Determination of the wave number of an electromagnetic wave propagating in high-frequency jet discharge plasma

The measurements of the amplitude-phase characteristics of the electromagnetic field in a high-frequency jet discharge burning in air and argon have been performed. Experimentally obtained radial distributions of the radial component of the electric field gave the base to determine the value of the wave number of an electromagnetic wave which propagates in the HF jet discharge plasma. The axial distribution of the radial component of the electric field has been calculated from the model of a jet discharge channel formed as a finite-length electric line.     

Navigating localized wave packets in phase space

The ability to localize and to steer Rydberg wave packets in phase space using tailored sequences of half-cycle pulses is demonstrated. Classical phase-space portraits are used to explain the method and to illustrate the level of control that can be achieved. This is confirmed experimentally by positioning a phase-space-localized wave packet at the center of a stable island or navigating it around its periphery. This work provides a valuable starting point for further engineering of electronic wave functions.     

Generation of soliton-like wave packets and wave packets with linear phase modulation in gaining optical wave-guides with saturable nonlinearity

We have considered the dynamics of soliton-like pulses and stable frequency-modulated self-similar pulses in an active medium with saturable nonlinearity and a parabolic refractive-index profile. We show that, based on gaining gradient fibers with a parabolic distribution of the refractive index and saturable nonlinearity, it is possible to create complexes that ensure generation of laser pulses with a high (above 1 TW) peak power.     

Observation of nonspreading wave packets in an imaginary potential

We propose and experimentally demonstrate a method to prepare a nonspreading atomic wave packet. Our technique relies on a spatially modulated absorption constantly chiseling away from an initially broad de Broglie wave. The resulting contraction is balanced by dispersion due to Heisenberg's uncertainty principle. This quantum evolution results in the formation of a nonspreading wave packet of Gaussian form with a spatially quadratic phase. Experimentally, we confirm these predictions by observing the evolution of the momentum distribution. Moreover, by employing interferometric techniques, we measure the predicted quadratic phase across the wave packet. Nonspreading wave packets of this kind also exist in two space dimensions and we can control their amplitude and phase using optical elements.     

Invariants of the dynamics of molecular vibrational wave packets in phase modulation

An exact analytic solution was obtained for the correlation function of the motion of a phase-modulated Gauss wave packet in an anharmonic potential. The solution is expressed through the theta-function with the parameters depending on both the potential and phase modulation of the initial wave packet. Changes in both linear and quadratic chirps result in an invariant correlation function time shift in a weakly anharmonic potential with the conservation of all the total and fractional revivals. At a strong potential anharmonicity, translational invariance with respect to a quadratic chirp is preserved in certain instances, whereas the dynamics of packets experiences qualitative changes depending on linear phase modulation. This approach can be used to qualitatively analyze intramolecular dynamics if the potential energy surface is not known exactly, which is especially useful for quantum control of large molecules, in particular, photochromes.     

Self-focusing of wave packets and envelope shock formation in nonlinear dispersive media

The self-action of three-dimensional wave packets is analyzed analytically and numerically under the conditions of competing diffraction, cubic nonlinearity, and nonlinear dispersion (dependence of group velocity on wave amplitude). A qualitative analysis of pulse evolution is performed by the moment method to find a sufficient condition for self-focusing. Self-action effects in an electromagnetically induced transparency medium (without cubic nonlinearity) are analyzed numerically. It is shown that the self-focusing of a wave packet is accompanied by self-steepening of the longitudinal profile and envelope shock formation. The possibility of envelope shock formation is also demonstrated for self-focusing wave packets propagating in a normally dispersive medium.     

Observation of lower hybrid wave packets with very large amplitude in a high-voltage linear plasma discharge

We have observed repetitive, large-amplitude (> 80 kV/cm) parallel electric-field wave packets with electron density modulation in the current limiting phase of a high-voltage linear plasma discharge. The power spectral density of the whole span of the wave packets shows the peak frequency, 65 MHz, in the vicinity of the lower hybrid frequency.     

