Materials and Measurements
Damage to the bulk of transparent optical media can occur in amorphous, polymeric, polycrystalline or crystalline materials. Characterization and measurements of damage threshold including methods of test procedures, data reduction, systems considerations, and international standards are reported. Also, characterization of basic materials properties, such as absorption, thermal conductivity, stress-optic coefficients, moduli and defects is in the focus of this section. With the emergence of nanostructured materials, the relationship between the propagating laser flux and engineered nanostructures becomes another topic of interest.
Keynote Presentation: "Minimizing risk for laser damage due to transverse stimulated Raman scattering in large-aperture KDP/DKDP plates for polarization control at 3w," Tanya Kosc, Laboratory for Laser Energetics, Univ. of Rochester (United States)

Surfaces, Mirrors, and Contamination
Optical surfaces often limit the fluence of an optic due to intrinsic and extrinsic flaws and defects. Proper surface preparation, subsurface damage control, roughness and scattering reduction, environmental degradation and aging prevention, and contamination control can improve the performance of mirrors, diffraction gratings, substrates for multilayer coatings, and other surfaces.
Keynote Presentation: “The impact of surface particulates and laser-accelerated particles on continuous-wave laser damage," Joey Talghader, University of Minnesota (United States)

Thin Films
Because of the tremendous range of applications of optical multilayers for modifying the performance of optical measurements, and because thin films are generally the weakest part of optical systems, research into more damage-resistant thin films is a vibrant area. In addition to damage thresholds, researchers are interested in advanced film-deposition technology, contamination, film structure, film design, and film response to various environmental attacks and aging.
Keynote Presentation: “Limitation of dispersive optics for ultrafast physics," Volodymyr Pervak, Ludwig-Maximilians-Universität München (Germany)

Fundamental Mechanisms
Topics range from the basics of photon-matter interaction to nonlinear propagation. Emphasis is on nonlinear behavior; for example, multiphoton effects, nonlinear refractive index, and self-focusing. This area also includes modeling, such as thermal behavior of defect-initiated damage and the interplay between elements in an optical train that affect performance and hence damage.
Keynote Presentation: "Atomistic modeling of laser-induced surface modification and generation of nanoparticles: The effect of background gas and liquid environment," Leonid V. Zhigilei, University of Virginia (United States)

Mini-Symposium on Mid-Infrared Optical Materials and High-Power Lasers
Chaired by: Konstantin Vodopyanov, CREOL, The College of Optics & Photonics, Univ. of Central Florida (United States), and Vitaly Gruzdev, University of New Mexico (United States)

This Mini-Symposium is to overview the recent developments in the fields of high-power mid-infrared lasers, optical materials for those lasers, specific laser-damage issues, and some relevant applications. Tremendous progress in the area of mid-infrared lasers has resulted in availability of high-power short and ultrashort (femtosecond) pulses at wavelengths spanning from 2 to 10 micrometers. The specific wavelength range favors usage of semiconductor crystals, e. g., ZnSe, GaP, ZGP and GaSe as typical optical materials, for example, as nonlinear and lasing crystals. Laser-induced damage (LID) of those materials is currently a major limitation that blocks further progress of high-power mid-infrared lasers. This fact motivates engaging the laser-damage and mid-infrared-laser communities to join efforts on studies of the LID specific of those materials and wavelengths, and on fixing the major LID issues. As a part of this event, the following invited talk is planned:
Invited Presentation: “Kerr coefficient and multiphoton absorption of semiconductor crystals in mid-infrared," Konstantin Vodopyanov, CREOL, The College of Optics & Photonics, Univ. of Central Florida (United States)

Tutorial on Machine Learning in Design of Optical Components
Prepared and delivered by: Laura Kegelmeyer, Lawrence Livermore National Laboratory (United States)

Practical guide to machine learning for managing Laser Damage

Overview of machine learning methods and the practical steps needed for implementation. We will use examples from NIF to demonstrate steps from data preparation to the pros and cons of different machine learning methods.

Femtosecond 515-nm Mirror Thin Film Damage Competition
Coordinated by: Raluca Negres, Christopher J. Stolz, Lawrence Livermore National Lab. (United States)

A double-blind laser damage competition will be held to determine the current laser damage resistance of 515-nm, normal incidence multilayer mirrors in the femtosecond pulse regime. The results will be shared at SPIE Laser Damage 2021. The mirrors must meet the following requirements: This is a continuation of 2020 nanosecond laser, 532-nm damage competition. Any new sample submittals must be preapproved by Raluca Negres at (negres2@llnl.gov). Coatings received in 2020 will be angle-tuned for damage testing at 25 degrees to account for the large wavelength shift. The coatings shall be deposited on glass substrates provided by the coating supplier. The dimensions of the substrate shall be 50 mm (+/- 1 mm) in diameter and at least 10 mm thick.

Samples must be received by June 1, 2021 to the following address:

Raluca Negres, L-470 Lawrence Livermore National Laboratory 7000 East Avenue Livermore, CA 94550

Each sample will be assigned a unique label to maintain anonymity. The origin of the samples will not be released to the damage testing service and also will not be published at the Laser Damage Symposium or within the proceedings. A summary of the results will be published in the conference proceedings. Coating suppliers will be informed of the measured results and relative ranking within the submitted population. In order to minimize the number of damage tests, no more than two different samples can be submitted from each coating supplier.

In addition to the sample, the coating supplier MUST also supply the following information: Failure to provide the required information will result in disqualification of the sample. If two samples are submitted, the vendor must describe the manufacturing differences between the two samples. Optical or scanning electron microscopy may be used to image damage sites. Reflectance measurements may also occur. No other characterization tools will be used on the samples to protect any proprietary features of the samples.

See web for full details

Testing will be performed by:
;
In progress – view active session
Conference 11910

