This PDF file contains the front matter associated with SPIE Proceedings Volume 12939, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Understanding the dynamics of electron-phonon and phonon-phonon interactions is important to unravel the complex behavior of materials subject to ultrafast laser excitation. We report the results of studying these interactions in femtosecond laser-excited tungsten (W) using the technique of ultrafast electron diffuse scattering (UEDS). By tracking changes of diffuse scattering signal over time, we resolve the dynamics of phonon populations across the Brillouin zone in W. Our results shed light on both electron-phonon and phonon-phonon coupling dynamics in W [Mo et al. Science Advances, in press (2024)]. This paper outlines the fundamental principle behind the UEDS technique, provides a brief overview of the experimental setup, and presents selected results of time-resolved diffuse scattering patterns.

Volumetric modification of glass materials by ultrashort laser pulses is a powerful technique enabling direct writing of three-dimensional structures for fabrication of optical, photonic, and microfluidic devices. The level of modification is determined by the locally absorbed energy density, which depends on numerous factors. In this work, the effect of the spatial pulse shape on the ultrashort laser excitation of fused silica was investigated experimentally and theoretically for the volumetric modification regimes. We focused on two shapes of laser pulses, Gaussian and doughnut-shaped (DS) ones. It was found that, at relatively low pulse energies, in the range of ~1–5 microjoules, the DS pulses are more efficient in volumetric structural changes than Gaussian pulses. It is explained by the intensity clamping effect for the Gaussian pulses, which leads to the delocalization of the laser energy absorption. In the DS case, this effect is overcome due to the geometry of the focused beam propagation, accompanied by the electron plasma formation, which scatters light toward the beam axis. The thermoelastoplastic modeling performed for the DS pulses revealed intriguing dynamics of the shock waves generated because of tubular-like energy absorption. It is anticipated that such a double shock wave structure can induce the formation of high-pressure polymorphs of transparent materials that can be used for investigations of nonequilibrium thermodynamics of warm dense matter. The DS laser pulses of low energies of the order of 100 nJ which generate a gentle tubular-like modification can be perspective for a miniature waveguide writing in glass.

In high-power pulsed laser ablation of metals, the material removal usually occurs in the regime of volumetric boiling, when the ablated materials form two-phase plasma plumes composed of neutral atoms, ions, electrons, and a large fraction of nanoparticles/clusters. To predict the effect of plasma shielding induced by absorption of laser radiation in such twophase plumes, a hybrid multi-phase computational model is developed. The model includes a thermal model of the irradiated target, a model of non-equilibrium ionization of gaseous plasma plume based on the collision-radiation plasma model, and a kinetic equation that describes the distribution of cluster sizes and temperatures. The model accounts for the fragmentation of the target material in the regime of volumetric boiling, evaporation and condensation of nanoparticles, as well as radiation absorption and scattering by all constituents of the plume. The model is used to evaluate the contributions of various factors on the degree of plasma shielding at laser ablation of a copper target irradiated by a nanosecond laser pulse. The simulations show that the radiation scattering by nanoparticles is the dominant mechanism of radiation attenuation. The cluster evaporation and attenuation of laser radiation by nanoparticles are found to have a strong effect on plume dynamics and plasma shielding.

An exciting use of high powered lasers is to inertially confine fusion plasmas in the laboratory. This presentation describes the first design to achieve controlled fusion target gain exceeding one using high powered lasers in the inertial confinement fusion approach and recent experimental results on the NIF (National Ignition Facility). In these experiments, laser beams incident on the inside of a cylindrical can (Hohlraum) generates an intense x-ray radiation bath that is used to spherically implode pellets containing Deuterium and Tritium. On Dec 5th 2022, the imploded pellet generated more fusion energy (3.15 MJ) than laser energy incident on the target (2.05 MJ), reaching a milestone for the field that was more than six decades in the making. Follow on experiments in this platform using 2.2 MJ of laser energy have generated >5 MJ and >2x target gain.

Surface properties of polymers are important for different applications such as their use as biomaterials, protective coatings, and thin film technology. We explore the formation of laser-induced periodic surface structures (LIPSS) on different polymers, investigating the influence of polymer nature, laser parameters, and environmental factors. By varying laser irradiation conditions, the study demonstrates control over LIPSS period and quality, surface chemistry, and properties like wettability, surface energy, and adhesion. Depending on the conditions, surface modifications can lead to increased hydrophilicity or hydrophobicity. These findings are essential for applications where surface interactions are crucial.

