Organic polymers are a versatile class of materials employed in a broad range of optical coating applications. However, their use as coatings in high-power laser applications, particularly in the UV spectral region, has been limited in scope due to their relatively low laser-induced damage thresholds (LIDTs), which decrease further with exposure to multiple pulses. This study explores the effect of post-deposition drying temperature and residual solvent on the LIDT of solvent-borne polymer coatings. In this work, poly(ethyl methacrylate) (PEMA) coatings were deposited by first spin coating solutions of PEMA (dissolved in 2,2,2-trichloroethanol (TCE)) onto fused silica substrates, then baking at temperatures of either 130 degrees C (soft-bake) or 180 degrees C (hard-bake). Analysis of the two coatings revealed that the soft-bake coating retained a significant amount of TCE within the polymer matrix, which functioned to plasticize the coating and reduce internal stress. The laser-induced damage resistance of the two coatings was evaluated using 351-nm, 1-ns laser pulses. The testing protocols included single-pulse (1-on-1), 1-pulse ramp (R-on-1), and a 1000-pulse ramp (1000R-on-1) test. The results showed that the plasticized, soft-bake coating exhibits a significantly increased LIDT, especially for multipulse irradiation conditions.

The laser-damage performance of HfO2/SiO2 and Al2O3/SiO2 mirrors was investigated at a laser wavelength of 351 nm with nanosecond pulse durations. A method was developed to quantify the laser-induced damage-growth threshold under conditions relevant to high-repetition-rate, large-aperture laser systems. The results suggest that the damage-growth performance cannot be inferred from the corresponding damage-initiation threshold that is commonly used to evaluate the performance of optical materials. A systematic difference was also observed in the performance between these two groups of high-index materials, with the Al2O3/SiO2 mirrors exhibiting about twofold improvement in the damage-growth threshold.

This publisher's note contains a correction to Opt. Lett.50, 4838 (2025)10.1364/OL.559478.

The laser-induced damage threshold of a grating waveguide output coupler (GWOC) exposed to laser radiation at a wavelength of 1030 nm and with a pulse duration of 500 fs was investigated. The GWOC is a combination of a sub-wavelength circular grating and a partial reflector based on a Nb2O5 and SiO2 multilayer sequence. It was designed to be used as an output coupler of a thin-disk laser cavity for the generation of beams with radial polarization. The results revealed a laser-induced damage threshold (LIDT) fluence of 0.36 J/cm² for single-pulse tests and 0.26 J/cm² for multiple-pulse conditions with up to 1000 shots. These threshold values are comparable to those of an unstructured output coupler with Nb2O5 and SiO2 coating layers, highlighting the minor influence of the grating on the LIDT.

This year’s competition proposed to survey the state-of-the-art broadband, near-IR multilayer dielectric (MLD) mirrors designed for ultra-short, pulsed laser applications. The requirements for the coatings were a minimum reflection of 99.5% at 45-degree incidence angle for S-polarization from 830 nm to 1010 nm and group delay dispersion (GDD) < ± 50 fs2. The participants in this effort selected the coating materials, coating design, and deposition method. Samples were damage tested at a single testing facility to enable direct comparison among the participants using a 25 ± 5 fs OPCPA laser system operating at 5 Hz. A double blind test assured sample and submitter anonymity. The damage performance results, sample rankings, details of the deposition processes, coating materials and substrate cleaning methods are shared here. We found that multilayer coatings using tantala and/or hafnia as high index materials were top performers within several coating deposition groups. Specifically, dense coatings by ion-beam sputtering (IBS), magnetron sputtering (MS), and electron-beam ion assisted deposition (e-beam IAD) exhibited highest damage initiation onset (LIDT) while e-beam coatings were low performers. In addition, damage growth onset (LDGT) was also examined and the results are reported here for all samples as this performance metric plays an important role in establishing the safe operational conditions for larger aperture, ultrashort pulsed lasers. Lastly, not all coating samples in the survey met the GDD requirements stated above and associated measurements are discussed in the context of the present and past competitions focused on similar broadband, near-IR MLD coatings.

We demonstrate efficient anti reflection coatings based on adiabatic index matching obtained via nano-imprint lithography. They exhibit high total transmission, achromaticity (99.5% < T < 99.8% from 390 to 900 nm and 99% < T < 99.5% from 800 to 1600 nm) and wide angular acceptance (T > 99% up to 50 degrees). Our devices show high laser-induced damage thresholds in the sub-picosecond (>5 J/cm2 at 1030 nm, 500 fs), nanosecond (>150 J/cm2 at 1064 nm, 12 ns and >100 J/cm2 at 532 nm, 12 ns) regimes, and low absorption in the CW regime (<1.3 ppm at 1080 nm), close to those of the fused silica substrate.