Laser-Induced Damage in Optical Materials 2021

On demand now
View Session ∨
  • Opening Remarks, Keynote Session I
  • Keynote Session II
  • Damage Competition Results and Mini-Symposium
  • Tutorial and Closing Remarks
  • 1: Fundamental Mechanisms I
  • Posters: Fundamental Mechanisms
  • 2: Materials and Measurements I
  • 3: Materials and Measurements II
  • 4: Materials and Measurements III
  • Posters: Materials and Measurements
  • 6: Thin Films I
  • 7: Thin Films II
  • 8: Thin Films III
  • Posters: Thin Films
  • 9: Surfaces, Mirrors, and Contamination
  • Posters: Surfaces, Mirrors, and Contamination
Session LIVE: Opening Remarks, Keynote Session I
Livestream: 12 October 2021 • 10:00 AM - 11:30 AM EDT
Join us for the opening Laser Damage 2021. Opening remarks from Conference Chairs, followed by keynote presentations on Fundamental Mechanisms + Materials and Measurements.
11910-800
12 October 2021 • 10:00 AM - 10:10 AM EDT
11910-1
Author(s): Leonid V. Zhigilei, Univ. of Virginia (United States)
On demand | Presented Live 12 October 2021
Show Abstract + Hide Abstract
The ability of short pulse laser ablation in liquids to produce clean colloidal nanoparticles and unusual surface morphology and microstructure has been employed in a range of practical applications. The results of large-scale molecular dynamics simulations help to uncover the key processes that control the structure of laser-modified surfaces and nanoparticle size distributions generated by pulsed laser ablation in liquids. The simulations are performed for one-component metals, bilayer thin films and alloy targets. The predictions of the simulations include the emergence of Rayleigh–Taylor hydrodynamic instability at the interface between ablation plume and liquid environment, as well as the limited elemental mixing in the colloidal nanoparticles generated by laser ablation of bilayer films.
11910-5
Author(s): Tanya Z. Kosc, Terrence J. Kessler, Hu Huang, Stavros G. Demos, Univ. of Rochester (United States)
On demand | Presented Live 12 October 2021
Show Abstract + Hide Abstract
The 3-D dependence of the spontaneous Raman scattering cross section for crystal configurations pertinent for the evaluation of the transverse stimulated Raman scattering (TSRS) in KDP and DKDP polarization control optics for large-aperture laser systems is investigated. TSRS can generate a transversely propagating parasitic beam capable of damaging both the optic and its mount. The results presented in this work can help optimize the design and manufacture of such optics where the TSRS gain is suppressed.
Session LIVE: Keynote Session II
Livestream: 13 October 2021 • 12:30 PM - 2:00 PM EDT
11910-25
Author(s): Vladimir Pervak, Ludwig-Maximilians-Univ. München (Germany)
On demand | Presented Live 13 October 2021
Show Abstract + Hide Abstract
Optical thin films multilayer coating has been driving the advancement of ultrashort laser technology towards ever shorter pulses and broader bandwidth. Deposition and sputtering of dozens of thin film layers with sub-nanometer accuracy. It permits controlling of the spectral phase and amplitude of optical radiation over an optical octave and beyond. We give overview on non-linear effects in multilayer ultrafast coating shortly before damage threshold appear as well as damages. We describe ways how to use or post-pone these effects and damages to higher fluences.
11910-39
Author(s): Joseph J. Talghader, Univ. of Minnesota, Twin Cities (United States)
On demand | Presented Live 13 October 2021
Show Abstract + Hide Abstract
Typical continuous-wave (CW) laser damage, which is based on average power, differs considerably from its ultra-short-pulse counterpart, which is based on maximum field. Despite this fundamental difference, it has recently been found that CW breakdown in the presence of surface particle contamination (i.e. dirt) has some of the dependences of ultra-short pulse breakdown, such as bandgap dependences, albeit based on very different physical mechanisms. Further studies have shown that particles in air are also a danger to surfaces in high average power applications, with laser breakdown potentially occurring at power levels well below that of both clean optics and optics with fixed surface particles.
Session LIVE: Damage Competition Results and Mini-Symposium
Livestream: 14 October 2021 • 10:00 AM - 12:30 PM EDT
11910-28
Author(s): Raluca A. Negres, Christopher J. Stolz, Lawrence Livermore National Lab. (United States); Gintare Batavičiute, Andrius Melninkaitis, LIDARIS Ltd. (Lithuania)
On demand | Presented Live 14 October 2021
Show Abstract + Hide Abstract
We propose to survey the state-of-the-art of VIS high reflectors. Specifically, mirrors must meet a minimum reflection of 99.5% at normal incidence for 515 nm. The participants select the coating materials, design, and deposition method. The samples will be damage tested using the raster scanning protocol with a 200-fs pulse length laser system operating at 5 kHz at a single testing facility to enable direct comparison among the participants. Details of the deposition processes, cleaning method, coating materials, and layer count will be shared.
11910-20
Author(s): Konstantin L. Vodopyanov, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Peter G. Schunemann, BAE Systems (United States); Taiki Kawamori, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
On demand | Presented Live 14 October 2021
Show Abstract + Hide Abstract
Using Z-scan and femtosecond 2.35-µm pulses, we study high-order nonlinear effects – multiphoton absorption (MPA) and nonlinear refraction (n2) in several notable mid-IR nonlinear monocrystals. We find that the multiphoton absorption orders N vary from N=4 (GaSe, ZGP) to N=6 (GaP, ZnSe) and correspond to the crystals’ bandgaps.
11910-21
Author(s): Bálint Kiss, Máté Kurucz, ELI-ALPS Research Institute (Hungary); Eric Cormier, ELI-ALPS Research Institute (Hungary), Laboratoire Photonique, Numérique et Nanosciences, CNRS-IOGS-Université Bordeaux (France), Institut Universitaire de France (IUF) (France)
On demand | Presented Live 14 October 2021
Show Abstract + Hide Abstract
A simple and cheap technique for post-compression of mid-IR laser pulses relies on nonlinear spectral broadening via SPM in mm-thick optical windows (plates) followed by recompression. Efficient broadening requires peak intensities of ~hundred GW/cm2, which in case of high average power (>10W) drivers puts serious requirements on the used optical materials’ thermal properties, purity, homogeneity, surface quality and LIDT of coatings. Several materials (YAG, fluorides, KBr, Si, ZnSe, ZnS) were tested with 3.2 µm, 13W (130 µJ, 100 kHz), 48 fs pumping. Measured nonlinear absorption, wavefront distortion, spectral broadening and long-term survival as a function of intensity will be shown.
11910-22
Author(s): Sergei Tomilov, Yicheng Wang, Clara J. Saraceno, Ruhr-Univ. Bochum (Germany)
On demand | Presented Live 14 October 2021
Show Abstract + Hide Abstract
Thin-disk lasers (TDLs) at 1 µm wavelength have made spectacular progress in the last decades both in high-power continuous-wave and ultrafast operation. Transferring the advantages of this geometry to longer wavelengths can significantly boost development of application-ready high-power ultrafast MIR laser systems. We report on our recent progress in this field, demonstrating several Ho:YAG-based laser oscillators, featuring 112 W of CW-operation output power and 40.5 W of mode-locked output with pulse duration in the ps-range.
11910-24
Author(s): Vitaly E. Gruzdev, Univ of New Mexico (United States)
On demand | Presented Live 14 October 2021
Show Abstract + Hide Abstract
Low photon energy of mid-infrared radiation supports generation of non-equilibrium free-carrier plasma in transparent optical materials via nonlinear absorption and associated inter-band electron excitation. The collision rate of the plasma may be low so that the free carriers experience from zero to very few collisions per electron per pulse for pulses shorter than 200 fs. Those features of the free-carrier plasma support specific mechanisms of light absorption. We consider solid-state analogs of the Brunel absorption at interfaces, Landau damping, and nonlinear absorption by free-carrier stimulated inverse bremsstrahlung. Parametric scaling of those mechanisms is compared against that of the traditional models.
Session LIVE: Tutorial and Closing Remarks
Livestream: 15 October 2021 • 10:00 AM - 11:45 AM EDT
Join us for the Live Tutorial on Machine Learning in Design of Optical Components delivered by: Laura Kegelmeyer, Lawrence Livermore National Laboratory (United States). Followed by closing remarks from the Conference Chairs.
11910-78
Author(s): Laura Mascio-Kegelmeyer, Lawrence Livermore National Lab. (United States)
On demand | Presented Live 15 October 2021
Show Abstract + Hide Abstract
Overview of machine learning methods and the practical steps needed for implementation. We will use examples from NIF to demonstrate steps from data preparation to the pros and cons of different machine learning methods.
11910-801
15 October 2021 • 11:30 AM - 11:45 AM EDT
Session 1: Fundamental Mechanisms I
11910-2