Ultrashort and short high-power laser pulses are employed to ablate metallic and oxide materials, to analyze their element composition by laser-induced breakdown spectroscopy (LIBS), and to grow complex oxide thin films by pulsedlaser deposition (PLD). With ultrashort femtosecond (fs) lasers the ablated mass per laser pulse can be reduced compared to short nanosecond lasers. This enables chemical imaging with high spatial resolution. The intensity of atomic emission lines in fs-LIBS spectra is correlated to the ablated mass for metal thin films on glass. The obtained limits of detection are 370 fg for Ag, 100 fg for Cu, and 14 fg for Na. LIBS measurements of industrial steel samples using nanosecond lasers reveal a surprisingly strong matrix effect. The line intensities of analyte elements like Mn are cross-sensitive to other elements like Si. This detrimental matrix effect is overcome when the laser-ablated sample is re-excited by an electric spark discharge (laser ablation-spark discharge-optical emission spectroscopy, LA-SD-OES). Thin films of quasi-2D high-temperature superconducting Bi₂Sr₂CaCu₂O_8+d are grown on LaAlO₃ substrates. The PLD films are epitaxial, stoichiometric, and single-phase and have high critical temperature and critical current densities.

The detection and quantification of hydrogen (^1,2,3H) and lithium (^6,7Li) isotopes are critical to several energy and defense application areas, including hydrogen storage, nuclear forensics, and safeguards/non-proliferation. In this context, laser-induced breakdown spectroscopy is a very promising technique and it comes with certain advantages such as rapid detection, and standoff capability. Although LIBS provides experimental simplicity and is capable of detecting all elements in the periodic table in any phase (solid, liquid, or gas), there exist certain challenges for isotopic analyses of H and Li due to spectral broadening, the presence of closely spaced fine and hyperfine structures, and line distortion effects (e.g., self-absorption and self-reversal) present in laser-produced plasmas. This article reports recent developments in H and Li isotopic analysis using LIBS, and existing challenges.

Interactions of intense ultrashort laser pulses with liquid media and at solid-liquid interfaces produce plasmas with high densities of reactive chemical species that promote the formation of nanomaterials. This work discusses the current understanding of laser-induced chemical reactions in aqueous medium involving hydrated electrons and hydroxyl radicals, and the effects of chemical additives on these reactions. Two chemical strategies are presented for controlling the composition of the laser-induced plasma and nanomaterial properties. First, adding chemical scavengers of hydroxyl radicals will be shown to inhibit metal oxidation, enabling the synthesis of ligand-free Ag and Au-Ag alloy nanoparticles by reduction of Au and Ag salts. Second, ablating a silicon wafer in a solution containing two metal salts with different reduction potentials will be shown to enhance the deposition of the high-reduction potential metal onto the ablated silicon surface, producing high densities of metal nanostructures on silicon laser-induced periodic surface structures (LIPSS).

Metal Halide Perovskites (MHPs) have garnered significant attention for several attractive properties, making them suitable for numerous applications, including light-emitting devices, lasers, photodetectors, solar cells, and radiation detectors. This study focuses on the deposition of MHPs via pulsed laser ablation (PLD), with a particular emphasis on CsPbBr₃/Cs₄PbBr₆ films. The robust stability of PLD-deposited Cs-Pb-Br-based films over two years is demonstrated through an examination of their structural, optical, and emission properties of the films. They retain UV-Vis absorption characteristics and crystalline phases, with only a slight variation in peak intensity. Notably, a robust emission at 520 nm under 395 nm diode laser excitation is recorded two years after deposition, even without the presence of a protective layer. Our study point out that the choice of the deposition conditions is a critical factor to obtain film stability over time. Specifically, the films are deposited using a KrF laser beam at a background pressure of 10^-2 Pa and a target-substrate distance of 3 cm. The rationale behind choosing these conditions is discussed in relation to the unique aspects of the deposition process and their interplay with perovskite physics.

