Science.gov

Sample records for optical damage characterization

  1. Optical characterization in laser damage studies

    NASA Astrophysics Data System (ADS)

    Commandré, Mireille; Natoli, Jean Yves; Gallais, Laurent; Wagner, Frank; Amra, Claude

    2007-01-01

    The development of high power lasers and optical micro-components requires optical characterization techniques for studying behavior of optical materials under illumination, laser damage phenomena and ageing. More usual optical characterization tools are based on measurements of absorption, scattering and luminescence; they are non destructive evaluation techniques. It is important to combine several tools which allow getting complementary information. Optical tools can be used in damage initiation studies or to characterize properties of damaged areas. Because defects involved in laser damage initiation are sub-micrometer sized, both high spatial resolution and high sensitivity are required to detect defects as small as possible. Furthermore optical tools have to be implemented in damage set-up and at the same wavelength for a detailed analysis of damage mechanisms. We present an overview of recent developments in the field of optical characterization in connection with laser damage. Especially, a high resolution photothermal deflection microscopy has been coupled with a damage set-up to detect nano-absorbing precursors of damage and to study their behavior under irradiation. Thus model defects such as gold inclusions of various sizes have been followed through irradiation and results are compared with numerical simulations. Optical characterization allows to get determining information if several techniques are associated with numerical simulations.

  2. Ultrasonic Technology for Characterizing Laser Damage in Optics

    SciTech Connect

    Thomas, G; Martin, L P; Chambers, D

    2002-04-30

    An ultrasonic technique was developed to detect and characterize laser damage in critical optics. During normal usage, sub critical flaws induced by high laser fluence can grow to critical size and potentially can cause unanticipated failure of the optics. This ultrasonic technique monitors the optic in situ and provides a quick, reliable way to quantify the location, number and, ultimately, the size of defects that may initiate and grow during firing of the laser. The feasibility of detecting and sizing laser-induced damage with an ultrasonic technology was theoretically and experimentally demonstrated. An experiment was conducted whereby ultrasonic data was acquired in situ on an optic as it was damaged by a laser. This monitoring of laser induced damage clearly demonstrated the potential for ultrasonic monitoring of critical optics for laser-induced damage.

  3. Damage detection and characterization using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Glisic, Branko; Sigurdardottir, Dorotea; Yao, Yao; Hubbell, David

    2013-04-01

    Fiber optic sensors (FOS) have significantly evolved and have reached their market maturity during the last decade. Their widely recognized advantages are high precision, long-term stability, and durability. But in addition to these advantageous performances, FOS technologies allow for affordable instrumentation of large areas of structure enabling global large-scale monitoring based on long-gauge sensors and integrity monitoring based on distributed sensors. These two approaches are particularly suitable for damage detection and characterization, i.e., damage localization and to certain extent quantification and propagation, as illustrated by two applications presented in detail in this paper: post-tensioned concrete bridge and segmented concrete pipeline. Early age cracking was detected, localized and quantified in the concrete deck of a pedestrian bridge using embedded long-gauge FOS. Post-tensioning of deck closed the cracks; however, permanent weakening in a bridge joint occurred due to cracking and it was identified and quantified. The damage was confirmed using embedded distributed FOS and a separate load test of the bridge. Real-size concrete pipeline specimens and surrounding soil were equipped with distributed FOS and exposed to permanent ground displacement in a large-scale testing facility. Two tests were performed on different pipeline specimens. The sensors bonded on the pipeline specimens successfully detected and localized rupture of pipeline joints, while the sensors embedded in the soil were able to detect and localize the failure plane. Comparison with strain-gauges installed on the pipeline and visual inspection after the test confirmed accurate damage detection and characterization.

  4. Tissue Damage Characterization Using Non-invasive Optical Modalities

    NASA Astrophysics Data System (ADS)

    Diaz, David

    The ability to determine the degree of cutaneous and subcutaneous tissue damage is essential for proper wound assessment and a significant factor for determining patient treatment and morbidity. Accurate characterization of tissue damage is critical for a number of medical applications including surgical removal of nonviable tissue, severity assessment of subcutaneous ulcers, and depth assessment of visually open wounds. The main objective of this research was to develop a non-invasive method for identifying the extent of tissue damage underneath intact skin that is not apparent upon visual examination. This work investigated the relationship between tissue optical properties, blood flow, and tissue viability by testing the hypotheses that (a) changes in tissue oxygenation and/or microcirculatory blood flow measurable by Diffuse Near Infrared Spectroscopy (DNIRS) and Diffuse Correlation Spectroscopy (DCS) differ between healthy and damaged tissue and (b) the magnitude of those changes differs for different degrees of tissue damage. This was accomplished by developing and validating a procedure for measuring microcirculatory blood flow and tissue oxygenation dynamics at multiple depths (up to 1 centimeter) using non-invasive DCS and DNIRS technologies. Due to the lack of pressure ulcer animal models that are compatible with our optical systems, a proof of concept was conducted in a porcine burn model prior to conducting clinical trials in order to assess the efficacy of the system in-vivo. A reduction in total hemoglobin was observed for superficial (5%) and deep burns (35%) along with a statistically significant difference between the optical properties of superficial and deep burns (p < 0.05). Burn depth and viable vessel density were estimated via histological samples. 42% of vessels in the dermal layer were viable for superficial burns, compared to 25% for deep burns. The differences detected in optical properties and hemoglobin content by optical measurements

  5. Damage characterization in engineering materials using a combination of optical, acoustic, and thermal techniques

    NASA Astrophysics Data System (ADS)

    Tragazikis, I. K.; Exarchos, D. A.; Dalla, P. T.; Matikas, T. E.

    2016-04-01

    This paper deals with the use of complimentary nondestructive methods for the evaluation of damage in engineering materials. The application of digital image correlation (DIC) to engineering materials is a useful tool for accurate, noncontact strain measurement. DIC is a 2D, full-field optical analysis technique based on gray-value digital images to measure deformation, vibration and strain a vast variety of materials. In addition, this technique can be applied from very small to large testing areas and can be used for various tests such as tensile, torsion and bending under static or dynamic loading. In this study, DIC results are benchmarked with other nondestructive techniques such as acoustic emission for damage localization and fracture mode evaluation, and IR thermography for stress field visualization and assessment. The combined use of these three nondestructive methods enables the characterization and classification of damage in materials and structures.

  6. Damage detection and characterization using long-gauge and distributed fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Glišić, Branko; Hubbell, David; Sigurdardottir, Dorotea Hoeg; Yao, Yao

    2013-08-01

    Fiber optic strain sensors have significantly evolved and have reached their market maturity during the last decade. Their widely recognized advantages are high precision, long-term stability, and durability. In addition to these benefits, fiber optic (FO) techniques allow for affordable instrumentation of large areas of civil structures and infrastructure enabling global large-scale monitoring based on long-gauge sensors, and integrity monitoring based on distributed sensors. The FO techniques that enable these two approaches are based on fiber Bragg-gratings and Brillouin optical time-domain analysis. The aim of this paper is to present both FO techniques and both structural assessment approaches, and to validate them through large-scale applications. Although many other currently applied methods fail to detect the damage in real, on-site conditions, the presented approaches were proven to be suitable for damage detection and characterization, i.e., damage localization and, to certain extent, quantification. This is illustrated by two applications presented in detail in this paper: the first on a post-tensioned concrete bridge and the second on segmented concrete pipeline.

  7. Use of nondestructive inspection and fiber optic sensing for damage characterization in carbon fiber fuselage structure

    NASA Astrophysics Data System (ADS)

    Neidigk, Stephen; Le, Jacqui; Roach, Dennis; Duvall, Randy; Rice, Tom

    2014-04-01

    To investigate a variety of nondestructive inspection technologies and assess impact damage characteristics in carbon fiber aircraft structure, the FAA Airworthiness Assurance Center, operated by Sandia National Labs, fabricated and impact tested two full-scale composite fuselage sections. The panels are representative of structure seen on advanced composite transport category aircraft and measured approximately 56"x76". The structural components consisted of a 16 ply skin, co-cured hat-section stringers, fastened shear ties and frames. The material used to fabricate the panels was T800 unidirectional pre-preg (BMS 8-276) and was processed in an autoclave. Simulated hail impact testing was conducted on the panels using a high velocity gas gun with 2.4" diameter ice balls in collaboration with the University of California San Diego (UCSD). Damage was mapped onto the surface of the panels using conventional, hand deployed ultrasonic inspection techniques, as well as more advanced ultrasonic and resonance scanning techniques. In addition to the simulated hail impact testing performed on the panels, 2" diameter steel tip impacts were used to produce representative impact damage which can occur during ground maintenance operations. The extent of impact damage ranges from less than 1 in2 to 55 in2 of interply delamination in the 16 ply skin. Substructure damage on the panels includes shear tie cracking and stringer flange disbonding. It was demonstrated that the fiber optic distributed strain sensing system is capable of detecting impact damage when bonded to the backside of the fuselage.

  8. Sub-picosecond laser induced damage test facility for petawatt reflective optical components characterizations

    NASA Astrophysics Data System (ADS)

    Sozet, Martin; Néauport, Jérôme; Lavastre, Eric; Roquin, Nadja; Gallais, Laurent; Lamaignère, Laurent

    2015-05-01

    While considering long pulse or short pulse high power laser facilities, optical components performances and in particular laser damage resistance are always factors limiting the overall system performances. Consequently, getting a detailed knowledge of the behavior of these optical components under irradiations with large beam in short pulse range is of major importance. In this context, a Laser Induced Damage Threshold test facility called DERIC has been developed at the Commissariat à l'Energie Atomique et aux Energies Alternatives, Bordeaux. It uses an Amplitude Systemes laser source which delivers Gaussian pulses of 500 fs at 1053 nm. 1-on-1, S-on-1 and RasterScan test procedures are implemented to study the behavior of monolayer and multilayer dielectric coatings.

  9. CHARACTERIZATION OF DAMAGED MATERIALS

    SciTech Connect

    Hsu, P C; Dehaven, M; McClelland, M; Chidester, S; Maienschein, J L

    2006-06-23

    Thermal damage experiments were conducted on LX-04, LX-10, and LX-17 at high temperatures. Both pristine and damaged samples were characterized for their material properties. A pycnometer was used to determine sample true density and porosity. Gas permeability was measured in a newly procured system (diffusion permeameter). Burn rate was measured in the LLNL strand burner. Weight losses upon thermal exposure were insignificant. Damaged pressed parts expanded, resulting in a reduction of bulk density by up to 10%. Both gas permeabilities and burn rates of the damaged samples increased by several orders of magnitude due to higher porosity and lower density. Moduli of the damaged materials decreased significantly, an indication that the materials became weaker mechanically. Damaged materials were more sensitive to shock initiation at high temperatures. No significant sensitization was observed when the damaged samples were tested at room temperature.

  10. Optical characterization of free-falling mold-damaged wheat kernels

    NASA Astrophysics Data System (ADS)

    Delwiche, Stephen R.

    2007-09-01

    One of the most common molds that infects the seeds of small cereals worldwide, such as wheat, is Fusarium Head Blight (FHB). The mycotoxin, deoxynivalenol (also known as DON or vomitoxin) is often produced by this mold, which, upon ingestion, causes health problems to not only livestock (especially non-ruminants), but to humans as well. In the United States, the FDA has established advisory levels for DON in food and feeds, a practice that is likewise conducted by most countries of the world. Our previous research has shown that commercial high-speed optical sorters are on average 50 percent efficient at the removal of mold-damaged kernels; however, under more careful control in the laboratory, this efficiency can rise to 95 percent or better. Ongoing research is examining the potential to achieve the higher efficiencies at conditions that are more akin to those of commercial processing. For example, multispectral information is collected on single kernels in freefall at the sub-millisecond level. Knowledge gained from this research will provide design criteria for improvement of high-speed optical sorters for reduction of DON in raw cereals commodities, as well as in finished food products.

  11. Subsurface defect characterization and laser-induced damage performance of fused silica optics polished with colloidal silica and ceria

    NASA Astrophysics Data System (ADS)

    Xiang, He; Gang, Wang; Heng, Zhao; Ping, Ma

    2016-04-01

    This paper mainly focuses on the influence of colloidal silica polishing on the damage performance of fused silica optics. In this paper, nanometer sized colloidal silica and micron sized ceria are used to polish fused silica optics. The colloidal silica polished samples and ceria polished samples exhibit that the root-mean-squared (RMS) average surface roughness values are 0.7 nm and 1.0 nm, respectively. The subsurface defects and damage performance of the polished optics are analyzed and discussed. It is revealed that colloidal silica polishing will introduce much fewer absorptive contaminant elements and subsurface damages especially no trailing indentation fracture. The 355-nm laser damage test reveals that each of the fused silica samples polished with colloidal silica has a much higher damage threshold and lower damage density than ceria polished samples. Colloidal silica polishing is potential in manufacturing high power laser optics.

  12. Pulsed laser damage to optical fibers

    SciTech Connect

    Allison, S.W.; Gillies, G.T.; Magnuson, D.W.; Pagano, T.S.

    1985-10-01

    This paper describes some observations of pulsed laser damage to optical fibers with emphasis on a damage mode characterized as a linear fracture along the outer core of a fiber. Damage threshold data are presented which illustrate the effects of the focusing lens, end-surface preparation, and type of fiber. An explanation based on fiber-beam misalignment is given and is illustrated by a simple experiment and ray trace.

  13. A fiber optic damage monitor

    NASA Astrophysics Data System (ADS)

    Jen, C. K.; Cielo, P.; Farnell, G. W.; Parker, M.

    A simplified fiber-optic damage monitoring system for on-line assessments of the condition of composite structural materials in F/A-18 fighters is described. Optical fibers are implanted into the composite mesh in a configuration with horizontal and vertical orientations. When light is pumped into the fibers, and failure of transmittance in either the x- or y-coordinates indicates the location of a defect at that coordinate, as revealed by the fiber damage. Attaching photodiodes to the optic fibers and connecting the entire system to a video camera and computer permits on-line monitoring of the mesh-holding panels. Sample results are provided from a system with multimode step index fibers, a VAX 11/780 computer and a video camera with a 488 x 380 cell photodiode array. Image subtraction is an effective means for fast determination of the identities of broken fibers by comparisons of images of arrays of original and damaged fibers.

  14. Damage thresholds in laser irradiated optical materials

    SciTech Connect

    Guignard, F.; Autric, M.; Baudinaud, V.

    1997-12-01

    An experimental study on the damage induced by laser irradiation on different materials, borosilicate glass, fused silicate, moulded and stretched polymethylmethacrylate (PMMA), has been performed. The irradiation source is a 1KJ pulsed cold cathode electron gun preionized TEA CO{sub 2} laser. Damage mechanisms are controlled by the in-depth absorption of the 10,6 {mu}m radiation according to the Beer-Lambert law. The heating of the interaction area gives rise to thermal or thermo-mechanical damages. PMMA is damaged following a boiling process. Stretched PMMA is fractured first, releasing stresses, then boiled like moulded PMMA at higher energy. BK7 crazed after the irradiation due to thermomechanical stresses, silicate melt and vaporized. Optical damages have been characterized by measuring the contrast transfer function through the irradiated samples.

  15. Method for producing damage resistant optics

    DOEpatents

    Hackel, Lloyd A.; Burnham, Alan K.; Penetrante, Bernardino M.; Brusasco, Raymond M.; Wegner, Paul J.; Hrubesh, Lawrence W.; Kozlowski, Mark R.; Feit, Michael D.

    2003-01-01

    The present invention provides a system that mitigates the growth of surface damage in an optic. Damage to the optic is minimally initiated. In an embodiment of the invention, damage sites in the optic are initiated, located, and then treated to stop the growth of the damage sites. The step of initiating damage sites in the optic includes a scan of the optic using a laser to initiate defects. The exact positions of the initiated sites are identified. A mitigation process is performed that locally or globally removes the cause of subsequent growth of the damaged sites.

  16. Unidirectional growth of potassium hydrogen malate single crystals and its characterizations on optical, mechanical, dielectric, laser damage threshold studies

    NASA Astrophysics Data System (ADS)

    Boopathi, K.; Rajesh, P.; Ramasamy, P.

    2013-02-01

    Single crystals of potassium hydrogen malate (PHM) were successfully grown by Sankaranarayanan-Ramasamy (SR) method and conventional slow evaporation solution technique which have the sizes of 35 mm in length, 20 mm in diameter and 15 × 10 × 3 mm3 respectively. The grown PHM crystals have been subjected to single crystal X-ray diffractometer, UV-Vis NIR studies, dielectric measurements, Vickers microhardness analysis and Laser damage threshold. The range and percentage of optical transmission is represented by recording UV-Vis-NIR analysis. The dielectric constant and loss measurement was made as function of temperature in the range of 40-150°C. Mechanical strength and laser stability of the SR method grown crystals was higher than the conventional method grown crystal.

  17. Methods for globally treating silica optics to reduce optical damage

    DOEpatents

    Miller, Philip Edward; Suratwala, Tayyab Ishaq; Bude, Jeffrey Devin; Shen, Nan; Steele, William Augustus; Laurence, Ted Alfred; Feit, Michael Dennis; Wong, Lana Louie

    2012-11-20

    A method for preventing damage caused by high intensity light sources to optical components includes annealing the optical component for a predetermined period. Another method includes etching the optical component in an etchant including fluoride and bi-fluoride ions. The method also includes ultrasonically agitating the etching solution during the process followed by rinsing of the optical component in a rinse bath.

  18. Optical components damage parameters database system

    NASA Astrophysics Data System (ADS)

    Tao, Yizheng; Li, Xinglan; Jin, Yuquan; Xie, Dongmei; Tang, Dingyong

    2012-10-01

    Optical component is the key to large-scale laser device developed by one of its load capacity is directly related to the device output capacity indicators, load capacity depends on many factors. Through the optical components will damage parameters database load capacity factors of various digital, information technology, for the load capacity of optical components to provide a scientific basis for data support; use of business processes and model-driven approach, the establishment of component damage parameter information model and database systems, system application results that meet the injury test optical components business processes and data management requirements of damage parameters, component parameters of flexible, configurable system is simple, easy to use, improve the efficiency of the optical component damage test.

  19. Large area damage testing of optics

    SciTech Connect

    Sheehan, L.; Kozlowski, M.; Stolz, C.

    1996-04-26

    The damage threshold specifications for the National Ignition Facility will include a mixture of standard small-area tests and new large-area tests. During our studies of laser damage and conditioning processes of various materials we have found that some damage morphologies are fairly small and this damage does not grow with further illumination. This type of damage might not be detrimental to the laser performance. We should therefore assume that some damage can be allowed on the optics, but decide on a maximum damage allowance of damage. A new specification of damage threshold termed {open_quotes}functional damage threshold{close_quotes} was derived. Further correlation of damage size and type to system performance must be determined in order to use this measurement, but it is clear that it will be a large factor in the optics performance specifications. Large-area tests have verified that small-area testing is not always sufficient when the optic in question has defect-initiated damage. This was evident for example on sputtered polarizer and mirror coatings where the defect density was low enough that the features could be missed by standard small- area testing. For some materials, the scale-length at which damage non-uniformities occur will effect the comparison of small-area and large-area tests. An example of this was the sub-aperture tests on KD*P crystals on the Beamlet test station. The tests verified the large-area damage threshold to be similar to that found when testing a small-area. Implying that for this KD*P material, the dominate damage mechanism is of sufficiently small scale-length that small-area testing is capable of determining the threshold. The Beamlet test station experiments also demonstrated the use of on-line laser conditioning to increase the crystals damage threshold.

  20. Growth, crystalline perfection, optical, thermal, laser damage threshold and electrical characterization of melaminium levulinate monohydrate single crystal

    NASA Astrophysics Data System (ADS)

    Sivakumar, N.; Kanagathara, N.; Bhagavannarayana, G.; Kalainathan, S.; Anbalagan, G.

    2015-09-01

    Equimolar amounts of melamine and levulinic acid results an organic crystal of melaminium levulinate monohydrate (MLM) at room temperature. MLM belongs to a monoclinic crystal structure having P21/c space group which was confirmed by single crystal X-ray diffraction study. Functional groups present in the MLM crystal were identified by FT-IR spectral study. HRXRD study dictates the quality of MLM crystal. UV-visble spectrum of MLM reveals the lower cut-off wavelength of 293 nm with 55% optical transparency and optical band gap was found to be 4.20 eV for the prominent plane (1 0 -1). Refractive indices for the three axes of MLM crystal were found to be nx=2.6, ny=2.4 and nz=2.2 respectively. Further the thermal stability and melting point of MLM crystal were investigated by TG/DTA study. Dielectric permittivity tensor components were estimated for the planes (1 0 -1), (0 1 0) and (1 1 1) respectively. The thermal conductivity of the crystal by Wiedemann-Franz law was found to be 5.99×10-11 W/mK at 70 °C. LDT value (2.84 GW/cm2) of MLM was estimated for laser optical device applications.

  1. Optical detection of DNA damage

    NASA Astrophysics Data System (ADS)

    Rogers, Kim R.; Apostol, A.; Cembrano, J.

    1999-02-01

    A rapid and sensitive fluorescence assay for oxidative damage to calf thymus DNA is reported. A decrease in the transition temperature for strand separation resulted from exposure of the DNA to the reactive decomposition products of 3- morpholinosydnonimine (SIN-1) (i.e., nitric oxide, superoxide, peroxynitrite, hydrogen peroxide, and hydroxyl radicals). A decrease in melting temperature of 12 degrees Celsius was indicative of oxidative damage including single strand chain breaks. Double stranded (ds) and single stranded (ss) forms of DNA were determined using the indicator dyes ethidium bromide and PicoGreen. The change in DNA 'melting' curves was dependant on the concentration of SIN-1 and was most pronounced at 75 degrees Celsius. This chemically induced damage was significantly inhibited by sodium citrate, tris(hydroxymethyl)aminomethane (Tris), and diethylenetriaminepentaacetic acid (DTPA), but was unaffected by superoxide dismutase (SOD), catalase, ethylenediamine tetraacietic acid (EDTA), or deferoxamine. Lowest observable effect level for SIN-1-induced damage was 200 (mu) M.

  2. Role of point defects in optical damage of nonlinear crystals

    NASA Astrophysics Data System (ADS)

    Scripsick, Michael P.; Edwards, Gary J.

    1993-07-01

    We have initiated a program at West Virginia University to establish the properties of point defects that are relevant to the optical damage phenomena in KTP, BBO, and LBO crystals. Defects have been characterized using optical absorption, electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and luminescence techniques. Among the defects which have been observed are impurity ions (iron, platinum, hydrogen, etc.), trapped hole centers, and trapped electron centers.

  3. Electro-Optical Characterization

    SciTech Connect

    Not Available

    2006-06-01

    In the Electro-Optical Characterization group, within the National Center for Photovoltaic's Measurements and Characterization Division, we use various electrical and optical experimental techniques to relate photovoltaic device performance to the methods and materials used to produce them. The types of information obtained by these techniques range from small-scale atomic-bonding information to large-scale macroscopic quantities such as optical constants and electron-transport properties. Accurate and timely measurement of the electro-optical properties as a function of device processing provides researchers and manufacturers with the knowledge needed to troubleshoot problems and develop the knowledge base necessary for reducing cost, maximizing efficiency, improving reliability, and enhancing manufacturability. We work collaboratively with you to solve materials- and device-related R&D problems. This sheet summarizes our primary techniques and capabilities.

  4. FIBER OPTIC BIOSENSOR FOR DNA DAMAGE

    EPA Science Inventory

    This paper describes a fiber optic biosensor for the rapid and sensitive detection of radiation-induced or chemically-induced oxidative DNA damage. The assay is based on the hybridization and temperature-induced dissociation (melting curves) of synthetic oligonucleotides. The...

  5. Optical Characterization Laboratory (Fact Sheet)

    SciTech Connect

    Not Available

    2011-10-01

    This fact sheet describes the purpose, lab specifications, applications scenarios, and information on how to partner with NREL's Optical Characterization Laboratory at the Energy Systems Integration Facility. The Optical Characterization Laboratory at NREL's Energy Systems Integration Facility (ESIF) conducts optical characterization of large solar concentration devices. Concentration solar power (CSP) mirror panels and concentrating solar systems are tested with an emphasis is on measurement of parabolic trough mirror panels. The Optical Characterization Laboratory provides state-of-the-art characterization and testing capabilities for assessing the optical surface quality and optical performance for various CSP technologies including parabolic troughs, linear Fresnel, dishes, and heliostats.

  6. Modeling and characterization of recompressed damaged materials

    SciTech Connect

    Becker, R; Cazamias, J U; Kalantar, D H; LeBlanc, M M; Springer, H K

    2004-02-11

    Experiments have been performed to explore conditions under which spall damage is recompressed with the ultimate goal of developing a predictive model. Spall is introduced through traditional gas gun techniques or with laser ablation. Recompression techniques producing a uniaxial stress state, such as a Hopkinson bar, do not create sufficient confinement to close the porosity. Higher stress triaxialities achieved through a gas gun or laser recompression can close the spall. Characterization of the recompressed samples by optical metallography and electron microscopy reveal a narrow, highly deformed process zone. At the higher pressures achieved in the gas gun, little evidence of spall remains other than differentially etched features in the optical micrographs. With the very high strain rates achieved with laser techniques there is jetting from voids and other signs of turbulent metal flow. Simulations of spall and recompression on micromechanical models containing a single void suggest that it might be possible to represent the recompression using models similar to those employed for void growth. Calculations using multiple, randomly distributed voids are needed to determine if such models will yield the proper behavior for more realistic microstructures.

  7. Damage thresholds in laser-irradiated optical materials

    NASA Astrophysics Data System (ADS)

    Guignard, Franck; Autric, Michel L.; Baudinaud, Vincent

    1997-05-01

    An experimental study on the damage induced by laser irradiation on different materials, borosilicate glass, fused silicate, molded and stretched polymethylmethacrylate (PMMA), has been performed. The irradiation source is a 1KL pulsed cold cathode electron gun preionized TEA CO2 laser. Damage mechanisms are controlled by the in-depth absorption of the 10.6 micrometers radiation according to the Beer-Lambert law. PMMA is damaged following a boiling process. Stretched PMMA is fractured first, releasing stresses, then boiled like molded PMMA at a higher energy. BK7 crazed after the irradiation due to thermomechanical stresses, silicate melt and vaporized. Optical damages have been characterized by measuring the contrast transfer function through the irradiated samples.

  8. Atomic oxygen damage characterization by photothermal scanning

    NASA Technical Reports Server (NTRS)

    Williams, A. W.; Wood, N. J.; Zakaria, A. B.

    1993-01-01

    In this paper we use a photothermal imaging technique to characterize the damage caused to an imperfectly coated gold-coated Kapton sample exposed to successively increased fluences of atomic oxygen in a laboratory atomic source.

  9. Phonons, defects and optical damage in crystalline acetanilide

    NASA Astrophysics Data System (ADS)

    Kosic, Thomas J.; Hill, Jeffrey R.; Dlott, Dana D.

    1986-04-01

    Intense picosecond pulses cause accumulated optical damage in acetanilide crystals at low temperature. Catastrophic damage to the irradiated volume occurs after an incubation period where defects accumulate. The optical damage is monitored with subanosecond time resolution. The generation of defects is studied with damage-detected picosecond spectroscopy. The accumulation of defects is studied by time-resolved coherent Raman scattering, which is used to measure optical phonon scattering from the accumulating defects.

  10. CHARACTERIZATION OF THERMALLY DAMAGED LX-17

    SciTech Connect

    Hsu, P C

    2007-07-11

    Thermal damage was applied to LX-17 at 190 C for several hours. The damaged LX-17 samples, after cooled down to room temperature, were characterized for their material properties (density, porosity, permeability, moduli), safety, and performance. Weight losses upon thermal exposure were insignificant (< 0.1% wt.). The damaged LX-17 samples expanded, resulting in a bulk density reduction of 4.3%. Subsequent detonation measurements (cylinder tests) were conducted on the thermally-damaged LX-17 samples. The results showed that the fractions of damaged LX-17 reacted were slightly lower than those of pristine LX-17. The thermally damaged LX-17 had a detonation velocity of 7.315 mm/{micro}s, lower than that (7.638 mm/{micro}s) of pristine LX-17. Detonation energy density for the damaged LX-17 was 5.08 kJ/cm{sup 3}, about 9.0% lower than the detonation energy density of 5.50 kJ/cm{sup 3} for the pristine LX-17. The break-out curves showed reaction zone lengths for pristine LX-17 and damaged LX-17 were similar but the damaged samples had ragged detonation fronts.

  11. Measurements and characterization - Electro-optical characterization

    SciTech Connect

    Cook, G.

    2000-03-16

    This brochure presents the capabilities that the Measurements and Characterization Division has in Electro-Optical Characterization, in which a variety of spectroscopy, ellipsometry, and capacitance techniques are used to probe the fundamental electrical and optical properties of solid-state materials.

  12. Fracture Induced Sub-Band Absorption as a Precursor to Optical Damage on Fused Silica Surfaces

    SciTech Connect

    Miller, P E; Bude, J D; Suratwala, T I; Shen, N; Laurence, T A; Steele, W A; Menapace, J; Feit, M D; Wong, L L

    2010-03-05

    The optical damage threshold of indentation induced flaws on fused silica surfaces was explored. Mechanical flaws were characterized by laser damaged testing, SEM, optical, and photoluminescence microscopy. Localized polishing, chemical etching, and the control of indentation morphology were used to isolate the structural features which limit optical damage. A thin defect layer on fracture surfaces, including those smaller than the wavelength of visible light, was found to be the dominant source of laser damage initiation during illumination with 355nm, 3ns laser pulses. Little evidence was found that either displaced or densified material or fluence intensification plays a significant role in optical damage at fluences >35J/cm{sup 2}. Elimination of the defect layer was shown to increase the overall damage performance of fused silica optics.

  13. Triboluminescent Materials for Smart Optical Damage Sensors for Space Applications

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D.; Penn, B. G.; Miller, J.; Sadate, S.; Batra, A. K.

    2008-01-01

    There is a need to develop a new technique of damage detection for composites, which could detect cracking or delamination from any desired location within a material structure in real time. Recently, triboluminescent materials have been proposed as smart sensors of structural damage. To sense the damage, these materials can be epoxy bonded, coated in a polymer matrix, or embedded in a composite host structure. When the damage or fracture takes place in the host structure, the resultant fracture of triboluminescent crystals creates a light emission. This will warn in real time that structural damage has occurred. The triboluminescent emission of the candidate phosphor has to be bright enough that the light reaching from the point of fracture to the detector through a fiber optic cable is detectable. There are a large number of triboluminescent materials, but few satisfy the above criterion. The authors have synthesized an organic material known as Europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA), which is a potential candidate for application as a damage sensor and could be made into a wireless sensor with the addition of microchip, antenna, and electronics. Preliminary results on the synthesis and characterization of this material are presented.

  14. Automated damage test facilities for materials development and production optic quality assurance at Lawrence Livermore National Laboratory

    SciTech Connect

    Battersby, C; Dickson, R; Jennings, R; Kimmons, J; Kozlowski, M R; Maricle, S; Mouser, R; Runkel, M; Schwartz, S; Sheehan, L M; Weinzapfel, C

    1998-12-22

    The Laser Program at LLNL has developed automated facilities for damage testing optics up to 1 meter in diameter. The systems were developed to characterize the statistical distribution of localized damage performance across large-aperture National Ignition Facility optics. Full aperture testing is a key component of the quality assurance program for several of the optical components. The primary damage testing methods used are R:1 mapping and raster scanning. Automation of these test methods was required to meet the optics manufacturing schedule. The automated activities include control and diagnosis of the damage-test laser beam as well as detection and characterization of damage events.

  15. Laser damage threshold measurements of optical materials for direct laser accelerators

    SciTech Connect

    Soong, Ken; Byer, R. L.; Colby, E. R.; England, R. J.; Peralta, E. A.

    2012-12-21

    The laser-damage threshold is a fundamental limit for any dielectric laser-driven accelerator and is set by the material of the structure. In this paper, we present a theoretical model of the laser damage mechanism, in comparison with experimental data on the damage threshold of silicon. Additionally, we present damage threshold measurement data of various optical materials, most of which have not been previously characterized in the picosecond-regime.

  16. Triboluminescent Materials for Smart Optical Damage Sensors for Space Applications

    NASA Technical Reports Server (NTRS)

    Aggarwal, Mohan D.; Penn, Benjamin G.; Miller, Jim

    2007-01-01

    Triboluminescence is light that is produced by pressure, friction or mechanical shock. New composite materials are constantly being reengi neered in an effort to make lightweight spacecrafts for various NASA missions. For these materials there is interest in monitoring the con dition of the composite in real time to detect any delamination or cr acking due to damage, fatigue or external forces. Methods of periodic inspection of composite structures for mechanical damage such as ult rasonic testing are rather mature. However, there is a need to develop a new technique of damage detection for composites, which could dete ct cracking or delamination from any desired location within a materi al structure in real time. This could provide a valuable tool in the confident use of composite materials for various space applications. Recently, triboluminnescent materials have been proposed as smart sen sors of structural damage. To sense the damage, these materials can b e epoxy bonded or coated in a polymer matrix or embedded in a composi te host structure. When the damage or fracture takes place in the hos t structure, it will lead to the fracture of triboluminescent crystal s resulting in a light emission. This will warn, in real time, that a structural damage has occurred. The triboluminescent emission of the candidate phosphor has to be sufficiently bright, so that the light signal reaching from the point of fracture to the detector through a fiber optic cable is sufficiently strong to be detected. There are a large number of triboluminescent materials, but few satisfy the above criterion. Authors have synthesized a Eu based organic material know n as Europium tetrakis (dibenzoylmethide) triethylammonium .(EuD(sub 4)TEA), one of the bright triboluminescent materials, which is a pote ntial candidate for application as a damage sensor and could be made into a wireless sensor with the addition of microchip, antenna and el ectronics. Preliminary results on the synthesis and

  17. Characterization and damage evaluation of advanced materials

    NASA Astrophysics Data System (ADS)

    Mitrovic, Milan

    Mechanical characterization of advanced materials, namely magnetostrictive and graphite/epoxy composite materials, is studied in this dissertation, with an emphasis on damage evaluation of composite materials. Consequently, the work in this dissertation is divided into two parts, with the first part focusing on characterization of the magneto-elastic response of magnetostrictlve materials, while the second part of this dissertation describes methods for evaluating the fatigue damage in composite materials. The objective of the first part of this dissertation is to evaluate a nonlinear constitutive relation which more closely depict the magneto-elastic response of magnetostrictive materials. Correlation between experimental and theoretical values indicate that the model adequately predicts the nonlinear strain/field relations in specific regimes, and that the currently employed linear approaches are inappropriate for modeling the response of this material in a structure. The objective of the second part of this dissertation is to unravel the complexities associated with damage events associated with polymeric composite materials. The intent is to characterize and understand the influence of impact and fatigue induced damage on the residual thermo-mechanical properties and compressive strength of composite systems. The influence of fatigue generated matrix cracking and micro-delaminations on thermal expansion coefficient (TEC) and compressive strength is investigated for woven graphite/epoxy composite system. Experimental results indicate that a strong correlation exists between TEC and compressive strength measurements, indicating that TEC measurements can be used as a damage metric for this material systems. The influence of delaminations on the natural frequencies and mode shapes of a composite laminate is also investigated. Based on the changes of these parameters as a function of damage, a methodology for determining the size and location of damage is suggested

  18. Cleanliness and damage measurements of optics in atmospheric sensing high energy lasers

    SciTech Connect

    Harvey, G.A.; Chyba, T.H.; Cimolino, M.C.

    1996-12-31

    Langley Research Center has several atmospheric remote sensing programs which utilize, high energy pulsed lasers. These lasers typically have many damaged optics after several million shots. Damage is defined herein as color changes and/or optical flaws seen in microscopic inspection, and does not necessarily relate to measured performance degradation of the optic. Inspections and measurements of some of these optics indicate that energy thresholds for several million shots damage is about an order of magnitude lower than that for single shot damage. Damage initiation is often at micron size areas at the coating interface, which grows and sometimes develops as erosion of the top of the coating. There is a wide range in polish and coating quality of new optics, even on different faces of the same optic. Military Standard 1246C can be used to provide overall particulate, and molecular film, or nonvolatile residue (NTVR) cleanliness scales. Microscopic inspections and photography at I0x to 500x with brightfield (perpendicular) and darkfield (oblique) illumination are useful in assigning cleanliness levels of new and in-service optics. Microextraction (effecting concentration of molecular films to small areas) provides for enhanced optical detection and surface film chemical analysis by electron-microscope energy-dispersive-spectroscopy (EDS). Similar measurement techniques can be used to characterize and document optical damage initiation and optical damage growth. Surface contamination interferes with and complicates measurements of polish and coating quality, and of optical damage. This work indicates ultrasonic cleaning, and packaging of optics in Teflon sleeves or cups is advantageous over conventional cleaning and packaging for characterization of new optics.

  19. Cleanliness and damage measurements of optics in atmospheric-sensing high-energy lasers

    NASA Astrophysics Data System (ADS)

    Harvey, Gale A.; Chyba, Thomas H.; Cimolino, Marc C.

    1996-05-01

    Langley Research Center has several atmospheric remote sensing programs which utilize high energy pulsed lasers. These lasers typically have many damaged optics after several million shots. Damage is defined herein as color changes and/or optical flaws seen in microscopic inspection, and does not necessarily relate to measured performance degradation of the optic. Inspections and measurements of some of these optics indicate that energy thresholds for several million shots damage is about an order of magnitude lower than that for single shot damage. Damage initiation is often at micron size areas at the coating interface, which grows and sometimes develops as erosion of the top of the coating. There is a wide range in polish and coating quality of new optics, even on different faces of the same optic. Military Standard 1246C can be used to provide overall particulate, and molecular film, or nonvolatile residue cleanliness scales. Microscopic inspections and photography at 10X to 500X with brightfield (perpendicular) and darkfield (oblique) illumination are useful in assigning cleanliness levels of new and in-service optics. Microextraction (effecting concentration of molecular films to small areas) provides for enhanced optical detection and surface film chemical analysis by electron-microscope energy-dispersive-spectroscopy. Similar measurement techniques can be used to characterize and document optical damage initiation and optical damage growth. Surface contamination interferes with and complicated measurements of polish and coating quality, and of optical damage. Our work indicates ultrasonic cleaning, and packaging of optics in Teflon sleeves or cups is advantageous over conventional cleaning and packaging for characterization of new optics.

  20. Thermal Damage Characterization of Energetic Materials

    SciTech Connect

    Hsu, P C; DeHaven, M R; Springer, H K; Maienschein, J L

    2009-08-14

    We conducted thermal damage experiments at 180?C on PBXN-9 and characterized its material properties. Volume expansion at high temperatures was very significant which led to a reduction in material density. 2.6% of weight loss was observed, which was higher than other HMX-based formulations. Porosity of PBXN-9 increased to 16% after thermal exposure. Small-scale safety tests (impact, friction, and spark) showed no significant sensitization when the damaged samples were tested at room temperature. Gas permeation measurements showed that gas permeability in damaged materials was several orders of magnitude higher than that in pristine materials. In-situ measurements of gas permeability and density were proved to be possible at higher temperatures.

  1. Thermal Damage Characterization of Energetic Materials

    NASA Astrophysics Data System (ADS)

    Hsu, P. C.; DeHaven, M. R.; Springer, H. K.; Maienschein, J. L.

    2009-12-01

    We conducted thermal damage experiments at 180° C on PBXN-9 and characterized its material properties. Volume expansion at high temperatures was very significant which led to a reduction in material density. 2.6% of weight loss was observed, which was higher than other HMX-based formulations. Porosity of PBXN-9 increased to 16% after thermal exposure. Small-scale safety tests (impact, friction, and spark) showed no significant sensitization when the damaged samples were tested at room temperature. Gas permeation measurements showed that gas permeability in damaged materials was several orders of magnitude higher than that in pristine materials. In-situ measurements of gas permeability and density were proved to be possible at higher temperatures.

  2. Precision short-pulse damage test station utilizing optical parametric chirped-pulse amplification

    SciTech Connect

    Jovanovic, I; Brown, C; Wattellier, B; Nielsen, N; Molander, W; Stuart, B; Pennington, D; Barty, C J

    2004-03-22

    The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression, due to their high efficiency and high damage threshold for picosecond pulses. The peak power of HEPW lasers will be determined by the aperture and damage threshold of the final dielectric grating in the pulse compressor and final focusing optics. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. Our damage test station is based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier (OPCPA) operating at 1053 nm at a repetition rate of 10 Hz. We present the design of our OPCPA system pumped by a commercial Q-switched pump laser and the results of the full system characterization. Initial short-pulse damage experiments in the far field using our system have been performed.

  3. Damage Characterization in Copper Deformed Under Hydrostatic Stress - Experimental Analysis

    NASA Astrophysics Data System (ADS)

    Flater, Philip; de Angelis, Robert; House, Joel

    2005-07-01

    This paper presents an experimental investigation to characterize the effect of damage created by hydrostatic tensile loading on the properties of copper. Three metallurgical conditions were investigated: half-hard OFHC copper in the as worked, annealed 2hr at 400°C (˜40 micron grain diameter), and annealed 2hr at 800^ oC (˜80 micron grain diameter). Quasi-static testing of each condition included uniaxial tension and compression, round notched bar tension, and flat tapered bar tension. Dynamic properties under uniaxial tension and compression were tested using a split-Hopkinson pressure bar. Damaged structures were created employing Taylor impact tests and rod-on-rod impact experiments. The resulting damage was characterized employing optical and scanning electron microscopy. Quasi-static compression samples machined from recovered samples were tested to determine the influence of damage on deformation behavior and elastic modulus. The compression experimental results will be discussed in relationship to the starting microstructure and subsequent damaged material.

  4. Analysis of optics damage growth at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Liao, Z. M.; Nostrand, M.; Whitman, P.; Bude, J.

    2015-11-01

    Optics damage growth modeling and analysis at the National Ignition Facility (NIF) has been performed on fused silica. We will show the results of single shot growth comparisons, damage site lifetime comparisons as well as growth metrics for each individual NIF beamline. These results help validate the consistency of the damage growth models and allow us to have confidence in our strategic planning in regards to projected optic usage.

  5. Marine Optical Characterizations

    NASA Technical Reports Server (NTRS)

    Clark, Dennis K.

    1996-01-01

    The team's major emphasis during this reporting period has been focused on the completion of the operational versions of the Marine Optical Buoys (MOBY's). Other work areas consisted of designing and testing bio-optical instrumentation, evaluating several of the SeaWiFS bio-optical protocols, processing data collected during field experiments, and reprocessing several of the Marine Optical Characteristics Experiment (MOCE) 2 and 3 bio-optical data sets. The team conducted one trip to the operations site in Honolulu, Hawaii, making necessary preparations for future field experiments. Part of the team also traveled to Moss Landing Marine Laboratories, Salinas, CA, and to American Holographic Co. Fitchburg MA, to assist with the fabrication of the next generation Marine Optical Buoys. Technical memoranda are being written to address the remote sensing reflectance, and instrument self-shading protocols. During the Ocean Color 96 meeting discussions with the Spanish on acquiring research vessel support during the MODIS validation period were conducted. A proposal will be generated towards this purpose for an experiment to be conducted off the North African coast during the summer of 1999.

  6. Laser induced damage in optical materials: tenth ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1979-07-01

    The tenth annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 12-14 September 1978. 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, and the Office of Naval Research. About 175 scientists attended, including representatives of the United Kingdom, France, Canada, Japan, West Germany, and the Soviet Union. The symposium was divided into sessions concerning the measurement of absorption characteristics, bulk material properties, mirrors and surfaces, thin film damage, coating materials and design, and breakdown phenomena. As in previous years, the emphasis of the papers presented was directed toward new frontiers and new developments. Particular emphasis was given to materials for use 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. The scaling of damage thresholds with pulse duration, focal area, and wavelength was also discussed. In commemoration of the tenth symposium in this series, a number of comprehensive review papers were presented to assess the state of the art in various facets of laser induced damage in optical materials. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons. The eleventh annual symposium is scheduled for 30-31 October 1979 at the National Bureau of Standards, Boulder, Colorado. PMID:20212622

  7. Optic probe for semiconductor characterization

    DOEpatents

    Sopori, Bhushan L.; Hambarian, Artak

    2008-09-02

    Described herein is an optical probe (120) for use in characterizing surface defects in wafers, such as semiconductor wafers. The optical probe (120) detects laser light reflected from the surface (124) of the wafer (106) within various ranges of angles. Characteristics of defects in the surface (124) of the wafer (106) are determined based on the amount of reflected laser light detected in each of the ranges of angles. Additionally, a wafer characterization system (100) is described that includes the described optical probe (120).

