arXiv subjects

Ruxin Li

Publications and source records attributed to Ruxin Li.

At least 37 records · Page 2Linked to original sources

arXiv2025

Coherent Axion Production through Laser Crystal Interaction

We investigate the interaction between an optical laser and an ionic crystal and reveal coherent emission of axions through phase-match between laser and axion fields. Such emission is further enhanced by stacking thin crystal layers of half-wavelength thickness. Based on these findings, we propose a novel method for generating and detecting axions in terrestrial experiments, achieving up to a two-order-of-magnitude increase in transition probability compared to light-shining-through-wall (LSW) experiments with the same interaction region size. For an experimental length of 10 meters, this setup could lower the exclusion limit to $g_{aγγ}\gtrsim1.32\times10^{-11}\textrm{GeV}^{-1}$ with currently available laser technologies.

hep-ph↗

arXiv2025

Efficiently Laser Driven Terahertz Surface Plasmon Polaritons on Long Metal Wire

We experimentally demonstrate a novel scheme for efficiently generating intense terahertz (THz) surface plasmon polaritons (SPPs) on a sub-wavelength-diameter meter-long metal wire. Driven by a subrelativistic femtosecond laser (a0=0.3, 3 mJ) focused at the wire's midpoint, single-cycle ten-megawatt THz SPPs are excited and propagating bidirectionally along it over 25 cm. The measured laser-to-SPPs energy conversion efficiency is reaching up to ~2.4%, which is the highest value at present. It is proved that the THz SPPs are excited by coherent transition radiation of the subrelativistic laser produced escaping electrons. Particle-in-cell together with CST simulations confirm the experimental observations. Our scheme of using readily available subrelativistic laser should thus be useful to applications requiring terawatt level single-cycle THz SPPs.

physics.optics↗

arXiv2025

Quasi-perfect spatiotemporal optical vortex with suppressed mode degradation

Spatiotemporal optical vortex (STOV) carrying transverse orbital angular momentum (OAM) enriches the family of vortex beams and exhibit unique properties. Typically, a high-order STOV with an intensity null degrades into multiple first-order STOVs embedded within a single wave packet during propagation, a phenomenon known as time diffraction or mode degradation. However, this degradation limits the applicability of STOVs in specialized fields. Therefore, the generation of mode degradation-suppressed STOVs (MDS-STOVs) is of significant for both practical applications and theoretical studies. Herein, we theoretically analyze the generation of MDS-STOVs by utilizing a conical phase to localize the energy of the STOV into a ring-shaped structure. For MDS-STOVs with large topological charges (TCs), the ring-shaped profile can be well-maintained, and the rapid expansion of the beam size with increasing TC is significantly suppressed compared to conventional STOVs. As a result, these MDS-STOVs can be regarded as quasi-perfect STOVs (QPSTOVs). Furthermore, QPSTOVs exhibit strong resistance to group delay dispersion (GDD), eliminating the need for precise dispersion control and facilitating their generation and application. This work advances our understanding of the physical properties of light carrying transverse OAM and opens up exciting avenues for the application of STOVs in diverse fields, such as optical communication and quantum information processing.

physics.optics↗

arXiv2025

Enhanced Proton Acceleration via Petawatt Laguerre-Gaussian Lasers

High-energy, high-flux collimated proton beams with high repetition rates are critical for applications such as proton therapy, proton radiography, high-energy-density matter generation, and compact particle accelerators. However, achieving proton beam collimation has typically relied on complex and expensive target fabrication or precise control of auxiliary laser pulses, which poses significant limitations for high-repetition applications. Here, we demonstrate an all-optical method for collimated proton acceleration using a single femtosecond Laguerre-Gaussian (LG) laser with an intensity exceeding 1020 W/cm2 irradiating a simple planar target. Compared to conventional Gaussian laser-driven schemes, the maximum proton energy is enhanced by 60% (reaching 35 MeV) and beam divergence is much reduced. Particle-in-cell simulations reveal that a plasma jet is initially focused by the hollow electric sheath field of the LG laser, and then electrons in the jet are further collimated by self-generated magnetic fields. This process amplifies the charge-separation electric field between electrons and ions, leading to increased proton energy in the longitudinal direction and improved collimation in the transverse direction. This single-LG-laser-driven collimation mechanism offers a promising pathway for high-repetition, high-quality proton beam generation, with broad potential applications including proton therapy and fast ignition in inertial confinement fusion.

physics.plasm-ph↗

arXiv2024

Tunable ultraviolet dispersive-wave emission driven directly by 40-fs Ti: sapphire laser pulses in hollow capillary fiber

