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Ultrashort light pulses have strong research and application values, while nonlinear inverse Thomson scattering has been considered as a unique source of zepto-yoctosecond pulses. Here, the mechanism of nonlinear inverse Thomson scattering of a high-energy electron colliding with a tightly focused intense laser pulse is investigated through numerical simulation. The time-compression effect was proposed to explain the origin of ultrashort pulses and the nonlinear phenomenon of electron radiation in the time–space joint distribution. It is found that the time scale of electron radiation is orders of magnitude shorter than that of electron motion, and the increases in laser intensity and electron initial energy will result in stronger and shorter pulses. Yoctosecond pulses can be generated by a laser pulse with an intensity of 1.384 × 10 20   W / c m 2 and an electron with an initial energy of 51.1   M e V . These results provide theoretical and numerical basis for generating shorter light pulses. [ABSTRACT FROM AUTHOR]

In this paper, two parameters of the applied magnetic field—magnetic field strength and pulse length—are modified, the spatial properties of electron trajectories and radiation are studied, and conclusions are drawn. Under the premise that the radius of the laser pulse waist b 0 = 4 λ 0 , and that the peak amplitude a 0 = 5 corresponds to the peak laser intensity I L = 3.45 × 10 19   W / c m 2 of the electrons, obtaining high-energy and highly collimated X-rays can be realized by increasing the pulse length up to 6 λ 0 and increasing the magnitude of the applied magnetic field, or by continuously increasing the pulse length and applying a smaller magnetic field. [ABSTRACT FROM AUTHOR]

Based on the classical theory of nonlinear Thomson scattering and the single electron model, we performed extensive numerical simulations in MATLAB R2022b to comprehensively investigate how the initial phase of a tightly focused, circularly polarized laser pulse affects the radiation characteristics of high-energy electrons at different energy levels. Our findings indicate that the polar angle corresponding to the maximum radiation energy remains constant as the initial phase of the laser changes from 0 to 2π, while the azimuth angle correspondingly moves from 0 to 2π. Moreover, as the initial phase changes, the pulse width of the electron radiation peak displays a quasi-periodic oscillation with a period of π. Notably, an increase in the initial energy of the electrons results in a significant enhancement in both the peak radiation value and the collimation of the radiation. These results demonstrate that manipulating the initial phase of the driving laser pulse enables effective control over the spatial distribution of radiation light. [ABSTRACT FROM AUTHOR]

This article delves into the generation and modulation process of X-rays as high-energy photon sources. Using the principles of classical electrodynamics, this study enables nonrelativistic short pulse lasers to collide with high-energy electrons while the collision center is away from the focal point. This scattering method may produce X-rays with good collimation and monochromaticity, and it progressively approaches inverse Thomson scattering. We studied and analyzed the effects of different electron characteristics and laser parameter settings on the high-energy angular distribution and spectrum of X-rays, especially the setting of the collision center and initial electron velocity, as well as the setting of laser intensity and pulse width. Linear polarized laser pulses with relativistic intensity can generate discrete supercontinuum X-rays with spectral distortion. In addition, the relationships between electronic and laser properties and radiation energy were also studied. Our research can provide valuable insights for manipulating collimated or distorted, monochromatic, or tunable X-rays, as well as understanding their properties. [ABSTRACT FROM AUTHOR]

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]

The effects of magnetic fields on electron dynamics, spatially radiated power, and radiation spectra in tightly focused circularly polarized laser pulses are studied in detail. The laser wavelength λ 0 = 1   μ m . As the pulse width increases from λ 0 to 6 λ 0 , the electron dynamics, spatially radiated power, and spectral properties stabilize, and the benefit that can be enhanced by increasing the pulse width decreases continuously, i.e., saturation is reached. However, although the benefits are better at pulse widths equal to 6 λ 0 , to obtain high-energy, highly collimated X-rays, tightly focused circularly polarized laser pulses with larger pulse widths is better. [ABSTRACT FROM AUTHOR]

In this paper, a model of electron electromagnetic radiation is established using Lorentz formula for the interaction of a tightly focused elliptically polarized laser with a single electron under the condition of nonlinear Thomson scattering. Let the initial pulse width λ 0 be 3.3 fs. By changing the laser pulse width L , the energy distribution and space distribution of electron radiation emitted by electron under different conditions are obtained. The results show that when laser interacts with a single electron, the electromagnetic radiation emitted by the electron accumulates in a cone shape in space. With the increase of pulse width L , the peak energy of electron radiation is bimodal, and the peak power of electron radiation drops. At the same time, the longer it takes for the electron radiation to reach the peak, the frequency spectrum and time function show that the high-frequency component decreases, the cutoff frequency decreases, and the harmonic frequency increases. [ABSTRACT FROM AUTHOR]

