Search results for "Linear"
showing 10 items of 7165 documents
Counter-propagating difference frequency mixing in diamond with terahertz waves
2013
We investigate four-wave mixing between terahertz and optical pulses in diamond. We observe the occurrence of sum and difference frequency generation, with the latter being phase-matched for terahertz pulses counter-propagating to the optical field.
The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation
2010
We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical difference frequency generation, when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon-absorption terms, we have been able to plot universal charts for phase matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date, in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conver…
Tapered Two-Wire Waveguide for Time-Domain Integration of Broadband Terahertz Pulses
2021
We show the time-domain integration of terahertz pulses achieved in a sub-wavelength, tapered two-wire waveguide. Both simulation and experimental results prove the time integration functionality of this waveguide topology.
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.
Spatio-temporal control of ultra-short pulses by using diffractive optical elements
2012
Diffractive optical elements (DOEs) have shown their applicability to control the spatio-temporal characteristics of ultra-short laser pulses. DOEs can provide high efficiency, compactness, very low material dispersion and, when implemented with spatial light modulators, real-time pulse engineering. In this communication, we report management of temporal and spectral profiles of ultra-short pulses by means of a quasi-direct space-to-time (QDST) pulse shaper. Moreover, we present spatio-temporal control, including dispersion compensation, by DOEs, and applications for activating nonlinear processes. On the other hand, we have achieved complete spatial control of ultra-short pulses, overcomin…
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
Switching synchronization in one-dimensional memristive networks: An exact solution.
2017
We study a switching synchronization phenomenon taking place in one-dimensional memristive networks when the memristors switch from the high- to low-resistance state. It is assumed that the distributions of threshold voltages and switching rates of memristors are arbitrary. Using the Laplace transform, a set of nonlinear equations describing the memristors dynamics is solved exactly, without any approximations. The time dependencies of memristances are found, and it is shown that the voltage falls across memristors are proportional to their threshold voltages. A compact expression for the network switching time is derived.
Polarizabilities of small annulenes from Cholesky CC2 linear response theory
2004
Using recently developed algorithms based on Cholesky decomposition of two-electron integrals to compute response properties at the correlated level, the static and dynamic (at 589 nm) polarizabilities of [4n + 2]-annulenes (n = 1, 2, 3, 4) have been calculated. The results show that the perpendicular component increases along the series linearly with the number of double bonds. The in-plane static polarizability is also increasing linearly with the area of the aromatic ring in the case of the delocalized species. However, linearity is lost for the localized conformations and for the dynamic polarizability. (C) 2004 Elsevier B.V. All rights reserved.
Probing ultrafast thermalization with field-free molecular alignment
2012
International audience; The rotation-translation thermalization of CO2 gas is investigated 500 ps after its preheating by a nonresonant short and intense laser pulse. The temperature of thermalization is optically determined with two additional short laser pulses enabling a field-free molecular alignment process and its probing, respectively. The measurements are performed for various intensities of the preheat pulse, leading to the observation of different temperatures which are in very good agreement with classical molecular dynamics simulations. The results can be regarded as a step towards real-time tracking of ultrafast relaxation pathways in molecular motion.
Dynamics of mean-field spin models from basic results in abstract differential equations
1992
The infinite-volume limit of the dynamics of (generalized) mean-field spin models is obtained through a direct analysis of the equations of motion, in a large class of representations of the spin algebra. The resulting dynamics fits into a general framework for systems with long-range interaction: variables at infinity appear in the time evolution of local variables and spontaneous symmetry breaking with an energy gap follows from this mechanism. The independence of the construction of the approximation scheme in finite volume is proven. © 1992 Plenum Publishing Corporation.