  8. Dynamic Optical Investigations of Hypervelocity Impact Damage

    NASA Astrophysics Data System (ADS)

    Lamberson, Leslie Elise

    One of the prominent threats in the endeavor to develop next-generation space assets is the risk of space debris impact in earth's orbit and micrometeoroid impact damage in near-earth orbit and deep space. To date, there is no study available which concentrates on the analysis of dynamic crack growth from hypervelocity impacts on such structures, resulting in their eventual catastrophic degradation. Experiments conducted using a unique two-stage light-gas gun facility have examined the in situ dynamic fracture of brittle polymers subjected to this high-energy-density event. Optical techniques of caustics and photoelasticity, combined with high-speed photography up to 100 million frames per second, analyze crack growth behavior of Mylar and Homalite 100 thin plates after impact by a 1.8 mm diameter nylon 6-6 right cylindrical slug at velocities ranging from 3 to 7 km/s (7000--15500 mph). Crack speeds in both polymers averaged between 0.2 and 0.47 cR, the Rayleigh wave speed (450--1000 mph). Shadow spots and surrounding caustics reveal time histories of the dynamic stress intensity factor, as well as the energy release rate ahead of the mode-I, or opening, crack tips. Results indicate that even under extreme impact conditions of out of-plane loading, highly localized heating, and energetic impact phenomena involving plasma formation and ejecta, the dynamic fracture process occurs during a deformation regime dominated by in-plane loading. These findings imply that the reliability of impacted, thin-walled, plate and shell space structures, idealized by the experimental configuration investigated, can be predicted by the well defined principles of classical dynamic fracture mechanics.

  9. Final optics damage inspection (FODI) for the National Ignition Facility

    SciTech Connect

    Conder, A; Alger, T; Azevedo, S; Chang, J; Glenn, S; Kegelmeyer, L; Liebman, J; Spaeth, M; Whitman, P

    2007-10-23

    The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) will routinely fire high energy shots (approaching 10 kJ per beamline) through the final optics, located on the target chamber. After a high fluence shot, exceeding 4J/cm2 at 351 nm wavelength, the final optics will be inspected for laser-induced damage. The FODI (Final Optics Damage Inspection) system has been developed for this purpose, with requirements to detect laser-induced damage initiation and to track and size it's the growth to the point at which the optic is removed and the site mitigated. The FODI system is the 'corner stone' of the NIF optic recycle strategy. We will describe the FODI system and discuss the challenges to make optics inspection a routine part of NIF operations.

  10. Final optics damage inspection (FODI) for the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Conder, Alan; Chang, Jim; Kegelmeyer, Laura; Spaeth, Mary; Whitman, Pam

    2010-08-01

    The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) routinely fires high energy shots (> 6 kJ per beamline) through the final optics, located on the target chamber. After a high fluence shot, exceeding 4J/cm2 at 351 nm wavelength, the final optics are inspected for laser-induced damage. The FODI (Final Optics Damage Inspection) system has been developed for this purpose, with requirements to detect laser-induced damage initiation and to track and size it's growth to the point at which the optic is removed and the site mitigated. The FODI system is the "corner stone" of the NIF optic recycle strategy. We will describe the FODI system and discuss the challenges to make optics inspection a routine part of NIF operations.

  11. Final optics damage inspection (FODI) for the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Conder, Alan; Alger, Terry; Azevedo, Stephen; Chang, Jim; Glenn, Steven; Kegelmeyer, Laura; Liebman, Judith; Spaeth, Mary; Whitman, Pam

    2008-01-01

    The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) will routinely fire high energy shots (approaching 10 kJ per beamline) through the final optics, located on the target chamber. After a high fluence shot, exceeding 4J/cm2 at 351 nm wavelength, the final optics will be inspected for laser-induced damage. The FODI (Final Optics Damage Inspection) system has been developed for this purpose, with requirements to detect laser-induced damage initiation and to track and size it's the growth to the point at which the optic is removed and the site mitigated. The FODI system is the "corner stone" of the NIF optic recycle strategy. We will describe the FODI system and discuss the challenges to make optics inspection a routine part of NIF operations.

  12. Laser induced damage in optical materials: eleventh ASTM symposium.

    PubMed

    Bennett, H E; Glass, A J; Guenther, A H; Newnam, B

    1980-07-15

    The eleventh Symposium on Optical Materials for High-Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 30-31 October 1979. 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 Projects Agency, the Department of Energy, and the Office of Naval Research. About 150 scientists attended the symposium, including representatives of the United Kingdom, France, Canada, Japan, West Germany, and Denmark. The symposium was divided into sessions concerning transparent optical materials and the measurement of their properties, mirrors and surfaces, thin film characteristics, thin film damage, considerations for high-power systems, and finally theory and breakdown. 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. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Alexander J. Glass of the Lawrence Livermore Laboratory, Arthur H. Guenther of the Air Force Weapons Laboratory, and Brian E. Newnam of the Los Alamos Scientific Laboratory were cochairpersons. The twelfth annual symposium is scheduled for 30 September-1 October 1980 at the National Bureau of Standards, Boulder, Colorado. PMID:20234423

  13. Predicting threshold and location of laser damage on optical surfaces

    DOEpatents

    Siekhaus, Wigbert

    1987-01-01

    An apparatus useful in the prediction of the damage threshold of various optical devices, the location of weak spots on such devices and the location, identification, and elimination of optical surface impurities comprising, a focused and pulsed laser, an photo electric detector/imaging means, and a timer. The weak spots emit photoelectrons when subjected to laser intensities that are less than the intensity actually required to produce the damage. The weak spots may be eliminated by sustained exposure to the laser beam.

  14. Marine optical characterizations

    NASA Technical Reports Server (NTRS)

    Clark, Dennis K.; Ge, Yuntao; Hovey, Phil; King, ED; Stengel, Eric; Yuen, Marilyn; Koval, Larisa

    1995-01-01

    During the past three months, the MOCE Team conducted two field experiments in Mill Creek,Chesapeake Bay, from July 24 to August 4, and at the MOBY operations site at Snug Harbor, Honolulu, Hawaii, from August 15-30, prepared two technical memoranda, and continued MOCE-2 and MOCE-3 data reduction. The primary purposes of the experiments were to test the SeaWiFS 'remote sensing reflectance' protocol, obtain turbid water data for ocean color satellite algorithm development, perform calibration for both Near Infrared (NIR) and Visible Rainbow Spectrometer system, continue assembling the operational Marine Optical Buoy, and to test the MOBY cellular phone communications link at the Lanai mooring site.

  15. Laser induced damage of fused silica polished optics due to a droplet forming organic contaminant.

    PubMed

    Bien-Aimé, Karell; Néauport, Jérome; Tovena-Pecault, Isabelle; Fargin, Evelyne; Labrugère, Christine; Belin, Colette; Couzi, Michel

    2009-04-20

    We report on the effect of organic molecular contamination on single shot laser induced damage density at the wavelength of 351 nm, with a 3 ns pulse length. Specific contamination experiments were made with dioctylphthalate (DOP) in liquid or gaseous phase, on the surface of fused silica polished samples, bare or solgel coated. Systematic laser induced damage was observed only in the case of liquid phase contamination. Different chemical and morphological characterization methods were used to identify and understand the damage process. We demonstrate that the contaminant morphology, rather than its physicochemical nature, can be responsible for the decrease of laser induced damage threshold of optics. PMID:19381171

  16. Seismic damage identification for steel structures using distributed fiber optics.

    PubMed

    Hou, Shuang; Cai, C S; Ou, Jinping

    2009-08-01

    A distributed fiber optic monitoring methodology based on optic time domain reflectometry technology is developed for seismic damage identification of steel structures. Epoxy with a strength closely associated to a specified structure damage state is used for bonding zigzagged configured optic fibers on the surfaces of the structure. Sensing the local deformation of the structure, the epoxy modulates the signal change within the optic fiber in response to the damage state of the structure. A monotonic loading test is conducted on a steel specimen installed with the proposed sensing system using selected epoxy that will crack at the designated strain level, which indicates the damage of the steel structure. Then, using the selected epoxy, a varying degree of cyclic loading amplitudes, which is associated with different damage states, is applied on a second specimen. The test results show that the specimen's damage can be identified by the optic sensors, and its maximum local deformation can be recorded by the sensing system; moreover, the damage evolution can also be identified. PMID:19649054

  17. Optical characterization of frame grabbers

    NASA Astrophysics Data System (ADS)

    Pozo, A. M.; Rubiño, M.

    2013-04-01

    Today, video cameras connected to frame grabbers are used in many applications such as traffic control, surveillance, medical systems or machine vision. In this work, we present an optical characterization of frame grabbers in terms of their spatial-frequency responses. This characterization is based on the modulation transfer function (MTF) determination from speckle patterns using a low-cost experimental setup. We have characterized and compared three different frame grabbers. The three frame grabbers produce an amplification (boost) in the horizontal MTF in different spatial-frequency ranges and having different maximum amplification values.

  18. Optical Characterization of Biological Tissues

    NASA Astrophysics Data System (ADS)

    Barrera, Frederick; Sardar, Dhiraj; Tsin, Andrew

    2008-03-01

    University of Texas at San Antonio, San Antonio, Texas 78249. An in-depth characterization of optical properties of biological tissues has been performed. The wavelength-dependent total diffuse reflection (Rd) and total transmission (Tt) measurements have been taken for individual tissue by using a double-integrating sphere setup. The index of refraction of the tissue will be determined using conventional optical techniques. The Inverse Adding Doubling (IAD) computational method is applied to the measured values of n, Rd, and Tt to calculate the optical absorption and scattering coefficients as well as the scattering anisotropy coefficients of these tissues. The Rd and Tt determined by the IAD method were compared with those generated by the Monte Carlo simulation technique. A thorough comparison of the scattering characteristics of these tissues has been made. Furthermore, a comparison of these optical scattering and absorption coefficients calculated by IAD method were compared to the values determined by the Kubelka-Munk model.

  19. Laser induced damage in optical materials: ninth ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1978-08-01

    The Ninth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 4-6 October 1977. The symposium was 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 (formerly ERDA), and the Office of Naval Research. About 185 scientists attended, including representatives of the United Kingdom, France, Canada, Australia, Union of South Africa, and the Soviet Union. The Symposium was divided into sessions concerning Laser Windows and Materials, Mirrors and Surfaces, Thin Films, Laser Glass and Glass Lasers, and Fundamental Mechanisms. As in previous years, the emphasis of the papers was directed toward new frontiers and new developments. Particular emphasis was given to materials for use 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. The scaling of damage thresholds with pulse duration, focal area, and wavelength were also discussed. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons. The Tenth Annual Symposium is scheduled for 12-14 September 1978 at the National Bureau of Standards, Boulder, Colorado. PMID:20203792

  20. Optical Damage Threshold of Silicon for Ultrafast Infrared Pulses

    SciTech Connect

    Cowan, B.; /SLAC

    2006-09-07

    While silicon has several properties making it an attractive material for structure-based laser-driven acceleration, its optical damage threshold, a key parameter for high-gradient acceleration, has been unknown. Here we present measurements of the optical damage threshold of crystalline silicon for ultrafast pulses in the mid-infrared. The wavelengths tested span a range from the telecommunications band at 1550 nm extending longer toward the two-photon absorption threshold at around 2200 nm. We discuss the prevailing theories of ultrafast optical breakdown, describe the experimental setup and preliminary results, and propose a relevant performance parameter for candidate accelerator structures.

  1. Optical characterization in wide spectral range by a coherent spectrophotometer

    NASA Astrophysics Data System (ADS)

    Sirutkaitis, Valdas; Eckardt, Robert C.; Balachninaite, Ona; Grigonis, Rimantas; Melninkaitis, A.; Rakickas, T.

    2003-11-01

    We report on the development and use of coherent spectrophotometers specialized for the unusual requirements of characterizing nonlinear optical materials and multilayer dielectric coatings used in laser systems. A large dynamic range is required to measure the linear properties of transmission, reflection and absorption and nonlinear properties of laser-induced damage threshold and nonlinear frequency conversion. Optical parametric oscillators generate coherent radiation that is widely tunable with instantaneous powers that can range from milliwatts to megawatts and are well matched to this application. As particular example a laser spectrophotometer based on optical parametric oscillators and a diode-pumped, Q-switched Nd:YAG laser and suitable for optical characterization in the spectral range 420-4500 nm is described. Measurements include reflectance and transmittance, absorption, scattering and laser-induced damage thresholds. Possibilities of a system based on a 130-fs Ti:sapphire laser and optical parametric generators are also discussed.

  2. Low Coherence Optic Source Characterization

    NASA Astrophysics Data System (ADS)

    Flores-Domínguez, C. E.; Ochoa-Valiente, R.; García-Trujillo, L. A.

    2015-01-01

    This work presents the results of characterization of the coherence length of an optic source using interferometric techniques and digital signal processing. Optic sources are not ideal because of random behavior in the emission process and spectral dispersion. Optical coherence is the ability of light to generate interference, either temporal or spatial. In time domain, coherence is expressed by the autocorrelation function. In case of monochromatic laser, it has larger coherence length, in the order of tenths to hundredth of meters, rather than a superluminiscent diode (SLD), which is shorter, in the orders of millimeters. This work presents a method for measuring coherence length using an automated Michelson interferometer and a SLD with central wavelength λ0 = 1302.4 nm and acquisition system.by means of a soundcard in a personal computer.

  3. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D.W.; Bennett, B.L.; Cockroft, N.J.

    1998-09-08

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal. 5 figs.

  4. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D. Wayne; Bennett, Bryan L.; Cockroft, Nigel J.

    1998-01-01

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal.

  5. Transient stimulated Brillouin scattering and damage of optical glass

    SciTech Connect

    Yu, H.; Meng, S.

    1997-01-01

    A theory of the excitation of ultrasound waves arising from photoelastic coupling with light is presented in this article. Using several reasonable approximations, a numerical calculation of the transient stimulated Brillouin scattering process shows that a large amplitude of acoustic wave can be built up during the pulse of pump light, and it may result in damage to optical materials. This model gives a damage threshold value of {approximately}30{endash}50 J/cm{sup 2} when using Gaussian or square nanosecond pulses on optical materials. {copyright} {ital 1997 American Institute of Physics.}

  6. Predicting threshold and location of laser damage on optical surfaces

    DOEpatents

    Siekhaus, W.

    1985-02-04

    Disclosed is an apparatus useful in the prediction of the damage threshold of various optical devices, the location of weak spots on such devices and the location, identification, and elimination of optical surface impurities. The apparatus comprises a focused and pulsed laser, a photo electric detector/imaging means, and a timer. The weak spots emit photoelectrons when subjected to laser intensities that are less than the intensity actually required to produce the damage. The weak spots may be eliminated by sustained exposure to the laser beam.

  7. Proton radiation damage in optical filter glass

    NASA Technical Reports Server (NTRS)

    Grillot, Patrick N.; Rosenberg, William J.

    1989-01-01

    Samples of Schott BG-39 and Hoya CM-500 blue-green filter glass were subjected to proton radiation to determine their acceptability for spaceflight. Initial testing done with 2.7 MeV protons showed negligible change in optical transmittance with doses as high as 5.2 x 10 to the 14th protons per sq cm. Irradiation with protons of energy up to 63 MeV caused a significant reduction in transmittance in the Schott samples at doses of 5.3 x 10 to the 12th protons per sq cm, while negligible change occurred in the Hoya samples.

  8. Integrated optic modulator and splitter damage at 1053nm

    SciTech Connect

    Wilcox, R.B.; Browning, D.F.

    1996-12-31

    We are designing and developing a single mode fiber laser and modulation system for use in an inertial confinement fusion research laser, the National Ignition Facility (NIF). Our fiber and integrated optic oscillator / modulator system generates optical pulses of around 30 nanoseconds duration, at one kilohertz, with up to 500 nanojoules of energy. This is enough to potentially damage some of the single mode fiber and waveguide components. To test these components, we have built a test system using a diode-pumped Nd:YLF laser, producing 10 microjoules in 120 nanoseconds at 500 hertz. This system has been used to test commercial lithium niobate integrated optic modulators, silica-on-silicon waveguide splitters, lens-coupled dichroic mirror splitters, and other fiber optic components. We present results of damage tests and efforts to improve performance.

  9. Large-aperture, high-damage-threshold optics for beamlet

    SciTech Connect

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J.

    1996-06-01

    Beamlet serves as a test bed for the proposed National Ignition Facility (NIF) laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of the previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, the authors discuss the properties and characteristics of the large-aperture optics used on Beamlet.

  10. Optical characterization of beef muscle

    NASA Astrophysics Data System (ADS)

    Yao, Gang; Xia, Jinjun

    2005-11-01

    An objective and reliable method for meat quality measurement will benefit both consumers and meat industry. Among various techniques, optical methods have the advantage of being fast, flexible, inexpensive and nondestructive, which are important characteristics for online quality control. Although there have been great progress in this area, many results are inconsistent and controversial because of the lack of fundamental understanding of in light-meat interactions. Optical measurements on meat tissues are affected by both meat scattering and absorption properties. In the project, a method based on diffuse approximation solution of light transport in tissue was used to derive meat scattering and absorption coefficients. Differentiating muscle scattering properties from absorption properties are important for muscle characterization because they represent distinctly different aspects of muscle physical and chemical components. Our preliminary results showed that scattering coefficients can detect variations in beef steak tenderness. This new technique is promising to be used as an indicator for beef tenderness. However, a more extensive study with larger sample population will be necessary to fully test the capability of using optical scattering for beef tenderness characterization.

  11. Laser induced damage in optical materials: twelfth ASTM symposium.

    PubMed

    Bennett, H E; Glass, A J; Guenther, A H; Newnam, B

    1981-09-01

    The twelfth annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 30 Sept.-l Oct., 1980. The symposium was held under the auspices of ASTM Committee F-l, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Projects Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific research. Over 150 scientists attended the symposium, including representatives of the United Kingdom, France, Japan, 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 papers presented at the symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high power systems. 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. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Alexander J. Glass of the Lawrence Livermore National Laboratory, Arthur H. Guenther of the Air Force Weapons Laboratory, and Brian E. Newnam of the Los Alamos National Laboratory were cochairmen of the symposium. The thirteenth annual symposium is scheduled for 17-18 Nov. 1981 at the National Bureau of Standards, Boulder, Colorado. PMID:20333088

  12. Optical Characterization of Biological Tissues

    NASA Astrophysics Data System (ADS)

    Mimun, L.; Barrera, Frederick; Sardar, Dhiraj; Tsin, Andrew

    2008-03-01

    University of Texas at San Antonio, San Antonio, Texas 78249 An in-depth characterization of the optical properties of biological tissues has been performed. The wavelength-dependent total diffuse reflection (Rd) and total transmission (Tt) measurements have been taken for individual tissues by using a double-integrating sphere setup. The index of refraction of the tissues will be determined using conventional optical techniques. The Kubelka Munk theory is applied to determine the scattering and absorption coefficients of these samples from the measurements of diffuse transmission and reflection. A thorough study of the scattering characteristics of these tissues has been made. *This work was supported in part by the NSF sponsored Center for Biophotonics Science and Technology (CBST) at UC Davis under Cooperative Agreement No. PHY 0120999.

  13. Damage mechanisms avoided or managed for NIF large optics

    DOE PAGESBeta

    Manes, K. R.; Spaeth, M. L.; Adams, J. J.; Bowers, M. W.; Bude, J. D.; Carr, C. W.; Conder, A. D.; DiNicola, J. M. G.; Dixit, S. N.; Feigenbaum, E.; et al

    2016-02-09

    After every other failure mode has been considered, in the end, the high-performance limit of all lasers is set by optical damage. The demands of inertial confinement fusion (ICF) pushed lasers designed as ICF drivers into this limit from their very earliest days. The first ICF lasers were small, and their pulses were short. Their goal was to provide as much power to the target as possible. Typically, they faced damage due to high intensity on their optics. As requests for higher laser energy, longer pulse lengths, and better symmetry appeared, new kinds of damage also emerged, some of themmore » anticipated and others unexpected. This paper will discuss the various types of damage to large optics that had to be considered, avoided to the extent possible, or otherwise managed as the National Ignition Facility (NIF) laser was designed, fabricated, and brought into operation. Furthermore, it has been possible for NIF to meet its requirements because of the experience gained in previous ICF systems and because NIF designers have continued to be able to avoid or manage new damage situations as they have appeared.« less

  14. Laser-induced damage in optical materials: sixteenth ASTM symposium.

    PubMed

    Bennett, H E; Guenther, A H; Milam, D; Newnam, B E

    1987-03-01

    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. PMID:20454228

  15. Modeling of Laser Induced Damage in NIF UV Optics

    SciTech Connect

    Feit, M D; Rubenchik, A M

    2001-02-21

    Controlling damage to nominally transparent optical elements such as lenses, windows and frequency conversion crystals on high power lasers is a continuing technical problem. Scientific understanding of the underlying mechanisms of laser energy absorption, material heating and vaporization and resultant mechanical damage is especially important for UV lasers with large apertures such as NIF. This LDRD project was a single year effort, in coordination with associated experimental projects, to initiate theoretical descriptions of several of the relevant processes. In understanding laser damage, we distinguish between damage initiation and the growth of existent damage upon subsequent laser irradiation. In general, the effect of damage could be ameliorated by either preventing its initiation or by mitigating its growth. The distinction comes about because initiation is generally due to extrinsic factors such as contaminants, which provide a means of local laser energy absorption. Thus, initiation tends to be local and stochastic in nature. On the other hand, the initial damaging event appears to modify the surrounding material in such a way that multiple pulse damage grows more or less regularly. More exactly, three ingredients are necessary for visible laser induced damage. These are adequate laser energy, a mechanism of laser energy absorption and mechanical weakness. For damage growth, the material surrounding a damage site is already mechanically weakened by cracks and probably chemically modified as well. The mechanical damage can also lead to electric field intensification due to interference effects, thus increasing the available laser energy density. In this project, we successfully accounted for the pulselength dependence of damage threshold in bulk DKDP crystals with the hypothesis of small absorbers with a distribution of sizes. We theoretically investigated expected scaling of damage initiation craters both to baseline detailed numerical simulations

  16. Impact damage characterization of composite materials

    NASA Astrophysics Data System (ADS)

    Korkmaz, Yesim

    2002-04-01

    Impact damage in structural composites depends on their material properties, component geometry and a variety of impact parameters and experimental determination of their detailed characteristics requires prohibitively large test matrices. The effects of some of these parameters can be understood through simulation models that complement experimental results. In this dissertation a series of finite element models are developed using MSC/NASTRAN for calculating contact laws and progressive damage (e.g., matrix cracking, delamination and fiber break) in graphite/epoxy laminates subject to low and intermediate velocity impact. The validity of the computational models is supported by theoretical calculations involving idealized cases. The effects of laminate geometry as well as the impact parameters on the nature and degree of damage are studied. The global force-time and displacement-time responses of the laminate during impact are also studied. The results of this research can be used for damage growth prediction in composite structural components subject to impact loads.

  17. Characterizing loss and damage from climate change

    NASA Astrophysics Data System (ADS)

    James, Rachel; Otto, Friederike; Parker, Hannah; Boyd, Emily; Cornforth, Rosalind; Mitchell, Daniel; Allen, Myles

    2014-11-01

    Policymakers are creating mechanisms to help developing countries cope with loss and damage from climate change, but the negotiations are largely neglecting scientific questions about what the impacts of climate change actually are.

  18. GIS characterization of spatially distributed lifeline damage

    USGS Publications Warehouse

    Toprak, Selcuk; O'Rourke, Thomas, D.; Tutuncu, Ilker

    1999-01-01

    This paper describes the visualization of spatially distributed water pipeline damage following an earthquake using geographical information systems (GIS). Pipeline damage is expressed as a repair rate (RR). Repair rate contours are developed with GIS by dividing the study area into grid cells (n ?? n), determining the number of particular pipeline repairs in each grid cell, and dividing the number of repairs by the length of that pipeline in each cell area. The resulting contour plot is a two-dimensional visualization of point source damage. High damage zones are defined herein as areas with an RR value greater than the mean RR for the entire study area of interest. A hyperbolic relationship between visual display of high pipeline damage zones and grid size, n, was developed. The relationship is expressed in terms of two dimensionless parameters, threshold area coverage (TAC) and dimensionless grid size (DGS). The relationship is valid over a wide range of different map scales spanning approximately 1,200 km2 for the largest portion of the Los Angeles water distribution system to 1 km2 for the Marina in San Francisco. This relationship can aid GIS users to get sufficiently refined, but easily visualized, maps of damage patterns.

  19. Damage characterization for particles filled semi-crystalline polymer

    NASA Astrophysics Data System (ADS)

    Lauro, Franck; Balieu, Romain; Bennani, Bruno; Haugou, Gregory; Bourel, Benjamin; Chaari, Fahmi; Matsumoto, Tsukatada; Mottola, Ernesto

    2015-09-01

    Damage evolution and characterization in semi-crystalline polymer filled with particles under various loadings is still a challenge. A specific damage characterization method using Digital Image Correlation is proposed for a wide range of strain rates considering tensile tests with hydraulic jacks as well as Hopkinson's bars. This damage measurement is obtained by using and adapting the SEE method [1] which was developed to characterize the behaviour laws at constant strain rates of polymeric materials in dynamic. To validate the characterization process, various damage measurement techniques are used under quasi-static conditions before to apply the procedure in dynamic. So, the well-known damage characterization by loss of stiffness technique under quasi-static loading is applied to a polypropylene. In addition, an in-situ tensile test, carried out in a microtomograph, is used to observe the cavitation phenomenon in real time. A good correlation is obtained between all these techniques and consequently the proposed technique is supposed suitable for measuring the ductile damage observed in semi-crystalline polymers under dynamic loading. By applying it to the semi-crystalline polymer at moderate and high speed loadings, the damage evolution is measured and it is observed that the damage evolution is not strain rate dependent but the failure strain on the contrary is strain rate dependent.

  20. Correlation of polishing-induced shallow subsurface damages with laser-induced gray haze damages in fused silica optics

    NASA Astrophysics Data System (ADS)

    He, Xiang; Zhao, Heng; Wang, Gang; Zhou, Peifan; Ma, Ping

    2016-08-01

    Laser-induced damage in fused silica optics greatly restricts the performances of laser facilities. Gray haze damage, which is always initiated on ceria polished optics, is one of the most important damage morphologies in fused silica optics. In this paper, the laser-induced gray haze damages of four fused silica samples polished with CeO2, Al2O3, ZrO2, and colloidal silica slurries are investigated. Four samples all present gray haze damages with much different damage densities. Then, the polishing-induced contaminant and subsurface damages in four samples are analyzed. The results reveal that the gray haze damages could be initiated on the samples without Ce contaminant and are inclined to show a tight correlation with the shallow subsurface damages.

  1. Impurity-doped optical shock, detonation and damage location sensor

    DOEpatents

    Weiss, J.D.

    1995-02-07

    A shock, detonation, and damage location sensor providing continuous fiber-optic means of measuring shock speed and damage location, and could be designed through proper cabling to have virtually any desired crush pressure. The sensor has one or a plurality of parallel multimode optical fibers, or a singlemode fiber core, surrounded by an elongated cladding, doped along their entire length with impurities to fluoresce in response to light at a different wavelength entering one end of the fiber(s). The length of a fiber would be continuously shorted as it is progressively destroyed by a shock wave traveling parallel to its axis. The resulting backscattered and shifted light would eventually enter a detector and be converted into a proportional electrical signals which would be evaluated to determine shock velocity and damage location. The corresponding reduction in output, because of the shortening of the optical fibers, is used as it is received to determine the velocity and position of the shock front as a function of time. As a damage location sensor the sensor fiber cracks along with the structure to which it is mounted. The size of the resulting drop in detector output is indicative of the location of the crack. 8 figs.

  2. Impurity-doped optical shock, detonation and damage location sensor

    DOEpatents

    Weiss, Jonathan D.

    1995-01-01

    A shock, detonation, and damage location sensor providing continuous fiber-optic means of measuring shock speed and damage location, and could be designed through proper cabling to have virtually any desired crush pressure. The sensor has one or a plurality of parallel multimode optical fibers, or a singlemode fiber core, surrounded by an elongated cladding, doped along their entire length with impurities to fluoresce in response to light at a different wavelength entering one end of the fiber(s). The length of a fiber would be continuously shorted as it is progressively destroyed by a shock wave traveling parallel to its axis. The resulting backscattered and shifted light would eventually enter a detector and be converted into a proportional electrical signals which would be evaluated to determine shock velocity and damage location. The corresponding reduction in output, because of the shortening of the optical fibers, is used as it is received to determine the velocity and position of the shock front as a function of time. As a damage location sensor the sensor fiber cracks along with the structure to which it is mounted. The size of the resulting drop in detector output is indicative of the location of the crack.

  3. Impact damage detection of curved stiffened composite panels by using wavy embedded small-diameter optical fibers

    NASA Astrophysics Data System (ADS)

    Tsutsui, Hiroaki; Kawamata, Akio; Kimoto, Junichi; Sanda, Tomio; Takeda, Nobuo

    2002-07-01

    It is well known that barely visible damage is often induced in composite structures subjected to our-of-plane impact, and the mechanical properties of the composites decrease markedly. So far, for the significance of the damage monitoring, the impact test of the CFRP laminate plates with embedded small-diameter optical fibers were conducted, and it was found possible to detect impact load and impact damage in real-time by measuring the optical loss and strain response. But the stiffened composite panels, which are the representative structural elements of airplane. Are characterized by different impact damage from that of the composite plates. In this study, single-mode and multi-mode optical fibers are used as a sensor for detecting impact load and impact damage in curved/stiffened composite panels. Those fibers have polyimide coating and about 40 micron in diameter which will have no serious effect on the mechanical properties of composites. Impact test are performed using the panels with wavy embedded optical fibers. The characteristics of impact damage are investigated. The impact load, the strain measured by FBG sensors and the optical intensity of the optical fibers embedded in the composites are monitored as a function of time. And we discuss the relationship between optical response, impact load and impact damage.

  4. Optical transmission scanning for damage quantification in impacted GFRP composites

    NASA Astrophysics Data System (ADS)

    Khomenko, Anton; Karpenko, Oleksii; Koricho, Ermias G.; Haq, Mahmoodul; Cloud, Gary L.; Udpa, Lalita

    2016-04-01

    Glass fiber reinforced polymer (GFRP) composites constitute nearly 90% of the global composites market and are extensively used in aerospace, marine, automotive and construction industries. While their advantages of lightweight and superior mechanical properties are well explored, non-destructive evaluation (NDE) techniques that allow for damage/defect detection and assessment of its extent and severity are not fully developed. Some of the conventional NDE techniques for GFRPs include ultrasonics, X-ray, IR thermography, and a variety of optical techniques. Optical methods, specifically measuring the transmission properties (e.g. ballistic optical imaging) of specimens, provide noninvasive, safe, inexpensive, and compact solutions and are commonly used in biomedical applications. In this work, this technique is adapted for rapid NDE of GFRP composites. In its basic form, the system for optical transmission scanning (OTS) consists of a light source (laser diode), a photo detector and a 2D translation stage. The proposed technique provides high-resolution, rapid and non-contact OT (optical transmittance)-scans, and does not require any coupling. The OTS system was used for inspection of pristine and low-velocity impacted (damaged) GFRP samples. The OT-scans were compared with conventional ultrasonic C-scans and showed excellent agreement but with better resolution. Overall, the work presented lays the groundwork for cost-effective, non-contact, and rapid NDE of GFRP composite structures.

  5. Nondestructive optical characterization of MEMS

    NASA Astrophysics Data System (ADS)

    Pryputniewicz, Ryszard J.

    2013-10-01

    Advances in emerging technology of microelectromechanical systems (MEMS) are one of the most challenging tasks in today's experimental mechanics. More specifically, development of these miniature devices requires sophisticated design, analysis, fabrication, testing, and characterization tools that have multiphysics and multiscale capabilities, especially as MEMS are being developed for use at harsh conditions. In harsh-environment and high-performance guidance applications inertial sensors must be sensitive to low rates of rotation yet survive the high blast loads associated with the initial launch. In this multi-year study a set of tuning fork gyroscopes (TFGs) were subjected to a series of increasing g-loads (culminating at approximately 60,000 g's) with measurements of shape made after each test. High-g-testing was conducted within the large test chamber using a custom fabricated mini powder gun. A custom set of test sample packages were hermetically sealed with glass lids to allow optical inspection of components while preserving the operating (vacuum) environment. Optical and interferometric measurements have been made prior to and after each shock g-loading. The shape of the TFG test articles was measured using optoelectronic laser interferometric microscope (OELIM) methodology. Line traces were extracted from pertinent structures to clearly examine changes in the TFG. Failure of the die was observed in the form of fractures below the chip surface as well as fractures in the glass lid sealing the package.

  6. Damage to the Optic Chiasm in Myelin Oligodendrocyte Glycoprotein–Experimental Autoimmune Encephalomyelitis Mice

    PubMed Central

    Herrera, Sheryl L; Palmer, Vanessa L; Whittaker, Heather; Smith, Blair Cardigan; Kim, Annie; Schellenberg, Angela E; Thiessen, Jonathan D; Buist, Richard; Del Bigio, Marc R; Martin, Melanie

    2014-01-01

    Optic chiasm lesions in myelin oligodendrocyte glycoprotein (MOG)–experimental autoimmune encephalomyelitis (EAE) mice were characterized using magnetic resonance imaging (MRI) and validated using electron microscopy (EM). MR images were collected from 3 days after induction to remission, approximately 20 days after induction. Hematoxylin and eosin, solochrome cyanin–stained sections, and EM images were obtained from the optic chiasms of some mice approximately 4 days after disease onset when their scores were thought to be the highest. T2-weighted imaging and apparent diffusion coefficient map hyperintensities corresponded to abnormalities in the optic chiasms of EAE mice. Mixed inflammation was concentrated at the lateral surface. Degeneration of oligodendrocytes, myelin, and early axonal damage were also apparent. A marked increase in chiasm thickness was observed. T2-weighted and diffusion-weighted MRI can detect abnormalities in the optic chiasms of MOG-EAE mice. MRI is an important method in the study of this model toward understanding optic neuritis. PMID:25520558

  7. Role of HDACs in optic nerve damage-induced nuclear atrophy of retinal ganglion cells.

    PubMed

    Schmitt, Heather M; Schlamp, Cassandra L; Nickells, Robert W

    2016-06-20

    Optic neuropathies are characterized by retinal ganglion cell (RGC) death, resulting in the loss of vision. In glaucoma, the most common optic neuropathy, RGC death is initiated by axonal damage, and can be modeled by inducing acute axonal trauma through procedures such as optic nerve crush (ONC) or optic nerve axotomy. One of the early events of RGC death is nuclear atrophy, and is comprised of RGC-specific gene silencing, histone deacetylation, heterochromatin formation, and nuclear shrinkage. These early events appear to be principally regulated by epigenetic mechanisms involving histone deacetylation. Class I histone deacetylases HDACs 1, 2, and 3 are known to play important roles in the process of early nuclear atrophy in RGCs, and studies using both inhibitors and genetic ablation of Hdacs also reveal a critical role in the cell death process. Select inhibitors, such as those being developed for cancer therapy, may also provide a viable secondary treatment option for optic neuropathies. PMID:26733303

  8. Damage to the optic chiasm in myelin oligodendrocyte glycoprotein-experimental autoimmune encephalomyelitis mice.

    PubMed

    Herrera, Sheryl L; Palmer, Vanessa L; Whittaker, Heather; Smith, Blair Cardigan; Kim, Annie; Schellenberg, Angela E; Thiessen, Jonathan D; Buist, Richard; Del Bigio, Marc R; Martin, Melanie

    2014-01-01

    Optic chiasm lesions in myelin oligodendrocyte glycoprotein (MOG)-experimental autoimmune encephalomyelitis (EAE) mice were characterized using magnetic resonance imaging (MRI) and validated using electron microscopy (EM). MR images were collected from 3 days after induction to remission, approximately 20 days after induction. Hematoxylin and eosin, solochrome cyanin-stained sections, and EM images were obtained from the optic chiasms of some mice approximately 4 days after disease onset when their scores were thought to be the highest. T2-weighted imaging and apparent diffusion coefficient map hyperintensities corresponded to abnormalities in the optic chiasms of EAE mice. Mixed inflammation was concentrated at the lateral surface. Degeneration of oligodendrocytes, myelin, and early axonal damage were also apparent. A marked increase in chiasm thickness was observed. T2-weighted and diffusion-weighted MRI can detect abnormalities in the optic chiasms of MOG-EAE mice. MRI is an important method in the study of this model toward understanding optic neuritis. PMID:25520558

  9. MRF Applications: Measurement of Process-dependent Subsurface Damage in Optical Materials using the MRF Wedge Technique

    SciTech Connect

    Menapace, J A; Davis, P J; Steele, W A; Wong, L L; Suratwala, T I; Miller, P E

    2005-11-02

    Understanding the behavior of fractures and subsurface damage in the processes used during optic fabrication plays a key role in determining the final quality of the optical surface finish. During the early stages of surface preparation, brittle grinding processes induce fractures at or near an optical surface whose range can extend from depths of a few mm to hundreds of mm depending upon the process and tooling being employed. Controlling the occurrence, structure, and propagation of these sites during subsequent grinding and polishing operations is highly desirable if one wishes to obtain high-quality surfaces that are free of such artifacts. Over the past year, our team has made significant strides in developing a diagnostic technique that combines magnetorheological finishing (MRF) and scanning optical microscopy to measure and characterize subsurface damage in optical materials. The technique takes advantage of the unique nature of MRF to polish a prescribed large-area wedge into the optical surface without propagating existing damage or introducing new damage. The polished wedge is then analyzed to quantify subsurface damage as a function of depth from the original surface. Large-area measurement using scanning optical microscopy provides for improved accuracy and reliability over methods such as the COM ball-dimple technique. Examples of the technique's use will be presented that illustrate the behavior of subsurface damage in fused silica that arises during a variety of intermediate optical fabrication process steps.

  10. MRF applications: measurement of process-dependent subsurface damage in optical materials using the MRF wedge technique

    NASA Astrophysics Data System (ADS)

    Menapace, Joseph A.; Davis, Pete J.; Steele, William A.; Wong, Lana L.; Suratwala, Tayyab I.; Miller, Philip E.

    2005-12-01

    Understanding the behavior of fractures and subsurface damage in the processes used during optic fabrication plays a key role in determining the final quality of the optical surface finish. During the early stages of surface preparation, brittle grinding processes induce fractures at or near an optical surface whose range can extend from depths of a few μm to hundreds of μm depending upon the process and tooling being employed. Controlling the occurrence, structure, and propagation of these sites during subsequent grinding and polishing operations is highly desirable if one wishes to obtain high-quality surfaces that are free of such artifacts. Over the past year, our team has made significant strides in developing a diagnostic technique that combines magnetorheological finishing (MRF) and scanning optical microscopy to measure and characterize subsurface damage in optical materials. The technique takes advantage of the unique nature of MRF to polish a prescribed large-area wedge into the optical surface without propagating existing damage or introducing new damage. The polished wedge is then analyzed to quantify subsurface damage as a function of depth from the original surface. Large-area measurement using scanning optical microscopy provides for improved accuracy and reliability over methods such as the COM ball-dimple technique. Examples of the technique's use will be presented that illustrate the behavior of subsurface damage in fused silica that arises during a variety of intermediate optical fabrication process steps.

  11. Characterizing damage in ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Gyekenyesi, Andrew L.; Baker, Christopher; Morscher, Gregory

    2014-04-01

    With the upcoming implementation of ceramic matrix composites (CMCs) within aerospace systems (e.g., aviation turbine engines), an in-depth understanding of the failure process due to mechanical loads is required. This includes developing a basic understanding of the complex, multi-mechanism failure process as well as the associated nondestructive evaluation (NDE) techniques that are capable of recognizing and quantifying the damage. Various NDE techniques have been successfully utilized for assessing the damage state of woven CMCs, in particular, consisting of silicon carbide fibers and silicon carbide matrices (SiC/SiC). The multiple NDE techniques, studied by the authors of this paper, included acousto-ultrasonics, modal acoustic emissions, electrical resistance, impedance based structural health monitoring, pulsed thermography as well as thermoelastic stress analysis. The observed damage within the composites was introduced using multiple experimental tactics including uniaxial tensile tests, creep tests, and most recently, ballistic impact. This paper offers a brief review and summary of results for each of the applied NDE tools.

  12. Damage precursor measurements on UV-optical coatings

    SciTech Connect

    Ettrich, K.; Blaschke, H.; Welsch, E.

    1995-12-31

    For application in UV thin film optics the thermal contribution to the laser-induced optical breakdown was investigated utilizing time-resolved photothermal probe beam deflection (MIRAGE) technique. The potentiality of this method for the determination of both the subdamage range and the onset of single-shot-damage of Al{sub 2}O{sub 3}/SiO{sub 2} and LaF{sub 3}/MgF{sub 2} high-reflective coatings by using the thermal branch of the MIRAGE technique could be demonstrated. Examining the dielectric mirrors by 248 nm KrF laser irradiation, distinct damage precursor features were found. Thus, the physical origin of the UV pulsed radiation breakdown in HR coatings can be elucidated.

  13. Continued advancement of laser damage resistant optically functional microstructures

    NASA Astrophysics Data System (ADS)

    Hobbs, Douglas S.; MacLeod, Bruce D.; Sabatino, Ernest

    2012-11-01

    Micro- and nano-structured optically functional surface textures continue to exhibit higher performance and longer term survivability than thin-film coatings for an increasing number of materials used within high energy laser (HEL) systems. Anti-reflection (AR) microstructures (ARMs) produce a graded refractive index yielding high transmission over wide spectral ranges along with a chemical, mechanical and laser damage resistance inherited from the bulk optic material. In this study, ARMs were fabricated in the relevant HEL materials sapphire, neodymium-doped YAG, fused silica, BK7 glass, and the magnesium aluminate known as SPINEL. Standardized pulsed laser induced damage threshold (LiDT) measurements were made using commercial testing services to directly compare the damage resistance of ARMs-treated optics to uncoated and thin-film-AR-coated (TFARC) optics at wavelengths of 532nm, 694nm, 800nm, 1064nm, and 1538nm. As found with prior work, the LiDT of ARMs etched in fused silica was typically in the range of 35 J/cm2 at a wavelength of 1064nm and a pulse width of 10ns, a level that is comparable to uncoated samples and 3.5 times greater than the level specified by six prominent TFARC providers. The Army Research Laboratory measured the pulsed LiDT at 532nm (10ns) of ARMs in fused silica to be up to 5 times the level of the ion beam sputtered TFARC previously employed in their HEL system, and 2 times higher than a low performance single layer MgF2 TFARC. This result was repeated and expanded using a commercial LiDT testing service for ARMs in two types of fused silica and for Schott N-BK7 glass. An average damage threshold of 26.5 J/cm2 was recorded for the ARMs-treated glass materials, a level 4 times higher than the commercial IBS TFARCs tested.

  14. Characterization of damage modes in impacted thermoset and thermoplastic composites

    NASA Technical Reports Server (NTRS)

    Srinivasan, K.; Jackson, W. C.; Smith, B. T.; Hinkley, J. A.

    1992-01-01

    Composite materials remain extremely vulnerable to out-of-plane impact loads, which may lead to severe losses in strength and stiffness. Impact induced damage is often a complex mixture of transverse cracks, delaminations and fiber failures. An experimental investigation was undertaken to quantify damage tolerance and resistance in composite materials impacted using the drop-weight method. Tests were conducted on laminates of several different carbon-fiber composite systems such as epoxies, modified epoxies, and amorphous and semicrystalline thermoplastics. In this paper, impacted composite specimens have been examined using destructive and nondestructive techniques to establish the characteristic damage states. Specifically, optical microscopy, ultrasonic and scanning electron microscopy techniques have been used to identify impact induced damage mechanisms. Damage propagation during post impact compression was also studied.