Pulsed Laser Deposition (PLD) is a thin film deposition technique especially well adapted to binary or ternary oxides. Classically, PLD deposition was limited to small sample sizes (about 10 x 10 mm²) due to the small spatial extension of the plume. Being a hindrance for the application of PLD grown thin films in industrial applications, PLD machines allowing for larger deposition areas have been developed, by scanning the laser on a larger target and rotating the sample above the ablated area. This set-up adds other parameters, as for example the laser scan speed and the rotation speed to the typical deposition parameters, and we have used the new transparent conductor SrVO3 as a prototypical system to control the homogeneity of monocrystalline and polycrystalline thin films on a 4-inch area.

We report on the progress of Pulsed Laser Deposition growth of thin films by using a high-power Nd:YAG laser source. We demonstrate that by using the fundamental wavelength at 1064 nm, the congruent ablation of a large number of materials can be successfully achieved. Even if the infra-red radiation of the fundamental harmonics of Nd:YAG lasers - corresponding to impinging photons with energy of about 1.16 eV - is unexpectedly proved to be also absorbed by insulating materials characterized by a large value of the band-gap (e.g. 3.0 eV for rutile TiO2). Combined investigation of structural properties by transmission electron microscopy and scanning electron microscopy provides evidence of the very high-quality thin films grown by Nd:YAG lasers with no trace of precipitates and droplets over a scale of tens of micrometers.

Systems of combined high-power fiber amplifiers form the basis for the High Energy Laser (HEL) systems used in military directed energy applications. In this paper we review the current state-of-the-art for these combinable, building-block, fiber amplifiers and discuss the fundamental challenges in power scaling HEL systems.

We discuss methods and lessons learned during the integration and testing of five individual kW-class fiber amplifiers seeded with pseudorandom phase-modulated light, using a 1x5 Diffractive Optical Element (DOE). Each amplifier is capable of producing approximately 1.2 kW of near diffraction-limited output power (M2 <1.1). Low power samples from each amplifier are used for active polarization control. Phase control of each amplifier was accomplished using a low power combined beam sample and AFRL’s Locking of Optical Coherent via Single-detector Electronic-frequency Tagging (LOCSET) control system. Approximately 5 kW of signal output was achieved with a combined efficiency of 82%. Losses in the system arise from DOE efficiency limitations, Amplified Spontaneous Emission (ASE), polarization errors, uncorrelated wavefront errors, optical path length mismatches, and beam misalignments. We discuss the impact of recent amplifier developments and how these developments impact this beam combining method.

A study of damage and ablation of silicon induced by two individual femtosecond laser pulses of different wavelengths, 1030 and 515 nm, is performed to address the physical mechanisms of dual-wavelength ablation and reveal possibilities for increasing the ablation efficiency. The produced ablation craters and damaged areas are analyzed as a function of time separation between the pulses and are compared with monochromatic pulses of the same total energy. Particular attention is given to low-fluence irradiation regimes when the energy densities in each pulse are below the ablation threshold and thus no shielding of the subsequent pulse by the ablation products occurs. The sequence order of pulses is demonstrated to be essential in bi-color ablation with higher material removal rates when a shorter-wavelength pulse arrives first at the surface. At long delays of 30-100 ps, the dual-wavelength ablation is found to be particularly strong with the formation of deep smooth craters. This is explained by the expansion of a hot liquid layer produced by the first pulse with a drastic decrease in the surface reflectivity at this timescale. The results provide insight into the processes of dual-wavelength laser ablation offering a better control of the energy deposition into material.

Long-wave infrared (LWIR) lasers based on high-voltage pulsed discharges in the high-pressure CO₂ gas have reached multi-TW peak power. As optical pumping appears to be a more viable pathway toward ultrahigh power and high repetition rate, we investigated multiple apparatus including direct and indirect optical pumping. Indirect optical pumping through stimulated Raman scattering in N₂ gas could be efficient, and is relatively insensitive to the pump wavelength. On the other hand, laser technologies for direct optical pumping have higher maturity levels at wavelengths of ~ 1.4 μm and ~ 2.0 μm among multiple excitation bands in the mid-IR wavelength.

