Intensity Laser-matter Interaction Research Articles

Recent advances in high-order harmonic generation from laser-ablated plumes at the advanced laser light source laboratory

High-order harmonic generation is a nonlinear optical frequency conversion process that occurs during intense ultrafast laser-matter interaction. At the Advanced Laser Light Source laboratory, we use ultrafast laser pulses having diverse wavelengths, spanning visible, near- and mid-infrared ranges, to generate high-order harmonics from laser-ablated plumes in the extreme ultraviolet or soft X-ray region of the electromagnetic spectrum. The Advanced Laser Light Source Laboratory is situated within the Énergie Matériaux Télécommunications Center of the Institut national de la recherche scientifique in Montréal, Quebec, Canada. We focus on generating bright and broadband harmonics by exploiting various types of ultrafast resonances in different species within the laser-ablated plume, and use them for applications in ultrafast spectroscopy, imaging, and AMO science. We are also actively exploring previously unknown physics governing the harmonic generation from different resonances. In this review article, we provide an overview of the recent advancements made in these directions.

Stability and debris-mitigation of a solid tape target delivery system for intense laser-matter interactions towards high-repetition-rate

The VEGA-3 laser system at the Centro de Láseres Pulsados delivers laser pulses up to 1 PW at 1 Hz repetition rate, focused to intensities up to 2.5×1020 W cm−2. A versatile and compact solid target suitable for up to 0.05 Hz is presented which can operate in the challenging petawatt laser environment close to the laser-plasma interaction. Strips are spooled in a tape target system to deliver a solid density target to the laser focus for every shot. Results are presented for different tape materials and thicknesses, and a shot-to-shot standard deviation of the cut-off energy of 1.5% was obtained for Kapton reinforced aluminium tapes of 9 µm thickness. Experimental ion spectra are recorded by a Thomson Parabola Ion Spectrometer coupled with a scintillator screen; and an antenna array is used for the characterization of electromagnetic pulses. The results of both diagnostics show a good shot-to-shot stability of the system.

Probing the electron motion in molecules using forward-scattering photoelectron holography.

Charge migration initiated by the coherent superposition of several electronic states is a basic process in intense laser-matter interactions. Observing this process on its intrinsic timescale is one of the central goals of attosecond science. Here, using forward-scattering photoelectron holography we theoretically demonstrate a scheme to probe the charge migration in molecules. In our scheme, by solving the time-dependent Schrödinger equation, the photoelectron momentum distributions (PEMDs) for strong-field tunneling ionization of the molecule are obtained. For a superposition state, it is shown that an intriguing shift of the holographic interference appears in the PEMDs, when the molecule is aligned perpendicularly to the linearly polarized laser field. With the quantum-orbit analysis, we demonstrate that this shift of the interference fringes is caused by the time evolution of the non-stationary superposition state. By analyzing the dependence of the shift on the final parallel momentum of the electrons, the relative phase and the expansion coefficient ratio of the two electronic states involved in the superposition state are determined accurately. Our study provides an efficient method for probing the charge migration in molecules. It will facilitate the application of the forward-scattering photoelectron holography to survey the electronic dynamics in more complex molecules.

Single Shot Generation of High‐Aspect‐Ratio Nano‐Rods from Sapphire by Ultrafast First Order Bessel Beam

AbstractEngineering the polarization and spatial phase of ultrafast laser pulses represents a compelling strategy for enhancing control over laser–matter interaction and enabling rapid and innovative nano‐fabrication processes. Here, the single‐shot, ultrafast laser fabrication of high‐aspect‐ratio, vertically standing nano‐pillars with a diameter of nm and height up to 15 µm on the surface of sapphire, is reported. To achieve this, the distinctive properties of diffraction‐free, first‐order Bessel beams endowed with either radial or azimuthal polarization distributions, are harnessed under tight focusing conditions. The highly intense laser–matter interaction in this configuration generates a tubular‐shaped, high‐pressure field beneath the material surface, leading to the rapid expulsion of material across the surface. Three distinct regimes for the pillar generation are identified in addition to a mechanism based on the Rayleigh‐Plateau theory that explains the distinct morphological regimes observed. The findings not only shed light on the underlying physical mechanisms of intense excitation of transparent dielectrics but also offer exciting prospects for the rapid fabrication of positive nano‐structures and material compression across various fields of application.

