Enhanced radiation of nonlinear Thomson backscattering by a tightly focused Gaussian laser pulse and an external magnetic field

Abstract

The electron dynamics and the Thomson backscattering of an electron moving in a combined field of a tightly focused Gaussian laser pulse and an external uniform magnetic field are investigated in detail. It is found that by considering the tightly focused Gaussian laser pulse, the electron can be pushed out from the laser pulse by the ponderomotive force, resulting in the symmetry breaking of the electron dynamics from the Gaussian envelope, which can dramatically enhance the radiation intensity. It is also found that by introducing an external magnetic field, the emergence of the cyclotron motion of the electron under the external magnetic field also breaks the symmetry of the electron dynamics and enhances the radiation. Especially in the resonance case, i.e., the cyclotron frequency of the electron is close to the laser frequency, the emission spectrum is further enhanced due to the great extension of the interaction time and the symmetry breaking by the beat wave between the helix motion and the cyclotron motion of the electron in the combined field, and a platform with high radiation intensity containing the THz band has also appeared.

Reply to the Comment by Yubo Wang et al.

“…In the Comment [1], the claim was made that the higher-order correction terms of a tightly focused Gaussian laser pulse, including the longitudinal vector potential, the non-planar effect of the laser wavefront and the Rayleigh diffraction of the beam waist, should not be neglected in our study since the electron dynamics and its Thomson backscattering were modified by the higher-order correction terms. In this Reply, we suppose that although the higher-order correction terms have a certain influence on the dynamics and radiation spectrum of the electron, they do not affect the issues and concerns studied in our paper [2]. Therefore, it is feasible for us to adopt the lowestorder approximation for the tightly focused Gaussian laser pulse and it does not affect the main ideas and conclusions of our paper [2].…”

“…In this Reply, we suppose that although the higher-order correction terms have a certain influence on the dynamics and radiation spectrum of the electron, they do not affect the issues and concerns studied in our paper [2]. Therefore, it is feasible for us to adopt the lowestorder approximation for the tightly focused Gaussian laser pulse and it does not affect the main ideas and conclusions of our paper [2].…”

“…We welcome Wang et al for their Comment [1] on our paper [2]. In the Comment [1], the claim was made that the higher-order correction terms of a tightly focused Gaussian laser pulse, including the longitudinal vector potential, the non-planar effect of the laser wavefront and the Rayleigh diffraction of the beam waist, should not be neglected in our study since the electron dynamics and its Thomson backscattering were modified by the higher-order correction terms.…”

“…To begin with, it is important to emphasize that the main issues and concerns of our paper [2] are the radiation enhancement by considering the tightly focused effect of the Gaussian laser pulse and the generation of a THz band platform with high radiation intensity by introducing an external magnetic field.…”

“…Here and in the following, the symbols denote the same meaning with the paper [2] unless otherwise stated. Considering the Coulomb gauge of ∇•A = 0, the vector potential of the combined field with the higher-order correction (a) E-mail: hongxr@nwnu.edu.cn (corresponding author)…”