  15. AFM CHARACTERIZATION OF LASER INDUCED DAMAGE ON CDZNTE CRYSTAL SURFACES

    SciTech Connect

    Hawkins, S; Lucile Teague, L; Martine Duff, M; Eliel Villa-Aleman, E

    2008-06-10

    Semi-conducting CdZnTe (or CZT) crystals can be used in a variety of detector-type applications. CZT shows great promise for use as a gamma radiation spectrometer. However, its performance is adversely affected by point defects, structural and compositional heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), secondary phases and in some cases, damage caused by external forces. One example is damage that occurs during characterization of the surface by a laser during Raman spectroscopy. Even minimal laser power can cause Te enriched areas on the surface to appear. The Raman spectra resulting from measurements at moderate intensity laser power show large increases in peak intensity that is attributed to Te. Atomic Force Microscopy (AFM) was used to characterize the extent of damage to the CZT crystal surface following exposure to the Raman laser. AFM data reveal localized surface damage in the areas exposed to the Raman laser beam. The degree of surface damage to the crystal is dependent on the laser power, with the most observable damage occurring at high laser power. Moreover, intensity increases in the Te peaks of the Raman spectra are observed even at low laser power with little to no visible damage observed by AFM. AFM results also suggest that exposure to the same amount of laser power yields different amounts of surface damage depending on whether the exposed surface is the Te terminating face or the Cd terminating face of CZT.

  16. Laser induced damage in optical materials: 8th ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1977-05-01

    The Eighth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was hosted by the National Bureau of Standards in Boulder, Colorado, from 13 to 15 July 1976. 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 Energy Research and Development Administration, and the Office of Naval Research. About 160 scientists attended the Symposium, including representatives of the United Kingdom, France, Canada, and Brazil. The Symposium was divided into five half-day sessions concerning Bulk Material Properties and Thermal Behavior, Mirrors and Surfaces, Thin Film Properties, Thin Film Damage, and Scaling Laws 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 new materials for use at 10.6 microm in mirror substrates, windo s, and coatings. New techniques in film deposition and advances in diamond-turning of optics were described. The scaling of damage thresholds with pulse duration, focal area, and wavelength were discussed. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons of the Symposium. The Ninth Annual Symposium is scheduled for 4-6 October 1977 at the National Bureau of Standards, Boulder, Colorado. PMID:20168679

  17. Damage monitoring of CFRP retrofit using optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Joshi, Kunal; Breaux Frketic, Jolie; Olawale, David; Dickens, Tarik

    2015-04-01

    With nearly 25% of bridge infrastructure deemed deficient, repair of concrete structures is a critical need. FRP materials as thin laminates or fabrics are appearing to be an ideal alternative to traditional repair technology, because of their high strength to weight ratios and stiffness to weight ratios. In addition, FRP materials offer significant potential for lightweight, high strength, cost-effective and durable retrofit. One drawback of using CFRP retrofitting is its brittle-type failure; caused by its nearly linear elastic nature of the stress-strain behavior. This causes a strength reduction of the retrofitted member, thus the health of the retrofit applied on the structure becomes equally important to sustain the serviceability of the structure. This paper provides a system to monitor damage on the CFRP retrofits through optical fiber sensors which are woven into the structure to provide damage sensing. Precracked reinforced concrete beams were retrofitted using CFRP laminates with the most commonly used FRP application technique. The beams were tested under constant stress to allow the retrofitting to fail while evaluating the performance of the sensing system. Debonding failure modes at a stress of 9 MPa were successfully detected by TL optical fiber sensors in addition to detection during flexural failure. Real-time failure detection of FRP strengthened beams was successfully achieved and the retrofit damage-monitoring scheme aims at providing a tool to reduce the response time and decision making involved in maintenance of deficient structures.

  18. Damage detection in bridges through fiber optic structural health monitoring

    NASA Astrophysics Data System (ADS)

    Doornink, J. D.; Phares, B. M.; Wipf, T. J.; Wood, D. L.

    2006-10-01

    A fiber optic structural health monitoring (SHM) system was developed and deployed by the Iowa State University (ISU) Bridge Engineering Center (BEC) to detect gradual or sudden damage in fracture-critical bridges (FCBs). The SHM system is trained with measured performance data, which are collected by fiber optic strain sensors to identify typical bridge behavior when subjected to ambient traffic loads. Structural responses deviating from the trained behavior are considered to be signs of structural damage or degradation and are identified through analytical procedures similar to control chart analyses used in statistical process control (SPC). The demonstration FCB SHM system was installed on the US Highway 30 bridge near Ames, IA, and utilizes 40 fiber bragg grating (FBG) sensors to continuously monitor the bridge response when subjected to ambient traffic loads. After the data is collected and processed, weekly evaluation reports are developed that summarize the continuous monitoring results. Through use of the evaluation reports, the bridge owner is able to identify and estimate the location and severity of the damage. The information presented herein includes an overview of the SHM components, results from laboratory and field validation testing on the system components, and samples of the reduced and analyzed data.

  19. Full-scale prestress loss monitoring of damaged RC structures using distributed optical fiber sensing technology.

    PubMed

    Lan, Chunguang; Zhou, Zhi; Ou, Jinping

    2012-01-01

    For the safety of prestressed structures, prestress loss is a critical issue that will increase with structural damage, so it is necessary to investigate prestress loss of prestressed structures under different damage scenarios. Unfortunately, to date, no qualified techniques are available due to difficulty for sensors to survive in harsh construction environments of long service life and large span. In this paper, a novel smart steel strand based on the Brillouin optical time domain analysis (BOTDA) sensing technique was designed and manufactured, and then series of tests were used to characterize properties of the smart steel strands. Based on prestress loss principle analysis of damaged structures, laboratory tests of two similar beams with different damages were used to verify the concept of full-scale prestress loss monitoring of damaged reinforced concrete (RC) beams by using the smart steel strands. The prestress losses obtained from the Brillouin sensors are compared with that from conventional sensors, which provided the evolution law of prestress losses of damaged RC beams. The monitoring results from the proposed smart strand can reveal both spatial distribution and time history of prestress losses of damaged RC beams. PMID:22778590

  20. Full-Scale Prestress Loss Monitoring of Damaged RC Structures Using Distributed Optical Fiber Sensing Technology

    PubMed Central

    Lan, Chunguang; Zhou, Zhi; Ou, Jinping

    2012-01-01

    For the safety of prestressed structures, prestress loss is a critical issue that will increase with structural damage, so it is necessary to investigate prestress loss of prestressed structures under different damage scenarios. Unfortunately, to date, no qualified techniques are available due to difficulty for sensors to survive in harsh construction environments of long service life and large span. In this paper, a novel smart steel strand based on the Brillouin optical time domain analysis (BOTDA) sensing technique was designed and manufactured, and then series of tests were used to characterize properties of the smart steel strands. Based on prestress loss principle analysis of damaged structures, laboratory tests of two similar beams with different damages were used to verify the concept of full-scale prestress loss monitoring of damaged reinforced concrete (RC) beams by using the smart steel strands. The prestress losses obtained from the Brillouin sensors are compared with that from conventional sensors, which provided the evolution law of prestress losses of damaged RC beams. The monitoring results from the proposed smart strand can reveal both spatial distribution and time history of prestress losses of damaged RC beams. PMID:22778590

  1. High-resolution 3-D imaging of surface damage sites in fused silica with Optical Coherence Tomography

    SciTech Connect

    Guss, G; Bass, I; Hackel, R; Mailhiot, C; Demos, S G

    2007-10-30

    In this work, we present the first successful demonstration of a non-contact technique to precisely measure the 3D spatial characteristics of laser induced surface damage sites in fused silica for large aperture laser systems by employing Optical Coherence Tomography (OCT). What makes OCT particularly interesting in the characterization of optical materials for large aperture laser systems is that its axial resolution can be maintained with working distances greater than 5 cm, whether viewing through air or through the bulk of thick optics. Specifically, when mitigating surface damage sites against further growth by CO{sub 2} laser evaporation of the damage, it is important to know the depth of subsurface cracks below the damage site. These cracks are typically obscured by the damage rubble when imaged from above the surface. The results to date clearly demonstrate that OCT is a unique and valuable tool for characterizing damage sites before and after the mitigation process. We also demonstrated its utility as an in-situ diagnostic to guide and optimize our process when mitigating surface damage sites on large, high-value optics.

  2. Adhesive Characterization and Progressive Damage Analysis of Bonded Composite Joints

    NASA Technical Reports Server (NTRS)

    Girolamo, Donato; Davila, Carlos G.; Leone, Frank A.; Lin, Shih-Yung

    2014-01-01

    The results of an experimental/numerical campaign aimed to develop progressive damage analysis (PDA) tools for predicting the strength of a composite bonded joint under tensile loads are presented. The PDA is based on continuum damage mechanics (CDM) to account for intralaminar damage, and cohesive laws to account for interlaminar and adhesive damage. The adhesive response is characterized using standard fracture specimens and digital image correlation (DIC). The displacement fields measured by DIC are used to calculate the J-integrals, from which the associated cohesive laws of the structural adhesive can be derived. A finite element model of a sandwich conventional splice joint (CSJ) under tensile loads was developed. The simulations indicate that the model is capable of predicting the interactions of damage modes that lead to the failure of the joint.

  3. In situ CTE measurements and damage detection using optical metrology

    NASA Astrophysics Data System (ADS)

    Rajaram, Satish; Cuadra, Jefferson; Saralaya, Raghav; Bartoli, Ivan; Kontsos, Antonios

    2016-02-01

    This paper presents a methodology to make coefficient of thermal expansion measurements through the combined use of two non-contact and full field optical metrology methods including digital image correlation and infrared thermography. In this context, active Infrared Thermography techniques combined with contact and non-contact deformation measurement methods have already been reported to measure materials’ thermal expansion. In addition, such techniques have been reported to be capable to detect surface and subsurface defects from changes in homogenous heat diffusion due to damage. Based on this knowledge, it is hypothesized in this article that the material response induced by thermal loading and quantified by coefficient of thermal expansion measurements could be further used as an indicator of damage. To validate the hypothesis three measurements were performed. The first established the effectiveness of using deformation and thermal full field data for coefficient of thermal expansion measurements. The second intended to demonstrate the advantage of using such full field data in order to provide site-specific measurements of thermal expansion. Finally damage was a priori induced to a metallic specimen, and the measured variations of local CTE confirmed the potential of using the described approach as a means of damage quantification in materials and structures.

  4. Characterization on Smart Optics Using Ellipsometry

    NASA Technical Reports Server (NTRS)

    Song, Kyo D.

    2002-01-01

    Recently, NASA Langley Research Center developed a smart active optical concept to filter narrow band pass or to control optical intensity. To characterize developed smart optics materials, we have measured thickness and reflection properties of the materials using a WVASE32 ellipsometry. This project allowed us to: (1) prepare the smart optical materials for measurement of thickness and optical properties at NASA Langley Research Center; (2) measure thickness and optical properties of the smart optical materials; (3) evaluate the measured properties in terms of applications for narrow band-pass filters. The outcomes of this research provide optical properties and physical properties of the smart optics on a selected spectral range. The applications of this development were used for field-controlled spectral smart filters.

  5. Optical Damage Threshold of Silicon for Ultrafast Infrared Pulses

    SciTech Connect

    Cowan, Benjamin M.; /Tech-X, Boulder /SLAC

    2007-11-28

    We present measurements of the optical damage threshold of crystalline silicon in air for ultrafast pulses in the near infrared. The wavelengths tested span a range from the telecommunications band at 1550 nm, extending to 2260 nm. We discuss the motivation for the measurements and give theoretical context. We then describe the experimental setup, diagnostics, and procedure. The results show a breakdown threshold of 0.2J/cm{sup 2} at 1550 nm and 1.06 ps FWHM pulse duration, and a weak dependence on wavelength.

  6. Characterization of damage precursor density from laser damage probability measurements with non-Gaussian beams

    NASA Astrophysics Data System (ADS)

    Wagner, F. R.; Melninkaitis, A.; BatavičiutÄ--, G.; Gouldieff, C.; Smalakys, L.; Beaudier, A.; Natoli, J.-Y.

    2015-11-01

    Damage induced by nanosecond laser in optical materials can often be attributed to the presence of laser damage precursor in the material. The presence of these precursors within dielectric optics can be successfully described by so called distributed defect ensembles. The physical parameters of these precursor presence models can be deduced by fitting experimental laser damage probability data. For a degenerate defect ensemble these parameters are the precursor threshold and the precursor density in the sample. To deduce precursor densities correctly it is essential to consider the real shape of laser beam that often deviates from Gaussian or hat-top models. To address these issues we discuss a new fitting procedure that minimizes significant errors in the deduced model parameters using experimental beam profile images. We suggest two methods: Defining a Gaussian replacement beam or using a numerical approximation of the surface over threshold (SOT) of the real beam. Both methods are discussed at the example of a degenerate damage precursor population but apply to any type of damage precursor population.

  7. OCCIMA: Optical Channel Characterization in Maritime Atmospheres

    NASA Astrophysics Data System (ADS)

    Hammel, Steve; Tsintikidis, Dimitri; deGrassie, John; Reinhardt, Colin; McBryde, Kevin; Hallenborg, Eric; Wayne, David; Gibson, Kristofor; Cauble, Galen; Ascencio, Ana; Rudiger, Joshua

    2015-05-01

    The Navy is actively developing diverse optical application areas, including high-energy laser weapons and free- space optical communications, which depend on an accurate and timely knowledge of the state of the atmospheric channel. The Optical Channel Characterization in Maritime Atmospheres (OCCIMA) project is a comprehensive program to coalesce and extend the current capability to characterize the maritime atmosphere for all optical and infrared wavelengths. The program goal is the development of a unified and validated analysis toolbox. The foundational design for this program coordinates the development of sensors, measurement protocols, analytical models, and basic physics necessary to fulfill this goal.

  8. Clean Assembly Practices to Prevent Contamination and Damage to Optics

    SciTech Connect

    Pryatel, J; Gourdin, W H

    2005-12-19

    A key lesson learned from the earliest optics installed in the National Ignition Facility (NIF) was that the traditional approach for maintaining cleanliness, such as the use of cleanrooms and associated garments and protocols, is inadequate. Assembly activities often negate the benefits provided by cleanrooms, and in fact generate contamination with high damage potential. As a result, NIF introduced ''clean assembly protocols'' and related practices to supplement the traditional clean room protocols. These new protocols included ''clean-as-you-go'' activities and regular bright light inspections. Introduction of these new protocols has greatly reduced the particle contamination found on more recently installed optics. In this paper we will describe the contamination mechanisms we have observed and the details of the clean assembly protocols we have successfully introduced to mitigate them.

  9. Photothermal microscopy for studying the role of nano-sized absorbing precursors in laser-induced damage of optical materials

    NASA Astrophysics Data System (ADS)

    Commandré, M.; Natoli, J.-Y.; Gallais, L.

    2008-01-01

    Laser-induced damage in optical components has long been acknowledged as a localized phenomenon linked to the presence of defects. Destructive investigations combined to optical characterizations have led to the conclusion that in high quality components the damage initiators are typically a few nanometers in size and have low densities. The understanding of damage phenomena requires the development of non destructive evaluation techniques with both high spatial resolution and sensitivity to detect these defects. In this context, a High Resolution Photothermal Deflection microscope (HRPD) has been developed and coupled with a damage facility at the same wavelength 1.064 μm. The behavior under irradiation of model defects such as gold inclusions (3 to 250 nm) has been studied. We show how HRPD gives determining information about damage mechanisms.

  10. Shell-NASA Vibration-Based Damage Characterization

    NASA Technical Reports Server (NTRS)

    Rollins, John M.

    2014-01-01

    This article describes collaborative research between Shell International Exploration and Production (IE&P) scientists and ISAG personnel to investigate the feasibility of ultrasonic-based characterization of spacecraft tile damage for in-space inspection applications. The approach was proposed by Shell personnel in a Shell-NASA "speed-matching" session in early 2011 after ISAG personnel described challenges inherent in the inspection of MMOD damage deep within spacecraft thermal protection system (TPS) tiles. The approach leveraged Shell's relevant sensor and analytical expertise. The research addressed the difficulties associated with producing 3D models of MMOD damage cavities under the surface of a TPS tile, given that simple image-based sensing is constrained by line of sight through entry holes that have diameters considerably smaller than the underlying damage cavities. Damage cavity characterization is needed as part of a vehicle inspection and risk reduction capability for long-duration, human-flown space missions. It was hoped that cavity characterization could be accomplished through the use of ultrasonic techniques that allow for signal penetration through solid material.

  11. Laser damage testing of optical components under cryogenic conditions

    NASA Astrophysics Data System (ADS)

    Oulehla, Jindrich; Pokorný, Pavel; Lazar, Josef

    2012-11-01

    In this contribution we present a technology for deposition and testing of interference coatings for optical components designed to operate in power pulsed lasers. The aim of the technology is to prepare components for high power laser facilities such as ELI (Extreme Light Infrastructure) or HiLASE. ELI is a part of the European plan to build a new generation of large research facilities selected by the European Strategy Forum for Research Infrastructures (ESFRI). These facilities rely on the use of diode pumped solid state lasers (DPSSL). The choice of the material for the lasers' optical components is critical. Some of the most important properties include the ability to be antireflection and high reflection coated to reduce the energy losses and increase the overall efficiency. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. The conducted experiments served as preliminary tests of laser damage threshold measurement methodology that we plan to use in the future. We designed a special apparatus consisting of a vacuum chamber and a cooling system. The samples were placed into the vacuum chamber which was evacuated and then the samples were cooled down to approximately 120K and illuminated by a pulsed laser. Pulse duration was in the nanosecond region. Multiple test sites on the sample's surface were used for different laser pulse energies. We used optical and electron microscopy and spectrophotometer measurements for coating investigation after the conducted experiments.

  12. Characterizing conical refraction optical tweezers.

    PubMed

    McDonald, C; McDougall, C; Rafailov, E; McGloin, D

    2014-12-01

    Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focusing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots, and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focusing on the trap stiffness, and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot, but benefit from rotational control. PMID:25490654

  13. Optical fiber dispersion characterization study

    NASA Technical Reports Server (NTRS)

    Geeslin, A.; Arriad, A.; Riad, S. M.; Padgett, M. E.

    1979-01-01

    The theory, design, and results of optical fiber pulse dispersion measurements are considered. Both the hardware and software required to perform this type of measurement are described. Hardware includes a thermoelectrically cooled injection laser diode source, an 800 GHz gain bandwidth produce avalanche photodiode and an input mode scrambler. Software for a HP 9825 computer includes fast Fourier transform, inverse Fourier transform, and optimal compensation deconvolution. Test set construction details are also included. Test results include data collected on a 1 Km fiber, a 4 Km fiber, a fused spliced, eight 600 meter length fibers concatenated to form 4.8 Km, and up to nine optical connectors.

  14. Optical characterization of contrast agents for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lee, Tin-Man; Toublan, Farah J.; Oldenburg, Amy; Sitafalwalla, Shoeb; Luo, Wei; Marks, Daniel L.; Suslick, Kenneth S.; Boppart, Stephen A.

    2003-07-01

    The use of contrast agents in almost every imaging modality has been known to enhance the sensitivity of detection and improve diagnostic capabilities by site-specifically labeling tissues or cells of interest. The imaging capabilities of Optical Coherence Tomography (OCT) need to be improved in order to detect early neoplastic changes in medicine and tumor biology. We introduce and characterize the optical properties of several types of optical contrast agents in OCT, namely encapsulating microspheres that incorporate materials including melanin, gold, and carbon. Micron-sized microspheres have been fabricated by state-of-the-art sonicating and ultrasound technology. The optical properties of optical contrast agents have been characterized according to their scattering and absorption coefficients and lifetimes using OCT and the oblique incidence reflectometry method. Finally, we demonstrate the use of these optical contrast agents in in vitro mice liver and analyze the contrast improvement from the OCT images. These optical contrast agents have the potential to improve the detection of in vivo pathologies in the future.

  15. Suppression of optical damage at 532 nm in Holmium doped congruent lithium niobate.

    PubMed

    Barnes, Eftihia; O'Connell, Nathan H; Balli, Nicolas R; Pokhrel, Madhab; Movsesyan, Anush; Kokanyan, Edvard; Sardar, Dhiraj K

    2014-10-20

    Optical damage experiments were carried out in a series of Holmium doped congruent lithium niobate (Ho:cLN) crystals as a function of dopant concentration and laser intensity. The light induced beam distortion was recorded with a camera and a detector under the pseudo-Z-scan configuration. At 532 nm, strong suppression of the optical damage was observed for the 0.94 mol. % doped crystal. Increased resistance to optical damage was also observed at 488 nm. The suppression of the optical damage is predominantly attributed to the reduction of the Nb antisites due to the holmium doping. PMID:25401654

  16. Modeling and Characterization of Damage Processes in Metallic Materials

    NASA Technical Reports Server (NTRS)

    Glaessgen, E. H.; Saether, E.; Smith, S. W.; Hochhalter, J. D.; Yamakov, V. I.; Gupta, V.

    2011-01-01

    This paper describes a broad effort that is aimed at understanding the fundamental mechanisms of crack growth and using that understanding as a basis for designing materials and enabling predictions of fracture in materials and structures that have small characteristic dimensions. This area of research, herein referred to as Damage Science, emphasizes the length scale regimes of the nanoscale and the microscale for which analysis and characterization tools are being developed to predict the formation, propagation, and interaction of fundamental damage mechanisms. Examination of nanoscale processes requires atomistic and discrete dislocation plasticity simulations, while microscale processes can be examined using strain gradient plasticity, crystal plasticity and microstructure modeling methods. Concurrent and sequential multiscale modeling methods are being developed to analytically bridge between these length scales. Experimental methods for characterization and quantification of near-crack tip damage are also being developed. This paper focuses on several new methodologies in these areas and their application to understanding damage processes in polycrystalline metals. On-going and potential applications are also discussed.

  17. Optical textures: characterizing spatiotemporal chaos.

    PubMed

    Clerc, Marcel G; González-Cortés, Gregorio; Odent, Vincent; Wilson, Mario

    2016-07-11

    Macroscopic systems subjected to injection and dissipation of energy can exhibit complex spatiotemporal behaviors as result of dissipative self-organization. Here, we report a one- and two-dimensional pattern forming setup, which exhibits a transition from stationary patterns to spatiotemporal chaotic textures, based on a nematic liquid crystal layer with spatially modulated input beam and optical feedback. Using an adequate projection of spatiotemporal diagrams, we determine the largest Lyapunov exponent. Jointly, this exponent and Fourier transform allow us to distinguish between spatiotemporal chaos and amplitude turbulence concepts, which are usually merged. PMID:27410822

  18. AFM CHARACTERIZATION OF RAMAN LASER INDUCED DAMAGE ON CDZNTECRYSTAL SURFACES

    SciTech Connect

    Teague, L.; Duff, M.

    2008-10-07

    High quality CdZnTe (or CZT) crystals have the potential for use in room temperature gamma-ray and X-ray spectrometers. Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. The presence of structural heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SPs) can have an impact on the detector performance. There is considerable need for reliable and reproducible characterization methods for the measurement of crystal quality. With improvements in material characterization and synthesis, these crystals may become suitable for widespread use in gamma radiation detection. Characterization techniques currently utilized to test for quality and/or to predict performance of the crystal as a gamma-ray detector include infrared (IR) transmission imaging, synchrotron X-ray topography, photoluminescence spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. In some cases, damage caused by characterization methods can have deleterious effects on the crystal performance. The availability of non-destructive analysis techniques is essential to validate a crystal's quality and its ability to be used for either qualitative or quantitative gamma-ray or X-ray detection. The work presented herein discusses the damage that occurs during characterization of the CZT surface by a laser during Raman spectroscopy, even at minimal laser powers. Previous Raman studies have shown that the localized annealing from tightly focused, low powered lasers results in areas of higher Te concentration on the CZT surface. This type of laser damage on the surface resulted in decreased detector performance which was most likely due to increased leakage current caused by areas of higher Te concentration. In this study

  19. Laser-Induced Damage Threshold and Certification Procedures for Optical Materials

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This document provides instructions for performing laser-induced-damage-threshold tests and pass-fail certification tests on optical materials used in pulsed-laser systems. The optical materials to which these procedures apply include coated and uncoated optical substrates, laser crystals, Q-switches, polarizers, and other optical components employed in pulsed-laser systems.

  20. Ovarian tissue characterization using bulk optical properties

    NASA Astrophysics Data System (ADS)

    Tavakoli, B.; Xu, Y.; Zhu, Q.

    2013-03-01

    Ovarian cancer, the deadliest of all gynecologic cancers, is not often found in its early stages due to few symptoms and no reliable screening test. Optical imaging has a great potential to improve the ovarian cancer detection and diagnosis. In this study we have characterized the bulk optical properties of 26 ex-vivo human ovaries using a Diffuse Optical Tomography system. The quantitative values indicated that, in the postmenopausal group, malignant ovaries showed significantly lower scattering coefficient than normal ones. The scattering parameter is largely related to the collagen content that has shown a strong correlation with the cancer development.

  1. Characterization of magneto-optical media

    NASA Technical Reports Server (NTRS)

    Hajjar, Roger A.; Wu, Te-Ho; Mansuripur, M.

    1991-01-01

    Amorphous rare earth-transition metal (RE-TM) alloys and compositionally modulated TM/TM films were characterized in terms of their magnetic, magneto-optic, and galvanomagnetic properties. The loop tracer, vibrating sample magnetometer (VSM), and Rutherford Backscattering (RBS) facility were used to characterize and analyze the various properties of these magneto-optical storage media. Kerr effect, ellipticity, coercivity, and anisotropy at various temperatures, magnetoresistance, and resistivity are among the properties measured in Co/Pt films, Co/Pd films, and TbFeCo films.

  2. Early-state damage detection, characterization, and evolution using high-resolution computed tomography

    NASA Astrophysics Data System (ADS)

    Grandin, Robert John

    Safely using materials in high performance applications requires adequately understanding the mechanisms which control the nucleation and evolution of damage. Most of a material's operational life is spent in a state with noncritical damage, and, for example in metals only a small portion of its life falls within the classical Paris Law regime of crack growth. Developing proper structural health and prognosis models requires understanding the behavior of damage in these early stages within the material's life, and this early-stage damage occurs on length scales at which the material may be considered "granular'' in the sense that the discrete regions which comprise the whole are large enough to require special consideration. Material performance depends upon the characteristics of the granules themselves as well as the interfaces between granules. As a result, properly studying early-stage damage in complex, granular materials requires a means to characterize changes in the granules and interfaces. The granular-scale can range from tenths of microns in ceramics, to single microns in fiber-reinforced composites, to tens of millimeters in concrete. The difficulty of direct-study is often overcome by exhaustive testing of macro-scale damage caused by gross material loads and abuse. Such testing, for example optical or electron microscopy, destructive and further, is costly when used to study the evolution of damage within a material and often limits the study to a few snapshots. New developments in high-resolution computed tomography (HRCT) provide the necessary spatial resolution to directly image the granule length-scale of many materials. Successful application of HRCT with fiber-reinforced composites, however, requires extending the HRCT performance beyond current limits. This dissertation will discuss improvements made in the field of CT reconstruction which enable resolutions to be pushed to the point of being able to image the fiber-scale damage structures and

  3. Apparatus and method for characterizing ultrafast polarization varying optical pulses

    DOEpatents

    Smirl, Arthur; Trebino, Rick P.

    1999-08-10

    Practical techniques are described for characterizing ultrafast potentially ultraweak, ultrashort optical pulses. The techniques are particularly suited to the measurement of signals from nonlinear optical materials characterization experiments, whose signals are generally too weak for full characterization using conventional techniques.

  4. Localized planarization of optical damage using laser-based chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Matthews, Manyalibo J.; Elhadj, Selim; Guss, Gabe M.; Sridharan, Arun; Nielsen, Norman D.; Yoo, Jae-Hyuck; Lee, Daeho; Grigoropoulos, Costas

    2013-11-01

    We present a method to repair damaged optics using laser-based chemical vapor deposition (L-CVD). A CO2 laser is used to heat damaged silica regions and polymerize a gas precursor to form SiO2. Measured deposition rates and morphologies agree well with finite element modeling of a two-phase reaction. Along with optimizing deposition rates and morphology, we also show that the deposited silica is structurally identical to high-grade silica substrate and possesses high UV laser damage thresholds. Successful application of such a method could reduce processing costs, extend optic lifetime, and lead to more damage resistant laser optics used in high power applications.

  5. Terahertz material characterization for nonreciprocal integrated optics

    NASA Astrophysics Data System (ADS)

    Mičica, Martin; Postava, Kamil; Vanwolleghem, Mathias; Horák, Tomáś; Lampin, Jean François; Pištora, Jaromír.

    2015-05-01

    Interest in nonreciprocal terahertz (THz) integrated optics makes necessity to look for new materials active in this region and precisely characterize their optical properties. In this paper we present important aspects of the methods for determination of optical functions in far infrared (FIR) and THz spectral range. The techniques are applied to polyethylene cyclic olefin copolymer (Topas) and hexaferrites (BaFe12O19, SrFe12O19). Topas is promising material in integrated optics for THz radiation, thanks to its low absorption in this region. On the other hand, hexaferrites with its magneto-optic properties can be used for nonreciprocal integrated optic parts and radiation control. Samples were studied by THz time domain spectroscopy (THz-TDS) in spectral range 2 - 100 cm-1 by transmission and reflection. Advantage of presented THz time domain spectroscopy is measurement of the electric field wavefunction, which allows to obtain both the amplitude and phase spectra. In results we provide measured data, processing, and final computed optical properties of Topas and hexaferrites which reveal interesting optical behaviour in THz spectral range.

  6. Characterization of Polarizing Splitter Optics in Extreme Environments

    SciTech Connect

    Tucker, Ryand; Olson, Matthew; Morelli, Gregg

    2013-01-04

    Development of laser systems capable of surviving extreme conditions experienced in military applications requires mounts and components that are able to survive these conditions. The characterization of mounted and/or bonded optical assemblies in harsh environments is critical for the development of laser and optical systems for functionality in these extreme conditions. Customized mounts, bonding assemblies and packaging strategies are utilized to develop and field reliable and robust optical subassemblies. Thin film polarizers operating at 45o and polarizing beam splitter cubes were chosen for initial testing based on past experiences, advancements in optical coating and construction technologies and material properties. Shock, vibration, shear strength, tensile strength and temperature testing are performed on mounted polarizing beam splitter cubes and thin film polarizers from two manufacturers. Previous testing showed that polarizing beam splitter cubes constructed using epoxy would become damaged in the laser resonator. The cubes being tested in this report are constructed using epoxy- free direct optical contact bonding. Thin film polarizers operating at 45o are chosen opposed to Brewster’s angle thin film polarizers to reduce the size and simplify design and construction since an optical wedge is not required. The components and mounts are each environmentally tested beyond the manufacturers’ specifications for shock, vibration, and temperature. Component functionality is monitored during and after the environmental testing. Experimental results from the testing will be discussed as will the impact on future laser resonator designs.

  7. NDE for Characterizing Oxidation Damage in Reinforced Carbon-Carbon

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Rauser, Richard W.; Jacobson, nathan S.; Wincheski, Russell A.; Walker, James L.; Cosgriff, Laura A.

    2009-01-01

    In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter s thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using NDE methods. These specimens were heat treated in air at 1143 and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3 mm. Single-sided NDE methods were used since they might be practical for on-wing inspection, while x-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally-cracked coating and subsequent oxidation damage was also studied with x-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating. The results of that study are briefly reviewed in this article as well. Additionally, a short discussion on the future role of simulation to aid in these studies is provided.

  8. Microstructural characterization of titanium alloys with fretting damage

    NASA Astrophysics Data System (ADS)

    Swalla, Dana Ray

    The primary focus of this work is to understand the role of microstructure in the fretting damage process and develop quantifying measures in fretting damage accumulation in a dual phase Ti-6Al-4V as well as two single phase materials: commercially pure titanium (CP-Ti), which consists of pure alpha-phase titanium, and a near alpha Ti-5Al-2.5Sn. The size and distribution of crystallographic orientation of the alpha-phase, which has an HCP crystalline structure, is significant in fretting crack formation. In particular, the effect of slip displacement amplitude and number of fretting cycles on the evolution of grain morphology, grain orientation, misorientation distribution, composition, and microhardness is investigated. The fretting behavior is also related to the macroscopic monotonic and cyclic deformation response. The research goals are accomplished using state-of-the-art surface characterization tools such as orientation image microscopy (OIM) using electron backscatter diffraction (EBSD), energy dispersive X-ray analysis (EDX) and nanoindentation. This study is the first of its kind to use OIM to characterize fretting damage and also makes contributions to the body of knowledge about deformation mechanisms in titanium alloys. The results provide a foundation for developing and validating computational crystal plasticity models and their application to fretting and sliding contact problems. New fretting assessment measures have also been identified and have application for components that suffer from fretting wear and/or fatigue related failures.

  9. Optical characterization of ultrabright LEDs

    SciTech Connect

    Benavides, Juan Manuel; Webb, Robert H

    2005-07-01

    Ultrabright light emitting diodes (LEDs) are a new light source for visual psychophysics and microscopy. The new LEDs are intended primarily for room and exterior illumination, and the manufacturers' specifications are adequate for that. However, we use them as light sources in situations where a more complete characterization may be useful. For one set of LEDs we have measured the radiometric intensity and its distribution in space and wavelength, and we have tested for interactions of these variables and their dependence on driver configuration. We describe techniques for making these measurements and give a link to a simple calculator for converting among radiometric and photometric measures, as well as an evaluation of the safety considerations these very bright sources demand.

  10. Characterization of passive polymer optical waveguides

    NASA Astrophysics Data System (ADS)

    Joehnck, Matthias; Kalveram, Stefan; Lehmacher, Stefan; Pompe, Guido; Rudolph, Stefan; Neyer, Andreas; Hofstraat, Johannes W.

    1999-05-01

    The characterization of monomode passive polymer optical devices fabricated according to the POPCORN technology by methods originated from electron, ion and optical spectroscopy is summarized. Impacts of observed waveguide perturbations on the optical characteristics of the waveguide are evaluated. In the POPCORN approach optical components for telecommunication applications are fabricated by photo-curing of liquid halogenated (meth)acrylates which have been applied on moulded thermoplastic substrates. For tuning of waveguide material refractive indices with respect to the substrate refractive index frequently comonomer mixtures are used. The polymerization characteristics, especially the polymerization kinetics of individual monomers, determine the formation of copolymers. Therefore the unsaturation as function of UV-illumination time in the formation of halogenated homo- and copolymers has been examined. From different suitable copolymer system, after characterization of their glass transition temperatures, their curing behavior and their refractive indices as function of the monomer ratios, monomode waveguides applying PMMA substrates have been fabricated. To examine the materials composition also in the 6 X 6 micrometers 2 waveguides they have been visualized by transmission electron microscopy. With this method e.g. segregation phenomena could be observed in the waveguide cross section characterization as well. The optical losses in monomode waveguides caused by segregation and other materials induce defects like micro bubbles formed as a result of shrinkage have been quantized by return loss measurements. Defects causing scattering could be observed by convocal laser scanning microscopy and by conventional light microscopy.

  11. Reduction of damage initiation density in fused silica optics via UV laser conditioning

    DOEpatents

    Peterson, John E.; Maricle, Stephen M.; Brusasco, Raymond M.; Penetrante, Bernardino M.

    2004-03-16

    The present invention provides a method for reducing the density of sites on the surface of fused silica optics that are prone to the initiation of laser-induced damage, resulting in optics which have far fewer catastrophic defects and are better capable of resisting optical deterioration upon exposure for a long period of time to a high-power laser beam having a wavelength of about 360 nm or less. The initiation of laser-induced damage is reduced by conditioning the optic at low fluences below levels that normally lead to catastrophic growth of damage. When the optic is then irradiated at its high fluence design limit, the concentration of catastrophic damage sites that form on the surface of the optic is greatly reduced.

  12. Optical Characterization of Metallic Aerosols

    NASA Technical Reports Server (NTRS)

    Sun, Wenbo; Lin, Bing

    2005-01-01

    Airborne metallic particulates from industry and urban sources are highly conducting aerosols. The characterization of these pollutant particles is important for environment monitoring and protection. Because these metallic particulates are highly reflective, their effect on local weather or regional radiation budget may also need to be studied. In this work, light scattering characteristics of these metallic aerosols are studied using exact solutions on perfectly conducting spherical and cylindrical particles. It is found that for perfectly conducting spheres and cylinders, when scattering angle is larger than approx. 90 deg. the linear polarization degree of the scattered light is very close to zero. This light scattering characteristics of perfectly conducting particles is significantly different from that of other aerosols. When these perfectly conducting particles are immersed in an absorbing medium, this light scattering characteristics does not show significant change. Therefore, measuring the linear polarization of scattered lights at backward scattering angles can detect and distinguish metallic particulates from other aerosols. This result provides a great potential of metallic aerosol detection and monitoring for environmental protection.

  13. Electro-Optical Characterization at NREL

    SciTech Connect

    Keyes, B. M.; Dippo, P.; Gedvilas, L.; Johnston, S.; Levi, D.; Metzger, W.; Sopori, B.

    2005-11-01

    One of the core issues in all of the photovoltaics technologies is relating PV device performance to the methods and materials used to produce them. Due to the nature of PV devices, the electronic and optical properties of the materials are key to device performance. The relationship between materials growth and processing, the resulting electro-optical properties, and device performance can be extremely complex and difficult to determine without direct measurement of these properties. Accurate and timely measurement of the electro-optical properties as a function of device processing provides researchers and manufacturers with the knowledge they need to troubleshoot problems and develop the knowledge base necessary for reducing cost, maximizing efficiency, improving reliability, and enhancing manufacturability. The Electro-optical Characterization Team at NREL provides this support for all internal and external projects funded by the PV Program.

  14. Optical damage performance measurements of multilayer dielectric gratings for high energy short pulse lasers

    NASA Astrophysics Data System (ADS)

    Alessi, D.; Carr, C. W.; Negres, R. A.; Hackel, R. P.; Stanion, K. A.; Cross, D. A.; Guss, G.; Nissen, J. D.; Luthi, R.; Fair, J. E.; Britten, J. A.; Haefner, C.

    2015-02-01

    We investigate the laser damage resistance of multilayer dielectric (MLD) diffraction gratings used in the pulse compressors for high energy, high peak power laser systems such as the Advanced Radiographic Capability (ARC) Petawatt laser on the National Ignition Facility (NIF). Our study includes measurements of damage threshold and damage density (ρ(Φ)) with picosecond laser pulses at 1053 nm under relevant operational conditions. Initial results indicate that sparse defects present on the optic surface from the manufacturing processes are responsible for damage initiation at laser fluences below the damage threshold indicated by the standard R-on-1 test methods, as is the case for laser damage with nanosecond pulse durations. As such, this study supports the development of damage density measurements for more accurate predictions on the damage performance of large area optics.

  15. Synthesis and optical characterization of interactive nanosystems

    NASA Astrophysics Data System (ADS)

    Yasmin, Zannatul

    The use of interactive nanosystems (INSs) has unique advantages in sensing applications. Due to their multivalent interactions and stimuli responsiveness i.e. chemical, optical, pH, these adaptive networks can enhance sensing applications. In this work, two distinct INSs are synthesized and the interparticle interactions are probed optically. One of them is the gold nanoparticles based INS in presence of the biomolecule, glutathione. Their unique optical properties and surface binding affinity to thiol-containing glutathione provide an intriguing opportunity to probe bio-systems. The second one is the rare earth oxides/fluorides conjugated with gold nanoparticles based INS which exhibit tunabilty in their multi-wavelength absorbance and emission through coupling with the surface plasmon resonance of gold nanoparticles. The conjugation of these two interactive particles is uniquely synthesized in the presence of the bio-polymer chitosan. This structure displays tunable optical properties. The two novel INSs presented are characterized through their optical signatures using various spectroscopies including a novel approach developed in this work that comprises an all optical photoacoustic spectroscopy (AOPAS). The AOPAS technique is used to determine the unique characteristics of these INSs in aqueous environments by measuring their optical properties in situ. Additionally, we expect the AOPAS technique will provide unique information about nano-bio interfaces and the usefulness of INS as sensors in biological systems without the artifacts limiting the use of current methods, such as fluorescence-based indicators.

  16. Physical limits of semiconductor laser operation: A time-resolved analysis of catastrophic optical damage

    SciTech Connect

    Ziegler, Mathias; Hempel, Martin; Tomm, Jens W.; Elsaesser, Thomas; Larsen, Henning E.; Andersen, Peter E.; Clausen, Soennik; Elliott, Stella N.

    2010-07-12

    The early stages of catastrophic optical damage (COD) in 808 nm emitting diode lasers are mapped by simultaneously monitoring the optical emission with a 1 ns time resolution and deriving the device temperature from thermal images. COD occurs in highly localized damage regions on a 30 to 400 ns time scale which is determined by the accumulation of excess energy absorbed from the optical output. We identify regimes in which COD is avoided by the proper choice of operation parameters.

  17. Application of Golay codes to distributed optical fiber sensor for long-distance oil pipeline leakage and external damage detection

    NASA Astrophysics Data System (ADS)

    Wang, Yannian; Jiang, Zhuangde

    2006-03-01

    A new distributed optical fiber sensor system for long-distance oil pipeline leakage and external damage detection is presented. A smart and sensitive optical fiber cable is buried beneath the soil running along the oil pipeline, which is sensitive to soakage of oil products and mechanical deformation and vibration caused by leaking, tampering, and mechanical impacting. The region of additional attenuation can be located based on the optical time domain reflectometry (OTDR), and the types of external disturbances can be identified according to the characteristics of transmitted optical power. The Golay codes are utilized to improve the range-resolution performance of the OTDR sub-system and offer a method to characterize the transmitted optical power in a wide range of frequency spectrum. Theoretic analysis and simulation experiment have shown that the application of Golay codes can overcome the shortcomings of the prototype based on the conventional single-pulse OTDR.

  18. Combined advanced finishing and UV laser conditioning process for producing damage resistant optics

    DOEpatents

    Menapace, Joseph A.; Peterson, John E.; Penetrante, Bernardino M.; Miller, Philip E.; Parham, Thomas G.; Nichols, Michael A.

    2005-07-26

    A method for reducing the density of sites on the surface of fused silica optics that are prone to the initiation of laser-induced damage, resulting in optics which have far fewer catastrophic defects, and are better capable of resisting optical deterioration upon exposure to a high-power laser beam.

  19. Optical Characterization of Molecular Contaminant Films

    NASA Technical Reports Server (NTRS)

    Visentine, James T.