Quantum Electrodynamics of Intense Laser-Matter Interactions: A Tool for Quantum State Engineering

Intense laser-matter interactions are at the center of interest in research and technology since the development of high-power lasers. They have been widely used for fundamental studies in atomic, molecular, and optical physics, and they are at the core of attosecond physics and ultrafast optoelectronics. Although the majority of these studies have been successfully described using classical electromagnetic fields, recent investigations based on fully quantized approaches have shown that intense laser-atom interactions can be used for the generation of controllable high-photon-number entangled coherent states and coherent state superpositions. In this tutorial, we provide a comprehensive fully quantized description of intense laser-atom interactions. We elaborate on the processes of high-harmonic generation, above-threshold ionization, and we discuss new phenomena that cannot be revealed within the context of semiclassical theories. We provide the description for conditioning the light field on different electronic processes, and their consequences for quantum state engineering of light. Finally, we discuss the extension of the approach to more complex materials, and the impact to quantum technologies for a new photonic platform composed of the symbiosis of attosecond physics and quantum information science.12 MoreReceived 30 June 2022DOI:https://doi.org/10.1103/PRXQuantum.4.010201Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum description of light-matter interactionQuantum engineeringAtomic, Molecular & OpticalQuantum Information

Review on the Reconstruction of Transition Dipole Moments by Solid Harmonic Spectrum

In the process of intense laser–matter interactions, the transition dipole moment is a basic physical quantity at the core, which is directly related to the internal structure of the solid and dominates the optical properties of the solid in the intense laser field. Therefore, the reconstruction of the transition dipole moment between solid energy bands is extremely important for clarifying the ultrafast dynamics of carriers in the strong and ultrashort laser pulse. In this review, we introduce recent works of reconstructing transition dipole moment in a solid, and the advantages and drawbacks of different works are discussed.

Radiation pressure acceleration of high-quality ion beams using ultrashort laser pulses

The generation of compact, high-energy ion beams is one of the most promising applications of intense laser-matter interactions, but the control of the beam spectral quality remains an outstanding challenge. We show that in radiation pressure acceleration of a thin solid target the onset of electron heating is determined by the growth of the Rayleigh-Taylor-like instability at the front surface and must be controlled to produce ion beams with high spectral quality in the light sail regime. The growth rate of the instability imposes an upper limit on the laser pulse duration and intensity to achieve high spectral beam quality and we demonstrate that under this optimal regime, the maximum peak ion beam energy per nucleon is independent of target density, composition, and laser energy (transverse spot size). Our predictions are validated by two- and three-dimensional particle-in-cell simulations, which indicate that for recent and upcoming experimental facilities using ultrashort ($\lesssim 25$ fs) laser pulses it is possible to produce $100 - 300$ MeV proton beams with $\sim 30\%$ energy spread and high laser-to-proton energy conversion efficiency.

High Photon Number Entangled States and Coherent State Superposition from the Extreme Ultraviolet to the Far Infrared.

We present a theoretical demonstration on the generation of entangled coherent states and of coherent state superpositions, with photon numbers and frequencies orders of magnitude higher than those provided by the current technology. This is achieved by utilizing a quantum mechanical multimode description of the single- and two-color intense laser field driven process of high harmonic generation in atoms. It is found that all field modes involved in the high harmonic generation process are entangled, and upon performing a quantum operation, lead to the generation of high photon number optical cat states spanning from the far infrared to the extreme ultraviolet spectral region. This provides direct insights into the quantum mechanical properties of the optical field in the intense laser matter interaction. Finally, these states can be considered as a new resource for fundamental tests of quantum theory, quantum information processing, or sensing with nonclassical states of light.

