0000000000018965
AUTHOR
P. Tchofo Dinda
showing 51 related works from this author
Modulational instability in fiber systems with periodic loss compensation and dispersion management
2003
In this paper we study modulational instability in a Kerr fiber taking into account the combined effects of periodic power variations and dispersion management. It is shown that periodic dispersion management and periodic amplification produce nonconventional MI sidebands which are essentially independent of each other. In addition, we show that the amplifier spontaneous emission noise tends to inhibit the growth of sidebands, for a sufficiently long propagation distance.
Oscillations of a highly discrete breather with a critical regime
2000
We analyze carefully the essential features of the dynamics of a stationary discrete breather in the ultimate degree of energy localization in a nonlinear Klein-Gordon lattice with an on-site double-well potential. We demonstrate the existence of three different regimes of oscillatory motion in the breather dynamics, which are closely related to the motion of the central particle in an effective potential having two nondegenerate wells. In given parameter regions, we observe an untrapped regime, in which the central particle executes large-amplitude oscillations from one to the other side of the potential barrier. In other parameter regions, we find the trapped regime, in which the central …
Collective variable theory for optical solitons in fibers
2000
We present a projection-operator method to express the generalized nonlinear Schrödinger equation for pulse propagation in optical fibers, in terms of the pulse parameters, called collective variables, such as the pulse width, amplitude, chirp, and frequency. The collective variable (CV) equations of motion are derived by imposing a set of constraints on the CVs to minimize the soliton dressing during its propagation. The lowest-order approximation of this CV approach is shown to be equivalent to the variational Lagrangian method. Finally, we demonstrate the application of this CV theory for pulse propagation in dispersion-managed optical fiber links.
Experimental demonstration of 160-GHz densely dispersion-managed soliton transmission in a single channel over 896 km of commercial fibers
2003
International audience; We experimentally demonstrate the first 160-GHz densely dispersion-managed soliton transmission in a single channel at 1550 nm over nearly 900 km using commercially available non-zero dispersion-shifted fibers. This performance has been achieved by using a 16 km-long recirculating loop configuration and an appropriate design of the dispersion map.
Analytical design of nonlinear optical loop mirrors for fiber-optic communication systems
2006
International audience; We propose an easy and efficient method for analytically designing nonlinear optical loop mirrors (NOLMs) for fiber-optic communication systems. This analytical design is based on a Taylor series expansion of the transfer function of the NOLM, from which highly stable dynamical regimes can be readily obtained for any desired pulse parameters. We present numerical simulations showing dramatically improved performances in a 160 Gb/s transmission system that incorporates the NOLMs designed analytically.
Analytical design of 160 Gbits/s densely dispersion-managed optical fiber transmission systems using Gaussian and raised cosine RZ ansätze
2004
We present an easy and efficient analytical method to design 160 Gbits/s densely dispersion-managed optical fiber transmission systems using Gaussian and raised cosine RZ ansatze.
Optimization of wavelength division multiplexing in N×160Gbit/s terrestrial transmission systems
2005
Abstract We analyze, from an engineering viewpoint, the prospects of an exploitable upgrade of terrestrial fiber systems based on standard monomode fiber and dispersion compensating units, for future N × 160 Gbit/s transmission systems. We show that dispersion swing, average dispersion and input pulse power are the key parameters that govern the system performances. We show that whenever the dispersion swing is arranged in a symmetrical setup and the compensation ratio is optimized accordingly, one may obtain a significant improvement of the transmission performances.
Modulational Instability and Stimulated Raman Scattering in Normally Dispersive Highly Birefringent Fibers
2001
Abstract The nonlinear interaction of two laser beams in normally dispersive highly birefringent optical fibers leads to a large set of fascinating physical effects such as modulational instability (MI) and stimulated Raman scattering (SRS). These two nonlinear phenomena have a positive role as a mechanism for the generation of short optical pulses and represent a drawback in fiber-optics transmissions. Indeed, we will show that an induced process of modulational instability may be exploited for the generation of THz train of vector dark solitons. The technique of frequency-resolved optical gating is used to completely characterize the intensity and phase of the dark soliton trains. On the …
Vibrations and oscillations of tri-soliton molecules in a mode-locked fiber laser
2018
We present numerical simulations highlighting internal oscillations and vibrations within tri-soliton molecules generated by a mode-locked fiber laser. We highlight major qualitative differences as compared to two-soliton molecules.