Author(s): Joseph R. Smith, Simin Zhang, The Ohio State Univ. (United States); Charles Varin, Cégep de l'Outaouais (Canada); Vitaly E. Gruzdev, The Univ. of New Mexico (United States); Enam A. Chowdhury, The Ohio State Univ. (United States)
On demand
Show Abstract + Hide Abstract
The development of next-generation laser optics can be guided by studies looking to improve the laser-induced damage threshold of highly-reflective interference coatings. We model intense few-cycle pulses interacting with multilayer HfO2/SiO2 dielectric interference coatings using fully three-dimensional particle-in-cell simulations to which we have added a Keldysh model for photoionization and a dielectric model to include refractive properties of the materials. We explore the reflection, transmission, and absorption of the laser pulses. We use the predicted excited electron density and energy density to estimate damage thresholds for these optics. This research was funded by DOE STTR grant no. DE-SC0019900.
11910-3
Author(s): Fedor V. Potemkin, MV Lomonosov Moscow State Univ (Russian Federation)
On demand
Show Abstract + Hide Abstract
We report on the clear difference in the behavior of laser-matter interaction of tightly focused high-intensity pulses with the bulk of solids when chirping and tuning the wavelength of the laser driver from near-IR to mid-IR. In transparent dielectrics, laser wavelength scaling leads to the change in the heating mechanism which, in turn, leads to a weak dependence of the plasma formation threshold on the pulse duration in mid-IR (4.6 μm) and a significant impact in the case of the near-IR (1.24 μm) excitation. In the case of semiconductors, the ionization mechanism remains within the framework of the multiphoton approximation, but an increase in the photon order for excitation by mid-IR pulses leads to a decrease in delocalization processes and losses in the prefocal region.
11910-4
Author(s): Marco Jupé, Laser Zentrum Hannover e.V. (Germany); Erikas Atkocaitis, Emilija Zutautaite, Vilnius Univ. (Lithuania); Kevin Kiedrowski, Morten Steinecke, Lars Herrero, Lars O. Jensen, Laser Zentrum Hannover e.V. (Germany); Urte Kimbaraite, Vilnius Univ. (Lithuania); Mindaugas Šciuka, LIDARIS Ltd. (Lithuania); Andrius Melninkaitis, Vilnius Univ. (Lithuania)
On demand
Show Abstract + Hide Abstract
The scaling of LIDTs for optical coatings has always been a topic of practical importance. Metallic coatings are no exception, thus experimental and theoretical investigation of the pulse duration dependency of the LIDT is studied in this work. Thereby, the most popular metallic layers were deposited on glass substrates and LIDT tested with the 1-on-1 and S-on-1 procedures with pulse durations between 200fs and several seconds, by combining different laser beam sources with comparable focusing conditions. These experimental results were used to extract empirical laws of LIDT scaling and are also compared with the preliminary theoretical considerations.
Session P4: Posters: Fundamental Mechanisms
11910-59
Author(s): Chloé Lacombe, Guillaume Hallo, Martin Sozet, Pauline Fourtillan, Jérôme Néauport, CEA-Cesta (France)
On demand
Show Abstract + Hide Abstract
The ``Laser MegaJoule'' (LMJ) is a high energy laser facility, located in France. It is developed to deliver about 1.4 MJ of ultraviolet laser energy in a few nanoseconds on targets set in its vacuum chamber, in order to achieve fusion ignition experiments. For current and intended LMJ laser specifications, LMJ large optical components are susceptible to laser-induced damage. Since damage sites on optics reduce optical quality of the laser beams, an excessively damaged component must be replaced. Monitoring laser damage growth on LMJ optics is essential both to control the quality of laser beams and to limit the operating costs using optics mitigation combined with beam blockers. An observation system has been developed to track laser damage sites without removing fused silica components. Images are automatically processed to detect damage sites and analyze their growth.
Session 2: Materials and Measurements I
11910-6
Author(s): Isaac L. Bass, Eyal Feigenbaum, Lawrence Livermore National Lab. (United States); Darin Anderson, LUMIBIRD (United States); Gabe Guss, Christopher W. Carr, Lawrence Livermore National Lab. (United States)
On demand
Show Abstract + Hide Abstract
Isaac Bass, Eyal Feigenbaum, Darin Anderson, Gabe Guss, Wren Carr High energy and power laser systems such as NIF operate near the damage threshold of its optical components. Stable operation requires control of the initiation and growth of the inevitable damage that will occur on its high-value optics due to factors such as beam contrast, non-linear effects, and contamination. This is accomplished through an optics recycling loop.[1] A key element in this loop is the Final Optics Damage Inspection (FODI) [2] system that monitors damage on the final optics preceding the target chamber. When the damage size reaches an upper limit, the optic is removed from the system and transported to the Optics Mitigation Facility (OMF). For fused silica optics, the damage is removed by a machining process using a CO2 laser.[3] This leaves a conical shaped depression in the surface of the optic. The core of the FODI system is an articulated telescopic imager at the center of the target chamber that can interrogate the final optics in any of the 192 beam lines entering the chamber. The detector in the imager is a two-dimensional charge coupled device (CCD) array. Individual optics in any beam line can be separately interrogated using an illuminator that injects light into the optic through one of its edges. This light then scatters or reflects from damage, defects, and cones to the FODI imager. The walls of the cones on the input surface of the optic, because of their orientations, are particularly efficient reflectors/scatterers of light. In many instances, the magnitude is sufficient to highly saturate the CCD pixels. This produces the well know blooming effect in CCDs when the charge exceeds the storage capacity of a pixel and spills into adjacent pixels. This result is a long line of saturated pixels when the charge is read out. The area of this line can be sufficiently large to obscure the growth of damage to sizes exceeding the upper allowable limit for removal of the optic. This can lead to either loss of the optic for recycling, or loss of the optic for any further use. The issue may become exacerbated by the prospect of increased use of even larger input cones to control the growth of exit surface damage by shadowing.[4] We will report on our study of light scattering by input surface cones and techniques to suppress the blooming effect it produces on the FODI imager. It includes high resolution imaging of the scattered light, its dependence on cone size and shape, modeling of the scattering process, and diversion of the scattered light by opposing exit surface cones. 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-??????. References: [1] Optics Recycle Loop Strategy for NIF Operations above UV Laser-Induced Damage Threshold, M. L. Spaeth, P. J. Wegner, T. I. Suratwala, M. C. Nostrand, J. D. Bude, A.D. Conder, J. A. Folta, J. E. Heebner, L. M. Kegelmeyer, B. J. MacGowan, D. C. Mason, M. J. Matthews & P. K. Whitman, Fusion Science and Technology Volume 69, 2016 - Issue 1 [2] Kegelmeyer LM, Clark RD, Leach RR, McGuigan DL, Miller Kamm V, Potter D, Salmon JT, Senecal JD, Conder AD, Nostrand M, Whitman PK. Automated optics inspection analysis for NIF. "Fusion Engineering and Design", Volume 87, Issue 12, December 2012, Pages 2120-2124 [3] I. L. Bass, G. M. Guss, M. J. Nostrand, and P. L. Wegner, “An improved method of mitigating laser-induced surface damage growth in fused Silica using a rastered, pulsed CO2 laser,” Proc. SPIE 7842, 7842202010. [4] R. N. Raman, R. Garcha, M. C. Rushford, G. Guss, and C.W. Carr, “A shadowing technique to arrest laser-induced damage growth on exit surface silica,” Proc SPIE 11173, 1117303 (2019)
11910-7
Author(s): Douglas W. Broege, Stavros G. Demos, Christophe Dorrer, Kyle R. P. Kafka, Amy Rigatti, Michael Spilatro, Univ. of Rochester (United States)
On demand
Show Abstract + Hide Abstract
Laser systems capable of delivering energetic nanosecond pulses with large incoherent bandwidth spanning more than 10 THz are currently under development for the study of laser–plasma instabilities. A consequence of such a spectrum is random intensity fluctuations, which may have a significant effect on laser damage thresholds. A special damage test station has been built for studying the effect this unique radiation has on common laser materials. We will share measurements of damage thresholds in coated optics, KDP, transmission gratings, and bare materials under various conditions aimed at understanding the role temporal fluctuations play in laser damage.
11910-8
Author(s): Eyal Feigenbaum, Isaac L. Bass, James L. Vickers, Gabe Guss, Christopher W. Carr, Lawrence Livermore National Lab. (United States)
On demand
Show Abstract + Hide Abstract
