1,720,964 research outputs found
Frequency resolved optical gating in the 1.55 µm-band via cascaded χ(2) interactions
No full textWe investigate cascaded χ(2) ultrashort pulse interactions and propose their use for frequency-resolved optical gating at telecom wavelengths in a waveguide configuration. Better efficiency and time-resolution compared to single-step χ(2) interactions can be achieved
Proton-exchanged lithium niobate waveguides for photonic applications
No full textThis talk shall provide an overview of the current activity on integrated LiNbO3 devices based on proton-exchange techniques at the ORC. We shall present the technology and the experimental results obtained so far on slab waveguides in 2D Nonlinear Photonic Crystals and on channel waveguides in Periodically Poled Lithium Niobate and discuss perspective applications for all-optical signal processing in ultra-fast fibre telecom systems
Frequency resolved optical gating in the 1.55µm band via cascaded χ(2) processes
No full textWe investigate ultrashort-pulse interactions based on cascaded second-harmonic generation and difference-frequency generation and propose their use for frequency-resolved optical gating (FROG) at telecom wavelengths in a waveguide configuration. We show how a χ(2)-χ(2) FROG device could allow the efficient characterization of ultrashort pulses, with time resolutions well beyond the limits normally imposed by walk-off effects on single-step χ(2) FROG devices
Theoretical and numerical investigations of parametric transfer via difference frequency generation for indirect mid-infrared pulse shaping
No full textWe theoretically and numerically investigate indirect mid-infrared pulse shaping via parametric transfer, specifically difference-frequency generation. We define a quantitative measure for the fidelity of parametric transfer, and investigate the effect of material dispersion and process nonlinearity on the parametric transfer. We show that a good fidelity transfer of a broad-bandwidth pulse can be efficiently achieved with a reasonable wavelength tunability, by careful design of the experimental configuration
High fidelity femtosecond pulses from an ultrafast fiber laser system via adaptive amplitude and phase pre-shaping
No full textThe generation of high-fidelity femtosecond pulses is experimentally demonstrated in a fiber based chirped-pulse amplification (CPA) system through an adaptive amplitude and phase pre-shaping technique. A pulse shaper, based on a dual-layer liquid crystal spatial light modulator (LC-SLM), was implemented in the fiber CPA system for amplitude and phase shaping prior to amplification. The LC-SLM was controlled using a differential evolution algorithm, to maximize a two-photon absorption detector signal from the compressed fiber CPA output pulses. It is shown that this approach compensates for both accumulated phase from material dispersion and nonlinear phase modulation. A train of pulses was produced with an average power of 12.6W at a 50MHz repetition rate from our fiber CPA system, which were compressible to high fidelity pulses with a duration of 170 fs
Processing ultrafast optical signals in broadband telecom systems by means of cascaded quadratic nonlinearities
Get PDFQuadratic optical nonlinearities offer several attractive features for the implementation of ultra-fast, low-noise and transparent telecom devices. Technological progress has dramatically increased their efficiency, driving a steady move towards practical applications. In this talk we shall discuss the use of cascaded quadratic interactions in LiNbO3 integrated devices for pulse diagnostics, format conversion and signal regeneration in ultra-fast multi-wavelength telecom systems
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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