1,720,981 research outputs found
Precision dicing of optical materials
Full text linkDuctile regime dicing has been used to machine a variety of optical materials to produce waveguides for lasers, multi-mode interference devices and non-linear devices. However, few papers discuss the properties of the machining, either qualitatively or quantitatively. In this work ductile regime dicing of germanium, Yttrium Aluminum Garnet (YAG), lithium niobate and silicon for photonic applications are reported. Machining parameters are discussed, surface micrographs shown, and surface roughnesses are calculated for each sidewall machined. The sidewall average surface roughnesses (Sa) were measured to be 2.1 nm for germanium, 3.5 nm for YAG, 7.9 nm for lithium niobate and 8.6 nm for silicon
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
Micromilling with nanoscale roughness for silica photonics
No full textWe present Flame Hydrolysis Deposition (FHD) silica micromilled with nanoscale surface roughness, sub-micron form control and micron scale depths of cut for photonic applications. Using our in-house developed high-precision micromill and industrially standard micromill tools, we have machined slots 1.5 mm long and 17 µm deep, enabling access and interaction with the evanescent field of nearby UV-written waveguides. Potential applications vary from: biological sensing, plasmonic devices, refractometers and chemical sensing. The micromilling approach offers advantages over conventional cleanroom and laser-based machining of optical materials in both form control and achievable surface roughness. To assess optimum cutting conditions a wide parameter test was conducted, where the rotational and translational speeds were varied and feed speeds optimized to allow cutting in the high-quality low-chipping ductile regime. Whilst milling in the ductile regime our smoothest form slots had a surface roughness of 3.0 nm (Sa) at a 17.0µm depth of cut. This represents a forty times increase in cut depth and an eight times improvement in surface roughness over previously reported silica slot micromilling. We will present our latest machining results with studies into sequential slot milling and report on the subsequent slot form, surface roughness, and mill wear from prolonged sequential machining. We will also show results of integrating milled slots with optical waveguides and Bragg gratings to create refractometer devices
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
Optomechanical cantilever device for displacement sensing and variable attenuator
No full textAn optomechanical double cantilever device has been fabricated with applications as a displacement sensor and variable attenuator. The device is based on a silica glass on silicon substrate. A novel fabrication approach using a precision dicing saw is used, which has benefits in terms of cost, fabrication time and energy consumption compared to cleanroom based lithography techniques. The silica cantilevers contain integrated optical waveguides and Bragg gratings fabricated using a Direct UV Writing process. The cantilevers are deflected out of plane by thin film stress effects, providing a suitable geometry for use in sensing. Displacement causes both cantilevers to move simultaneously resulting in variable coupling due to the angular alignment of the waveguide modes. Using a developed ratiometric approach based on fitting to Gaussian apodized Bragg gratings, the measured displacement is completely independent of fluctuations in light source power as well as insensitive to detector noise. The device is optically interrogated at a wavelength band around 1550nm. As a sensor the device has a sensitivity of 0.8 dB/micron and can be accurately modelled using fiber optic coupling misalignment theory. When operating as an attenuator, a suppression ratio of over 20dB can be obtained. If combined with integrated optical components such as X-couplers, multiple double cantilever arrays can be placed on the same chip for distributed sensing. We will report detailed fabrication procedures as well as optical characterization of the device including the performance metrics of the force sensor
Micro-mechanical integrated optical structures
No full textThe work presented, reports recent developments in the fabrication of micro-mechanical integrated optical components. Combining physical micromachining and direct UV-writing, micro-membranes micro-cantilevers and microbridge structures are fabricated
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