Demonstration of Stimulated-Raman-scattering suppression in optical fibers in a multifrequency pumping configuration
1999
International audience; We analyze the stimulated-Raman-scattering-(SRS) process induced by a linearly polarized multifrequency pump field in a normally dispersive single-mode fiber. We show, by theoretical analysis and numerical simulations, that the SRS process may be either controlled by switching all the generated Stokes radiations to the lowest-frequency pump or suppressed for all the frequency components of the pump field. The suppression process is achieved by an appropriate choice of the frequency separation between the pumps and a particular power distribution among the frequency components of the pump field. We present experimental spectra showing the effectiveness of this suppres…
Dark spatial solitary waves in a cubic-quintic-septimal nonlinear medium
2017
We consider the evolution of light beams in nonlinear media exhibiting nonlinearities up to the seventh order wherein the beam propagation is governed by the cubic-quintic-septimal nonlinear Schr\"odinger equation. An exact analytic solution that describes dark solitary wave propagation is obtained, based on a special ansatz. Unlike the well-known $\text{tanh}$-profile dark soliton in Kerr media, the present one has a functional form given in terms of ``${\text{sech}}^{2/3}$''. The requirements concerning the optical material parameters for the existence of this localized structure are discussed. This propagating solitary wave exists due to a balance among diffraction, cubic, quintic, and s…
Strong reduction of optimum pump power for efficient wave conversion in optical fibers with dual-frequency circularly polarized pump waves.
2002
We present experiments that show achievement of highly efficient generation of parametric sidebands in an optical fiber with dual-frequency, circularly polarized pump waves. An appropriate choice of the separation between the pump frequencies permits a strong reduction of the optimum power for highly efficient frequency conversion.
Suppression of soliton self-frequency shift by up-shifted filtering
2002
We propose an efficient method for suppressing the soliton self-frequency shift in high-speed transmission lines by means of up-shifted filters.
Impact of fourth-order dispersion in the modulational instability spectra of wave propagation in glass fibers with saturable nonlinearity
2010
We analyze the modulational instability (MI) of light waves in glass fibers with a local saturable nonlinear refractive index. We identify and discuss the salient features of the effect of the fourth order of the fiber dispersion, in the MI spectra. Particularly, we find that in fibers with negative sign of the second-order dispersion and positive sign of the fourth-order dispersion (FOD), the two existing types of MI processes, called processes of type I, which generate a single pair of sidebands, and processes of type II, which lead to two pairs of sidebands, become highly sensitive to the magnitude of the FOD, both quantitatively and qualitatively. We demonstrate the existence of a criti…
W-shaped, bright and kink solitons in the quadratic-cubic nonlinear Schrödinger equation with time and space modulated nonlinearities and potentials
2017
An extended non-linear Schrodinger equation (NLSE) combining quadratic and cubic Non-linearities, which appears as an approximate model of a relatively dense quasi-one-dimensional Bose–Einstein con...
Ultra-short pulse propagation in birefringent fibers—the projection operator method
2008
We examine the propagation of ultra-short optical light pulses in dispersion-managed birefringent fiber transmission systems, in which the pulse dynamics is governed by the coupled higher-order nonlinear Schrodinger equations with higher-order linear and nonlinear optical effects. We derive the equations of motion in terms of pulse parameters such as amplitude, temporal position, width, chirp, frequency and phase, using a projection operator method, and we obtain the spatial dynamical behavior of picosecond and femtosecond pulse parameters. From our detailed analysis, we show that the stimulated Raman scattering has a strong impact on the pulse dynamics.
Soliton collisions with shape change by intensity redistribution in mixed coupled nonlinear Schrodinger equations
2006
International audience; A different kind of shape changing (intensity redistribution) collision with potential application to signal amplification is identified in the integrable N-coupled nonlinear Schrodinger (CNLS) equations with mixed signs of focusing- and defocusing-type nonlinearity coefficients. The corresponding soliton solutions for the N=2 case are obtained by using Hirota's bilinearization method. The distinguishing feature of the mixed sign CNLS equations is that the soliton solutions can both be singular and regular. Although the general soliton solution admits singularities we present parametric conditions for which nonsingular soliton propagation can occur. The multisoliton …
Observation of modulational instability induced by velocity-matched cross-phase modulation in a normally dispersive bimodal fiber
2008
We demonstrate experimentally the existence of cross-phase-modulation-induced modulational instability in the absence of group-velocity mismatch between the interacting nonlinear dispersive waves. The experiment is performed by means of a normally dispersive isotropic bimodal fiber. The group-velocity mismatch between the fundamental and the first-order modes that constitute the two interacting waves is controlled by wavelength tuning. A strong power dependence of the modulational instability spectra is observed near the condition of group-velocity matching.
