Dynamical properties of liquid Al near melting. An orbital-free molecular dynamics study

The static and dynamic structure of liquid Al is studied using the orbital free ab-initio molecular dynamics method. Two thermodynamic states along the coexistence line are considered, namely T = 943 K and 1323 K for which X-ray and neutron scattering data are available. A new kinetic energy functional, which fulfills a number of physically relevant conditions is employed, along with a local first principles pseudopotential. In addition to a comparison with experiment, we also compare our ab-initio results with those obtained from conventional molecular dynamics simulations using effective interionic pair potentials derived from second order pseudopotential perturbation theory.Comment: 15 pages, 12 figures, 2 tables, submitted to PR

Nearly 100 Nm Bandwidth Of Flat Gain With A Double-pumped Fiber Optic Parametric Amplifier

We demonstrate double-pumped fiber-optical parametric amplifiers with flat and broadband gain spectrum. Using specially fabricated highly non-linear fibers having low variations of the zero-dispersion wavelength and low PMD we obtain flat gain (23.5±1dB) over ∼95nm. ©2007 Optical Society of America.Hansryd, J., Andrekson, P.A., Westlund, M., Li, J., Hedekvist, P.O., Fiber-based optical parametric amplifiers and their applications (2002) IEEE J. Sel. Top. Quantum. Electron, 10, pp. 506-520Gao, M.Y., Jiang, C., Hu, W., Wang, J., Two-pump fiber optical parametric amplifiers with three sections fiber allocation (2006) Optics and Laser Technol, 38, pp. 186-191Yaman, F., Lin, Q., Agrawal, G.P., Impact of dispersion fluctuations in dual-pump fiber-optic parametric amplifiers (2004) IEEE Phot. Tech. Lett, 16, pp. 1292-1294Radic, S., McKinstrie, C.J., Jopson, R.M., Centanni, J.C., Lin, Q., Agrawal, G.P., Record performance of parametric amplifier constructed with highly nonlinear fibre (2003) Electron. Lett, 39, pp. 838-839Chavez Boggio, J.M., Marconi, J.D., Fragnito, H.L., Double-pumped fiber optical parametric amplifier with flat gain over 47-nm bandwidth using a conventional dispersion-shifted fiber (2005) IEEE Photon. Technol. Lett, 17, pp. 1842-1844Chavez Boggio, J.M., Marconi, J.D., Fragnito, H.L., Bickham, S.R., Mazzali, C., Broadband and low ripple double-pumped fiber optical parametric amplifier and wavelength converters using HNLF (2006) Proc. Optical Amplifiers and their Applications, , Whistler, Canada, Jun

Two-pump Fiber Opas With Flat Gain Over 100 Nm Bandwidth

[No abstract available]5758Marhic, M.E., (1996) Opt. Lett, 21, pp. 1354-1356Nakanishi, T., (2006) Proc. Optical Fiber Communication (OFC) conference, , paper OtuH7, AnaheimM. Hirano et al., in Proc. European Conference Optical Communication (ECOC), PD paper Th 4.4.4, Glasgow, Scotland, 2005Yaman, F., (2004) IEEE Photon. Technol. Lett, 16, pp. 1292-1294Radic, S., (2003) Electron. Lett, 39, pp. 838-839Radic, S., (2004) Proc. of Optical Fiber Communication Conference, OFC, , Paper TuC4Chavez Boggio, J.M., (2007) Opt. Exp, 15, pp. 5288-583

Broadband And Low Ripple Double-pumped Parametric Amplifier And Wavelength Converter Using Hnlf

