to yield the lateral index profile. It is shown that the surface expansion of the glass that occurs during the exchange has a significant effect on the interference data. A simple method of correcting for this effect is reported and justified. The application of the above technique to the characterisation of Cu ion exchanged channel guides is demonstrated. Some observations concerning the relationship between the index profile and surface expansion profile are made.