Laser-induced Damage In Optical Materials Research Articles

Fundamental mechanisms of laser-induced damage in optical materials: today’s state of understanding and problems

Theoretical models of laser-induced damage mechanisms in optical materials are reviewed: inclusion-initiated thermal explosion (extrinsic mechanism) and impact ionization (II) and photoionization (intrinsic mechanisms). Different approaches to II theory based on quantum kinetic equation, Boltzman equations, and rate equations are briefly described. A relative contribution of II and photoionization predicted by these models at different laser pulse durations, including femtosecond-range, are discussed and compared with available experimental data. Basing on an analysis of published theoretical and experimental results, a today’s state of understanding fundamental laser damage mechanisms is concluded.

Effect of thermal anneal on growth behavior of laser-induced damage sites on the exit surface of fused silica

Thermal anneal is known to arrest the growth of laser-induced damage in optical materials. However, the response of the material which leads to this observed behavior is poorly understood. In this work, we investigate the effect of isothermal anneal at 1100°C for 12 hours on the growth rate of laser-induced damage sites in fused silica. Growth rate was significantly lower for annealed initiated damage sites than that for untreated sites. This decrease in growth rate was associated with the closure of small surface and subsurface cracks, suggesting that aggressive growth rate is due, at least in part, to subsurface fracture complexity.

Investigation of laser-induced damage by nanoabsorbers at the surface of fused silica

A model for describing laser-induced damage in optical materials by nanosecond laser pulses is investigated. The laser-damage critical fluence is obtained based on calculating the light absorption of nanoabsorbers by using Mie theory and solving the heat equation. Considering a power law distribution of nano-absorbers, we calculated the damage probability at the surface of fused silica including Pt particles. The theoretical results calculated with appropriate parameters are applied to fit the experimental data in order to identify the properties of nanodefects.

Investigations of laser-induced damages in fused silica optics using x-ray laser interferometric microscopy

A novel x-ray laser (XRL) application, aimed at understanding the microscopic effects involved in formation of laser-induced damage in optical materials exposed to high-power sub-ns laser pulses, is presented. Standard fused silica substrates with permanent damage threshold below 20 J/cm2, when irradiated by 438 nm laser pulses, were probed in situ by a neonlike zinc XRL at 21.2 nm. The probing beamline employed a double Lloyd’s mirror x-ray interferometer, used in conjunction with an imaging mirror to achieve magnification of ∼8. In conjunction with an array of in situ optical diagnostics, the main question addressed is whether the damage on the rear surface of the beamsplitter is transient or permanent. The second issue, examined by both the x-ray interferometric microscopy and the optical diagnostics, is whether a local rear-surface modification is associated with nonlinear effects such as self-focusing or filamentation of the damaging laser beam in the bulk.

Phase explosion induced by high-repetition rate pulsed laser

The characteristics and mechanisms of the damage to absorbing glass with high-repetition laser pulses (several kHz) are discussed. The results show that: (1) in the range of comparatively low-repetition rate, the damage is characterized by material melting and a small crater on the surface of substrate; (2) with the increase in repetition rate, a bigger and deeper crater is surrounded by re-deposition and crystalline granules originating from the cooling of vapor; and (3) the crater, surrounded by evaporation and an large number of solid particulates which is obviously the characters of phase explosion, becomes even bigger and deeper when the repetition rate is further increased. We modeled the temperature distribution in different repetition rate regime and found that heat accumulation plays a significant role in damage process. Because of the temperature dependence of damage mechanism, the temperature of the area irradiated by laser beam will ramp up with increasing the repetition rate, which triggers the melting and evaporation of dielectrics and phase explosion successively. Our results may benefit the understanding of laser-induced damage in optical materials.

Techniques for qualitative and quantitative measurement of aspects of laser-induced damage important for laser beam propagation

Characterizing laser-induced damage in optical materials is important for laser design and operation. Previous methods of evaluating optical materials damage resistance to high-power laser irradiation have typically suffered from shot-to-shot uncertainties in laser energy output and/or have insufficient sensitivity. More importantly, such methods do not address the aspects of laser-induced damage important to laser beam propagation, namely the amount of light scattered by the damage. We present a method for the quantitative correlation of material modification on the surface or in the bulk of optical materials to laser parameters, which deconvolutes the effects of laser output instability. In image analysis, two images, one a fluence spatial profile and the other a visible light scatter image of the damage, are directly compared to extract scatter as a function of fluence. An automated microscope is used to record the location and number of bulk damage sites and determine a calibration factor between the scatter signal observed and damage density. We illustrate the method with a determination of both bulk damage density as a function of laser fluence and of a representative size distribution in a DKDP crystal. Our method is capable of determining damage densities with an absolute uncertainty of ±0.3 pinpoint damage sites per cubic millimetre (pp mm−3) in the range 1–100 pp mm−3 with our minimum detectable density being 0.01 pp mm−3. We also determined the pps produced by laser pulses of 351 nm, 3 ns light to have a mean diameter of 5.5 ± 2.5 µm (1/e2).

