Acoustic activity effect for picosecond soliton-like pulses

A theoretical analysis is made of the acoustic activity for interfering picosecond acoustic soliton-like pulses of down to a single oscillation period. An analysis is made of the case where these pulses propagate parallel to an external magnetic field and one of the acoustic axes in a cubic crystal containing paramagnetic impurities having effective spin S = 1. Allowance is made for natural, magnetic (Faraday), and cross acoustic activity. This cross activity is caused by the significant spatial nonlocality of the spin-phonon interaction for such short pulses in crystals having no center of inversion in the presence of paramagnetic impurities. A system of nonlinear equations is obtained for the transverse and longitudinal components of the strain in the form of a coupling between the “differentiated” nonlinear Schrödinger equation (with nonlinearity after the derivative sign) and the Korteweg-de Vries equation which generalizes the known systems of long-short-wavelength resonance to the case where the slowly varying envelope approximation is not valid. An approximate solution of this system is used to study the structure of an elastic soliton-like pulse whose transverse component has a rotating plane of polarization, which propagates under conditions of nonlinear coupling with the longitudinal strain.     

Dynamics of frequency-modulated soliton-like pulses in an amplifier-modulator-compressor cascade

Specific features of the formation of frequency-modulated pulses with large peak powers in amplifier-modulator-compressor cascade schemes based on length-inhomogeneous optic fibers are considered. Optimum profiles of fiber parameters ensuring the most effective amplification and modulation of pico- and subpicosecond frequency-modulated pulses are proposed. It is established that the use of a cascade consisting of active (gain) and passive (modulating) fibers with optimized profiles of the normal group-velocity dispersion and mode area can ensure the formation of pico- and subpicosecond pulses with energies higher than 100 nJ and peak powers above 100 kW.     

Amplification of frequency-modulated soliton-like pulses in inhomogeneous optical waveguides with normal dispersion

The possibility of effective amplification of self-similar frequency-modulated pulses (FMPs) in longitudinally inhomogeneous active optical waveguides is studied. Peculiarities of the dynamics of parabolic pulses with a constant frequency modulation rate are considered. An optimal profile of variation of the group velocity dispersion was obtained in correspondence with optimal amplification of a similariton-like pulse. The use of FMPs in amplifying and longitudinally inhomogeneous optical waveguides with a correspondingly matched profile of normal dispersion of group velocities is shown to be capable of providing for an amplification of subpicosecond pulses up to energies above 1 nJ.     

Dynamics of frequency-modulated soliton-like pulses in a longitudinally inhomogeneous active optical waveguide

Conditions of the formation and amplification of frequency-modulated soliton-like pulses in longitudinally inhomogeneous active optical waveguides with anomalous dispersion of group velocities are studied. Group velocity dispersion profiles that are necessary for existence and amplification for active and passive optical waveguides are determined, and the dependences on the distance passed along the waveguide, duration, and chirp of the pulse are established.     

Propagation of a soliton-like pulse in a weakly nonlinear medium

Numerical methods are used to study the decay dynamics of a soliton-like signal in a medium with a cubic nonlinearity (using the nonlinear Shrödinger equation). We consider the influence of the initial pulse area, shape, and random modulations in its amplitude and phase on the decay process, as well as the effects of absorption and pumping in the medium.V. D. Kuznetsov Physico-Technical Institute, Tomsk State University, Siberia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 36–40, April, 1995.     

On the soliton-like dynamics of ultrashort acoustic pulses in a paramagnetic crystal

A system of nonlinear equations describing the dynamics of the longitudinal and transverse components of an acoustic pulse in a cubic crystal containing paramagnetic impurities has been obtained. On the basis of this system, the dynamics of a two-component ultrashort acoustic pulse propagating under the Zakharov-Benney resonance conditions has been analytically investigated.     

Dissipative structures in a continuous medium

Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 94–104, April, 1992.     

Parametric generation of soliton-like spin wave pulses in ferromagnetic thin-film ring resonators

Intense soliton-like spin wave pulses were parametrically generated in ferromagnetic thin-film ring resonators under the action of periodic parallel magnetic pulse pumping. Various types of nonlinear pulse sequences were observed depending on the pump pulse repetition period and the position of the pulse carrier frequency with respect to the ring resonator frequency spectrum. A theoretical model is suggested and calculations are performed that give a detailed explanation of the observed phenomena.     

Polarization effects and manifestations of nonparaxiality in collisions of soliton-like beams (pulses)

Collisions of polarized soliton-like light beams are analyzed numerically. The polarization is shown to influence considerably the merging of the solitons, the energy exchange between them, and the increase in their number in the process of collision. In addition to the polarization effects, induced anisotropy and nonparaxiality can also manifest themselves substantially in collisions. The disturbance of the soliton structure of the beam in consequence of the finite length of a pulse is shown to give rise to distortions of its profile, which are considerably enhanced in collisions and can lead to a fragmentation of the beams in the direction of propagation.     

超短激光脉冲在等离子体中的分裂以及类孤子结构的形成

用一维粒子模拟研究了超短脉冲在等离子体中传播时产生的光孤子结构以及由此形成的脉冲分裂现象，比较了不同峰值强度和脉冲宽度对形成光孤子以及脉冲传播方式的影响.研究表明: 脉冲宽度在若干个到十几个振荡周期的超短脉冲在等离子体中可能形成高速传播的光孤子；脉冲宽度增加和强度增大两种方式都可以使得孤子结构的传播速度减慢,且由于高阶孤子的衰变使得初始激光脉冲在等离子体中发生分裂，形成两个以不同速度向前传播的孤子结构.由孤子阶数的理论计算可较好地预言激光脉冲在等离子体中分裂的子脉冲数. 关键词： 光孤子 超短激光脉冲 等离子体 粒子模拟     

On the effect of transverse perturbations on the propagation of soliton-like two-component pulses in a uniaxial crystal

The combined approach including the method of analytic continuation of dispersion parameters to the complex plane and an averaged variational principle of the Ritz-Whitham type is used for studying the propagation of a soliton-like two-component pulse in a uniaxial crystal in the direction perpendicular to its optic axis. The ordinary component of the soliton is a pulse with an arbitrary number of light oscillations (down to one period), and the extraordinary component is a video pulse. Such a pulse is shown to be stable against small transverse perturbations, including small-scale ones.     

Surface plasmon-polariton waves in optically active media

A theory of surface plasmon-polariton wave propagation along an interface of an optically active medium and metal or metamaterial has been developed. It is shown that optical activity leads to changing of cross section and polarization of the surface modes, whereas the propagation constant in first approximation does not depend on the gyrotropy coefficient.     

Excitation, generation, and propagation of soliton-like spin-wave pulses in ferromagnetic films: Numerical calculation and experiment

The excitation, collision, and detection of soliton-like spin-wave pulses in ferromagnetic films are numerically simulated. The theoretical dependence of the pulse peak power at the output of the delay line on the peak power at the input of the input transducer is constructed for the first time. The experiment is compared with measurements. The shape of the nonlinear magnetization pulse excited and propagating in the film is theoretically studied as a function of the carrier frequency position relative to the backward volume spin-wave (BVSW) spectrum. The head-on collision of soliton-like BVSW pulses in ferromagnetic films is simulated for the first time.     

Possibility of generating a sequence of attosecond subpulses upon second harmonic generation of high-intensity femtosecond pulses in an optically extended medium

Optics and Spectroscopy - Based on numerical simulation, we demonstrate the possibility of forming a sequence of equalintensity coupled subpulses upon second harmonic generation (SHG) of a...