We present the development of large aperture fabricated input surface sites (~1-2 mm size) designed to “shadow” damage sites on the exit surface and arrest their further growth. The inherent expanding wave which leads to exit surface damage, motivates our diversion from a conic shape and development of more intricate geometries. We discuss the design considerations, the fabrication and resulting geometries, the optical modeling of light propagation through these geometries, the imaging of the shadowed region as well as the damage-inducing expanding wave intensification they lead to, and the large beam damage testing and their analysis.
Session 3: Materials and Measurements II
11910-9
Author(s): Jonathan Arenberg, Northrop Grumman Aerospace Systems (United States); Michael Thomas, Spica Technologies, Inc. (United States); Donna Howland, Northrop Grumman Aerospace Systems (United States); John Bellum, Coherent Technologies (United States)
On demand
Show Abstract + Hide Abstract
This papers reports on experiments designed and conducted to support the development of the proposed U.S. national laser damage standard. The key aspects of the proposed standard requiring experimental verification are test fluence profile, test scan design and test statistics. The paper will discuss the need and influence of each of these experiments on proposed standard. We will also discuss the experiment's designs and results. This paper will conclude with any revisions to the proposed standard informed by the experimental results.
11910-10
Author(s): Evelina Drobuzaite, Linas Smalakys, Erikas Atkocaitis, Andrius Melninkaitis, Vilnius Univ. (Lithuania)
On demand
Show Abstract + Hide Abstract
When discussing laser-induced damage phenomena, the main parameter of interest is the laser-induced damage threshold (LIDT). Since LIDT is a function of irradiation time (or number of pulses), its characterization is of critical importance when designing reliable industrial or medical laser systems or even planning long-term space missions involving high power lasers. Within laser-induced damage community, decrease of LIDT with increase in irradiation time (the so-called fatigue effect) is often estimated by using the S-on-1 test procedure described in the ISO 21254-2 standard. However, due to measurement limitations, S-on-1 tests are usually carried out for relatively small numbers of pulses, therefore additional extrapolation methods must be used in order to predict lifetime of optical components. The simple extrapolation procedure provided by the ISO 21254-2 standard no longer meets the demands of the community as it ignores existence of multiple failure modes and data censoring resulting from different damage detection techniques, therefore a new approach for LIDT extrapolation is much needed. In our previous work [1], we explored application of accelerated lifetime testing (ALT) techniques on S-on-1 test data. ALT approach treats S-on-1 experiments as sets of lifetime (or time to failure) distributions at different fluence levels instead of damage probability curves at different numbers of pulses. We have shown that this approach, combined with Bayesian inference and Markov chain Monte Carlo (MCMC) sampling, is well suited for extrapolation and uncertainty evaluation of S-on-1 experiments. However, proper application of these methods require empirical knowledge about lifetime distributions for different material types and irradiation parameters. Therefore, in this work an attempt is made to experimentally characterize lifetime distributions of highly reflective dielectric and metallic laser optics at both nanosecond and femtosecond pulse durations. UV and IR wavelengths as well as influence of irradiation fluence and polarization state are also considered. The results of this study provided insights into lifetime distributions of laser-induced damage and helped to shape guidelines for extrapolating S-on-1 experiments to longer irradiations. [1] L. Smalakys, A. Melninkaitis, Predicting lifetime of optical components with Bayesian inference, Opt. Express 29, 903-915 (2021).
11910-11
Author(s): Zhi M. Liao, Christopher Miller, David A. Cross, Christopher W. Carr, Lawrence Livermore National Lab. (United States)
On demand
Show Abstract + Hide Abstract
Recent development of using automatic microscopy to validate damage sites for damage mitigation at the National Ignition Facility (NIF) have accumulated a large set of damage data for growth analysis. In this work, we will examine how we can use the pre and post installation sizes to analyze the accumulated probability of growth of damage sites that have been exposed to multiple shots. The analysis can form the basis to derive single-shot probability growth behavior of fused silica damage site as a function of size, allowing a much higher fidelity on the behavior because of the size of the dataset. The results will allow us to compare the result to offline measurements as well as explore the potential differences across various NIF beamlines.
11910-13
Author(s): Kyle R. P. Kafka, Tanya Z. Kosc, Stavros G. Demos, Univ. of Rochester (United States)
On demand
Show Abstract + Hide Abstract
The design principles of a 20-fs, near-infrared laser-induced–damage testing system are presented. In addition to typical damage-initiation threshold tests such as S-on-1 and raster scan, this system is capable of studying other performance-relevant metrics, such as damage growth and functional thresholds. Experimental results for a hybrid mirror sample are presented as a demonstration.
Session 4: Materials and Measurements III
11910-14
Author(s): Karl-Friedrich Klein, Philipp Raithel, Stefan Heiden, Technische Hochschule Mittelhessen (Germany); Georg Hillrichs, Hochschule Merseburg (Germany)
On demand
Show Abstract + Hide Abstract
Over more than two decades, step-index fibers with undoped silica core and F-doped cladding have been improved for many broadband spectroscopic UV applications using broadband light sources. Although high-OH fibers are commonly used, broadband low-OH fibers with high UV-resistance are an alternative in the UV-region. The improvements have been supported by a solarization measurement-system using deuterium-lamp for damaging, which has been standardized by the German standardization group (DIN). Based on current studies with low-OH fibers using either a 213 nm pulsed laser or a pulsed Xe-lamp, the fitting procedure of multiple Gaussian shaped absorption bands of the UV-defects was strongly high-lighted and confirmed by comparing the temporally measured UV-induced losses between 200 and 400 nm. However, a band around 180 nm is been predicted to minimize the LSA-approximation belkow 225 nm. For this presentation additional studies have been conducted using a 266 nm pulsed laser. The focus is the comparison of the fiber damage by above-described pulsed Nd-YAG lasers; their emission wavelengths are close to peak wavelengths of well-known UV-defects in silica: E’ centers (210 … 214 nm) and NBOHC (260 nm). Looking more deeply into material modifications, different levels of hydrogen and OH-content are studied in these test fibers. In this presentation measurement results including short- and long-term damage, power-dependance and controlled annealing during and after the damaging phase will be shown. Finally, the results will be compared with studies using broadband cw Deuterium-lamp and pulsed Xenon-lamp for UV-defect generation.
11910-15
Author(s): Matthew S. Dabney, Edmund Optics Inc. (United States)
On demand
Show Abstract + Hide Abstract
Laser users desire optics that not only perform well, but also consistently over time. In fact, some aerospace and military applications can require long lifetime optics for remote environments where replacement is untenable. UV laser optics are susceptible to slow performance degradation with exposure to sub-Laser Induced Damage Threshold UV laser light due to the process of UV fatigue. Although UV fatigue of optics is well documented, the mechanisms are not well understood. Design and construction of a UV lifetime testbed to investigate the mechanisms of UV fatigue, preliminary results, and future directions will be presented.
11910-16
Author(s): Yingjie Chai, MJ Soileau, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
On demand
Show Abstract + Hide Abstract
Chemical vapor deposited (CVD) Zinc Selenide (ZnSe) window are often used in the high power laser system because of their extremely low (near-/far-)infrared absorption, and large transmission range (0.5um-22um). A good CVD process enables us to achieve the extreme purity needed for high-powered optics: 99.999% purity. Zinc vapor and H2Se gas react to form sheets of ZnSe on graphite susceptors. Different grain-sized polycrystalline ZnSe plates are precisely prepared and tooled to form optical windows or optical gain media. In recent years, in the area of few-cycle laser interaction with optic components, many new phenomena were found and investigated. Electron dynamic calculations were clearer and richer in this time domain[1-2]. Due to the potential applications in NIR few-cycle laser or attosecond laser generation, the single shot and multi-shot laser-induced damage threshold are tested in a multiplate supercontinuum-based few-cycle laser platform (12fs 1030nm centered) in CREOL according to ISO 21254. The damage threshold of different pulse numbers was carefully extracted. Laser-induced damage evolution along with the pulse number and grain boundary density are carefully characterized by SEM, AFM, and confocal Raman spectroscopy. Our experimental results will show the impact of grain boundary density on the laser-induced damage threshold of polycrystalline materials, which is of great value for future ultrashort laser pulse applications.