Amplifying ps-laser radiation to high pulse-energies as well as a high average output power is a challenging task. In the past it was shown that thin-disk multipass amplifiers can achieve excellent properties for ultrashort laser pulses at over 1 kW of average power. Furthermore, systems combining multipass and regenerative thindisk amplifiers achieved 700 mJ of pulse energy at a repetition rate of 1000 Hz. These systems reaching such excellent properties are complex, extensive and typically need dozens of mirror-optics and the corresponding space associated with those. With the introduction of our monolithic wedged thin-disk (WTD) concept we were able to demonstrate small signal laser amplification of up to 10 (+10 dB) for cw-systems with a drastically reduced amount of mirror optics as well as space needed. By adding a redirecting mirror to introduce two multipasses in the WTD we were able to amplify a 2 ps-laser source with a small signal gain of up to 55 (+17 dB) and at 20W seed power by a factor of 5 (+7 dB) reaching up to 100W of output power.

Laser interaction with a metal excites electrons into a non-equilibrium state after which the path back to equilibrium is determined by the scattering of electrons and phonons. We present a computational study of such a process in a metallic system showing the role of electron-phonon and phonon-phonon coupling. Our modelling approach incorporates realistic momentum resolved electron-phonon coupling in a classical molecular dynamics simulation. In addition, the phonon-phonon scattering is controlled by varying the anharmonicity of the interatomic potential. Our results show that both electron-phonon and phonon-phonon couplings are important in order to match experimental measurements.

The rapidly increasing amount of space debris is a critical problem of modern and future space infrastructure. Repetitively pulsed high energy lasers are frequently discussed as a technological option for the remotely based removal of multiple small space debris objects from the low Earth orbit (LEO) by recoil from laser ablation. Aiming for a realistic assessment of the concept’s efficiency in debris mitigation, awareness of thermal constraints is needed. In our study, we employ finite element analysis (FEM) of the laser ablation process regarding imparted momentum from laser-ablative recoil as well as laser-induced heat inside the target after ablation. The simulation results are underpinned by observations of velocity change and temperature increase from single pulse laser irradiation of cm-sized targets in a drop experiment in vacuum (10 ns pulse duration, 1064 nm wavelength, 60 J nominal pulse energy) from the nhelix laser of the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. Both polished and sandblasted samples of common space debris materials like aluminum, copper, steel, and titanium are employed in our analysis. Our findings suggest that exhaustive target reconnaissance is required to ensure operational safety in laser-based orbit modification regarding predictability of the modified trajectory as well as thermal constraints in target heating.

For a proper understanding of laser shock applications, it is necessary to explore new experimental configurations and push forwards the range of configurations available. It is also important to develop theoretical and numerical models to guide these experiments, helping to reach new developments. In the present work, the latest advancements concerning laser-matter interaction will be introduced and discussed. New models were developed, associated with their experimental demonstration, concerning the expansion of a laser-induced plasma in the case of small focal spots. Furthermore, when applying a high overlapping ratio between laser shots, the material reaction to the thermal loading of the plasma was spatially resolved, helping to thwart detrimental thermal effects. Finally, a new configuration for the interaction itself, using a water tank, was also implemented and shown an increase up to 2 times of the intensity threshold for the breakdown inside the water confinement.

Laser-assisted surface structuring was developed at CERN for the treatment of the inside wall of the vacuum system of the Large Hadron Collider (LHC). 50-µm-deep grooves were created by material ablation while the laser scanned the surface. A part of this material was redeposited as micrometer-size particle aggregates. This two-scale rugosity efficiently traps electrons. During the operation of the LHC, the surface is submitted to high electromagnetic forces and cooling cycles which might deteriorate its performances. Accelerations of the surface in the order of 350 000 g are expected to be induced by these electromagnetic forces. The LAser Shock Adhesion Test (LASAT), initially developed to assess the adhesion of coatings by spallation, was used to accelerate the surface of treated samples, in order to reproduce stress states similar to those generated by the electromagnetic forces. Pressure shock waves generated by nanosecond laser irradiation produce sharp velocity variations of the surface. Decelerations and, therefore, applied inertial forces were evaluated from the dynamics of the sample macroscopic surface, whose velocity evolution was measurement by VISAR (Velocity Interferometer System for Any Reflector) with a time resolution smaller than 1 ns. Once the test set-up was calibrated, the collect and the analysis of detached particles allowed the quantification of ejected material as a function of the applied mechanical stresses.

