Doped Silica Glass Photosensitivity And Fiber Bragg Grating Devices Study

In the section 1 of this thesis the brief history and main results on the photosensitivity of glasses were briefly reviewed. The elucidation of photosensitivity mechanisms in Ge-doped silica glasses and the various views about the photosensitivity of Sn-doped silica glasses were highlighted. The properties, fabricating techniques and sensing applications of FBG were described as well.This thesis focused on the photo-induced refractive index changes and the mechanism of photosensitivity in Sn-doped silica glasses, sensing characteristics of Hi-Bi fiber Bragg gratings as well as the optical devices basing on 1053 nm FBGIt is the first time to our knowledge that 10.5 urn thick Sn-doped silica films were produced on a pure silica plate by MCVD followed by solution-doping method, in which a positive UV-induced refractive index change of 2×10-4 at 1550nm was observed using a novel method based on Fresnel formulae. The measured UV absorption and Raman spectra under different irradiating conditions indicate that the photosensitivity of the Sn-doped silica film depends on the energy density. Under high energy density (about 50mJ/cm2, 266 nm) irradiation, photosensitivity should be mainly originates from the microscopic structural modifications starting from bond-breaking of oxygen deficient defects (Sn-ODCs, Si-ODCs, and Si-E'). On the contrary, under low energy density (about 10mJ/cm2, 266 nm) irradiation, photo-conversion of optically active defects should play an important role in the generation of photosensitivity, and the mechanism of photosensitivity can be explained by Kramers-Kronig relationship. Apart from the well-known E'-Sn center responsible for 212 nm absorption band, two color centers with absorption at 194 nm and 263 nm appear while the 256 nm band due to Sn-ODCs is bleached by low energy density UV irradiation.It is the first time also to our knowledge that Yb doped tin-silicate optical fiber were produced by MCVD followed by solution-doping method, in which the peculiar photosensitivity of Sn-doped silica and the gain property of Yb-doped silica are both preserved. The recorded photo luminescence spectra (under 978 nm laser diode pumping) suggested that UV irradiation almost do no influence on its gain property when a positive UV-induced refractive index change of 2×10-4 was observed. The measured UV absorption indicates that the photosensitivity of the fiber depends on the energy density of UV laser pulses, which is similar to that in the Sn-doped silica films mentioned above. Under high energy density irradiation, photosensitivity should be mainly originates from the microscopic structural modifications starting from bond-breaking of ODCs. On the contrary, under low energy density irradiation, photo-conversion of optically active defects should...