Damage In Optical Materials Research Articles

Systematic Study of LED Stimulated Recovery of Radiation Damage in Optical Materials

The radiation damage in optical materials mostly manifests itself as the loss of optical transmission. The optical materials recover from radiation damage to some extent in the presence of natural light, and at a faster rate in the presence of stimulating light. On the other hand, the systematic study of the dynamics of the recovery as a function of the stimulating light parameters such as its wavelength, intensity and exposure duration and method has not been performed in detail. We established an LED recovery station which provides pulsed and continuous light at various wavelengths at custom geometries. The study starts with the irradiation of optical samples at various gamma doses at a rate of 87.5 Gy/min. The optical transmittance of the samples are then measured in 200 nm - 1500 nm range for an extended period of time. Here we report on the details of the irradiation and recovery setups, and the results of recovery from radiation damage under different light exposure mechanisms.

Systematic study of LED stimulated recovery of radiation damage in optical materials

The radiation damage in optical materials mostly manifests itself as the loss of optical transmittance. The optical materials recover from radiation damage to some extent when the radiation exposure is stopped. The recovery is at a faster rate in the presence of stimulating light. On the other hand, a systematic study of the dynamics of the recovery as a function of the stimulating light parameters such as its wavelength, intensity and exposure duration and method has not been performed in detail yet.We established an LED recovery station which provides pulsed and continuous light at various wavelengths at custom geometries. We irradiated soda lime glass samples at a rate of 87.5 Gy/min to a total dose of 3.5 kGy and 7.0 kGy. The optical transmittance of the samples were then measured in 200 nm–1500 nm range for an extended period of time. The recovery from radiation damage is improved, both in terms of timing and quantity, as the wavelength of the stimulating light decreases. Around 50% improvement was measured both in recovery rate and the permanent damage when UV LED with a wavelength of 396 nm was used for stimulation. The trend is such that wavelengths deeper in the UV range would result in faster and more effective recovery from radiation damage. The LED stimulated recovery technique from radiation damage is a feasible implementation for the optical active media of radiation and particle detectors which operate in high radiation environments.

High laser induced damage threshold photoresists for nano-imprint and 3D multi-photon lithography

Abstract Optics manufacturing technology is predicted to play a major role in the future production of integrated photonic circuits. One of the major drawbacks in the realization of photonic circuits is the damage of optical materials by intense laser pulses. Here, we report on the preparation of a series of organic–inorganic hybrid photoresists that exhibit enhanced laser-induced damage threshold. These photoresists showed to be candidates for the fabrication of micro-optical elements (MOEs) using three-dimensional multiphoton lithography. Moreover, they demonstrate pattern ability by nanoimprint lithography, making them suitable for future mass production of MOEs.

Experimental Study on the Damage of Optical Materials by out of Band Composite Laser

For the paper, experimental studies were performed on the damage of the Ge- and Si-based flat window by lasers out-of-band. The experimental results showed that lasers out-of-band can cause film damage and substrate damage to Ge and Si windows. The high-energy laser damage window mechanism mainly manifested as thermal effects. The composite laser damage thresholds for the substrate were an Si window of 21.6 J/cm2 and a Ge window of 3 J/cm2. Compared with continuous laser and long pulse laser experimental results, it was found that the use of long pulse-continuous composite constitution could effectively reduce the damage threshold. Compared to the long-pulse laser, the composite laser could achieve similar damage effects with a smaller energy density.

Real-time, in situ probing of gamma radiation damage with packaged integrated photonic chips

Integrated photonics is poised to become a mainstream solution for high-speed data communications and sensing in harsh radiation environments, such as outer space, high-energy physics facilities, nuclear power plants, and test fusion reactors. Understanding the impact of radiation damage in optical materials and devices is thus a prerequisite to building radiation-hard photonic systems for these applications. In this paper, we report real-time, in situ analysis of radiation damage in integrated photonic devices. The devices, integrated with an optical fiber array package and a baseline-correction temperature sensor, can be remotely interrogated while exposed to ionizing radiation over a long period without compromising their structural and optical integrity. We also introduce a method to deconvolve the radiation damage responses from different constituent materials in a device. The approach was implemented to quantify gamma radiation damage and post-radiation relaxation behavior of SiO 2 -cladded SiC photonic devices. Our findings suggest that densification induced by Compton scattering displacement defects is the primary mechanism for the observed index change in SiC. Additionally, post-radiation relaxation in amorphous SiC does not restore the original pre-irradiated structural state of the material. Our results further point to the potential of realizing radiation-hard photonic device designs taking advantage of the opposite signs of radiation-induced index changes in SiC and SiO 2 .

基于SBS效应激光波长对光学材料损伤的影响

基于SBS效应激光波长对光学材料损伤的影响

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.

The Temperature Field Caused by Sphere Inclusion in Dielectric Irradiated by Single Pulse Laser

The thermal effect arisen from absorbing inclusions is the main factor which causes the damage of optical materials or component irradiated by the longer pulse duration laser. The unsteady heat conduction depends markedly on both the thermal properties of inclusions and the parameters of laser. Based on the differential equation of heat conduction, the temperature distribution caused by single absorbing inclusion is solved by use of finite difference method. The effect of the laser intensity and the pulse duration on temperature field is analyzed in detail. The result demonstrates that the smaller size inclusion and the smaller pulse duration cause relative safe thermal effect, consequently, the less probability to be damaged by thermal effect.