High-repetition rate diode-pumped sub-ps lasers are widely used in the industrial sector for high-quality material processing applications. However, for their reliable operation, it is crucial to study the power handling capabilities of the optical components used in these systems. The optical components, such as mirrors, gratings, dichroic filters, and gain media, are designed based on dielectric thin films. When subjected to high-intensity laser radiation, the phenomenon of laser-induced contamination (LIC) can lead to the growth of a nanometric, highly absorbent layer on an irradiated optical surface, which can result in transmission or reflection loss and eventual permanent damage. In this study, we investigate LIC growth on dielectric oxide thin films in an air environment irradiated by MHz sub-ps laser at 515 nm. We examine the effect of thin film deposition method, material, and thickness on LIC growth dynamics. The irradiated spots on the surface are inspected using multiple observation methods, including white light interference microscopy and fluorescence imaging. Our results show that the LIC growth dynamics depend on the laser intensity and irradiation time and can be affected by the thin film deposition method, material, and thickness. These findings could be used to inform the development of more resistant optical components, ensuring long-term reliable laser operation required for industrial applications. The study highlights the need for validating optical components using tests that closely mimic real-world applications and provides insight into the complex processes that lead to LIC.

Laser-induced contamination (LIC) degrades the performance of optical components and can result in optical losses or even laser-induced damage. LIC deposit formation limits reliable operation of high repetition rate industrial lasers. In this work, we investigate LIC growth on dielectric oxide thin films in air environment irradiated by MHz sub-ps laser at 515 nm. We study the LIC growth dynamic in dependence on thin film deposition method, thin film material and thin film thickness.

Since the early years of laser research, laser damage resistance of optical components has been extensively studied. The research dealing with laser-induced damage threshold (LIDT) remains still very active thanks to the complexity of the involved physical mechanisms and numerous breakthroughs in the field of lasers and their applications. The laser damage studies are important for proper handling of optical components in laser systems and for the research on damage initiation, material processing comprising ablation and laser machining. The emerging scientific fields and industrial applications require optical elements that tune the polarization, wavelength, or pulse duration of emitted ultrashort pulses. Key elements that can control the light properties are diffraction gratings. For high power use, a design based on the combination of a planar waveguide and sub-wavelength grating, called grating waveguide structures (GWS), is very promising. [1] Within the MSCA GREAT project [2] , an established network of scientific institutions designs, fabricates, characterizes and implements the GWS into laser systems. Our role is to develop and implement robust laser damage metrology to investigate the power handling capabilities of GWS. An essential part of the characterization of such complex structures is the laser damage study of particular materials used in high reflective (HR) mirrors, see Fig. 1a ). In this work, high-index dielectric coatings of HfO 2 , Nb 2 O 5 and Y 2 O 3 were tested by near-infrared sub-ps pulses, see Fig. 1b ).

Crystalline sesquioxide films (Sc2O3, Y2O3, Lu2O3) produced by pulsed-laser deposition were examined for laser damage resistance with pulses of 500 fs duration, at a wavelength of 1030 nm and at a 10 Hz repetition rate. Comparable tests were performed with amorphous magnetron-sputtered thin films (SiO2, HfO2, Nb2O5). We found the laser-induced damage thresholds of the sesquioxides are close to those of HfO2 in the multi-pulse test regime. The results are the basis for designs of damage resistant re ective components used in ultrashort-pulse lasers.

Dielectric sesquioxide films (Sc2O3, Y2O3, and Lu2O3) were fabricated by pulsed-laser deposition and tested in terms of their laser damage properties for pulses of 500 fs duration, at a wavelength of 1030 nm and at a 10 Hz repetition rate. Comparable tests were performed with magnetron-sputtered thin films of established optical-coating materials (SiO2, HfO2, and Nb2O5), whose results served as a benchmark. The laser-induced damage thresholds of the sesquioxides are comparable to each other, and in the multi-pulse test regime show values close to ones of HfO2 coatings. A lower damage threshold was observed for the polycrystalline Lu2O3 film grown on sapphire compared to single-crystal Lu2O3 grown on yttrium aluminium garnet (Y3Al5O12), attributed to the highly textured morphology and potential for a greater density of defect states in these films. We conclude that pulsed-laser deposition is a potential fabrication method of sesquioxides for use in high-power resistant optical components for ultrashort-pulse lasers.

