UV-Radiation Induced Color Centers in Optical Fibers

ABSTRACTParamagnetic color centers have been observed in germanium silicate and germanium phosphosilicate multimode optical fiber exposed to broadband ultraviolet light (2–5 eV). These centers are characterized by an ESR and optical absorption similar to 1 meV and 100 keV radiation induced defects and show an apparent saturation as the UV dose approaches 100 J/cm2. The UV induced ESR spectra are not identical to that induced by 60Co radiation however, similar Ge(2) and Ge(3) germanium defect signatures are apparent. For both compositions these centers are characterized by a rapidly increasing loss from 1.0 to 0.5 µm with an additional broad absorption peak at 1.5 µm for the phosphorus containing cores. We suggest that the UV induced optical absorptions for both compositions in the short wavelength range are due in part to the Ge(2) germanium substitutional sites and expect that the 1.5 µm absorption is due to the P1 phosphorus oxygen vacancy.

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Radiation-Induced-Defects Localization in Single-Mode Optical Fibers

Materials Science Forum ◽

10.4028/www.scientific.net/msf.480-481.329 ◽

2005 ◽

Vol 480-481 ◽

pp. 329-332 ◽

Cited By ~ 1

Author(s):

Sylvain Girard ◽

A. Boukenter ◽

Y. Ouerdane ◽

J.-P. Meunier

Keyword(s):

Optical Fibers ◽

Single Mode ◽

Wavelength Dependence ◽

Radiation Sensitivity ◽

Color Centers ◽

Strong Interactions ◽

Radiation Induced ◽

Different Color ◽

Induced Defects

We studied the defects at the origins of the permanent radiation-induced attenuation in four g-rays irradiated single-mode germanosilicate optical fibers (~1 MeV; 1.2 kGy; 0.3 Gy/s) in the spectral range 400 - 1700 nm. We determined the wavelength dependence of the following cladding codopant influences: germanium (0.3 %), phosphorus (0.3 %), fluorine (0.3 %) on the germanosilicate (13 %) fiber radiation responses. We identified some of the different color centers produced by g-rays and we evaluated their localization in the fiber cross-section through the determination of the radial distribution of the radiation-induced absorption at 633 nm. We also evidenced the strong interactions between these three codopants. In particular, our results showed that the properties of the phosphorus-related color centers, which mainly determine the fiber infrared radiation sensitivity, are strongly influenced by the germanium- and fluorine-codoping.

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Radiation-induced defects in montebrasite: An electron paramagnetic resonance study of O – hole and Ti3+ electron centers

American Mineralogist ◽

10.2138/am-2020-7168 ◽

2020 ◽

Vol 105 (7) ◽

pp. 1051-1059

Author(s):

José R. Toledo ◽

Raphaela de Oliveira ◽

Lorena N. Dias ◽

Mário L.C. Chaves ◽

Joachim Karfunkel ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Electron Irradiation ◽

Color Centers ◽

Hydroxyl Groups ◽

Γ Irradiation ◽

Paramagnetic Resonance ◽

Radiation Induced ◽

Induced Defects ◽

Electron Paramagnetic ◽

Hole Centers

Abstract Montebrasite is a lithium aluminum phosphate mineral with the chemical formula LiAlPO4(Fx,OH1–x) and considered a rare gemstone material when exhibiting good crystallinity. In general, montebrasite is colorless, sometimes pale yellow or pale blue. Many minerals that do not have colors contain hydroxyl ions in their crystal structures and can develop color centers after ionization or particle irradiation, examples of which are topaz, quartz, and tourmaline. The color centers in these minerals are often related to O− hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil, were investigated by electron paramagnetic resonance (EPR) for radiation-induced defects and color centers. Although γ irradiation (up to a total dose of 1 MGy) did not visibly modify color, a 10 MeV electron irradiation (80 MGy) induced a pale greenish-blue color. Using EPR, O− hole centers were identified in both γ- or electron-irradiated montebrasite samples showing superhyperfine interactions with two nearly equivalent 27Al nuclei. In addition, two different Ti3+ electron centers were also observed. From the γ irradiation dose dependency and thermal stability experiments, it is concluded that production of O− hole centers is limited by simultaneous creation of Ti3+ electron centers located between two equivalent hydroxyl groups. In contrast, the concentration of O− hole centers can be strongly increased by high-dose electron irradiation independent of the type of Ti3+ electron centers. From detailed analysis of the EPR angular rotation patterns, microscopic models for the O− hole and Ti3+ electron centers are presented, as well as their role in the formation of color centers discussed and compared to other minerals.

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