Search results for "Linea"
showing 10 items of 7724 documents
Polarisation attraction and incoherent modulation instability in optical fibers
2006
This thesis, entitled « Polarisation attraction and incoherent modulation instability in optical fibers », presents a theoretical and experimental study of two new processes from the nonlinear optic in optical fibers domain. We introduce in the first chapter some theoretical notions useful for the comprehension of this work. Then, we demonstrate in the second chapter that it is possible to generate some modulation instability in optical fibers using a partially coherent optical beam. We highlight and observe the main properties of the phenomenon. We study the polarisation attraction in isotropic fibers process in the third chapter. Our work proves the existence of the phenomenon, and permit…
Even harmonic pulse train generation by cross-polarization-modulation seeded instability in optical fibers
2012
International audience; We show that, by properly adjusting the relative state of polarization of the pump and of a weak modulation, with a frequency such that at least one of its even harmonics falls within the band of modulation instability, one obtains a fully modulated wave at the second or higher even harmonic of the initial modulation. An application of this principle to the generation of a 80-GHz optical pulse train with high extinction ratio from a 40-GHz weakly modulated pump is experimentally demonstrated using a nonzero dispersion shifted fiber in the telecom C band.
Signal processing in photonic crystals and nanostructures
2006
International audience; Optical devices employing photonic crystals and novel nanostructure materials may exhibit useful properties for applications to all-optical signal processing. In this work we analyze as a first example four-wave mixing of polarized beams in photonic crystal fibers. We show that by properly tuning the pump wavelength and the linear dispersion properties of the fiber one may obtain broadband parametric amplification and frequency conversion. Next we consider the in-line periodic amplification of short optical pulses by means of quantum-dot semiconductor optical amplifiers. We show by numerical simulations that pattern-free amplification of a 40 Gbit/s soliton signal at…
NONLINEAR OPTICS Nonlinear virtues of multimode fibre
2015
The finding that multimode optical bres support a rich and complex mix of spatial and temporal nonlinear phenomena could yield a plethora of promising applications.
Long-transient conoscopic pattern technique
1999
0038-1098; Recent results on laser induced anisotropy in terbium gallium garnet are extended to the dynamic regime. We observed that the characteristic conoscopic pattern formation time presents a quadratic dependence on the beam size. The observed pattern intensity is accounted for by a simple analytical formula. The transient refractive index change due to thermal stress in the terbium gallium garnet is determined. (C) 1999 Elsevier Science Ltd. All rights reserved.
Stability, electronic structure, and optical properties of protected gold-doped silver Ag29−xAux (x = 0–5) nanoclusters
2017
In this work, we used density functional theory (DFT) and linear response time-dependent DFT (LR-TDDFT) to investigate the stability, electronic structure, and optical properties of Au-doped [Ag29-xAux(BDT)12(TPP)4]3- nanoclusters (BDT: 1,3-benzenedithiol; TPP triphenylphosphine) with x = 0-5. The aim of this work is to shed light on the most favorable doped structures by comparing our results with previously published experimental data. The calculated relative energies, ranging between 0.8 and 10 meV per atom, indicate that several doped Ag29-xAux nanoclusters are likely to co-exist at room temperature. However, only the Au-doped [Ag29-xAux(BDT)12(TPP)4]3- nanoclusters that have direct bon…
Optimal Spectral Wavelengths for Discriminating Orchard Species Using Multivariate Statistical Techniques
2019
Sustainable management of orchard fields requires detailed information about the tree types, which is a main component of precision agriculture programs. To this end, hyperspectral imagery can play a major role in orchard tree species mapping. Efficient use of hyperspectral data in combination with field measurements requires the development of optimized band selection strategies to separate tree species. In this study, field spectroscopy (350 to 2500 nm) was performed through scanning 165 spectral leaf samples of dominant orchard tree species (almond, walnut, and grape) in Chaharmahal va Bakhtiyari province, Iran. Two multivariable methods were employed to identify the optimum wavelengths:…
Elämänasenteiden ja -odotusten yhteys fyysiseen toimintakykyyn myöhemmällä iällä
2017
Tämän pro gradu -tutkielman tarkoituksena oli selvittää, miten myöhäiskeski-iän elämänasenteet ja -odotukset ovat yhteydessä fyysiseen toimintakykyyn myöhemmällä iällä. Lisäksi tarkasteltiin, ovatko elämänasenteet ja -odotukset yhteydessä fyysiseen toimintakykyyn vielä silloinkin, kun otetaan huomioon muut tunnetut toimintakyvyn riskitekijät, kuten ikä, sukupuoli, sosioekonominen asema ja koettu terveys. Tutkielman aineistona käytettiin Helsingin syntymäkohorttitutkimuksen (The Helsinki Birth Cohort Study) aineistoa vuosilta 2001–2011. Tutkimukseen osallistui 469 miestä ja 604 naista eli yhteensä 1073 tutkittavaa. Osanottajien keski-ikä vuonna 2001 oli noin 61 vuotta. Elämänasenteisiin liit…
Fundamentos de Optimización Matemática en Economía
1999
La optimización matemática es un área dentro de las matemáticas que se encarga de la elección de la mejor alternativa de entre las posibles para un problema formulado en términos matemáticos. Este área de las matemáticas es muy amplia, debido a la diversidad de situaciones que se pueden plantear y a las distintas maneras de enfocar la resolución del problema. El presente texto, en la medida que pretende ser una herramienta para el análisis económico, se centra en la programación no lineal y en los métodos analíticos de resolución de esos problemas. Por tanto, el objetivo es proporcionar al lector los conocimientos básicos y avanzados de optimización matemática que destacan por su aplicabili…
PRELIMINARY ANALYSES FROM A HOSPITAL BASED STUDY ON 3154 WESTERN SICILIAN PATIENTS WITH ORAL MUCOSAL LESIONS
2010
Objectives: Diagnosis of the wide variety of lesions that occur in the oral cavity is an essential part of dental practice. The objective of this study was to explore the demographic and behavioural profiles of patients affected by oral cavity diseases on a wide spectrum. Methods: Demographic and behavioural data of 3154 patients with at least one oral cavity disease among those consecutively visited between 2004 and 2009 at the Unit of Oral Medicine, were recorded: gender, age, smoking status, alcohol consumption, drugs use. Analysis was restricted to the eleven more frequent oral cavity diseases. Firstly, Multiple Correspondence Analysis (MCA) was applied as a descriptive tool to geometri…