1,720,990 research outputs found
Microring Resonators as Integrated Sources of Nonclassical States of Light
No full textThe experimental work that is reported in the thesis explores some properties and possible uses of silicon microring resonators as integrated sources of non-classical states of light, based on the enhancement of non-linear effect of four-wave mixing (FWM).The experimental work that is reported in the thesis explores some properties and possible uses of silicon microring resonators as integrated sources of non-classical states of light, based on the enhancement of non-linear effect of four-wave mixing (FWM)
DEVICE COMPRISING A RING OPTICAL RESONATOR
No full textA device includes an optical resonator having four ports including a first port, a second port, a third port, and a fourth port. A first electronic circuit is configured to calculate a first information representative of a power difference between optical signals supplied by two of the four ports. A method of operating a device is also disclosed
Recent Advances in Perovskite Single-Crystal Thin Film Optoelectronic Devices
Full text linkAmong novel semiconductors, perovskites have gained significant attention due to their versatility, combining tunable optoelectronic properties with relatively easy fabrication processes. However, certain issues still hinder their widespread use, often related to the presence of defects and traps within the material. Beyond defect passivation in polycrystalline thin films, an alternative approach to enhancing material quality lies in the fabrication of single crystals. This review aims to provide an overview of the promising approaches explored to address specific challenges of perovskites that benefit from the single crystal nature, restricting our analysis to perovskite single crystal thin films (PSC-TF). We will discuss novel fabrication techniques and highlight recent achievements in devices, such as photodetectors, solar cells, and transistors. By examining the fundamental properties already discovered and showcasing the latest advancements, we aim to provide an overview of the perspectives and open challenges for PSC-TF in next-generation optoelectronic devices
Low-power four-wave mixing in porous silicon microring resonators
No full textWe report the measurement of low-power continuous-wave four-wave mixing in porous silicon microring resonators operating in the 1550 nm telecom band. Resonantly enhanced stimulated four-wave mixing has been measured in rings with 25 mu m radius and quality factor around 5000 for pump powers as low as a few hundreds of microwatts. A waveguide nonlinear parameter gamma = 20 W-1 m(-1) has been determined. These results suggest further research on porous silicon for low-power nonlinear optics, possibly taking advantage of its tunable porosity
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
Single Crystal Sn-Based Halide Perovskites
Full text linkSn-based halide perovskites are expected to be the best replacement for toxic lead-based counterparts, owing to their similar ionic radii and the optimal band gap for use in solar cells, as well as their versatile use in light-emitting diodes and photodetection applications. Concerns, however, exist about their stability under ambient conditions, an issue that is exacerbated in polycrystalline films because grain boundaries present large concentrations of defects and act as entrance points for oxygen and water, causing Sn oxidation. A current thriving research area in perovskite materials is the fabrication of perovskite single crystals, promising improved optoelectronic properties due to excellent uniformity, reduced defects, and the absence of grain boundaries. This review summarizes the most recent advances in the fabrication of single crystal Sn-based halide perovskites, with emphasis on synthesis methods, compositional engineering, and formation mechanisms, followed by a discussion of various challenges and appropriate strategies for improving their performance in optoelectronic applications
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
Halide double-perovskites: High efficient light emission and beyond
Full text linkLead-free halide double perovskites are stable and versatile materials for a wide range of applications, particularly for lighting, thanks to their very efficient emission of warm white light. Element substitution in halide double perovskite is recognized as a powerful method for tuning the emission wavelength and improve the efficiency. This review provides an overview on composition and recent progress in halide double perovskite with main focus on the synthesis and emission properties of chloride-based compounds
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