arXiv subjects

Zhengming Sheng

Publications and source records attributed to Zhengming Sheng.

At least 19 recordsLinked to original sources

arXiv2026

$X$-dispersionless solver for electromagnetic and axion fields in a cylindrical particle-in-cell code

We develop a quasi-cylindrical direction-splitting (QDS) dispersionless Maxwell solver for the open-source EPOCH particle-in-cell framework. The method preserves the exact axial phase velocity for every retained azimuthal mode by advecting transverse transport variables with the $c\Delta t=\Delta x$ shift. Building on the same transport viewpoint, we formulate an axion solver that advances the Klein--Gordon equation and the axion-regenerated electromagnetic fields within the QDS solver, so that axion--photon coupling is handled self-consistently. Benchmarks demonstrate that the cylindrical QDS solver reproduces the standard Yee wakefield structure while removing the axial group-velocity error and reducing computational cost by orders of magnitude. In the resonant axion generation test via two-color laser mixing, the QDS solver eliminates the spurious vacuum source term and maintains phase matching, whereas the Yee solver suffers from rapid dephasing due to numerical dispersion. The proposed algorithm therefore enables quasi-3D simulations of axion--photon physics in laser-plasma interaction with dispersion-free laser transport.

physics.plasm-ph↗

arXiv2026

Generating intense attosecond pulses and vectorizing polarization states from laser-plasma interactions

Vector beams with spatially structured polarization and intertwined spin-orbital angular momentum (SAM-OAM) provide powerful degrees of freedom for tailoring light-matter interactions. While such structured beams are well established in the visible and infrared regimes, extending them to the extreme-ultraviolet (EUV) and soft X-ray (SXR) domains at relativistic intensities remains a major challenge. Here, we investigate the generation of higher-order harmonic vector beams driven by relativistic laser-plasma interactions. Combining theoretical analysis with three-dimensional particle-in-cell simulations, we elucidate the underlying physical mechanisms governing the transfer and conversion of polarization and orbital angular momentum during harmonic generation. We demonstrate that both the polarization topology and OAM of the emitted harmonics can be deterministically controlled by the topological charges of the driving field. Owing to the intrinsic properties of vector beams, either few-cycle driving pulses or vector polarization gating applied to multi-cycle pulses enable the production of intense isolated attosecond pulses featuring spiral wavefronts and spatially tailored polarization states. These results establish a pathway toward high-intensity structured light sources in the EUV and SXR regimes and open new opportunities for ultrafast and strong-field light-matter interaction studies with engineered angular momentum.

physics.plasm-ph↗

arXiv2025

Gigagauss magnetic fields generated via theta-pinching driven by multiple petawatt-class lasers

Extremely high axial magnetic fields above the gigagauss (GG) level are supposed to exist in neutron stars, which may be a one of the critical parameters for their internal structures and be responsible for the X and gamma-ray emission from these stars. Here we show that such ultrahigh magnetic fields can be produced by multiple petawatt-class lasers interacting with a cuboid solid target with a cylindrical microtube in the middle. It is found that the obliquely incident intense lasers at the target surfaces enable the produced hot electrons to form an azimuthal current and subsequently induce a seed magnetic field along the cylindrical axis inside the microtube as the hot electrons transport into it. This current-field configuration is similar to a theta-pinch device. When the hot electrons and energetic ions produced via target normal sheath acceleration converge towards the microtube axis, the seed magnetic field is dramatically amplified. This process continues until the magnetic pressure near the axis becomes comparable to the thermal pressure contributed both by hot electrons and energetic ions. Later on, as the plasma in the center start to be expelled outward by the magnetic pressure, an electron current ring with extremely high densities is formed, leading to a further boost of the magnetic fields to well above the GG-level. A scaling of the magnetic field strength with laser intensities, pulse durations, incident angles, and target sizes is presented and verified by numerical simulations, which demonstrates the robustness of our scheme. Our scheme is well suited for experimental realization on 100 terawatt-class to petawatt-class femtosecond or picosecond laser facilities with multiple linearly polarized laser beams.