11910-17
Author(s): Frank Nürnberg, Bodo Kühn, Heraeus Quarzglas GmbH & Co. KG (Germany)
On demand
Show Abstract + Hide Abstract
The optical performance of fused silica can be negatively influenced by absorption, bubbles and material limits defined by the laser induced damage threshold (LIDT). Most of nowadays LIDT measurements focus on the durability of the coated surface instead of on the damage limits of the bulk material. Therefore, independent sets of LIDT measurements were carried out following a S-on-1 test procedure according to ISO 21254. Different fused silica grades have been tested at 355 nm with 5 ns pulses and at 1064 nm with 8 ns pulses to understand the influence of material properties for high energy laser applications.
11910-18
Author(s): Charles Bouyer, Romain Parreault, Nadja Roquin, CEA (France); Jean-Yves Natoli, Institut Fresnel (France); Laurent Lamaignère, CEA (France)
On demand
Show Abstract + Hide Abstract
The MELBA facility located at CEA CESTA aims at studying laser-induced damage of fused silica in the UV and nanosecond range on thin and thick silica plates. The impact of the temporal profile on laser-induced damage was studied with Gaussian, flat-in-time pulses and other shapes. Amplitude modulations with frequencies up to 30 GHz were also used to test LID on silica samples. We show that laser damage is sensitive to the temporal profile as well as the frequency of amplitude modulations. Experimental results are compared to 1D Lagrangian hydrodynamic simulations to assess the difference observed for LID as a function of power profile.
11910-19
Author(s): Kenneth L. Marshall, Kyle R. P. Kafka, Nathaniel D. Urban, Univ. of Rochester (United States); Jason U. Wallace, Univ. of Rochester (United States), D'Youville College (United States); Stavros G. Demos, Univ. of Rochester (United States)
On demand
Show Abstract + Hide Abstract
Interactions of liquid crystals (LC’s) with polarized light have been studied widely and have spawned numerous device applications across wide regions of the electromagnetic spectrum. To date, little is known about the effect of incident light polarization state on laser-induced damage thresholds (LIDT) for LC’s exposed to high-peak-power, nanosecond-pulsed lasers. This work describes the LIDT dependence on incident polarization for light encountering a LC mesophase in a high degree of molecular orientation. In one example chiral nematic LC, the 1053 nm, 1.4 ns LIDT ranged from 17.7-30.5 J/cm2 in the same device, depending on the input polarization handedness and ellipticity.
Session P3: Posters: Materials and Measurements
11910-63
Author(s): Michael Tripepi, The Ohio State Univ. (United States), Air Force Research Lab. (United States); Noah Talisa, Enam A. Chowdhury, The Ohio State Univ. (United States)
On demand
Show Abstract + Hide Abstract
We present an analysis of the electron dynamics in undoped (111) YAG when damaged with 9 fs, few cycle pulses at 760 nm central wavelength using time-resolved surface microscopy (TRSM). TRSM is a pump-probe technique that yields 2D shadowgrams of the exposed area, which are used to calculate the local, transient free carrier concentration. The dynamics presented will be for few-cycle pulses with a peak fluence of 8.3 J/cm^2 at delays up to 2 nanoseconds and time steps as small as 5 picoseconds. Atomic force microscope and TRSM images along with damage thresholds will be presented.
11910-60
Author(s): Loïc Ramousse, Institut de Physique de Nice (France), Fastlite (France); Gilles Chériaux, Cyrille Claudet, Aurélie Jullien, Institut de Physique de Nice (France)
On demand
Show Abstract + Hide Abstract
The laser-induced damage threshold (LIDT) of nematic liquid crystals is investigated in the femtosecond regime at 1030 nm. The thickness and breakdown of freely-suspended thin films (approximately 100 nm) of different mixtures (MLC2073, MLC2132 and E7) is monitored in real time by spectral-domain interferometry. The duration of laser pulses was varied from 180 fs to 1.8 ps for repetition rates ranging from single-shot to 1 MHz. The dependence of the LIDT with pulse duration suggests a damage mechanism dominated by ionization mechanisms at low repetition rate and by linear absorption at high repetition rate. In the single-shot regime, LIDTs exceeding 1 J/cm² are found for the three investigated mixtures.
11910-61
Author(s): Yuki Matsumoto, Naoki Nishioka, Atsushi Koizumi, Akito Uemura, Osaka Institute of Technology (Japan); Ryosuke Nakamura, Saitama Univ. (Japan); Masashi Yoshimura, Osaka Univ. (Japan); Hideo Horibe, Osaka City Univ. (Japan); Tomosumi Kamimura, Osaka Institute of Technology (Japan)
On demand
Show Abstract + Hide Abstract
For the semiconductor and liquid crystal display manufacturing process, resist removal by using laser irradiation has been investigated instead of conventional processes such as oxygen plasma and chemical method. An advanced laser resist stripping method for the positive-tone diazonaphthoquinone (DNQ) / novolak resist was successfully developed without causing the laser damage to the Si wafer. The pulsed laser irradiation in water can improve the resist stripping effect when compared with that of conventional atmosphere irradiation, however, the mechanism has yet to be clarified. In this study, we investigated the analysis of resist stripping phenomenon by using a high-speed laser imaging system. A pulsed laser at 640 nm (pulse duration: 40 ns) was used as an illumination laser and a CCD camera detected the reflectance image on the sample. Time resolution of this system depended on the pulse duration of illumination laser. Time-resolved images were acquired based on the “1-on-1” method. Time-resolved images were acquired from 40 ns to 10 us after the laser irradiation. At the laser irradiated spot, changes of the resist were observed after 40 ns from the laser irradiation. The resist was completely stripped from the Si wafer surface after 10 us. The duration of resist removal phenomenon in the water condition was longer than that in the normal atmosphere condition. A resist stripping mechanism could be elucidated by combining experimental high-speed laser imaging and a finite element (FE) analysis. The mechanism of the resist stripping in the water condition will be presented.
11910-62
Author(s): Atsushi Koizumi, Akito Uemura, Yuki Matsumoto, Tomosumi Kamimura, Osaka Institute of Technology (Japan); Nobu Kuzuu, Univ. of Fukui (Japan); Hideharu Horikoshi, Tosoh SGM Corp. (Japan)
On demand
Show Abstract + Hide Abstract
Degradation and resulting photo luminescence (PL) are sometimes induced by irradiation with UV lasers. The mechanisms of the degradation are dependent on the grades of silica glass and their production conditions. In this study, relationship between degradation phenomena and photo luminescence during the laser irradiation of pulsed 266 nm was evaluated with several glades of silica glass. Synthetic fused silica containing ca. 1000 ppm of OH (ES), silica glass produced from synthetic silica powder melted with oxy-hydrogen flame (S), and plasma torch (SD) were used for this measurement. Pulsed 266 nm laser with 80 kHz was irradiated at the inside of silica glass by using lens with a focal length of 50 mm. Degradation at the focused area was observed from the transmitted laser power. PL from the focused area was also detected with a spectrometer. SD needs nine times longer time for degradation than ES. PL around 640 nm related to the NBOHC (SiO) was gradually increased with degradation change, and rapidly increased when the laser damage occurred at the focused area. The mechanism of the degradation during the laser irradiation of pulsed 266 nm will be presented.
11910-64
Author(s): Laurent Lamaignère, Charles Bouyer, Matthieu Veinhard, Romain Parreault, CEA (France); Jean-Yves Natoli, Institut Fresnel (France)
On demand
Show Abstract + Hide Abstract
The poster aims to compare the results obtained with the same laser source with a large beam and with small beams. These latest were shaped from phase objects implemented to obtain several small beams from a single larger beam. The consistency of the results from both sets of measurements is shown. It validates the assumptions made and the specific mathematical treatments implemented to establish the link between the two approaches. It also validates and strengthens the approach developed from the rasterscan procedure used to measure damage densities from the scanning with beams of small dimensions. This shows that small beam tests are reasonably representative of tests carried out with large beams.
11910-67
