Fabrication and ultraviolet photosensitivity of Ge-doped silica films using FHD for optical waveguide

UV photosensitivity of Ge-doped silica films deposited on Si (1 0 0) substrates using flame hydrolysis deposition (FHD) has been investigated. The ratio of Ge and Si of the sample was estimated by XPS as 10:90, and it was shown by AFM as smooth and homogeneous. It seems to have not germanium oxygen deficiency centers which play a role in the change in refractive index after UV irradiation. The irradiation of a H2-unloaded and a loaded film with fluency of 190 mJ/cm2/pulse at 10 Hz to KrF excimer laser induced a relative value of the refractive index change of 5.46×10−4 and 2.94×10−3 at 1550 nm, respectively. Optical absorption and PL spectra of our FHD H2-loaded sample demonstrate that Ge2+ center (constituting GeO defect) was produced by a reaction of the germanosilicate glasses with the H2 molecule, which could lead the higher UV-induced refractive index change after irradiation. Therefore, H2 loading is sufficient to significantly increase the photosensitivity of Ge-doped SiO2 film to 248 nm light.