physics.plasm-ph↗

arXiv2025

Acceleration of Ultrahigh Energy Particles from Fast Radio Bursts

Two extreme events in the universe, fast radio bursts (FRBs) and cosmic rays (CRs), could be correlated, where FRBs with extreme field strength near their sources may contribute to CRs. This study investigates localized particle acceleration driven by FRB-like ultra-relativistic electromagnetic pulses in an electron--positron--ion plasma system. It is found ultra-high energy neutral plasma sheets form constantly via the front erosion of an FRB pulse. There are two regimes of ion acceleration depending upon the field strength and the plasma density: the piston regime driven by the Lorentz force of the pulse, and the wakefield regime dominated by charge separation field. The predicted energy scalings align well with particle-in-cell simulations. A power-law energy spectrum with an index close to the CRs naturally emerges during FRBs expansion outward. Detecting high-energy particles possibly produced by FRBs enables deeper insights into their origins and promotes the development of multi-messenger astronomy.

astro-ph.HE↗

arXiv2025

Coherently Enhanced Axion-Photon Conversion via Seeded Photons for Short-Pulse Axion Detection

We propose a seeded axion-photon conversion scheme to enhance the sensitivity of light-shining-through-a-wall (LSW) experiments for axion detection, where the axions are generated from short pulse lasers and the usual resonant cavity is not applicable. By injecting a weak, coherent seed electromagnetic (EM) field into the axion-photon conversion region, the axion-induced EM field can constructively interfere with the seed field, amplifying the number of regenerated photons to a level exceeding that of the unseeded scenario. We evaluate the expected signal enhancement, statistical limits from Poisson counting with seed fluctuations and background, and the potential improvement in coupling sensitivity. Compared to a standard LSW setup, the seeded scheme can achieve orders-of-magnitude higher photon yield per axion, potentially surpassing resonance-enhanced experiments in certain parameter regimes. This approach presents a promising pathway to extend the reach of laboratory axion searches, particularly in scenarios where the resonant cavities are impractical.

hep-ph↗

arXiv2025

Axion generation and detection in laser-plasma wakefields

The axions are compelling candidates for cold dark matter, but their extremely weak interaction with photons makes laboratory searches challenging. We show that the quasi-static electromagnetic fields of a laser-plasma wakefield, which can exceed $10^{11}$\,V/m, enable axion generation without an external production magnet and enhance the conversion rate by two orders of magnitude over a conventional magnetic production region. Self-consistent particle-in-cell simulations reveal two complementary routes to detection. In the first route, axions are reconverted into photons within the wakefield and laser fields, eliminating the need for a separate regeneration magnet but requiring to suppress the intense laser-plasma background. The regenerated photons have polarization, harmonic-frequency, and Laguerre-Gaussian transverse-mode signatures that are largely absent from the driving fields, allowing successive filters to isolate the signal. In the second route, axions traverse a wall and undergo reconversion in a downstream magnet, providing a much lower background at the cost of requiring both the magnet and a seed pulse for coherent amplification. For axion masses below $0.1$\,meV, meter-scale wakefield guiding under our stated assumptions yields a projected coupling sensitivity down to $3.9\times10^{-12}\,\mathrm{GeV}^{-1}$, surpassing the projected constraint of next-generation laboratory searches. These results establish ultra-strong plasma wakefields as a magnet-free axion source with two experimentally distinct and complementary detection strategies.

physics.plasm-ph↗

arXiv2024

Modeling of axion and electromagnetic fields coupling in a particle-in-cell code

Axions have aroused widespread research interest because they can solve the strong CP problem and serve as a possible candidate for dark matter. Currently, people have explored a lot of axion detection experiments, including passively detecting the existing axions in the universe, and actively generating axions in the laboratory. Recently, axion-coupled laser-plasma interactions have been discussed as a novel method to detect axions. Petawatt (PW) lasers are considered as a powerful tool to study not only the vacuum polarization but also the axion coupling, due to their extreme fields. However, particle-in-cell (PIC) simulation is still missed in current studies, which limits the understanding of axion-coupled laser-plasma interactions. In this paper, we proposed the method to include the axion field and the coupling with electromagnetic (EM) fields in PIC codes. The axion wave equation and modified Maxwell's equations are numerically solved, while the EM field modulation from axions is considered as a first-order perturbation. Meanwhile, different axion field boundary conditions are considered to satisfy different simulation scenarios. The processes of conversions between axions and photons, and weak laser pulse propagation with axion effects are checked as benchmarks of the code. Such an extended PIC code may help researchers develop novel axion detection schemes based on laser-plasma interactions and provide a better understanding of axion-coupled astrophysical processes.

