Search

This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings, when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought. [ABSTRACT FROM AUTHOR]

In this paper, nonlinear Thomson scattering in an intense () tightly focused () Gaussian laser pulse is theoretically and numerically investigated to demonstrate varying spatial characteristics in the few-cycle and multi-cycle domains. We find that within ultrashort incident laser pulses, electrons have the potential to radiate a single attosecond pulse with a large signal-to-noise ratio, which turns into a train of attosecond pulses with a multi-cycle laser. Furthermore, a novel asymmetry phenomenon is discovered for the first time in the few-cycle domain whereby spatial radiation lasts for only one circle with apparent peaks and valleys, in contrast to the helical radiation pattern apparent in the multi-cycle domain, which gradually turns into a common fourfold-symmetry pattern. This means that the difference between tightly and non-tightly focused laser pulses can be bridged utilizing an appropriate incident pulse duration under specific conditions. The above difference is demonstrated again in the polar plane, where electrons change from a light-spot to a light-band radiation feature when the incident pulse duration increases. [ABSTRACT FROM AUTHOR]