1,721,074 research outputs found
Challenges in fabrication towards realization of practical metamaterials
No full textMetamaterials, artificially structured materials consisted of sub-wavelength unit cells, have attracted tremendous attentions in physics, material science, and engineering over the past decade. Many exotic and extraordinary electromagnetic phenomena such as negative refractive index, invisibility cloaking and super-resolution imaging have been realized through metamaterials. Now, metamaterials need to be focused on nanoscale optical metamaterials, operating at ultra-violet (UV), visible and near-infrared (NIR) frequencies for practical applications of them. Here, we review the fundamentals, recent progress, main challenges, and future direction of optical metamaterials and related fabrication processes. The fundamentals and recent progress of the optical metamaterials are discussed with representative examples such as negative index metamaterials and invisible cloaks. Main challenges in fabrication for practical metamaterials, three-dimensional and large-scale metamaterials, and brief discussion about the outlook for the next generation scalable nanofabrication methodologies are followed. (C) 2016 Elsevier B.V. All rights reserved.1197Nsciescopu
Nanophotonic modal dichroism: mode-multiplexed modulators
Full text linkAs the diffraction limit is approached, device miniaturization to integrate more functionality per area becomes more and more challenging. Here we propose a strategy to increase the functionality-per-area by exploiting the modal properties of a waveguide system. With such an approach the design of a mode-multiplexed nanophotonic modulator relying on the mode-selective absorption of a patterned in-dium-tin-oxide (ITO) is proposed. Full-wave simulations of a device operating at the telecom wavelength of 1550 nm show that two modes can be independently modulated, while maintaining performances in line with conventional single-mode ITO modulators reported in the recent literature. The proposed design principles can pave the way to a class of mode-multiplexed compact photonic devices able to effectively multiply the functionality-per-area in integrated photonic systems. (C) 2016 Optical Society of America1153Ysciescopu
Photonic spin Hall effect by the spin-orbit interaction in a metasurface with elliptical nano-structures
No full text114Nsciescopu
Fabrication of three-dimensional suspended, interlayered and hierarchical nanostructures by accuracy-improved electron beam lithography overlay
Full text linkNanofabrication techniques are essential for exploring nanoscience and many closely related research fields such as materials, electronics, optics and photonics. Recently, three-dimensional (3D) nanofabrication techniques have been actively investigated through many different ways, however, it is still challenging to make elaborate and complex 3D nanostructures that many researchers want to realize for further interesting physics studies and device applications. Electron beam lithography, one of the two-dimensional (2D) nanofabrication techniques, is also feasible to realize elaborate 3D nanostructures by stacking each 2D nanostructures. However, alignment errors among the individual 2D nanostructures have been difficult to control due to some practical issues. In this work, we introduce a straightforward approach to drastically increase the overlay accuracy of sub-20 nm based on carefully designed alignmarks and calibrators. Three different types of 3D nanostructures whose designs are motivated from metamaterials and plasmonic structures have been demonstrated to verify the feasibility of the method, and the desired result has been achieved. We believe our work can provide a useful approach for building more advanced and complex 3D nanostructures.114sciescopu
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
High Refractive index Ti3O5 films for dielectric metasurfaces
No full textTi3O5 films are deposited with the help of an electron beam evaporator for their applications in metasurfaces. The film of subwavelength (632 nm) thickness is deposited on a silicon substrate and annealed at 400 degrees C. The ellipsometry result shows a high refractive index above 2.5 with the minimum absorption coefficient in the visible region, which is necessary for high efficiency of transparent metasurfaces. Atomic force microscopy analysis is employed to measure the roughness of the as-deposited films. It is seen from micrographs that the deposited films are very smooth with the minimum roughness to prevent scattering and absorption losses for metasurface devices. The absence of grains and cracks can be seen by scanning electron microscope analysis, which is favorable for electron beam lithography. Fourier transform infrared spectroscopy reveals the transmission and reflection obtained from the film deposited on glass substrates. The as-deposited film shows high transmission above 60%, which is in good agreement with metasurfaces.1111Nsciescopu
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
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