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A magnifying fiber element with an array of sub-wavelength Ge/ZnSe pixel waveguides for infrared imaging Appl. Phys. Lett. 101, 021108 (2012) Embedded calibration system for the DIII-D Langmuir probe analog fiber optic links Rev. Sci. Instrum. 83, 10D710 (2012) Analytical analysis of modulation instability in fiber optics AIP Advances 2, 022168 (2012) Atmospheric pressure dielectric barrier microplasmas inside hollow-core optical fibers Defect centers induced by ionizing radiation (50-100-keY x rays, 6OCo r rays) in high purity Pdoped silica glass have been observed and elucidated by ESR spectroscopy. Four generic species are well characterized on the basis of the observed 31p hyperfine splittings and g values as defects analogous to PO; -(phosphoryl), PO! -(phosphoranyl), PO~ -(phosphinyl), and PO! -radicals. The latter species, also termed the phosphorus-oxygen-hole center (POHC), is shown to occur in two variants comprising holes trapped on one or two nonbridging oxygens. Radiation-induced Si E ' centers with and without P next-nearest-neighbors were also identified, and a singlet resonance S due to E; type defects such as (OSi 2 )Si· and/or (02Si)Si. was observed to grow in with annealing above -800 K, regardless of whether or not the sample was irradiated. The structures, formation mechanisms, and precursors of these defects have been determined or inferred for all centers. Radiation-induced optical absorption spectra over the range 0.5-6.2 eY have been obtained for bulk glass and fiber samples after irradiation and following anneals to various temperatures up to 1250 K. Gaussian resolutions of the spectra into component bands have been performed and isochronal anneal data have been used to identify optical absorptions of the PO; -, PO! -, PO~ -, POHC, and S centers. The PO; -defect was found to absorb at -0.8 eY in the region of interest for fiber optic communication. Oscillator strengths are calculated for all bands.

A series of synthetic fused silicas of diverse OH contents was subjected to 100-keV x irradiations at 77 K and investigated by electron-spin-resonance techniques at -110 K or higher temperatures.Spectra were recorded at X-band frequencies (-9.2 -9.3 6Hz) both as the first derivative of absorption and in the high-power second-harmonic mode in order to bring out features not fully accessible by using one of these methods alone. In addition to the previously known E', E~, and oxygen-associated hole centers, three new defects were detected and characterized by computer lineshape simulation methods. These were atomic chlorine, a delocalized E' center (denoted Eq), and the first biradical to be reported in a-Si02. A sample-to-sample correlation of the radiation yields of these three new centers has been noted, leading to the suggestion that all three find their origins in specific chlorine-decorated precursor sites in the unirradiated glasses. Although significant chlorine impurities (& 100 ppm) may be ubiquitous in both type-III (high OH) and type-IV (low OH) fused silicas, the occurrence of chlorine-associated radiation-induced defects appears to be anticorrelated with the OH contents of the materials. Some possible technological implications of these findings are discussed.

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