Search results for "Statistical physics"
showing 10 items of 1402 documents
Phase evolution of Peregrine-like solitons in nonlinear fiber optics
2019
Optical fiber systems are well-known to provide convenient platforms in which one may investigate a large variety of fascinating fundamental nonlinear coherent structures such as solitons or self-similar patterns. Interestingly, one of the major conclusions of the studies dealing with extreme-value fluctuations is that the temporal and spectral characteristics of localization processes can be well described in terms of solitons over finite background and in particular in terms of Peregrine soliton (PS) [1]. Whereas the longitudinal evolution of the temporal and spectral intensity of the PS have been characterized in detail [2], much less attention has been experimentally devoted to the evol…
Universal spectral dynamics of modulation instability : theory, simulation, experiment
2011
A central process of nonlinear fibre optics is modulation instability (MI), where weak perturbations on a continuous wave are amplified to generate a parametric cascade of spectral sidebands. Although studied for many years, it has only been recently appreciated that MI dynamics can be described analytically by Akhmediev breather (AB) solutions to the nonlinear Schrodinger equation (NLSE) [1]. This has led to important results, including the first observation of the Peregrine Soliton [2]. AB theory has also shown that the spectral amplitudes at the peak of the MI gain curve yield a characteristic log-triangular spectrum, providing new insight into the initial phase of supercontinuum generat…
Stationary and pulsating dissipative light bullets from a collective variable approach
2009
A collective variable approach is used to map domains of existence for (3+1) -dimensional spatiotemporal soliton solutions of a complex cubic-quintic Ginzburg-Landau equation. A rich variety of evolution behaviors, which include stationary and pulsating dissipative soliton dynamics, is revealed. Comparisons between the results obtained by the semianalytical approach of collective variables, and those obtained by a purely numerical approach show good agreement for a wide range of equation parameters. This also demonstrates the relevance of the semianalytical method for a systematic search of stability domains for spatiotemporal solitons, leading to a dramatic reduction of the computation tim…
Real-time measurements of spontaneous breathers and rogue wave events in optical fibre modulation instability
2016
Modulation instability is a fundamental process of nonlinear science, leading to the unstable breakup of a constant amplitude solution of a physical system. There has been particular interest in studying modulation instability in the cubic nonlinear Schrödinger equation, a generic model for a host of nonlinear systems including superfluids, fibre optics, plasmas and Bose–Einstein condensates. Modulation instability is also a significant area of study in the context of understanding the emergence of high amplitude events that satisfy rogue wave statistical criteria. Here, exploiting advances in ultrafast optical metrology, we perform real-time measurements in an optical fibre system of the u…
Impact of a temporal sinusoidal phase modulation on the optical spectrum
2018
International audience; We discuss the effects of imparting a temporal sinusoidal phase modulation to a continuous wave on the frequency spectrum. While a practical analytical solution to this problem already exists, we present here a physical interpretation based on interference processes. This simple model will help the students better understand the origin of the oscillatory structure that can be observed in the resulting spectrum and that is characteristic of Bessel functions of the first kind. We illustrate our approach with an example from the field of optics.
Optimal control of an inhomogeneous spin ensemble coupled to a cavity
2018
We apply optimal control techniques to an inhomogeneous spin ensemble coupled to a cavity. A general procedure is proposed for designing the control strategies. We numerically show the extent to which optimal control fields robust against system uncertainties help enhancing the sensitivity of the detection process. The parameters of the numerical simulations are taken from recent Electron Spin Resonance experiments. The low and high cooperativity regimes are explored.
Laser Pulse Effects in Two-level Systems Driven by Coherent and Fluctuating Radiation Fields
1988
Abstract We reconsider the problem of a two-level system interacting with a radiation field in order to study some new features suggested by the actual experimental conditions. Pulse shape and duration effects are included in the formalism and the counter-rotating terms are retained. The criterion of validity of the rotating wave approximation (RWA) for pulsed fields is investigated; generalizing results well known in RWA, we establish some new formal results, including non-RWA contributions to all orders and for any pulse shape. The analysis is then carried out for fluctuating fields, by developing a method based on the theory of multiplicative stochastic differential equations. For short …
Statistical description of soliton clustering in fiber lasers with slow-gain dynamics
2014
We demonstrate theoretically that the dynamic clustering of solitons observed in a variety of experiments are due to the initial phase and position of interacting solitons with the slow gain dynamics of the fiber laser.
Electric conduction in semiconductors: a pedagogical model based on the Monte Carlo method
2008
We present a pedagogic approach aimed at modelling electric conduction in semiconductors in order to describe and explain some macroscopic properties, such as the characteristic behaviour of resistance as a function of temperature. A simple model of the band structure is adopted for the generation of electron–hole pairs as well as for the carrier transport in moderate electric fields. The semiconductor behaviour is described by substituting the traditional statistical approach (requiring a deep mathematical background) with microscopic models, based on the Monte Carlo method, in which simple rules applied to microscopic particles and quasi-particles determine the macroscopic properties. We …
Dynamics of Dense Polymers: A Molecular Dynamics Approach
1988
The physics of polymeric materials[1, 2] is one of the most challenging problems in condensed matter physics today. It is a problem of great interest both from a fundamental viewpoint and for their various technical applications. In addition to theortical and experimental approaches, computer simulations[3–11] have played an important role in our present understanding of polymers. For static properties Monte Carlo methods have been widely used and give excellent results for static critical exponents. To investigate dynamic properties three different methods — Monte Carlo (MC)[3–7], molecular dynamics (MD)[8, 9] and Brownian dynamics methods[10] — have been used. Detailed microscopic dynamic…