An Abundance of Extremely Large Clusters as a Target for Intense Laser-Matter Interaction

An Abundance of Extremely Large Clusters as a Target for Intense Laser-Matter Interaction

High sensitivity Thomson spectrometry: analysis of measurements in high power picosecond laser experiments

Thomson spectrometers (TS) are designed to detect and distinguish protons from heavier ions in experiments of intense laser-matter interaction. The combination of electric and magnetic field allows for deflecting ion species with different mass-to-charge ratio on different trajectories. However, even small distortions of the internal fields of the device can lead to a degradation of the measurement quality. Hence, TS are sensitive to both high electromagnetic pulses (EMPs) and fields due to static charge accumulation caused by the interaction. Here we report on the analysis of data obtained with a TS designed to have high sensitivity and robustness with, optimized shielding against EMPs, even when the device is placed at short distances from the interaction point, where the electromagnetic radiation is more intense. To test this, the spectrometer was thus placed ∼50 cm far from the target during an experiment at the PHELIX laser at GSI (∼180 J energy, >1020 W/cm2 intensity, sub-picosecond laser pulses on solid targets). Despite the presence of strong EMPs (beyond 100 kV/m at 1 m distance from the target), the tests were successful and the TS was able to retrieve a good-quality signal. Indeed, the close proximity to the interaction point caused a significant number of electrons, produced by the intense laser-target interaction, entering the TS and causing internal electrostatic fields up to tens of kV/m. These induced fields altered the trajectories of the detected ions, making the interpretation and characterization of the particle species not straightforward. This effect was analyzed with ad-hoc particle tracking simulations. This study is of high importance for the effective implementation of this type of high-sensitivity TSs in experiments with PW-power lasers.

Intense laser matter interaction in atoms, finite systems and condensed media: recent experiments and theoretical advances

This special issue of the European Journal of Physics: Special Topics entitled “Intense Laser Matter Interaction in Atoms, Finite Systems and Condensed Media” published a set of 21 articles aiming to put in perspective this burgeoning area of science, application and technology. The invention of chirped pulse amplification by Strickland and Mourou, which led to their Nobel prizes in 2018, has ushered in a new era in photon–matter interaction where coherent intense light pulses in the optical and infrared domains play a central role. This development has not only called in creative experimental methods, but has demanded new theoretical approaches working in the non-perturbative and highly nonlinear regimes of light–matter interaction. Both for fundamental physics as well as key applications these have played an essential role. Key pillars of this subject, captured in this collection, are laser-induced nanometer-scale plasmas ignited in unsupported nanoparticles, laser-based particle acceleration taking advantage of unprecedented field gradients, the generation of high-order harmonics opening up attosecond science and ultrafast X-ray spectroscopy, and the generation of terahertz pulses for time-domain spectroscopy of new materials.

Generation of optical Schrödinger cat states in intense laser–matter interactions

The physics of intense laser-matter interactions is described by treating the light pulses classically, anticipating no need to access optical measurements beyond the classical limit. However, the quantum nature of the electromagnetic fields is always present. Here, we demonstrate that intense laser-atom interactions may lead to the generation of highly non-classical light states. This was achieved by using the process of high-harmonic generation in atoms, in which the photons of a driving laser pulse of infrared frequency are up-converted into photons of higher frequencies in the extreme ultraviolet spectral range. The quantum state of the fundamental mode after the interaction, when conditioned on the high-harmonic generation, is a so-called Schr\"odinger cat state, which corresponds to a superposition of two distinct coherent states: the initial state of the laser and the coherent state reduced in amplitude that results from the interaction with atoms. The results open the path for investigations towards the control of the non-classical states, exploiting conditioning approaches on physical processes relevant to high-harmonic generation.

