Optical absorption and luminescence of germanium oxygen-deficient centers in densified germanosilicate glass.

Spectroscopic properties of germanium oxygen-deficient centers were studied in vapor axial deposition and modified chemical-vapor deposition germanosilicate glass after hydrostatic densification by as much as 19%. Gaussian decomposition showed a broadening and a significant shift of the initial absorption bands at 5.11 and 5.42 eV. A threefold decrease of the 3.15-eV luminescence band was revealed, whereas the 4.25-eV luminescence band was only slightly sensitive to densification. This shows that these two bands belong to different luminescence centers. A drastic growth of a new metastable absorption band near 7.3 eV was observed. The pressure-induced changes disappeared as a result of thermal annealing. These changes are discussed with respect to in-fiber grating phenomena.