Abstract
We develop an analytical model for ultraintense attosecond pulse emission in the highly relativistic laser-plasma interaction. In this model, the attosecond pulse is emitted by a strongly compressed electron layer around the instant when the layer transverse current changes the sign and its longitudinal velocity approaches the maximum. The emitted attosecond pulse has a broadband exponential spectrum and a stabilized constant spectral phase. The waveform of the attosecond pulse is also given explicitly. We validate the analytical model via particle-in-cell simulations for both normal and oblique incidence. Based on this model, we highlight the potential to generate an isolated ultraintense phase-stabilized attosecond pulse.
Highlights
An ultrashort pulse with atomic unit of timescale (24as) can be used as a camera to capture ultrafast electron dynamics in atoms, molecules and condensed matters, enabling highly time-resolved studies of many fundamental physical processes [1, 2]
Contrary to gaseous high-order harmonic generation (HHG) in which incident laser intensities are limited to be much lower than relativistic intensity, i.e. Il ≪ 1018 W/cm2 corresponding to a0 = eEl/mecωl ≪ 1, due to the strong ionization of gaseous media [5], much brighter harmonic photon flux can be emitted in plasma HHG by employing highly relativistic laser pulses a0 ≫ 1, where Il, El and ωl are the laser intensity, electric field and frequency, e and me denote the electron charge and mass, c is the light speed in vacuum
The physics behind plasma HHG has been extensively investigated with different models [15,16,17,18,19]: coherent wake emission (CWE), relativistically oscillating mirror (ROM), coherent synchrotron emission (CSE) and relativistic electron spring (RES)
Summary
An ultrashort pulse with atomic unit of timescale (24as) can be used as a camera to capture ultrafast electron dynamics in atoms, molecules and condensed matters, enabling highly time-resolved studies of many fundamental physical processes [1, 2]. The physics behind plasma HHG has been extensively investigated with different models [15,16,17,18,19]: coherent wake emission (CWE), relativistically oscillating mirror (ROM), coherent synchrotron emission (CSE) and relativistic electron spring (RES). These models are associated and characterized by distinctive harmonic properties: spectrum, divergence and phase [10, 11, 17, 20, 21].
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