    2007-01-01

    A semi-empirical method of optical characterization of thin contaminant films on surfaces of optical components has been conceived. The method was originally intended for application to films that become photochemically deposited on such optical components as science windows, lenses, prisms, thinfilm radiators, and glass solar-cell covers aboard spacecraft and satellites in orbit. The method should also be applicable, with suitable modifications, to thin optical films (whether deposited deliberately or formed as contaminants) on optical components used on Earth in the computer microchip laser communications and thin-film industries. The method is expected to satisfy the need for a means of understanding and predicting the reductions in spectral transmittance caused by contaminant films and the consequent deterioration of performances of sensitive optical systems. After further development, this method could become part of the basis of a method of designing optical systems to minimize or compensate for the deleterious effects of contaminant films. In the original outer-space application, these deleterious effects are especially pronounced because after photochemical deposition, the films become darkened by further exposure to solar vacuum ultraviolet (VUV) radiation. In this method, thin contaminant films are theoretically modeled as thin optical films, characterized by known or assumed values of thickness, index of refraction, and absorption coefficient, that form on the outer surfaces of the original antireflection coating on affected optical components. The assumed values are adjusted as needed to make actual spectral transmittance values approximate observed ones as closely as possible and to correlate these values with amounts of VUV radiation to which the optical components have been exposed. In an initial study, the method was applied in correlating measured changes in transmittance of high-purity fused silica photochemically coated with silicone films of

  20. Characterizing microbial diversity and damage in mural paintings.

    PubMed

    Rosado, Tânia; Mirão, José; Candeias, António; Caldeira, Ana Teresa

    2015-02-01

    Mural paintings are some of the oldest and most important cultural expressions of mankind and play an important role for the understanding of societies and civilizations. These cultural assets have high economic and cultural value and therefore their degradation has social and economic impact. The present work presents a novel microanalytical approach to understand the damages caused by microbial communities in mural paintings. This comprises the characterization and identification of microbial diversity and evaluation of damage promoted by their biological activity. Culture-dependent methods and DNA-based approaches like denaturing gradient gel electrophoresis (DGGE) and pyrosequencing are important tools in the isolation and identification of the microbial communities allowing characterization of the biota involved in the biodeterioration phenomena. Raman microspectrometry, infrared spectrometry, and variable pressure scanning electron microscopy coupled with energy-dispersive X-ray spectrometry are also useful tools for evaluation of the presence of microbial contamination and detection of the alteration products resulting from metabolic activity of the microorganisms. This study shows that the degradation status of mural paintings can be correlated to the presence of metabolically active microorganisms. PMID:25358672

  1. Optical characterization of amber from Chiapas, Mexico

    NASA Astrophysics Data System (ADS)

    López-Morales, Guadalupe; Espinosa-Luna, Rafael; Frausto-Reyes, Claudio

    2013-09-01

    An optical characterization of amber samples from México, the Baltic Sea and fake samples is presented, with the aim of discriminate between genuine and fake samples. We sought to identify the physical variables that could serve as the basis for the development of a device whose operation was able to discriminate between samples of genuine and fake amber. The optical refractive index was determined by Spectroscopic Ellipsometry, Abbe refractometry, and by the Brewster angle. The Raman spectra and the fluorescence optical responses were also determined. The results obtained indicate that the refractive index is not a robust variable that can differentiate between genuine amber and a fake sample. On the other hand, the Raman spectra and the fluorescence responses provide information that allows discriminating between both types of samples. For this reason, we used the results obtained by fluorescence as a basis for the design and construction of a prototype simple, reliable, portable, and affordable for authentication of the Mexican amber.

  2. Characterization and simulation of optical sensors.

    PubMed

    Grapinet, M; De Souza, Ph; Smal, J-C; Blosseville, J-M

    2013-11-01

    Numerical simulation is gradually becoming an advantage in active safety. This is why the development of realistic numerical models enabling to substitute real truth by simulated truth is primordial. In order to provide an accurate and cost effective solution to simulate real optical sensor behavior, the software Pro-SiVIC™ has been developed. Simulations with the software Pro-SiVIC™ can replace real tests with optical sensors and hence allow substantial cost and time savings during the development of solutions for driver assistance systems. An optical platform has been developed by IFSTTAR (French Institute of Science and Technology for Transport, Development and Networks) to characterize and validate any existing camera, in order to measure their characteristics as distortion, vignetting, focal length, etc. By comparing real and simulated sensors with this platform, this paper demonstrates that Pro-SiVIC™ accurately reproduces real sensors' behavior. PMID:23735581

  3. Correlating optical damage threshold with intrinsic defect populations in fused silica as a function of heat treatment temperature

    SciTech Connect

    Shen, N.; Matthews, M. J.; Elhadj, S.; Miller, P. E.; Nelson, A. J.; Hamilton, J.

    2013-04-03

    Here, chemical vapor deposition (CVD) is used for the production of fused silica optics in high-power laser applications. However, relatively little is known about the ultraviolet laser damage threshold of CVD films and how they relate to intrinsic defects produced during deposition. We present here a study relating structural and electronic defects in CVD films to 355 nm pulsed-laser damage threshold as a function of post-deposition annealing temperature (THT). Plasma-enhanced CVD based on SiH4/N2O under oxygen-rich conditions was used to deposit 1.5, 3.1 and 6.4 µm thick films on etched SiO2 substrates. Rapid annealing was performed using a scanned CO2 laser beam up to THT ~ 2100 K. The films were then characterized using x-ray photoemission spectroscopy, Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy. A gradual transition in the damage threshold of annealed films was observed for THT values up to 1600 K, correlating with a decrease in non-bridging silanol and oxygen deficient centres. An additional sharp transition in damage threshold also occurs at ~1850 K indicating substrate annealing. Based on our results, a mechanism for damage-related defect annealing is proposed, and the potential of using high-THT CVD SiO2 to mitigate optical damage is also discussed.

  4. Production, Characterization, and Acceleration of Optical Microbunches

    SciTech Connect

    Sears, Christopher M.S.

    2008-06-20

    Optical microbunches with a spacing of 800 nm have been produced for laser acceleration research. The microbunches are produced using a inverse Free-Electron-Laser (IFEL) followed by a dispersive chicane. The microbunched electron beam is characterized by coherent optical transition radiation (COTR) with good agreement to the analytic theory for bunch formation. In a second experiment the bunches are accelerated in a second stage to achieve for the first time direct net acceleration of electrons traveling in a vacuum with visible light. This dissertation presents the theory of microbunch formation and characterization of the microbunches. It also presents the design of the experimental hardware from magnetostatic and particle tracking simulations, to fabrication and measurement of the undulator and chicane magnets. Finally, the dissertation discusses three experiments aimed at demonstrating the IFEL interaction, microbunch production, and the net acceleration of the microbunched beam. At the close of the dissertation, a separate but related research effort on the tight focusing of electrons for coupling into optical scale, Photonic Bandgap, structures is presented. This includes the design and fabrication of a strong focusing permanent magnet quadrupole triplet and an outline of an initial experiment using the triplet to observe wakefields generated by an electron beam passing through an optical scale accelerator.

  5. Characterizing single atom optical dipole traps

    NASA Astrophysics Data System (ADS)

    Shih, Chung-Yu; Gibbons, Michael; Chapman, Michael

    2012-06-01

    Trapping and manipulating individual neutral atoms in far off-resonant traps (FORTs) is a promising approach for quantum information processing. It is important to characterize the trapping environment of the atom and the atomic level shifts due to the trapping fields. Using non-destructive measurement techniques,ootnotetextM. J. Gibbons et al., Phys. Rev. Lett 106, 133002 (2011). we have measured the level dependent AC Stark shifts, trap frequencies, and temperature of single rubidium atoms confined in optical dipole trap.

  6. Enhanced Damage-Resistant Optics for Spaceflight Laser Systems: Workshop findings and recommendations

    NASA Technical Reports Server (NTRS)

    Schulze, Norman; Cimolino, Marc; Guenther, Arthur; Mcminn, Ted; Rainer, Frank; Schmid, Ansgar; Seitel, Steven C.; Soileau, M. J.; Theon, John S.; Walz, William

    1991-01-01

    NASA has defined a program to address critical laser-induced damage issues peculiar to its remote sensing systems. The Langley Research Center (LaRC), with input from the Goddard Space Flight Center (GSFC), has developed a program plan focusing on the certification of optical materials for spaceflight applications and the development of techniques to determine the reliability of such materials under extended laser exposures. This plan involves cooperative efforts between NASA and optics manufacturers to quantify the performance of optical materials for NASA systems and to ensure NASA's continued application of the highest quality optics possible for enhanced system reliability. A review panel was organized to assess NASA's optical damage concerns and to evaluate the effectiveness of the LaRC proposed program plan. This panel consisted of experts in the areas of laser-induced damage, optical coating manufacture, and the design and development of laser systems for space. The panel was presented information on NASA's current and planned laser remote sensing programs, laser-induced damage problems already encountered in NASA systems, and the proposed program plan to address these issues. Additionally, technical presentations were made on the state of the art in damage mechanisms, optical materials testing, and issues of coating manufacture germane to laser damage.

  7. Identification and Elimination of Fluorescent Surface-Damage Precursors on DKDP Optics

    SciTech Connect

    Nostrand, M; Thompson, S; Siekhaus, W; Fluss, M; Hahn, D; Whitman, P; Burnham, A

    2002-11-15

    Fluorescing surface defects that led to damage upon 351-nm laser exposure below 7 J/cm{sup 2} (3-11s) in DKDP optics were reported in these proceedings by this group a year ago. Subsequent laser damage experiments have correlated the density of these damage precursors to single-point diamond finishing conditions. Every diamond-finishing schedule contains brittle-mode cutting and ductile-mode cutting in a taper-down sequence. Finishing experiments have traced the occurrence of these defects to insufficient ductile-mode removal of subsurface damage incurred during prior brittle-mode cutting. Additionally, a correlation between defect fluorescence, laser-induced damage, and defect morphology has been established. Laser-induced damage tests also suggest a correlation between growth method and damage probability. Current experiments indicate that damage-prone defects can be minimized with the proper choice of diamond finishing conditions.

  8. Etching, micro hardness and laser damage threshold studies of a nonlinear optical material L-valine

    NASA Astrophysics Data System (ADS)

    Anbuchezhiyan, M.; Ponnusamy, S.; Muthamizhchelvan, C.; Kanakam, C. C.; Singh, S. P.; Pal, P. K.; Datta, P. K.

    2012-04-01

    A nonlinear optical crystal of L-valine was grown from an aqueous solution containing a small amount of phosphoric acid by the slow evaporation method. The grown crystal was characterized by a single crystal X-ray diffraction to determine the unit cell parameters. The powder X-ray diffraction analysis also confirmed the lattice parameters to be a = 9.6687(7) Å, b = 5.2709(4) Å, c = 12.0371(10) Å and β = 90.805(4)°. The results of the Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES) indicate the presence of a small amount of phosphorus in the grown crystal. The Vickers micro hardness test was performed to study the mechanical strength of the crystals. Chemical etching studies were carried out to analyze the dislocation structure. The laser damaged threshold of the grown crystal was measured to be 11.11 GW/cm2 for 10 ns pulse at 1064 nm, which is higher than that of the standard nonlinear optical crystals like KDP. Second harmonic generation of the grown crystals was also 1.44 times that of KDP.

  9. Laser Damage Testing of Small Optics for the National Ignition Facility

    SciTech Connect

    Chow, R; Runkel, M; Taylor, J R

    2004-01-24

    A damage test procedure was established for optical components that have large incident beam footprints. The procedure was applied on coated samples for a high powered 1053 nm, 3-ns pulse length laser system.

  10. Laser damage testing of small optics for the National Ignition Facility

    SciTech Connect

    Chow, Robert; Runkel, Mike; Taylor, John R

    2005-06-10

    A damage test procedure was established for optical components that have large incident beam footprints. The procedure was applied on coated samples for a high-powered 1053-nm, 3-ns pulse-length laser system.

  11. Research on optical damage to sodium chloride by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Gavasheli, Yu. O.; Komarov, P. S.; Ashitkov, S. I.; Savintsev, A. P.

    2016-06-01

    Thresholds of optical damage to sodium chloride by ultrashort laser pulses with a duration of about 40 fs are determined. Experiments were carried out using a terawatt titanium-sapphire laser device. p-polarized laser radiation at a wavelength of 800 nm fell on the specimen surface at an angle of 60°. Optical damage to the surface was observed when the critical electric field strength attained 94 MV/cm.

  12. Increase of bulk optical damage threshold fluences of KDP crystals by laser irradiation and heat treatment

    DOEpatents

    Swain, J.E.; Stokowski, S.E.; Milam, D.; Kennedy, G.C.; Rainer, F.

    1982-07-07

    The bulk optical damage threshold fluence of potassium dihydrogen phosphate (KDP) crystals is increased by irradiating the crystals with laser pulses of duration 1 to 20 nanoseconds of increasing fluence, below the optical damage threshold fluence for untreated crystals, or by baking the crystals for times of the order of 24 hours at temperatures of 110 to 165/sup 0/C, or by a combination of laser irradiation and baking.

  13. Rugged Packaging for Damage Resistant Inertial Fusion Energy Optics

    SciTech Connect

    Stelmack, Larry

    2003-11-17

    The development of practical fusion energy plants based on inertial confinement with ultraviolet laser beams requires durable, stable final optics that will withstand the harsh fusion environment. Aluminum-coated reflective surfaces are fragile, and require hard overcoatings resistant to contamination, with low optical losses at 248.4 nanometers for use with high-power KrF excimer lasers. This program addresses the definition of requirements for IFE optics protective coatings, the conceptual design of the required deposition equipment according to accepted contamination control principles, and the deposition and evaluation of diamondlike carbon (DLC) test coatings. DLC coatings deposited by Plasma Immersion Ion Processing were adherent and abrasion-resistant, but their UV optical losses must be further reduced to allow their use as protective coatings for IFE final optics. Deposition equipment for coating high-performance IFE final optics must be designed, constructed, and operated with contamination control as a high priority.

  14. Laser-Induced Surface Damage of Optical Materials: Absorption Sources, Initiation, Growth, adn Mitigation

    SciTech Connect

    Papernov, S.; Schmid, A.W.

    2009-04-07

    Susceptibility to laser damage of optical-material surfaces originates from the nature of the surface as a transitional structure between optical-material bulk and its surroundings. As such, it requires technological processing to satisfy figure and roughness requirements and is also permanently subjected to environmental exposure. Consequently, enhanced absorption caused by mechanical structural damage or incorporation and sorption of microscale absorbing defects, even layers of organic materials, is always characteristic for optical-material surfaces. In this review physics of interaction of pulsed-laser radiation with surface imperfections for different types of optical materials (metals, semiconductors, dielectrics, etc.), mechanisms of damage initiation, damage morphology, and damage-site growth under repetitive pulse irradiation are discussed. Consideration is also given here to the surface treatments leading to the reduction of damage initiation sites, such as laser cleaning and conditioning, removal of the surface layers affected by the grinding/polishing process, and mitigation of the damage growth at already formed damage sites.

  15. IMPROVEMENTS IN OPTICAL SORTING OF MOLD-DAMAGED WHEAT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The current study describes the use of three forms of optical measurement of single wheat kernels for screening of Fusarium head blight for eventual incorporation in high-speed optical sorters. Our previous research has demonstrated a sorting efficiency of approximately 50 percent with existing hig...

  16. Adult mice transplanted with embryonic retinal progenitor cells: New approach for repairing damaged optic nerves

    PubMed Central

    Cho, Jang-Hyeon; Mao, Chai-An

    2012-01-01

    Purpose Retinal ganglion cell (RGC) death and optic nerve degeneration are complex processes whose underlying molecular mechanisms are only vaguely understood. Treatments commonly used for optic nerve degeneration have little long-term value and only prolong degeneration. Recent advances in stem cell replacement therapy offer new ways to overcome RGC loss by transferring healthy cells into eyes of afflicted individuals. However, studies on stem cell replacement for optic nerve degeneration are hampered by limitations of the available animal models, especially genetic models. We have developed a mouse model in which RGCs are genetically ablated in adult mice with subsequent degeneration of the optic nerve. In the study reported here, we used this model to determine whether embryonic retinal progenitor cells (RPCs) removed from donor retinas when RPCs are committing to an RGC fate could restore lost RGCs. Methods We used the RGC-depleted model as a host for transplanting donor green fluorescent protein (GFP)–labeled RPCs from embryonic retinas that are maximally expressing Atoh7, a basic helix–loop–helix gene essential for RGC specification. Dissociated GFP-labeled RPCs were characterized in situ by immunolabeling with antibodies against proteins known to be expressed in RPCs at embryonic day (E)14.5. Dissociated retinal cells were injected into the vitreous of one eye of RGC-depleted mice at two to six months of age. The injected and non-injected retinas were analyzed for gene expression using immunolabeling, and the morphology of optic nerves was assessed visually and with histological staining at different times up to four months after injection. Results We demonstrate the successful transfer of embryonic GFP-labeled RPCs into the eyes of RGC-depleted mice. Many transplanted RPCs invaded the ganglion cell layer, but the efficiency of the invasion was low. GFP-labeled cells within the ganglion cell layer expressed genes associated with early and late stages

  17. Optical Measurement Technique for Space Column Characterization

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.; Watson, Judith J.; Burner, Alpheus W.; Phelps, James E.

    2004-01-01

    A simple optical technique for the structural characterization of lightweight space columns is presented. The technique is useful for determining the coefficient of thermal expansion during cool down as well as the induced strain during tension and compression testing. The technique is based upon object-to-image plane scaling and does not require any photogrammetric calibrations or computations. Examples of the measurement of the coefficient of thermal expansion are presented for several lightweight space columns. Examples of strain measured during tension and compression testing are presented along with comparisons to results obtained with Linear Variable Differential Transformer (LVDT) position transducers.

  18. Characterization of Adaptive Optics at Keck Observatory

    SciTech Connect

    van Dam, M A; Macintosh, B A

    2003-07-24

    In this paper, the adaptive optics (AO) system at Keck Observatory is characterized. The AO system is described in detail. The physical parameters of the lenslets, CCD and deformable mirror, the calibration procedures and the signal processing algorithms are explained. Results of sky performance tests are presented: the AO system is shown to deliver images with an average Strehl ratio of up to 0.37 at 1.59 {micro}m using a bright guide star. An error budget that is consistent with the observed image quality is presented.

  19. Optical Material Characterization Using Microdisk Cavities

    NASA Astrophysics Data System (ADS)

    Michael, Christopher P.

    Since Jack Kilby recorded his "Monolithic Idea" for integrated circuits in 1958, microelectronics companies have invested billions of dollars in developing the silicon material system to increase performance and reduce cost. For decades, the industry has made Moore's Law, concerning cost and transistor density, a self-fulfilling prophecy by integrating technical and material requirements vertically down their supply chains and horizontally across competitors in the market. At recent technology nodes, the unacceptable scaling behavior of copper interconnects has become a major design constraint by increasing latency and power consumption---more than 50% of the power consumed by high speed processors is dissipated by intrachip communications. Optical networks at the chip scale are a potential low-power high-bandwidth replacement for conventional global interconnects, but the lack of efficient on-chip optical sources has remained an outstanding problem despite significant advances in silicon optoelectronics. Many material systems are being researched, but there is no ideal candidate even though the established infrastructure strongly favors a CMOS-compatible solution. This thesis focuses on assessing the optical properties of materials using microdisk cavities with the intention to advance processing techniques and materials relevant to silicon photonics. Low-loss microdisk resonators are chosen because of their simplicity and long optical path lengths. A localized photonic probe is developed and characterized that employs a tapered optical-fiber waveguide, and it is utilized in practical demonstrations to test tightly arranged devices and to help prototype new fabrication methods. A case study in AlxGa1-xAs illustrates how the optical scattering and absorption losses can be obtained from the cavity-waveguide transmission. Finally, single-crystal Er2O3 epitaxially grown on silicon is analyzed in detail as a potential CMOS-compatable gain medium due to its high Er3

  20. Damage induced in red blood cells by infrared optical trapping: an evaluation based on elasticity measurements

    NASA Astrophysics Data System (ADS)

    de Oliveira, Marcos A. S.; Moura, Diógenes S.; Fontes, Adriana; de Araujo, Renato E.

    2016-07-01

    We evaluated the damage caused to optically trapped red blood cells (RBCs) after 1 or 2 min of exposure to near-infrared (NIR) laser beams at 785 or 1064 nm. Damage was quantified by measuring cell elasticity using an automatic, real-time, homemade, optical tweezer system. The measurements, performed on a significant number (hundreds) of cells, revealed an overall deformability decrease up to ˜104% after 2 min of light exposure, under 10 mW optical trapping for the 785-nm wavelength. Wavelength dependence of the optical damage is attributed to the light absorption by hemoglobin. The results provided evidence that RBCs have their biomechanical properties affected by NIR radiation. Our findings establish limits for laser applications with RBCs.

  1. Mapping and inspection of damage and artifacts in large-scale optics

    SciTech Connect

    Rainer, F.

    1997-12-22

    We have developed tools for accurately and economically mapping and inspecting damage and artifacts in the bulk as well as on the surface of meter-sized optics intended for use on large-scale lasers such as Beamlet and NIF. Optics are illuminated by white light through the optic edge or externally at grazing incidence using linear fiber- optics arrays. The mega-pixel camera records a digital map of the entire optic with precise addresses of highlighted artifacts. From these coordinated, artifacts are located and digitally recorded with resolution of less than 5 microns using a long-working-distance microscope. Total internal reflection of edge illumination efficiency couples light into the entire optic to inspect for bulk artifacts, such as bubbles, inclusions, edge-cladding flaws and laser- induced damage as well as surface scratches and pits which propagate into the substrate. Surface contamination such as dust, fingerprints, coating flaws, and cleaning flaws are highlighted by external grazing illumination. The procedures permit accurate recording of the evolution of damage after many laser shots as well as correlation of damage from one optic to the next in a laser chain.

  2. Apparatus and method for characterizing ultrafast polarization varying optical pulses

    DOEpatents

    Smirl, A.; Trebino, R.P.

    1999-08-10

    Practical techniques are described for characterizing ultrafast potentially ultraweak, ultrashort optical pulses. The techniques are particularly suited to the measurement of signals from nonlinear optical materials characterization experiments, whose signals are generally too weak for full characterization using conventional techniques. 2 figs.

  3. Optical fiber null coupler sensor for damage detection using ultrasonic

    NASA Astrophysics Data System (ADS)

    Xuan, HaiFeng; Liao, Yanbiao; Zhang, Ming; Lai, Shu R.

    2005-02-01

    A novel optical fiber null coupler (OFNC) sensor based on acousto-optic interaction is developed, which can be used in the structure health monitoring of the medical materials. The OFNC sensors can be response to 10MHz supersonic wave, and their signal-to noise ratio are higher then Piezo Ceramic Transducers(PZT). A kind of Perspex with a 1mm hole is employed as the sample, where the OFNC sensor is glued on, and the reflected signal of ultrasonic wave by the hole is detected .

  4. Methods for Mitigating Growth of Laser-Initiated Surface Damage on DKDP Optics at 351nm

    SciTech Connect

    Hrubesh, L W; Brusasco, R B; Grundler, W; Norton, M A; Donohue, E E; Molander, W A; Thompson, S L; Strodtbeck, S R; Whitman, P K; Shirk, M D; Wegner, P J; Nostrand, M C; Burnham, A K

    2002-10-11

    We report an experimental investigation of mitigating surface damage growth at 351nm for machine-finished DKDP optics. The objective was to determine which methods could be applied to pre-initiated or retrieved-from-service optics, in order to stop further damage growth for large aperture DKDP optics used in high-peak-power laser applications. The test results, and the evaluation thereof, are presented for several mitigation methods applied to DKDP surface damage. The mitigation methods tested were CW-CO{sub 2} laser processing, aqueous wet-etching, short-pulse laser ablation, and micro-machining. We found that micro-machining, using a single crystal diamond tool to completely remove the damage pit, produces the most consistent results to halt the growth of surface damage on DKDP. We obtained the successful mitigation of laser-initiated surface damage sites as large as 0.14mm diameter, for up to 1000 shots at 351nm and fluences in the range of 2 to 13J/cm{sup 2}, {approx} 11ns pulse length. Data obtained to-date indicates that micro-machining is the preferred method to process large-aperture optics.

  5. Reaction ion etching process for improving laser damage resistance of fused silica optical surface.

    PubMed

    Sun, Laixi; Liu, Hongjie; Huang, Jin; Ye, Xin; Xia, Handing; Li, Qingzhi; Jiang, Xiaodong; Wu, Weidong; Yang, Liming; Zheng, Wanguo

    2016-01-11

    Laser induced damage of fused silica optics occurs primarily on optical surface or subsurface resulting from various defects produced during polishing/grinding process. Many new kinds of surface treatment processes are explored to remove or control the defects on fused silica surface. In this study, we report a new application of reaction ion etching (RIE)-based surface treatment process for manufacture of high quality fused silica optics. The influence of RIE processes on laser damage resistance as a function of etching depth and the evolution of typical defects which are associated with laser damage performance were investigated. The results show that the impurity element defects and subsurface damage on the samples surface were efficiently removed and prevented. Pure silica surface with relatively single-stable stoichiometry and low carbon atomic concentration was created during the etching. The laser damage resistance of the etched samples increased dramatically. The increase of roughness and ODC point defect with deeper etching are believed to be the main factors to limit further increase of the damage resistance of fused silica. The study is expected to contribute to the development of fused silica optics with high resistance to laser induced degradation in the future. PMID:26832251

  6. Effect of spatial coherence on damage occurrence in multimode optical fibers.

    PubMed

    Herzog, Amir; Malka, Dror; Zalevsky, Zeev; Ishaaya, Amiel A

    2015-02-01

    We investigate the influence of spatial coherence on damage occurrence in highly multimode optical fibers using ultraviolet (UV) nanosecond pulses, with the aim of delivering high fluence in the UV. In some cases, the optical damage is initiated below the fiber facet damage threshold and takes place along the propagation path; such damage is believed to be caused by local constructive interference, creating "hot spots." In order to reduce the degree of spatial coherence, we used a large-diameter core (1.5 mm) fiber as a mode scrambler. Different lengths of this large core fiber were used to deliver energy to a fiber core with a smaller diameter (0.6 mm), in which the damage occurrence was observed. The experimental results indicate that there is a correlation between the degree of spatial coherence and the occurrence of optical damages, typically observed a few millimeters from the fiber facet. Numerical simulations, based on the beam-propagation method, support the degradation of spatial coherence, due to the excitation of high-order modes. Finally, by degrading the spatial coherence of the beam, we establish a new record by delivering more than 100 mJ via a 1.5 mm core diameter fiber in the UV, corresponding to ∼26 times the critical power for self-focusing. Our work sheds light on the ability to deliver high energies of nanosecond-pulsed UV laser radiation through multimode optical fibers. PMID:25680061

  7. Tools for Predicting Optical Damage on Inertial Confinement Fusion-Class Laser Systems

    SciTech Connect

    Nostrand, M C; Carr, C W; Liao, Z M; Honig, J; Spaeth, M L; Manes, K R; Johnson, M A; Adams, J J; Cross, D A; Negres, R A; Widmayer, C C; Williams, W H; Matthews, M J; Jancaitis, K S; Kegelmeyer, L M

    2010-12-20

    Operating a fusion-class laser to its full potential requires a balance of operating constraints. On the one hand, the total laser energy delivered must be high enough to give an acceptable probability for ignition success. On the other hand, the laser-induced optical damage levels must be low enough to be acceptably handled with the available infrastructure and budget for optics recycle. Our research goal was to develop the models, database structures, and algorithmic tools (which we collectively refer to as ''Loop Tools'') needed to successfully maintain this balance. Predictive models are needed to plan for and manage the impact of shot campaigns from proposal, to shot, and beyond, covering a time span of years. The cost of a proposed shot campaign must be determined from these models, and governance boards must decide, based on predictions, whether to incorporate a given campaign into the facility shot plan based upon available resources. Predictive models are often built on damage ''rules'' derived from small beam damage tests on small optics. These off-line studies vary the energy, pulse-shape and wavelength in order to understand how these variables influence the initiation of damage sites and how initiated damage sites can grow upon further exposure to UV light. It is essential to test these damage ''rules'' on full-scale optics exposed to the complex conditions of an integrated ICF-class laser system. Furthermore, monitoring damage of optics on an ICF-class laser system can help refine damage rules and aid in the development of new rules. Finally, we need to develop the algorithms and data base management tools for implementing these rules in the Loop Tools. The following highlights progress in the development of the loop tools and their implementation.

  8. Improving 351-nm Damage Performance of Large-Aperture Fused Silica and DKDP Optics

    SciTech Connect

    Burnham, A K; Hackel, L; Wegner, P; Parham, T; Hrubesh, L; Penetrante, B; Whitman, P; Demos, S; Menapace, J; Runkel, M; Fluss, M; Feit, M; Key, M; Biesiada, T

    2002-01-07

    A program to identify and eliminate the causes of UV laser-induced damage and growth in fused silica and DKDP has developed methods to extend optics lifetimes for large-aperture, high-peak-power, UV lasers such as the National Ignition Facility (NIF). Issues included polish-related surface damage initiation and growth on fused silica and DKDP, bulk inclusions in fused silica, pinpoint bulk damage in DKDP, and UV-induced surface degradation in fused silica and DKDP in a vacuum. Approaches included an understanding of the mechanism of the damage, incremental improvements to existing fabrication technology, and feasibility studies of non-traditional fabrication technologies. Status and success of these various approaches are reviewed. Improvements were made in reducing surface damage initiation and eliminating growth for fused silica by improved polishing and post-processing steps, and improved analytical techniques are providing insights into mechanisms of DKDP damage. The NIF final optics hardware has been designed to enable easy retrieval, surface-damage mitigation, and recycling of optics.

  9. Pyroelectricity and its role in optical damage of potassium titanyl phosphate crystals

    SciTech Connect

    Cooke, D.W.; Bennett, B.L.; Thomas, J.C.; Petrin, R.R.

    1996-12-01

    The origin of optical damage in potassium titanyl phosphate (KTP) crystals has been vigorously investigated since its introduction as a nonlinear optical material in 1976. It is well known that this material exhibits a laser damage threshold that limits its use in many high average-power applications, especially frequency doubling of Nd-doped lasers. Both photochromic and electrochromic damage can be induced in KTP. Until recently, it was thought that these two types of damage were distinctly different, possibly involving different mechanisms; however, new data show that electrochromic-like damage can be induced in KT? by laser irradiation only, implying the existence of an internal electric field. We have recently observed bursts of light (optical scintillations) when heating KTP crystals at 0.1 - 1.0 K/s in the temperature range 8 - 675 K. The scintillations correspond to molecular nitrogen emission occurring during the electrical breakdown of air near the crystal surface, and imply the existence of pyroelectric fields in KTP exceeding 30 kV/cm. These fields (and concomitant currents) were induced by 10.6 {mu}m laser irradiation. The observation of pyroelectric effects, heretofore not considered in KTP damage models, provides an important new insight into the possible cause of the recently observed {open_quotes}electrochromic-like{close_quotes} photochromic damage in KTP.

  10. Investigating the relationship between material properties and laser-induced damage threshold of dielectric optical coatings at 1064 nm

    NASA Astrophysics Data System (ADS)

    Bassiri, Riccardo; Clark, Caspar; Martin, Iain W.; Markosyan, Ashot; Murray, Peter G.; Tessmer, Joseph; Rowan, Sheila; Fejer, Martin M.

    2015-11-01

    The Laser Induced Damage Threshold (LIDT) and material properties of various multi-layer amorphous dielectric optical coatings, including Nb2O5, Ta2O5, SiO2, TiO2, ZrO2, AlN, SiN, LiF and ZnSe, have been studied. The coatings were produced by ion assisted electron beam and thermal evaporation; and RF and DC magnetron sputtering at Helia Photonics Ltd, Livingston, UK. The coatings were characterized by optical absorption measurements at 1064 nm by Photothermal Common-path Interferometry (PCI). Surface roughness and damage pits were analyzed using atomic force microscopy. LIDT measurements were carried out at 1064 nm, with a pulse duration of 9.6 ns and repetition rate of 100 Hz, in both 1000-on-1 and 1-on-1 regimes. The relationship between optical absorption, LIDT and post-deposition heat-treatment is discussed, along with analysis of the surface morphology of the LIDT damage sites showing both coating and substrate failure.

  11. Optical fiber sensors for damage analysis in aerospace materials

    NASA Technical Reports Server (NTRS)

    Schindler, Paul; May, Russell; Claus, Richard

    1995-01-01

    Under this grant, fiber optic sensors were investigated for use in the nondestructive evaluation of aging aircraft. Specifically, optical fiber sensors for detection and location of impacts on a surface, and for detection of corrosion in metals were developed. The use of neural networks was investigated for determining impact location by processing the output of a network of fiberoptic strain sensors distributed on a surface. This approach employs triangulation to determine location by comparing the arrival times at several sensors, of the acoustic signal generated by the impact. For this study, a neural network simulator running on a personal computer was used to train a network using a back-propagation algorithm. Fiber optic extrinsic Fabry-Perot interferometer (EFPI) strain sensors are attached to or embedded in the surface, so that stress waves emanating from an impact can be detected. The ability of the network to determine impact location by time-or-arrival of acoustic signals was assessed by comparing network outputs with actual experimental results using impacts on a panel instrumented with optical fiber sensors. Using the neural network to process the sensor outputs, the impact location can be inferred to centimeter range accuracy directly from the arrival time data. In addition, the network can be trained to determine impact location, regardless of material anisotropy. Results demonstrate that a back-propagation network identifies impact location for an anisotropic graphite/bismaleimide plate with the same accuracy as that for an isotropic aluminum plate. Two different approaches were investigated for the development of fiber optic sensors for corrosion detection in metals, both utilizing optical fiber sensors with metal coatings. In the first approach, an extrinsic Fabry-Perot interferometric fiber optic strain sensor was placed under tensile stress, and while in the resulting strained position, a thick coating of metal was applied. Due to an increase in

  12. Smart Optical Material Characterization System and Method

    NASA Technical Reports Server (NTRS)

    Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor)

    2015-01-01

    Disclosed is a system and method for characterizing optical materials, using steps and equipment for generating a coherent laser light, filtering the light to remove high order spatial components, collecting the filtered light and forming a parallel light beam, splitting the parallel beam into a first direction and a second direction wherein the parallel beam travelling in the second direction travels toward the material sample so that the parallel beam passes through the sample, applying various physical quantities to the sample, reflecting the beam travelling in the first direction to produce a first reflected beam, reflecting the beam that passes through the sample to produce a second reflected beam that travels back through the sample, combining the second reflected beam after it travels back though the sample with the first reflected beam, sensing the light beam produced by combining the first and second reflected beams, and processing the sensed beam to determine sample characteristics and properties.

  13. Photonic Crystal Optical Tweezers with High Efficiency for Live Biological Samples and Viability Characterization.

    PubMed

    Jing, Peifeng; Wu, Jingda; Liu, Gary W; Keeler, Ethan G; Pun, Suzie H; Lin, Lih Y

    2016-01-01

    We propose and demonstrate a new optical trapping method for single cells that utilizes modulated light fields to trap a wide array of cell types, including mammalian, yeast, and Escherichia coli cells, on the surface of a two-dimensional photonic crystal. This method is capable of reducing the required light intensity, and thus minimizing the photothermal damage to living cells, thereby extending cell viability in optical trapping and cell manipulation applications. To this end, a thorough characterization of cell viability in optical trapping environments was performed. This study also demonstrates the technique using spatial light modulation in patterned manipulation of live cell arrays over a broad area. PMID:26814808

  14. Photonic Crystal Optical Tweezers with High Efficiency for Live Biological Samples and Viability Characterization

    PubMed Central

    Jing, Peifeng; Wu, Jingda; Liu, Gary W.; Keeler, Ethan G.; Pun, Suzie H.; Lin, Lih Y.

    2016-01-01

    We propose and demonstrate a new optical trapping method for single cells that utilizes modulated light fields to trap a wide array of cell types, including mammalian, yeast, and Escherichia coli cells, on the surface of a two-dimensional photonic crystal. This method is capable of reducing the required light intensity, and thus minimizing the photothermal damage to living cells, thereby extending cell viability in optical trapping and cell manipulation applications. To this end, a thorough characterization of cell viability in optical trapping environments was performed. This study also demonstrates the technique using spatial light modulation in patterned manipulation of live cell arrays over a broad area. PMID:26814808

  15. Photonic Crystal Optical Tweezers with High Efficiency for Live Biological Samples and Viability Characterization

    NASA Astrophysics Data System (ADS)

    Jing, Peifeng; Wu, Jingda; Liu, Gary W.; Keeler, Ethan G.; Pun, Suzie H.; Lin, Lih Y.

    2016-01-01

    We propose and demonstrate a new optical trapping method for single cells that utilizes modulated light fields to trap a wide array of cell types, including mammalian, yeast, and Escherichia coli cells, on the surface of a two-dimensional photonic crystal. This method is capable of reducing the required light intensity, and thus minimizing the photothermal damage to living cells, thereby extending cell viability in optical trapping and cell manipulation applications. To this end, a thorough characterization of cell viability in optical trapping environments was performed. This study also demonstrates the technique using spatial light modulation in patterned manipulation of live cell arrays over a broad area.

  16. Parabolic Trough VSHOT Optical Characterization in 2005-2006 (Presentation)

    SciTech Connect

    Wendelin, T.

    2006-02-01

    This presentation regarding parabolic trough VSHOT optical characterization describes trough deployment and operation phases including: development, manufacture/installation, and maintenance/operation.

  17. Optical characterization of lyotropic chromonic liquid crystals

    NASA Astrophysics Data System (ADS)

    Liu, Hui

    Lyotropic chromonic liquid crystals (LCLCs) represent a special class of lyotropic mesophases markedly different from conventional amphiphilic mesogens. Materials forming LCLCs are composed of plank-like molecules with a polyaromatic central core and hydrophilic ionic groups at the periphery. The individual molecules tend to assemble into rodlike aggregates that form the N phase once the concentration exceeds about 0.1M. The LCLC materials show a tremendous potential for applications in optics as self-assembling polarizing and compensating films and in the area of real-time biological sensing. The emerging applications require an understanding of basic properties of LCLC. This work addresses these needs by providing the optical characterization of LCLC. We studied in detail the optical anisotropic properties of three different nematic LCLCs: disodium cromoglycate (DSCG), Blue 27, and Violet 20. We determined the birefringence of these three materials as the function of the temperature T and wavelength lambda and the corresponding dependencies of the absorption coefficients for Blue 27 and Violet 20. The birefringence is negative and significantly lower in the absolute value as compared to the birefringence of typical thermotropic N materials. We determined the scalar order parameter of the nematic phase of Blue 27 and its temperature dependence. The scalar order parameter is close to the one predicted by the classic Onsager theory for solutions of rigid rods. However, this similarity is not complete, as the measured scalar order parameter depends on temperature. The I-N pretransitional fluctuations in an aqueous solution of DSCG were studied by light scattering. We obtained the correlation length of the orientational order-parameter fluctuations of isotropic DSCG solution. The pretransitional behavior of light scattering does not completely follow the classic Landau-de Gennes model. This feature is explained by the variable length of DSCG aggregates as a function

  18. Characterization of fluoride nanocrystals for optical refrigeration

    NASA Astrophysics Data System (ADS)

    Soares de Lima Filho, Elton; Quintanilla, Marta; Vetrone, Fiorenzo; Nemova, Galina; Kummara, Venkata Krishaniah; Kashyap, Raman

    2015-03-01

    This paper reports on the characterization of nanocrystalline powders of ytterbium doped YLiF4 for applications in optical refrigeration. Here we used powders with nanocrystals of Yb 3+ concentrations of (10, 15, 20) mol % and lengths (70, 66, 96) nm. Our preliminary spectroscopic measurements did not show an enhancement in the absorption at the long-wavelength tail of the spectra of the nanocrystalline powder when compared with bulk Yb:YLiF4, indicating that the increase of the phonon-assisted excitation is not large enough to play a significant role in cooling in the present conditions. One advantage of nanocrystalline powders over bulk crystals is the possibility of enhancing the absorption by the realization of cavity-less pump recycling through photon localization [1]. While photon localization also increases the reabsorption of the fluorescence depending on the quantum efficiency of the material and can mitigate cooling, it allows the use of crystals of low enough concentrations to avoid deleterious effects such as ion-ion energy transfer followed by quenching. The pump intensity enhancement favors upconversion luminescence to visible wavelengths, which can be used for optical refrigeration and extends the scope of the application for the material. We observed both green and blue emission from the samples and investigate the processes which lead to it. We present the experimental investigation of the nanocrystals' absorption and emission spectra and the first excited state lifetime measurements, which are used to estimate the nanocrystal's photoluminescence quantum efficiency.

  19. Characterization of automotive paint by optical coherence tomography.

    PubMed

    Zhang, Ning; Wang, Chengming; Sun, Zhenwen; Mei, Hongcheng; Huang, Wei; Xu, Lei; Xie, Lanchi; Guo, Jingjing; Yan, Yuwen; Li, Zhihui; Xu, Xiaojing; Xue, Ping; Liu, Ningning

    2016-09-01

    Automotive paint is common trace evidence that plays a significant role in many vehicle-related criminal cases. However, the conventional methods of obtaining tomographic images tend to damage the samples. Optical coherence tomography (OCT) is a novel method to obtain high-resolution and cross-sectional images of the automotive paints in a non-destructive, and high-speed manner. In this study, OCT was applied to image and analyze the automotive paint, using scanning electron microscope (SEM) as reference. Eight automotive paint samples of different brands were examined. The images of multi-layer structures provided by OCT system with 5μm depth resolution were consistent with those by SEM. To distinguish different paints with similar visual appearance, we extracted internal structural features from the images using peak analysis and optical attenuation fit. Six characterized parameters were found to distinguish the samples including the optical path length (OPL) of base coat, the optical attenuation coefficient (OAC) of base coat, the OPL of clear coat, the back-scattering ratio (BSR) of clear coat and base coat, the OPL of primer surfacer, and the BSR of base coat and primer. Statistical differences were evaluated by an independent t-test with p<0.05. OCT was applied to analyze repainted paint as well. Three-dimensional OCT reconstruction of the paints was also implemented to create en face (transverse section) images for morphology examination and comparison. These results suggest that OCT imaging can provide additional new features for analyzing the automotive paints and thereby may be a promising supplement to traditional methods. Meanwhile, the OCT system is favorable for achieving in-situ and real-time examination at the scene of crime. PMID:27341546

  20. In situ compressive damage of cement paste characterized by lab source X-ray computer tomography

    SciTech Connect

    Wan, Keshu; Xue, Xiaobo

    2013-08-15

    This paper aims at illustrating the potential of lab source X-ray CT for studying the damage behavior of cement based materials through in situ load experiments. This approach permits quantifying the microstructure prior and during loading. The load damage is separated from the specimen deformation using an image interpolation method. A quantitative relationship between external load and internal specimen damage is analyzed using the statistical information of gray scale values of the CT data. Local damage degrees are defined on 3D subset, and the 3D spatial distribution of damage information is clarified in this research. - Highlights: • On line damage is characterized by lab source X-ray CT. • Loading damage is separated with the specimen deformation. • Local damage is analyzed using gray scale values of the CT data. • 3D spatial distribution of the local damage information is clarified.

  1. Cleaning Process Versus Laser-Damage Threshold of Coated Optical Components

    SciTech Connect

    Rigatti, A.L.

    2005-03-31

    The cleaning of optical surfaces is important in the manufacture of high-laser-damage-threshold coatings, which are a key component on peak-power laser systems such as OMEGA located at the Laboratory for Laser Energetics (LLE). Since cleaning adds time, labor, and ultimately cost to the final coated component, this experiment was designed to determine the impact of different cleaning protocols on the measured laser-damage performance.

  2. Damage Resistant Optical Glasses for High Power Lasers: A Continuing Glass Science and Technology Challenge

    SciTech Connect

    Campbell, J H

    2002-08-28

    A major challenge in the development of optical glasses for high-power lasers is reducing or eliminating laser-induced damage to the interior (bulk) and the polished surface of the glass. Bulk laser damage in glass generally originates from inclusions. With the development of novel glass melting and forming processes it is now possible to make both fused silica and a suit of meta-phosphate laser glasses in large sizes ({approx}>0.5-lm diameter), free of inclusions and with high optical homogeneity ({approx} 10{sup -6}). Considerable attention also has been focused on improving the laser damage resistance to polished optical glass surfaces. Studies have shown that laser-induced damage to surfaces grows exponentially with the number of shots when illuminated with nano-second pulses at 351-nm above a given fluence threshold. A new approach for reducing and eliminating laser-induced surface damage relies on a series of post-polishing treatment steps. This damage improvement method is briefly reviewed.

