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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]

To study the time evolution of high-energy electron radiation in circularly polarized intense laser pulses in detail, a model of the interaction between the high-energy single electron and intense laser pulses is constructed based on the Lagrangian equation and the electron energy equation. Through simulation, this article vividly displays the evolution process of radiation in the spatial, frequency and time domain. By modulating the interaction time between the laser and electron and referring to the spatial distribution image of energy, the value and direction of the maximum radiation energy per unit solid angle are calculated. In addition, in specific directions, this paper discusses the effects of interaction duration on the energy frequency distribution and the power variation pattern. The results prove that the maximum radiation energy per unit solid angle will appear when the interaction time comes to about 450 fs, which is also the boundary moment when the frequency and time spectrum no longer change obviously. Therefore, by modifying the duration of the electron–laser interaction, it is possible to produce the electron radiation with desired characteristics more precisely. [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]

Based on the scalar diffraction theory, the propagation and focusing properties of a hard-edged diffracted beam generated by a Gaussian mirror resonator were investigated. Explicit expressions for the field distribution of the truncated beam that propagates through a paraxial optical ABCD system were derived in detail. Numerical examples are given to illustrate our analytical results. OCIS codes: 050.1960, 140.3300, 050.1220, 000.4430.

The far-field intensity distribution (FFID) of a beam generated by a phase-unifying mirror resonator was investigated based on scalar diffraction theory. Attention was paid to the parameters, such as obscuration ratio and reflectivity of the phase-unifying mirror, that determine the FFID. All analyses were limited to the [TEM.sub.00], fundamental mode. OCIS codes: 000.4430, 140.3300. 140.4780, 260.1960, 350.5500.

In the framework of laser-matter interaction and nonlinear Thomson scattering, we investigate the three-dimensional (3D) motion trajectories and spatial radiation characteristics of the colliding motion electrons with tightly focused circularly polarized Gaussian pulses at different intensities. Combined with the 3D spatial images and the analysis of specific two-dimensional unfolded images, we discover that the amplitude of the motion trajectory increases steadily with increasing laser intensity, the peak radiation power increases rapidly, and the peak radiation azimuth decreases slowly. In addition, by studying the electron motion under the high-intensity () laser field, we find that the electron motion is retrograde twice when interacting with pulsed laser once. Lastly, by extracting the direction and energy of spatial radiation, we indicate that the existence of a specific laser intensity can make the peak radiation azimuth and which intienity provides the maximum conversion rate of laser energy to the peak power of radiation. [ABSTRACT FROM AUTHOR]

The nonlinear Thomson backscattering of electrons interacting with a circularly polarized laser pulse is studied by using the single-electron model. By means of theoretical analysis and computer simulation, the influence of the central collision place and the beam waist radius on the spectral characteristics of the scattered light are discussed. It is indicated that the spectrum is nonlinear broadened as a result of redshifting of the Thomson scattered frequency. Only when the central collision point is set at a proper place under the tight focusing situation, can quasi-monochromatic x-rays be generated. Taking into account the requirements for the radiation intensity of scattered light, the optimum situation to generate quasi-monochromatic x-rays is explored. In addition, we find that the spectral and angular distribution of the backscattered light do not vary with azimuth angle. [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]

In this paper, the trajectory as well as the temporal and spatial characteristics of the electromagnetic radiation of high-energy electrons collided by fields of relativistically circularly polarized laser pulses are studied theoretically and calculated numerically, based on Lorentz equation, energy equation of electrons, and the basic equations of electron radiation. Results shows that the head-on collision of a single counter-streaming electron and an intense circularly polarized laser pulse can produce an ultra-intense pulse with zeptosecond duration in the direction where the azimuth angle and the polar angle. The amplitude of the electron trajectory and the peak power of its radiation are positively related to the beam waist radius. However, as the radius of the laser beam increases, its influence on the dynamic and radiation characteristics of the electron weaken gradually and become negligible when the beam waist radius is greater than 4 times the laser wavelength. [ABSTRACT FROM AUTHOR]

Osteosarcoma is among the commonly observed malignancies worldwide. High-mobility group box 1 protein (HMGB1) is a highly conserved protein and is involved in the progression of various types of human cancer. The aim of the present study was to explore whether the level of HMGB1 was involved in the necrosis of osteosarcoma cells. Doxorubicin (DXR), as an inducer of necrosis, was administered to human osteosarcoma cell lines (MG63, Saos-2 and U2OS), and the results indicated that 0.5 µg/ml DXR significantly induced the necrosis of MG63 cells (P<0.01), while 0.5 and 1.0 µg/ml DXR suppressed the viability of MG63 and U2OS cells (P<0.05), relative to untreated controls. Additionally, treatment with DXR was observed by western blot analysis to markedly increase the expression levels of HMGB1 in MG63 cells, and to significantly increase the levels of secreted HMGB1 in the supernatants of MG63 and U2OS cells (P<0.01). In conclusion, cell necrosis increased the level of HMGB1 in osteosarcoma cells, as well as the level of secreted HMGB1 in cell supernatants. Therefore, HMGB1 may be a potential target in molecular therapy for patients with osteosarcoma. [ABSTRACT FROM AUTHOR]

Abstract: The characteristics of harmonic radiation due to electron oscillation driven by an intense femtosecond laser pulse are analyzed considering a single electron model. An interesting modulated structure of the spectrum is observed and analyzed for different polarization. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width broadening of the high harmonic radiations can be limited. [Copyright &y& Elsevier]