hep-ph↗

arXiv2024

PM2D: A parallel GPU-based code for the kinetic simulation of laser plasma instabilities in large scale plasmas

Laser plasma instabilities (LPIs) have significant influences on the laser energy deposition efficiency, hot electron generation, and uniformity of irradiation in inertial confined fusion (ICF). In contrast to theoretical analysis of linear development of LPIs, numerical simulations play a more and more important role in revealing the complex physics of LPIs. Since LPIs are typically a three-wave coupling process, the precise kinetic simulation of LPIs requires to resolve the laser period (around one femtosecond) and laser wavelength (less than one micron). In this paper, a full wave fluid model of LPIs is constructed and numerically solved by the particle-mesh method, where the plasma is described by macro particles that can move across the mesh grids freely. Based upon this model, a two-dimensional (2D) GPU code named PM2D is developed. It can simulate the kinetic effects of LPIs self-consistently as normal particle-in-cell (PIC) codes. Moreover, as the physical model adopted in the PM2D code is specifically constructed for LPIs, the required macro particles per grid in the simulations can be largely reduced and thus overall simulation cost is considerably reduced comparing with typical PIC codes. Moreover, the numerical noise in our PM2D code is much lower, which makes it more robust than PIC codes in the simulation of LPIs for the long-time scale above 10 picoseconds. After the distributed computing is realized, our PM2D code is able to run on GPU clusters with a total mesh grids up to several billions, which meets the typical requirements for the simulations of LPIs at ICF experimental scale with reasonable cost.

physics.plasm-ph↗

arXiv2022

Stimulated Raman scattering in the degenerate regime

Stimulated Raman scattering (SRS) in plasma in the degenerate regime is studied theoretically and numerically. Different from normal SRS with the non-degenerate eigen electrostatic mode excited, the degenerate SRS is developed at plasma density $n_e>0.25n_c$ when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency $ω_0/2$, which is no longer the non-degenerate eigenmode of electron plasma wave $ω_{pe}$. Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super hot electrons are produced by the degenerate electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this degenerate regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than $10^{15}$W/cm$^2$.

physics.plasm-ph↗

arXiv2022

Effective suppression of parametric instabilities with decoupled broadband lasers in plasma

A theoretical analysis for the stimulated Raman scattering (SRS) instability driven by two laser beams with certain frequency difference is presented. It is found that strong coupling and enhanced SRS take place only when the unstable regions corresponding respectively to the two beams are overlapped in the wavenumber space. Hence a threshold of the beam frequency difference for their decoupling is found as a function of their intensity and plasma density. Based upon this, a strategy to suppress the SRS instability with decoupled broadband lasers (DBLs) is proposed. A DBL can be composed of tens or even hundreds of beamlets, where the beamlets are distributed uniformly in a broad spectrum range such as over 10\% of the central frequency. Decoupling among the beamlets is found due to the limited beamlet energy and suitable frequency difference between neighboring beamlets. Particle-in-cell simulations demonstrate that SRS can be almost completely suppressed with DBLs at the laser intensity $\sim10^{15}$ W/cm$^2$. Moreover, stimulated Brillouin scattering (SBS) will be suppressed simultaneously with DBLs as long as SRS is suppressed. DBLs can be attractive for driving inertial confined fusion.

