1,720,986 research outputs found
High Thermo-Optic Coefficient of Silicon Oxycarbide Photonic Waveguides
Full text linkIn this Letter, we report on the observation of a high thermo-optic coefficient (TOC) of silicon oxycarbide (SiOC) films deposited by reactive RF magnetron sputtering for integrated photonic waveguides. In the 1550 nm wavelength range, the measured TOC of SiOC is as large as 2.5 X 10(-4) RIU degrees C-1, which is about 30 times larger than that of silica and almost twice that of silicon. Thin films of SiOC have been integrated in germanium-doped silica and silicon oxynitride conventional waveguide technology, achieving a 10x and 3x enhancement of the waveguide effective TOC, respectively. These results demonstrate the potential of SiOC for the realization of highly efficient phase actuators and low-power-consumption thermally tunable photonic integrated platforms
Semiconductor Laser in Distributed Optical Feedback Regime
Full text linkIn this work, we first analyse the behaviour of semiconductor laser in the presence of weak-to-moderate feedback from a single (lumped) and double external cavity setting. Analysis of laser diode in dynamic double cavity configuration shows that the dynamic double cavity does not disturb the stability of the laser device, but it introduces a considerable shift in the emission frequency that is directly related to the feedback strength and the relative phase difference between the phase of the two mirrors, and the phase of electric field inside the laser diode. Conditions for maximum and minimum impact of the laser emission wavelength have been derived. Addressing the issue of distributed optical feedback, optical feedback produced by more than two external mirrors has been also studied. To this aim we have first generalized the Lang and Kobayashi deterministic rate equations model to arbitrary number of external reflectors and provide the corresponding steady-state solution, which is done for the first time. To the best of our knowledge, this kind of study is carried out for the first time
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
Integrated photonic devices with silicon oxycarbide
Full text linkIn this paper, we report on the potential of silicon oxycarbide (SiOC) for integrated photonic applications. SiOC films are developed by reactive radio frequency magnetron sputtering from a silicon carbide (SiC) target in the presence of argon and oxygen gases. The optical properties of the developed SiOC film are characterized with spectroscopic ellispometry over a broad wavelength range 300-1600 nm. The refractive index n of the SiOC film is 2.2 at wavelength lambda = 1550 nm and the extinction coefficient k is estimated to be less than 10(-4) in the near-infrared region above 600 nm. The topography of SiOC films is studied with AFM showing very smooth surface, with rms roughness of 0.24 nm. SiOC film with refractive index n = 2.2 is then patterned by direct laser-writing lithography and etched with reactive ion etching to realize high contrast SiOC core optical waveguides for integrated photonics applications. The waveguide losses are characterized at telecommunication wavelength lambda = 1550 nm. As an example of photonic integrated devices integrating SiOC films, a microring resonator is fabricated where a SiOC layer is used as a coating material for the core of a silicon oxynitride (SiON) waveguide
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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