Open AccessPhotochemical process of divalent germanium responsible for photorefractive index change in GeO2-SiO2 glasses
Author(s) -
Akifumi Sakoh,
Masahide Takahashi,
Toshinobu Yoko,
Junji Nishii,
Hiroaki Nishiyama,
Isamu Miyamoto
Publication year - 2003
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.11.002679
Subject(s) - photorefractive effect , germanium , materials science , ultraviolet , excitation , singlet state , divalent , photoluminescence , photochemistry , refractive index , germanium compounds , optoelectronics , optics , silicon , atomic physics , chemistry , physics , excited state , quantum mechanics , metallurgy
The photoluminescence spectra of the divalent Ge (Ge2+) center in GeO2-SiO2 glasses with different photosensitivities were investigated by means of excitation-emission energy mapping. The ultraviolet light induced photorefractivity has been correlated with the local structure around the Ge2+ centers. The glasses with a larger photorefractivity tended to exhibit a greater band broadening of the singlet-singlet transition on the higher excitation energy side accompanied by an increase in the Stokes shifts. This strongly suggests the existence of highly photosensitive Ge2+ centers with higher excitation energies. It is also found that the introduction of a hydroxyl group or boron species in GeO2-SiO2 glasses under appropriate conditions modifies the local environment of Ge2+ leading to an enhanced photorefractivity.