Based on the Thomson scattering model of a single high-energy electron interacting with a Gaussian laser pulse, the motion of the electron and the spatial radiation characteristics of the scattered light during the process are simulated with the electron's varying initial position. The results reveal that the initially stationary electron first oscillates, and then travels in a straight line after interacting with a linearly polarized tightly focused intense laser. As the initial position of the electron moves forward on the z axis, the azimuth angle of the maximum energy radiation direction remains unchanged, while the polar angle gradually decreases and finally stabilizes. It is found that the maximum radiated energy in the whole space is obtained only when the electron is initially set at a specific position and when observed from a certain direction. In the maximum energy radiation direction, both the time and the frequency spectra are further studied qualitatively and quantitatively. [ABSTRACT FROM AUTHOR]

Hong et al. [Phys. Plasmas 29, 043102 (2022)] researched the nonlinear Thomson backscatter in a highly focused Gaussian linear laser pulse. They studied the law of backward harmonic spectrum and electron motion trajectory and put forward the view that "the electron will be pushed to the −z-axis by the responsible force of the falling edge of the laser pulse when the interaction time is long enough." In this Comment, we study the electron motion law under the precise laser pulse expression. We find and explain that the initial position of the electron is the reason why the electron is pushed to the −z-axis. Only when the initial position of the electron is in the −z half-axis, the electron will be pushed away at the end of the pulse. [ABSTRACT FROM AUTHOR]

Within the frame of electrodynamic and nonlinear Thomson scattering, we utilize MATLAB simulation to study the motion and radiation features of a static electron irradiated by circularly polarized laser pulses. The beam waist of non-tightly focused pulses (NFP) and tightly focused pulses (TFP) are respectively 30 λ 0 and 3 λ 0 . It is shown that with peak amplitude increasing, the peak radiation azimuth decreases at approximately the same speed regardless of the beam-focusing conditions, whereas the motion intensity has greatly varied rising trends. We also find that the beam-focusing condition only affects the electron's motion and radiation conditions significantly in intensive laser pulses, where irregular trajectories lead to complex radiated energy distributions in TFP. Furthermore, through investigating the shift of radiation ramifications in circularly polarized laser pulses, we gain novel insight into spatial decoupling process and the dynamic evolving trend of angular radiation. [ABSTRACT FROM AUTHOR]

According to the classical theory of backwards Thomson scattering, if an electron is encountered with an intense multi-cycle circularly polarized laser pulse, the radiated power is produced in the propagation of the laser pulse. The spatial and temporal emission characteristics of radiation have been investigated theoretically and numerically using a single electron model. The motion of an electron is highly relativistic and the radiated power produced by head-on collision transits from two peaks to single peak finally. This interesting phenomenon can be attributed to acceleration of the single electron on the z axis and has been studied in detail in this treatise. [ABSTRACT FROM AUTHOR]

Abstract: Linear Thomson scattering by a relativistic electron of a short pulse laser has been investigated by computer simulation. Under a laser field with a pulse of 33.3-fs full-width at half-maximum, and the initial energy of an electron of , the motion of the electron is relativistic and generates an ultrashort radiation of 76-as with a photon wave length of 2.5-nm in the backward scattering. The radiation under a high relativistic energy electron has better characteristic than under a low relativistic energy electron in terms of the pulse width and the angular distribution. [Copyright &y& Elsevier]

The utilization of X-rays produced by interaction between relativistic electrons and laser pulses finds profound application in domains such as photoelectron spectroscopy. Through numerical simulation, the influence of the laser pulse delay time τ 0 and the initial Lorentz factor γ 0 on the spatial and spectral properties of radiation produced by electron cross collision with a circularly polarized laser pulse is investigated. Also, the optimal parameters for generating quasi-monochromatic pulses and high-order harmonic radiation are discussed. The results reveal that when | τ 0 | is large, the electron collides with the leading or trailing edge of the laser pulse, resulting in superior quasi-monochromatic radiation pulses. However, when τ 0 =0, the electron collides with the center of the laser pulse, which is most favorable for the generation of high-order harmonics. Furthermore, γ 0 has a negligible impact on the monochromaticity of the fundamental harmonic but plays a detrimental role in forming a single quasi-monochromatic pulse at higher values. Instead, higher γ 0 promotes the broadening of high-order harmonics. These results are important for obtaining radiating X-rays with different properties according to practical requirements. [ABSTRACT FROM AUTHOR]