Absorption of high-intensity, high-contrast femtosecond laser pulses by a dielectric solid

Basic understanding of high-intensity femtosecond laser absorption by a solid is crucial for high-energy-density science. This multidimensional problem has many variables like laser parameters, solid target material, and geometry of the excitation. This study is important for a basic understanding of intense laser-matter interaction as well for applications such as ‘plasma mirror’. Here, we experimentally observe high-contrast femtosecond laser absorption by an optically polished fused silica target at near-relativistic laser intensities (∼1018 W cm−2). Laser absorption as a function of angle of incidence and incident energy is investigated for both p- and s-polarized pulses in detail, providing a strong indication of the presence of collisionless processes. At an optimum angle of incidence, almost 80% of the p-polarized laser energy gets absorbed by the target. We also observed high reflectivity (∼60%) at lower angle of incidence (30∘) for both the polarization of laser, indicating this study is fundamentally important for ‘plasma mirrors’ at near-relativistic intensities.

Quantum-Optical Spectrometry in Relativistic Laser–Plasma Interactions Using the High-Harmonic Generation Process: A Proposal

Quantum-optical spectrometry is a recently developed shot-to-shot photon correlation-based method, namely using a quantum spectrometer (QS), that has been used to reveal the quantum optical nature of intense laser–matter interactions and connect the research domains of quantum optics (QO) and strong laser-field physics (SLFP). The method provides the probability of absorbing photons from a driving laser field towards the generation of a strong laser–field interaction product, such as high-order harmonics. In this case, the harmonic spectrum is reflected in the photon number distribution of the infrared (IR) driving field after its interaction with the high harmonic generation medium. The method was implemented in non-relativistic interactions using high harmonics produced by the interaction of strong laser pulses with atoms and semiconductors. Very recently, it was used for the generation of non-classical light states in intense laser–atom interaction, building the basis for studies of quantum electrodynamics in strong laser-field physics and the development of a new class of non-classical light sources for applications in quantum technology. Here, after a brief introduction of the QS method, we will discuss how the QS can be applied in relativistic laser–plasma interactions and become the driving factor for initiating investigations on relativistic quantum electrodynamics.

Combined laser-based X-ray fluorescence and particle-induced X-ray emission for versatile multi-element analysis

Particle and radiation sources are widely employed in manifold applications. In the last decades, the upcoming of versatile, energetic, high-brilliance laser-based sources, as produced by intense laser–matter interactions, has introduced utilization of these sources in diverse areas, given their potential to complement or even outperform existing techniques. In this paper, we show that the interaction of an intense laser with a solid target produces a versatile, non-destructive, fast analysis technique that allows to switch from laser-driven PIXE (Particle-Induced X-ray Emission) to laser-driven XRF (X-ray Fluorescence) within single laser shots, by simply changing the atomic number of the interaction target. The combination of both processes improves the retrieval of constituents in materials and allows for volumetric analysis up to tens of microns and on cm2 large areas up to a detection threshold of ppms. This opens the route for a versatile, non-destructive, and fast combined analysis technique.

Realization of laser intensity over 1023 W/cm2

High-intensity lasers are critical for the exploration of strong field quantum electrodynamics. We report here a demonstration of laser intensity exceeding 1 0 23 W / c m 2 with the CoReLS petawatt (PW) laser. After wavefront correction and tight focusing with a two-stage adaptive optical system and an f/1.1 ( f = 300 m m ) off-axis parabolic mirror, we obtained near diffraction-limited focusing with a spot size of 1.1 µm (FWHM). From the measurement of 80 consecutive laser shots at 0.1 Hz, we achieved a peak intensity of ( 1.1 ± 0.2 ) × 1 0 23 W / c m 2 , verifying the applicability of the ultrahigh intensity PW laser for ultrahigh intensity laser–matter interactions. From the statistical analysis of the PW laser shots, we identified that the intensity fluctuation originated from air turbulence in the laser beam path and beam pointing. Our achievement could accelerate the study of strong field quantum electrodynamics by enabling exploration of nonlinear Compton scattering and Breit–Wheeler pair production.

Dispersion calibration for the National Ignition Facility electron-positron-proton spectrometers for intense laser matter interactions.