We demonstrate that by using 1-m-long gas-filled hollow capillary fiber (HCF) with a core diameter of 100 μm, tunable ultraviolet (UV) dispersive-wave (DW) pulses can be generated in a compact, single-stage set-up driven directly by 40-fs Ti: sapphire laser pulses. By adjusting the gas type and pressure inside the HCF, the central wavelength of the UV DW can be continuously tuned from 185 nm to ~450 nm. In the experiment, we found that for longer-wavelength (from ~320 to ~450 nm) DW generation, Raman-active gas filled in the HCF can efficiently suppress the pulse splitting effect of the high-order soliton due to the Raman-induced pulse energy dissipation, leading to the high-quality DW generation at these wavelengths with smooth, single-peak spectra. These results provide some useful insights for designing compact, wavelength-tunable ultrafast UV light sources with microjoule-level pulse energies.

physics.optics↗

arXiv2024

Isolated Attosecond $γ$-Ray Pulse Generation with Transverse Orbital Angular Momentum Using Intense Spatiotemporal Optical Vortex Lasers

An isolated attosecond vortex $γ$-ray pulse is generated by using a relativistic spatiotemporal optical vortex (STOV) laser in particle-in-cell simulations. A $\sim$ 300-attosecond electron slice with transverse orbital angular momentum (TOAM) is initially selected and accelerated by the central spatiotemporal singularity of the STOV laser. This slice then collides with the laser's reflected Gaussian-like front from a planar target, initiating nonlinear Compton scattering and resulting in an isolated, attosecond ($\sim$ 300 as), highly collimated ($\sim$ 4$\degree$), ultra-brilliant ($\sim 5\times 10^{24}$ photons/s/mm$^2$/mrad$^2$/0.1\%BW at 1 MeV) $γ$-ray pulse. This STOV-driven approach overcomes the significant beam divergence and complex two-laser requirements of prior Gaussian-based methods while introducting TOAM to the attosecond $γ$-ray pulse, which opens avenues for ultrafast imaging, nuclear excitation, and detection applications.

physics.plasm-ph↗

arXiv2024

First Proof of Principle Experiment for Muon Production with Ultrashort High Intensity Laser

Muons, which play a crucial role in both fundamental and applied physics, have traditionally been generated through proton accelerators or from cosmic rays. With the advent of ultra-short high-intensity lasers capable of accelerating electrons to GeV levels, it has become possible to generate muons in laser laboratories. In this work, we show the first proof of principle experiment for novel muon production with an ultra-short, high-intensity laser device through GeV electron beam bombardment on a lead converter target. The muon physical signal is confirmed by measuring its lifetime which is the first clear demonstration of laser-produced muons. Geant4 simulations were employed to investigate the photo-production, electro-production, and Bethe-Heitler processes response for muon generation and their subsequent detection. The results show that the dominant contributions of muons are attributed to the photo-production/electro-production and a significant yield of muons up to 0.01 $μ$/$e^-$ out of the converter target could be achieved. This laser muon source features compact, ultra-short pulse and high flux. Moreover, its implementation in a small laser laboratory is relatively straightforward, significantly reducing the barriers to entry for research in areas such as muonic X-ray elemental analysis, muon spin spectroscopy and so on.

physics.acc-ph↗

arXiv2024

Generation of Quantum Vortex Electrons with Intense Laser Pulses

Accelerating a free electron to high energy forms the basis for studying particle and nuclear physics. Here it is shown that wavefunction of such an energetic electron can be further manipulated with femtosecond intense lasers. During the scattering between a high-energy electron and a strong laser pulse, we find a regime where the enormous photon spin angular momenta can be efficiently transferred to the electron orbital angular momentum (OAM). The wavefunction of the scattered electron is twisted from its initial plane-wave state to quantum vortex state. Nonlinear quantum electrodynamics (QED) theory suggests that GeV-level electrons acquire average intrinsic OAM beyond 100 h-barat laser intensities of 10^20W/cm^2 with linear scaling. These electrons emit gamma photons with double-peaked spectrum, which sets them apart from ordinary electrons. The findings demonstrate a proficient method for generating relativistic leptons with quantum vortex wavefunctions based on existing laser technology, thereby fostering a novel source for particle and nuclear physics.

physics.optics↗

arXiv2024

Probing Berry phase effect in topological surface states

We have observed the Berry phase effect associated with interband coherence in topological surface states (TSSs) using two-color high-harmonic spectroscopy. This Berry phase accumulates along the evolution path of strong field-driven election-hole quasiparticles in electronic bands with strong spin-orbit coupling. By introducing a secondary weak field, we perturb the evolution of Dirac fermions in TSSs and thus provide access to the Berry phase. We observe a significant shift in the oscillation phase of the even-order harmonics from the spectral interferogram. We reveal that such a modulation feature is linked to the geometric phase acquired in the nonperturbative dynamics of TSSs. Furthermore, we show that the overwhelming Berry phase effect can significantly deform the quantum paths of electron-hole pairs, thus enhancing the ability to harness electron spin using lightwaves in quantum materials with strong spin-orbit interactions.

