Nonlinear Compton scattering is calculated for the collision of an electron with a plane wave pulse. A mid infra-red (IR) peak arises in the photon spectrum due to long-range interference associated with the pulse envelope. The case of a flat-top pulse is studied as a toy model for pulse envelope effects and reduced to two final-state momentum integrations; the case of a sine-squared pulse is studied numerically. A perturbative expansion in charge-field coupling reveals that already at intermediate intensities, many orders are required to correctly capture the structure of the mid-IR peak. By regularising the classical result, it is shown that the mid-IR peak is due to plane-wave ponderomotive effects on the pulse envelope. Finally, it is shown that the mid-IR peak can be isolated using energy, angle and polarisation filters.
The effect of the pulse envelope on electron-positron pair creation in a circularly-polarised laser pulse is investigated. Interference on the length scale of the pulse envelope, and smoothness of the pulse edges are found to influence the pair spectrum. A toy model of a flat-top pulse is used to identify pulse envelope effects inaccessible to local approaches. Broadening of channel openings and a widening of the energy and transverse momentum distribution of the pair are found to receive contributions that are below the local harmonic threshold. By comparing pair yields in a flat-top, sine-sq…
Laser pulses traveling through a plasma can feature group velocities significantly differing from the speed of light in vacuum. This modifies the well-known Volkov states of an electron inside a strong laser-field from the vacuum case and consequently all quantum electrodynamical effects triggered by the electron. Here we present an in-depth study of the basic process of photon emission by an electron scattered from an intense short laser pulse inside a plasma, labeled nonlinear Compton scattering, based on modified Volkov solutions derived from first principles. Consequences of the nonlinear,…
Laser pulses facilitate multiphoton contributions to the trident pair production $e_L^- \to e_L^- + e_L^- + e_L^+$ , where the label $L$ indicates a laser field dressed electron ($e^-$) or positron ($e^+$). We isolate the impact of the pulse envelope in the trident S matrix element, formulated within the Furry picture, in leading order of a series expansion in the classical non-linearity parameter $a_0$. Generally, the Fourier transform of the envelope carries the information on the pulse length, which becomes an easily tractable function in the case of a $\cos^2$ pulse envelope. The transitio…
We demonstrate that the nontrivial dispersion of a plasma driven by a high-intensity laser pulse qualitatively affects fundamental nonperturbative QED processes triggered by the laser pulse even in the case that no electrons remain in the interaction volume, e.g., due to ponderomotive expulsion. In the electron-free case this plasma effect is mediated by the response current of the residual ions as a dispersive effect on the laser propagation. The residual ions hence act as an effective background to the propagating electromagnetic laser field. We demonstrate that this has an impact on the fun…
Non-linear Compton scattering of ultra-relativistic electrons traversing high-intensity laser pulses generates also hard photons. These photon high-energy tails are considered for parameters in reach at the forthcoming experiments LUXE and E-320. We consider the invariant differential cross sections $d σ/ du$ between the IR and UV regions and analyze the impact of the laser polarization and find q-deformed exponential shapes. (The variable $u$ is the light-cone momentum-transfer from initial electron to final photon.) Optical laser pulses of various durations are compared with the monochromati…
The photon spectrum from electrons scattering on multiple laser pulses exhibits interference effects not present for scattering on a single pulse. We investigate the conditions required for the experimental observation of these interference effects in electron-laser collisions, in particular analysing the roles of the detector resolution and the transverse divergence of the pump electron beam.
Effect of super-Gaussian pulse shape on pair production in chirped electric field with spatial inhomogeneity
Northwest Normal University（西北师范大学）；Lanzhou Jiaotong University（兰州交通大学）；Beijing Normal University（北京师范大学）；Beijing Academy of Science and Technology（北京科学院）
Scattering of ultraintense short laser pulses off relativistic electrons allows one to generate a large number of X- or $γ$-ray photons with the expense of the spectral width---temporal pulsing of the laser inevitable leads to considerable spectral broadening. In this Letter, we describe a simple method to generate optimized laser pulses that compensate the nonlinear spectrum broadening, and can be thought of as a superposition of two oppositely linearly chirped pulses delayed with respect to each other. We develop a simple analytical model that allow us to predict the optimal parameters of su…
The recoil associated with photon emission is key to the dynamics of ultrarelativistic electrons in strong electromagnetic fields, as are found in high-intensity laser-matter interactions and astrophysical environments such as neutron star magnetospheres. When the energy of the photon becomes comparable to that of the electron, it is necessary to use quantum electrodynamics (QED) to describe the dynamics accurately. However, computing the appropriate scattering matrix element from strong-field QED is not generally possible due to multiparticle effects and the complex structure of the electroma…
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, Möller scattering, Bhabha scattering, etc., we illustrate it for a trident process. Spec…
Analytical calculation of the spectrum of nonlinear Compton scattering beyond local approximations
National Research Nuclear University MEPhI（国立核研究大学莫斯科工程物理学院）；Skolkovo Institute of Science and Technology（斯科尔科沃科学技术研究所）；Institute of Applied Physics of the Russian Academy of Sciences（俄罗斯科学院应用物理研究所）；Deutsches Elektronen–Synchrotron DESY（德国电子同步加速器）；ELI Beamlines facility, The Extreme Light Infrastructure ERIC（ELI光束线设施，极端光基础设施欧洲研究协调中心）；FNSPE, Czech Technical University in Prague（捷克布拉格理工大学自然科学和物理工程学院）
Experimental efforts toward the detection of the nonperturbative strong-field regime of the Breit-Wheeler pair creation process plan to combine incoherent sources of GeV $γ$ quanta and the coherent fields of tightly focussed optical laser pulses. This endeavour calls for a theoretical understanding of how the pair yields depend on the applied laser field profile. We provide estimates for the number of produced pairs in a setup where the high-energy radiation is generated via bremsstrahlung. Attention is paid to the role of the transversal and longitudinal focussing of the laser field, along wi…