Etude de la tenue au flux laser de matériaux et structures couches minces pour la réalisation d’optiques diffractives de type GWS (Grating Waveguide Structure) L’endommagement laser et la contamination induite par laser sont des phénomènes qui limitent les performances des composants optiques à base de couches minces optiques dans les lasers haute puissance à impulsions ultracourtes. Afin d'améliorer la résistance au flux laser des couches optiques destinées à être utilisées dans des composants diffractifs (GWS), des tests de différents matériaux diélectriques, le développement d’empilements optimisés et l’étude de l’effet de la technique de dépôt ont été réalisés.De tels développements reposent sur une métrologie robuste de l'endommagement laser. Malgré les processus physiques d'excitation des matériaux diélectriques dans le régime sub-ps, indiquant que le seuil d’endommagement laser (LIDT) ne devrait pas dépendre de la taille du faisceau, nous avons constaté que cette affirmation n'est pas sans équivoque dans la littérature publiée sur le sujet. Notre travail de métrologie avec une source laser de 500 fs 1030-nm souligne la difficulté de la mesure du LIDT par des faisceaux laser très focalisés et nous suggérons la déformation du faisceau due à l'auto-focalisation dans la lentille comme une explication possible. Nous avons également identifié les paramètres de test permettant d'obtenir des résultats LIDT stables et reproductibles.Nous avons effectué une étude de la tenue au flux laser de sesquioxydes cristallins déposés par laser pulsé (Sc2O3, Y2O3, Lu2O3) et des oxydes métalliques amorphes (HfO2, Nb2O5, SiO2) déposés par pulvérisation magnétron. Nous avons mesuré les LIDT intrinsèques de chaque matériau et leur évolution avec le nombre d'impulsions pour différents paramètres laser pertinents pour le fonctionnement des GWS.Après cette sélection et cette étude des matériaux en couches minces, nous avons étudié les effets des techniques de fabrication et le design des GWS sur le LIDT. Puisque la fabrication de composants optiques diffractifs nécessite des étapes de fabrication multiples et complexes, nous avons étudié l’effet de certaines de ces étapes, utilisation de promoteur d’adhésion et couches de masquage, sur la tenue au flux laser. Nous avons observé que les LIDT des surfaces traitées sont proches des LIDT des surfaces non traitées, dans nos conditions de test.Sur la base d’une source laser 700-fs 515-nm 3.3-MHz, nous avons étudié la dynamique de croissance de la contamination induite par laser (LIC) en fonction du matériau, de la technique de dépôt et de l’épaisseur des couches. Nous avons trouvé une relation quasi linéaire entre les épaisseurs de dépôt de LIC et les épaisseurs de couche de SiO2 et HfO2. De plus, la technique de dépôt et donc les propriétés du matériau ont un effet déterminant sur la croissance du dépôt de LIC.

Laser-induced contamination (LIC) can lead to optical losses or laser-induced damage on optical components and limits the reliable operation of high repetition rate industrial lasers. In our work, we used MHz sub-ps laser source at 515 nm to test dielectric oxide materials in air environment in terms of LIC formation. We found significant difference in the LIC deposit rate in dependence on coating material and deposition technique. The results could be used for new designs of optical components that will be more resistant to LIC formation.

Laser-induced damage experiments on H f O 2 and N b 2 O 5 thin films were performed with 500 fs pulse duration at 1030 nm wavelength. Threshold fluences as a function of beam size have been determined for effective beam diameters ranging from 40 to 220 µm, in a single shot regime. The results suggest no beam-size effect related to material properties in the investigated range, but size effects related to the metrology. The results indicate the importance of appropriate focusing conditions and beam measurement to qualify the optics for use in lasers with large beam sizes.

Laser-induced damage experiments on HfO2 and Nb2O5 were performed with 500 fs pulse duration at 1030 nm wavelength. Threshold fluences in dependence of beam size have been determined within the range of effective beam diameters from 40 µm up to 220 µm. The results suggest no dependence of beam size effect on effective beam diameters at least between 80 µm to 160 µm. The LIDT results indicate importance of appropriate focusing conditions and beam measurement to qualify the optics for use in lasers with large beam sizes.