Photosensitive GeO2-SiO2 films for ultraviolet laser writing of channel waveguides and bragg gratings with Cr-loaded waveguide structure

Irradiation with intense ultraviolet laser pulses induced a large refractive-index change in 30GeO2-70SiO2 waveguide-grade thin films prepared by the plasma-enhanced chemical vapor deposition method, which contained a large amount of photoactive Ge2+ defects. The maximum index change in the as-deposited films by KrF and XeF excimer laser irradiation was estimated to be 1.2 x 10(-3) and 0.28 x 10(-3), respectively. These results clearly indicate that the photorefractivity of GeO2-SiO2 glasses is due to a Ge2+ defect in origin. The channel waveguide and the planar Bragg gratings were directly written in the photoactive Ge(2+)-enriched GeOs-SiO2 thin films by pulsed ultraviolet laser irradiation with a Cr-metal-loaded-type waveguide structure.