Amplitude and phase reconstruction of electron wave packets for probing ultrafast photoionization dynamics

Ultrafast atomic processes, such as excitation and ionization occurring on the femtosecond or shorter time scale, were explored by employing attosecond high-harmonic pulses. With the absorption of a suitable high-harmonic photon a He atom was ionized, or resonantly excited with further ionization by absorbing a number of infrared photons. The electron wave packets liberated by the two processes generated an interference containing the information on ultrafast atomic dynamics. The attosecond electron wave packet, including the phase, from the ground state was reconstructed first and, subsequently, that from the 1s3p state was retrieved by applying the holographic technique to the photoelectron spectra comprising the interference between the two ionization paths. The reconstructed electron wave packet revealed details of the ultrafast photoionization dynamics, such as the instantaneous two-photon ionization rate.     

Formation of envelope solitons of spin-wave packets propagating in thin-film magnon crystals

The formation of light envelope solitons has been experimentally observed under the pulsed excitation and propagation of radio-frequency spin-wave packets in a magnon crystal, a periodic magnetic film structure. The magnon crystal has been fabricated from a thin single-crystal yttrium iron garnet (YIG) film. The envelope solitons have been excited at frequencies corresponding to the edges of the Bragg-resonance-induced band gaps of the spin-wave spectrum of the magnon crystal. A theoretical explanation of the observed phenomenon has been proposed with the use of the numerical simulation of the formation of solitons based on the nonlinear Schrödinger equation.     

Cyclotron dynamics of electron wave packets in topological insulators in an external magnetic field

The evolution of electron wave packets formed from surface states in topological insulators located in an external magnetic field is studied. The electron and spin densities of the wave packets under consideration are calculated analytically and are visualized. The influence of the main characteristics of the wave packets (the spin polarization) on the splitting and the change in their forms with time is considered.     

Dynamics of electron wave packets in topological insulators

Dynamics of wave packets formed by surface (edge) electronic states in topological insulators has been investigated. The spin and electron probability density, as well as zitterbewegung, of wave packets have been calculated analytically and numerically for various values of the Hamiltonian parameters. The effects of the main parameters (size and spin polarization) of the wave packets on a change in the packet shape and oscillations of their average velocity have been considered.     

Recovery time in quantum dynamics of wave packets

A wave packet formed by a linear superposition of bound states with an arbitrary energy spectrum returns arbitrarily close to the initial state after a quite long time. A method in which quantum recovery times are calculated exactly is developed. In particular, an exact analytic expression is derived for the recovery time in the limiting case of a two-level system. In the general case, the reciprocal recovery time is proportional to the Gauss distribution that depends on two parameters (mean value and variance of the return probability). The dependence of the recovery time on the mean excitation level of the system is established. The recovery time is the longest for the maximal excitation level.     

Instability of wave packets in nonlinear inhomogeneous waveguides

Conditions for modulation instability of a wave packet to occur in cubically nonlinear single- and double-mode waveguides with various distributions of dispersion parameters over the waveguide length are investigated. Analytical expressions are obtained for the integral gain increment and other characteristics governing the modulation instability dynamics. Features of the dynamics are revealed using numerical simulation.     

Diffusion of electrons in coherent Langmuir wave packets

A new diffusion coefficient for electrons repeatedly interacting with coherent Langmuir wave packets is proposed. The model accounts for regular islands embedded in a region of connected stochasticity, since these islands have a profound effect on the diffusion process. The diffusion coefficient has a resonant form which has been explicity calculated incorporating the finite decay times of the correlation functions. Theoretical predictions compare well with numerical results derived from solutions of the equation of motion.     

Extreme wave formation in unidirectional sea due to stochastic wave phase dynamics

The authors consider a stochastic model based on the interaction and phase coupling amongst wave components that are modified envelope soliton solutions to the nonlinear Schrödinger equation. A probabilistic study is carried out and the resulting findings are compared with ocean wave field observations and laboratory experimental results. The wave height probability distribution obtained from the model is found to match well with prior data in the large wave height region. From the eigenvalue spectrum obtained through the Inverse Scattering Transform, it is revealed that the deep-water wave groups move at a speed different from the linear group speed, which justifies the inclusion of phase correction to the envelope solitary wave components. It is determined that phase synchronization amongst elementary solitary wave components can be critical for the formation of extreme waves in unidirectional sea states.     

Nonspreading wave packets in three dimensions formed by an ultracold bose gas in an optical lattice

We predict that an ultracold Bose gas in an optical lattice can give rise to a new form of condensation, namely, nonspreading 3D wave packets that reflect the symmetry of the Laplacian with a negative effective mass along the lattice direction and are allowed to exist in the absence of any trapping potential even in the limit of noninteracting atoms. This result also has strong implications for optical propagation in periodic structures.