Motion of compactonlike kinks.
1999
We analyze the ability of a compactonlike kink (i.e., kink with compact support) to execute a stable ballistic propagation in a discrete Klein-Gordon system with anharmonic coupling. We demonstrate that the effects of lattice discreteness, and the presence of a linear coupling between lattice sites, are detrimental to a stable ballistic propagation of the compacton, because of the particular structure of the small-oscillation frequency spectrum of the compacton in which the lower-frequency internal modes enter in direct resonance with phonon modes. Our study reveals the parameter regions for obtaining a stable ballistic propagation of a compactonlike kink. Finally we investigate the interac…
Experimental observation of the generation of cutoff solitons in a discreteLCnonlinear electrical line
2014
We address the problem of supratransmission of waves in a discrete nonlinear system, driven at one end by a periodic excitation at a frequency lying above the phonon band edge. In an experimental electrical transmission line made of 200 inductance-capacitance LC cells, we establish the existence of a voltage threshold for a supratransmission enabling the generation and propagation of cut-off solitons within the line. The decisive role of modulational instability in the onset and development of the process of generation of cut-off solitons is clearly highlighted. The phenomenon of dissipation is identified as being particularly harmful for the soliton generation, but we show that its impact …
Suppression of stimulated Raman scattering in optical fibres by power-controlled multifrequency pumping
1999
International audience; We present a method for suppressing the stimulated Raman scattering process induced by a multifrequency pump field propagating in a normally dispersive single-mode fibre. The suppression process is completely achieved by suitably choosing the frequency separation between the pumps, as well as the power distribution among the frequency components of the pump field. The experimental spectra show the effectiveness of this suppression process for a dual-frequency pumping configuration.
Dispersion-managed electrical transmission lines
2009
International audience; We examine the ability of electrical pulses to execute a highly stable propagation in a special electrical network made of concatenated pieces of discrete electrical lines with alternately positive and negative signs of the second-order dispersion. We show that such networks, called dispersion-managed electrical lines, induce a pulse breathing phenomenon, that is a dynamical behaviour with alternate regimes of pulse broadening and compression. This breathing phenomenon, which prevents the pulse from broadening without bounds during propagation in the network is the most appealing feature of the technique of dispersion management developed in the last decade in the ar…
Transmission performance ofN×160 Gbit s−1densely dispersion-managed optical fibre systems
2005
We carefully analyse the feasibility of N × 160 Gbit s−1 ultra-long haul transmissions in densely dispersion-managed (DDM) fibre systems. By using a novel analytical approach, we design highly optimized configurations of DDM fibre systems. Transmission performances of the analytically designed DDM fibre systems are evaluated using numerical simulations. We show that single-channel transoceanic transmissions at 160 Gbit s−1 may be achievable in DDM fibre systems, whereas multi-channel transmissions result in dramatically poor performances.
Radiating and nonradiating behavior of hyperbolic-secant, raised-cosine, and Gaussian input light pulses in dispersion-managed fiber systems.
2005
We address the problem of optical light pulses, called dressed pulses, which do not match the stationary pulse profile of a dispersion-managed (DM) fiber system and we theoretically analyze the associated radiation. Comparing hyperbolic-secant, raised-cosine, and Gaussian pulse envelopes, we show that the general radiation figure is highly sensitive to the input pulse profile. As common general features for these pulse profiles, we find a rich variety of dynamical states that includes weak-, moderate-, and strong-radiation states, depending on the map strength of the DM fiber system. We demonstrate the existence of two intervals of map strengths where the emitted radiation is of considerabl…
Influence of parametric four-wave mixing effects on stimulated Raman scattering in bimodal optical fibers.
2007
We analyze stimulated Raman scattering in normally dispersive bimodal fibers under single-frequency pumping conditions. Experiments show that whenever the interacting nonlinear waves propagate in the LP(01) and LP(11) modes, a parametric four-wave mixing enters unavoidably into play in the wave-coupling behavior, which causes qualitatively different phenomena compared with the ordinary process of Raman scattering, such as the parametric suppression of the first-order Raman Stokes radiation.
Analytical design of soliton molecules in fibers
2016
We present an analytical method for designing fiber systems for a highly stable propagation of soliton molecules. This analytical design uses the variational equations of the soliton molecule to determine the parameters of the most suitable fiber system for any desired soliton, thus reducing dramatically the cost of the whole procedure of design, for both the appropriate fiber system and the desired soliton molecule.
