11,040 research outputs found
Coherence-controlled transparency and far-from-degenerate parametric gain in a strongly-absorbing Doppler-broadened medium
An inversionless gain of anti-Stokes radiation above the oscillation
threshold in an optically-dense far-from-degenerate double-Lambda
Doppler-broadened medium accompanied by Stokes gain is predicted. The outcomes
are illustrated with numerical simulations applied to sodium dimer vapor.
Optical switching from absorption to gain via transparency controlled by a
small variation of the medium and of the driving radiation parameters which are
at a level less than one photon per molecule is shown. Related video/audio
clips see in: A.K. Popov, S.A. Myslivets, and T.F. George, Optics Express Vol.
7, No 3, 148 (2000)(http://epubs.osa.org/oearchive/source/22947.htm) or
download: http://kirensky.krasn.ru/popov/opa/opa.htmComment: 4 pages, 3 eps figures, to be published in Optics Letters, vol.25, No
18 (2000), minor style changes and reference correctio
Secularly growing loop corrections in strong electric fields
We calculate one--loop corrections to the vertexes and propagators of photons
and charged particles in the strong electric field backgrounds. We use the
Schwinger--Keldysh diagrammatic technique. We observe that photon's Keldysh
propagator receives growing with time infrared contribution. As the result,
loop corrections are not suppressed in comparison with tree--level
contribution. This effect substantially changes the standard picture of the
pair production. To sum up leading IR corrections from all loops we consider
the infrared limit of the Dyson--Schwinger equations and reduce them to a
single kinetic equation.Comment: 16 pages, no figures; Minor correction
Damping of electromagnetic waves due to electron-positron pair production
The problem of the backreaction during the process of electron-positron pair
production by a circularly polarized electromagnetic wave propagating in a
plasma is investigated. A model based on the relativistic Boltzmann-Vlasov
equation with a source term corresponding to the Schwinger formula for the pair
creation rate is used. The damping of the wave, the nonlinear up-shift of its
frequency due to the plasma density increase and the effect of the damping on
the wave polarization and on the background plasma acceleration are
investigated as a function of the wave amplitude.Comment: 11 pages, 5 figures; revtex
Four-wave mixing, quantum control and compensating losses in doped negative-index photonic metamaterials
The possibility of compensating absorption in negative-index metatamterials
(NIMs) doped by resonant nonlinear-optical centers is shown. The role of
quantum interference and extraordinary properties of four-wave parametric
amplification of counter-propagating electromagnetic waves in NIMs are
discussed.Comment: 3 pages, 3 figures, LaTeX, corrected typos in eqs. (1) and (2
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