This talk will address the history of laser damage testing and how early measurement techniques have given way to current best practices and the development of those best practices across multiple wavelength ranges. The talk will discuss current methodologies, which have been driven by the development of the laser marketplace and the need for manufacturers and end users to qualify and assure components will meet the laser damage needs at the system level. The talk will conclude with novel measurement techniques and the direction of future work supporting the growth of laser technologies.

Remote sensing, range finding, optical communications have strong demand for compact, eye-safe lasers. Co2+:MgAl2O4 crystals can be used as a passive Q-switchers to obtain pulses of compact Er:glass lasers and might be one of the limiting factors, determining their maximum output power. This study presents oxygen plasma etching of commercially-polished Co2+:MgAl2O4 crystals, including investigation on their spectrophotometric, surface and LIDT (R(1)-on-1) properties using two different lasers and beam diameters - 172 µm and 55 µm at 1540 nm. Measurements higher fluence laser and smaller 55 µm laser beam diameter allowed determination of all etched crystals and revealed dramatic increase of their surface LIDT comparing to untreated sample.

The MELBA testbed located at CEA CESTA (France) is a nanosecond UV centimeter-sized beam aiming at studying laser damage. Previous work carried out on MELBA showed a dependency of laser-induced damage to power modulation of the laser pulse in linear propagation regime. We extended this study to the non-linear propagation regime. Thanks to dedicated imaging setup, we carried out an experimental study of Bespalov-Talanov gain and laser-induced damage with different temporal modulations. The tuning of phase modulation parameters made it possible to annihilate backward stimulated Brillouin scattering and consequently focus on the impact of the Kerr effect.

Ultrafast dynamics of ultrashort single pulse induced micro-explosions in bulk Diamond was examined using time resolved shadowgraphy technique in a pump-probe experimental setup. Experimental and theoretical considerations identify such confined micro-explosions creating Warm Dense Matter (WDM) state. Different phases of the ongoing micro-explosions have been captured in real-time with femtoseconds to picoseconds temporal and micron-sized spatial resolutions. This study broadens the horizon of our understanding of exotic matter generation process in extreme environments.

Cathodoluminescence and electrostatic techniques were used to study the nanoscale spatial evolution of native defects, crystallinity and work function in Ga2O3 across different morphological regions in laser induced periodic surface structures generated by an ultrafast laser. An emergent ~2.4 eV emission, likely related to oxygen interstitials or divacancy complexes, inversely correlates with the crystallinity of these regions. A contrast in work functions between the rims and troughs of the LIPSS, indicative of periodic differences in defect concentration, correlates with a reduction of crystallinity in the rim region relative to the trough region, suggesting an increased concentration of relatively shallow defects.

Laser MegaJoule (LMJ) is a high energy laser facility designed for fusion experiments. To track final optics damage, laser damage monitoring is carried out using images acquired by a camera. To prepare for the LMJ full energy/power operation, the damage models based on the phenomenological laws established in the laboratories are validated by experimental campaigns dedicated to performance. The very high quality of LMJ optics surfaces makes damage highly unlikely. In order to take the greater benefit of these performance campaigns, carried out on a reduced number of laser shots and components, a matrix of nearly 1000 damage sites is initiated offline on one optics. Precisely measured on a metrology bench before and after the campaign, this component was on LMJ facility during a performance campaign at the end of 2021. Very useful for the calibration of the LMJ monitoring camera, it also provided data to set LMJ laser damage models at higher energy level.

High energy laser facilities designed for fusion experiments, such as Laser MegaJoule or National Ignition Facility, are limited by laser-induced damage on their final optics. Accurate and early detection of damage growth is required for successful operation of such facilities. Since the image resolution is about the size of damage sites to monitor, diameter measurements are not sufficient to meet the objectives of damage growth quantification. An accurate size quantification of damage sites is based on light scattering measurements after time-consuming calibrations on the facility. An optical model is proposed to perform a simple and fast calibration of the measurements by numerical simulation. The model is based on light scattering measurements of several damage sites combined with optical simulations of the lighting system.

We investigate fluid jet polishing (FJP) for its potential to be used for freeform finishing of fused silica and potassium dihydrogen phosphate (KDP and DKDP) crystals without compromising laser damage performance. As part of this effort, a different slurry for each material was utilized. Samples with different amounts of material removed by FJP were prepared for damage testing. The results show that FJP can improve or maintain the laser damage resistance of these materials while simultaneously functioning as a deterministic, sub-aperture finishing method.