  3. Synthesis, characterization and optical properties of nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Shoutian

    ZnO, Si, silica, Ge, Ga oxide, W oxide and Mo oxide nanoparticles have been synthesized and characterized, and their optical properties have been investigated. These particles were synthesized by a Laser Vaporization and Controlled Condensation (LVCC) technique in a modified diffusion cloud chamber. The particles deposited on smooth substrates reveal highly organized web-like structures with uniform micrometer size pores. The effect of solvents on the web-like structures was also investigated. ZnO nanoparticles were also prepared by wet chemical methods such as the reversed micelle and sol solutions technique. The photoluminescence quantum yield is enhanced 10 times once the surfaces of the ZnO nanoparticles are coated with a layer of stearate molecules. Many techniques have been used to characterize the nanoparticles. SEM gives information about particle size and morphology; X-ray diffraction and Raman spectroscopy determine the crystallinity and crystal structure; XPS and FTIR reveal the surface chemical composition; UV-vis spectroscopy and photoluminescence measurements characterize the optical properties of nanoparticles. Silica nanoparticles, prepared in an amorphous phase, show bright blue photoluminescence upon irradiation with UV light, but the luminescence has a very short lifetime (less than 20 ns). Si nanoparticles, with a diamond-like crystal phase, acquire oxidized-surfaces on exposure to air. The surface-oxidized Si nanocrystals show a short- lived blue emission characteristic of the SiO2 coating and a longer-lived red emission at room temperature. The lifetime of the red emission depends on the emission wavelength. Some substituted benzene molecules and tungsten oxide nanoparticles can quench the red photoluminescence of the Si nanocrystals. Tungsten oxide and molybdenum oxide nanoparticles show photochromic properties: they change color to blue when irradiated. The photons drive a transition from one chemical state to another. The color change of

  4. Seismic damage identification using multi-line distributed fiber optic sensor system

    NASA Astrophysics Data System (ADS)

    Ou, Jinping; Hou, Shuang

    2005-06-01

    Determination of the actual nonlinear inelastic response mechanisms developed by civil structures such as buildings and bridges during strong earthquakes and post-earthquake damage assessment of these structures represent very difficult challenges for earthquake structural engineers. One of the main reasons is that the traditional sensor can't serve for such a long period to cover an earthquake and the seismic damage location in the structure can't be predicted in advance definitely. It is thought that the seismic damage of reinforced concrete (RC) structure can be related to the maximum response the structure, which can also be related to the cracks on the concrete. A distributed fiber optic sensor was developed to detect the cracks on the reinforced concrete structure under load. Fiber optic couples were used in the sensor system to extend the sensor system's capacity from one random point detection to more. An optical time domain reflectometer (OTDR) is employed for interrogation of the sensor signal. Fiber optic sensors are attached on the surface of the concrete by the epoxy glue. By choosing the strength of epoxy, the damage state of the concrete can be responded to the occurrence of the Fresnel scattering in the fiber optic sensor. Experiments involved monotonic loading to failure. Finally, the experimental results in terms of crack detection capability are presented and discussed.

  5. Theoretical analysis for temperature dependence of laser- induced damage threshold of optical thin films

    NASA Astrophysics Data System (ADS)

    Mikami, K.; Motokoshi, S.; Somekawa, T.; Jitsuno, T.; Fujita, M.; Tanaka, KA; Azechi, H.

    2016-03-01

    The temperature dependence of the laser-induced damage threshold on optical coatings was studied in detail for laser pulses from 123 K to 473 K at different temperatures. The laser-induced damage threshold increased with decreasing temperatures when we tested long pulses (200 ps and 4 ns). The temperature dependence, however, was reversed for pulses shorter than a few picoseconds (100 fs testing). We propose a scaling model with a flowchart that includes three separate processes: free-electron generation, electron multiplication, and electron heating. Furthermore, we calculated the temperature dependence of laser-induced damage thresholds at different temperatures. Our calculation results agreed well with the experimental results.

  6. Catastrophic optical mirror damage in diode lasers monitored during single-pulse operation

    NASA Astrophysics Data System (ADS)

    Ziegler, Mathias; Tomm, Jens W.; Reeber, David; Elsaesser, Thomas; Zeimer, Ute; Larsen, Henning E.; Petersen, Paul M.; Andersen, Peter E.

    2009-05-01

    Catastrophic optical mirror damage (COMD) is analyzed for 808 nm emitting diode lasers in single-pulse operation in order to separate facet degradation from subsequent degradation processes. During each pulse, nearfield and thermal images are monitored. A temporal resolution better than 7 μs is achieved. The thermal runaway process is unambiguously related to the occurrence of a "thermal flash." A one-by-one correlation between nearfield, thermal flash, thermal runaway, and structural damage is observed. The single-pulse excitation technique allows for controlling the propagation of the structural damage into the cavity. We propose this technique for the analysis of early stages of COMD.

  7. Laser damage threshold of gelatin and a copper phthalocyanine doped gelatin optical limiter

    SciTech Connect

    Brant, M.C.; McLean, D.G.; Sutherland, R.L.

    1996-12-31

    The authors demonstrate optical limiting in a unique guest-host system which uses neither the typical liquid or solid host. Instead, they dope a gelatin gel host with a water soluble Copper (II) phthalocyaninetetrasulfonic acid, tetrasodium salt (CuPcTs). They report on the gelatin`s viscoelasticity, laser damage threshold, and self healing of this damage. The viscoelastic gelatin has mechanical properties quite different than a liquid or solid. The authors` laser measurements demonstrate that the single shot damage threshold of the undoped gelatin host increases with decreasing gelatin concentration. The gelatin also has a much higher laser damage threshold than a stiff acrylic. Unlike brittle solids, the soft gelatin self heals from laser induced damage. Optical limiting test also show the utility of a gelatin host doped with CuPcTs. The CuPcTs/gelatin matrix is not damaged at incident laser energies 5 times the single shot damage threshold of the gelatin host. However, at this high laser energy the CuPcTs is photo bleached at the beam waist. The authors repair photo bleached sites by annealing the CuPcTs/gelatin matrix.

  8. Prediction of feather damage in laying hens using optical flows and Markov models

    PubMed Central

    Lee, Hyoung-joo; Roberts, Stephen J.; Drake, Kelly A.; Dawkins, Marian Stamp

    2011-01-01

    Feather pecking in laying hens is a major welfare and production problem for commercial egg producers, resulting in mortality, loss of production as well as welfare issues for the damaged birds. Damaging outbreaks of feather pecking are currently impossible to control, despite a number of proposed interventions. However, the ability to predict feather damage in advance would be a valuable research tool for identifying which management or environmental factors could be the most effective interventions at different ages. This paper proposes a framework for forecasting the damage caused by injurious pecking based on automated image processing and statistical analysis. By frame-by-frame analysis of video recordings of laying hen flocks, optical flow measures are calculated as indicators of the movement of the birds. From the optical flow datasets, measures of disturbance are extracted using hidden Markov models. Based on these disturbance measures and age-related variables, the levels of feather damage in flocks in future weeks is predicted. Applying the proposed method to real-world datasets, it is shown that the disturbance measures offer improved predictive values for feather damage thus enabling an identification of flocks with probable prevalence of damage and injury later in lay. PMID:20659929

  9. Laser-induced damage of fused silica on high-power laser: beam intensity modulation, optics defect, contamination

    NASA Astrophysics Data System (ADS)

    Zhao, Dongfeng; Sun, Mingyin; Wu, Rong; Lu, Xinqiang; Lin, Zunqi; Zhu, Jianqiang

    2015-11-01

    The wedged focus lens of fused silica, one of the final optics assembly's optics, focuses the 351 nm beam onto target and separates the residual 1053 and 527 nm light with 351 nm light. After the experiment with beam energies at 3ω range from 3 to 5KJ, and pulse shapes about 3ns, the wedged focus lens has laser-induced damage at particular area. Analysis the damage result, there are three reasons to induce these damages. These reasons are beam intensity modulation, optics defect and contamination that cause different damage morphologies. The 3ω beam intensity modulation, one of three factors, is the mostly import factor to induce damage. Here, the n2 nonlinear coefficient of fused silica material can lead to small-scale self-focusing filament because of optics thickness and beam intensity. And some damage-filaments' tails are bulk damage spots because there are subsurface scratches or metal contaminations.

  10. Probabilistic Damage Characterization Using the Computationally-Efficient Bayesian Approach

    NASA Technical Reports Server (NTRS)

    Warner, James E.; Hochhalter, Jacob D.

    2016-01-01

    This work presents a computationally-ecient approach for damage determination that quanti es uncertainty in the provided diagnosis. Given strain sensor data that are polluted with measurement errors, Bayesian inference is used to estimate the location, size, and orientation of damage. This approach uses Bayes' Theorem to combine any prior knowledge an analyst may have about the nature of the damage with information provided implicitly by the strain sensor data to form a posterior probability distribution over possible damage states. The unknown damage parameters are then estimated based on samples drawn numerically from this distribution using a Markov Chain Monte Carlo (MCMC) sampling algorithm. Several modi cations are made to the traditional Bayesian inference approach to provide signi cant computational speedup. First, an ecient surrogate model is constructed using sparse grid interpolation to replace a costly nite element model that must otherwise be evaluated for each sample drawn with MCMC. Next, the standard Bayesian posterior distribution is modi ed using a weighted likelihood formulation, which is shown to improve the convergence of the sampling process. Finally, a robust MCMC algorithm, Delayed Rejection Adaptive Metropolis (DRAM), is adopted to sample the probability distribution more eciently. Numerical examples demonstrate that the proposed framework e ectively provides damage estimates with uncertainty quanti cation and can yield orders of magnitude speedup over standard Bayesian approaches.

  11. Characterization of commercial fiber optic connectors - Preliminary report

    SciTech Connect

    Andrews, Larry A.; Williams, Randy J.

    1998-09-01

    Several types of commercial fiber optic connectors were characterized for potential use in a Sandia designed Laser Diode Ignition (LDI) system. The characterization included optical performance while the connectors were subjected to the more dynamic environmental conditions experienced in weapons applications. The environmental testing included temperature cycling, random vibration, and mechanical shock. This report presents a performance assessment of the fiber optic connectors and fiber included in the characterization. The desirable design features are described for a fiber optic connector that must survive the dynamic environment of weapon systems. The more detailed performance of each connector type will be included as resources permit.

  12. An investigation of the chemical and physical properties of pristine, electrochromically damaged, and photochromically damaged KTiOPO{sub 4} (KTP) using surface analytical and optical spectroscopic techniques

    SciTech Connect

    Quagliano, J.R.; Petrin, R.R.; Trujillo, T.C.; Cockroft, N.J.; Paffett, M.T.; Maggiore, C.J.; Jacco, J.C.

    1995-03-01

    A variety of experimental techniques were employed to study the properties of electrochromically (EC) damaged, photochromically (PC) damaged, and pristine KTiOP0{sub 4} (KTP). Additionally, nonlinear optical calculations were performed to complement the experimental work in an effort to elucidate the respective mechanisms operative in producing EC and PC damage to KTP. Several independent experiments indicate that there is Ti deficiency in the EC damaged material, which is due to migration of these ions to the electrode surface. The laser experiments indicate that UV radiation can produce reversible PC damage. UV-producing SFG processes accidentally occurring in SHG cut KTP may lead to macroscopic damage. It must be emphasized that a fundamentally different mechanism is responsible for EC damaged versus PC damaged KTP.

  13. Structure/property (constitutive and dynamic strength/damage) characterization of additively manufactured 316L SS

    NASA Astrophysics Data System (ADS)

    Gray, G. T., III; Livescu, V.; Rigg, P. A.; Trujillo, C. P.; Cady, C. M.; Chen, S. R.; Carpenter, J. S.; Lienert, T. J.; Fensin, S.

    2015-09-01

    For additive manufacturing (AM), the certification and qualification paradigm needs to evolve as there exists no "ASTM-type" additive manufacturing certified process or AM-material produced specifications. Accordingly, utilization of AM materials to meet engineering applications requires quantification of the constitutive properties of these evolving materials in comparison to conventionally-manufactured metals and alloys. Cylinders of 316L SS were produced using a LENS MR-7 laser additive manufacturing system from Optomec (Albuquerque, NM) equipped with a 1kW Yb-fiber laser. The microstructure of the AM-316L SS is detailed in both the as-built condition and following heat-treatments designed to obtain full recrystallization. The constitutive behavior as a function of strain rate and temperature is presented and compared to that of nominal annealed wrought 316L SS plate. The dynamic damage evolution and failure response of all three materials was probed using flyer-plate impact driven spallation experiments at a peak stress of 4.5 GPa to examine incipient spallation response. The spall strength of AM-produced 316L SS was found to be very similar for the peak shock stress studied to that of annealed wrought or AM-316L SS following recrystallization. The damage evolution as a function of microstructure was characterized using optical metallography.

  14. Linking Material Properties and Microstructures to Characterize Damage Associated with an Underground Explosion in Granite

    NASA Astrophysics Data System (ADS)

    Wilson, J. E.; Broome, S.; Sussman, A. J.; Townsend, M.; Schultz-Fellenz, E. S.

    2013-12-01

    The Source Physics Experiment, conducted in granite in Nevada, is a series of explosive tests designed to study the generation and propagation of seismic waves. Extensive seismic monitoring and site rock characterization are being used to improve the predictive capability of models for detecting and characterizing underground explosions. Site rock characterization includes geomechanical and material properties testing, core-scale fracture identification, and optical microscopy studies. Geomechanical and material properties determined via laboratory testing of the site rocks include unconfined compressive strength, Young's modulus, Poisson's ratio, and bulk density. Detailed fracture mapping and characterization of meso- and micro-scale fractures in recovered cores are being conducted and include mineralization changes and the extent of crushed or fractured zone away from the source. We report on the analysis of microfractures in these cores, which provide a detailed and quantitative dataset on the extent and nature of damage in the recovered cores. Microfracture density and character (open, sealed, healed) are recorded in order to differentiate sets of microfractures associated with explosive tests. Densities (mf/mm) of open microfractures correlate with source-related damage, and increase from pre- to post-test samples. Microfracture densities are affected by pre-existing fractures, depending on fracture-zone mineralogy and alteration. These microfracture density data, linked to the bulk material properties, geomechanical properties, and the structural features of the rock at the core-scale, define a damage zone surrounding the source at depth. This link is essential to understanding how the bulk material properties manifest themselves in the rock and how that might affect energy propagation. Work by Los Alamos National Laboratory was sponsored by the National Nuclear Security Administration Award No. DE-AC52-06NA25946/NST10-NCNS-PD00. Work by National Security

  15. Damage characteristics at optical fiber connector for high power light transmission

    NASA Astrophysics Data System (ADS)

    Matsuda, S.; Shibuya, T.; Wakaki, M.

    2008-01-01

    In the field of optical communication, either fusion splicing of optical fibers or physical contact between optical-fibers using a fiber connector has been utilized as the typical method of optical fiber connection. Optical fiber connectors have been widely employed in optical transmission systems according to their features of easy and quick connection without special apparatus to connect fibers. The power of laser diodes for light sources became more intense and the multiplexing of wavelength (WDM) of a light source was enhanced with increasing traffic data. As a result, intense light transmits through the optical fiber. The high power transmission characteristics of the optical fiber connector are important factors to realize dense wavelength division multiplexing systems (DWDM). In this paper, we present an experimental investigation about the degradation of the transmission properties through the optical fiber connector by introducing the contamination between the end faces of a connector. The metal foils to simulate the contamination at the end of the core were inserted between the optical fibers to cover the core of an optical fiber partially. As metal foils, Nickel, SUS304, and Phosphor Bronze which were typically used as the components of the ferrule and sleeve were selected. The Nd: YAG laser with the wavelength of 1064 nm was used as a high power light source at various output powers. The transmission loss was set by adjusting the insertion of a metal foil into the core region of the fiber and the temperature rising of the connector induced by the absorption of incident light was measured at a sleeve portion. The damage at the end face of the physical contact region was observed using an optical microscope. The temperatures increase of the core of the fiber was estimated for the fiber connector with a zirconia ferrule through the thermal simulation using the MSC Visual Nastran. The damage of the fiber end face was recognized depending on the species of

  16. The potential of optical coherence tomography in meniscal tear characterization

    NASA Astrophysics Data System (ADS)

    Ling, Hang-yin; Guo, Shuguang; Thieman, Kelley M.; Wise, Brent T.; Pozzi, Antonio; Xie, Huikai; Horodyski, MaryBeth

    2009-02-01

    Meniscal tear is one of the most common knee injuries leading to pain and discomfort. Partial and total meniscectomies have been widely used to treat the avascular meniscal injuries in which tears do not heal spontaneously. However, the meniscectomies would cause an alteration of the tibiofemoral contact mechanics resulting in progressive osteoarthritis (OA). To mitigate the progression of OA, maximal preservation of meniscal tissue is recommended. The clinical challenge is deciding which meniscal tears are amenable to repair and which part of damaged tissues should be removed. Current diagnosis techniques such as arthroscopy and magnetic resonance imaging can provide macrostructural information of menisci, but the microstructural changes that occur prior to the observable meniscal tears cannot be identified by these techniques. Serving as a nondestructive optical biopsy, optical coherence tomography (OCT), a newly developed imaging modality, can provide high resolution, cross-sectional images of tissues and has been shown its capabilty in arthroscopic evaulation of articular cartilage. Our research was to demonstrate the potential of using OCT for nondestructive characterization of the histopathology of different types of meniscal tears from clinical cases in dogs, providing a fundamental understanding of the failure mechanism of meniscal tears. First, cross-sectional images of torn canine menisci obtained from the OCT and scanning electronic microscopy (SEM) were be compared. By studying the organization of collegan fibrils in torn menisci from the SEM images, the feasibility of using OCT to characterize the organization of collegan fibrils was elucidated. Moreover, the crack size of meniscal tears was quantatitively measured from the OCT images. Changes in the crack size of the tear may be useful for understanding the failure mechanism of meniscal tears.

  17. Halogen Occultation Experiment (HALOE) optical filter characterization

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1989-01-01

    The Halogen Occultation Experiment (HALOE) is a solar occultation experiment that will fly on the Upper Atmosphere Research Satellite to measure mixing ratio profiles of O3, H2O, NO2, NO, CH4, HCl, and HF. The inversion of the HALOE data will be critically dependent on a detailed knowledge of eight optical filters. A filter characterization program was undertaken to measure in-band transmissions, out-of-band transmissions, in-band transmission shifts with temperature, reflectivities, and age stability. Fourier Transform Infrared Spectrometers were used to perform measurements over the spectral interval 400/cm to 6300/cm (25 micrometers to 1.6 micrometers). Very high precision (0.1 percent T) in-band measurements and very high resolution (0.0001 percent T) out-of-band measurements have been made. The measurements revealed several conventional leaks at 0.01 percent transmission and greatly enhanced (1,000) leaks to the 2-element filters when placed in a Fabry-Perot cavity. Filter throughput changes by 5 percent for a 25 C change in filter temperature.

  18. A unified optical damage criterion based on the probability density distribution of detector signals

    NASA Astrophysics Data System (ADS)

    Somoskoi, T.; Vass, Cs.; Mero, M.; Mingesz, R.; Bozoki, Z.; Osvay, K.

    2013-11-01

    Various methods and procedures have been developed so far to test laser induced optical damage. The question naturally arises, that what are the respective sensitivities of these diverse methods. To make a suitable comparison, both the processing of the measured primary signal has to be at least similar to the various methods, and one needs to establish a proper damage criterion, which has to be universally applicable for every method. We defined damage criteria based on the probability density distribution of the obtained detector signals. This was determined by the kernel density estimation procedure. We have tested the entire evaluation procedure in four well-known detection techniques: direct observation of the sample by optical microscopy; monitoring of the change in the light scattering power of the target surface and the detection of the generated photoacoustic waves both in the bulk of the sample and in the surrounding air.

  19. Cell damage in near-infrared multimode optical traps as a result of multiphoton absorption

    NASA Astrophysics Data System (ADS)

    König, K.; Liang, H.; Berns, M. W.; Tromberg, B. J.

    1996-07-01

    We report on cell damage of single cells confined in continuous-wave (cw), near-infrared (NIR) multimode optical traps as a result of multiphoton absorption phenomena. Trapping beams at NIR wavelengths less than 800 nm are capable of damaging cells through a two-photon absorption process. Cell damage is more pronounced in multimode cw traps compared with single-frequency true cw NIR traps because of transient power enhancement by longitudinal mode beating. Partial mode locking in tunable cw Ti:sapphire lasers used as trapping beam sources can produce unstable subnanosecond pulses at certain wavelengths that amplify multiphoton absorption effects significantly. We recommend the use of single-frequency long-wavelength NIR trapping beams for optical micromanipulation of vital cells.

  20. The characterization of widespread fatigue damage in fuselage structure

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Willard, Scott A.; Miller, Matthew

    1994-01-01

    The characteristics of widespread fatigue damage (WSFD) in fuselage riveted structure were established by detailed nondestructive and destructive examinations of fatigue damage contained in a full size fuselage test article. The objectives of this were to establish an experimental data base for validating emerging WSFD analytical prediction methodology and to identify first order effects that contribute to fatigue crack initiation and growth. Detailed examinations were performed on a test panel containing four bays of a riveted lap splice joint. The panel was removed from a full scale fuselage test article after receiving 60,000 full pressurization cycles. The results of in situ examinations document the progression of fuselage skin fatigue crack growth through crack linkup. Detailed tear down examinations and fractography of the lap splice joint region revealed fatigue crack initiation sites, crack morphology, and crack linkup geometry. From this large data base, distributions of crack size and locations are presented and discussions of operative damage mechanisms are offered.

  1. Characterization of Creep-Damaged Grain Boundaries of Alloy 617

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Field, David P.

    2013-11-01

    Intergranular cracking and void nucleation occur over extended periods of time in alloy 617 when subjected to stress at high temperatures. Damage occurs inhomogeneously with some boundaries suffering failure, while others are seemingly immune to creep. Crack propagation associated with grain size, and grain boundary character was investigated to determine which types of grain boundaries are susceptible to damage and which are more resistant. Electron backscatter diffraction and a stereological approach to obtain the five-parameter grain boundary distribution were used to measure the proportions of each type of boundary in the initial and damaged structures. The samples were crept at 1273.15 K (1000 °C) at 25 MPa until fracture. It was found that in addition to low-angle and coherent twin boundaries, other low index boundary plane grain boundaries with twist character are relatively resistant to creep.

  2. Guided Wave and Damage Detection in Composite Laminates Using Different Fiber Optic Sensors

    PubMed Central

    Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

    2009-01-01

    Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH0) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent. PMID:22412347

  3. Development of high damage threshold optics for petawatt-class short-pulse lasers

    NASA Astrophysics Data System (ADS)

    Stuart, Brent C.; Perry, Michael D.; Boyd, Robert D.; Britten, Jerald A.; Shore, Bruce W.; Feit, Michael D.; Rubenchik, Alexander M.

    1995-04-01

    We report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, (tau) , ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm2 in the subpicosecond range from 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated (tau) 1/2 scaling indicate that damage results from plasma formation and ablation for (tau) 50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results.

  4. Time resolved studies of catastrophic optical mirror damage in red-emitting laser diodes

    SciTech Connect

    Elliott, Stella N.; Smowton, Peter M.; Ziegler, Mathias; Tomm, Jens W.; Zeimer, Ute

    2010-06-15

    We have observed the changing light intensity during catastrophic optical mirror damage (COMD) on the timescale of tens of nanoseconds using red-emitting AlGaInP quantum well based laser diodes. Using as-cleaved facets and this material system, which is susceptible to COMD, we recorded the drop in light intensity and the area of damage to the facet, as a function of current, for single, high current pulses. We found that in the current range up to 40 A, the total COMD process up to the drop of light intensity to nonlasing levels takes place on a timescale of hundreds of nanoseconds, approaching a limiting value of 200 ns, and that the measured area of facet damage showed a clear increase with drive current. Using a straightforward thermal model, we propose an explanation for the limiting time at high currents and the relationship between the time to COMD and the area of damaged facet material.

  5. Predictive modeling techniques for nanosecond-laser damage growth in fused silica optics.

    PubMed

    Liao, Zhi M; Abdulla, Ghaleb M; Negres, Raluca A; Cross, David A; Carr, Christopher W

    2012-07-01

    Empirical numerical descriptions of the growth of laser-induced damage have been previously developed. In this work, Monte-Carlo techniques use these descriptions to model the evolution of a population of damage sites. The accuracy of the model is compared against laser damage growth observations. In addition, a machine learning (classification) technique independently predicts site evolution from patterns extracted directly from the data. The results show that both the Monte-Carlo simulation and machine learning classification algorithm can accurately reproduce the growth of a population of damage sites for at least 10 shots, which is extremely valuable for modeling optics lifetime in operating high-energy laser systems. Furthermore, we have also found that machine learning can be used as an important tool to explore and increase our understanding of the growth process. PMID:22772252

  6. Development of high damage threshold optics for petawatt-class short-pulse lasers

    SciTech Connect

    Stuart, B.C.; Perry, M.D.; Boyd, R.D.

    1995-02-22

    The authors report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, {tau}, ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm{sup 2} in the subpicosecond range for 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated {tau}1/2 scaling indicate that damage results from plasma formation and ablation for {tau}{le}10 ps and from conventional melting and boiling for {tau}>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results.

  7. Image dissector photocathode solar damage test program. [solar radiation shielding using a fast optical lens

    NASA Technical Reports Server (NTRS)

    Smith, R. A.

    1977-01-01

    Image dissector sensors of the same type which will be used in the NASA shuttle star tracker were used in a series of tests directed towards obtaining solar radiation/time damage criteria. Data were evaluated to determine the predicted level of operability of the star tracker if tube damage became a reality. During the test series a technique for reducing the solar damage effect was conceived and verified. The damage concepts are outlined and the test methods and data obtained which were used for verification of the technique's feasibility are presented. The ability to operate an image dissector sensor with the solar image focussed on the photocathode by a fast optical lens under certain conditions is feasible and the elimination of a mechanical protection device is possible.

  8. Image Science and Analysis Group Spacecraft Damage Detection/Characterization

    NASA Technical Reports Server (NTRS)

    Wheaton, Ira M., Jr.

    2010-01-01

    This project consisted of several tasks that could be served by an intern to assist the ISAG in detecting damage to spacecrafts during missions. First, this project focused on supporting the Micrometeoroid Orbital Debris (MMOD) damage detection and assessment for the Hubble Space Telescope (HST) using imagery from the last two HST Shuttle servicing missions. In this project, we used coordinates of two windows on the Shuttle Aft flight deck from where images were taken and the coordinates of three ID points in order to calculate the distance from each window to the three points. Then, using the specifications from the camera used, we calculated the image scale in pixels per inch for planes parallel to and planes in the z-direction to the image plane (shown in Table 1). This will help in the future for calculating measurements of objects in the images. Next, tabulation and statistical analysis were conducted for screening results (shown in Table 2) of imagery with Orion Thermal Protection System (TPS) damage. Using the Microsoft Excel CRITBINOM function and Goal Seek, the probabilities of detection of damage to different shuttle tiles were calculated as shown in Table 3. Using developed measuring tools, volume and area measurements will be created from 3D models of Orion TPS damage. Last, mathematical expertise was provided to the Photogrammetry Team. These mathematical tasks consisted of developing elegant image space error equations for observations along 3D lines, circles, planes, etc. and checking proofs for minimal sets of sufficient multi-linear constraints. Some of the processes and resulting equations are displayed in Figure 1.

  9. Synthesis, characterization and optical applications of nanomaterials

    NASA Astrophysics Data System (ADS)

    Xu, Fen

    Nanomaterials have been studied extensively due to their potential application in electronics, photonics and nanodevices. There are a wide variety of methods developed to create the nano-scale materials. Chemical colloidal synthesis is the way most used since it is reproducible and high efficiency. Nanoparticles lie at the heart of nanoscience for their novel electronic, magnetic and optical properties. In this dissertation, there are two parts where researches have been performed based on the synthesis of metal and semiconductor nanoparticles. In part I, Semiconductor type-II core-shell quantum dots (QDs) ZnO-CdS have been synthesized by chemical colloidal method which was carried out in a two-step process. We initially synthesized ZnO core nanoparticles and overcoat them with CdS shell. UV-Visible spectra, photoluminescence spectra (PL), high resolution TEM images and X-ray microanalysis for composition studies of the core-shell nanoparticles were characterized. PL lifetime measurements showed this type-II ZnO-CdS core-shell QDs presented extended exciton lifetime due to the spatial separation of electrons and holes between the core and the shell, which opens various useful applications in biosensors and photovoltaic devices. In part II, normal Raman (NR) and surface enhanced Raman scattering (SERS) spectra of 3-hydroxyflavone (3-HF) have been measured. The SERS spectra were obtained both on a Ag electrode surface and on Ag colloidal nanoparticles. The experimental results support the DFT geometry calculations, which show that an adatom site at the vertex of Ag20 cluster binding with the 3-HF molecular plane tilted at an angle of about 53° to the surface is a low-energy structure. This is consistent with the enhancement of in-plane vibrational modes. Furthermore, the effect of fluence level on the discoloration of marble surfaces after the removal of the encrustation by 355 nm laser pulses was comparatively studied. Considering the thermochemical reaction

  10. Hollow-core waveguide characterization by optically induced particle transport.

    PubMed

    Measor, Philip; Kühn, Sergei; Lunt, Evan J; Phillips, Brian S; Hawkins, Aaron R; Schmidt, Holger

    2008-04-01

    We introduce a method for optical characterization of hollow-core optical waveguides. Radiation pressure exerted by the waveguide modes on dielectric microspheres is used to analyze salient properties such as propagation loss and waveguide mode profiles. These quantities were measured for quasi-single-mode and multimode propagation in on-chip liquid-filled hollow-core antiresonant reflecting optical waveguides. Excellent agreement with analytical and numerical models is found, demonstrating that optically induced particle transport provides a simple, inexpensive, and nondestructive alternative to other characterization methods. PMID:18382513

  11. Damage-resistant single-pulse optics for x-ray free electron lasers

    SciTech Connect

    Hau-Riege, S; London, R; Bogan, M; Chapman, H; Bergh, M

    2007-04-27

    Short-pulse ultraviolet and x-ray free electron lasers of unprecedented peak brightness are in the process of revolutionizing physics, chemistry, and biology. Optical components for these new light sources have to be able to withstand exposure to the extremely high-fluence photon pulses. Whereas most optics have been designed to stay intact for many pulses, it has also been suggested that single-pulse optics that function during the pulse but disintegrate on a longer timescale, may be useful at higher fluences than multiple-pulse optics. In this paper we will review damage-resistant single-pulse optics that recently have been demonstrated at the FLASH soft-x-ray laser facility at DESY, including mirrors, apertures, and nanolenses. It was found that these objects stay intact for the duration of the 25-fs FLASH pulse, even when exposed to fluences that exceed the melt damage threshold by fifty times or more. We present a computational model for the FLASH laser-material interaction to analyze the extent to which the optics still function during the pulse. Comparison to experimental results obtained at FLASH shows good quantitative agreement.

  12. Improving UV laser damage threshold of fused silica optics by wet chemical etching technique

    NASA Astrophysics Data System (ADS)

    Ye, Hui; Li, Yaguo; Yuan, Zhigang; Wang, Jian; Xu, Qiao; Yang, Wei

    2015-07-01

    Fused silica is widely used in high-power laser systems because of its good optical performance and mechanical properties. However, laser damage initiation and growth induced by 355 nm laser illumination in optical elements have become a bottleneck in the development of high energy laser system. In order to improve the laser-induced damage threshold (LIDT), the fused silica optics were treated by two types of HF-based etchants: 1.7%wt. HF acid and buffer oxide etchant (BOE: the mixture of 0.4%wt. HF and 12%wt. NH4F), respectively, for varied etching time. Damage testing shows that both the etchants increase the damage threshold at a certain depth of material removal, but further removal of material lowers the LIDT markedly. The etching rates of both etchants keep steady in our processing procedure, ~58 μg/min and ~85 μg/min, respectively. The micro-surface roughness (RMS and PV) increases as etching time extends. The hardness (H) and Young's modulus (E) of the fused silica etched for diverse time, measured by nano-indenter, show no solid evidence that LIDT can be related to hardness or Young's modulus.

  13. Subsurface damage of optical components and the influence on scattering properties

    NASA Astrophysics Data System (ADS)

    Draheim, Falk; Harnisch, Bernd; Weigel, Thomas

    1994-09-01

    The influence ofsurface damage under smooth optical surfaces on the scattering properties was investigated. Usually thissurface damage is filled and covered by a polishing layer. Thereforesurface damage does not contribute to the micro roughness of the surface. Three glasses, SF3, BK7, and SUPRASIL, with different Knoop hardness and related differentsurface damage density were chosen for the measurements. Three samples of each glass were polished with increasing polishing time in order to reduce the layer which contains thesurface damage. Beside the extensive measurements of the scatter behavior the samples were also investigated by means of microscopy (Nomarski, darkfield, cross polarization) and optical profilometry. The stray light was detected in the case of reflection (back scatter), transmission (forward scatter) and total reflection. In the case of totalreflection the scattered light behind the reflection surface was investigated. The detected scatter light was integrated over the measurement range and the resulting value was compared with the polishing time. Additional investigations were carried out to determine the influence on the light polarization.

  14. Optical Sensing using Fiber Bragg Gratings for Monitoring Structural Damage in Composite Over-Wrapped Vessels

    NASA Technical Reports Server (NTRS)

    Grant, Joseph

    2005-01-01

    Composite Over-Wrap Vessels are widely used in the aerospace community. They are made of thin-walled bottles that are over wrapped with high strength fibers embedded in a matrix material. There is a strong drive to reduce the weight of space borne vehicles and thus pushes designers to adopt COPVs that are over wrapped with graphite fibers embedded in its epoxy matrix. Unfortunately, this same fiber-matrix configuration is more susceptible to impact damage than others and to make matters worse; there is a regime where impacts that damage the over wrap leave no visible scar on the COPV surface. In this paper FBG sensors are presented as a means of monitoring and detecting these types of damage. The FBG sensors are surface mounted to the COPVs and optically interrogated to explore the structural properties of these composite pressure vessels. These gratings optically inscribed into the core of a single mode fiber are used as a tool to monitor the stress strain relation in the composite matrix. The response of these fiber-optic sensors is investigated by pressurizing the cylinder up to its burst pressure of around 4500 psi. A Fiber Optic Demodulation System built by Blue Road Research, is used for interrogation of the Bragg gratings.

  15. Optical self-sensing of impact damage in composites using E-glass cloth

    NASA Astrophysics Data System (ADS)

    Rauf, A.; Hand, R. J.; Hayes, S. A.

    2012-04-01

    Self-sensing of damage in composites employs the reinforcing fibres as the sensing element, obviating the need for addition of sensing elements to the system. Optical self-sensing systems in the past have relied on the use of low refractive index resins in order to work, preventing the use of commercial laminating resins. In this study a commercial laminating resin (Araldite LY5052/Aradur HY5052) is modified with propylene carbonate, a commercial reactive diluent, to reduce the resin’s refractive index. It is shown that this system is capable of identifying and locating an impact and quantifying the extent of damage within a composite.

  16. Investigations on the SR method growth, etching, birefringence, laser damage threshold and dielectric characterization of sodium acid phthalate single crystals

    NASA Astrophysics Data System (ADS)

    Senthil, A.; Ramasamy, P.; Verma, Sunil

    2011-03-01

    Optically good quality semi-organic single crystal of sodium acid phthalate (NaAP) was successfully grown by Sankaranarayanan-Ramasamy (SR) method. Transparent, colourless <0 0 1> oriented unidirectional bulk single crystals of diameters 10 and 20 mm and length maximum up to 75 mm were grown by the SR method. The grown crystals were subjected to various characterization studies such as etching, birefringence, laser damage threshold, UV-vis spectrum and dielectric measurement. The value of birefringence and quality were ascertained by birefringence studies.

  17. Optical Characterization of Window Materials for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Tedjojuwono, Ken K.; Clark, Natalie; Humphreys, William M., Jr.

    2013-01-01

    An optical metrology laboratory has been developed to characterize the optical properties of optical window materials to be used for aerospace applications. Several optical measurement systems have been selected and developed to measure spectral transmittance, haze, clarity, birefringence, striae, wavefront quality, and wedge. In addition to silica based glasses, several optical lightweight polymer materials and transparent ceramics have been investigated in the laboratory. The measurement systems and selected empirical results for non-silica materials are described. These measurements will be used to form the basis of acceptance criteria for selection of window materials for future aerospace vehicle and habitat designs.

  18. Orbital Debris Characterization via Laboratory Optical Measurements

    NASA Technical Reports Server (NTRS)

    Cowardin, Healther

    2011-01-01

    Optical observations of orbital debris offer insights that differ from radar measurements (specifically the size parameter,wavelength regime,and altitude range). For example, time-dependent photometric data yield lightcurves in multiple bandpasses that aid in material identification and possible periodic orientations. These data can also be used to help identify shapes and optical properties at multiple phase angles. Capitalizing on optical data products and applying them to generate a more complete understanding of orbital objects is a key objective of NASA's Optical Measurement Program, and the primary reason for the creation of the Optical Measurements Center(OMC). The OMC attempts to emulate space-based illumination conditions using equipment and techniques that parallel telescopic observations and source-target-sensor orientations.

  19. Nanosecond laser damage resistance of differently prepared semi-finished parts of optical multimode fibers

    NASA Astrophysics Data System (ADS)

    Mann, Guido; Vogel, Jens; Preuß, Rüdiger; Vaziri, Pouya; Zoheidi, Mohammadali; Eberstein, Markus; Krüger, Jörg

    2007-12-01

    Optical multimode fibers are applied in materials processing (e.g. automotive industry), defense, aviation technology, medicine and biotechnology. One challenging task concerning the production of multimode fibers is the enhancement of laser-induced damage thresholds. A higher damage threshold enables a higher transmitted average power at a given fiber diameter or the same power inside a thinner fiber to obtain smaller focus spots. In principle, different material parameters affect the damage threshold. Besides the quality of the preform bulk material itself, the drawing process during the production of the fiber and the preparation of the fiber end surfaces influence the resistance. Therefore, the change of the laser-induced damage threshold of preform materials was investigated in dependence on a varying thermal treatment and preparation procedure. Single and multi-pulse laser-induced damage thresholds of preforms (F300, Heraeus) were measured using a Q-switched Nd:YAG laser at 1064 nm wavelength emitting pulses with a duration of 15 ns, a pulse energy of 12 mJ and a repetition rate of 10 Hz. The temporal and spatial shape of the laser pulses were controlled accurately. Laser-induced damage thresholds in a range from 150 J cm -2 to 350 J cm -2 were determined depending on the number of pulses applied to the same spot, the thermal history and the polishing quality of the samples, respectively.

  20. Characterization of Fiber Optic CMM Probe System

    SciTech Connect

    K.W.Swallow

    2007-05-15

    This report documents a study completed on the fiber optic probe system that is a part of the Werth optical CMM. This study was necessary due to a lack of documentation from the vendor for the proper use and calibration of the fiber probe, and was performed in support of the Lithographie Galvanoformung Abformung (LIGA) development program at the FM&T. As a result of this study, a better understanding of the fiber optic probe has been developed, including guidelines for its proper use and calibration.

  1. A comprehensive model of catastrophic optical-damage in broad-area laser diodes

    NASA Astrophysics Data System (ADS)

    Chin, A. K.; Bertaska, R. K.; Jaspan, M. A.; Flusberg, A. M.; Swartz, S. D.; Knapczyk, M. T.; Petr, R.; Smilanski, I.; Jacob, J. H.

    2009-02-01

    The present model of formation and propagation of catastrophic optical-damage (COD), a random failure-mode in laser diodes, was formulated in 1974 and has remained substantially unchanged. We extend the model of COD phenomena, based on analytical studies involving EBIC (electron-beam induced current), STEM (scanning transmission-electron microscopy) and sophisticated optical-measurements. We have determined that a ring-cavity mode, whose presence has not been previously reported, significantly contributes to COD initiation and propagation in broad-area laser-diodes.

  2. Optical characterization of anti reflective sol-gel coatings fabricated using dip coating method

    NASA Astrophysics Data System (ADS)

    Melninkaitis, A.; Juškevičius, K.; Maciulevičius, M.; Sirutkaitis, V.; Beganskienė, A.; Kazadojev, I.; Kareiva, A.; Perednis, D.

    2007-01-01

    In recent years, there has been a growing interest in further development of sol-gel method which can produce ceramics and glasses using chemical precursors at relative low-temperatures. The applications for sol-gel derived products are numerous. Department of General and Inorganic Chemistry with Laser Research Center of Vilnius University and Institute of Physics continues an ongoing research effort on the synthesis, deposition and characterization of porous solgel. Our target is highly optically resistant anti-reflective (AR) coatings for general optics and nonlinear optical crystals. In order to produce AR coatings a silica (SiO II) sol-gel has been dip coated on the set of fused silica substrates. The optical properties and structure of AR-coatings deposited from hydrolysed tetraethylorthosilicate (TEOS) sol were characterized in detail in this study. The influence of different parameters on the formation of colloidal silica antireflective coatings by dip-coating technique has been investigated. All samples were characterized performing, transmission electron microscopy, UV-visible spectroscopy, atomic force microscopy, ellipsometric, total scattering and laser-induced damage threshold measurements. Herewith we present our recent results on synthesis of sol-gel solvents, coating fabrication and characterization of their optical properties.

  3. High-damage-threshold static laser beam shaping using optically patterned liquid-crystal devices.

    PubMed

    Dorrer, C; Wei, S K-H; Leung, P; Vargas, M; Wegman, K; Boulé, J; Zhao, Z; Marshall, K L; Chen, S H

    2011-10-15

    Beam shaping of coherent laser beams is demonstrated using liquid crystal (LC) cells with optically patterned pixels. The twist angle of a nematic LC is locally set to either 0 or 90° by an alignment layer prepared via exposure to polarized UV light. The two distinct pixel types induce either no polarization rotation or a 90° polarization rotation, respectively, on a linearly polarized optical field. An LC device placed between polarizers functions as a binary transmission beam shaper with a highly improved damage threshold compared to metal beam shapers. Using a coumarin-based photoalignment layer, various devices have been fabricated and tested, with a measured single-shot nanosecond damage threshold higher than 30 J/cm2. PMID:22002377

  4. A visibility characterization program for optical communications through the atmosphere

    NASA Technical Reports Server (NTRS)

    Cowles, K.

    1989-01-01

    A program is described for characterizing the atmosphere as it affects optical communications from a spacecraft. Cloud cover patterns and optical transmission will be determined by setting up three automated observatories in the Southwestern United States. Methods of site selection and operation of hardware and software components are presented, as well as plans for term deployment.

  5. Interferometric characterization of joint optical tables

    NASA Astrophysics Data System (ADS)

    Corzo-Garcia, S. C.; Medina-Lopez, R. J.; Anderson, S.; Carriles, R.; Ruiz-Marquez, A.; Castro-Camus, E.

    2011-08-01

    We present a straight forward and practical method for joining pneumatically floated optical tables with no previous preparation. In order to demonstrate this method we joined two optical tables in an uncentered "T-shape" using twenty four stainless steel plates (SSP), and used a Michelson interferometer to compare the stability of the entire "T"-structure versus one of its parts alone, finding that they both show similar rigidity. We also evaluated the performance of two different master-salve leg configurations by calculating the stress on the joint and confirmed the calculations by Michelson interferometry. In terms of floor vibration damping, it was observed that the performance of the system for the joined "T"-table seemed to be comparable to that of a single segment. This method can significantly reduce costs of large optical tables and will be useful to extend existing optical tables without manufacturer modification.

  6. Characterization of corrosion damage in prestressed concrete using acoustic emission

    NASA Astrophysics Data System (ADS)

    Mangual, Jesé; ElBatanouny, Mohamed K.; Vélez, William; Ziehl, Paul; Matta, Fabio; González, Miguel

    2012-04-01

    The corrosion of reinforced concrete structures is a major issue from both a structural safety and maintenance management point of view. Early detection of the internal degradation process provides the owner with sufficient options to develop a plan of action. An accelerated corrosion test was conducted in a small scale concrete specimen reinforced with a 0.5 inch (13 mm) diameter prestressing strand to investigate the correlation between corrosion rate and acoustic emission (AE). Corrosion was accelerated in the laboratory by supplying anodic current via a rectifier while continuously monitoring acoustic emission activity. Results were correlated with traditional electrochemical techniques such as half-cell potential and linear polarization. The location of the active corrosion activity was found through a location algorithm based on time of flight of the stress waves. Intensity analysis was used to plot the relative significance of the damage states present in the specimen and a preliminary grading chart is presented. Results indicate that AE may be a useful non-intrusive technique for the detection and quantification of corrosion damage.

  7. Characterization of swift heavy ion irradiation damage in ceria

    SciTech Connect

    Yablinsky, Clarissa A.; Devanathan, Ram; Pakarinen, Janne; Gan, Jian; Severin, Daniel; Trautmann, Christina; Allen, Todd R.

    2015-03-04

    Swift heavy ion induced radiation damage is investigated for ceria (CeO2), which serves as a UO2 fuel surrogate. Microstructural changes resulting from an irradiation with 940 MeV gold ions of 42 keV/nm electronic energy loss are investigated by means of electron microscopy accompanied by electron energy loss spectroscopy showing that there exists a small density reduction in the ion track core. While chemical changes in the ion track are not precluded, evidence of them was not observed. Classical molecular dynamics simulations of thermal spikes in CeO2 with an energy deposition of 12 and 36 keV/nm show damage consisting of isolated point defects at 12 keV/nm, and defect clusters at 36 keV/nm, with no amorphization at either energy. Furthermore, inferences are drawn from modeling about density changes in the ion track and the formation of interstitial loops that shed light on features observed by electron microscopy of swift heavy ion irradiated ceria.