Analytical design of dispersion-managed fiber system with map strength 1.65
2003
Abstract We present an easy analytical method for designing dispersion-managed fiber systems with map strength of 1.65, where the transmission lines have minimal pulse–pulse interactions.
Modulational instability in optical fibers with arbitrary higher-order dispersion and delayed Raman response
2006
International audience; We analyse modulational instability (MI) of electromagnetic waves in a large variety of optical fibers having different refractive-index profiles. For the normal-, anomalous-, and zero-dispersion regimes of the wave propagation, we show that whenever the second-order dispersion competes with higher-order dispersion (HOD), propagation of plane waves leads to a rich variety of dynamical behaviors. Most of the richness comes from the existence of critical behaviors, which include situations in which the HOD suppresses MI in the anomalous dispersion regime, and other situations in which the HOD acts in the opposite way by inducing non-conventional MI processes in the nor…
Wavelength conversion from 1.3 µm to 1.5 µm in single-mode optical fibres using Raman-assisted three-wave mixing
2000
International audience; We theoretically analyse the achievement of wide-range all-optical wavelength conversion of a 1.31 µm signal to an idler wave in the 1.5 µm spectral region by Raman-assisted three-wave mixing in single-mode optical fibres. Raman-assisted three-wave mixing allows efficient conversion on a large frequency detuning bandwidth while alleviating the need for stringent phase-matching conditions.
Energy-exchange collision of the Manakov vector solitons under strong environmental perturbations
2007
International audience; We use a collective-variable approach to study the dynamical behavior of vector solitons in the Manakov system under strong environmental perturbations induced by the fiber losses and a modified cross-phase modulation parameter. We identify and discuss the salient features associated with energy-exchange collisions of transmissional and reflectional types. Particularly, we find that such perturbations can induce important effects not only on fundamental soliton parameters such as the peak power, central position, width, chirp, and frequency, but also on the nature of the collision. Interestingly, we find that the perturbations lead to only a slight alteration of coll…
Analytical design of densely dispersion-managed optical fiber transmission systems with Gaussian and raised cosine return-to-zero Ansätze
2004
We propose an easy and efficient way to analytically design densely dispersion-managed fiber systems for ultrafast optical communications. This analytical design is based on the exact solution of the variational equations derived from the nonlinear Schrodinger equation by use of either a Gaussian or a raised-cosine (RC) Ansatz. For the input pulses of dispersion-managed optical fiber transmission systems we consider a RC profile and show that RC return-to-zero pulses are as effective as Gaussian pulses in high-speed (160-Gbits/s) long-distance transmissions.
Control processes for stimulated Raman scattering in optical fibers by dual-frequency pumping
1998
We pointed out that with nondegenerate frequency, and orthogonally polarized pump waves, the SRS may be suppressed in one of the axes of a highly birefringent fiber either via a four wave mixing (FWM) parametric process, or through the orthogonal component of the Raman nonlinearity.
Gap solitons and modulation instability in a dynamic Bragg grating with nonlinearity management
2008
International audience; We investigate the occurrence of modulation instability in systems in which a dynamic Bragg grating consists of alternating positive and negative Kerr coefficients. The dependence of modulation instability gain spectra over the perturbation wavenumber and system parameters is portrayed near and at the edges of the photonic band gap structure. Further, we demonstrate the generation of traveling gap solitons near the photonic band gap structure through the modulation instability
Modulational instability and generation of self-induced transparency solitons in resonant optical fibers
2009
International audience; We consider continuous-wave propagation through a fiber doped with two-level resonant atoms, which is described by a system of nonlinear Schrodinger-Maxwell-Bloch (NLS-MB) equations. We identify the modulational instability (MI) conditions required for the generation of ultrashort pulses, in cases of both anomalous and normal GVD (group-velocity dispersion). It is shown that the self-induced transparency (SIT) induces non-conventional MI sidebands. The main result is a prediction of the existence of both bright and dark SIT solitons in the anomalous and normal GVD regimes.
Vector Modulational Instabilities and Soliton Experiments
1999
In optical fibers, the interaction between nonlinear and dispersive effects leads to phenomena such as modulational instability (MI)[1, 2, 3, 4, 5, 6], in which a continuous or quasi-continuous wave undergoes a modulation of its amplitude or phase in the presence of noise or any other small perturbation. The perturbation can originate from quantum noise (spontaneous-MI) or from a frequency shifted signal wave (induced-MI). MI has been observed for the first time for a single pump wave propagating in a standard non birefringe.nt fiber (scalar MI)[7]. It has been shown that scalar MI only occurs when the group velocity dispersion (GVD) is negative (anomalous dispersion regime).
