Thermally stabilized photoinduced Bragg gratings

Bragg gratings were printed in Ge–SiO2 and Ge–B–SiO2 thin glass films by KrF excimer laser irradiation through a phase mask. The diffraction efficiency of the grating printed in the Ge–B–SiO2 film was approximately one order of magnitude greater than that of the Ge–SiO2 film. Although the gratings were almost erased upon annealing at temperatures lower than 500 °C, a grating with much higher diffraction efficiency than before annealing was formed exclusively in the Ge–B–SiO2 film after annealing at 600 °C. The diffraction efficiency of the grating was unchanged upon repeated heating between room temperature and 600 °C.