85 research outputs found
High laser harmonics induced by the Berry curvature in time-reversal invariant materials
A new nonlinear scheme of high harmonics generation in a wide class of
time-reversal invariant materials with broken spatial inversion symmetry (where
recently the nonlinear Hall effect has been established) due to the nontrivial
topology of bands is proposed. A microscopic quasiclassical theory describing
the nonperturbative optical response of pseudo-relativistic electrons with
nonzero Berry curvature of bands to a strong laser field is developed. We
analyze the harmonic content of the induced current and show that one can
decouple induced laser harmonics solely by the Berry curvature of bands. We
also study the dependence of the nonlinear response on the driving wave and
system parameters.Comment: 8 pages, 5 figure
Two-level system with broken inversion symmetry coupled to a quantum harmonic oscillator
We study the generalized Jaynes-Cummings model of quantum optics at the
inversion-symmetry-breaking and in the ultrastrong coupling regime. With the
help of a generalized multiphoton rotating-wave approximation, we study the
stationary solutions of the Schr\"{o}dinger equation. It is shown that the
problem is reduced to resonant interaction of two position-displaced harmonic
oscillators. Explicit expressions for the eigenstates and eigenvalues of
generalized Jaynes-Cummings Hamiltonian are presented. We exemplify our
physical model with analytical and numerical considerations regarding collapse
and revivals of the initial population of a two-level system and photon
distribution function at the direct multiphoton resonant coupling.Comment: 5 pages, 5 figure
Relativistic Quantum Theory of Cyclotron Resonance in a Medium
In this paper the relativistic quantum theory of cyclotron resonance in an
arbitrary medium is presented. The quantum equation of motion for charged
particle in the field of plane electromagnetic wave and uniform magnetic field
in a medium is solved in the eikonal approximation. The probabilities of
induced multiphoton transitions between Landau levels in strong laser field is
calculated.Comment: 4 pages, RevTe
Relativistic theory of the above-threshold multiphoton ionization of hydrogen-like atoms in the ultrastrong laser fields
The relativistic theory of above-threshold ionization (ATI) of hydrogen-like
atoms in ultrastrong radiation fields, taking into account the photoelectron
induced rescattering in the continuum spectrum is developed. It is shown that
the contribution of the latter in the multiphoton ionization probability even
in the Born approximation by Coulomb field is of the order of ATI probability
in the scope of Keldysh-Faisal-Reiss ansatz.Comment: REVTeX, 13 page
Quantum Theory of Generation of Coherent X-Ray in a Wiggler
In this paper we present the nonlinear quantum theory of X-Ray FEL in a
wiggler. We present the solution of the Dirac equation in a space periodic
strong magnetic field, which describes the quantum dynamics of a single
electron in a wiggler. With the help of obtained wave function of an electron
the self-consistent set of the Maxwell and relativistic quantum kinetic
equations is obtained. Then, the process of coherent X-ray radiation generation
in nonlinear quantum regime, when the photon energy is larger than resonance
widths due to energetic/angular spreads of an electron beam and resonance width
caused by finite interaction length, is investigated.Comment: 11 pages, RevTe
On the theory of the relativistic cross sections for stimulated bremsstrahlung on an arbitrary electrostatic potential in the strong electromagnetic field
On the base of relativistic generalized eikonal approximation wave function
the multiphoton cross sections of a Dirac particle bremsstrahlung on an
arbitrary electrostatic potential and strong laser radiation field are
presented. In the limit of the Born approximation the ultimate analytical
formulas for arbitrary polarization of electromagnetic wave have been obtained.Comment: Revtex,10 pages,3 figure
Relativistic quantum theory of high harmonic generation on atoms/ions by strong laser fields
High-order harmonic generation (HHG) by hydrogenlike atoms/ions in the
uniform periodic electric field, formed by the two linearly polarized
counterpropagating laser beams of relativistic intensities, is studied. The
relativistic quantum theory of HHG in such fields, at which the impeding factor
of relativistic magnetic drift of a strong wave can be eliminated, is presented
arising from the Dirac equation. Specifically, a scheme of HHG in underdense
plasma with the copropagating ultraintense laser and fast ion beams is
proposed.Comment: 8 pages, 8 figures, Conference: Photons, Atoms, and Qubits 2007
(PAQ07, paper 47
Harmonics generation and intense terahertz radiation from polar molecules at multiphoton resonant excitation in laser fields
The coherent radiation spectrum of two-level polar molecules with UV
transition is studied at the multiphoton resonant excitation by a moderately
strong laser field. The spectrum corresponding to harmonic generation and
low-frequency radiation is investigated both analytically and numerically.
Specifically, a mechanism for generation of intense smoothly tunable terahertz
radiation by two-level molecular configurations (with dynamic Stark shifts)
possessing permanent dipole moments, is considered.Comment: 8 pages, 6 figure
Multiphoton Resonant Transitions of Electrons in the Laser Field in a Medium
Within the scope of the relativistic quantum theory for electron-laser
interaction in a medium and using the resonant approximation for the two
degenerated states of an electron in a monochromatic radiation field [1] a
nonperturbative solution of the Dirac equation (nonlinear over field solution
of the Hill type equation) are obtained. The multiphoton cross sections of
electrons coherent scattering on the plane monochromatic wave at the Cherenkov
resonance are obtained taking into account the specificity of induced Cherenkov
process [1, 2] and spin-laser interaction as well. In the result of this
resonant scattering the electron beam quantum modulation at high frequencies
occurs that corresponds to a quantity of an electron energy exchange at the
coherent reflection from the ''phase lattice'' of slowed plane wave in a
medium. So, we can expect to have a coherent X-ray source in induced Cherenkov
process, since such beam is a potential source of coherent radiation itself.Comment: 6 pages, REVTE
Enhanced harmonic generation and wave-mixing via two-color multiphoton excitation of atoms/molecules
We consider harmonics generation and wave-mixing by two-color multi photon
resonant excitation of three-level atoms/molecules in strong laser fields. The
coherent part of the spectra corresponding to multicolor harmonics generation
is investigated. The obtained analytical results on the basis of generalized
rotating wave approximation are in a good agreement with numerical
calculations. The results applied to the hydrogen atom and homonuclear diatomic
molecular ion show that one can achieve efficient generation of moderately high
multicolor harmonics via multiphoton resonant excitation by appropriate laser
pulses.Comment: 7 pages, 6 figure
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