1,721,061 research outputs found
Neodymium doped chalcogenide glass fibre laser
No full textWe report on laser action in a Neodymium doped Gallium Lanthanum Sulphide glass fibre. Laser action at 1080nm was obtained in a 22mm long multimode glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour
Chemical etching of AlF-based glasses
No full textAluminium fluoride based glass [AlF3-M(II)F2-xPO3 M=Mg, Ca, Ba, Sr] fibres have potential for use as 1.3µm amplifiers, but successful application depends on improving their poor mechanical strength. Surface contamination of the preform is a major factor contributing to the lack of strength; it can be improved by chemical etching. As the glass components are highly unreactive, few etching studies have been reported in the literature. In this work, two multicomponent etches have been identified for the purpose and characterised. Optimum working compositions are 0.4M AlCl3 - 6 H2O / 1M HCl and 50% HF (48%) / 30% HNO3 (68%) / 20% H2O plus 3M H3BO3. Both yield fibres of significantly improved strength and quality, although the former etch tends to perform slightly better. Furthermore, an etch procedure has been developed for the aluminium chloride mixture which enables good strength fibre to be pulled in a controlled and reproducible manner
Rare-earth doped chalcogenide glass fibre laser
Full text linkWe report on the first laser action in a rare-earth doped chalcogenide glass fibre. Laser action at 1080nm was obtained in a 22mm long gallium lanthanum sulphide glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour
Chemical etching of AlF<sub>3</sub>-based glasses
No full textIn this work, two multi component etches have been identified for the purpose of etching aluminium fluoride based [AlF3-M(II)F2-xPO3, M=Mg, Ca, Ba, Sr] fibre samples to improve their mechanical strength. Optimum working compositions are (i) 0.4M AlCl3·6H2O/1M HCl and (ii) (by volume) 50% HF (48%)/30% HNO3 (68%)/20% H2O with 3M H3BO3 dissolved. Both yield fibres of improved strength and quality, although the former etch performs better. Furthermore, an etch procedure has been developed for the aluminium chloride mixture which enables increased strength fibre to be pulled in a controlled and reproducible manner
Thulium-doped tellurite fiber for s-band amplification
No full textSpectroscopy measurements and the first demonstration of fiber gain in thulium doped tellurite for S-band amplification is reported. The gain extends to longer wavelength than in fluorides showing improved overlap with the C-band EDFA
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A 1317nm neodymium doped fluoride glass waveguide laser
No full textLaser emission at 1317nm has been observed for the first time in a neodymium doped fluoroaluminate glass waveguide fabricated by a combination of hot dip spin coating and direct UV writing
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