Author(s): Selim Elhadj, Craig Garvin, Andy Bayramian, William Clauson, Matthew Murachver, Jeff Jarboe, Drew Kissinger, Cote LeBlanc, Seurat Technologies (United States); Nathaniel D. Urban, Jason U. Wallace, Stavros G. Demos, Kenneth L. Marshall, Univ. of Rochester (United States)
On demand
Show Abstract + Hide Abstract
Nematic liquid crystals (LC’s) are transparent rod-shaped molecules that can exhibit large dielectric anisotropy, high birefringence and excellent transparency, which make them well suited for use in many optical components in high power laser systems. Extrinsic factors such as alignment layer composition and LC purity can also play an important role in determining the LC optical response and durability. In this study, we investigate the efficacy of an absorption-based purification method and their impact on the laser damage behavior of nematic LC’s and their switching speed. We focus on the lifetime of the LC’s at kW’s average power, over cm2 areas, at near infrared wavelength and 20 Hz rep. rates.
11910-68
Author(s): Camille Petite, Institut Fresnel (France), CILAS (France); Antonin Moreau, Institut Fresnel (France); Hélène Krol, Catherine Grezes-Besset, CILAS (France); Julien Lumeau, Laurent Gallais, Institut Fresnel (France)
On demand
Show Abstract + Hide Abstract
The development of high power lasers implies specific needs of optics with very low absorption to avoid detrimental thermal effects up to damage of optical components, and associated metrology of these optics. In this work, we discuss on our recent developments of a thermographic-based technique to measure absorption: specifically, the Lock-In Thermography (LIT) technique applied in a multipass configuration to increase the effective power on the tested samples. We will present the system developed at the Institut Fresnel that is based on 1.5 kW Ytterbium fiber, that allows to submit samples to 5 kW effective power and measure absorption levels down to the ppm on optical coatings.
Session 6: Thin Films I
11910-26
Author(s): Marek Stehlik, Frank Wagner, Janis Zideluns, Julien Lumeau, Laurent Gallais, Institut Fresnel (France)
On demand
Show Abstract + Hide Abstract
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.
11910-27
Author(s): Marine Chorel, Florian Tournemenne, Eric Lavastre, Laurent Lamaignère, Saaxewer Diop, CEA-Cesta (France); Nicolas Bonod, Institut Fresnel (France)
On demand
Show Abstract + Hide Abstract
We report on the development of the robust optimization calculation for improving the LIDT of short-pulse MLD mirrors and gratings. This method has been validated experimentally with the manufacturing of multiple series of mirrors samples. In the case of a mirror used at 1053nm wavelength under vacuum in p-polarization and 45° angle of incidence the improvement reached 73%. The experimental validation of the method adapted to MLD gratings is an ongoing work.
Session 7: Thin Films II
11910-29
Author(s): Leif Kochanneck, Laser Zentrum Hannover e.V. (Germany); Henrik Ehlers, LASEROPTIK GmbH (Germany); Stepan F. Mikhailov, Maurice E. Pentico, Ying K. Wu, Victor G. Popov, Patrick Wallace, Jun Yan, Duke Univ. (United States), Triangle Universities Nuclear Lab. (United States); Lars O. Jensen, Laser Zentrum Hannover e.V. (Germany)
On demand
Show Abstract + Hide Abstract
Dielectric cavity mirrors for storage-ring free-electron lasers (FELs) in the VUV range have to overcome several challenges including resistance to synchrotron radiation and long-term stability in a contaminated vacuum. While oxide materials are not suitable below 190 nm, pure fluoride materials are not stable in this challenging environment. It has not been possible until now to generate lasing below 176 nm in a storage ring FEL. Duke University/TUNL and Laser Zentrum Hannover have successfully developed new strategies and produced mirrors with a high reflectivity of 95 %, which enabled FEL lasing between 168,6 and 176,7 nm.
11910-30
Author(s): Colin M. Harthcock, S. Roger Qiu, Paul B. Mirkarimi, Thomas Voisin, Christopher Colla, Harris Mason, Raluca A. Negres, Gabe Guss, Lawrence Livermore National Lab. (United States); Devika Vipin, Mengbing Huang, SUNY Polytechnic Institute (United States)
On demand
Show Abstract + Hide Abstract
We compare the 355 nm, 45º AOI p-pol 8 n-s laser damage performance of standing-wave hafnia single layers fabricated using argon and xenon as working gas. A suite of metrology tools has been employed to understand the structural, chemical and paramagnetic defect states in the two films. The resultant films from the xenon deposition process are highly dense and have high 3w laser damage performance.
11910-33
Author(s): Tsion Teklemarim, Matt Brophy, Pete Kupinski, Optimax Systems, Inc. (United States); Christopher J. Stolz, Lawrence Livermore National Lab. (United States); Michael Pierce, Rochester Institute of Technology (United States)
On demand
Show Abstract + Hide Abstract
Evaporated Al2O3 films are used in pulsed high energy laser applications from the deep-UV through near-infrared. Laser damage threshold and film stress must both be optimized to achieve the best laser mirror performance. In this study we investigate the affect oxygen partial pressure has on the properties of Al2O3 films deposited by electron beam evaporation. As oxygen partial pressure increases we observe a decrease in the refractive index and shift towards less tensile films at ambient. The decrease in tensile stress was observed to be correlated with water content in the films. Increasing oxygen partial pressure during deposition was also observed to improve film stoichiometry, absorption, and laser induced damage threshold (LIDT) at 351 nm.
11910-32
Author(s): Sina Malobabic, Niklas Höpfl, Sebastian Herr, Lars Mechold, Laser Components GmbH (Germany)
On demand
Show Abstract + Hide Abstract
Following customer demand, silicon oxynitride optical coatings were produced by ion beam sputtering (IBS). The multilayer sequence of the samples was designed such that the low refractive index was provided by SiO2, whereas for different designs a different composition of silicon oxynitride (n≈1.5–1.9) was used as high refractive material. This was realized by varying the ratio of the reactive gas components N2 and O2. LIDT measurements were carried out using a pulsed laser (9ns FWHM) @1064nm. Additionally, comparative measurements were carried out with frequency doubled pulses at 532nm. The performances of the designs were compared with their oxide-based QWOT-equivalents.
11910-31
Author(s): Christopher J. Stolz, Jian-gang Weng, Lawrence Livermore National Lab. (United States); Tsion Teklemarim, Matt Brophy, Pete Kupinski, Optimax Systems, Inc. (United States)
On demand
Show Abstract + Hide Abstract
One third of the final turning mirrors on the National Ignition Facility are laser damaged by 351 nm target backscattered light. The mirrors are spectrally complex hafnia and silica multilayer coatings with high 1 reflection for the forward propagating beam and high 3 transmission to suppress propagation of target backscatter. Alumina, a wider bandgap high index material, was selected to improve the 3 laser damage resistance despite a significantly lower refractive index resulting in increased layer count and reduced angular bandwidth. The impact on 3 laser damage fluence, coating stress, and spectral performance will be reported.
Session 8: Thin Films III
11910-35
Author(s): Xiangkun Lin, Yuan'an Zhao, Xiaofeng Liu, Dawei Li, Hao Ma, Yuchen Shao, Shanghai Institute of Optics and Fine Mechanics (China); Keqiang Qiu, Univ. of Science and Technology of China (China); Jian Sun, Meiping Zhu, Jianda Shao, Shanghai Institute of Optics and Fine Mechanics (China)
On demand
Show Abstract + Hide Abstract
Multilayer dielectric gratings(MLDGs)have been widely used in chirped pulse amplification due to their high laser induced damage thresholds(LIDTs). The quest for MLDG LIDT improvement is endless. For MLDGs applied in picosecond(ps) lasers, damage shows the characteristics of both thermal effect and nonlinear effect. The thermal damage of multilayer dielectric films (MLDFs) and MLDGs were investigated using a 1064 nm laser with a duration of 8 ns in our study. Differently from previous 1-on-1 studies, Raster Scan method is adopted to investigate the effect of low-density defects on the laser damage resistance of MLDFs with different top layers and MLDGs. The results show that the LIDTs of MLDGs are half of those MLDFs. For MLDFs with the top layer of HfO2, the damage behaves the ablation of the top layer material due to the surface strong electrical field. For MLDFs with top layer Ta2O5 and SiO2, the typical morphologies are nodule ejections. The initial damage of MLDGs fabricated by etching these three kinds of grating films are similar, and all behave nodule ejections. This indicates that reducing nodule defects can help the MLDGs LIDT improvement in ps pules. These results provide guidance for process optimizations of MLDG fabrication.
11910-36
Author(s): Matthias Lenzner, Lenzner Research, LLC (United States); Amir Khabbazi Oskouei, Luke A. Emmert, The Univ. of New Mexico (United States); Marco Jupé, Laser Zentrum Hannover e.V. (Germany); Thomas Willemsen, Laseroptik Garbsen GmbH (Germany); Morten Steinecke, Detlev Ristau, Laser Zentrum Hannover e.V. (Germany); Wolfgang Rudolph, The Univ. of New Mexico (United States)
