Channel waveguides formed by ion implantation of PECVD grown silica

Low loss channel waveguides have been formed in silica-on-silicon by implantation with 5MeV Si and Ge ions. In these experiments, the substrate was comprised of an undoped layer of silica (30 mu m thick) which was grown by plasma enhanced chemical vapour deposition (PECVD). The optical loss characteristics of the waveguides, as measured at both lambda = 1300 and 1550nm, were independent of the implanted ion species. A minimum in the attenuation loss (alpha) of similar to 0.10-0.20dB/cm was obtained following both a pre-implant (1050 degrees C) and a post-implant (400-500 degrees C) anneal of the waveguides. The ability to produce a minimum in alpha by pre-implant annealing has been attributed to the thermally induced relaxation of the densified structure in the as-grown layer. Only a comparatively small degree of compaction was measured for Si-implanted samples which did not receive a pre-implant anneal. In contrast, the much larger degree of compaction in the pre-implant annealed samples was similar in magnitude to that observed in fused silica. These are the first reported examples of ion-implanted waveguides using a substrate of silica grown by PECVD.