We report on a double-pumped fiber optical parametric amplifier and wavelength converter with flat gain (35.0 ± 1.5 dB) over 71 nm using a highly non-linear dispersion shifted fiber with low longitudinal variation of the zero dispersion wavelength (< ±0.1 nm). © 2006 Optical Society of America.Hansryd, J., Andrekson, P.A., Westlund, M., Li, J., Hedekvist, P.O., Fiber-based optical parametric amplifiers and their applications (2002) IEEE J. Sel. Top. Quantum. Electron., 10, pp. 506-520Chavez Boggio, J.M., Guimarães, A., Callegari, F.A., Marconi, J.D., Fragnito, H.L., Q penalties due to pump phase modulation and pump RIN in fiber optical parametric amplifiers with non uniform dispersion (2005) Opt. Comm., 249, pp. 451-472Chavez Boggio, J.M., Tenenbaum, S., FWM induced changes in the noise spectrum after propagation in optical fibers (2001), WD24, Optical Fiber Conference, AnaheimYaman, F., Lin, Q., Agrawal, G.P., Effects of polarization-mode dispersion in dual-pump fiber-optic parametric amplifiers (2004) IEEE Phot. Tech. Lett., 16, pp. 431-43

Localized States in Discrete Nonlinear Schr\"{o}dinger Equations

A new 1-D discrete nonlinear Schr\"{o}dinger (NLS) Hamiltonian is introduced which includes the integrable Ablowitz-Ladik system as a limit. The symmetry properties of the system are studied. The relationship between intrinsic localized states and the soliton of the Ablowitz-Ladik NLS is discussed. It is pointed out that a staggered localized state can be viewed as a particle of a {\em negative} effective mass. It is shown that staggered localized states can exist in the discrete dark NLS. The motion of localized states and Peierls-Nabarro pinning are studied.Comment: LaTeX file. Two postscript figure file

Confinement of discrete breathers in inhomogeneously profiled nonlinear chains

We investigate numerically the scattering of a moving discrete breather on a pair of junctions in a Fermi-Pasta-Ulam chain. These junctions delimit an extended region with different masses of the particles. We consider (i) a rectangular trap, (ii) a wedge shaped trap, and (iii) a smoothly varying convex or concave mass profile. All three cases lead to DB confinement, with the ease of trapping depending on the profile of the trap. We also study the collision and trapping of two DBs within the profile as a function of trap width, shape, and approach time at the two junctions. The latter controls whether one or both DBs are trapped

Dynamical properties of discrete breathers in curved chains with first and second neighbor interaction

We present the study of discrete breather dynamics in curved polymerlike chains consisting of masses connected via nonlinear springs. The polymer chains are one dimensional but not rectilinear and their motion takes place on a plane. After constructing breathers following numerically accurate procedures, we launch them in the chains and investigate properties of their propagation dynamics. We find that breather motion is strongly affected by the presence of curved regions of polymers, while the breathers themselves show a very strong resilience and remarkable stability in the presence of geometrical changes. For chains with strong angular rigidity we find that breathers either pass through bent regions or get reflected while retaining their frequency. Their motion is practically lossless and seems to be determined through local energy conservation. For less rigid chains modeled via second neighbor interactions, we find similarly that chain geometry typically does not destroy the localized breather states but, contrary to the angularly rigid chains, it induces some small but constant energy loss. Furthermore, we find that a curved segment acts as an active gate reflecting or refracting the incident breather and transforming its velocity to a value that depends on the discrete breathers frequency. We analyze the physical reasoning behind these seemingly general breather properties

Interaction of a discrete breather with a lattice junction

We study the scattering of a moving discrete breather (DB) on a junction in a Fermi-Pasta-Ulam chain consisting of two segments with different masses of the particles. We consider four distinct cases: (i) a light-heavy (abrupt) junction in which the DB impinges on the junction from the segment with lighter mass, (ii) a heavy-light junction, (iii) an up mass ramp in which the mass in the heavier segment increases continuously as one moves away from the junction point, and (iv) a down mass ramp. Depending on the mass difference and DB characteristics (frequency and velocity), the DB can either reflect from, or transmit through, or get trapped at the junction or on the ramp. For the heavy-light junction, the DB can even split at the junction into a reflected and a transmitted DB. The latter is found to subsequently split into two or more DBs. For the down mass ramp the DB gets accelerated in several stages, with accompanying radiation (phonons). These results are rationalized by calculating the Peierls-Nabarro barrier for the various cases. We also point out implications of our results in realistic situations such as electron-phonon coupled chains