This presentation video was prepared for the Laser Damage 2022 conference.

We investigate the pulsed laser-induced damage performance and optoelectronic properties (at wavelength ~ 1 µm) of model nanophotonic thin films including gold, indium tin oxide, and alternative refractory materials such as titanium nitride and titanium oxynitride. We find that gold exhibits the best laser damage resistance compared to other plasmonic films of comparable thicknesses. We show that large absorption losses arising from high carrier concentrations and low mobilities in alternative plasmonic thin films, lead to exacerbated degradation and poorer laser damage performance. We will also present advanced strategies for engineering damage resistance and optical performance of nanophotonic thin films for high laser power applications. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-XXXXXX. LLNL-ABS-834545

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

The poster will report the Laser Induced Damage Threshold of an amplifier medium immersed in an active cooling system, and with different protocols, as 1on1 and Son1 procedures to evaluate the influence of the cooling system on the laser damage resistance. Some theoretical investigations will also be reported in order to explain the different experimental observations.

This conference presentation was prepared for the Laser Damage conference in 2022.

Anti-reflective (AR) coatings are frequently used for imaging and laser-related applications, however, their highest possible output power is limited by laser-induced damage threshold (LIDT). LIDT data for AR-coated nonlinear crystals is very limited, especially when it comes to pulse temporal scaling laws. Therefore, we investigated four identical lithium triobate (LBO) crystals deposited with the AR@1064+532 nm coating on one side and the AR@355 nm coating on the opposite side. Numerous tests were conducted following 1-on-1 and S-on-1 testing protocols at UV as well as IR wavelengths in the pulse duration range of 50 fs - 9 ns. To interpret experimental findings, we analyze empirical pulse temporal scaling laws of LIDT for distinct failure modes. Furthermore, we also considered numerical analysis based on rate equations.

Transverse stimulated raman scattering (TSRS) in potassium dihydrogen phosphate (KDP) and deuterated potassium dihydrogen phosphate (DKDP) plates for polarization control is a well-recognized limitation, giving rise to parasitic energy conversion and laser-induced damage. TSRS amplification is a coherent process that grows exponentially and distributed nonuniformly in the crystal and at the crystal surfaces. To understand the growth and spatial distribution of TSRS energy, a modeling approach was developed to simulate operational conditions in inertial confinement fusion-class laser systems. The result helps assess upper limits for operational conditions and guide possible ways to suppress the TSRS gain.

All-silica mirrors manufactured using GLancing Angle Deposition (GLAD) are a promising approach for optics with improved LIDT. However, water content may increase over time due to the porosity of the low index silica layers, potentially changing the LIDT. Additionally, consecutive irradiation during LIDT testing may remove stored water and influence the LIDT. Laser calorimetry, spectrophotometry and LIDT measurements, applying S-on-1 and R-on-1 methods, were used in order to determine the impact of laser-induced removal of stored water on the absorption, spectral behavior and laser damage resistance of all-silica mirrors. Influence of water reabsorption was investigated under different environmental atmospheric conditions.

We show that high repetition rate supercontinuum generation in solids is accompanied by the emission of conical third harmonic, whose occurrence serves as straightforward indication of the onset of in-bulk optical damage at its early stage. It is shown that conical third harmonic generation obeys noncollinear phase matching condition, which involves reciprocal lattice vector of a nanograting inscribed by femtosecond filament in the volume of transparent material. The universality of phenomenon is justified by the experiments in various transparent crystals and glasses and under various settings of focusing condition, pulse energy, repetition rate, exposure time and laser wavelength.

Understanding the physical process behind laser-induced damage of multilayer dielectric (MLD) interference coatings (IC) is of supreme importance for building ultrahigh-intensity laser systems. We experimentally studied the S-on-1 laser-induced damage threshold (LIDT) and damage characteristics of the SiO2/HfO2 high reflector quarter-wave stacks for three different femtosecond pulse durations operating at 1030nm wavelength. The S-on-1 LIDT for 1,10,100,1000 and 10000 pulses were recorded, and the values compare well with the state of the art. A strong correlation between single-shot damage morphology and laser focal intensity profiles was observed. Potential damage mechanisms of IC layers consistent with our observation will be discussed.