Localized dynamics during laser-induced damage in optical materials.

Laser-induced damage in wide band-gap optical materials is the result of material modifications arising from extreme conditions occurring during this process. The material absorbs energy from the laser pulse and produces an ionized region that gives rise to broadband emission. By performing a time-resolved investigation of this emission, we demonstrate both that it is blackbody in nature and that it provides the first direct measurement of the localized temperature of the material during and following laser damage initiation for various optical materials. For excitation using nanosecond laser pulses, the plasma, when confined in the bulk, is in thermal equilibrium with the lattice. These results allow for a detailed characterization of temperature, pressure, and electron densities occurring during laser-induced damage.

Laser-induced damage in optical materials: sixteenth ASTM symposium

The Sixteenth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, CO, 15-17 Oct. 1984. The Symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific Research. Approximately 180 scientists attended the Symposium, including representatives from England, France, The Netherlands, Scotland, and West Germany. The Symposium was divided into sessions concerning Materials and Measurements, Mirrors and Surfaces, Thin Films, and Fundamental Mechanisms. As in previous years, the emphasis of the papers presented at the Symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high-power apparatus. The wavelength range of prime interest was from 10.6,microm to the UV region. Highlights included surface characterization, thin-film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. Harold E. Bennett of the U.S. Naval Weapons Center, Arthur H. Guenther of the U.S. Air Force Weapons Laboratory, David Milam of the Lawrence Livermore National Laboratory, and Brian E. Newnam of the Los Alamos National Laboratory were cochairmen of the Symposium.

Laser-induced damage in optical materials: fifteenth ASTM symposium

The Fifteenth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, CO, 14–16 Nov. 1983. The Symposium was held under the auspices of the ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific Research. Approximately 200 scientists were in attendance, including representatives of the U.K., France, Israel, and West Germany. The Symposium was divided into sessions concerning Materials and Measurements, Mirrors and Surfaces, Thin Films, and finally Fundamental Mechanisms. As in previous years, the emphasis of the contributed papers was directed toward new frontiers and new developments. Particular emphasis was given to materials for high-power apparatus. The wavelength range of prime interest extended from 10.6 μm to the UV region. Highlights included surface characterization, thin-film–substrate boundaries, and advances in fundamental laser–matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Arthur H. Guenther of the Air Force Weapons Laboratory, David Milam of the Lawrence Livermore National Laboratory, and Brian E. Newnam of the Los Alamos National Laboratory were cochairmen of this Symposium.

Laser-induced damage: an introduction

Knowledge of laser-induced damage in optical materials cannot advance until definitions, testing procedures, and analytical methods are standardized. Eight laboratories in Europe and the U.S.A. participated in laser-induced damage testing; the papers in the 1 Nov. 1984 issue of Applied Optics discuss their findings.

Laser-induced damage in optical materials: fourteenth ASTM symposium

The Fourteenth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colo., 16–17 Nov. 1982. The Symposium was held under the auspices of the ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific Research. Approximately 200 scientists attended the Symposium, including representatives of the U.K., France, Japan, West Germany, and the U.S.S.R. The Symposium was divided into sessions concerning Materials and Measurements, Mirrors and Surfaces, Thin Films, and finally Fundamental Mechanisms. As in previous years, the emphasis of the papers presented at the Symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high-power apparatus. The wavelength range of prime interest was from 10.6 μm to the UV region. Highlights included surface characterization, thin-film–substrate boundaries, and advances in fundamental laser–matter threshold interactions and damage mechanisms. Harold E. Bennett of the Naval Weapons Center, Arthur H. Guenther of the Air Force Weapons Laboratory, David Milam of the Lawrence Livermore National Laboratory, and Brian E. Newnam of the Los Alamos National Laboratory were cochairmen of the Symposium.

Laser-induced damage in optical materials: thirteenth ASTM symposium

The Thirteenth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards (NBS) in Boulder, Colo., 17–18 Nov. 1981. The Symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific Research. Approximately 200 scientists attended the Symposium, including representatives of the UK, France, Japan, West Germany, the Peoples Republic of China, Sweden, and the U.S.S.R. The Symposium was divided into sessions concerning Materials and Measurements, Mirrors and Surfaces, Thin Films, and finally Fundamental Mechanisms. As in previous years, the emphasis of the papers presented at the Symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high-power apparatus. The wavelength range extended from 10.6 μm to the UV region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Arthur H. Guenther of the Air Force Weapons Laboratory, David Milam of the Lawrence Livermore National Laboratory, and Brian E. Newnam of the Los Alamos National Laboratory were cochairmen of the Symposium.