Photosensitive GeO 2 =SiO 2 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 Ge^2 + 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 Ge^2 + defect in origin. The channel waveguide and the planar Bragg gratings were directly written in the photoactive Ge^2 +-enriched GeO2 =SiO2 thin films by pulsed ultraviolet laser irradiation with a Cr-metalloaded-type waveguide structure.