1,721,233 research outputs found
Spatio-temporal extreme waves in optical fiber systems
No full textWe overview recent progress on complex optical rogue wave generation phenomena.
Multicomponent deterministic rogue waves are predicted both in the anomalous [1]
and normal [2] dispersion regime of birefringent optical fibers. Experiments led to the
observation of dark hole polarization rogue waves in a randomly birefringent fiber [3].
The generation of rogue waves in different multicomponent wave systems is
associated with the presence of baseband modulation instability [4,5].
Multicomponent rogue waves are also generated by three-wave coupling between an
optical pump and a Stokes wave mediated by an acoustic wave [6], and between
counter-propagating waves in a nonlinear Bragg grating [7]. Dissipative rogue waves
are closely linked with the onset of turbulence in mode-locked [8,9] and Raman fiber
lasers [10], and in passive coherently pumped cavities [11]. Hydrodynamic rogue
waves also occur in the regime of weak normal dispersion [12-14]. A new frontier for
rogue waves studies is provided by multimode fiber systems, where complex spatiotemporal
extreme wave phenomena have recently been discovered [15-18].
References
[1] F. Baronio et al., Phys. Rev. Lett. 109, 044102 (2012)
[2] F. Baronio et al., Phys. Rev. Lett. 113, 034101 (2014)
[3] B. Frisquet et al., Scientific Reports 6, 20785 (2016)
[4] F. Baronio et al., Phys. Rev. A 91, 033804 (2015)
[5] B. Frisquet et al., Phys. Rev. A 92, 053854 (2015)
[6] S. Chen et al., Phys. Rev. A 92, 033847 (2015)
[7] A. Degasperis et al., Phys. Lett. A 379, 1067 (2015)
[8] S. Wabnitz, Opt. Lett. 39, 1362 (2014)
[9] C. Lecaplain et al., Phys. Rev. A 89, 063812 (2014)
[10] S. Sugavanam et al., Laser & Photonics Rev. 9, L35 (2015)
[11] T. Hansson and S. Wabnitz, J. Opt. Soc. Am. B 32, 1259 (2015)
[12] S. Wabnitz et al., Phys. Lett. A 377, 932 (2013)
[13] S. Wabnitz, J. of Optics 15, 064002 (2013)
[14] B. Varlot et al., Optics Letters 38, 3899 (2013)
[15] A. Picozzi, et al., Nature Photonics 9, 289 (2015)
[16] L.G. Wright et al., Phys. Rev. Lett. 115, 223902 (2015)
[17] K. Krupa et al., ArXiv 1602.04991 (2016)
[18] K. Krupa et al., ArXiv 1603.02972 (2016
Nonlinear optical waves in disordered ferroelectrics
Full text linkThis thesis describes an experimental, numerical and theoretical investigation of nonlinear optical phenomena in disordered photorefractive ferroelectrics in proximity of their phase-transition temperature. The work addresses different physical issues that find in nonlinear optics a common fertile research arena and are closely related to each other in the considered systems. Nonlinear wave dynamics in the spatial domain, where self-interaction of propagating waves generally results into non-spreading localized wavepackets such as spatial solitons, is extended in photorefractive ferroelectrics to non-equilibrium regimes characterized by stochastic instabilities and large material fluctuations. We discover the emergence of rogue waves, localized perturbations of abnormal intensity, whose understanding is challenging in various physical contexts and resides in the general problem of long-tail statistical distributions in complex systems. We identify their origin in spatiotemporal soliton dynamics in a saturable nonlinearity which can support scale-invariant waveforms. Properties and predictability of the observed extreme events are investigated, and, in particular, we demonstrate their active control through the spatial incoherence scale of the optical field. Moreover, we report how their emergence is sustained by turbulent transitions to an incoherent and disordered optical state triggered by modulational instability. The onset of strong turbulence for propagating optical waves has remained unobserved up to now and our results demonstrate a new experimental setting for its study. When the functional form of the nonlinearity is turned into a nonlocal one due
to diffusive fields, this setting also exploits photonics to address fundamental physical problems and access to otherwise hidden phenomena. The natural spreading of waves during propagation, representing the wavelength-defined ultimate limit to spatial
resolution, can be eliminated and reversed leading to diffraction cancellation and anti-diffraction of light. Since these behaviors on modifying the nature of underlying Schrödinger equation, we are the first to demonstrate how nonlinearity can make the spatial light distribution behave as the wavefunction of a quantum particle with negative mass. All these findings have roots in the nonlinear optical response of critical disordered ferroelectric crystals, which are also extremely interesting from the condensed matter point of view. In fact, competition of different microscopic structural phases and the associated polar-domain dynamics at the nanoscale results into non-ergodic dipolar-glass behaviors giving giant responses such as giant polarization, piezoelectricity and electro-optic effect. Disordered ferroelectrics crystals are investigated electro-optically across their ferroelectric phase-transition, where we report the observation of an anomalous electro-optic effect compatible with ultracold dipolar reorientation. In compounds presenting spatial inhomogeneity in their chemical composition, we discover a new ferroelectric phase of matter in which polar domains spontaneously coordinate into a mesoscopic coherent polarization super-crystals. This phase mimics standard solid-state structures but on scales that are thousands of times larger and represent the first spontaneous three-dimensional photonic crystal
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
Bandwidth Limits of Soliton Transmission with Sliding Filters
No full textThe limitations to the maximum transmission capacity in a long distance soliton transmission system with sliding guiding filters are studied. Shown is that sliding the center frequency of the filters may substantially stabilize the soliton even in the case of strong resonance overlap with the radiation that originates from the periodic amplification. This permits a considerable reduction of both the minimum pulse width and pulse-to-pulse separation in the transmission
Chirped RZ communication links in presence of strong dispersion management and lumped gaussian filters
No full textCatania - Itali
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
Generazione di impulsi solitonici stabili in una cavità laser non risonante in fibra all'Erbio
No full textAppropriate 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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