  8. Characterization of Damage in Triaxial Braid Composites Under Tensile Loading

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.; Binienda, Wieslaw K.; Roberts, Gary D.; Goldberg, Robert K.

    2009-01-01

    Carbon fiber composites utilizing flattened, large tow yarns in woven or braided forms are being used in many aerospace applications. Their complex fiber architecture and large unit cell size present challenges in both understanding deformation processes and measuring reliable material properties. This report examines composites made using flattened 12k and 24k standard modulus carbon fiber yarns in a 0 /+60 /-60 triaxial braid architecture. Standard straight-sided tensile coupons are tested with the 0 axial braid fibers either parallel with or perpendicular to the applied tensile load (axial or transverse tensile test, respectively). Nonuniform surface strain resulting from the triaxial braid architecture is examined using photogrammetry. Local regions of high strain concentration are examined to identify where failure initiates and to determine the local strain at the time of initiation. Splitting within fiber bundles is the first failure mode observed at low to intermediate strains. For axial tensile tests splitting is primarily in the 60 bias fibers, which were oriented 60 to the applied load. At higher strains, out-of-plane deformation associated with localized delamination between fiber bundles or damage within fiber bundles is observed. For transverse tensile tests, the splitting is primarily in the 0 axial fibers, which were oriented transverse to the applied load. The initiation and accumulation of local damage causes the global transverse stress-strain curves to become nonlinear and causes failure to occur at a reduced ultimate strain. Extensive delamination at the specimen edges is also observed.

  9. Characterization of swift heavy ion irradiation damage in ceria

    SciTech Connect

    Yablinsky, Clarissa A.; Devanathan, Ram; Pakarinen, Janne; Gan, Jian; Severin, Daniel; Trautmann, Christina; Allen, Todd R.

    2015-03-04

    Swift heavy ion induced radiation damage is investigated for ceria (CeO2), which serves as a UO2 fuel surrogate. Microstructural changes resulting from an irradiation with 940 MeV gold ions of 42 keV/nm electronic energy loss are investigated by means of electron microscopy accompanied by electron energy loss spectroscopy showing that there exists a small density reduction in the ion track core. While chemical changes in the ion track are not precluded, evidence of them was not observed. Classical molecular dynamics simulations of thermal spikes in CeO2 with an energy deposition of 12 and 36 keV/nm show damage consisting of isolated point defects at 12 keV/nm, and defect clusters at 36 keV/nm, with no amorphization at either energy. Inferences are drawn from modeling about density changes in the ion track and the formation of interstitial loops that shed light on features observed by electron microscopy of swift heavy ion irradiated ceria.

  10. Characterization of swift heavy ion irradiation damage in ceria

    DOE PAGESBeta

    Yablinsky, Clarissa A.; Devanathan, Ram; Pakarinen, Janne; Gan, Jian; Severin, Daniel; Trautmann, Christina; Allen, Todd R.

    2015-03-04

    Swift heavy ion induced radiation damage is investigated for ceria (CeO2), which serves as a UO2 fuel surrogate. Microstructural changes resulting from an irradiation with 940 MeV gold ions of 42 keV/nm electronic energy loss are investigated by means of electron microscopy accompanied by electron energy loss spectroscopy showing that there exists a small density reduction in the ion track core. While chemical changes in the ion track are not precluded, evidence of them was not observed. Classical molecular dynamics simulations of thermal spikes in CeO2 with an energy deposition of 12 and 36 keV/nm show damage consisting of isolatedmore » point defects at 12 keV/nm, and defect clusters at 36 keV/nm, with no amorphization at either energy. Furthermore, inferences are drawn from modeling about density changes in the ion track and the formation of interstitial loops that shed light on features observed by electron microscopy of swift heavy ion irradiated ceria.« less

  11. Wavelength dependence of femtosecond laser-induced damage threshold of optical materials

    SciTech Connect

    Gallais, L. Douti, D.-B.; Commandré, M.; Batavičiūtė, G.; Pupka, E.; Ščiuka, M.; Smalakys, L.; Sirutkaitis, V.; Melninkaitis, A.

    2015-06-14

    An experimental and numerical study of the laser-induced damage of the surface of optical material in the femtosecond regime is presented. The objective of this work is to investigate the different processes involved as a function of the ratio of photon to bandgap energies and compare the results to models based on nonlinear ionization processes. Experimentally, the laser-induced damage threshold of optical materials has been studied in a range of wavelengths from 1030 nm (1.2 eV) to 310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system. Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1 to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damage threshold with the bandgap and photon energy. A model based on the Keldysh photo-ionization theory and the description of impact ionization by a multiple-rate-equation system is used to explain the dependence of laser-breakdown with the photon energy. The calculated damage fluence threshold is found to be consistent with experimental results. From these results, the relative importance of the ionization processes can be derived depending on material properties and irradiation conditions. Moreover, the observed damage morphologies can be described within the framework of the model by taking into account the dynamics of energy deposition with one dimensional propagation simulations in the excited material and thermodynamical considerations.

  12. Collagen remodeling in photo-thermal damaged skin with optical coherence tomography and multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Wu, Shu-lian; Li, Hui; Zhang, Xiao-man; Yu, Lili

    2009-08-01

    Cutaneous photo-thermal damage is the common damages in clinical medicine; it is a complex and dynamic process that follows an orderly sequence of events. The sequence can be roughly divided into three distinct, yet sequentially overlapping phases-inflammation, granulation tissue formation, and tissue remodeling. Characteristic structural changes associated with each phase could provide a basis for photo-thermal damage assessment with imaging technologies. Monitoring the skin tissue response during the skin after irradiated by laser and tracing the process of skin remodeling would help to understand the mechanism of photo-thermal. Optical coherence tomography (OCT) and multiphoton microscopy (MPM) imaging were used to observe the process of the collagen remodeling in mouse dermis photo-thermal injured which after irradiated by intense pulsed light source (IPLs) in this paper. Our finding showed that the OCT and MPM techniques can image the process of collagen remodeling in mouse dermis.

  13. Influence of oil contamination on the optical performance and laser induced damage of fused silica

    NASA Astrophysics Data System (ADS)

    Yang, L.; Xiang, X.; Miao, X. X.; Li, Z. J.; Li, L.; Yuan, X. D.; Zhou, G. R.; Lv, H. B.; Zu, X. T.

    2015-12-01

    The influence of oil contamination on the optical performance of fused silica and laser induced damage threshold (LIDT) at 355 nm is studied. The liquid vacuum oil is artificially spun on the fused silica surface. Optical microscopy and ultraviolet-visible (UV-vis) spectrophotometer are used to identify and understand the potential influence of oil contamination on the optical performance of fused silica. The results show that a large number of oil droplets are observed on the surface of fused silica after spin-coating, and the transmissivity of fused silica decreases with the increasing oil quantity. The LIDTs of fused silica decrease with the increasing oil mass for both on input and output surfaces at 355 nm, and the LIDT of fused silica with oil on input surface is lower than that on output surface at same contamination level. The damage mechanisms are also discussed by the photo-thermal measurement and three dimensional finite difference time domain (3D-FDTD) method. The experimental and simulated results show that the electric-field modulation by oil droplets, rather than its photo-thermal absorption, is mainly responsible for the oil contamination induced laser damage of fused silica.

  14. Characterization of the Los Alamos IPG YLR-6000 fiber laser using multiple optical paths and laser focusing optics

    SciTech Connect

    Milewski, John O; Bernal, John E

    2009-01-01

    Fiber laser technology has been identified as the replacement power source for the existing Los Alamos TA-55 production laser welding system. An IPG YLR-6000 fiber laser was purchased, installed at SM-66 R3, and accepted in February 2008. No characterization of the laser and no welding was performed in the Feb 2008 to May 2009 interval. T. Lienert and J. Bernal (Ref. 1, July 2009) determined the existing 200 mm Rofin collimator and focus heads used with the Rofin diode pumped lasers were inadequate for use with the IPG laser due to clipping of the IPG laser beam. Further efforts in testing of the IPG laser with Optoskand fiber delivery optics and a Rofin 120 mm collimator proved problematic due to optical fiber damage. As a result, IPG design optical fibers were purchased as replacements for subsequent testing. Within the same interval, an IPG fiber-to-fiber (F2F) connector, custom built for LANL, (J. Milewski, S. Gravener, Ref.2) was demonstrated and accepted at IPG Oxford, MA in August 2009. An IPG service person was contracted to come to LANL to assist in the installation, training, troubleshooting and characterization of the multiple beam paths and help perform laser head optics characterization. The statement of work is provided below: In summary the laser system, optical fibers, F2F connector, Precitec head, and a modified Rofin type (w/120mm Optoskand collimator) IWindowIBoot system focus head (Figure 1) were shown to perform well at powers up to 6 kW CW. Power measurements, laser spot size measurements, and other characterization data and lessons learned are contained within this report. In addition, a number of issues were identified that will require future resolution.

  15. Sub-surface damage issues for effective fabrication of large optics

    NASA Astrophysics Data System (ADS)

    Tonnellier, X.; Shore, P.; Morantz, P.; Baldwin, A.; Walker, D.; Yu, G.; Evans, R.

    2008-07-01

    A new ultra precision large optics grinding machine, BoX® has been developed at Cranfield University. BoX® is located at the UK's Ultra Precision Surfaces laboratory at the OpTIC Technium. This machine offers a rapid and economic solution for grinding large off-axis aspherical and free-form optical components. This paper presents an analysis of subsurface damage assessments of optical ground materials produced using diamond resin bonded grinding wheels. The specific materials used, Zerodur® and ULE® are currently under study for making extremely large telescope (ELT) segmented mirrors such as in the E-ELT project. The grinding experiments have been conducted on the BoX® grinding machine using wheels with grits sizes of 76 μm, 46 μm and 25 μm. Grinding process data was collected using a Kistler dynamometer platform. The highest material removal rate (187.5 mm3/s) used ensures that a 1 metre diameter optic can be ground in less than 10 hours. The surface roughness and surface profile were measured using a Form Talysurf. The subsurface damage was revealed using a sub aperture polishing process in combination with an etching technique. These results are compared with the targeted form accuracy of 1 μm p-v over a 1 metre part, surface roughness of 50-150 nm RMS and subsurface damage in the range of 2-5 μm. This process stage was validated on a 400 mm ULE® blank and a 1 metre hexagonal Zerodur® part.

  16. Assessment of retinal ganglion cell damage in glaucomatous optic neuropathy: Axon transport, injury and soma loss.

    PubMed

    Nuschke, Andrea C; Farrell, Spring R; Levesque, Julie M; Chauhan, Balwantray C

    2015-12-01

    Glaucoma is a disease characterized by progressive axonal pathology and death of retinal ganglion cells (RGCs), which causes structural changes in the optic nerve head and irreversible vision loss. Several experimental models of glaucomatous optic neuropathy (GON) have been developed, primarily in non-human primates and, more recently and commonly, in rodents. These models provide important research tools to study the mechanisms underlying glaucomatous damage. Moreover, experimental GON provides the ability to quantify and monitor risk factors leading to RGC loss such as the level of intraocular pressure, axonal health and the RGC population. Using these experimental models we are able to gain a better understanding of GON, which allows for the development of potential neuroprotective strategies. Here we review the advantages and disadvantages of the relevant and most often utilized methods for evaluating axonal degeneration and RGC loss in GON. Axonal pathology in GON includes functional disruption of axonal transport (AT) and structural degeneration. Horseradish peroxidase (HRP), rhodamine-B-isothiocyanate (RITC) and cholera toxin-B (CTB) fluorescent conjugates have proven to be effective reporters of AT. Also, immunohistochemistry (IHC) for endogenous AT-associated proteins is often used as an indicator of AT function. Similarly, structural degeneration of axons in GON can be investigated via changes in the activity and expression of key axonal enzymes and structural proteins. Assessment of axonal degeneration can be measured by direct quantification of axons, qualitative grading, or a combination of both methods. RGC loss is the most frequently quantified variable in studies of experimental GON. Retrograde tracers can be used to quantify RGC populations in rodents via application to the superior colliculus (SC). In addition, in situ IHC for RGC-specific proteins is a common method of RGC quantification used in many studies. Recently, transgenic mouse models

  17. Highly automated optical characterization with FTIR spectrometry

    NASA Technical Reports Server (NTRS)

    Perry, G. L. E.; Szofran, F. R.

    1989-01-01

    The procedure for evaluating the characteristics of II-VI semiconducting infrared sensor materials with a Fourier Transform Infrared (FTIR) spectrometer system will be discussed. While the method of mapping optical characteristics with a spectrometer has been employed previously, this system is highly automated compared to other systems where the optical transmission data are obtained using a FTIR system with a small stationary aperture in the optical path and moving the specimen behind the aperture. The hardware and software, including an algorithm developed for extracting cut-on wavelengths of spectra, as well as several example results, are described to illustrate the advanced level of the system. Additionally, data from transverse slices and longitudinal wafers of the aforementioned semiconductors will be used to show the accuracy of the system in predicting trends in materials such as shapes of growth interfaces and compositional uniformity.

  18. Optical characterization of photolithographic metal grids

    NASA Astrophysics Data System (ADS)

    Osmer, Kurt A.; Jones, Mike I.

    1991-10-01

    Infrared window materials for modern military aircraft must simultaneously provide adequate optical performance and maintain stringent shielding levels for electromagnetic interference (EMI). Microscopic metal grids deposited on the surface of dielectric windows can provide the conductivity necessary for proper radio frequency or RF shielding. This paper will examine the optical impact of three grid patterns designed for EMI suppression. Transmission blockage and beam diffraction in the far-field have been measured and compared to predicted values. A discussion of durability under severe thermal and rain erosion environments is also included.

  19. Nonlinear nanoprobes for characterizing ultrafast optical near field

    NASA Astrophysics Data System (ADS)

    Li, Haifeng

    With the rapid development of ultrafast optics and nanophotonics, it is crucial to measure the spatiotemporal evolution of an ultrafast optical near field in nanometer spatial and femtosecond temporal resolution with minimal perturbation. Although near-field scanning optical microscopy (NSOM) can achieve nanoscale spatial resolution and various ultrashort pulse diagnostic tools can characterize femtosecond laser pulses, yet such capability to noninvasively characterize the nanoscale characteristics of femtosecond pulses in all three spatial dimensions remains elusive. In this dissertation, we developed different types of nonlinear optical probes to characterize ultrashort optical pulses. The nonlinear optical probe is composed of three parts, a silica fiber taper, a single nanowire bonded to the end of the fiber and nonlinear nanoparticles attached on the tip of the nanowire. The optical fiber taper can be readily mounted on a mechanical stage and served as a macroscopic interface for handling and positioning control. The single nanowire bridges the dimension gap between the nanocrystals and the fiber taper, and is critical for achieving large aspect ratio and hence minimizing optical scattering and perturbation. The nonlinear nanoparticles give rise to its capability to characterize ultrashort optical pulses. The unique fusion of nanoscale and nonlinear features in developed nonlinear optical probes provides the ability of probing ultrafast optical field in complex 3D microand nano- structures. The demonstration of such ability is crucial for understanding the interaction of ultrafast optical fields and nanoscale systems. The fabrication processes of the nonlinear optical probes are illustrated in detail and the optical properties of the probes are investigated. Two different types of nonlinear optical probes, two-photon fluorescent nanoprobes and Second HARmonic nanoProbes (SHARP), are fabricated. Interferometric autocorrelation measurements near the focal point

  20. Development of a multi-frequency diffuse photon density wave device for the characterization of tissue damage at multiple depths

    NASA Astrophysics Data System (ADS)

    Diaz, David; Weingarten, Michael S.; Neidrauer, Michael T.; Samuels, Joshua A.; Huneke, Richard B.; Kuzmin, Vladimir L.; Lewin, Peter A.; Zubkov, Leonid A.

    2014-02-01

    The ability to determine the depth and degree of cutaneous and subcutaneous tissue damage is critical for medical applications such as burns and pressure ulcers. The Diffuse Photon Density Wave (DPDW) methodology at near infrared wavelengths can be used to non-invasively measure the optical absorption and reduced scattering coefficients of tissue at depths of several millimeters. A multi-frequency DPDW system with one light source and one detector was constructed so that light is focused onto the tissue surface using an optical fiber and lens mounted to a digitally-controlled actuator which changes the distance between light source and detector. A variable RF generator enables the modulation frequency to be selected between 50 to 400MHz. The ability to digitally control both source-detector separation distance and modulation frequency allows for virtually unlimited number of data points, enabling precise selection of the volume and depth of tissue that will be characterized. Suspensions of Intralipid and india ink with known absorption and reduced scattering coefficients were used as optical phantoms to assess device accuracy. Solid silicon phantoms were formulated for stability testing. Standard deviations for amplitude and phase shift readings were found to be 0.9% and 0.2 degrees respectively, over a one hour period. The ability of the system to quantify tissue damage in vivo at multiple depths was tested in a porcine burn model.

  1. Optical characterization of vocal folds using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lüerßen, Kathrin; Lubatschowski, Holger; Radicke, Nicole; Ptok, Martin

    2006-02-01

    The current standard procedure to ensure the diagnosis, if tissue is malignant, is still an invasive one. Optical coherence tomography (OCT) is a new non-invasive method to investigate biological tissue. In this study OCT was used on porcine and on human vocal folds. The optical penetration depth of the used radiation is up to 2 mm. Three different OCT application systems were used. The first is a high resolution OCT, which works in contact mode. It was used to examine porcine vocal folds ex vivo. Porcine vocal folds were assigned to defined areas and examined by OCT in contact mode followed by traditional histo-morphological analysis. The second OCT is fiber based. It also works in contact mode. Images of human vocal folds were done in contact mode. They were compared with a typical histo-morphological image of a human vocal fold. The third application system works in non contact to the tissue. It was integrated in a conventional laryngoscope. Human vocal folds were examined in vivo. Single layers of the vocal folds could be distinguished from each other with all used systems. Pathological alterations could be seen. Imaging is possible in real time. General anaesthesia is not necessary. OCT makes it possible to get a view under the surface of the vocal fold without being invasive.

  2. Characterization of swift heavy ion irradiation damage in ceria

    SciTech Connect

    Yablinsky, Clarissa; Devanathan, Ram; Pakarinen, Janne; Gan, Jian; Severin, Daniel; Trautmann, Christina; Allen, T. R.

    2015-05-14

    We have examined microstructural evolution in irradiated ceria (CeO2) using swift heavy ion irradiation, electron microscopy, and atomistic simulation. CeO2, a UO2 fuel surrogate, was irradiated with gold ions at an energy of 1 GeV to fluences up to 1x1014 ions/cm2. Transmission electron microscopy accompanied by electron energy loss spectroscopy showed that the ion tracks were of similar size at all fluences, and that there was no chemical change in the ion track core. Classical molecular dynamics simulations of thermal spikes in CeO2 with energy deposition of 12 and 36 keV/nm show damage consisting of isolated point defects at the lower energy and defect clusters at 36 keV/nm, with no amorphization at either energy. Inferences are drawn from modeling about density changes in the ion track and the formation of interstitial loops that shed light on features observed by electron microscopy of swift heavy ion irradiated ceria.

  3. Ultrasonic characterization of formation damage: effect of particle sizes

    NASA Astrophysics Data System (ADS)

    Khan, M. A.; Mohammed, A. H.; Jilani, S. Z.; Menouar, H.; Al-Majed, A. A.

    2003-01-01

    Permeability of a geological formation such as an oil field can be altered locally during drilling operations through penetration of particulates from the drilling fluid into the formation pores. This can adversely affect the overall production rate by constricting the pores. The composition of these fluids, particularly the sizes of the particulates therein, can be critical from the point of view of controlling the extent of 'damage' to the formation. Using our recently reported ultrasonic mapping technique, we have investigated the depth of particle penetration as a function of particle size and contamination time. An important correlation is observed between the diameters of the 'mud' particles and the pore size distribution in the formation. It is further noted that a substantial layer of 'mud cake' is formed on the surface beyond a certain critical particle size and this subsequently acts as a filter allowing only some finer particles to continue penetrating into the formation. The results are discussed in the context of bridging action at the pores.

  4. Optical Characterization of Commercial Lithiated Graphite Battery Electrodes and in Situ Fiber Optic Evanescent Wave Spectroscopy.

    PubMed

    Ghannoum, AbdulRahman; Norris, Ryan C; Iyer, Krishna; Zdravkova, Liliana; Yu, Aiping; Nieva, Patricia

    2016-07-27

    Optical characterization of graphite anodes in lithium ion batteries (LIB) is presented here for potential use in estimating their state of charge (SOC). The characterization is based on reflectance spectroscopy of the anode of commercial LIB cells and in situ optical measurements using an embedded optical fiber sensor. The optical characterization of the anode using wavelengths ranging from 500 to 900 nm supports the dominance of graphite over the solid electrolyte interface in governing the anode's reflectance properties. It is demonstrated that lithiated graphite's reflectance has a significant change in the near-infrared band, 750-900 nm, compared with the visible spectrum as a function of SOC. An embedded optical sensor is used to measure the transmittance of graphite anode in the near-infrared band, and the results suggest that a unique inexpensive method may be developed to estimate the SOC of a LIB. PMID:27379859

  5. Low-velocity impact damage characterization of carbon fiber reinforced polymer (CFRP) using infrared thermography

    NASA Astrophysics Data System (ADS)

    Li, Yin; Zhang, Wei; Yang, Zheng-wei; Zhang, Jin-yu; Tao, Sheng-jie

    2016-05-01

    Carbon fiber reinforced polymer (CFRP) after low-velocity impact is detected using infrared thermography, and different damages in the impacted composites are analyzed in the thermal maps. The thermal conductivity under pulse stimulation, frictional heating and thermal conductivity under ultrasonic stimulation of CFRP containing low-velocity impact damage are simulated using numerical simulation method. Then, the specimens successively exposed to the low-velocity impact are respectively detected using the pulse infrared thermography and ultrasonic infrared thermography. Through the numerical simulation and experimental investigation, the results obtained show that the combination of the above two detection methods can greatly improve the capability for detecting and evaluating the impact damage in CFRP. Different damages correspond to different infrared thermal images. The delamination damage, matrix cracking and fiber breakage are characterized as the block-shape hot spot, line-shape hot spot,

  6. Effect of defects on long-pulse laser-induced damage of two kinds of optical thin films

    SciTech Connect

    Wang Bin; Qin Yuan; Ni Xiaowu; Shen Zhonghua; Lu Jian

    2010-10-10

    In order to study the effect of defects on the laser-induced damage of different optical thin films, we carried out damage experiments on two kinds of thin films with a 1ms long-pulse laser. Surface-defect and subsurface-defect damage models were used to explain the damage morphology. The two-dimensional finite element method was applied to calculate the temperature and thermal-stress fields of these two films. The results show that damages of the two films are due to surface and subsurface defects, respectively. Furthermore, the different dominant defects for thin films of different structures are discussed.

  7. Multi-Pulse Effects in the Damage to the LCLS Reflective Optics

    SciTech Connect

    Ryutov, D

    2004-07-29

    A number of experiments to be performed on the planned Linac Coherent Light Source (LCLS) will have to use various types of reflective optics (see, e.g., [1]). On the other hand, LCLS will operate at a rate of 120 x-ray pulses per second. Therefore, when considering effects leading to the damage to its optics, one has to be concerned not only with a possible damage within one pulse, but also with effects accumulating during many pulses. We identify and analyze two of such effects: a thermal fatigue, and the intensity-dependent radiation damage. The first effect is associated with thermal stresses and deformations that occur in every pulse. The heating of the surface layers of the optics leads to a peculiar distribution of stresses, with a strong concentration near the surface. The quasistatic analysis of this problem was presented in [2]. In the present study, we show that transients in both transverse and longitudinal acoustic perturbations play a significant role and generally worsen the situation. If the maximum stresses approach the yield strength, the thermal fatigue causes degradation of the surface within a few thousands pulses. The second effect is related to formation of clusters of ionized atoms which lead to gross deformation of the lattice and formation of numerous vacancies and interstitials. At maximum LCLS fluxes, the number of displacements per atom may reach values exceeding unity during a few hours of operation of LCLS, meaning degradation of reflective properties of the surface of the optics. We derive constraints on the admissible fluence per pulse and suggest ways for decreasing the impact of the multipulse effects.

  8. Optical Characterization of Single Plasmonic Nanoparticles

    PubMed Central

    Olson, Jana; Dominguez-Medina, Sergio; Hoggard, Anneli; Wang, Lin-Yung; Chang, Wei-Shun; Link, Stephan

    2015-01-01

    This tutorial review surveys the optical properties of plasmonic nanoparticles studied by various single particle spectroscopy techniques. The surface plasmon resonance of metallic nanoparticles depends sensitively on the nanoparticle geometry and its environment, with even relatively minor deviations causing significant changes in the optical spectrum. Because for chemically prepared nanoparticles a distribution of their size and shape is inherent, ensemble spectra of such samples are inhomogeneously broadened, hiding the properties of the individual nanoparticles. The ability to measure one nanoparticle at a time using single particle spectroscopy can overcome this limitation. This review provides an overview of different steady-state single particle spectroscopy techniques that provide detailed insight into the spectral characteristics of plasmonic nanoparticles. PMID:24979351

  9. Optical characterization of directly deposited graphene on a dielectric substrate.

    PubMed

    Kaplas, Tommi; Karvonen, Lasse; Ahmadi, Sepehr; Amirsolaimani, Babak; Mehravar, Soroush; Peyghambarian, Nasser; Kieu, Khanh; Honkanen, Seppo; Lipsanen, Harri; Svirko, Yuri

    2016-02-01

    By using scanning multiphoton microscopy we compare the nonlinear optical properties of the directly deposited and transferred to the dielectric substrate graphene. The direct deposition of graphene on oxidized silicon wafer was done by utilizing sacrificial copper catalyst film. We demonstrate that the directly deposited graphene and bi-layered transferred graphene produce comparable third harmonic signals and have almost the same damage thresholds. Therefore, we believe directly deposited graphene is suitable for the use of e.g. nanofabricated optical setups. PMID:26906863

  10. (Optical characterization techniques applied to ceramic oxides)

    SciTech Connect

    Abraham, M.M.

    1990-10-15

    The traveler collaborated with M.J.M. Leask, J.M. Baker, B. Bleaney, and others at the Clarendon Laboratory, Oxford University, Oxford, UK, to Study Tetragonal rare-earth phosphates and vanadates by optical and magnetic spectroscopy. This work is related to similar studies that have been performed at ORNL by the Synthesis and Properties of Novel Materials Group in the Solid State Division.

  11. Optimization of radiation damage to proteins using X-ray nanofocusing optics

    NASA Astrophysics Data System (ADS)

    Boularaoui, Selwa; Evans-Lutterodt, K.; Lee, S.; Isakovic, A. F.

    2013-03-01

    The need to understand protein structure and perform treatment lead to the use of X-ray and particle-based radiation. Since the use of such radiation has undesirable side effects, mostly through the damage to proteins, it is important to continuously work on decreasing radiation damage. We outline the proposal to use the kinoform refractive optics to focus X-rays on the nanoscale to minimize the radiation damage to protein crystals under study. These optics devices are nanofabricated from low-Z elements (silicon, diamond) and can be used at synchrotron X-ray radiation facilities. We discuss the automated setup that performs nanopositioning of the nanofocusing element, and collects the chemical and structural protein solution under study. We offer simple mathematical models in irradiation and in treatment that help optimize the radiation parameters. This work is supported in part by Khalifa University IRF-Level 1 Fund. The work at BNL-NSLS is supported through US DOE, Office of Basic Energy Sciences.

  12. Multiple pulse thermal damage thresholds of materials for x-ray free electron laser optics investigated with an ultraviolet laser

    SciTech Connect

    Hau-Riege, Stefan P.; London, Richard A.; Bionta, Richard M.; Soufli, Regina; Ryutov, Dmitri; Shirk, Michael; Baker, Sherry L.; Smith, Patrick M.; Nataraj, Pradeep

    2008-11-17

    Optical elements to be used for x-ray free electron lasers (XFELs) must withstand multiple high-fluence pulses. We have used an ultraviolet laser to study the damage of two candidate materials, crystalline Si and B{sub 4}C-coated Si, emulating the temperature profile expected to occur in optics exposed to XFEL pulses. We found that the damage threshold for 10{sup 5} pulses is {approx}20% to 70% lower than the melting threshold.

  13. Impact damage detection system using small-diameter optical fiber sensors wavily embedded in CFRP laminate structures

    NASA Astrophysics Data System (ADS)

    Tsutsui, Hiroaki; Kawamata, Akio; Kimoto, Junichi; Isoe, Akira; Hirose, Yasuo; Sanda, Tomio; Takeda, Nobuo

    2003-08-01

    It is well known that barely visible damage is often induced in composite structures subjected to out-of plane impact, and the mechanical properties of the composites decrease markedly. In this study, some element technologies for the detection of the damage are explained. Those are (1) the technologies for the arrangement of embedded small-diameter optical fibers which have no serious effect on the mechanical properties of composites, (2) the technologies for the egress of the optical fibers using "the embedded connector for smart structures" which can be trimmed without care about the optical fibers, (3) the technologies for the damage detection system that has the functions for data acquisition and analysis, the evaluation of the initiation and the position of damage, and the visualization of damage information. The impact test using the composite airframe demonstrator is conducted. The sensors embedded in the upper panel of the stiffened cylindrical composite structure with 1.5 m in diameter and 3 m in length, are FBG sensors for strain measurement and the optical fibers for optical loss measurement. The detection of damage in the composite structures using a developed damage detection system is demonstrated.

  14. Acousto-ultrasonics-based fatigue damage characterization: Linear versus nonlinear signal features

    NASA Astrophysics Data System (ADS)

    Su, Zhongqing; Zhou, Chao; Hong, Ming; Cheng, Li; Wang, Qiang; Qing, Xinlin

    2014-03-01

    Engineering structures are prone to fatigue damage over service lifespan, entailing early detection and continuous monitoring of the fatigue damage from its initiation through growth. A hybrid approach for characterizing fatigue damage was developed, using two genres of damage indices constructed based on the linear and the nonlinear features of acousto-ultrasonic waves. The feasibility, precision and practicability of using linear and nonlinear signal features, for quantitatively evaluating multiple barely visible fatigue cracks in a metallic structure, was compared. Miniaturized piezoelectric elements were networked to actively generate and acquire acousto-ultrasonic waves. The active sensing, in conjunction with a diagnostic imaging algorithm, enabled quantitative evaluation of fatigue damage and facilitated embeddable health monitoring. Results unveiled that the nonlinear features of acousto-ultrasonic waves outperform their linear counterparts in terms of the detectability. Despite the deficiency in perceiving small-scale damage and the possibility of conveying false alarms, linear features show advantages in noise tolerance and therefore superior practicability. The comparison has consequently motivated an amalgamation of linear and nonlinear features of acousto-ultrasonic waves, targeting the prediction of multi-scale damage ranging from microscopic fatigue cracks to macroscopic gross damage.

  15. Damage on fused silica optics caused by laser ablation of surface-bound microparticles.

    PubMed

    Raman, Rajesh N; Demos, Stavros G; Shen, Nan; Feigenbaum, Eyal; Negres, Raluca A; Elhadj, Selim; Rubenchik, Alexander M; Matthews, Manyalibo J

    2016-02-01

    High peak power laser systems are vulnerable to performance degradation due to particulate contamination on optical surfaces. In this work, we show using model contaminant particles that their optical properties decisively determine the nature of the optical damage. Borosilicate particles with low intrinsic optical absorption undergo ablation initiating in their sub-surface, leading to brittle fragmentation, distributed plasma formation, material dispersal and ultimately can lead to micro-fractures in the substrate optical surface. In contrast, energy coupling into metallic particles is highly localized near the particle-substrate interface leading to the formation of a confined plasma and subsequent etching of the substrate surface, accompanied by particle ejection driven by the recoil momentum of the ablation plume. While the tendency to create fractured surface pitting from borosilicate is stochastic, the smooth ablation pits created by metal particles is deterministic, with pit depths scaling linearly with laser fluence. A simple model is employed which predicts ~3x electric field intensity enhancement from surface-bound fragments. In addition, our results suggest that the amount of energy deposited in metal particles is at least twice that in transparent particles. PMID:26906835

  16. Failure Analysis Study and Long-Term Reliability of Optical Assemblies with End-Face Damage

    NASA Technical Reports Server (NTRS)

    Kichak, Robert A.; Ott, Melanie N.; Leidecker, Henning W.; Chuska, Richard F.; Greenwell, Christopher J.

    2008-01-01

    In June 2005, the NESC received a multi-faceted request to determine the long term reliability of fiber optic termini on the ISS that exhibited flaws not manufactured to best workmanship practices. There was a lack of data related to fiber optic workmanship as it affects the long term reliability of optical fiber assemblies in a harsh environment. A fiber optic defect analysis was requested which would find and/or create various types of chips, spalls, scratches, etc., that were identified by the ISS personnel. Once the defects and causes were identified the next step would be to perform long term reliability testing of similar assemblies with similar defects. The goal of the defect analysis would be for the defects to be observed and documented for deterioration of fiber optic performance. Though this report mostly discusses what has been determined as evidence of poor manufacturing processes, it also concludes the majority of the damage could have been avoided with a rigorous process in place.

  17. Scintillating glass fiber neutron sensors: 1, Production and optical characterization

    SciTech Connect

    Abel, K.H.; Arthur, R.J.; Bliss, M.

    1993-10-01

    The production and optical characterization of cerium-doped lithium silicate scintillating fibers used as thermal neutron detectors are discussed. The bulk glass continuing enriched {sup 6}Li is produced starting from high-purity commercial materials which are further purified at Pacific Northwest Laboratory (PNL). The fibers are drawn at PNL in a hot down-draw process. The fibers are coated with a silicone polymer that serves as both an optical cladding and a physical buffer coat. Optical characterization has included measurements of light output as a function of glass composition, optical attenuation lengths, and fluorescence lifetimes. Fibers have been prepared in our laboratory with as-drawn attenuation lengths (l/e distance) in excess of 2 meters over sub-meter distances.

  18. Optical Metamaterials: Design, Characterization and Applications

    ERIC Educational Resources Information Center

    Chaturvedi, Pratik

    2009-01-01

    Artificially engineered metamaterials have emerged with properties and functionalities previously unattainable in natural materials. The scientific breakthroughs made in this new class of electromagnetic materials are closely linked with progress in developing physics-driven design, novel fabrication and characterization methods. The intricate…

  19. Optical fiber sensors for materials and structures characterization

    NASA Technical Reports Server (NTRS)

    Lindner, D. K.; Claus, R. O.

    1991-01-01

    The final technical report on Optical Fiber Sensors for Materials and Structures Characterization, covering the period August 1990 through August 1991 is presented. Research programs in the following technical areas are described; sapphire optical fiber sensors; vibration analysis using two-mode elliptical core fibers and sensors; extrinsic Fabry-Perot interferometer development; and coatings for fluorescent-based sensor. Research progress in each of these areas was substantial, as evidenced by the technical publications which are included as appendices.

  20. Optical Characterization of Natural Nontoxic Nanomaterials

    NASA Astrophysics Data System (ADS)

    Rao, Devulapalli; Yelleswarapu, Chandra

    2013-03-01

    Synthetic nanomaterials - carbon nanotubes, semiconductor nanoparticles, nanowires and nanorods, metal clusters in polymer films - are extensively studied for potential photonic applications. Naturally occurring halloysite nanotubes offer additional advantages of high tensile strength, nontoxcity and biocompatibility. Halloysite is receiving lot of attention for application as low cost nanoscale container for encapsulation of biologically active molecules, drugs, and anticorrosion agents. We studied the optical properties of halloysite nanotube samples of length ~1000 nm with 50 nm external diameter and 15 nm internal diameter. The hollysite sample was provided by Prof. Yuri Lvov, Institute for Micromanufacturing, Louisiana Tech. The sample suspended in water at a concentration 2.5 mg/ml exhibits a broad optical absorption band in the visible region with a peak ~600 nm. Z-scan studies are carried out, with 3 nsec laser pulses of frequency doubled Nd:YAG laser, using 1 mm glass cell containing the sample suspended in acetone at a concentration 0.66 mg/ml. Open aperture z-scan measurements indicate two-photon absorption. Closed aperture z-scan measurements exhibit a positive nonlinear refractive index. Results of photoacoustic z-scan currently in progress will also be presented.

  1. Optical measurements on overhead optical fiber cables for stresses and damage identification

    NASA Astrophysics Data System (ADS)

    Ravet, Fabien L.; Heens, Bernard; Daniaux, D.; Froidure, Jean-Christophe; Blondel, Michel; Dascotte, M.; Lots, P.

    1998-12-01

    This paper concerns the characterization of various trunks of an OPGW based network. No strong fiber aging has been observed but combined OTDR and PMD measurements have pointed out strong cable clamping at suspension pylon. Large local losses have been measured at both 1.55 micrometers and 1.6 micrometers and stress induced birefringent behavior have been experienced. PMD temporal evolution has also been studied. A correlation between temperature variation and PMD evolution has been observed.

  2. Aero-optical characterization of aircraft optical turrets by holography, interferometry and shadowgraph

    NASA Technical Reports Server (NTRS)

    Trolinger, J. D.

    1980-01-01

    Density variations in the aircraft boundary layer, turret wakes and shock waves create distortion of an optical wavefront through associated refractive index variations. Such effects can be observed directly through optical flow visualization. The application of holographic interferometry, wave shearing interferometry, and laser shadowgraph to observe and quantify such effects is described. Examples of the results from five different wind tunnel tests are presented. The examples show that diagnostics have provided valuable qualitiative and quantitiative data. These include (1) wake dimensions, (2) optical strength of the flow field, (3) turbulence characterization, (4) shock location, and (5) direct observation of areo-optical effects.

  3. Sequential description of the catastrophic optical damage of high power laser diodes

    NASA Astrophysics Data System (ADS)

    Souto, J.; Pura, J. L.; Torres, A.; Jiménez, J.; Bettiati, M.; Laruelle, F. J.

    2016-03-01

    Cathodoluminescence (CL) analysis of high power laser diodes permits to reveal the main defects issued from the catastrophic optical degradation (COD). These defects are revealed as discontinuous dark lines along the ridge. The different levels of damage are analysed, and a thermomechanical model taking account of the thermal and mechanical properties of the laser structure is settled up. In this model the COD is described as a local temperature enhancement, which generates thermal stresses leading to the generation of dislocations, which are responsible for the degradation of the thermal conductivity of the of the active zone of the laser.

  4. Time-resolved analysis of catastrophic optical damage in 975 nm emitting diode lasers

    NASA Astrophysics Data System (ADS)

    Hempel, Martin; Ziegler, Mathias; Tomm, Jens W.; Elsaesser, Thomas; Michel, Nicolas; Krakowski, Michel

    2010-06-01

    Catastrophic optical damage (COD) is analyzed during single current pulse excitation of 975 nm emitting diode lasers. Power transients and thermal images are monitored during each pulse. The COD process is unambiguously related to the occurrence of a "thermal flash" of Planck's radiation. We observe COD to ignite multiple times in subsequent pulses. Thermography allows for tracing a spatial motion of the COD site on the front facet of the devices. The time constant of power decay after the onset of COD has values from 400 to 2000 ns, i.e., an order of magnitude longer than observed for shorter-wavelength devices.

  5. Optical characterization of ultra-sensitive TES bolometers for SAFARI

    NASA Astrophysics Data System (ADS)

    Audley, Michael D.; de Lange, Gerhard; Gao, Jian-Rong; Khosropanah, Pourya; Mauskopf, Philip D.; Morozov, Dmitry; Trappe, Neil A.; Doherty, Stephen; Withington, Stafford

    2014-07-01

    We have characterized the optical response of prototype detectors for SAFARI, the far-infrared imaging spectrometer for the SPICA satellite. SAFARI's three bolometer arrays will image a 2'×2' field of view with spectral information over the wavelength range 34—210 μm. SAFARI requires extremely sensitive detectors (goal NEP ~ 0.2 aW/√Hz), with correspondingly low saturation powers (~5 fW), to take advantage of SPICA's cooled optics. We have constructed an ultra-low background optical test facility containing an internal cold black-body illuminator and have recently added an internal hot black-body source and a light-pipe for external illumination. We illustrate the performance of the test facility with results including spectral-response measurements. Based on an improved understanding of the optical throughput of the test facility we find an optical efficiency of 60% for prototype SAFARI detectors.

  6. Characterizing Damage of Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) in Blueberries.

    PubMed

    Wiman, Nik G; Parker, Joyce E; Rodriguez-Saona, Cesar; Walton, Vaughn M

    2015-06-01

    Brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a severe economic pest of growing importance in the United States, Canada, and Europe. While feeding damage from H. halys has been characterized in tree fruit, vegetables, and agronomic crops, less is known about the impacts of stink bugs on small fruits such as blueberries. In this study, we examined H. halys feeding on two representative early and late ripening blueberry cultivars in Oregon and New Jersey. This research examined how different densities of H. halys confined on blueberry clusters for week-long periods affected fruit quality at harvest. After fruit were ripe, we stained and quantified the number of salivary sheaths on berries as an indication of feeding pressure. Feeding by H. halys damaged the fruits by causing increased levels of external discoloration, and internal damage in the form of tissue necrosis. Exposure of berries to H. halys was also associated with decreasing berry weights and lower soluble solids in fruits. However, the different cultivars did not respond consistently to feeding pressure from H. halys. Weekly variability in feeding pressure of two of the cultivars as quantified by the number of stylet sheaths per berry was largely accounted for by environmental variables. We conclude that H. halys does have potential to severely damage blueberries and may become an important economic pest. Characterization of damage is important because correct identification of insect damage is key for successful management. PMID:26470241

  7. Optical sensing of the fatigue damage state of CFRP under realistic aeronautical load sequences.

    PubMed

    Zuluaga-Ramírez, Pablo; Arconada, Álvaro; Frövel, Malte; Belenguer, Tomás; Salazar, Félix

    2015-01-01

    We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others. PMID:25760056

  8. Optical Sensing of the Fatigue Damage State of CFRP under Realistic Aeronautical Load Sequences

    PubMed Central

    Zuluaga-Ramírez, Pablo; Arconada, Álvaro; Frövel, Malte; Belenguer, Tomás; Salazar, Félix

    2015-01-01

    We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others. PMID:25760056

  9. Surface damage correction, and atomic level smoothing of optics by Accelerated Neutral Atom Beam (ANAB) Processing

    NASA Astrophysics Data System (ADS)

    Walsh, M.; Chau, K.; Kirkpatrick, S.; Svrluga, R.

    2014-10-01

    Surface damage and surface contamination of optics has long been a source of problems for laser, lithography and other industries. Nano-sized surface defects may present significant performance issues in optical materials for deep UV and EUV applications. The effects of nanometer sized surface damage (scratches, pits, and organics) on the surface of optics made of traditional materials and new more exotic materials is a limiting factor to high end performance. Angstrom level smoothing of materials such as calcium fluoride, spinel, zinc sulfide, BK7 and others presents a unique set of challenges. Exogenesis Corporation, using its proprietary Accelerated Neutral Atom Beam (ANAB) technology, is able to remove nano-scale surface damage and contamination and leaves many material surfaces with roughness typically around one angstrom. This process technology has been demonstrated on nonlinear crystals, and various other high-end optical materials. This paper describes the ANAB technology and summarizes smoothing results for various materials that have been processed with ANAB. All surface measurement data for the paper was produced via AFM analysis. Exogenesis Corporation's ANAB processing technology is a new and unique surface modification technique that has demonstrated to be highly effective at correcting nano-scale surface defects. ANAB is a non-contact vacuum process comprised of an intense beam of accelerated, electrically neutral gas atoms with average energies of a few tens of electron volts. The ANAB process does not apply normal forces associated with traditional polishing techniques. ANAB efficiently removes surface contaminants, nano-scale scratches, bumps and other asperities under low energy physical sputtering conditions as the removal action proceeds. ANAB may be used to remove a precisely controlled, uniform thickness of material without any increase of surface roughness, regardless of the total amount of material removed. The ANAB process does not

  10. Alternating Current Stimulation for Vision Restoration after Optic Nerve Damage: A Randomized Clinical Trial

    PubMed Central

    Schittkowski, Michael P.; Antal, Andrea; Ambrus, Géza Gergely; Paulus, Walter; Dannhauer, Moritz; Michalik, Romualda; Mante, Alf; Bola, Michal; Lux, Anke; Kropf, Siegfried; Brandt, Stephan A.; Sabel, Bernhard A.

