1,720,966 research outputs found
Spectral properties of Er<sup>3+</sup>-doped chalcogenide glasses
No full textLanthanum sulphides glasses formed with sufficient proportions of Ga2S3 constitute a very convenient matrix for rare earth sulphides, and Pr3+-doped Ga2S3:La2S3 (GLS) glasses have been recognized as one of the most promising candidates for fibre amplifiers operating at a wavelength of 1.3µm. In this report, the spectral properties of chalcogenide glass of the molar composition 0.7Ga2S3:0.3La2S3 doped with Er3+ are presented and discussed. Emission and absorption spectra and lifetimes of energy levels have been measured. The 2.7µm emission, as shown below, has been observed from chalcogenide glass for the first time. Radiative and non-radiative transition rates are calculated and compared with the measured lifetimes of interesting energy levels
Direct observation of cooperative upconversion mechanisms in erbium-doped fibre amplifiers
No full textBy examining upconversion fluorescence in Er3+-doped fibres, ion-pair upconversion and uniform upconversion have been directly and separately observed. An upper limit for the ion-pair lifetime has been determined
Applications of polymer optical fibre grating sensors to condition monitoring of textiles
Full text linkFibre Bragg gratings (FBGs) in polymer optical fibres (POFs) have been used to measure the strain in a woven textile.
FBGs in both POFs and silica optical fibres were attached to a woven textile specimen, and their performance
characterised. It was demonstrated that the POF FBGs provide improved strain transfer coefficients and reduce local
structural reinforcement compared to silica FBGs and therefore make a more suitable proposition for textile monitoring
Spectral properties of Er<sup>3+</sup>-doped gallium lanthanum sulphide glass
No full textThe spectral properties of chalcogenide glass 0.7Ga2S3:0.3La2S3 (Ga:La:S) doped with Er3+ are presented and discussed. Emission and absorption spectra and lifetimes of energy levels have been measured. The 2.7 km emission of Er3+ has been observed from chalcogenide glass for the first time. Radiative and non-radiative transition rates are calculated and compared with the measured lifetimes of interesting energy levels. Comparing this glass with Er3+-doped silica glasses, it is shown that the absorption and emission cross-sections of Er3+-doped Ga:La:S are around 2.5 times higher, radiative transition rates are around five times higher due to its higher refractive index, while multiphonon non-radiative decay rates are around three orders lower due to its much lower phonon energy. Furthermore, the inverse energy transfer process in Er3+:Ga:La:S glass may have significant implications for the operation of Er3+:Ga:La:S devices. These spectral properties, along with the higher solubility for rare earth-ions in Ga:La:S, make this glass a good candidate for new application
Fabrication and optical characterisation of doped germanosilicate fibres
No full textThis work assesses the incorporation of dopant ions such as Al3+, Ga3+, Zr4+, Nb5+, Ta5+ and Er3+ into the core of germanosilicate optical fibres via modified-chemical-vapour deposition plus solution doping fabrication techniques. We find that highly-charged smaller ions, like Al3+ and Ta5+, behave similarly. These ions are more efficiently incorporated, assist in the incorporation of Er3+, and have the same influence on the fluorescence spectra of Er3+. The structural role of these ions appear to be their ability to provide nonbridging oxygens around Er3+. The waveguide and lasing characteristics of Er3+ codoped with Ta5+ are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Proposal for an Er<sup>3+</sup>-doped chalcogenide glass fiber upconversion laser operating at 980nm and pumped at 1480nm
Full text linkWe propose a novel fiber upconversion laser operating at 980 nm and pumped at 1480 nm, which will allow remote optical pumping of erbium-doped optical amplifiers. From the measured spectroscopy, we show Er3+-doped gallium lanthanum sulphide glass to be a potential host for such a 1480nm/980nm upconversion laser. The small-signal gain is analyzed numerically and the lasing possibilities are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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