On demand
Show Abstract + Hide Abstract
When designing femtosecond laser mirrors, one tries to minimize the peak intensity within the high-index layers to increase the laser-induced damage threshold. Typically, the optimization procedure utilizes the electric field distribution in the layer stack generated by monochromatic irradiation. This approach is sufficient for certain structures like high-reflectors based on quarter-wave films. More complex structures require to take into account the exact evolution of the pulse parameters such as peak intensity and duration within the multi-layer system. We exemplify this by discussing a merit function that can be included in femtosecond optics design.
11910-37
Author(s): Ryan McGuigan, Helmut Kessler, Manx Precision Optics Ltd. (United Kingdom)
On demand
Show Abstract + Hide Abstract
Laser Induced Damage is thought to be due to thin film coating defects. However, in some cases this model fails to predict observations such as the performance of e-beam coated optics over those coated with IBS and IAD methods. This motivated our research into a thermal model that considered gradual build of heat due to a pulse train passing through the optic. It is found that for a larger beam to optic diameter there is steady deviation from a square law. In addition, the dependence of LIDT on repetition rate and the resultant scaling is explored.
Session P2: Posters: Thin Films
11910-45
Author(s): Simin Zhang, The Ohio State Univ. (United States); Joseph Smith, Marietta College (United States); Emily Dalton, Aaron Davenport, Carmen S. Menoni, Colorado State Univ. (United States); Vitaly E. Gruzdev, The Univ. of New Mexico (United States); Enam A. Chowdhury, The Ohio State Univ. (United States)
On demand
Show Abstract + Hide Abstract
The pulse compression grating (PCG) is one of the most critical components of a high power chirped pulse amplification laser system to achieve the shortest pulse duration. Compared to metal gratings, a multi-layer dielectric (MLD) grating is a possible solution to improve the laser induced damage threshold (LIDT) of PCGs. Our previous work reported simulations of electron excitation dynamics in the interaction of MLD mirrors and femtosecond pulses (<100 fs). Here we present the study of the interaction of a MLD grating and a 50-fs pulse using a 2D dynamic simulation modeling both the E-field enhancement and transient material responses.
11910-46
Author(s): Ella S. Field, Damon E. Kletecka, Sandia National Labs. (United States)
On demand
11910-47
Author(s): Laurynas Lukoševičius, Justinas Butkus, Altechna Coatings, JSC (Lithuania); Peter Wessels, Stefanie Unland, Roland Kalms, Tammo Böntgen, Heinrich Mädebach, Silke Kramprich, Michael Hunnekuhl, Dietmar Kracht, Jörg Neumann, Laser Zentrum Hannover e.V. (Germany); Mirco Lorrai, Pier G. Lorrai, Mahmoud Hmidat, Filar Opto Materials S.r.l. (Italy)
On demand
Show Abstract + Hide Abstract
Modern laser systems have paved the way for spaceborne laser applications such as Earth's surface and atmosphere monitoring. Well known technologies like Nd:YAG lasers are often employed; however, they do not always comply with all the different requirements for space missions. High optical efficiencies and tunable wavelength, which are desirable for many applications, can be achieved with a simple laser design employing Alexandrite crystals. Horizon 2020 project presented here discuss the results on the development of alexandrite laser crystal treatment before coating deposition, and introduce recent research achievements on the alexandrite crystal interference coating deposition for LIDT improvement.
11910-49
Author(s): Ulrike Wegner, Joachim Meier, Dimitrios Rompotis, Radu-Costin Secareanu, Moritz Emons, Balazs Monoszlai, Maximilian Lederer, European XFEL GmbH (Germany)
On demand
Show Abstract + Hide Abstract
We are presenting our observations of degradation on optics exposed to the burst-mode pulse-train in the European X-ray Free Electron Laser (European XFEL) optical pump-probe laser system. Degradation is observed on all optics exposed to the 515nm 800fs burst-mode beam, with single pulse fluences being well below specified and tested laser damage thresholds. In all coatings suffering from this degradation SiO2 is the low index material. In one mirror design the SiO2 was replaced with Al2O3, thus preventing degradation. We believe that the degradation results from an interplay between the specific burst-mode operation and the SiO2 layer in the coating.
11910-51
Author(s): Erikas Atkocaitis, Linas Smalakys, Andrius Melninkaitis, Vilnius Univ. (Lithuania)
On demand
Show Abstract + Hide Abstract
The laser-induced damage threshold (LIDT) of anti-reflective (AR) coatings is a limitation when it comes to the maximum laser power. Furthermore, LIDT data for AR coatings on nonlinear crystals are rather scarce in scientific literature, mainly available for ns pulse durations. Lately, however, ps and fs pulse durations are also becoming important. Thus, in this work, four LBO crystals were IBS coated on both sides with two distinct coatings, namely, AR@1064 nm and AR@355 nm. These coatings were then LIDT tested for both UV and IR wavelengths with ns, ps, and fs pulses.
11910-53
Author(s): Ruobin Jia, Brittany N. Hoffman, Alexei A. Kozlov, Stavros G. Demos, Alexander A. Shestopalov, Univ. of Rochester (United States)
On demand
Show Abstract + Hide Abstract
Silica substrates coated with organic thin films were exposed to stainless steel and silica micro-particles to determine the effectiveness in preventing particle contamination and cleaning efficiency by air flows. Three specially designed monolayers coatings were developed and tested. Laser induced damage tests were conducted to confirm that the coatings do not affect the LIDT values. The results suggest that although the accumulation of particles is not significantly affected, the coated substrates exhibit significantly improved cleaning efficiency with air flow. A size distribution analysis was conducted to study the adsorption and cleaning efficiency of particles of different sizes.
Session 9: Surfaces, Mirrors, and Contamination
11910-40
Author(s): Russell Dent, Brittany N. Hoffman, Alexei A. Kozlov, Nan Liu, Amy L. Rigatti, Stavros G. Demos, Alexander A. Shesopalov, Univ. of Rochester (United States)
On demand
Show Abstract + Hide Abstract
We investigate contamination induced in grating-like structures during the etching process as a possible precursor to laser-induced damage. Our experimental model utilizes 5-mm line structures fabricated in E-beam–deposited coatings of silica using reactive ion etching (RIE) and reactive ion beam etching (RIBE). This makes it possible to compare the behavior in the pillars and trench regions. The results suggest that surface contaminants are primarily fluorinated polymers, while embedded contaminants consist primarily of carbon with very low detection of fluorine. Samples fabricated by the RIBE method exhibit significantly reduced roughness in the trenches, yet still present similar embedded contamination.
11910-41
Author(s): Niklas Praetzsch, Hermann Sturzebecher, Norbert Pirch, Fraunhofer-Institut für Lasertechnik ILT (Germany)
On demand
Show Abstract + Hide Abstract
In Laser Powder Bed Fusion (LPBF), there are high demands on the cleanliness of laser protective windows. However, process by products may deposit on the protective windows during processing and causing changes to the process boundary conditions. In this work, a methodology to assess the condition of LPBF protective windows using a line scan camera is presented. Image processing is used to detect the degree of contamination on the surfaces by means of thresholding. Moreover, the influence of contaminated protective windows on the LPBF process is investigated with beam caustic measurements, analysis of single tracks, and investigation of relative sample density.
Coffee Break 10:00 AM - 10:30 AM
11910-43
Author(s): Lukas Ramalis, Ugne Norkute, Lina Grineviciute, Rytis Buzelis, Tomas Tolenis, Ctr. for Physical Sciences and Technology (Lithuania)
On demand
Show Abstract + Hide Abstract
Optical components are the main parts in laser systems, which limits the total generated output power due to laser-induced damage. At nanosecond laser pulses materials experiences thermal expansion phenomena, therefore optical coatings gain stress leading to breakdown. Moreover, the main resistance to laser radiation is limited by material itself (band gap). Glancing angle deposition method is presented to produce porous nanostructured coatings, which are characterized by low inner stress. Optical resistivity dependance on porosity of several materials such as aluminium, niobium and silicium oxides singlelayers was evaluated. Furthermore, all-silica Bragg mirror is formed and optical properties investigated in different environments to achieve stable and superior optical resistance.
11910-44
Author(s): Yuhai Li, Harbin Institute of Technology (China), China Academy of Engineering Physics (China); Qingshun Bai, Rongqi Shen, Peng Zhang, Lihua Lu, Harbin Institute of Technology (China); Xiaodong Yuan, Xinxiang Miao, Wei Han, Hao Liu, Lin Huang, Caizhen Yao, China Academy of Engineering Physics (China)