We present a method for producing durable thin optics for high-power lasers, using scalable process for spatially patterned glass engraved metasurface. The process is based on forming an etch-mask using laser raster-scan of a thin metal film on a glass, followed by dry-etching and removal of the metal mask. We present fabricated structures, and characterization of their optical performance, mechanical stability, and laser damage performance.

We will present our recent advances in identifying, understanding, and suppressing ns laser damage precursors in IBS produced dielectric films under UV, pulsed laser exposure. Model systems of single layer, layer pairs, and MLD coatings of silica, hafnia, scandia, and alumina were investigated. Through materials characterization, laser damage testing and simulations, we revealed that entrapped nanobubbles were important low fluence laser damage precursors. We further demonstrated that the identified precursors could be suppressed by either post low pressure thermal annealing or the manipulation of deposition process including using different sputtering gases to achieve ns UV-laser damage resistant dielectric coatings.

ELI stands for Extreme Light Infrastructure so it is expected to pose challenges to optical coatings by definition. Combination of high energies and high repetition rates requires very large apertures and high LIDT. Considerable number of ultrafast coating samples was tested over the years in our high vacuum LIDT platform. Similar effort was attributed to contamination control mainly for 1kHz ALLEGRA laser. LIDT studies concentrated on beam transport mirror for HAPLS Ti:Sapphire 10Hz/PW laser, mirrors for the ATON Nd:glass laser and advanced low line density MLD diffraction gratings for 10PW class operation at 1060nm. Concept of the ELIAS coating platform capable of handling up to 1.2m substrates will be presented as well.

The high-average-power petawatt-class Big Aperture Thulium (BAT) laser concept was proposed to meet the requirements for the next-generation compact particle accelerators. Our previous work reported the laser damage test and modeling of pulse compression gratings designed for the BAT laser and operating at 2 micron wavelength. Notably, we observed blister formation of the underlying layers at low fluences and ablation of the grating pillars at higher fluences. Here we present the measurement and analysis of these bulging damage precursors on the MLD gratings and mirrors using the cross-sectional transmission electron microscopy combined with focused ion beam processing.

More than 50 large aperture optics coated by Safran Reosc have been delivered to LULI for the APOLLON laser facility. Coating designs, processes and measurements are discussed with regard to the requirements. As a part of these optics is mounted on the beam line, we present operational performances with a specific focus on LIDT. This paper also relates the challenge to give a reliable LIDT value within a specific application toward the coatings of those component that have been tested by several LIDT-testing facilities. This test results are discussed and compared with LIDT test performed with the APOLLON laser beam.

In this work, we will review and evaluate the laser-induced optics damage observed on the final compressor gratings of the Advanced Radiographic Capability (ARC) laser. Damage initiation and growth rules are derived from online inspections and both measured and modeled laser performance are compared to a laser damage performance assessment of compressor grating witness samples performed offline. In addition, we will report the result of adapting these damage and growth rules to conditions relevant for the Scalable High-average-power Advanced Radiographic Capability (SHARC) 10 Hz Petawatt laser concept.

Laser-damage performance of optics is known to be negatively affected by microscale particle contamination induced by the operational environment. In this work, we discuss our approach to quantifying particulates found inside the grating compressor chamber in the OMEGA EP Laser System. Particulate was collected at specific locations near multilayer dielectric (MLD) gratings and MLD high reflectors and subsequently characterized using optical microscopy, scanning electron microscopy, and energy dispersive x ray spectroscopy. Initial results suggest that higher concentrations are observed near the beamline ports from the target chambers.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

A “cumulative” algorithm has recently been proposed as an alternative to the widely used International Organization for Standardization (ISO) standard approach to analyze laser-induced‒damage testing data. This algorithm may be particularly suitable for situations where the available sampling is limited. This work discusses the advantages and limitations of the cumulative algorithm using both simulated data and analytical models. Although the algorithm aims to increase statistical confidence for a given data set, it is demonstrated that the retrieved damage-probability distribution inaccurately represents the true distribution, even for a perfect measurement with infinite sampling. Modified versions of the cumulative algorithm are explored in attempt to increase accuracy.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.

This conference presentation was prepared for the Laser Damage conference in 2022.