physics.plasm-ph↗

arXiv2022

Polychromatic drivers for inertial fusion energy

Although tremendous achievements have been made toward inertial confinement fusion, laser plasma instabilities (LPIs) remain to be an inevitable problem for current drive schemes. To mitigate these instabilities, significant efforts have been paid to produce high-power broadband ultraviolet lasers. However, no practical scheme has been demonstrated up to now for efficient triple-frequency conversion of broadband laser. Here we propose the design of polychromatic drivers for the generation of multicolor beams mainly based upon the optical parametric amplification, which can significantly enhance the third-harmonic conversion efficiency. Each polychromatic light has four colors of monochromatic beamlets with a full spectrum width of 3\%, and the beamlet colors of any two adjacent flanges are different. The suppression effects of such polychromatic lights have been investigated via large scale particle-in-cell simulations, which indicate that more than 35\% of the incident energy can be saved from the LPIs compared with monochromatic lasers for the direct-drive scheme, or high-density filled target for the indirect-drive scheme. The proposed polychromatic drivers are based on the matured technologies, and thus may pave the way towards realization of robust and high-efficiency fusion ignition.

physics.optics↗

arXiv2021

Laser structured micro-targets generate MeV electron temperature at $4 \times 10^{16}$ W/cm$^2$

Relativistic temperature electrons higher than 0.5 MeV are generated typically with laser intensities of about 10$^{18}$ W/cm$^{2}$. Their generation with high repetition rate lasers that operate at non-relativistic intensities ($\simeq$10$^{16}$ W/cm$^{2}$) is cardinal for the realization of compact, ultra-short, bench-top electron sources. New strategies, capable of exploiting different aspects of laser-plasma interaction, are necessary for reducing the required intensity. We report here, a novel technique of dynamic target structuring of microdroplets, capable of generating 200 keV and 1 MeV electron temperatures at 1/100th of the intensity required by ponderomotive scaling($10^{18}$ W/cm$^2$) to generate relativistic electron temperature. Combining the concepts of pre-plasma tailoring, optimized scale length and micro-optics, this method achieves two-plasmon decay boosted electron acceleration with "non-ideal" ultrashort (25 fs) pulses at $4\times10^{16}$ W/cm$^2$, only. With shot repeatability at kHz, this precise in-situ targetry produces directed, imaging quality beam-like electron emission up to 6 MeV with milli-joule class lasers, that can be transformational for time-resolved, microscopic studies in all fields of science.

physics.plasm-ph↗

arXiv2019

Simultaneous polarization transformation and amplification of multi-petawatt laser pulses in magnetized plasmas

With increasing laser peak power, the generation and manipulation of high-power laser pulses becomes a growing challenge for conventional solid-state optics due to their limited damage threshold. As a result, plasma-based optical components which can sustain extremely high fields are attracting increasing interest. Here, we propose a type of plasma waveplate based on magneto-optical birefringence under a transverse magnetic field, which can work under extremely high laser power. Importantly, this waveplate can simultaneously alter the polarization state and boost the peak laser power. It is demonstrated numerically that an initially linearly polarized laser pulse with 5 petawatt peak power can be converted into a circularly polarized pulse with a peak power higher than 10 petawatts by such a waveplate with a centimeter-scale diameter. The energy conversion efficiency of the polarization transformation is about $98\%$. The necessary waveplate thickness is shown to scale inversely with plasma electron density $n_e$ and the square of magnetic field $B_0$, and it is about 1 cm for $n_e=3\times 10^{20}$ cm$^{-3}$ and $B_0=100$ T. The proposed plasma waveplate and other plasma-based optical components can play a critical role for the effective utilization of multi-petawatt laser systems.

physics.plasm-ph↗

arXiv2019

Suppression of parametric instabilities in inhomogeneous plasma with multi-frequency light

The development of parametric instabilities in a large scale inhomogeneous plasma with an incident laser beam composed of multiple-frequency components is studied theoretically and numerically. Firstly, theoretical analyses of the coupling between two laser beamlets with certain frequency difference $δω_0$ for parametric instabilities is presented. It suggests that the two beamlets will be decoupled when $δω_0$ is larger than certain thresholds, which are derived for stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), and two plasmon decay (TPD), respectively. In this case, the parametric instabilities for the two beamlets develop independently and can be controlled at a low level provided the laser intensity for individual beamlet is low enough. Secondly, numerical simulations of parametric instabilities with two or more beamlets ($N\sim20$) have been carried out and the above theory model is validated. Simulations confirm that the development of parametric instabilities with multiple beamlets can be controlled at a low level, provided the threshold conditions for $δω_0$ is satisfied, even though the total laser intensity is as high as $\sim10^{15}$W/cm$^2$. With such a laser beam structure of multiple frequency components ($N\gtrsim20$) and total bandwidth of a few percentages ($\gtrsim4\%$), the parametric instabilities can be well-controlled.