Electron-positron pairs, produced in intense laser-solid interactions, are diagnosed using magnetic spectrometers with image plates, such as the National Ignition Facility Electron-Positron-Proton Spectrometers (EPPSs). Although modeling can help infer the quantitative value, the accuracy of the models needs to be verified to ensure measurement quality. The dispersion of low-energy electrons and positrons may be affected by fringe magnetic fields near the entrance of the EPPS. We have calibrated the EPPS with six electron beams from a Siemens Oncor linear accelerator (linac) ranging in energy from 2.7 MeV to 15.2 MeV as they enter the spectrometer. A Geant4 traveling-wave optical parametric amplifier of superfluorescence Monte Carlo simulation was set up to match depth dose curves and lateral profiles measured in water at 100cm source-surface distance. An accurate relationship was established between the bending magnet current setting and the energy of the electron beam at the exit window. The simulations and measurements were used to determine the energy distributions of the six electron beams at the EPPS slit. Analysis of the scanned image plates together with the determined energy distribution arriving in the spectrometer provides improved dispersion curves for the EPPS.

Automation of Target Delivery and Diagnostic Systems for High Repetition Rate Laser-Plasma Acceleration

Fast solid target delivery and plasma-ion detection systems have been designed and developed to be used in high intensity laser-matter interaction experiments. We report on recent progress in the development and testing of automated systems to refresh solid targets at a high repetition rate during high peak power laser operation (>1 Hz), along with ion diagnostics and corresponding data collection and real-time analysis methods implemented for future use in a plasma-based ion acceleration beamline for multidisciplinary user applications.

Research progress of high-order harmonics and attosecond radiation driven by interaction between intense lasers and plasma

The realizing of the detection and control of ultrafast process conduces to understanding and remoulding the physical world at a microcosm level. The attosecond light source with attosecond temporal resolution and nanometer spatial resolution can realize real-time detection and manipulation of the atomic-scale electronic dynamics and relevant effects of the substances. Therefore, attosecond science is considered as one of the most important milestones in the history of laser science. and has been listed as an important scientific and technological development direction in the coming 10 years. High-order harmonic generation (HHG) from intense laser-matter interaction is one of the most important routes to breaking through the femtosecond limit and achieving brilliant attosecond pulse radiations, and thus having aroused great interest in recent years. After more than 20-year development, the research about attosecond pulse generation by laser-gas interaction has reached a mature stage. This method produces the shortest isolated pulse in the world to date, with a pulse width being only 43 as. However, this method based on ionization-acceleration-combination encounters inevitable difficulties in pursuing the relativistically intense attosecond pulses and the highest possible photon energy. Quite a lot of studies have proved that the HHG efficiency from laser-plasma interaction can be a few orders of magnitude higher than that in gaseous media, which makes it possible to produce pulses with shorter pulse width and higher photon energy. In this article, we introduce the main generation mechanisms, research progress and frontier applications of HHG through the laser-plasma interaction process. In Section 2, we introduce the HHG generation mechanisms, including coherent wake emission, which is used to describe the HHG process driven by a nonrelativistic laser; relativistic oscillating mirror, which can well explain most of HHG processes generated from plasma-vacuum interface in relativistic regime; coherent synchrotron emission, which is suited to explain the HHG synchronously emitted from isolated electron sheets. The research progress is summarized in Section 3 from the aspects of radiation efficiency, polarization characteristics, phase characteristics, generation and diagnosis of isolated attosecond pulses, etc. Frontier applications of these ultra-broadband intense attosecond pulses are presented in the last section, such as the study of electronic dynamics, process, coherent diffraction imaging, diagnosis of extreme states of matter, the generation of extremely intense fields, etc. Finally, an outlook on the future development trends and innovation breakthroughs is also presented.

Self-focusing and self-compression of intense pulses via ionization-induced spatiotemporal reshaping.

Ionization is a fundamental process in intense laser-matter interactions and is known to cause plasma defocusing and intensity clamping. Here, we investigate theoretically the propagation dynamics of an intense laser pulse in a helium gas jet in the ionization saturation regime, and we find that the pulse undergoes self-focusing and self-compression through ionization-induced reshaping, resulting in a manyfold increase in laser intensity. This unconventional behavior is associated with the spatiotemporal frequency variation mediated by ionization and spatiotempral coupling. Our results illustrate a new regime of pulse propagation and open up an optics-less approach for raising laser intensity.