179 research outputs found
Supercontinuum in ionization by relativistically intense and short laser pulses: ionization without interference and its time analysis
Ionization by relativistically intense laser pulses of finite duration is
considered in the framework of strong-field quantum electrodynamics. Our main
focus is on the formation of ionization supercontinua. More specifically, when
studying the energy distributions of photoelectrons ionized by circularly
polarized pulses, we observe the appearance of broad structures lacking the
interference patterns. These supercontinua extend over hundreds of driving
photon energies, thus corresponding to high-order nonlinear processes. The
corresponding polar-angle distributions show asymmetries which are attributed
to the radiation pressure experienced by photoelectrons. Moreover, our time
analysis shows that the electrons comprising the supercontinuum can form pulses
of short duration. While we present the fully numerical results, their
interpretation is based on the saddle-point approximation for the ionization
probability amplitude.Comment: 13 pages, 10 figure
Trident pair creation by a train of laser pulses: Resonance, threshold, and carrier envelope phase effects
General formulation in the realm of strong-field quantum electrodynamics is
provided for a process that occurs in the presence of a train of laser pulses
and, in the tree level, is represented by a two-vertex Feynman diagram with
exchange of a virtual photon. A scheme of retrieving resonances in the
corresponding probability distributions is also formulated in these general
settings. While the presented formalism is applicable to a variety of processes
like electron-positron pair creation and annihilation, M\"oller scattering,
Bhabha scattering, etc., we illustrate it for a trident process. Specifically,
we consider electron-positron pair creation in the muon--laser-field
collisions. We demonstrate that the probability distributions exhibit
integrable singularities close to the threshold of pair creation. Also, a
variety of resonances is observed that originate from the poles of the Feynman
photon propagator. While those resonances are, in general, obscured by strong
quantum interferences, we show that they can be isolated by changing the
carrier envelope phase of the driving laser pulses. In that case, while
transformed into the Lorentz-Breit-Wigner shape profile, the resonance position
and width can be determined.Comment: 15 pages, 9 figure
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