In this paper, damage produced by lightning strike, laser shock and electron beam deposition on a protected Carbon Fiber Reinforced Plastic composite laminate is studied in order to find analogies of effects and damage between these experimental means. As lightning strike physics on CFRP coated with a Lightning Strike Protection and paint is not fully understood, these analogies could be able to enhance lightning strike modelling by potentially uncoupling the physics at hand and having access to additional measurement instruments. The different experimental setups are briefly described before analyzing the damage response of the aeronautical CFRP protected using an Expanded Copper Foil and coated in aeronautical paint. Eventually the results are compared to build potential analogies able to enhance lightning strike modelling.

Various capabilities of LP3 ASUR platform are presented with particular emphasis on the possibility to combine moderate and high-intensity laser beamlines for developing pump-probe approach with modular (optical/x-ray) time-resolved diagnostics. This unique and highly versatile combination in terms of laser excitation, laser – material arrangement and conditions, and in-operando diagnostics makes the ASUR platform an ideal tool for nurturing fundamental knowledge in laser – material interaction and for innovative laser-driven engineering of materials and devices.

The BELLA PW Facility’s (LBNL, Berkeley CA/USA) recent laser system upgrades provide new capabilities for 1) ultrahigh intensity experiments with solid targets at Interaction Point#2 [iP2]; and 2) staged laser plasma accelerator [LPA] studies at the Second Beamline [2BL]. An overview of the special considerations, planning and implementation processes related to radiation shielding, laser and radiation interlock systems required for the safe and efficient operation of the new BELLA PW beamlines and the conduction of efficient experimental campaigns are reviewed.

This research looks to enhance our understanding of the laser-material interaction within silicon, considering variations in free carrier density. Silicon exhibits distinct optical behaviors, ranging from transparency to non-transparency, contingent on its doping concentration, particularly at a 1064 nm wavelength. Our experimental investigation delves into the quantitative assessment of damage size and the qualitative characterization of damage morphology induced by singlepulse 1064 nm laser irradiation. In this experiment, we vary laser intensities and focal depths to show their influence on the damage features of single crystal silicon with varying doping concentrations. The damage size and qualitative characteristics can be used to better understand the mechanisms responsible for the laser damage. Additionally, we can see when the damaged silicon is exhibiting pure melting or a form of ordered damage at higher intensities. The findings of this study give insight into the optimization of laser processing techniques that require precise control over material ablation, and phase change as cutting and material joining. Furthermore, the insights garnered from this work contribute to a broader understanding of the interplay between laser parameters and material properties. This study represents a move towards unlocking the potential of laser-matter interactions in shaping the future of silicon advanced manufacturing technologies.

We report a comprehensive numerical study on laser-induced melting of copper applying the two-temperature description combined with molecular dynamics simulations (TTM-MD). It reveals the internal energy relaxation and melting dynamics of thin copper films irradiated with an ultrafast laser pulse. The TTM-MD simulations were performed utilizing different expressions for the electronic properties of copper including the temperaturedependent heat capacity and the electron-phonon coupling strength. We study the resulting melting times and structural evolution of the lattice that were found to vary in the picosecond range. The importance of the correct choice of the electron-phonon coupling parameter is underlined by its large influence on the heating and melting times of the lattice.

The present work considers the interaction of a continuous-wave (CW) laser with carbon-fiber reinforced polymers in the presence of a subsonic crossflow. A multi-physical approach has been developed to address this computational problem. The optical model of a plume has been coupled with the flow and material response model, encompassing the formation and transport of soot particulates. At given power densities of the laser beam the gaseous component of a plume is nearly transparent to the laser beam, and the laser beam shielding by a plume arises from soot particulates. Soot particulates do not reach the outer edge of the boundary layer due to a small diffusion coefficient compared to gaseous species. These particulates are swept downstream by the crossflow, creating a favorable window for the transmission of the laser energy to the material in terms of the crossflow velocity-laser power density envelope.