    2016-01-01

    Background Vision loss after optic neuropathy is considered irreversible. Here, repetitive transorbital alternating current stimulation (rtACS) was applied in partially blind patients with the goal of activating their residual vision. Methods We conducted a multicenter, prospective, randomized, double-blind, sham-controlled trial in an ambulatory setting with daily application of rtACS (n = 45) or sham-stimulation (n = 37) for 50 min for a duration of 10 week days. A volunteer sample of patients with optic nerve damage (mean age 59.1 yrs) was recruited. The primary outcome measure for efficacy was super-threshold visual fields with 48 hrs after the last treatment day and at 2-months follow-up. Secondary outcome measures were near-threshold visual fields, reaction time, visual acuity, and resting-state EEGs to assess changes in brain physiology. Results The rtACS-treated group had a mean improvement in visual field of 24.0% which was significantly greater than after sham-stimulation (2.5%). This improvement persisted for at least 2 months in terms of both within- and between-group comparisons. Secondary analyses revealed improvements of near-threshold visual fields in the central 5° and increased thresholds in static perimetry after rtACS and improved reaction times, but visual acuity did not change compared to shams. Visual field improvement induced by rtACS was associated with EEG power-spectra and coherence alterations in visual cortical networks which are interpreted as signs of neuromodulation. Current flow simulation indicates current in the frontal cortex, eye, and optic nerve and in the subcortical but not in the cortical regions. Conclusion rtACS treatment is a safe and effective means to partially restore vision after optic nerve damage probably by modulating brain plasticity. This class 1 evidence suggests that visual fields can be improved in a clinically meaningful way. Trial Registration ClinicalTrials.gov NCT01280877 PMID:27355577

  11. Continuous-wave laser damage and conditioning of particle contaminated optics.

    PubMed

    Brown, Andrew; Ogloza, Albert; Taylor, Lucas; Thomas, Jeff; Talghader, Joseph

    2015-06-01

    This paper describes the physical processes that occur when high-power continuous-wave laser light interacts with absorbing particles on a low-absorption optical surface. When a particulate-contaminated surface is illuminated by high-power continuous-wave laser light, a short burst of light is emitted from the surface, and the particles rapidly heat over a period of milliseconds to thousands of degrees Celsius, migrating over and evaporating from the surface. The surviving particles tend to coalesce into larger ones and leave a relatively flat residue on the surface. The total volume of the material on the surface has decreased dramatically. The optical surface itself heats substantially during illumination, but the surface temperature can decrease as the material is evaporated. Optical surfaces that survive this process without catastrophic damage are found to be more resistant to laser damage than surfaces that have not undergone the process. The surface temperature of the conditioned surfaces under illumination is lower than that of unconditioned surfaces. These conditioning effects on particles occurred within the first 30 s of laser exposure, with subsequent laser shots not affecting particle distributions. High-speed photography showed the actual removal and agglomeration of individual particles to occur within about 0.7 ms. Elemental changes were measured using time-of-flight secondary ion mass spectroscopy, with conditioned residuals being higher in hydrocarbon content than pristine particles. The tests in this study were conducted on high-reflectivity distributed Bragg reflector coated optics with carbon microparticles in the size range of 20-50 μm, gold particles of size 250 nm, and silica 1 μm in size. PMID:26192686

  12. Combined Advanced Finishing and UV-Laser Conditioning for Producing UV-Damage-Resistant Fused Silica Optics

    SciTech Connect

    Menapace, J A; Penetrante, B; Golini, D; Slomba, A; Miller, P E; Parham, T; Nichols, M; Peterson, J

    2001-11-01

    Laser induced damage initiation on fused silica optics can limit the lifetime of the components when used in high power UV laser environments. Foe example in inertial confinement fusion research applications, the optics can be exposed to temporal laser pulses of about 3-nsec with average fluences of 8 J/cm{sup 2} and peak fluences between 12 and 15 J/cm{sup 2}. During the past year, we have focused on optimizing the damage performance at a wavelength of 355-nm (3{omega}), 3-nsec pulse length, for optics in this category by examining a variety of finishing technologies with a challenge to improve the laser damage initiation density by at least two orders of magnitude. In this paper, we describe recent advances in improving the 3{omega} damage initiation performance of laboratory-scale zirconium oxide and cerium oxide conventionally finished fused silica optics via application of processes incorporating magnetorheological finishing (MRF), wet chemical etching, and UV laser conditioning. Details of the advanced finishing procedures are described and comparisons are made between the procedures based upon large area 3{omega} damage performance, polishing layer contamination, and optical subsurface damage.

  13. Experimental characterization and numerical modelling of polymeric film damage, constituting the stratospheric super pressurized balloons

    NASA Astrophysics Data System (ADS)

    Chaabane, Makram; Chaabane, Makram; Dalverny, Olivier; Deramecourt, Arnaud; Mistou, Sébastien

    The super-pressure balloons developed by CNES are a great challenge in scientific ballooning. Whatever the balloon type considered (spherical, pumpkin...), it is necessary to have good knowledge of the mechanical behavior of the envelope regarding to the flight level and the lifespan of the balloon. It appears during the working stages of the super pressure balloons that these last can exploded prematurely in the course of the first hours of flight. For this reason CNES and LGP are carrying out research programs about experimentations and modelling in order to predict a good stability of the balloons flight and guarantee a life time in adequacy with the technical requirement. This study deals with multilayered polymeric film damage which induce balloons failure. These experimental and numerical study aims, are a better understanding and predicting of the damage mechanisms bringing the premature explosion of balloons. The following damages phenomena have different origins. The firsts are simple and triple wrinkles owed during the process and the stocking stages of the balloons. The second damage phenomenon is associated to the creep of the polymeric film during the flight of the balloon. The first experimental results we present in this paper, concern the mechanical characterization of three different damage phenomena. The severe damage induced by the wrinkles of the film involves a significant loss of mechanical properties. In a second part the theoretical study, concerns the choice and the development of a non linear viscoelastic coupled damage behavior model in a finite element code.

  14. Performance optimization of a diagnostic system based upon a simulated strain field for fatigue damage characterization

    NASA Astrophysics Data System (ADS)

    Sbarufatti, C.; Manes, A.; Giglio, M.

    2013-11-01

    The work presented hereafter is about the development of a diagnostic system for crack damage detection, localization and quantification on a typical metallic aeronautical structure (skin stiffened through riveted stringers). Crack detection and characterization are based upon strain field sensitivity to damage. The structural diagnosis is carried out by a dedicated smart algorithm (Artificial Neural Network) which is trained on a database of Finite Element simulations relative to damaged and undamaged conditions, providing the system with an accurate predictor at low overall cost. The algorithm, trained on numerical damage experience, is used in a simulated environment to provide reliable preliminary information concerning the algorithm performances for damage diagnosis, thus further reducing the experimental costs and efforts associated with the development and optimization of such systems. The same algorithm has been tested on real experimental strain patterns acquired during real fatigue crack propagation, thus verifying the capability of the numerically trained algorithm for anomaly detection, damage assessment and localization on a real complex structure. The load variability, the discrepancy between the Finite Element Model and the real structure, and the uncertainty in the algorithm training process have been addressed in order to enhance the robustness of the system inference process. Some further algorithm training strategies are discussed, aimed at minimizing the risk for false alarms while maintaining a high probability of damage detection.

  15. Characterization of creep and creep damage by in-situ microtomography

    NASA Astrophysics Data System (ADS)

    Borbély, András; Dzieciol, Krzysztof; Sket, Federico; Isaac, Augusta; di Michiel, Marco; Buslaps, Thomas; Kaysser-Pyzalla, Anke R.

    2011-07-01

    Application of in-situ microtomography to characterization of power law creep and creep damage in structural materials is presented. It is shown first that the successively reconstructed volumes are adequately monitoring the macroscopic sample shape and that microtomography is an optimal tool to characterize inhomogeneous specimen deformation. Based on a two-step image correlation technique the evolution of single voids is revealed and the basis of a pioneering approach to creep damage studies is presented. The method allows the unequivocal separation of three concurrent damage mechanisms: nucleation, growth, and coalescence of voids. The results indicate that growth rate of voids with equivalent diameters in the range of 2-5 mm is of about one order of magnitude higher than the prediction of continuum solid mechanics. Analysis of void coalescence points out the presence of two stable growth regimes related to coalescence between primary and secondary voids, respectively.

  16. Optical characterization of sputtered carbon films

    SciTech Connect

    Ager, J.W. III.

    1992-05-01

    Spattered carbon films are widely used as protective overcoats for thin film disk media. Raman spectroscopy is nondestructive and relatively rapid and is well suited for the characterization of carbon films. Specific features in the Raman spectra are empirically correlated with the rates of specific types of mechanical wear for both hydrogenated and unhydrogenated films. This observation is interpreted in terms of a random covalent network, in which the mechanical performance of the film is determined by the nature of the bonding that links sp{sup 2}-bonded domains.

  17. Nondestructive Structural Damage Detection in Flexible Space Structures Using Vibration Characterization

    NASA Technical Reports Server (NTRS)

    Ricles, James M.

    1991-01-01

    Spacecraft are susceptible to structural damage over their operating life from impact, environmental loads, and fatigue. Structural damage that is not detected and not corrected may potentially cause more damage and eventually catastrophic structural failure. NASA's current fleet of reusable spacecraft, namely the Space Shuttle, has been flown on several missions. In addition, configurations of future NASA space structures, e.g. Space Station Freedom, are larger and more complex than current structures, making them more susceptible to damage as well as being more difficult to inspect. Consequently, a reliable structural damage detection capability is essential to maintain the flight safety of these structures. Visual inspections alone can not locate impending material failure (fatigue cracks, yielding); it can only observe post-failure situations. An alternative approach is to develop an inspection and monitoring system based on vibration characterization that assesses the integrity of structural and mechanical components. A methodology for detecting structural damage is presented. This methodology is based on utilizing modal test data in conjunction with a correlated analytical model of the structure to: (1) identify the structural dynamic characteristics (resonant frequencies and mode shapes) from measurements of ambient motions and/or force excitation; (2) calculate modal residual force vectors to identify the location of structural damage; and (3) conduct a weighted sensitivity analysis in order to assess the extent of mass and stiffness variations, where structural damage is characterized by stiffness reductions. The approach is unique from other existing approaches in that varying system mass and stiffness, mass center locations, the perturbation of both the natural frequencies and mode shapes, and statistical confidence factors for structural parameters and experimental instrumentation are all accounted for directly.

  18. Optical properties and surface damage studies of crystalline silicon caused by swift iron ions

    NASA Astrophysics Data System (ADS)

    Dubey, S. K.

    2016-05-01

    p-Type silicon samples irradiated with 70 MeV 56Fe5+ ions for various fluences varying between 5 × 1012 and 4 × 1014 ions cm-2 have been studied using spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The microstructure of the irradiated samples was modeled from ellipsometric data, using a multilayer optical model and Bruggeman effective medium approximation. The values of pseudodielectric function, absorption coefficient and Penn gap energy were determined with respect to ion fluence. The effective medium analysis suggests that the superficial silicon layer can be explained as a mixture of crystalline and damaged silicon. The thickness of the damaged layer and percentage of voids present in the layer were found to increase with increase in the ion fluence. The effect of disorder on the interband optical spectra, especially on the critical point E1 at 3.4 eV was found to vary with ion fluence. A red shift in the critical point E1 with increasing ion fluence was observed. FTIR study showed of silicon samples irradiated with 70 MeV 56Fe5+ ions produced the oscillations in the spectral region 1000-400 cm-1. As irradiated sample showed more pronounced fringes, while contrast of the fringes and amplitude both were found to decrease with increase in depth.

  19. Optical coherence tomography imaging of retinal damage in real time under a stimulus electrode

    NASA Astrophysics Data System (ADS)

    Cohen, Ethan; Agrawal, Anant; Connors, Megan; Hansen, Barry; Charkhkar, Hamid; Pfefer, Joshua

    2011-10-01

    We have developed a novel method to study the effects of electrical stimulation of the local retina directly under an epiretinal stimulus electrode in real time. Using optical coherence tomography (OCT) and a superfused retinal eyecup preparation, we obtained high-resolution images of the rabbit retina directly under an optically transparent saline-filled fluoropolymer stimulation tube electrode. During OCT imaging, 50 Hz trains of biphasic current pulses 1 ms/phase (23-749 µC cm-2 ph-1) were applied to the retinal surface for 5 min. After imaging, the stimulated regions were stained with the dye propidium iodide (PI) to reveal cytotoxic damage. Pulse train stimulation at 44-133 µC cm-2 ph-1 had little effect on the retina; however, trains >=442 µC cm-2 ph-1 caused increases in the reflectance of the inner plexiform layer (IPL) and edema. The damage seen in retinal OCT images matched the pattern observed in histological sections, and in the PI staining. With pulse trains >=442 µC cm-2 ph-1, rapid increases in the reflectivity of the IPL could be observed under the stimulus electrode. Below the electrode, we observed a ring-like pattern of retinal detachment in the subretinal space. The OCT imaging method may be useful for analyzing overstimulation of neuronal tissue by electrodes in many brain regions. This paper was originally submitted for the special issue containing contributions from the Sixth Biennial Research Congress of The Eye and the Chip.

  20. Near-field characteristics of broad area diode lasers during catastrophic optical damage failure

    NASA Astrophysics Data System (ADS)

    Hempel, Martin; Tomm, Jens W.; Baeumler, Martina; Konstanzer, Helmer; Mukherjee, Jayanta; Elsaesser, Thomas

    2012-06-01

    One of the failure mechanisms preventing diode lasers in reaching ultra high optical output powers is the catastrophic optical damage (COD). It is a sudden degradation mechanism which impairs the device functionality completely. COD is caused by a positive feedback loop of absorbing laser light and increasing temperature at a small portion of the active material, leading to a thermal runaway on a nanosecond timescale. We analyze commercial gain-guided AlGaAs/GaAs quantum well broad area diode lasers in single pulse step tests. The near-field emission on the way to and at the COD is resolved on a picosecond time scale by a streak-camera combined with a microscope. In the final phase of the step tests the COD is occurring at ~50 times threshold current. The growth of the COD defect site is monitored and defect propagation velocities between 30 and 190 μm/μs are determined. The final shape of the damage is verified by opening the device and taking a micro-photoluminescence map of the active layer.

  1. Characterization of optical components for use in harsh environments

    NASA Astrophysics Data System (ADS)

    Bright, Michelle; Morelli, Gregg

    2006-08-01

    The characterization of mounted and/or bonded optical assemblies for survivability in harsh environments is crucial for the development of robust laser-optical firing systems. Customized mounts, bonded assemblies and packaging strategies were utilized for each of the laser resonator optics with the goal of developing and fielding a reliable initiation system for use in extreme conditions. Specific components were selected for initial testing based on past experience, material properties and optical construction. Shock, vibration and temperature testing was performed on three mounted optical components; polarizing cube beam splitters, Q-switch assemblies and xenon flashlamps. Previously, flashlamps of a solder-sealed construction type were successfully tested and characterized. This test regiment characterized the more fragile glass-to-metal seal constructed flashlamps. Components were shock-tested to a maximum impulse level of 5700 G's with a 1.1 millisecond long pulse. Vibration tests were performed to a maximum level of 15.5 grms for forty seconds in each of three axes. During each test, components were functionally tested and visually inspected at a specified point to verify survival. Temperature tests were performed over a range extending from a maximum of 75 degrees C to a minimum of -55 degrees C, allowing for a two hour soak at each temperature set point. Experimental results obtained from these tests will be discussed as will their impact on future component mounting strategies.

  2. Effects of laser plasma on damage in optical glass induced by pulsed lasers

    NASA Astrophysics Data System (ADS)

    Han, Jinghua; Li, Yaguo; He, Changtao; Zhang, Qiuhui; Niu, Ruihua; Yang, Liming; Feng, Guoying

    2012-12-01

    Laser-induced plasma can expedite the deposition of incident laser energy and the laser-induced damage in optical glass is considerably affected by the magnitude and distribution of the plasma shock wave. The spatial distribution of energy deposition and expansion pressure of the laser plasma shock wave is analyzed based on the moving breakdown model. Furthermore, damage morphologies are discussed in light of the spatial distribution of pressure and glass properties. It was found that with the increase of laser pulse energy, the shock wave expands rapidly in the direction opposite to the incident laser, resulting in that the damage morphologies transform from sphere to spindle gradually. The laser energy deposits mostly in a narrow plasma channel. The diffusion of the plasma with high temperature and pressure leads to the shock wave; the intensity of which decreases sharply with the axial distance from the centerline. As a consequence, the glass near the centerline fractures and melts, and the refractive index also changes near the end of cracks.

  3. Optical method for the surface topographic characterization of Fresnel lenses

    NASA Astrophysics Data System (ADS)

    Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Alonso Fernández, José; Quiroga, Juan Antonio

    2011-10-01

    Fresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices. As applications are more exigent this characterization is of increasing importance. We present a technique to characterize the surface topography of optical surfaces. It is especially well adapted to Fresnel lenses where abrupt surface slopes are usually difficult to handle in conventional techniques. The method is based on a new photometric strategy able to codify the height information in terms of optical absorption in a liquid. A detailed topographic map is simple to acquire by capturing images of the surface. Some experimental results are presented. A single pixel height resolution of ~0.1 μm is achieved for a height range of ~50 μm. A surface slope analysis is also made achieving a resolution of ~+/-0.15°.

  4. Optical coherence elastography for tissue characterization: a review

    PubMed Central

    Wang, Shang; Larin, Kirill V.

    2015-01-01

    Optical coherence elastography (OCE) represents the frontier of optical elasticity imaging techniques and focuses on the micro-scale assessment of tissue biomechanics in 3D that is hard to achieve with traditional elastographic methods. Benefit from the advancement of optical coherence tomography, and driven by the increasing requirements in nondestructive biomechanical characterization, this emerging technique recently has experienced a rapid development. In this paper, we start with the description of the mechanical contrast that has been employed by OCE and review the state-of-the-art techniques based on the reported applications and discuss the current technical challenges, emphasizing the unique role of OCE in tissue mechanical characterization. The position of OCE among other elastography techniques. PMID:25412100

  5. Characterization of impact damage in woven fiber composites using fiber Bragg grating sensing and NDE

    NASA Astrophysics Data System (ADS)

    Hiche, Cristobal; Liu, Kuang C.; Seaver, Mark; Wei, Jun; Chattopadhyay, Aditi

    2009-03-01

    Woven fiber composites are currently being investigated due to their advantages over other materials, making them suitable for low weight, high stiffness, and high interlaminar fracture toughness applications such as missiles, body armor, satellites, and many other aerospace applications. Damage characterization of woven fabrics is a complex task due to their tendency to exhibit different failure modes based on the weave configuration, orientation, ply stacking and other variables. A multiscale model is necessary to accurately predict progressive damage. The present research is an experimental study on damage characterization of three different woven fiber laminates under low energy impact using Fiber Bragg Grating (FBG) sensors and flash thermography. A correlation between the measured strain from FBG sensors and the damaged area obtained from flash thermography imaging has been developed. It was observed that the peak strain in the fabrics were strongly dependent on the weave geometry and decreased at different rates as damage area increased due to dissimilar failure modes. Experimental observations were validated with the development of a multiscale model. A FBG sensor placement model was developed which showed that FBG sensor location and orientation plays a key role in the sensing capabilities of strain on the samples.

  6. Ultrasonic Characterization of Fiber-Matrix Interphasial Properties and Damage in High-Temperature Composites

    NASA Astrophysics Data System (ADS)

    Chu, Ya-Cherng

    This study addresses ultrasonic characterization of fiber-matrix interphasial properties and damage in high -temperature composites. To accomplish this, experimental techniques for measurements of ultrasonic phase velocities and methodology for calculation of composite elastic moduli from velocity data are first developed and applied to unidirectional ceramic and intermetallic matrix composites. It is shown that computational error in the composite moduli is comparable to experimental error in the velocity data. For cross -ply composites, a novel method for determination of lamina elastic moduli from measurements on a (0/90) _ {s} composite is developed and validated experimentally. Second, a method to determine the elastic moduli of interphasial layers in high-temperature composites from the measured composite moduli is developed and applied to characterization of 3-μm thick carbon interphasial layers in ceramic and intermetallic matrix composites. Third, the techniques developed are used for assessment of oxidation and fatigue damage in ceramic and metal matrix composites. It is shown that ultrasonic phase velocities are very sensitive to damage and can effectively quantify damage severity. Appropriate models are applied to describe the effect of damage on the measured ultrasonic data, and they show reasonable agreement with experiments.

  7. Optical measurement system for characterizing plastic surfaces

    NASA Astrophysics Data System (ADS)

    Gahleitner, R.; Niel, Kurt S.; Frank, S.

    2008-02-01

    Injection molded plastic parts are often influenced with the surface defect tiger stripes, which dramatically reduce the visual quality. Tiger stripes are known as alternating bands of bright and dull regions normally to the molded flow direction. This defect highly depends on the injection time and on the formation of the plastic compound. In the last years, the intensity of the tiger stripes defect was controlled visually. For quantifying the tiger strip defect a new, efficient, repeatable, reliable and nondestructive optical measurement system is proposed. To evaluate the dependency of the injection time, a number of five DIN-A5 plastic specimens are molded. Each of the five plates consists of the same material but they have different injection times. For the measurement, one specimen is put into the specimen holder, which is placed on the drawer of a closed cabinet. In this inside black painted cabinet a LED light source and a CCD Camera are mounted. The beams of the LED light are diffuse reflected on the surface of the specimen. To catch only parallel beams by the lens of the camera a large distance between specimen and camera is realized by two justified mirrors in the cabinet. The bright and dull regions of the tiger stripe defect have different diffuse reflection parameters. Thus in a picture of defined brightness the visibility of this defect is very good. To enhance the repeatability the failure of the camera noise and of the light oscillation is reduced by mends of averaging multiple images. Next, the surface structure is filtered out of the image and a representing number of horizontal grey-value lines are extracted. The so called tiger line signal is the difference between the grey line and a calculated polynomial function (degree of 6) and shows the surface defect of each line oscillating on the zero x-axis. For each tiger line signal the mean squared error is evaluated. To calculate a quantitative value of the whole surface, all line errors are

  8. Use of optical reporter genes to assess sublethal cellular damage following skin ablation

    NASA Astrophysics Data System (ADS)

    Wilmink, Gerald J.; Opalenik, Susan R.; Davidson, Jeffrey M.; Jansen, E. Duco

    2008-02-01

    Numerous medical procedures utilize pulsed lasers to remove unwanted biological tissue. Mid-infrared wavelengths which preferentially target protein absorption bands ablate tissue more efficiently than wavelengths targeting water absorption. However, the mechanism responsible for this finding has not been established. In this report, we combine optical imaging and conventional techniques to assess lethal and sublethal collateral damage after ablative surgery with a Free Electron Laser (FEL). Heat shock protein expression was used to evaluate tissue damage in a transgenic mouse strain, with the hsp70 promoter driving luciferase and GFP expression (hsp70A1-L2G). To examine wavelength-dependence in the mid-IR, laser surgery was conducted on the hsp70A1-L2G mouse model using wavelengths targeting protein (amide II band, 6.45 μm), both water and protein (amide I band, 6.10 μm) and water (2.94 μm). Hsp70-driven luciferase activity was used as a quantitative biomarker for intracellular damage, and histological analyses were conducted to measure the depth of thermal damage. For all of the wavelengths tested, the bioluminescent data showed that the magnitude of hsp70 expression was dose-dependent. Tissues treated at 6.45 µm had approximately 2x higher hsp70 expression than tissues treated at 6.10 μm. Histology showed that immediate tissue injury at the 6.45 μm wavelength was ~2x deeper than at 6.10 μm. The 6.10 μm wavelength generated the least amount of epidermal hyperplasia. Overall, the data suggests that 6.10 μm is a superior wavelength for cutaneous laser ablation procedures.

  9. Characterizing matrix remodeling in collagen gels using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Levitz, David; Hinds, Monica T.; Hanson, Stephen R.; Jacques, Steven L.

    2010-02-01

    Optical coherence tomography (OCT) has shown promise at non-destructively characterizing engineered tissues such as collagen gels. However, as the collagen gels develop, the OCT images lose contrast of structures as the gels develop, making visual assessment difficult. Our group proposed quantitatively characterizing these gels by fitting the optical properties from the OCT signals. In this paper, we imaged collagen gels seeded with smooth muscle cells (SMCs) over a 5-day period and used the data to measure their optical properties. Our results showed that over time, the reflectivity of the samples increased 10-fold, corresponding to a decrease in anisotropy factor g, without much change in the scattering coefficient μs. Overall, the optical properties appeared to be dominated by scattering from the collagen matrix, not the cells. However, SMCs remodeled the collagen matrix, and this collagen remodeling by the cells is what causes the observed changes in optical properties. Moreover, the data showed that the optical properties were sensitive to the activity of matrix metalloproteinases (MMPs), enzymes that break down local collagen fibrils into smaller fragments. Blocking MMPs in the SMC gels greatly impeded both the remodeling process and change in optical properties at day 5. Treating day 1 acellular gels with MMP-8 for 3 hr managed to partially reproduce the remodeling observed in SMC gels at day 5. Altogether, we conclude that matrix remodeling in general, and MMPs specifically, greatly affect the local optical properties of the sample, and OCT is a unique tool that can assess MMP activity in collagen gels both non-destructively and label free.

  10. Reliable and Repeatable Characterization of Optical Streak Cameras

    SciTech Connect

    Michael Charest Jr., Peter Torres III, Christopher Silbernagel, and Daniel Kalantar

    2008-10-31

    Optical streak cameras are used as primary diagnostics for a wide range of physics and laser experiments at facilities such as the National Ignition Facility (NIF). To meet the strict accuracy requirements needed for these experiments, the systematic nonlinearities of the streak cameras (attributed to nonlinearities in the optical and electrical components that make up the streak camera system) must be characterized. In some cases the characterization information is used as a guide to help determine how experiment data should be taken. In other cases, the characterization data are applied to the raw data images to correct for the nonlinearities. In order to characterize an optical streak camera, a specific set of data is collected, where the response to defined inputs are recorded. A set of analysis software routines has been developed to extract information such as spatial resolution, dynamic range, and temporal resolution from this data set. The routines are highly automated, requiring very little user input and thus provide very reliable and repeatable results that are not subject to interpretation. An emphasis on quality control has been placed on these routines due to the high importance of the camera characterization information.

  11. Reliable and Repeatable Characterication of Optical Streak Cameras

    SciTech Connect

    Kalantar, D; Charest, M; Torres III, P; Charest, M

    2008-05-06

    Optical streak cameras are used as primary diagnostics for a wide range of physics and laser experiments at facilities such as the National Ignition Facility (NIF). To meet the strict accuracy requirements needed for these experiments, the systematic nonlinearities of the streak cameras (attributed to nonlinearities in the optical and electrical components that make up the streak camera system) must be characterized. In some cases the characterization information is used as a guide to help determine how experiment data should be taken. In other cases, the characterization data are applied to the raw data images to correct for the nonlinearities. In order to characterize an optical streak camera, a specific set of data is collected, where the response to defined inputs are recorded. A set of analysis software routines has been developed to extract information such as spatial resolution, dynamic range, and temporal resolution from this data set. The routines are highly automated, requiring very little user input and thus provide very reliable and repeatable results that are not subject to interpretation. An emphasis on quality control has been placed on these routines due to the high importance of the camera characterization information.

  12. Methods for Mitigating Growth of Laser-Initiated Surface Damage on Fused Silcia Optics at 351nm

    SciTech Connect

    Hrubesh, L W; Norton, M A; Molander, W A; Donohue, E E; Maricle, S M; Penetrante, B M; Brusasco, R M; Grundler, W; Butler, J A; Carr, J W; Hill, R M; Summers, L J; Feit, M D; Rubenchik, A; Key, M H; Wegner, P J; Burnham, A K; Hackel, L A; Kozlowski, M R

    2001-12-12

    We report a summary of the surface damage, growth mitigation effort at 351nm for polished fused silica optics. The objective was to experimentally validate selected methods that could be applied to pre-initiated or retrieved-from-service optics, to stop further damage growth. A specific goal was to obtain sufficient data and information on successful methods for fused silica optics to select a single approach for processing large aperture, fused-silica optics used in high-peak-power laser applications. This paper includes the test results and the evaluation thereof, for several mitigation methods for fused silica surfaces. The mitigation methods tested in this study are wet chemical etching, cold plasma etching, CW-CO{sub 2} laser processing, and micro-flame torch processing. We found that CW-CO{sub 2} laser processing produces the most significant and consistent results to halt laser-induced surface damage growth on fused silica. We recorded successful mitigation of the growth of laser-induced surface damage sites as large as 0.5mm diameter, for 1000 shots at 351nm and fluences in the range of 8 to 13J/cm{sup 2}, {approx}11ns pulse length. We obtained sufficient data for elimination of damage growth using CO{sub 2} laser processing on sub-aperture representative optics, to proceed with application to large aperture ({approx}40 x 40cm{sup 2}) fused silica.

  13. Optical characterization of carbon nanotube forests

    NASA Astrophysics Data System (ADS)

    Wood, Brian D.

    Carbon nanotube forests are vertically grown tubular formations of graphene. Samples were grown with an injection chemical vapor deposition method on substrates of silicon with various deposited layers and bare fused silica. The morphology of the forest is characterized by the height, density, and presence of defects. Total diffuse reflectance and transmittance measurements were taken in the 2-16 ?m spectral range and correlated to the forest's specific morphology. From these correlations, the conditions necessary to maximize the absorption of the forest were found and exploited to cater sample growth for specific substrates to make ideal absorbers. From the transmittance data, the absorption coefficient is found via Beer-Lambert's Law and also correlated to sample morphology, giving us an indication of the height of the forest needed for ideal absorption. Two models were used to attempt to reproduce the experimental absorption coefficient: an effective medium theory using a Maxwell Garnett approximation and by treating the carbon nanotube forest as an effective cylindrical waveguide with walls of graphite. Each model leads to a set of fitting parameters providing a better physical understanding of the forests. It was found that the effective medium theory gave results loosely corroborated with electron microscopy, but had trouble fitting the experimental data, and the index of refraction it provides does not behave like a unified medium. The waveguide model fits the data well, but it requires more experimental evidence to be more conclusive. The theoretical models need more work, but fabrication of ideal absorbers has been achieved on various substrates providing framework for their usage in radiometry and spectroscopy.

  14. Pathophysiology of human glaucomatous optic nerve damage: insights from rodent models of glaucoma.

    PubMed

    Morrison, John C; Cepurna Ying Guo, William O; Johnson, Elaine C

    2011-08-01

    Understanding mechanisms of glaucomatous optic nerve damage is essential for developing effective therapies to augment conventional pressure-lowering treatments. This requires that we understand not only the physical forces in play, but the cellular responses that translate these forces into axonal injury. The former are best understood by using primate models, in which a well-developed lamina cribrosa, peripapillary sclera and blood supply are most like that of the human optic nerve head. However, determining cellular responses to elevated intraocular pressure (IOP) and relating their contribution to axonal injury require cell biology techniques, using animals in numbers sufficient to perform reliable statistical analyses and draw meaningful conclusions. Over the years, models of chronically elevated IOP in laboratory rats and mice have proven increasingly useful for these purposes. While lacking a distinct collagenous lamina cribrosa, the rodent optic nerve head (ONH) possesses a cellular arrangement of astrocytes, or glial lamina, that ultrastructurally closely resembles that of the primate. Using these tools, major insights have been gained into ONH and the retinal cellular responses to elevated IOP that, in time, can be applied to the primate model and, ultimately, human glaucoma. PMID:20708000

  15. Threshold effects for resistance to optical damage and nonvolatile holographic storage properties in In:Mn:Fe:LiNbO3 crystals

    SciTech Connect

    Zhen Xihe; Li Qiang; Xu Yuheng

    2005-07-20

    The threshold concentration for In2O3 was found in In:Mn:Fe:LiNbO3 crystals by measurement of the infrared spectra of the crystals. The resistance of the In:Mn:Fe:LiNbO3 crystals to optical damage is characterized by changes in photoinduced birefringence as well as by distortion of the transmitted beam pattern. The resistance increases remarkably when the concentration of In2O3 exceeds its threshold. The resistance to optical damage of a In(3.0 mol. %):Mn:Fe:LiNbO3 crystal is 2 orders of magnitude higher that of a Mn:Fe:LiNbO3 crystal. The dependence of defects on the resistance to optical damage of the In:Mn:Fe:LiNbO3 crystals is discussed in detail. Nonvolatile holographic storage was achieved for all crystals, and the sensitivity of the In(3.0 mol. %):Mn:Fe:LiNbO3 crystal is much higher than that of the others.

  16. High-Sensitivity Optical Pulse Characterization Using Sagnac Electro-Optic Spectral Shearing Interferometry

    SciTech Connect

    Dorrer, C.; Bromage, J.

    2010-05-04

    An electro-optic spectral shearing interferometer for high-sensitivity optical pulse characterization is described. Two replicas of the test pulse counterpropagate in a Sagnac interferometer with orthogonal polarization states, resulting in two relatively sheared copolarized replicas after temporal phase modulation. The polarization interferometer is intrinsically stable, and its birefringence sets the delay between interfering replicas to reduce the spectrometer resolution requirement. Experimental implementations demonstrate real-time pulse characterization at average powers as low as 1 nWwith spectral shears as high as 280 GHz.

  17. Optical characterization of subwavelength-scale solid immersion lenses

    NASA Astrophysics Data System (ADS)

    Kim, Myun-Sik; Scharf, Toralf; Haq, Mohammad Tahdiul; Nakagawa, Wataru; Herzig, Hans Peter

    2012-03-01

    We present the fabrication and optical characterization of nano-scale solid immersion lenses (nano-SILs) with sizes down to a subwavelength range. Submicron-scale cylinders fabricated by electron-beam lithography (EBL) are thermally reflowed to form a spherical shape. Subsequent soft lithography leads to nano-SILs on transparent substrates, i.e. glass, for optical characterization with visible light. The optical characterization is performed using a high-resolution interference microscope (HRIM) with illumination at 642 nm wavelength. The measurements of the 3D amplitude and phase fields provide information on the spot size and the peak intensity. In particular, the phase measurement is a more convincing proof of the Airy disc size reduction rather than the full-width at half maximum (FWHM) spot size. The focal spots produced by the nano-SILs show both spot-size reduction and enhanced optical intensity, which are consistent with the immersion effect. In this way, we experimentally confirm the immersion effect of a subwavelength-size SIL (d = 530 nm and h = 45 nm) with a spot reduction ratio of 1.35, which is less than the expected value of 1.5, most likely due to the slightly non-ideal shape of the nano-SIL.

  18. Test results from LAGEOS-2 optical characterization using pulsed lasers

    NASA Technical Reports Server (NTRS)

    Varghese, Thomas K.; Selden, Michael; Oldham, Thomas; Clarke, Christopher; Zagwodzki, Thomas

    1993-01-01

    The Laser Geodynamic Satellite-2 (LAGEOS-2) has undergone extensive optical testing at NASA Goddard Space Flight Center during 1989. The techniques included measuring the far field diffraction pattern using cw and pulsed lasers. In the pulsed measurement technique, response of the satellite was studied by measuring the far-field diffraction pattern (FFDP) as a function of pulsewidth, wavelength, polarization, position in the FFDP, detector/processing techniques, and satellite orientation. The purpose of the pulsed laser testing was two-fold: (1) to characterize the satellite optical response with the detector and signal processing electronics currently used in most SLR stations using the portable laser ranging standard, and (2) to characterize the satellite response for various conditions using the highest bandwidth optical detector (streak camera) available for the next generation of satellite laser ranging (SLR) technology. The portable ranging standard employed multiple measurement devices and an optical calibration scheme to eliminate range-dependent and amplitude-dependent systematics. These precautions were taken to eliminate/minimize instrumental errors and provide maximum accuracy. For LAGEOS orbit (6000 Km), ground stations are located 34 to 38 Mu radians off the axis of the return signal from the satellite; therefore, an optical mask was used to restrict the field of view (FOV) of detection to this annular region of the FFDP. The two measurement techniques were implemented using an aperture sharing scheme and complemented each other by providing mutual verification.

  19. Response surface characterization of impact damage and residual strength degradation in composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Samarah, Issam Khder

    2003-06-01

    of strength were also addressed. Moreover, using a relatively small sample of experimental observations, statistical models were developed that are able to characterize the planar impact damage development and residual strength degradation for a large population of independent sandwich composite specimens. Employing the methodology outlined here, it may be possible to tailor sandwich composite designs in order to obtain enhanced damage tolerance characteristics over a range of expected impacts. Such efforts may facilitate sandwich panel design by establishing relationships between material configuration and impact parameters that lead to improved damage tolerance/resistance.

  20. Materials and processes laboratory composite materials characterization task, part 1. Damage tolerance

    NASA Technical Reports Server (NTRS)

    Nettles, A. T.; Tucker, D. S.; Patterson, W. J.; Franklin, S. W.; Gordon, G. H.; Hart, L.; Hodge, A. J.; Lance, D. G.; Russel, S. S.

    1991-01-01

    A test run was performed on IM6/3501-6 carbon-epoxy in which the material was processed, machined into specimens, and tested for damage tolerance capabilities. Nondestructive test data played a major role in this element of composite characterization. A time chart was produced showing the time the composite material spent within each Branch or Division in order to identify those areas which produce a long turnaround time. Instrumented drop weight testing was performed on the specimens with nondestructive evaluation being performed before and after the impacts. Destructive testing in the form of cross-sectional photomicrography and compression-after-impact testing were used. Results show that the processing and machining steps needed to be performed more rapidly if data on composite material is to be collected within a reasonable timeframe. The results of the damage tolerance testing showed that IM6/3501-6 is a brittle material that is very susceptible to impact damage.

  1. Thermal characterization of optical fibers using wavelength-sweeping interferometry.

    PubMed

    Perret, Luc; Pfeiffer, Pierre; Serio, Bruno; Twardowski, Patrice

    2010-06-20

    In this paper, we report a new method of thermal characterization of optical fibers using wavelength-sweeping interferometry and discuss its advantages compared to other techniques. The setup consists of two temperature-stabilized interferometers, a reference Michelson and a Mach-Zehnder, containing the fiber under test. The wavelength sweep is produced by an infrared tunable laser diode. We obtained the global phase shift coefficients of a large effective area fiber and gold-coated fiber optics with a 10(-7) accuracy. PMID:20563215

  2. Complete characterization of partially coherent and partially polarized optical fields.

    PubMed

    Basso, Gabriel; Oliveira, Luimar; Vidal, Itamar

    2014-03-01

    We suggest a method to access the second-order, or two-point, Stokes parameters of a partially coherent and partially polarized Gaussian model optical field from an intensity interferometry experiment. Through a remarkably simple experimental arrangement, it is possible to measure the two-point and one-point Stokes parameters simultaneously, allowing the reconstruction of the coherence matrix and the polarization matrix, thus completely characterizing the optical field both statistically and locally on the observation plane. Developments, automation, and applications are pointed out. PMID:24690711

  3. Research on laser-induced damage resistance of fused silica optics by the fluid jet polishing method.

    PubMed

    Lv, Liang; Ma, Ping; Huang, Jinyong; He, Xiang; Cai, Chao; Zhu, Heng

    2016-03-20

    Laser-induced damage threshold (LIDT) is one important evaluation index for optical glasses applied in large laser instruments which are exposed to high light irradiation flux. As a new kind of precise polishing technology, fluid jet polishing (FJP) has been widely used in generating planar, spherical, and aspherical optics with high-accuracy surfaces. Laser damage resistances of fused silica optics by the FJP process are studied in this paper. Fused silica samples with various FJP parameters are prepared, and laser damage experiments are performed with 351 nm wavelength and a 5.5 ns pulse width laser. Experimental results demonstrate that the LIDT of the samples treated with FJP processes did not increase, compared to their original state. The surface quality of the samples is one factor for the decrease of LIDT. For ceria solution polished samples, the cerium element remaining is another factor of the lower LIDT. PMID:27140559

  4. Performance Characterization of Digital Optical Data Transfer Systems for Use in the Space Radiation Environment

    NASA Technical Reports Server (NTRS)

    Reed, Robert A.; Ladbury, Ray L.; Day, John H. (Technical Monitor)

    2000-01-01

    Radiation effects in photonic and microelectronic components can impact the performance of high-speed digital optical data link in a variety of ways. This segment of the short course focuses on radiation effects in digital optical data links operating in the MHz to GHz regime. (Some of the information is applicable to frequencies above and below this regime) The three basic component level effects that should be considered are Total Ionizing Dose (TID), Displacement Damage Dose (DDD) and Single Event Effects (SEE). In some cases the system performance degradation can be quantified from component level tests, while in others a more holistic characterization approach must be taken. In Section 2.0 of this segment of the Short Course we will give a brief overview of the space radiation environment follow by a summary of the basic space radiation effects important for microelectronics and photonics listed above. The last part of this section will give an example of a typical mission radiation environment requirements. Section 3.0 gives an overview of intra-satellite digital optical data link systems. It contains a discussion of the digital optical data link and it's components. Also, we discuss some of the important system performance metrics that are impacted by radiation effects degradation of optical and optoelectronic component performance. Section 4.0 discusses radiation effects in optical and optoelectronic components. While each component effect will be discussed, the focus of this section is on degradation of passive optical components and SEE in photodiodes (other mechanisms are covered in segment II of this short course entitled "Photonic Devices with Complex and Multiple Failure Modes"). Section 5.0 will focus on optical data link system response to the space radiation environment. System level SEE ground testing will be discussed. Then we give a discussion of system level assessment of data link performance when operating in the space radiation environment.

  5. Characterization of irradiation damage distribution near TiO{sub 2}/SrTiO{sub 3} interfaces using coherent acoustic phonon interferometry

    SciTech Connect

    Yarotski, Dmitry; Yan Li; Jia Quanxi; Taylor, Antoinette J.; Fu Engang; Wang Yongqiang; Uberuaga, Blas P.

    2012-06-18

    We apply ultrafast coherent acoustic phonon interferometry to characterize the distribution of the radiation damage near the TiO{sub 2}/SrTiO{sub 3} interfaces. We show that the optical and mechanical properties of anatase TiO{sub 2} remain unaffected by the radiation dosages in the 0.1 Division-Sign 5 dpa (displacements per atom) range, while the degraded optical response indicates a significant defect accumulation in the interfacial region of SrTiO{sub 3} at 0.1 dpa and subsequent amorphization at 3 dpa. Comparison between the theoretical simulations and the experimental results reveals an almost threefold reduction of the sound velocity in the irradiated SrTiO{sub 3} layer with peak damage levels of 3 and 5 dpa.

  6. Ultrafast optical technique for the characterization of altered materials

    DOEpatents

    Maris, H.J.

    1998-01-06

    Disclosed herein is a method and a system for non-destructively examining a semiconductor sample having at least one localized region underlying a surface through into which a selected chemical species has been implanted or diffused. A first step induces at least one transient time-varying change in optical constants of the sample at a location at or near to a surface of the sample. A second step measures a response of the sample to an optical probe beam, either pulsed or continuous wave, at least during a time that the optical constants are varying. A third step associates the measured response with at least one of chemical species concentration, chemical species type, implant energy, a presence or absence of an introduced chemical species region at the location, and a presence or absence of implant-related damage. The method and apparatus in accordance with this invention can be employed in conjunction with a measurement of one or more of the following effects arising from a time-dependent change in the optical constants of the sample due to the application of at least one pump pulse: (a) a change in reflected intensity; (b) a change in transmitted intensity; (c) a change in a polarization state of the reflected and/or transmitted light; (d) a change in the optical phase of the reflected and/or transmitted light; (e) a change in direction of the reflected and/or transmitted light; and (f) a change in optical path length between the sample`s surface and a detector. 22 figs.