Modulational instability and critical regime in a highly birefringent fiber
1996
We report experimental observations of modulational instability of copropagating waves in a highly birefringent fiber for the normal dispersion regime. We first investigate carefully the system behavior by means of nonlinear Schr\"odinger equations and phase-matching conditions, and then, experimentally, we use two distinct techniques for observing MI (modulational instability) in the fiber; namely, the single-frequency copropagation, where two pump waves of identical frequency copropagate with orthogonal polarizations parallel to the two birefringence axes of the fiber, and the two-frequency copropagation, where the two polarized waves copropagate with different frequencies. In both cases …
Raman-assisted three-wave mixing of non-phase-matched waves in optical fibres: application to wide-range frequency conversion
2001
International audience; We analyse theoretically and experimentally the Raman-assisted parametric coupling between non-phase-matched waves propagating in normally dispersive single-mode fibres. We perform a careful analysis of the wave-coupling behaviour, which shows that scalar and vector three-wave mixing (TWM) interactions induce a relatively small periodic power flow between a central-frequency pump at frequency ω0 and a pair of up-shifted (anti-Stokes) and down-shifted (Stokes) sidebands at frequencies View the MathML source and View the MathML source, respectively. For sufficiently high pump powers, the stimulated Raman scattering enters into play, causing a unilateral transfer of ene…
Modulational instability in resonant optical fiber with higher-order dispersion effect
2010
International audience; The modulational instability (MI) of an electromagnetic wave in a resonant optical fiber with a two-level system is investigated. In the normal dispersion regime, we find the occurrence of nonconventional MI sidebands which are induced by the two-level resonant atoms. We also observe that the MI gain spectra are suppressed by the higher-order dispersion effect in the anomalous dispersion regime.
Generation of self-induced-transparency gap solitons by modulational instability in uniformly doped fiber Bragg gratings
2010
We consider the continuous-wave (cw) propagation through a fiber Bragg grating that is uniformly doped with two-level resonant atoms. Wave propagation is governed by a system of nonlinear coupled-mode Maxwell-Bloch (NLCM-MB) equations. We identify modulational instability (MI) conditions required for the generation of ultrashort pulses in both anomalous and normal dispersion regimes. From a detailed linear stability analysis, we find that the atomic detuning frequency has a strong influence on the MI. That is, the atomic detuning frequency induces nonconventional MI sidebands at the photonic band gap (PBG) edges and near the PBG edges. Especially in the normal dispersion regime, MI occurs w…
Theory of Raman effect on solitons in optical fibre systems: impact and control processes for high-speed long-distance transmission lines
2004
We examine the effects of stimulated Raman scattering on ultra-short pulses propagating in optical fibre systems. We demonstrate that the existing theories for the Raman-induced soliton self-frequency shift give consistent results in a restricted domain of pulse width which excludes important practical applications to high-speed soliton transmission systems. We present a general theory for the soliton self-frequency shift (SSFS), which applies to any pulse whose spectral bandwidth lies within the third-order telecommunication window. We also show that the harmful impact of the SSFS in high-speed long-distance transmission lines can be suppressed by use of filters whose central frequency is …
Optical Bistability and Switching in Oppositely Directed Coupler
2016
We report the optical bistability in two core oppositely directed coupler with negative index material channel. Using Langrangian variational method and Jacobi elliptic functions, we construct the solutions of the coupled nonlinear Schrodinger equations. The bistability arises due to the effective feedback mechanism as a result of opposite directionality of the phase velocity and energy flow in the negative index material channel. We report the various ways to control and manipulate the bistability threshold and hysteresis loop, which could be useful in the design and development of fast and low-threshold optical switches.
Analytical design of dispersion-managed fiber systems with S ≈ 1.65
2002
We present an easy analytical method for designing dispersion-managed fiber systems with map strength of 1.65, where the transmission lines have minimal pulse-pulse interactions.