physics.optics↗

arXiv2024

Octave-wide broadening of ultraviolet dispersive wave driven by soliton-splitting dynamics

Coherent dispersive wave emission, as an important phenomenon of soliton dynamics, manifests itself in multiple platforms of nonlinear optics from fibre waveguides to integrated photonics. Limited by its resonance nature, efficient generation of coherent dispersive wave with ultra-broad bandwidth has, however, proved difficult to realize. Here, we unveil a new regime of soliton dynamics in which the dispersive wave emission process strongly couples with the splitting dynamics of the driving pulse. High-order dispersion and self-steepening effects, accumulated over soliton self-compression, break the system symmetry, giving rise to high-efficiency generation of coherent dispersive wave in the ultraviolet region. Simultaneously, asymmetric soliton splitting results in the appearance of a temporally-delayed ultrashort pulse with high intensity, overlapping and copropagating with the dispersive wave pulse. Intense cross-phase modulations lead to octave-wide broadening of the dispersive wave spectrum, covering 200 to 400 nm wavelengths. The highly-coherent, octave-wide ultraviolet spectrum, generated from the simple capillary fibre set-up, is in great demand for time-resolved spectroscopy, ultrafast electron microscopy and frequency metrology applications, and the critical role of the secondary pulse in this process reveals some new opportunities for all-optical control of versatile soliton dynamics.

physics.optics↗

arXiv2023

Self-compression of ultrahigh-peak-power lasers

Pulse self-compression is a simple and economical method for improving the peak power of ultra-intense laser pulses. By solving a modified nonlinear Schrodinger equation considering the fifth-order susceptibility, we found that self-compression appeared even in normally dispersive medium owing to the negative fifth-order susceptibility inducing a mass of negative frequency chirp. Furthermore, negatively pre-chirped pulses allow for self-compression at lower intensity, avoiding medium damage. We numerically analyze the optimal choice of pre-chirp, input intensity, and medium length. A proof-of-principle experiment successfully proves the above theoretical findings. It is expected that petawatt or even exawatt laser pulses with 25 fs/15 fs transform limited pulse duration can be self-compressed to about 9.9 fs/7.6 fs in normally dispersive medium, such as fused silica glass plate.

physics.optics↗

arXiv2023

Broadband Dispersive-Wave Emission Coupled with Two-Stage Soliton Self-Compression in Gas-Filled Anti-Resonant Hollow-Core Fibers

We studied the underlying mechanism of broadband dispersive-wave emission within a resonance band of gas-filled anti-resonant hollow-core fiber. Both theoretical and experimental results unveiled that the high-order soliton, launched into the hollow-core fiber, experienced two stages of pulse compression, resulting in a multi-peak structure of the dispersive-wave spectrum. Over the first-stage pulse compression, a sharp increase of the pulse peak power triggered the first time of dispersion-wave emission, and simultaneously caused ionization of the noble gas filled in the fiber core. Strong soliton-plasma interactions led to blue shifting of the pump pulse, and the blue-shifted pulse experienced a decreasing dispersion value in the fiber waveguide, resulting in an increase of its soliton order. Then, the second-stage pulse compression due to the high-order soliton effect triggered the second time of dispersive-wave emission at a phase-matched frequency slightly lower than that in the first stage. Multi-peak spectra of the output dispersive-waves and their formation dynamics were clearly observed in our experiments, which can be understood using a delicate coupling mechanism among three nonlinear effects including high-order-soliton compression, soliton-plasma interaction and phase-matched dispersive-wave emission. The output broadband dispersive-wave could be potentially compressed to sub-30 fs duration using precise chirp-compensation technique.

physics.optics↗

arXiv2023

A novel small-scale self-focusing suppression method for ultrahigh peak power lasers

We proposed a novel method, using an asymmetric four grating compressor (AFGC) to improve the spatial uniformity of laser beams, to suppress the small-scale self-focusing (SSSF) during the post-compression of ultrahigh peak power lasers. The spatial uniformity is an important factor in performing post-compression, due to the spatial intensity nonuniformity will be enhanced while going through a nonlinear process. And what's more, the strong intensity spikes induced during nonlinear process can seriously damage the subsequent optical components. Moreover, the three-dimensional numerical simulations of the post-compression are implemented based on a petawatt (PW) class laser with a standard compressor and an AFGC. The results show that the post-compression with AFGC can shorten the laser pulses from 30fs to sub-10fs and meanwhile efficiently suppress SSSF. This work provides a promising scheme for the post-compression scaling to PW and even 10PW lasers.

physics.optics↗

arXiv2022

Measurements of microjoule-level, few-femtosecond ultraviolet dispersive-wave pulses generated in gas-filled hollow capillary fibers

