Search results for "Nonlinear system"

Random bit generation through polarization chaos in nonlinear optical fibers

2017

Nowadays, cryptographic applications are becoming of paramount importance in order to guarantee ultimately secure communications. Performances of classical and quantum key distribution and encryption algorithms are strongly dependent on the used Random Number Generator (RNG). A good RNG must produce unpredictable, unreproducible and unbiased sequences of numbers. For this reason, many true random number generators relying on chaotic physical phenomena, such as chaotic oscillations of high-bandwidth lasers [1, 2] or polarization chaos from a VCSEL diode [3], have been developed. In this work, we propose a RNG implementation based on a different physical mechanism than the ones previously use…

Nonlinear repolarization dynamics in optical fibers: transient polarization attraction

2011

International audience; In this work, we present a theoretical and experimental study of the response of a lossless polarizer to a signal beam with a time-varying state of polarization (SOP). By lossless polarizer, we mean a nonlinear conservative medium (e.g., an optical fiber) that is counterpumped by an intense and fully polarized pump beam. Such a medium transforms input uniform or random distributions of the SOP of an intense signal beam into output distributions that are tightly localized around a well-defined SOP. We introduce and characterize an important parameter of a lossless polarizer--its response time. Whenever the fluctuations of the SOP of the input signal beam are slower th…

Soft proton exchanged channel waveguides in congruent lithium tantalate for frequency doubling

2010

We report on stable optical waveguides fabricated by soft-proton exchange in periodically-poled congruent lithium tantalate in the a-phase. The channel waveguides are characterized in the telecom wavelength range in terms of both linear properties and frequency doubling. The measurements yield a nonlinear coefficient of about 9.5pm/V, demonstrating that the nonlinear optical properties of lithium tantalate are left nearly unaltered by the process. (C) 2010 Optical Society of America

Nonlinear Resonance Effects in Pattern Formation in Optical Parametric Oscillators

2005

Linear and nonlinear optical properties of some organoxenon derivatives

2007

We employ a series of state-of-the-art computational techniques to study the effect of inserting one or more Xe atoms in HC2H and HC4H, on the linear and nonlinear optical (L&NLO) properties of the resulting compounds. It has been found that the inserted Xe has a great effect on the L&NLO properties of the organoxenon derivatives. We analyze the bonding in HXeC2H, and the change of the electronic structure, which is induced by inserting Xe, in order to rationalize the observed extraordinary L&NLO properties. The derivatives, which are of interest in this work, have been synthesized in a Xe matrix. Thus the effect of the local field (LF), due to the Xe environment, on the properties of HXeC2…

3D-2D dimensional reduction for a nonlinear optimal design problem with perimeter penalization

2012

A 3D-2D dimension reduction for a nonlinear optimal design problem with a perimeter penalization is performed in the realm of $\Gamma$-convergence, providing an integral representation for the limit functional.

Optimal tuning of tuned liquid column damper systems in random vibration by means of an approximate formulation

2014

Passive control devices are often added to slender and flexible systems in order to increase their structural safety. Several types of devices have been proposed in order to reduce the dynamic responses of different kind of structural systems. Among them, the tuned liquid column damper (TLCD) proved to be very effective in reducing vibration of various type of structures by means of a combined action which involves the motion of the liquid mass within the tube. The restoring force, in particular, is produced by the force of gravity acting on the liquid and the damping effect is generated by the hydrodynamic head losses that arise during the motion of the liquid inside the TLCD. Since the in…

Modelling and optimization of a passive structural control design for a spar-type floating wind turbine

2014

Abstract Compared with fixed-bottom installation, deep water floating wind turbine has to undergo more severe structural loads due to extra degrees of freedom. Aiming for effective load reduction, this paper deals with the evaluation of a passive structural control design for a spar-type floating wind turbine, and the proposed strategy is to install a tuned mass damper (TMD) into the spar platform. Firstly, a mathematical model for wind turbine surge-heave-pitch motion is established based on the D’Alembert’s principle of inertial forces. Then, parameter estimation is performed by comparing the outputs from the proposed model and the state-of-the-art simulator. Further, different optimizati…

Testing for non-linearity in an artificial financial market: a recurrence quantification approach

2004

Abstract In this paper, earlier work on testing for non-linear dynamics on realizations from an artificial financial market is extended in two ways. On the one hand, Hinich’s bispectral test and White’s neural network test are computed. On the other hand, a recently developed methodology to test for hidden structures in data, inherited from Physics, is successfully applied on the realizations of the artificial market. Results among alternative tests are compared.

Oscillation results for second-order nonlinear neutral differential equations

2013

Published version of an article in the journal: Advances in Difference Equations. Also available from the publisher at: http://dx.doi.org/10.1186/1687-1847-2013-336 Open Access We obtain several oscillation criteria for a class of second-order nonlinear neutral differential equations. New theorems extend a number of related results reported in the literature and can be used in cases where known theorems fail to apply. Two illustrative examples are provided.