DISLOCATION DISTRIBUTIONS IN ION-IMPLANTED OPTICAL WAVE-GUIDES

The origin of anomalous refractive index values in ion implanted optical waveguides in some crystalline materials has been an outstanding problem for several years. By use of complementary X-ray edge-topography and Raman microprobe imaging we have found evidence that changes in the dislocation density after implantation correlate with changes in the dynamic response of the lattice to light. This implies that the effects of reduced dislocation density may be related to the origin of the refractive index anomalies, possibly as a result of strain relief. Further support for this hypothesis comes from the fact that the original bulk dislocation density is recovered throughout the crystal by annealing to the temperature at which the refractive index anomalies are lost.