1,720,972 research outputs found
UV laser-induced poling inhibition in proton exchanged optical waveguides in lithium niobate
No full textUV laser-induced poling inhibited domain building blocks for photonic and nonlinear optical microstructures
No full textWe demonstrate that partial overlap of UV laser irradiated tracks on the +z face of lithium niobate crystals allows the composition of arbitrary shaped complex large scale ferroelectric domain structures by inhibition of poling
Ferroelectric domain building blocks for photonic and nonlinear optical microstructures in LiNbO<sub>3</sub>
No full textThe ability to manipulate the size and depth of poling inhibited domains, which are produced by UV laser irradiation of the +z face of lithium niobate crystals followed by electric field poling, is demonstrated. It is shown that complex domain structures, much wider than the irradiating laser spot, can be obtained by partially overlapping the subsequent UV laser irradiated tracks. The result of this stitching process is one uniform domain without any remaining trace of its constituent components thus increasing dramatically the utility of this method for the fabrication of surface microstructures as well as periodic and aperiodic domain lattices for nonlinear optical and surface acoustic wave applications. Finally, the impact of multi exposure on the domain characteristics is also investigated indicating that some control over the domain depth can be attained
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
Annealing of amorphous silicon using c.w. visible lasers
No full textThe strong absorption of c.w. laser radiation in the green/blue spectral region has been used to thermally anneal and locally crystalize small volumes of amorphous silicon (a-Si) which has been thermally insulated from the environment. We will present experimental results for two distinct cases where this method has been used for producing high quality c-Si and secondly for allowing additional optoelectronic functionality to be built into the material. More specifically we will discuss laser annealing results obtained in cylindrical and planar geometries; in a-Si core optical fibers and in a-Si thin films deposited on fused silica slabs and on the polar faces of LiNbO3 single crystals. In both geometries crystallization of a-Si has been achieved, in some cases producing crystallites with enormous aspect ratios. In the case of a-Si core fibers we have not only achieved a significant improvement of the optical quality of the silicon material, but also observed some tuneability of its optoelectronics properties. LiNbO3 on the other hand is one of the cornerstone platforms of nonlinear/integrated optics. By transferring the materials processing advances made in our silicon fibers to LiNbO3, we can envisage a platform that exploits the superior optical and electronic properties of both materials for the development of high performance optoelectronic devices. Our preliminary results are very encouraging and we believe that this combination promises many exciting future applications
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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