Observation of a Long-Wavelength Hosing Modulation of a High-Intensity Laser Pulse in Underdense Plasma

Self Modulation and Scattering Instability of a Relativistic Short Laser Pulse in an Underdense Plasma

Characterization of self-consistent laser-plasma evolutions serves as a fundamental issue in the field of relativistic laser-plasma interactions. In this paper, we present an analysis framework for description of these evolutions during propagation of a short intense laser pulse in a sub-critical high-density plasma (the pulse length exceeds the plasma wavelength). In this context, the pulse evolutions are attributed to the wakefield induced self-modulation and destabilization via parametric exponentiation of the initial noise content. The self-consistent plasma evolutions are formulated in te…

Self-Channeling of Relativistic Laser Pulses in Large-Scale Underdense Plasmas

Relativistic self-focusing and channeling of intense laser pulses have been studied in underdense plasma using 2D PIC simulations, for different laser powers and plasma densities. Analytical solutions for the stationary evacuated channels have been recovered in PIC simulations. It is shown that otherwise stable channels can accelerate electrons due to surface waves on the walls of the channels. Relativistic filaments with finite electron density are unstable to transverse modulations which lead in the nonlinear stage to the break-up of laser pulses into independent filaments. Different regimes…

激光脉冲在欠稠密等离子体平板中传播期间功率损耗的抑制

Suppression of power losses during laser pulse propagation in underdense plasma slab

本研究通过二维PIC模拟揭示中低密度、非相对论条件下前向拉曼散射主导激光损耗，并提出以频率失谐大于等离子体频率的多色激光抑制该散射、实现高效功率传输。

通过束流不稳定性产生超准直偏振阿秒γ射线

Generation of Ultra-Collimated Polarized Attosecond $γ-$Rays via Beam Instabilities

该研究提出利用非偏振相对论电子束在固体密度等离子体中的自调制与软管不稳定性，结合非线性 Compton 散射，产生超准直、高亮度的线偏振阿秒γ射线，并获得可用于自由电子激光的高质量电子微聚束。

Indirect Self-Modulation Instability Measurement Concept for the AWAKE Proton Beam

AWAKE, the Advanced Proton-Driven Plasma Wakefield Acceleration Experiment, is a proof-of-principle R&D experiment at CERN using a 400 GeV/c proton beam from the CERN SPS (longitudinal beam size sigma_z = 12 cm) which will be sent into a 10 m long plasma section with a nominal density of approx. 7x10^14 atoms/cm3 (plasma wavelength lambda_p = 1.2mm). In this paper we show that by measuring the time integrated transverse profile of the proton bunch at two locations downstream of the AWAKE plasma, information about the occurrence of the self-modulation instability (SMI) can be inferred. In parti…

Modulation-Slippage Tradeoff in Resonant Four-Wave Upconversion

Following up on a proposal to use four-wave mixing in an underdense plasma at mildly relativistic laser intensities to produce vastly more energetic x-ray pulses [V. M. Malkin and N. J. Fisch, Phys. Rev. E, 101, 023211 (2020)], we perform the first numerical simulations in one dimension to demonstrate amplification of a short high frequency seed through four-wave mixing. We find that parasitic processes including phase modulation and spatial pulse slippage limit the amplification efficiency. We numerically explore the previously proposed "dual seed" configuration as a countermeasure against ph…

相对论质子束在等离子体中的丝化不稳定性

Filamentation of a Relativistic Proton Bunch in Plasma

实验证明长、欠稠密相对论质子束在等离子体中发生斜向不稳定性（丝化），确定阈值条件，并发现磁能随等离子体密度增加。

Influences of sinusoidal density modulation on stimulated Raman scattering in inhomogeneous plasmas

The influence of sinusoidal density modulation on the stimulated Raman scattering (SRS) reflectivity in inhomogeneous plasmas is studied by three-wave coupling equations, fully kinetic Vlasov simulations and particle in cell (PIC) simulations. Through the numerical solution of three-wave coupling equations, we find that the sinusoidal density modulation is capable of inducing absolute SRS even though the Rosenbluth gain is smaller than π, and we give a region of modulational wavelength and amplitude that the absolute SRS can be induced, which agrees with early studies. The average reflectivity…

Bow wave from ultra-intense electromagnetic pulses in plasmas

We show a new effect of the bow wave excitation by an intense short laser pulse propagating in underdense plasma. Due to spreading of the laser pulse energy in transverse direction, the bow wave causes a large-scale transverse modulation of the electron density. This can significantly increase the electric potential of the wake wave since the wake wave is generated in the region much wider than the laser pulse waist.

Transition from wakefield generation to soliton formation

It is well known that when a short laser pulse propagates in an underdense plasma, it induces longitudinal plasma oscillations at the plasma frequency after the pulse, typically referred to as the 'wakefield'. However, for plasma densities approaching the critical density wakefield generation is suppressed, and instead the EM-pulse undergoes nonlinear self-modulation. In this article we have studied the transition from the wakefield generation to formation of quasi-solitons as the plasma density is increased. For this purpose we have applied a one dimensional (1D) relativistic cold fluid model…

Plasma optical modulators for intense lasers

Optical modulators can be made nowadays with high modulation speed, broad bandwidth, while being compact, owing to the recent advance in material science and microfabrication technology. However, these optical modulators usually work for low intensity light beams. Here, we present an ultrafast, plasma-based optical modulator, which can directly modulate high power lasers with intensity up to 10^16 W/cm^2 level to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating la…

激光电离等离子体中热魏贝尔不稳定性感应磁场与线性尾波共存

Thermal Weibel instability induced magnetic fields co-exist with linear wakes in laser-ionized plasmas

本文通过模拟与实验证明激光电离等离子体中自调制尾波与魏贝尔不稳定性感应磁场可时空共存，并初步评估了该磁场对外部注入束横向发射度增长的影响。