physics.plasm-ph↗

arXiv2018

Absolute instability modes due to rescattering of stimulated Raman scattering in a large nonuniform plasma

Absolute instability modes due to rescattering of SRS in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite bandwidth. The different frequency components of the backscattered light can be coupled to develop absolute stimulated Raman scattering (SRS) and two plasmon decay (TPD) instability near their quarter-critical densities via rescattering process. The absolute SRS mode develops a Langmuir wave with a high phase velocity about $c/\sqrt{3}$ with $c$ the light speed in vacuum. Given that most electrons are at low velocities in the linear stage, the absolute SRS mode grows with much weak Landau damping. When the interaction evolves into the nonlinear regime, the Langmuir wave can heat abundant electrons up to a few hundred keV. Our theoretical model is validated by particle-in-cell simulations. The absolute instabilities may play a considerable role in the experiments of inertial confined fusion.

physics.plasm-ph↗

arXiv2018

THz pulses over 50 millijoules generated from relativistic picosecond laser-plasma interactions

Ultrahigh-power terahertz (THz) radiation sources are essential for many applications, such as nonlinear THz physics, THz-wave based compact accelerators, etc. However, until now none of THz sources reported, whether based upon large-scale accelerators or high power lasers, have produced THz pulses with energies above the millijoule (mJ) barrier. Here we report on the efficient generation of low-frequency (<3 THz) THz pulses with unprecedentedly high energies over 50 mJ. The THz radiation is produced by coherent transition radiation of a picosecond laser-accelerated ultra-bright bunch of relativistic electrons from a solid target. Such high energy THz pulses can not only trigger various nonlinear dynamics in matter, but also open up a new research field of relativistic THz optics.

physics.plasm-ph↗

arXiv2017

Ultrahigh charge electron beams from laser-irradiated solid surface

Compact acceleration of a tightly collimated relativistic electron beam with high charge from a laser-plasma interaction has many unique applications. However, currently the well-known schemes, including laser wakefield acceleration from gases and vacuum laser acceleration from solids, often produce electron beams either with low charge or with large divergence angles. In this work, we report the generation of highly collimated electron beams with a divergence angle of a few degrees, quasi-monoenergetic spectra peaked at the MeV level, and extremely high charge ($\sim$100 nC) via a powerful sub-ps laser pulse interacting with a solid target in grazing incidence. Particle-in-cell simulations illustrate a new direct laser acceleration scenario, in which the self-filamentation is triggered in a large-scale near-critical-density plasma and electron bunches are accelerated periodically and collimated by the ultra-intense electromagnetic field. The energy density of such electron beams in high-Z materials reaches to $\sim10^{12} \mathrm{J/m^{3}}$, making it a promising tool to drive warm or even hot dense matter states.

physics.plasm-ph↗

arXiv2017

Extreme case of Faraday effect: magnetic splitting of ultrashort laser pulses in plasmas

The Faraday effect, caused by a magnetic-field-induced change in the optical properties, takes place in a vast variety of systems from a single atomic layer of graphenes to huge galaxies. Currently, it plays a pivot role in many applications such as the manipulation of light and the probing of magnetic fields and material's properties. Basically, this effect causes a polarization rotation of light during its propagation along the magnetic field in a medium. Here, we report an extreme case of the Faraday effect where a linearly polarized ultrashort laser pulse splits in time into two circularly polarized pulses of opposite handedness during its propagation in a highly magnetized plasma. This offers a new degree of freedom for manipulating ultrashort and ultrahigh power laser pulses. Together with technologies of ultra-strong magnetic fields, it may pave the way for novel optical devices, such as magnetized plasma polarizers. In addition, it may offer a powerful means to measure strong magnetic fields in laser-produced plasmas.

physics.plasm-ph↗