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.

Dynamics of laser-induced damage of spherical nanoparticles by high-intensity ultrashort laser pulses

Damage of a metal spherical nanoparticle by femtosecond laser pulses is analyzed by splitting the overall process into two steps. The fast step includes electron photoemission from a nanoparticle. It takes place during direct action of a laser pulse and its rate is evaluated as a function of laser and particle parameters by two approaches. Obtained results sug- gest the formation of significant positive charge of the nanoparticles due to the photoemission. The next step includes ion emission that removes the excessive positive charge and modifies particle structure. It is delayed with respect to the photo-emission and is analyzed by a simple analytical model and modified molecular dynamics. Obtained energy distribution suggests generation of fast ions capable of penetrating into surrounding material and generating defects next to the nanoparticle. The modeling is extended to the case of a nanoparticle on a solid surface to understand the basic mechanism of surface laser damage initiated by nano-contamina- tion. Simulations predict embedding the emitted ions into substrate within a spot with size significantly exceeding the original particle size. We discuss the relation of those effects to the problem of bulk and surface laser-induced damage of optical materials by single and multiple ultrashort laser pulses. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10 .1117/1.OE.51.12.121816)

Theory of laser-induced inclusion-initiated damage in optical materials

We present the results of theoretical studies of the laser-induced damage in transparent solids containing absorbing inclusions. The investigation is based on the inclusion-initiated thermal explosion model. Key aspects of the model are considered: thermal instability initiated by the inclusions; a mechanism of photoionization of a surrounding layer of a host material by a thermal ultraviolet-radiation of laser-heated inclusions; the thermal instability kinetics, and an associated pulse-width dependence of the laser-induced damage threshold. Also, statistical features of the damage, caused by random spatial distribution of the inclusions in the materials, and a final stage of the damage process-a mechanical stress-produced crack formation-are analyzed. A comparison of the theoretical results, related to the pulse-width dependence of the damage threshold, with experimental data for some typical optical materials in a wide pulse-width range is presented.

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).

Investigation of photoionization processes in ultrashort laser induced damage in optical materials

Theoretical investigation is presented on femtosecond laser induced damage in optically transparent materials, of different energy band gaps, by a single shot of different pulse durations (<10 ps). A computer simulation model is developed based on the Fokker–Planck approximation of the Boltzmann equation and allows for electron production via electron impact ionization, tunnelling ionization and multiphoton ionization processes. The calculated damage thresholds, of SiO2, Ta2O5 and Si at ∼800 nm laser wavelength, are in reasonable quantitative agreement with the examined experimental measurements. The relative importance of each ionization process is also examined.

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 at the October 7–9, 1996 Symposium on Optical Materials for High‐Power Lasers (the Boulder Damage Symposium) Boulder, Colorado

The 28th annual symposium on optical materials for high‐power lasers (Boulder damage symposium) was held at the National Institute of Standards and Technology in Boulder, CO, 7–9 October 1996. The symposium was held under the joint sponsorship of Bennett Optical Research, the Center for Research and Education in Optics and Lasers (CREOL) at the Center for Research and Education in Optics and Lasers (CREOL) at the University of Central Florida, Los Alamos National Laboratory, Lawrence Livermore National Laboratory, Sandia National Laboratories, and SPIE—The International Society for Optical Engineering. Over 130 scientists attended the symposium, including representatives from France, Germany, Japan, Russia, South Africa, Hungary, Armenia, Israel, the UK, and the US. The symposium was divided into sessions concerning materials and measurements, surfaces and mirrors, thin films, fundamental mechanisms, and a mini‐symposium on ‘Laser‐Induced Damage in Optical Fibers,’ organized by R. E. Setchell and Sandia National Laboratories. 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 laser systems. The wavelength range of prime interest was from 10.6 μm in the infrared to the UV region. Highlights included surface characterization, thin film/substrate boundaries, and advances in fundamental laser‐matter interactions and mechansims. Harold E. Bennett of Bennett Optical Research, Inc., Arthur H. Guenther of Sandia National Laboratories, Mark R. Kozlowski of the Lawrence Livermore National Laboratory, Brian E. Newnam of the Los Alamos National Laboratory, and M. J. Soileau of the University of Central Florida were co‐chairs of the symposium. The 29th annual symposium is scheduled for 6–8 October 1997 at the National Institute of Standards and Technology, Boulder, CO. An added feature will be a wholly self‐contained mini‐symposium on ‘Damage in Laser Diodes’ organized by David Welch of Spectra Diode Laboratories.

Optical analysis of damage profiles in ion implanted LiNbO 3

The measurement of optical waveguide modes is a sensitive tool for the assessment of radiation damage in optical materials. Refractive index profiles can be computed from the waveguide mode data. Unexpected features, such as differences in the index profiles of n 0 and n e for LiNbO 3, are discussed in terms of lattice relaxation, defect production, ion migration and variations in the local stoichiometry. Examples of anomalous features are the production in n e of high-index regions on either side of the reduced index nuclear damage peak. These effects are thought to result from ion diffusion towards the amorphised zone.

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.