This study delves into advanced multi-beam technologies, focusing on the integration of Diffractive Optical Elements (DOEs) and Spatial Light Modulators (SLMs) in micro and nanostructuring. Significant productivity gains, surpassing traditional single-beam methods, are highlighted, illustrating the transformative impact of these technologies in the field. Specifically, DOE and SLM have been instrumental in applications ranging from biocompatibility enhancement in medical implants to friction reduction in machining tools. The research showcases the capability of these technologies to intricately tailor surface properties at micro and nano scales, opening new pathways in diverse sectors such as healthcare and manufacturing.

There is a scenario of strong field quantum electrodynamics where electron-positron pairs copropagating with an extremely intense laser mediate the continuous transformation of laser photons into directional gamma rays. This is made possible by a quasi-guiding equilibrium wherein the pairs are partially confined to the region of high intensity by quantum recoil. The laser parameters required to access this regime are far in advance of the current state of the art, but are made more plausible by operating at short wavelengths. Argon fluoride lasers are a possible route to accessing this regime.

Femtosecond laser allows the production of THz radiation that is very promising for the imaging of various tissues and, namely, for in vivo cancer detection. Despite numerous very convincing experimental demonstrations, the mechanisms involved in image formation are still under discussion. In this paper, based on modeling, we analyze the major physical processes involved in THz laser interactions with tissues, namely with skin. Particular attention is given to the mechanisms involved in integrated THz imaging with NIR femtosecond laser illumination. An effective medium approach is found to be helpful. The difference in water fraction, pores, and additional nanoparticles and nanorods are shown to play a role in the considered non-invasive optical imaging of skin cancer.

It is well documented that nonlinear optical systems can exhibit chaotic behavior. This behavior even appears in air when the light intensity is large enough. Chaotic behavior is well characterized by statistical means, because of sensitivity to initial conditions. Beam quality, 𝑀2 or the beam propagation parameter, is a key propagation parameter that is dependent on the spatial distribution of the optical field and deviations the medium makes from homogeneity or linearity. In order to better understand beam quality statistics for random fields in a nonlinear medium, an experimental system has been developed, and undergone initial testing. A Boston Micromachines Multi-DM 140 12x12 rectangular deformable mirror (DM) is used to induce phase screens on a 532nm visible beam, which then enters a lens-based beam profiling unit. Using computer controls and data pipelines, thousands of phase screened beams can be measured for beam quality automatically. Experimental testing shows stability of beam quality measurement across thousands of trials, and beam ensembles with long (of order beam size) coherence lengths to be feasible. Upon refinement of DM modeling with the insertion of a nonlinear medium the system can be made to test statistical models of nonlinear optics.

Intense underwater laser propagation is fundamental for many applications, e.g. laser surgery and laser acoustic generation. Meter-scale nonlinear propagation of picosecond ultraviolet pulses in water was measured and modeled. The SNOPROP code incorporates a 2D azimuthally-symmetric model of nonlinear laser pulse propagation in liquid water, solves coupled nonlinear Schrödinger propagation equations, and includes: stimulated Raman scattering, Kerr self-focusing, group-velocity dispersion, and both optical field and collisional cascade ionization. The SNOPROP liquid water chemistry model was recently augmented to include a set of energy-dependent cross sections, which it uses to calculate collisional rates and both conduction band electron density and temperature. Recent implementation of radially-varying computational grids is expected to improve SNOPROP efficiency, and comparison with published experimental data can provide validation. SNOPROP modeling fidelity will be enhanced by planned incorporation of ionization rates from ongoing experimental characterization of the nonlinear response of water.

Naturally occurring self-lasing of a confined plasma discharge is used as a plasma diagnostic. Together with other readily measurable parameters such as discharge voltage and current, the laser radiation provides the necessary constraints for fitting the parameters of a plasma chemistry model. The model determines the plasma density, electron temperature and excited-state populations as functions of time and space and shows excellent agreement with experiments performed in a nitrogen-filled discharge tube. Plasma self-lasing has been observed in a form of a ring and has a corresponding annular plasma density profile. This profile was used as initial conditions for diffusion model that predicts parabolic density at later times. Analysis of the parabolic profile shows that it can be employed for optical guiding of laser beams with spot radius ~mm.