On demand
Show Abstract + Hide Abstract
The problem of on-line removal of surface organic contaminants of large-aperture optical component in high energy laser systems has not been solved. In this work, an air low-pressure on-line plasma cleaning technique is proposed, which can remove organic contaminants and activate the surface of large-aperture optical component (430mm*430mm ). After air plasma cleaning, the transmittance and damage threshold are restored completely, and the damage of surface structure on optical components are not found. The interaction between air plasma species and organic contaminants was simulated by molecular dynamics to explain the mechanism of removing organic contaminants by air low-pressure plasma.
Session P1: Posters: Surfaces, Mirrors, and Contamination
11910-54
Author(s): Haruki Marui, Sora Aikawa, Yuji Umeda, Yusuke Funamoto, Tomosumi Kamimura, Osaka Institute of Technology (Japan); Yasunori Tanaka, Ryota Murai, Yoshinori Takahashi, Osaka Univ. (Japan); Tsuyoshi Sugita, Nikon Corp. (Japan); Masayuki Imanishi, Yusuke Mori, Masashi Yoshimura, Osaka Univ. (Japan)
On demand
Show Abstract + Hide Abstract
The developments of ultra-high purity material which resist the damage by DUV laser are strongly required. According to the general mechanism of laser-induced damage, some kinds of defects and contaminations on the optical material are very important factors for DUV laser-induced damage. The borate crystal SrB4O7 (SBO) was reported to be a nonlinear optical material with a wide transparency down to 130 nm. In this study, we grew a high-quality SBO single crystal and measured the surface DUV laser-induced damage threshold (LIDT) in several polished conditions. The SBO crystals grown over 13 days was 60 x 6 x 30 mm3 (a x b x c) without cracks or other defects. Two (020) plates were cut from the SBO crystal, and the both faces of the plates were optically polished. After that, we introduced catalyst-referred etching (CARE) to the one plate in order to atomically produce flat and damage-free SBO surfaces. As a result of the CARE treatment at a removal rate of 364 nm/h, the surface condition changed drastically, and a linear step-and-terrace structure was grew with a step height of 0.2 nm. The surface LIDT in several polished conditions were measured with a 1-on-1 method at 266 nm (5 ns pulse width). The polarization direction was parallel to the c-axis of the (020) sample. Synthetic silica was also evaluated for comparison. The surface LIDT (17.3 J/cm2) of SBO after optical polishing is 4.3 times that of synthetic silica (4.0 J/cm2). In addition, the surface LIDT (24.1 J/cm2) of CARE-treated SBO is 6.0 times that of synthetic silica. This suggests that CARE-treated SBO crystals are a promising material for optical components in high-power DUV laser systems.
11910-55
Author(s): Akito Uemura, Haruki Marui, Yuya Tsunezuka, Daichi Shima, Tomosumi Kamimura, Osaka Institute of Technology (Japan); Julian T. Long, Kristina D. Merino, Hitomi G. Yamaguchi, Univ. of Florida (United States)
On demand
Show Abstract + Hide Abstract
Effect of polishing contamination and surface defects for the LIDT has already been extensively studied in fused silica based transparent optics. The presence of contamination and damage layers on the surface of polished fused silica contributes to a large reduction in LIDT at ultraviolet wavelengths. The magnetic field-assisted finishing (MAF) technique has been shown to be successful in the fine finishing of optical components such as transparent Nd:YAG ceramics. Magnetic field-assisted finishing (MAF) with several tools has previously been applied to fused silica and was shown to improved surface LIDT at 266 nm. In this paper, the damaged surface of fused silica with enhanced damage resistance after MAF was analyzed to classify the MAF processed condition. Irradiated energy density and damaged volume calculated from depth geometry were measured with a white color interference microscope (Zygo: Zegage). Fused silica substrates polished with CeO2 compounds were prepared as workpieces, and the surface roughness was about 0.3 nm Sq after optical polishing. Material removal over 100 nm occurred with the MAF process, however the final surface roughness did not change. The LIDT at a laser wavelength of 266 nm of processed surfaces was about 1.4 times higher than for the as-polished surface. The damaged volume of as-polished surface was linearly increased as increase in the irradiated energy density. In contrast, MAF processed surface showed little change for the damaged volume. The damage morphology will be also discussed.
11910-56
Author(s): Marek Stehlik, Frank Wagner, Janis Zideluns, Julien Lumeau, Laurent Gallais, Institut Fresnel (France)
On demand
Show Abstract + Hide Abstract
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.
11910-57
Author(s): Thomas Gischkat, Daniel Schachtler, Zoltan Balogh-Michels, Roelene Botha, Rhysearch (Switzerland); André Mocker, Marco Cucinelli, Ostschweizer Fachhochschule (Switzerland); Bernd Eiermann, Sven Günther, Tamara Meinl, Igor Stevanovic, WZW-Optic AG (Switzerland); Marcus Denk, Philipp Alder, UCM AG (Switzerland); Michael Berger, Optics Balzers AG (Liechtenstein)
On demand
Show Abstract + Hide Abstract
The demand and requirements on optical components for laser applications are increasing continuously. Investigations of the defect morphologies after laser beam irradiation in the ns pulse regime indicate the presence of nano absorbers that negatively influence the components LIDT. In this report the laser induced damage testing and fitting method according to the precursor model was applied in order to determine the remaining particle densities for different ultrasonic cleaning procedures. High quality fused silica substrates were cleaned with different ultrasonic cleaning processes and subsequent coated with a SiO2 single layer. Laser irradiation was performed using a 1064 nm ns-pulsed laser.
11910-58
Author(s): Allison E. Browar, Eyal Feigenbaum, Isaac Bass, James Vickers, Gabe Guss, Wren Carr, Lawrence Livermore National Lab. (United States)
On demand
Show Abstract + Hide Abstract
We present surface process development for controlling densification, redeposition, and material removal to produce tailored shadower topographies. These topographies will be engineered to minimize the expanding wave intensification on the exit surface, being a potential source for further damage. We discuss the properties of thermal response to the effectiveness of laser material removal and develop a strategy for optimized shapes to support laser damage resiliency and fabricate high performance optics.
11910-69
Author(s): Dirk Raiser, Institut für Nanophotonik Göttingen e.V. (Germany); Ricardo Martins, European Space Agency (Netherlands), European Space Research and Technology Ctr. (Netherlands); Adrian P. Tighe, European Space Research and Technology Ctr. (Netherlands), European Space Agency (Netherlands)
On demand
Show Abstract + Hide Abstract
Molecular contamination due to outgassing of organic materials in vacuum as a source of significant degradation for space equipment is investigated in-situ and in real-time by a new experimental setup for controlled contamination and high-sensitivity spectroscopic analysis. The in operando build-up of contamination layers of a few nanometres and less on surfaces of typical space application materials in vacuum is detected by UV excited laser-induced fluorescence (LIF) and are accompanied by verification via a thermoelectric quartz crystal microbalance (TQCM) and a mass spectrometer, as well as ex-situ confirmation by Raman measurements.
Conference Chair
Lawrence Livermore National Lab. (United States)
Conference Chair
The Univ. of New Mexico (United States)
Conference Chair
Laser Zentrum Hannover e.V. (Germany)
Conference Chair
Colorado State Univ. (United States)
Conference Chair
CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
Program Committee
Northrop Grumman Aerospace Systems (United States)
Program Committee
The Ohio State Univ. (United States)
Program Committee
Lab. for Laser Energetics (United States)
Program Committee
Lawrence Livermore National Lab. (United States)
Program Committee
Sandia National Labs. (United States)
Program Committee
TRUMPF Laser Marking Systems AG (Germany)
Program Committee
Osaka Univ. (Japan)
Program Committee
CEA-Cesta (France)
Program Committee
Klaus Mann
Laser-Lab. Göttingen e.V. (Germany)
Program Committee
Vilnius Univ. (Lithuania)
Program Committee
Institut Fresnel (France)
Program Committee
Lawrence Livermore National Lab. (United States)
Program Committee
Lab. for Laser Energetics (United States)
Program Committee
Jonathan Phillips
STFC Rutherford Appleton Lab. (United Kingdom)
Program Committee
The Univ. of New Mexico (United States)
Program Committee
Lawrence Livermore National Lab. (United States)
Program Committee
Meiping Zhu
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (China)
Additional Information

POST DEADLINE ABSTRACT SUBMISSIONS


Post-Deadline Abstracts are being accepted for poster presentations



View Call for Papers PDF