1,721,026 research outputs found
Chiroptical properties of plasmonic nanohole arrays.
Get PDFRecent advances in chiral nanophotonics in man-made metasurfaces have highlighted the importance of chirality in enhancing light-matter interactions, manipulating light’s polarization states, detecting and analyzing chemical substances, and many more. A typical probe of chirality is circular dichroism CD in optical properties like absorption, reflection, and transmission. Through this work, two chiral plasmonic metasurfaces were analyzed to enhance the CD -in particular, absorption CD and hence increase the chiral sensitivity of the system. The metasurfaces are arranged in a square lattice within a metallic layer placed on a glass substrate.
The first metasurface consists of elliptical nanohole arrays realized in different metals such as silver, gold, and aluminum. This plasmonic metasurface exhibits an intrinsic chiral effect due to reduced symmetry via the elliptical shape of the nanoholes and their rotation.
The findings reveal that strong CD occurs in the absorption and transmission spectra at wavelengths where extraordinary optical transmission EOT is observed. This indicates a significant resonant coupling between light and surface plasmon polaritons SPPs at the metal/glass and metal/air interfaces.
The elliptical shape of the nanoholes leads to splitting of absorption peaks at each SPP resonance, while tilting of the nanohole axis produces an imbalance between the fields originating from linear polarizations along the long and short axes; as a result, they sum up with a phase delay of -90 (LCP) or +90(RCP), ending up in a CD for tilted holes and explaining the strongly dispersive features of CD spectra.
The study also explores how to optimize CD by varying parameters such as the diameters and tilt of the elliptical nanoholes, the thickness of the metallic layer, and the lattice constant. This optimization is crucial for designing metasurfaces with robust and tunable CD properties. The results indicate that silver (Ag) and gold (Au) metasurfaces are effective for CD resonances above 600~nm. At the same time, aluminum (Al) metasurface is suitable for strong CD resonances in the shorter wavelength range of the visible spectrum and near-UV. The UV region is particularly noteworthy as it encompasses the absorption spectrum of various chiral biomolecules. Promising applications for these elliptical plasmonic metasurfaces can be in sensing the chiral molecules and detecting and analyzing biological substances that exhibit chirality.
The second metasurface is a gold metasurface with nanoholes deformed from circular to oval shape. The metasurface with circular holes supports a bound state in the continuum BIC at the lower energy side of the SPP. Upon deforming the circular holes to oval holes, this metasurface displays an extrinsic chiral response primarily dominated by a quasi-BIC with nearly maximal values of the absorption CD at small angles of incidence, which are found to be almost independent of the specific deformation of the holes in the metasurface. This suggests that the design can be flexible while still achieving strong chiral effects.
The research also highlights the demonstration of a strong CD in emission, indicating that the enhanced chiral response is not limited to absorption but extends to emitted light. This broadens the potential applications of the findings in chiral light sources.
The extrinsically chiral response arises from a symmetry-broken BIC, associated with significantly enhancing the local electric field. This insight provides a deeper understanding of the mechanisms behind chiral responses in plasmonic metasurfaces.
Moreover, we theoretically investigated the chiral plasmonic BIC in the strong coupling regime, wherein we found evidence of plasmon-polariton BIC modes coupled to the resonance of the active medium
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
Maximum Chirality Empowered by a Bound State in a Continuum in a Plasmonic Metasurface
Get PDFAchieving a strong and robust chiral response in plasmonic metasurfaces is among the key goals of current nanophotonic research. In this work, we theoretically show that the circular dichroism (CD) of a metal metasurface can be maximized by exploiting the concept of a bound state in a continuum (BIC) with symmetry breaking. We consider a gold metasurface with a deformation of circular holes into oval holes. The chiral response at small values of the angle of incidence is dominated by a quasi-BIC, with nearly maximal values of the absorption CD that are almost independent of the deformation. A strong CD in emission is also demonstrated. Symmetry analysis and mode profiles show that the extrinsically chiral response does indeed follow from a symmetry-broken BIC and is associated with a strong enhancement of the local electrical field. The concept of a plasmonic BIC with symmetry breaking provides a robust pathway to increase the chiral response in metal metasurfaces and opens research opportunities in chiral plasmonics that combine narrow resonances with local field enhancement
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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