Abstract

An absorption band centered at ~ 5eV in SiO₂:GeO₂ glasses is composed of two components, photobleachable and unbleachable ( by one photon process) components, and attributed the former and the latter to a neutral oxygen monovacancy ( NOMV ) coordinated with two Ge⁴⁺ ions and a Ge²⁺ ( this may be regarded as neutral oxygen divacancy, NODV ) coordinated with two oxygens, respectively. The NOMV is converted into a Ge E’ center by illumination with 5 eV light or with 488nm Ar laser light. On the other hand, NODV with a lone pair electron occupying the uppermost level emits an intense blue luminescence but does not change chemically with 5 ev-light (at least via one photon process ). Therefore, we consider that the presence of the NOMV is essential to emergence of index change by irradiation with488 Ar laser light. Concentrations of the NOMV and NODV and are 2xl0¹⁶ and 2x10¹⁸ cm^-3 in VAD-5GeO₂-95SiO₂ glasses ( as-delivered ) or 6x 10¹⁶ and 1 x 10¹⁸ cm^-3 in 10GeO₂-90SiO₂ glasses, respectively.

© 1997 Optical Society of America