Search results for "Names"
showing 10 items of 6843 documents
Collisional models in a nonperturbative approach
1992
Abstract A nonperturbative method set forth recently for handling quantum dynamics in the intermediate regime (far from either the sudden or the adiabatic limit) is applied to soluble two-state collisional models.
STABILITY AND SPECTRA OF SMALL 3He-4He CLUSTERS
2005
Diffusion Monte Carlo calculations have been systematically performed to analyze the stability of small mixed 3 He -4 He clusters, as well as their excitation spectra. The picture that emerges is that of systems with strong shell effects whose binding and excitation energies are essentially determined by the monopole properties of an effective Hamiltonian.
Driven harmonic oscillators in the adiabatic Magnus approximation
1993
The time evolution of driven harmonic oscillators is determined by applying the Magnus expansion in the basis set of instantaneous eigenstates of the total Hamiltonian. It is shown that the first-order approximation already provides transition probabilities close to the exact values even in the intermediate regime.
Extreme statistics in Raman fiber amplifiers : from experiments to analytical description
2010
International audience; We describe the concept of an all-fibered device that enables the optical magnification of the amplitude jitter of low-fluctuation pulse trains, facilitating the measurement of the statistical properties by usual photodiodes and electronic equipments. Taking advantage of a highly nonlinear fiber with anomalous dispersion followed by central optical bandpass filtering, we experimentally demonstrate an amplification of small-scale fluctuations by a factor 10.
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…
Double-seed stabilization of a continuum generated from fourth-order modulation instability
2013
Summary form only given. Modulation instability (MI) is a ubiquitous process in which a weak field is exponentially amplified through a balance between dispersive and nonlinear effects. In single-mode scalar optical fibers, the positive Kerr nonlinearity phase-mismatch can be compensated by anomalous second-order dispersion, a process known as MI2. But phase-matched solutions can also exist in normal second-order dispersion region, thanks to negative even higher-order terms [1]. This process, that we label MI4, gives rise to a pair of narrow sidebands widely detuned far from the pump. MI may grow spontaneously from broadband noise and is usually the main process involved in the early stages…
Dissipative Optical Breather Molecular Complexes
2020
We demonstrate different types of breathing soliton complexes in a mode-locked fibre laser: multi-breather molecules, and molecular complexes arising from the binding of two breather-pair molecules or a breather-pair molecule and a single breather.
Four-wave mixing control in the filamentation of ultrafast Bessel beams via longitudinal intensity-shaping
2017
International audience; Bessel beams exploit conical energy flow to yield near-uniform intensity along a line focus which has been shown to be extremely attractive for laser processing in dielectrics. At high power, however, the nonlinear Kerr effect is known to induce significant oscillations of the on-axis intensity which is deleterious for machining applications. Here, we show through theory and numerical modelling how this problem can be understood and overcome by appropriate spatial phase shaping of the input profile. Our results also solve the longstanding problem related to the nonlinear Bessel beam dynamics seen at an air-dielectric interface.
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…
Two-stage linear-nonlinear shaping of an optical frequency comb as rogue nonlinear-Schrödinger-equation-solution generator
2014
International audience; We report a wave generator of complex solutions of the nonlinear Schrödinger equation (NLSE) combining both intensity and phase spectral shaping of an initial optical frequency comb with subsequent nonlinear propagation in an optical fiber. We apply the explicit analytical form of the two-breather solutions of the NLSE as a linear spectral filter to shape ideal modulation of a continuous wave. The additional nonlinear propagation of the tailored wave provides experimental evidence of both the growth and decay of the fundamental second-order periodic breather solution. The temporal and spectral profiles of the higher-order breather are in excellent agreement with the …