Gamma-Ray Induced Absorption Band at 770 nm in Pure Silica Core Optical Fibers

Abstract

The effects of the drawing conditions, OH content and irradiation temperature on radiation-induced optical absorption bands in step-index fibers with pure silica cores clad with silicone or F-doped silica have been investigated. A loss peak was induced at 770 nm in silicone-clad fibers with both low and high OH-content silica cores, but the loss peak occurred at 630 nm in F-doped silica-clad fibers under γ-ray irradiation. The drawing conditions affected the growth of the loss peak in both silicone-clad and F-doped silica-clad fibers. The 770 nm band decreased under γ-ray irradiation exceeding 100 Gy at room temperature but did not decrease at 77 K. Radiation hardening was produced in the 770 nm band by γ-ray irradiation at room temperature or by room temperature annealing after irradiation at 77 K. The loss peaks at 770 nm and 630 nm in the two kinds of fiber are discussed in relation to the differences in the cladding materials.

Self-trapped holes in pure-silica glass: A history of their discovery and characterization and an example of their critical significance to industry

“…Their decay data for the dominant 760 nm band, as well as their fractal-kinetic fits of these data, in the range 0.1-600 s are in harmony with my own isothermal decay data for similar fibers measured at the same wavelength, and my fractal-kinetic fits of these, in the range 60-8000 s following c irradiation (dose 8.4 · 10 4 Gy, dose rate 1 Gy/s) [63]. But Sylvain's new data are the first I have seen since those published by Kaya Nagasawa [31,32] that show the 760 nm band to be more intense than its companion at 660 nm. The common element here would seem to be the low doses employed in these very different experiments ($20-300 Gy in [31,32] versus $2 Gy in [83]) and certainly not the dose rates (0.02-0.07 Gy/s [31,32] versus >1 MGy/s [83]).…”

“…But Sylvain's new data are the first I have seen since those published by Kaya Nagasawa [31,32] that show the 760 nm band to be more intense than its companion at 660 nm. The common element here would seem to be the low doses employed in these very different experiments ($20-300 Gy in [31,32] versus $2 Gy in [83]) and certainly not the dose rates (0.02-0.07 Gy/s [31,32] versus >1 MGy/s [83]). We therefore have a strong hint that the relative peak absorptions of the 660 and 760 nm bands in comparable low-OH/ low-Cl fibers may be independent of dose rate even at room temperature.…”

“…2 are publications by Kaya Nagasawa and coworkers [31,32] and by me [33], which do not treat Chernov et al's weak 1800-nm optical absorption band, but rather concern much stronger c-ray-induced optical bands at 660 and 760 nm. In their ground-breaking pair of papers, Nagasawa et al [31,32] characterized these bands in considerable detail but tentatively ascribed them to unidentified impurities.…”

A Minireview of the Natures of Radiation-Induced Point Defects in Pure and Doped Silica Glasses and Their Visible/Near-IR Absorption Bands, with Emphasis on Self-Trapped Holes and How They Can Be Controlled

“…Due to this redirection, I found no opportunity to look for optical manifestations of STHs in bulk silicas. Indeed, I had nearly forgotten about STHs when five years later I began to think that the intense absorption bands at 660 and 760 nm (originally reported by Nagasawa and coworkers [42,43]) that leaped up in my aluminum-jacketed low-OH pure-silicacore and F-doped-silica-core test fibers immediately upon inserting the sample coils into the NRL "swimming pool" -ray source might be due to STHs [44,45].…”