MEAN ORDERING IN GLASS STRUCTURE AS A BACKGROUND OF PHOTOSENSITIVITY IN SILICA FIBERS

摘要

x It seems there is no clearance in the local atomic-scale geometry and, consequently, physical nature of photosensitivity in silica networks up to now. Traditional spectroscopic techniques, such as electron absorption and luminescence permit one only to reveal some local disorder in glasses. Unfortunately, the structural studies based on infrared absorption and spontaneous Raman scattering are not effective in glasses due to overlapping of an extremely broadened vibrational bands. Low loss silica-based optical fibers are capable to guide light beams over long distances and confine them to a small cross-sectional area. These advantages of fibers are especially favorable for nonlinear optical spectroscopic studies owing to threshold nature of stimulated Raman scattering (SRS) by optical phonones in a glass core. Recently, some experimental SRS data concerned with vibrational states of native Raman-active centers and photoinduced defects in silica fibers, capable to second harmonic generation were published [1].