High-energy ultraviolet pulse generation in gas-filled hollow capillary fibers (HCFs) through dispersive-wave-emission process, has attracted considerable attentions in recent several years due to its great application potentials in ultraviolet spectroscopy and photochemistry. While the ability of this technique to deliver high-energy, ultrafast ultraviolet pulses is widely recognized, few-fs duration of μJ-level dispersive-wave (DW) pulses has, however, escaped direct measurements. In this letter, we demonstrate that using several chirped mirrors, few-fs ultraviolet DW pulses can be obtained in atmosphere environment without the use of vacuum chambers. The pulse temporal profiles, measured using a self-diffraction frequency-resolved optical gating set-up, exhibit full-width-half-maximum pulse widths of 9.6 fs at 384 nm and 9.4 fs at 430 nm, close to the Fourier-transform limits. Moreover, theoretical and experimental studies reveal the strong influences of driving pulse energy and HCF length on temporal width and shape of the measured DW pulses. The ultraviolet pulses obtained in atmosphere environment with μJ-level pulse energy, few-fs pulse width and broadband wavelength tunability are ready to be used in many applications.

physics.optics↗

arXiv2022

High-order harmonic generation in X-ray range from laser induced noble gas multivalent ions

Sub-femtosecond x-ray burst is powerful tool for probing and imaging electronic and concomitant atomic motion in attosecond physics. For years, x-ray source (above 2 keV) had mainly been obtained from X-ray free electron laser (XFEL) or synchrotron radiation, which are high energy consumption, high cost and huge volume. Here we propose a low-cost and small-size method to generate X-ray source. We experimentally obtained high photon energy spectrum (~ 5.2 keV) through both atom and multiple valence state ions using a near-infrared 1.45 μm driving laser interacting with krypton gas, according to our knowledge, which is the highest photon energy generated through high-order harmonic generation up to now. In our scheme, multi-keV photon energy can be achieved with a relaxed requirement on experimental conditions, and make time-resolved studies more accessible to many laboratories that are capable of producing high energy photon extending to hard x-ray region. Furthermore, our scheme minimizes the influence of X-ray fluorescence process on detection, and can also be utilized to study the quantum-optical nature of high-order harmonic generation.

physics.optics↗

arXiv2022

Improving the accuracy of hard photon emission by Sigmoid sampling of the QED-table in particle-in-cell-Monte-Carlo simulations

Research on laser-plasma interaction in the quantum-electrodynamic (QED) regime has been greatly advanced by particle-in-cell & Monte-Carlo simulations (PIC-MC). While these simulations are widely used, we find that noticeable numerical error arises due to inappropriate implementation of the quantum process accounting for hard photon emission and pair production in the PIC-MC codes. The error stems from the low resolution of the QED table used to sample photon energy, which is generated in the logarithmic scale and cannot resolve high energy photons. We propose a new sampling method via Sigmoid function that handles both the low energy and high energy end of the photon emission spectrum. It guarantees the accuracy of PIC-MC algorithms for hard photon radiation and other related processes in the strong-field QED regime.

physics.comp-ph↗

arXiv2022

Diffraction properties of lights with transverse orbital angular momentum

Spatiotemporal optical vortex (STOV) is a unique optical vortex with phase singularity in the space-time domain and the photons in a STOV can carry transverse orbital angular momentum (OAM). The STOV shows many fantastic properties which are worth exploring. Here, we theoretically and experimentally study the diffraction property of STOV, which is a fundamental wave phenomenon. The diffraction behaviors of STOVs are obviously affected by the transverse OAM. The diffraction patterns of STOV pulses diffracted by a grating show multi-lobe structure with each gap corresponding to 1 topological charge. The diffraction properties of lights with transverse OAM are demonstrated clearly and help us understanding the physical properties of STOV, which will be of special applications, such as the realization of fast detection of STOVs with different topological charges, which may pay the way for STOV based optical communication.

physics.optics↗

arXiv2022

Multistep pulse compressor based on single-pass single-grating-pair main compressor

A multistage smoothing multistep pulse compressor (MPC) based on a single-pass single-grating-pair (SSGP) main compressor is proposed to simplify the entire petawatt (PW) compressor. Only one grating pair with relatively long distance is used to generate the same amount of spectral dispersion in the main compressor compared with a four-grating main compressor. As the SSGP induces the largest spatial dispersion, it can introduce the best beam-smoothing effect to the laser beam on the last grating. When considering the diffraction loss of only two gratings, the total compression efficiency of the SSGP main compressor is even larger than that of a four-grating main compressor. Furthermore, the spatiotemporal aberration induced by single-grating-pair can be compensated effectively by using deformable mirrors, however it is difficult or complicated to be well compensated in a four-grating compressor. Approximately 50-100 PW laser pulses can be obtained using this SSGP-based multistage smoothing MPC with a single laser beam

physics.optics↗