Bismuth-doped hafnia-yttria-alumina-silica based fiber: spectral characterization in NIR to mid-IR

We report an experimental analysis of new hafnia-yttria-alumina-silica glass based fiber doped with bismuth (Bi), with absorption/fluorescence spectra along with resonant-absorption saturation, fluorescence lifetime, and gain, all adherent to Bi-related active centers (BACs), being measured at laser-diode excitation @ 908, 976, 1069, and 1120 nm, matching the NIR BACs' band. The found spectral laws reveal the optimal on excitation wavelength fluorescence, resonant-absorption bleaching, and gain capacities of the fiber, useful for applications at diode pumping. Besides, we report, for the first time to the best of our knowledge, a new resonant-absorption band of BACs in mid-IR (similar to 2.1 mu m) in the fiber, effectively bleached under the action of low-power in-band excitation, and provide the reasons for its association with co-doping the fiber with hafnium. (C) 2017 Optical Society of Americ

Effects of electron-irradiation darkening and its posterior bleaching by light in novel Cr-Mg-YAS fiber

Two remarkable effects for the recently invented chromium-magnesium (Cr-Mg) co-doped yttria-alumino-silicate fiber are reported: (i) strong and spectrally peculiar darkening under the action of energetic (6 MeV) beta-electrons with dosage up to 1.0 x 10(15) cm(-2) and (ii) posterior optical bleaching of the darkening loss at exposure to low-power (of a mW-range) 633 nm light. Both phenomena are revealed to be conspecific to co-doping the fiber with Mg and to the presence of versatile valence forms of Cr ions. The reported results seem to be impactful for exploiting fiber of such type for dosimetry and in space technology

Effect of electron irradiation on the optical properties of bismuth doped hafnia-yttria-alumina-silicate fiber

We report a study on transformations in absorption and emission spectra of novel bismuth (Bi) doped hafnia-yttria-alumina-silicate fiber, which arise as the result of bombardment by high-energy (beta) electrons. Among the featuring data obtained, we reveal substantial growth of `active' Bi center content in the fiber core-glass with increasing beta-irradiation dosage, resulting in dose-dependent intensification of the resonant-absorption bands and enhancement of the emissive potential of the fiber in near-IR, inherent to these centers. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Effects of elevating temperature and high-temperature annealing upon state-of-the-art of yttia-alumino-silicate fibers doped with Bismuth

We report an experimental analysis of attenuation and fluorescence (at low-power 750-nm excitation) spectra' transformations in yttria-alumino-silicate fiber doped with Bismuth (Bi), which occur at higher than room, but not exceeding 700 degrees C, temperatures. As well, we address impact of elevating temperature upon the fiber's basic characteristics, such as fluorescence/resonant-absorption saturation, fluorescence lifetime, and pump-light backscattering, given by the presence of Bi-Al related active centers (BACs). The experimental data reveals dramatic impact of heating and high-temperature annealing in excess of 500...550 degrees C on the fiber's state-of-the-art, expressed as significant rise of resonant absorption, enhancement of BACs NIR fluorescence, and reduction of scattering loss. In the meantime, such microscopic parameters of the fiber as BACs fluorescence lifetime and saturation power are found to be kept almost unchanged in its post-annealed state as compared to the pristine one. Possible mechanisms responsible for the phenomena and advantages of utilizing temperature-treated fiber of such type for lasing/amplifying purposes are discussed. (C) 2016 Optical Society of Americ

Upconversion assisted self-pulsing in a high-concentration erbium doped fiber laser

We report results on experimental and theoretical characterisation of self-pulsing in high concentration erbium doped fibre laser which is free from erbium clusters. Unlike previous models of self-pulsing accounting for pair-induced quenching (PIQ) on the clustered erbium ions, new model has been developed with accounting for statistical nature of the excitation migration and upconversion and resonance-like pumpto-signal intensity noise transfer. The obtained results are in a good agreement with the experimental data

Hafnia-yttria-alumina-silica based optical fibers with diminished mid-IR (> 2 mu m) loss

Fabrication details and basic characteristics of a set of novel multimode hafniayttria- alumina-silicate (HYAS) core-glass based fibers, one of which is co-doped with bismuth (Bi), for the mid-IR (> 2 mu m) spectral range are reported. It is demonstrated that fibers of this type possess low fundamental loss in the spectral range beyond 2 mu m, lowered by fewer times as compared to conventional silica-based ones, even at moderate (units of mol.%) co-doping with hafnium. This makes them attractive for versatile mid-IR applications. Furthermore, HYAS core-glass fiber co-doped with Bi is revealed to have all the signs of `active' (fluorescing) Bi-related centers, thus being suitable for lasing/amplifying in the nearIR spectral range. (C) 2017 Optical Society of Americ

Ce-doped and Ce/Au-codoped alumino-phospho-silicate fibers: Spectral attenuation trends at high-energy electron irradiation and posterior low-power optical bleaching

We report a study of attenuation spectra' transformations in a couple of Cerium (Ce) doped alumino-phospho-silicate fibers (one of them codoped with gold (Au)), occurring under irradiation by a beam of high-energy beta-electrons. The experimental data reveals an essential effect of beta-irradiation upon the absorptive properties of the fibers, given by noticeable susceptibility of Ce ions in Ce3+/Ce4+ valence states to the treatment, arisen as growth followed by saturation of induced absorption. We also report posterior bleaching of the beta-darkened fibers, also in terms of attenuation spectra' transformations, at exposing them to low-power green (a He-Ne laser) and UV (mercury lamp) light, the effect never reported for Ce-doped fibers. It is shown that both phenomena are less expressed in Ce fiber codoped with Au than in Au-free one and that the spectral changes in the former are more regular and plain vs. irradiation dose and bleaching time. Possible mechanisms responsible for the phenomena and their impact at using such fibers for dosimetry and other applications are discussed. (C) 2013 Optical Society of Americ