Abstract

For some classes of ion-exchanged waveguides in glass, the index increase that results from the exchange process is strongly influenced by the associated buildup of surface stresses. In particular, for potassium-sodium exchange in soda-lime glass, the index increase is almost entirely from stress, and the waveguide is birefringent. This suggests modifying the waveguiding properties by altering the state of stress, either permanently or temporarily. One of the most convenient ways of doing this is to supply controllable amounts of heat to local areas of the surface by means of CO₂ laser pulses, which are strongly absorbed in glass. Various experimental results are reported in which permanent and temporary modifications to optical waveguides are obtained with power densities as low as 0.38 W/cm². In particular, efficient modulation at kilohertz rates, annealing of surface scattering losses, and damage thresholds are reported.

© 1990 Optical Society of America