Modulation instability scenario in negative index materials
2010
We present an investigation of the critical frequency windows permitting modulation instability in negative index materials. The principal motivation for our analysis stems from the impact of the inevitable presence of the effective dispersive magnetic permeability in addition to the effective dielectric permittivity determining the propagation model for ultrashort pulses in negative index materials. We emphasize the influence of nonlinear dispersion terms, arising out of the combinatorial effect of the dispersive permeability with the nonlinear polarization, over the MI phenomena, the outcome of its development achieved by using linear stability analysis. Gain spectrum investigation has be…
Dynamics of distorted and undistorted soliton molecules in a mode-locked fiber laser
2019
Recent developments in real-time ultrafast measurement techniques have enabled us to prove experimentally that soliton molecules execute internal motions with some aspects similar to those of a matter molecule. Such an analogy between the dynamics of soliton molecules and the dynamics of matter molecules is based on the assumption that the dissipative solitons constituting a molecule are rigid entities sharing a common profile. Whereas this assumption drastically reduces the number of degrees of freedom, it does not hold true in general and we demonstrate that it overlooks some of the essential dynamical features of the soliton molecule. We present a theoretical study based on the principle…
Design of dispersion-managed fiber systems for transmitting chirp-free Gaussian pulses
2008
International audience; We present a general method to analytically design a dispersion-managed (DM) fiber system for any desired fiber (dispersion, nonlinearity and losses) and pulse (width and energy) parameters. This analytical design allows one to transmit chirp-free Gaussian pulses (for very long distances) in almost all kinds of DM fiber systems that have appeared so far in the literature, including systems with dispersion map length greater, equal or shorter with respect to the amplification period.
Suppression of sideband frequency shifts in the modulational instability spectra of wave propagation in optical fiber systems
2007
International audience; In standard optical fibers with constant chromatic dispersion, modulational instability (MI) sidebands execute undesirable frequency shifts due to fiber losses. By means of a technique based on average-dispersion decreasing dispersion-managed fibers, we achieve both complete suppression of the sideband frequency shifts and fine control of the MI frequencies, without any compromise in the MI power gain.
Critical behavior with dramatic enhancement of modulational instability gain in fiber systems with periodic variation dispersion
2008
International audience; We analyze modulational instability (MI) of light waves in fiber systems with periodically varying dispersion. The dispersion fluctuation generates special waves, called nonconventional MI sidebands, which are shown to be highly sensitive to two fundamental system parameters. The first one is the average dispersion of the system. Surprisingly, the second parameter turns out to be the mean value of the dispersion coefficients of the two types of fibers of the system, which is then called “central dispersion.” These two parameters are used to control and optimize the MI process. In particular, we establish the existence of a critical region of the central dispersion at…
Optimized Hermite-Gaussian ansatz functions for dispersion-managed solitons
2001
Abstract By theoretical analysis, we show that the usual procedure of simply projecting the dispersion-managed (DM) soliton profile onto the basis of an arbitrary number of Hermite-gaussian (HG) polynomials leads to relatively accurate ansatz functions, but does not correspond to the best representation of DM solitons. Based on the minimization of the soliton dressing, we present a simple procedure, which provides highly accurate representation of DM solitons on the basis of a few HG polynomials only.
Radiating and non-radiating trains of light pulses in dispersion-managed optical fiber systems
2005
We show theoretically that the radiation picture of small trains of closely packed light pulses with Gaussian input profile, exhibits both some similar features and some fundamental differences when compared to the radiating behavior of a solitary pulse in a dispersion-managed optical fiber system. For small map strengths, the pulse trains strongly radiate away energy, and there, the total amount of radiated energy increases linearly as a function of the length of the pulse train. For large map strengths, the amount of radiated energy increases rather smoothly as a function of the length of the pulse train. We establish the existence of a map strength region, in which light pulses with init…
The melting behaviour of small silicon clusters
1994
Abstract We report an analysis of the melting behaviour of small silicon clusters interacting via a nonlinear interatomic potential with four-body terms. The analysis shows, by means of Monte Carlo and molecular dynamics simulations, that the small silicon clusters undergo, in a vacuum, structural changes from a solid rigid state to a liquid-like state. The melting temperature exhibits a strong variation with cluster size.
Ultra-short pulse propagation in birefringent fibers-the projection operator method
2008
International audience; We examine the propagation of ultra-short optical light pulses in dispersion-managed birefringent fiber transmission systems, in which the pulse dynamics is governed by the coupled higher-order nonlinear Schrödinger equations with higher-order linear and nonlinear optical effects. We derive the equations of motion in terms of pulse parameters such as amplitude, temporal position, width, chirp, frequency and phase, using a projection operator method, and we obtain the spatial dynamical behavior of picosecond and femtosecond pulse parameters. From our detailed analysis, we show that the stimulated Raman scattering has a strong impact on the pulse dynamics.