1,720,977 research outputs found
Group IV Mid-infrared waveguide-based bolometers
No full textMid-Infrared (MIR) silicon photonics, known as MIR group IV photonics, is an emerging area which aims to extend silicon photonics to longer wavelengths. MIR silicon photonics can address applications in environmental and biological sensing, homeland security, industrial process control and telecommunications. To realise MIR lab-on-chip photonic sensors, photodetectors which can operate at any MIR wavelengths are required. As the MIR integrated detectors developed so far are limited by either operation wavelength range or wafer scale fabrication, thermal detectors may be the best options for low-speed applications requiring broadband detection, such as sensing. This thesis presents the investigation of MIR waveguide integrated bolometers. The first uncooled silicon waveguide-based bolometers in the Silicon-on-Insulator (SOI) and suspended silicon waveguide platforms are presented in this thesis. The bolometers comprise gold plasmonic antennas on the waveguide surface that heat up when they absorb light, and Amorphous Silicon (a-Si) thermometers (formed by ion implantation), whose Temperature Coefficient of Resistance (TCR) is 0.90 % K−1 . The responsivity of bolometers based on suspended silicon waveguides is 1.13 %/mW at 3.8 µm wavelength. To further improve the performance, bolometers based on an a-Si platform have been investigated. The bolometers with p-type a-Si thermometers show a TCR of 1.90 % K−1 and a responsivity of 24.62 %/mW at 3.8 µm wavelength. The thermal conductance of the bolometer is 3.86 × 10−5 W/K and an improvement as large as 3 orders magnitude may be possible in the future through redesign of the device geometry. Moreover, the response of antenna arrays with different input polarisation have been investigated to prove that polarisation-dependent Localized Surface Plasmon Resonance (LSPR) is excited in bolometers
Dataset for suspended low-loss germanium waveguides for the longwave-infrared
No full textData corresponding to the data in figures 3 and 6 of the article 'Suspended low-loss germanium waveguides for the longwave-infrared' published in Optics Letters.</span
Mid-infrared nanometallic antenna assisted silicon waveguide based bolometers
No full textThe mid-infrared (MIR) wavelength region is attracting more and more research for applications such as medical diagnostics, environmental monitoring, and free space communications. In the MIR, thermal detectors play an important role because they can operate over a large wavelength range, can be fabricated using CMOS compatible processes, and do not require cooling. Today no other MIR detector technology is able to fill this gap. We demonstrate the first uncooled silicon waveguide-based bolometers, in the Silicon-on-Insulator (SOI) and suspended silicon waveguide platforms. The bolometers comprise gold plasmonic antennas on the waveguide surface that heat up when they absorb light, and amorphous silicon thermometers (formed by ion implantation), whose electrical resistance changes by 0.90 ± 0.26 % K-1 when they are heated. We show that suspending the bolometers improves their performance, and achieve sensitivities of up to 1.13 ± 0.04 % change in resistance per milliwatt of input power, with a noise equivalent power of 66 μW/√Hz. Calculations suggest the NEP could in future, be further reduced by 4 orders of magnitude
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
Suspended low-loss germanium waveguides for the longwave-infrared
No full textGermanium is a material of high interest for midinfrared (MIR) integrated photonics due to its CMOS compatibility and its wide transparency window covering the 2–15 μm spectral region exceeding the 4 and 8 μm limit of the Silicon-on-Insulator (SOI) platform and Si material respectively. In this Letter, we report suspended germanium waveguides operating at a wavelength of 7.67 μm with a propagation loss of 2.6 ± 0.3 dB/cm. To our knowledge, this is the first demonstration of low-loss suspended germanium waveguides at such a long wavelength. Suspension of the waveguide is achieved by defining holes alongside the core providing access to the buried oxide layer and the underlying Si layer so that they can be wet etched using HF and TMAH respectively. Our MIR waveguides create a new path towards long wavelength sensing in the fingerprint region
Dataset for mid-infrared nanometallic antenna assisted silicon waveguide based bolometers
No full textDataset supports: Wu, Y. et al. (2019). Mid-infrared nanometallic antenna assisted silicon waveguide based bolometers. ACS Photonics. </span
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
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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