We study the electron density response in gold after excitation with XUV and visible light. We have introduced the concept of occupational nonequilibrium and developed multiband rate equations that track the occupation in each active electron band. The rate equations also track the energy content of the sp- and d-electrons and can be coupled to the phonons. Our results show that visible light excitation leads to an overpopulation of the sp-band, driven primarily by photo-excitation, while XUV irradiation results in an underpopulation of the sp-band, dominated by subsequent impact ionization. However, assuming that the excess energy from the Auger recombination process is transferred to multiple d-electrons, we showcase that XUV-exited gold can lead to an overpopulation of the sp-band. In addition, using a detailed balance of Auger and impact ionization coefficients, we show that a single-rate relaxation time approach is sufficient to describe the imbalance between the impact ionization rate and the Auger recombination rate.

This study explores the effects of femtosecond laser pulses on Zinc Selenide (ZnSe), Germanium (Ge), and Silicon (Si), emphasizing laser-induced breakdown and the formation of Laser-Induced Periodic Surface Structures (LIPSS). Employing a 5.8 µm wavelength light at a 9 µJ per pulse energy, we document the ablation and structural changes in 5 mm thick samples. Our findings highlight the distinct responses of these materials to ultrafast, intense energy pulses, particularly noting the formation of LIPSS on ZnSe with a periodicity ∼1.5 times the wavelength of the incident light. These insights contribute to the broader understanding of material behavior under extreme laser conditions, offering avenues for advanced material patterning and surface engineering.

Pulsed laser technology is a green and versatile method to produce nanoparticles with tailored properties. In this work, pulsed laser ablation in liquids (PLAL) has been employed to generate nanoparticles (NPs) of titanium and zinc oxides. A Q-switched Nd:YAG laser (Quantel Brilliant B, wavelength 532 nm, pulses of 4 ns, repetition rate 10 Hz) was used to produce the ablation of the metal targets. The production on NPs was done in different liquids (water, methanol, ethanol, isopropanol and ethylene glycol), which present different thermal conductivities, viscosities, and chemical properties. A complete characterization of the NPs (UV/Vis, DLS, TEM, AFM, Raman) was carried out to evaluate the NPs formed.

Despite Neodymium laser systems being well-established and ever popular, there is motivation to improve gain and scale in inexpensive host materials such as Yttrium Aluminum Garnet (YAG) and Fine-Grain Al₂O₃. Thermal management through host materials with improved thermal properties is a promising pathway to stronger pumping and subsequently higher gain. Benefits of polycrystalline ceramic gain media, as well as various ceramic fabrication methods will be discussed. While polycrystalline Nd:YAG can be fabricated using traditional densification techniques of sintering and Hot Isostatic Pressing (HIP), in order to create polycrystalline Nd:Al₂O₃, one must turn to Current-Activated Pressure-Assisted Densification (CAPAD), a method of ceramic fabrication that utilizes high heating rates and pressure to reduce hold temperatures and times, reducing diffusion and subsequent grain growth.

This study compares the role of laser wavelength on the early time electron density evolution of the plasma following laser ablation using Nomarski interferometry. The laser-produced plasma was generated by focusing fundamental (1064 nm), second (532 nm), and fourth (266 nm) harmonic radiation from a 6 ns Nd:YAG laser at a laser intensity of 10 GW/cm² onto a copper target placed in vacuum. The dependence of plasma properties such as the electron density distribution, plume velocity, and plume morphology on the laser wavelength are discussed.

Zinctetraphenyporphyrine and Au nanoparticle-based nanocomposites (Au-ZnTPP) are examined for their nonlinear optical (NLO) behaviour and optical limiting property using z-scan experiment aiding pulsed laser that delivers 7ns pulses at 532 nm wavelength. The pulsed laser ablation on Au target in ZnTPP is the method of synthesis used for the nanocomposite preparation. ZnTPP with Au nanocomposite formation is confirmed from the quenching of the fluorescent emission spectrum and the modification of absorption spectrum. The introduction of the metal nanoparticle opens up additional energy transfer pathways, that can lead to enhanced excited-state absorption. Moreover, the augmentation is aided by local field effects of the Au NPs, contributes to increased interaction field strength on the surface of the NPs and the surrounding environment of the nanoparticle. The excited state absorption is revealed to be the major mechanism behind the observed nonlinear absorption and optical limiting activity. It is revealed that the suggested method could lead to the implementation of optical limiting-based devices suitable for photonic applications.