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

UV photosensitivity of Ge-doped silica films deposited on Si (100) 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 H-2-unloaded and a loaded film with fluency of 190 mJ/cm(2)/pulse at 10 Hz to KrF excimer laser induced a relative value of the refractive index change of 5.46 x 10(-4) and 2.94 x 10(-3) at 1550 nm, respectively. Optical absorption and PL spectra of our FHD H-2-loaded sample demonstrate that Ge2+ center (constituting GeO defect) was produced by a reaction of the germanosilicate glasses with the H-2 molecule, which could lead the higher UV-induced refractive index change after irradiation. Therefore, H, loading is sufficient to significantly increase the photosensitivity of Ge-doped SiO2 film to 248 nm light. (c) 2005 Elsevier B.V. All rights reserved.