1,720,964 research outputs found
Engineering spin and antiferromagnetic resonances to realize an efficient direction-multiplexed visible meta-hologram
No full textDriven by the need for enhanced integrated performance and rapid development of ultrathin multitasked optical devices, this paper experimentally demonstrates monolayer direction-controlled multiplexing of a transmissive meta-hologram in the visible domain. The directional sensitivity is designed by imparting direction-controlled spin-dependent holographic recordings in the monolayer structure. The designed metasurface hologram consists of nano half-waveplates (HWPs) of low loss hydrogenated amorphous silicon (a-Si:H). These nano-featured HWPs are carefully designed and optimized for circularly polarized (CP) illumination to not only excite electric and magnetic resonances simultaneously but also to excite antiferromagnetic modes to ensure high transmission for the cross CP-light. The antiferromagnetic modes are excited in such a way that the transmitted CP-light maintains the Ex component of the incident CP-light through even antiparallel magnetic dipoles while they reverse the E-y component via odd antiparallel magnetic dipoles. As compared to the standard amorphous silicon, our a-Si:H exhibits a much lower absorption coefficient in the visible domain. The proposed single-layer design is an advanced step towards scalability, low-cost fabrication, and on-chip implementation of novel metasurfaces with substantially higher performance in the visible domain.11Nsciescopu
Tungsten-based ultrathin absorber for visible regime
Get PDFUtilizing solar energy requires perfect absorption of light by the photovoltaic cells, particularly solar thermophotovoltaics (STPVs), which can be eventually converted into useful electrical energy. Ultrathin nanostructures, named metasurfaces, provide an intriguing platform to develop the miniaturized solar energy absorbers that can find potential applications in integrated photonics, optical sensing, color imaging, thermal imaging and electromagnetic shielding. Therefore, the quest of novel materials and designs to develop highly efficient absorbers at minuscule scale is an open topic. In this paper, novel absorbers using tungsten-metasurface are developed which give ultrahigh absorbance over a wide frequency spectrum. The proposed designs are two-dimensional, polarization insensitive, broadband and are predicted to give better response under high temperatures ascribed to high melting point of tungsten i.e. 3422 degrees C. Amongst these designs, cross alignment is found optimum for tungsten, because it is impedance matched with the free space for visible spectrum. This cross arrangement is further tweaked by changing width, height and length resulting in 7 different optimized solutions giving an average absorbance greater than 98%. One, amongst these solutions, gave a maximum average absorbance of 99.3%.114Nsciescopu
Geometric and physical configurations of meta-atoms for advanced metasurface holography
No full textMetasurfaces consisting of subwavelength structures, so-called meta-atoms, have steadily attracted considerable attention for advanced pi due to their advantages in terms of high-resolution holographic images, large field of view, and compact device volume. In contrast to conventional holographic displays using bulky conventional diffractive optical elements, metasurface pi enables arbitrary complex wavefront shaping with a much smaller footprint. In this review, we classify metasurface holography according to the meta-atom design methodologies, which can further expand hologram functionalities. We describe light-matter interactions, particularly in metasurface systems, using the relevant the Jones matrix to rigorously explain modulations of the amplitude, phase, and polarization of light. Six different types of meta-atoms are presented, and the corresponding achievable wavefronts that form the holographic images in the far-field are also provided. Such a simple classification will give a straightforward approach to design and further realize advanced metasurface holographic devices.11Ysci
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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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