1,721,564 research outputs found
Dataset for All-fiber fourth and fifth harmonic generation from a single source
No full textRaw data for figures in Abdul Khudus, Muhammad, Lee, Timothy, De Lucia, Francesco, Corbari, Constantino, Sazio, Pier-John, Horak, Peter and Brambilla, Gilberto (2016) All-fiber fourth and fifth harmonic generation from a single source. Optics Express, 24, (19), 21777-21793. (doi:10.1364/OE.24.021777)</span
Nonlinear properties of optical microfibres
No full textGlass microfibre waveguides offer an intriguing platform for the investigation of nonlinear effects, due to their high effective nonlinearity which arises from the tight modal confinement down to dimensions comparable to the wavelength of guided light. This thesis presents theoretical and experimental work towards achieving efficient third and second harmonic generation in silica microfibres, as well as in microfibre loop resonators for enhancing the conversion. Since microfibre resonators themselves exhibit interesting nonlinear behaviour, the polarisation dependent properties of microcoil resonators were also studied. Efficient third harmonic generation is possible through intermodal phase matching, and experiments using short tapers have demonstrated significant efficiencies up to 10-3 over a uniform 4 mm waist. On the other hand, the interrogation of longer tapers, in which the harmonic generation occurs within the taper transition regions of several cm rather than the waist, allows for a broadband conversion observed to exceed 36 nm at the 5 dB bandwidth level. A straightforward technique to improve efficiency using microfibre loop resonators was also investigated. Near resonance, the recirculation of the pump power inside the resonator was experimentally shown to increase conversion by 7.7 dB higher than that of the straight microfibre, similar to simulated predictions, and by optimising the loop geometry the resonant efficiency enhancement can potentially reach 20 dB.Simulations on second harmonic generation in microfibres indicate that the second order nonlinearity originates primarily from the structural anisotropy at the glass-air boundary (which exploits the high surface electric field strength of microfibres) as well as multipolar effects within the bulk. To overcome the inherent weakness of these effects, experiments focused on conversion enhancement via the aforementioned technique using loop resonators, with a measured 7.6 dB efficiency improvement.In addition, an accurate polarisation dependent model for microcoils was developed for both the linear and nonlinear regimes by incorporating the effects of fibre twist and birefringence. The coupling between orthogonally polarised modes propagating along the microcoil results in a strongly polarisation sensitive transmission, especially near resonances, which in turn influences the nonlinear hysteresis characteristics
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
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