  7. Ultrafast optical technique for the characterization of altered materials

    DOEpatents

    Maris, Humphrey J.

    1998-01-01

    Disclosed herein is a method and a system for non-destructively examining a semiconductor sample (30) having at least one localized region underlying a surface (30a) through into which a selected chemical species has been implanted or diffused. A first step induces at least one transient time-varying change in optical constants of the sample at a location at or near to a surface of the sample. A second step measures a response of the sample to an optical probe beam, either pulsed or continuous wave, at least during a time that the optical constants are varying. A third step associates the measured response with at least one of chemical species concentration, chemical species type, implant energy, a presence or absence of an introduced chemical species region at the location, and a presence or absence of implant-related damage. The method and apparatus in accordance with this invention can be employed in conjunction with a measurement of one or more of the following effects arising from a time-dependent change in the optical constants of the sample due to the application of at least one pump pulse: (a) a change in reflected intensity; (b) a change in transmitted intensity; (c) a change in a polarization state of the reflected and/or transmitted light; (d) a change in the optical phase of the reflected and/or transmitted light; (e) a change in direction of the reflected and/or transmitted light; and (f) a change in optical path length between the sample's surface and a detector.

  8. Photorefractive damage mechanisms in electro-optic materials. Final report, July 1985-March 1989

    SciTech Connect

    Halliburton, L.E.

    1990-01-01

    Point defects in lithium niobate and related electro-optic materials have been characterized using electron paramagnetic resonance (EPR), optical absorption, thermally stimulated been used to investigate a radiation-induced trapped-hole center. This new S = 1/2 defect is stable at 77 K but thermally decays near 150 K. Its EPR spectrum exhibits a complex hyperfine equally with three 93 Nb nuclei. We suggest that the hole is equally shared by a set of three equivalent oxygen ions adjacent to a cation vacancy. The photo-induced redistribution of charge has been characterized in Bi12GeO20 and Bi12SiO20 crystals. Optical excitation at 77 K converts Fe (3+) ions to Fe(2+) ions. The source of electrons (i.e., the hole traps) may be other impurities or intrinsic defects such as vacancies or anti-site cations. The intrinsic defects such as vacancies or anti-site cations. The Fe(3+) recovery during warming correlates with thermoluminescence peaks at 145, 165, and 245 K. Our results suggest that Fe(3+) ions may play an important role in the photorefractive effect in these materials. In LiTaO3, the EPR spectrum of Ta(4+) ions have been investigated. The diffusion coefficients of deuterium in single crystals of LiTaO3 have been measured by monitoring the growth of OD (-) infrared absorption bands.

  9. Characterization facility for magneto-optic media and systems

    NASA Technical Reports Server (NTRS)

    Mansuripur, M.; Fu, H.; Gadetsky, S.; Sugaya, S.; Wu, T. H.; Zambuto, J.; Gerber, R.; Goodman, T.; Erwin, J. K.

    1993-01-01

    Objectives of this research are: (1) to measure the hysteresis loop, Kerr rotation angle, anisotropy energy profile, Hall voltage, and magnetoresistance of thin-film magneto-optic media using our loop-tracer; (2) measure the wavelength-dependence of the Kerr rotation angle, Theta(sub k), and ellipticity, epsilon(sub k), for thin-film media using our magneto-optic Kerr spectrometer (MOKS); (3) measure the dielectric tensor of thin-film and multilayer samples using our variable-angle magneto-optic ellipsometer (VAMOE); (4) measure the hysteresis loop, coercivity, remanent magnetization, saturation magnetization, and anisotropy energy constant for thin film magnetic media using vibrating sample magnetometry; (5) observe small magnetic domains and investigate their interaction with defects using magnetic force microscopy; (6) perform static read/write/erase experiments on thin-film magneto-optic media using our static test station; (7) integrate the existing models of magnetization, magneto-optic effects, coercivity, and anisotropy in an interactive and user-friendly environment, and analyze the characterization data obtained in the various experiments, using this modeling package; (8) measure focusing- and tracking-error signals on a static testbed, determine the 'feedthrough' for various focusing schemes, investigate the effects of polarization and birefringence, and compare the results with diffraction-based calculations; and (9) measure the birefringence of optical disk substrates using two variable angle ellipsometers.

  10. Preparation, Characterization and Application of Optical Switch Probes

    PubMed Central

    Petchprayoon, Chutima; Marriott, Gerard

    2011-01-01

    Optical switches represent a new class of molecular probe with applications in high contrast imaging and optical manipulation of protein interactions. Small molecule, organic optical switches based on nitrospirobenzopyran (NitroBIPS) and their reactive derivatives and conjugates undergo efficient, rapid and reversible, orthogonal optically-driven transitions between a colorless spiro (SP) state and a colored merocyanine (MC) state. The excited MC-state also emits fluorescence, which serves as readout of the state of the switch. Defined optical perturbations of SP and MC generate a defined waveform of MC-fluorescence that can be isolated against unmodulated background signals by using a digital optical lock-in detection approach or to control specific dipolar interactions on proteins. The protocols describe general procedures for the synthesis and spectroscopic characterization of NitroBIPS and specifically labeled conjugates along with methods for the manipulation of dipolar interactions on proteins and imaging of the MC-state of NitroBIPS within living cells. PMID:22140655

  11. Characterization of fiber optic Cerenkov radiation sensor for detecting neutrons

    NASA Astrophysics Data System (ADS)

    Jang, K. W.; Yagi, T.; Pyeon, C. H.; Shin, S. H.; Yoo, W. J.; Misawa, T.; Lee, B.

    2013-09-01

    Cerenkov radiation can be observed easily as a shimmer of blue light from the water in boiling- and pressurized-water reactors, or spent fuel storage pools. In this research, we fabricated the fiber-optic Cerenkov radiation sensor using a Gdfoil, rutile crystal and optical fiber for detecting neutrons. Also, the reference sensor for measuring background gammarays was fabricated with the rutile crystal and optical fiber. The neutron fluxes could be obtained by measuring the signal difference between two sensors. To characterize the fiber-optic Cerenkov radiation sensor, we measured neutron fluxes using a Cf-252 neutron source according to depths of polyethylene. As the results, the counts of fiber-optic Cerenkov radiation sensor were higher than those of reference sensor due to additional interactions between Gd-foil and neutrons. Also, the counts of Cerenkov radiation decreased with increasing polyethylene thickness. It is anticipated that the novel and simple fiber-optic Cerenkov radiation sensor using the Cerenkov effect can be widely used to detect the neutrons in hazardous nuclear facilities.

  12. Investigating photoexcitation-induced mitochondrial damage by chemotherapeutic corroles using multimode optical imaging

    NASA Astrophysics Data System (ADS)

    Hwang, Jae Youn; Lubow, David J.; Sims, Jessica D.; Gray, Harry B.; Mahammed, Atif; Gross, Zeev; Medina-Kauwe, Lali K.; Farkas, Daniel L.

    2012-01-01

    We recently reported that a targeted, brightly fluorescent gallium corrole (HerGa) is highly effective for breast tumor detection and treatment. Unlike structurally similar porphryins, HerGa exhibits tumor-targeted toxicity without the need for photoexcitation. We have now examined whether photoexcitation further modulates HerGa toxicity, using multimode optical imaging of live cells, including two-photon excited fluorescence, differential interference contrast (DIC), spectral, and lifetime imaging. Using two-photon excited fluorescence imaging, we observed that light at specific wavelengths augments the HerGa-mediated mitochondrial membrane potential disruption of breast cancer cells in situ. In addition, DIC, spectral, and fluorescence lifetime imaging enabled us to both validate cell damage by HerGa photoexcitation and investigate HerGa internalization, thus allowing optimization of light dose and timing. Our demonstration of HerGa phototoxicity opens the way for development of new methods of cancer intervention using tumor-targeted corroles.

  13. Measuring single-shot, picosecond optical damage threshold in Ge, Si, and sapphire with a 5.1-μm laser

    SciTech Connect

    Agustsson, R.; Pogorelsky, I.; Arab, E.; Murokh, A.; O"Shea, B.; Ovodenko, A.; Rosenzweig, J.; Solovyov, V.; Tilton, R.

    2015-11-18

    Optical photonic structures driven by picosecond, GW-class lasers are emerging as promising novel sources of electron beams and high quality X-rays. Due to quadratic dependence on wavelength of the laser ponderomotive potential, the performance of such sources scales very favorably towards longer drive laser wavelengths. However, to take full advantage of photonic structures at mid-IR spectral region, it is important to determine optical breakdown limits of common optical materials. To this end, an experimental study was carried out at a wavelength of 5 µm, using a frequency-doubled CO2 laser source, with 5 ps pulse length. Single-shot optical breakdowns were detected and characterized at different laser intensities, and damage threshold values of 0.2, 0.3, and 7.0 J/cm2, were established for Ge, Si, and sapphire, respectively. As a result, the measured damage threshold values were stable and repeatable within individual data sets, and across varying experimental conditions.

  14. Measuring single-shot, picosecond optical damage threshold in Ge, Si, and sapphire with a 5.1-μm laser

    DOE PAGESBeta

    Agustsson, R.; Pogorelsky, I.; Arab, E.; Murokh, A.; O"Shea, B.; Ovodenko, A.; Rosenzweig, J.; Solovyov, V.; Tilton, R.

    2015-11-18

    Optical photonic structures driven by picosecond, GW-class lasers are emerging as promising novel sources of electron beams and high quality X-rays. Due to quadratic dependence on wavelength of the laser ponderomotive potential, the performance of such sources scales very favorably towards longer drive laser wavelengths. However, to take full advantage of photonic structures at mid-IR spectral region, it is important to determine optical breakdown limits of common optical materials. To this end, an experimental study was carried out at a wavelength of 5 µm, using a frequency-doubled CO2 laser source, with 5 ps pulse length. Single-shot optical breakdowns were detectedmore » and characterized at different laser intensities, and damage threshold values of 0.2, 0.3, and 7.0 J/cm2, were established for Ge, Si, and sapphire, respectively. As a result, the measured damage threshold values were stable and repeatable within individual data sets, and across varying experimental conditions.« less

  15. Barely visible impact damage detection for composite sandwich structures by optical-fiber-based distributed strain measurement

    NASA Astrophysics Data System (ADS)

    Minakuchi, S.; Okabe, Y.; Mizutani, T.; Takeda, N.

    2009-08-01

    The authors developed an impact damage-detection system for large-scale composite sandwich structures using an optical fiber network running throughout the structure. A Brillouin-based sensing system with high spatial resolution (pre-pump pulse Brillouin optical time-domain analysis (PPP-BOTDA)) was utilized for distributed strain measurement. The PPP-BOTDA sensing system can measure axial strain along the optical fiber by employing stimulated Brillouin scattering. The system realizes a spatial resolution of 10 cm, a sampling interval of 5 cm, and a sensing range of more than 1 km. Our previous study revealed that a non-uniform axial strain within centimeter spatial resolution broadens the width of the Brillouin gain spectrum, which is the output of the PPP-BOTDA. The specific response of the PPP-BOTDA was employed to detect non-uniform strain distribution along a residual facesheet dent in a damaged area. First, the response of the optical fiber sensor network, formed in the adhesive layer, was simulated to clarify the effectiveness and limitations of the proposed damage-detection technique. The system was then validated by an experiment. As the damage became larger, the width of the Brillouin gain spectra became broader. Consequently, the location and size of barely visible damage could be estimated. The system developed is quite useful for a first inspection of large-scale sandwich structures in aerospace and marine applications.

  16. Image Processing and control of a programmable spatial light modulator for optic damage protection

    SciTech Connect

    Awwal, A; Leach, R; Brunton, G; Tse, E; Matone, J; Heebner, J

    2010-12-06

    The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 beams used to drive inertial confinement fusion reactions. A recently installed system of programmable, liquid-crystal-based spatial light modulators adds the capability of arbitrarily shaping the spatial beam profiles in order to enhance operational flexibility. Its primary intended use is for introducing 'blocker' obscurations shadowing isolated flaws on downstream optical elements that would otherwise be damaged by high fluence laser illumination. Because an improperly shaped blocker pattern can lead to equipment damage, both the position and shape of the obscurations must be carefully verified prior to high-fluence operations. An automatic alignment algorithm is used to perform detection and estimation of the imposed blocker centroid positions compared to their intended locations. Furthermore, in order to minimize the spatially-varying nonlinear response of the device, a calibration of the local magnification is performed at multiple sub-image locations. In this paper, we describe the control and associated image processing of this device that helps to enhance the safety and longevity of the overall system.

  17. Investigation of proton damage in III-V semiconductors by optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Yaccuzzi, E.; Khachadorian, S.; Suárez, S.; Reinoso, M.; Goñi, A. R.; Strittmatter, A.; Hoffmann, A.; Giudici, P.

    2016-06-01

    We studied the damage produced by 2 MeV proton radiation on epitaxially grown InGaP/GaAs structure by means of spatially resolved Raman and photoluminescence (PL) spectroscopy. The irradiation was performed parallel to the sample surface in order to determine the proton penetration range in both compounds. An increase in the intensity of longitudinal optical phonons and a decrease in the luminescence were observed. We associate these changes with the creation of defects in the damaged region, also responsible for the observed change of the carrier concentration in the GaAs layer, determined by the shift of the phonon-plasmon coupled mode frequency. From the spatially resolved profile of the PL and phonon intensities, we obtained the proton range in both materials and we compared them with stopping and range of ions in matter simulations. The comparison between the experimentally obtained proton range and simulations shows a very good agreement for GaAs but a discrepancy of 20% for InGaP. This discrepancy can be explained in terms of limitations of the model to simulate the electronic orbitals and bonding structure of the simulated compound. In order to overcome this limitation, we propose an increase in 40% in the electronic stopping power for InGaP.

  18. Catastrophic optical mirror damage in diode lasers monitored during single pulse operation

    NASA Astrophysics Data System (ADS)

    Tomm, Jens W.; Ziegler, Mathias; Elsaesser, Thomas; Larsen, Henning E.; Petersen, Paul M.; Andersen, Peter E.; Clausen, Sønnik; Zeimer, Ute; Fendler, David

    2010-02-01

    The catastrophic optical mirror damage (COMD) effect is analyzed for 808 nm emitting diode lasers in single-pulse operation. During each single pulse, both nearfield of the laser emission and thermal image of the laser facet are monitored with cameras being sensitive in the respective spectral regions. A temporal resolution in the μs-range is achieved. The COMD is unambiguously related to the occurrence of a 'thermal flash' detected by thermal imaging. A one-by-one correlation between emission nearfield, 'thermal flash', thermal runaway, and structural damage is observed. As a consequence of the single-pulse-excitation technique, the propagation of 'dark bands' as observed in photo- or cathodoluminescence maps in the plane of the active region from the front facet is halted after the first pulse. Because of the rapidness of the thermal runaway, we propose the single-pulse technique for testing the facet stability and the intentional preparation of early stages of COMD; even for diode lasers that regularly fail by other mechanisms.

  19. Laser treatment of female stress urinary incontinence: optical, thermal, and tissue damage simulations

    NASA Astrophysics Data System (ADS)

    Hardy, Luke A.; Chang, Chun-Hung; Myers, Erinn M.; Kennelly, Michael J.; Fried, Nathaniel M.

    2016-02-01

    Treatment of female stress urinary incontinence (SUI) by laser thermal remodeling of subsurface tissues is studied. Light transport, heat transfer, and thermal damage simulations were performed for transvaginal and transurethral methods. Monte Carlo (MC) provided absorbed photon distributions in tissue layers (vaginal wall, endopelvic fascia, urethral wall). Optical properties (n,μa,μs,g) were assigned to each tissue at λ=1064 nm. A 5-mm-diameter laser beam and power of 5 W for 15 s was used, based on previous experiments. MC output was converted into absorbed energy, serving as input for ANSYS finite element heat transfer simulations of tissue temperatures over time. Convective heat transfer was simulated with contact cooling probe set at 0 °C. Thermal properties (κ,c,ρ) were assigned to each tissue layer. MATLAB code was used for Arrhenius integral thermal damage calculations. A temperature matrix was constructed from ANSYS output, and finite sum was incorporated to approximate Arrhenius integral calculations. Tissue damage properties (Ea,A) were used to compute Arrhenius sums. For the transvaginal approach, 37% of energy was absorbed in endopelvic fascia layer with 0.8% deposited beyond it. Peak temperature was 71°C, treatment zone was 0.8-mm-diameter, and almost all of 2.7-mm-thick vaginal wall was preserved. For transurethral approach, 18% energy was absorbed in endopelvic fascia with 0.3% deposited beyond it. Peak temperature was 80°C, treatment zone was 2.0-mm-diameter, and only 0.6 mm of 2.4-mm-thick urethral wall was preserved. A transvaginal approach is more feasible than transurethral approach for laser treatment of SUI.

  20. Optical characterization of porous silicon microcavities for glucose oxidase biosensing

    NASA Astrophysics Data System (ADS)

    Palestino, G.; Agarwal, V.; Garcia, D. B.; Legros, R.; Pérez, E.; Gergely, C.

    2008-04-01

    PSi microcavity (PSiMc) is characterized by a narrow resonance peak in the optical spectrum that is very sensitive to small changes in the refractive index. We report that the resonant optical cavities of PSi structures can be used to enhance the detection of labeled fluorescent biomolecules. Various PSi configurations were tested in order to compare the optical response of the PSi devices to the capture of organic molecules. Morphological and topographical analyses were performed on PSiMc using Atomic Force (AFM) and Scanning Electron (SEM) microscopies. The heterogeneity in pores lengths resulting from etching process assures a better penetration of larger molecules into the pores and sensor sensitivity depends on the pore size. Molecular detection is monitored by the successive red shifts in the reflectance spectra after the stabilization of PSiMc with 3-aminopropyltriethoxysilane (APTES). The glucose oxidase was cross linked into the PSiMc structures following a silane-glutaraldehyde (GTA) chemistry.

  1. Dynamic spectral-domain optical coherence elastography for tissue characterization.

    PubMed

    Liang, Xing; Adie, Steven G; John, Renu; Boppart, Stephen A

    2010-06-21

    A dynamic spectral-domain optical coherence elastography (OCE) imaging technique is reported. In this technique, audio-frequency compressive vibrations are generated by a piezoelectric stack as external excitation, and strain rates in the sample are calculated and mapped quantitatively using phase-sensitive spectral-domain optical coherence tomography. At different driving frequencies, this technique provides contrast between sample regions with different mechanical properties, and thus is used to mechanically characterize tissue. We present images of a three-layer silicone tissue phantom and rat tumor tissue ex vivo, based on quantitative strain rate. Both acquisition speed and processing speed are improved dramatically compared with previous OCE imaging techniques. With high resolution, high acquisition speed, and the ability to characterize the mechanical properties of tissue, this OCE technique has potential use in non-destructive volumetric imaging and clinical applications. PMID:20588552

  2. Dynamic spectral-domain optical coherence elastography for tissue characterization

    PubMed Central

    Liang, Xing; Adie, Steven G.; John, Renu; Boppart, Stephen A.

    2010-01-01

    A dynamic spectral-domain optical coherence elastography (OCE) imaging technique is reported. In this technique, audio-frequency compressive vibrations are generated by a piezoelectric stack as external excitation, and strain rates in the sample are calculated and mapped quantitatively using phase-sensitive spectral-domain optical coherence tomography. At different driving frequencies, this technique provides contrast between sample regions with different mechanical properties, and thus is used to mechanically characterize tissue. We present images of a three-layer silicone tissue phantom and rat tumor tissue ex vivo, based on quantitative strain rate. Both acquisition speed and processing speed are improved dramatically compared with previous OCE imaging techniques. With high resolution, high acquisition speed, and the ability to characterize the mechanical properties of tissue, this OCE technique has potential use in non-destructive volumetric imaging and clinical applications. PMID:20588552

  3. Use of atomic force microscopy for characterizing damage evolution during fatigue

    NASA Astrophysics Data System (ADS)

    Cretegny, Laurent

    2000-10-01

    A study of the development of surface fatigue damage in PH 13-8 Mo stainless steel and copper by atomic force microscopy (AFM) was performed. AFM observations allow highly automated, quantitative characterization of surface deformation with a resolution of 5 nm or better, which is ideal for understanding fatigue damage evolution. A secondary objective was to establish a correlation between fatigue life exhausted and impedance spectroscopy. Strain controlled fatigue tests were conducted both in high and low cycle fatigue regimes, and interruptions of the fatigue tests allowed characterizing the evolution of the surface upset at various life-fractions. In the low strain amplitude tests on stainless steel (Deltaepsilonpl/2 = 0.0026%), surface damage occurred in the shape of narrow streaks at the interface between martensite laths where reverted austenite was present. The streaks eventually coalesced to form crack nuclei. In high strain amplitude tests (Deltaepsilon pl/2 = 0.049%), fatigue surface damage was essentially dominated by the formation of extrusions. In copper, both low (Deltaepsilonpl/2 = 0.061%) and high (Deltaepsilonpl/2 = 0.134%) strain amplitude tests showed the formation of slip bands (mainly extrusions) across entire grains. Protrusions were present only in copper specimens tested at the high strain amplitude. Crack nucleation in the low strain amplitude tests occurred in both materials at the interface between a region that sustained a high level of deformation and one with little evidence of surface upset. This commonality between these two materials that are otherwise very dissimilar in nature suggests a universal scheme for location of fatigue crack nucleation sites during HCF. A procedure was developed in this study to quantitatively characterize the amount of irreversible surface strain. The proposed formalism is applicable to any material, independently of the type of surface damage, and leads to a criterion for crack nucleation based on

  4. Simultaneous quadruple modal nonlinear optical imaging for gastric diseases diagnosis and characterization

    NASA Astrophysics Data System (ADS)

    Wang, Zi; Zheng, Wei; Lin, Jian; Huang, Zhiwei

    2015-03-01

    We report the development of a unique simultaneous quadruple-modal nonlinear optical microscopy (i.e., stimulated Raman scattering (SRS), second-harmonic generation (SHG), two-photon excitation fluorescence (TPEF), and third-harmonic generation (THG)) platform for characterization of the gastric diseases (i.e., gastritis, intestinal metaplasia (IM), intestinal type adenocarcinoma). SRS highlights the goblet cells found in IM. SHG images the distribution of collagen in lamina propria. Collagen is found to aggregate for intestinal type adenocarcinoma. TPEF reveals the cell morphology and can reflect the damage inside glands caused by the diseases. THG visualizes the nuclei with high spatial resolution, which facilitates the identification of neutrophils that are usually used as a feature of inflammation. This work shows that the co-registration of quadruple-modal images can be an effective means for diagnosis and characterization of gastric diseases at the cellular and molecular levels.

  5. Optical characterization of thermal properties of biological tissue

    NASA Astrophysics Data System (ADS)

    Gutierrez-Arroyo, A.; Sánchez Pérez, C.; Alemán-García, N.; Piña-Barba, C.

    2013-11-01

    In this work we utilize heat conduction measurements trough the photothermal beam deflection technique to characterize thermal properties of biological tissue. We design a heat flux sensor based on the phenomenon of photothermal laser beam deflection within a thermo-optic slab (acrylic), where the deflection is quantified by an optical fiber angle sensor. We analytically model the heat flux sensor response based on heat wave propagation theory that well agree with experimental data. We present heat conduction measurements on different tissues applying a heat pulse. Hence we obtain the thermal effusivity coefficient of bovine tendon and chicken liver and heart. It has been shown that thermal conduction depends on the tissués chemical composition as well on their structural arrangements, so any modification in tissue will affect on heat conduction rendering this method potentially useful as an auxiliary in biomedical studies. Nowadays there are several thermal effusivity and diffusivity measurement techniques with classic calorimetry (using thermistors) for research and industrial applications. However there are only few integrated optical devices already proposed, turning this optical technique in an innovative and alternative sensing system for thermal properties characterization.

  6. Electro-optical characterization of GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Olsen, Larry C.; Dunham, Glen; Addis, F. W.; Huber, Dan; Daling, Dave

    1987-01-01

    The electro-optical characterization of gallium arsenide p/n solar cells is discussed. The objective is to identify and understand basic mechanisms which limit the performance of high efficiency gallium arsenide solar cells. The approach involves conducting photoresponse and temperature dependent current-voltage measurements, and interpretation of the data in terms of theory to determine key device parameters. Depth concentration profiles are also utilized in formulating a model to explain device performance.

  7. Characterization of thermomechanical damage on tungsten surfaces during long-duration plasma transients

    NASA Astrophysics Data System (ADS)

    Rivera, David; Crosby, Tamer; Sheng, Andrew; Ghoniem, Nasr M.

    2014-12-01

    A new experimental facility constructed at UCLA for the simulation of high heat flux effects on plasma-facing materials is described. The High Energy Flux Test Facility (HEFTY) is equipped with a Praxair model SG-100 plasma gun, which is nominally rated at 80 kW of continuous operation, of which approximately 30 kW reaches the target due to thermal losses. The gun is used to impart high intermittent heat flux to metal samples mounted within a cylindrical chamber. The system is capable of delivering an instantaneous heat flux in the range of 30-300 MW/m2, depending on sample proximity to the gun. The duration of the plasma heat flux is in the range of 1-1000 s, making it ideal for studies of mild plasma transients of relatively long duration. Tungsten and tungsten-copper alloy metal samples are tested in these transient heat flux conditions, and the surface is characterized for damage evaluation using optical, SEM, XRD, and micro-fabrication techniques. Results from a Finite Element (FE) thermo-elastoplasticity model indicate that during the heat-up phase of a plasma transient pulse, the majority of the sample surface is under compressive stresses leading to plastic deformation of the surface. Upon sample cooling, the recovered elastic strain of cooler parts of the sample exceeds that from parts that deformed plastically, resulting in a tensile surface self-stress (residual surface stress). The intensity of the residual tensile surface stress is experimentally correlated with the onset of complex surface fracture morphology on the tungsten surface, and extending below the surface region. Micro-compression mechanical tests of W micro-pillars show that the material has significant plasticity, failing by a 'barreling' mode before plasma exposure, and by normal dislocation slip and localized shear after plasma exposure. Ongoing modeling of the complex thermo-fracture process, coupled with elasto-plasticity is based on a phase field approach for distributed fracture, and

  8. Common Practice Lightning Strike Protection Characterization Technique to Quantify Damage Mechanisms on Composite Substrates

    NASA Technical Reports Server (NTRS)

    Szatkowski, George N.; Dudley, Kenneth L.; Koppen, Sandra V.; Ely, Jay J.; Nguyen, Truong X.; Ticatch, Larry A.; Mielnik, John J.; Mcneill, Patrick A.

    2013-01-01

    heating parameters which occur during lightning attachment. Following guidance defined in the universal common practice LSP test documents, protected and unprotected CFRP panels were evaluated at 20, 40 and 100KAmps. This report presents analyzed data demonstrating the scientific usefulness of the common practice approach. Descriptions of the common practice CFRP test articles, LSP test bed fixture, and monitoring techniques to capture the electrical, mechanical and thermal parameters during lightning attachment are presented here. Two methods of measuring the electrical currents were evaluated, inductive current probes and a newly developed fiberoptic sensor. Two mechanical displacement methods were also examined, optical laser measurement sensors and a digital imaging correlation camera system. Recommendations are provided to help users implement the common practice test approach and obtain LSP test characterizations comparable across data sets.

  9. Diffractive optics for combined spatial- and mode- division demultiplexing of optical vortices: design, fabrication and optical characterization.

    PubMed

    Ruffato, Gianluca; Massari, Michele; Romanato, Filippo

    2016-01-01

    During the last decade, the orbital angular momentum (OAM) of light has attracted growing interest as a new degree of freedom for signal channel multiplexing in order to increase the information transmission capacity in today's optical networks. Here we present the design, fabrication and characterization of phase-only diffractive optical elements (DOE) performing mode-division (de)multiplexing (MDM) and spatial-division (de)multiplexing (SDM) at the same time. Samples have been fabricated with high-resolution electron-beam lithography patterning a polymethylmethacrylate (PMMA) resist layer spun over a glass substrate. Different DOE designs are presented for the sorting of optical vortices differing in either OAM content or beam size in the optical regime, with different steering geometries in far-field. These novel DOE designs appear promising for telecom applications both in free-space and in multi-core fibers propagation. PMID:27094324

  10. Diffractive optics for combined spatial- and mode- division demultiplexing of optical vortices: design, fabrication and optical characterization

    NASA Astrophysics Data System (ADS)

    Ruffato, Gianluca; Massari, Michele; Romanato, Filippo

    2016-04-01

    During the last decade, the orbital angular momentum (OAM) of light has attracted growing interest as a new degree of freedom for signal channel multiplexing in order to increase the information transmission capacity in today’s optical networks. Here we present the design, fabrication and characterization of phase-only diffractive optical elements (DOE) performing mode-division (de)multiplexing (MDM) and spatial-division (de)multiplexing (SDM) at the same time. Samples have been fabricated with high-resolution electron-beam lithography patterning a polymethylmethacrylate (PMMA) resist layer spun over a glass substrate. Different DOE designs are presented for the sorting of optical vortices differing in either OAM content or beam size in the optical regime, with different steering geometries in far-field. These novel DOE designs appear promising for telecom applications both in free-space and in multi-core fibers propagation.

  11. Diffractive optics for combined spatial- and mode- division demultiplexing of optical vortices: design, fabrication and optical characterization

    PubMed Central

    Ruffato, Gianluca; Massari, Michele; Romanato, Filippo

    2016-01-01

    During the last decade, the orbital angular momentum (OAM) of light has attracted growing interest as a new degree of freedom for signal channel multiplexing in order to increase the information transmission capacity in today’s optical networks. Here we present the design, fabrication and characterization of phase-only diffractive optical elements (DOE) performing mode-division (de)multiplexing (MDM) and spatial-division (de)multiplexing (SDM) at the same time. Samples have been fabricated with high-resolution electron-beam lithography patterning a polymethylmethacrylate (PMMA) resist layer spun over a glass substrate. Different DOE designs are presented for the sorting of optical vortices differing in either OAM content or beam size in the optical regime, with different steering geometries in far-field. These novel DOE designs appear promising for telecom applications both in free-space and in multi-core fibers propagation. PMID:27094324

  12. Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

    SciTech Connect

    Awwal, A; Bauman, B; Gavel, D; Olivier, S; Jones, S; Hardy, J L; Barnes, T; Werner, J S

    2003-02-05

    Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.

  13. Optical tweezers as manufacturing and characterization tool in microfluidics

    NASA Astrophysics Data System (ADS)

    Köhler, J.; Ghadiri, R.; Ksouri, S. I.; Gurevich, E. L.; Ostendorf, A.

    2014-09-01

    Pumping and mixing of small volumes of liquid samples are basic processes in microfluidic applications. Among the number of different principles for active transportation of the fluids microrotors have been investigated from the beginning. The main challenge in microrotors, however, has been the driving principle. In this work a new approach for a very simple magnetic driving principle has been realized. More precisely, we take advantage of optical grippers to fabricate various microrotors and introduce an optical force method to characterize the fluid flow generated by rotating the structures through magnetic actuation. The microrotors are built of silica and magnetic microspheres which are initially coated with Streptavidin or Biotin molecules. Holographic optical tweezers (HOT) are used to trap, to position, and to assemble the microspheres with the chemical interaction of the biomolecules leading to a stable binding. Using this technique, complex designs of microrotors can be realized. The magnetic response of the magnetic microspheres enables the rotation and control of the structures through an external magnetic field. The generated fluid flow around the microrotor is measured optically by inserting a probe particle next to the rotor. While the probe particle is trapped by optical forces the flow force leads to a displacement of the particle from the trapping position. This displacement is directly related to the flow velocity and can be measured and calibrated. Variations of the microrotor design and rotating speed lead to characteristic flow fields.

  14. Characterization of integrated optical CD for process control

    NASA Astrophysics Data System (ADS)

    Yu, Jackie; Uchida, Junichi; van Dommelen, Youri; Carpaij, Rene; Cheng, Shaunee; Pollentier, Ivan; Viswanathan, Anita; Lane, Lawrence; Barry, Kelly A.; Jakatdar, Nickhil

    2004-05-01

    The accurate measurement of CD (critical dimension) and its application to inline process control are key challenges for high yield and OEE (overall equipment efficiency) in semiconductor production. CD-SEM metrology, although providing the resolution necessary for CD evaluation, suffers from the well-known effect of resist shrinkage, making accuracy and stability of the measurements an issue. For sub-100 nm in-line process control, where accuracy and stability as well as speed are required, CD-SEM metrology faces serious limitations. In contrast, scatterometry, using broadband optical spectra taken from grating structures, does not suffer from such limitations. This technology is non-destructive and, in addition to CD, provides profile information and film thickness in a single measurement. Using Timbre's Optical Digital Profililometry (ODP) technology, we characterized the Process Window, using a iODP101 integrated optical CD metrology into a TEL Clean Track at IMEC. We demonstrate the Optical CD's high sensitivity to process change and its insensitivity to measurement noise. We demonstrate the validity of ODP modeling by showing its accurate response to known process changes built into the evaluation and its excellent correlation to CD-SEM. We will further discuss the intrinsic Optical CD metrology factors that affect the tool precision, accuracy and its correlation to CD-SEM.

  15. Spray characterization in high pressure environment using optical line patternator

    NASA Astrophysics Data System (ADS)

    Koh, Hyeonseok; Kim, Dongjun; Shin, Sanghee; Yoon, Youngbin

    2006-08-01

    For the quantitative measurement in an optically dense spray, the intensity of the attenuated signal should be corrected. Therefore, the optical line patternator was applied to get the original distribution of the dense spray injected from a swirl injector at high ambient pressure up to 4.0 MPa. The optical line patternator is a combined technique of laser extinction measurement and image processing for the spray characterization. The spray was scanned with the laser beam and the line image of Mie scattering was captured simultaneously in the path of each laser beam by using a CCD camera. A photo-diode was used to obtain the transmission data that was the amount of the incident laser beam passing through the spray region. The distribution of the attenuation coefficients in the spray was obtained by processing the transmission data and Mie-scattering distribution data by an algebraic reconstruction technique. From the distribution of attenuation coefficients, we can obtain the accurate surface distribution from the Mie-scattering signal. Because the optical line patternator uses a laser beam instead of a laser sheet to scan the spray, the effect of multiple scattering, due to the increased number density of droplets in a high pressure environment is reduced significantly. The optical line patternator is suitable for investigating the characteristics of a relatively large spray under high pressure environments such as liquid rocket engines.

  16. Fabrication of monodispersed silver nanoparticles and their optical characterizations

    NASA Astrophysics Data System (ADS)

    Lama, Pemba

    This dissertation is about the fabrication of monodispersed (same size, shape, composition, structure, etc.) silver nanoparticles in gas media and their optical characterizations such as optical absorption, nonlinear optical response and plasmon assisted fluorescence. The first part of the thesis presents the fabrication method used to prepare monodispersed silver (Ag) nanoparticles (NPs) using heterogeneous condensation in gas media. Well defined and charged Ag NPs were separated based on their sizes by applying an electric field on unipolar charged Ag NPs and were collected on quartz substrates. Thin films consisting of monodispersed Ag NPs with size ranging from 35 nm to 120 nm were prepared by varying an applied electric field during the fabrication process. Scanning electron microscope (SEM) results showed that the samples have a uniform size distribution. In the second part of the thesis, optical characterization, including linear and nonlinear optical properties, are performed on monodispersed and polydispersed Ag NPs and analyzed. A strong plasmon resonance was observed for the monodispersed Ag NPs due to the coherent oscillations of the conduction band electrons, owing to the uniform size of the Ag NPs. Narrow extinction widths (~ 41 nm to ~ 69 nm) were observed for the Ag NPs compared to the width of the polydispersed Ag sample. Nonlinear optical characterizations were also performed on monodispersed silver (Ag) nanoparticles (NPs) of various sizes using a picosecond Z-scan technique with excitation wavelengths at 532 nm and 1064 nm. The nonlinear refraction values were higher for the monodispersed Ag NPs whose surface plasmon resonance (SPR) peak is closer to the excitation wavelength. The higher nonlinear optical response is explained in terms of an electric field enhancement near the SPR. Finally, plasmon assisted fluorescence of Rhodamine B dye was also investigated. Higher fluorescence quantum yield was obtained from Rhodamine B when using

  17. Damage monitoring using fiber optic sensors and by analysing electro-mechanical admittance signatures obtained from piezo sensor

    NASA Astrophysics Data System (ADS)

    Maheshwari, Muneesh; Annamdas, Venu Gopal M.; Pang, John Hock Lye; Tjin, Swee C.; Asundi, Anand

    2015-12-01

    Damage monitoring is the need of the hour in this age of infrastructure. Many methods are being used for damage monitoring in different mechanical and civil structures. Some of them are strain based methods in which abruptly increased strain signifies the presence of damage in the structure. This article focuses on crack monitoring of a fixedfixed beam using fiber optic sensors which can measure strain locally or globally. The two types of fiber optic sensors used in this research are fiber Bragg grating (FBG) and fiber optic polarimetric sensors (FOPS). FBG and FOPS are used for local strain monitoring (at one point only) and global strain monitoring (in the entire specimen) respectively. At the centre of the specimen, a piezoelectric wafer active sensor (PWAS) is also attached. PWAS is used to obtain electromechanical admittance (EMA) signatures. Further, these EMA signatures are analysed to access the damage state in the beam. These multiple smart materials together provide improved information on damages in the specimen which is very valuable for the structural health monitoring (SHM) of the specimen.

  18. Identification and Characterization of Trichoderma Species Damaging Shiitake Mushroom Bed-Logs Infested by Camptomyia Pest.

    PubMed

    Kim, Jun Young; Kwon, Hyuk Woo; Yun, Yeo Hong; Kim, Seong Hwan

    2016-05-28

    The shiitake mushroom industry has suffered from Camptomyia (gall midges) pest, which feeds on the mycelium of shiitake mushroom during its cultivation. It has been postulated that fungal damage of shiitake bed-logs is associated with infestation by the insect pest, but this is not well understood. To understand the fungal damage associated with Camptomyia pest, various Trichoderma species were isolated, identified, and characterized. In addition to two previously known Trichoderma species, T. citrinoviride and T. deliquescens, two other Trichoderma species, T. harzianum and T. atroviride, were newly identified from the pestinfested bed-log samples obtained at three mushroom farms in Cheonan, Korea. Among these four species, T. harzianum was the most evident. The results of a chromogenic media-based assay for extracellular enzymes showed that these four species have the ability to produce amylase, carboxyl-methyl cellulase, avicelase, pectinase, and β-glucosidase, thus indicating that they can degrade wood components. A dual culture assay on PDA indicated that T. harzianum, T. atroviride, and T. citrinoviride were antagonistic against the mycelial growth of a shiitake strain (Lentinula edodes). Inoculation tests on shiitake bed-logs revealed that all four species were able to damage the wood of bed-logs. Our results provide evidence that the four green mold species are the causal agents involved in fungal damage of shiitake bed-logs infested by Camptomyia pest. PMID:26930351

  19. Age- and diet-associated metabolome remodeling characterizes the aging process driven by damage accumulation

    PubMed Central

    Avanesov, Andrei S; Ma, Siming; Pierce, Kerry A; Yim, Sun Hee; Lee, Byung Cheon; Clish, Clary B; Gladyshev, Vadim N

    2014-01-01

    Aging is thought to be associated with increased molecular damage, but representative markers vary across conditions and organisms, making it difficult to assess properties of cumulative damage throughout lifespan. We used nontargeted metabolite profiling to follow age-associated trajectories of >15,000 metabolites in Drosophila subjected to control and lifespan-extending diets. We find that aging is associated with increased metabolite diversity and low-abundance molecules, suggesting they include cumulative damage. Remarkably, the number of detected compounds leveled-off in late-life, and this pattern associated with survivorship. Fourteen percent of metabolites showed age-associated changes, which decelerated in late-life and long-lived flies. In contrast, known metabolites changed in abundance similarly to nontargeted metabolites and transcripts, but did not increase in diversity. Targeted profiling also revealed slower metabolism and accumulation of lifespan-limiting molecules. Thus, aging is characterized by gradual metabolome remodeling, and condition- and advanced age-associated deceleration of this remodeling is linked to mortality and molecular damage. DOI: http://dx.doi.org/10.7554/eLife.02077.001 PMID:24843015

  20. An investigation of the chemical and physical properties of pristine, electrochromically damaged, and photochromically damaged KTiOPO{sub 4} (KTP) using surface analytical and optical spectroscopic techniques

    SciTech Connect

    Quagliano, J.R.; Petrin, R.R.; Trujillo, T.C.; Cockroft, N.J.; Paffett, M.T.; Havrilla, G.; Maggiore, C.J.; Jacco, J.C.

    1994-10-01

    Single-crystal KTiOPO{sub 4} (KTP) is widely used as a nonlinear optical material in optics and lasers, but it can suffer irreversible damage from intense electric and electromagnetic fields; impurities, defects, vacancies, and electron/hole transfers are probably involved. This report shows results of surface and near-surface (bulk) studies using SIMS, Rutherford backscattering, PIXE, channeling, and XRF. The electrochromic damage may occur upon reduction of Ti{sup 4+} to Ti{sup 3+} by trapping electrons passing through the ion channels. Jahn-Teller distortions and Ti{sup 3+} absorption could produce the dark macroscopi damage. The claim that Ag ions could travel through the ion channels, is discounted by the RBS and SIMS data. RBS does suggest Ti ion migration, but this is not likely, according to the KTP structure and lack of Ti ion enhancement in the white residue. The 355 nm radiation could be absorbed into the UV band edge to inititate a photochemical process (gray tracking), which could be the charge transfer from the oxide ligand to Ti{sup 4+} to create Ti{sup 3+}.

  1. Nondestructive Evaluation (NDE) for Characterizing Oxidation Damage in Cracked Reinforced Carbon-Carbon

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Jacobson, Nathan S.; Rauser, Richard W.; Wincheski, Russell A.; Walker, James L.; Cosgriff, Laura A.

    2010-01-01

    In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter's thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using nondestructive evaluation (NDE) methods. These specimens were heat treated in air at 1143 C and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3mm. Single-sided NDE methods were used because they might be practical for on-wing inspection, while X-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally cracked coating and subsequent oxidation damage was also studied with X-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating.

  2. Nondestructive Evaluation (NDE) for Characterizing Oxidation Damage in Cracked Reinforced Carbon-Carbon (RCC)

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Rauser, Richard W.; Jacobson, Nathan S.; Wincheski, Russell A.; Walker, James L.; Cosgriff, Laura A.

    2009-01-01

    In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter's thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using nondestructive evaluation (NDE) methods. These specimens were heat treated in air at 1143 and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3 mm. Single-sided NDE methods were used since they might be practical for on-wing inspection, while x-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally-cracked coating and subsequent oxidation damage was also studied with x-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating.

  3. Investigations on structural, optical, dielectric, laser damage threshold and NLO properties of 2-amino-5-nitropyridinium p-tolunesulfonate (2A5NPT) single crystal

    NASA Astrophysics Data System (ADS)

    Pandian, Muthu Senthil; Sivasubramani, V.; Ramasamy, P.

    2016-05-01

    The highly efficient organic nonlinear optical (NLO) 2-amino-5-nitropyridinium p-tolunesulfonate single crystals have been grown by conventional slow evaporation technique using Millipore water as a solvent in the period of 60 days. The single crystal XRD confirms the unit cell parameters of the grown crystal. The morphology of the grown crystal was analyzed using Bruker-Kappa APEXII single crystal instrument and their planes are identified. The optical transmittance range and the cut-off wavelength are recorded using UV-Visible NIR characterization. The laser damage threshold (LDT) studies were carried out using Nd:YAG laser and LDT value was found to be 3.7 GW/cm2. The dielectric constant and dielectric loss of 2A5NPT single crystals were measured. The SHG efficiency was tested by powder Kurtz-Perry technique and the SHG efficiency is 15 times greater than that of standard KDP material.

  4. Optical Coherence Tomography Compared With Colposcopy for Assessment of Vaginal Epithelial Damage: A Randomized Controlled Trial

    PubMed Central

    Vincent, Kathleen L.; Stanberry, Lawrence R.; Moench, Thomas R.; Breitkopf, Carmen Radecki; Loza, Melissa L.; Wei, Jingna; Grady, James; Paull, Jeremy; Motamedi, Massoud; Rosenthal, Susan L.

    2011-01-01

    Objective Colposcopy has been used to detect epithelial damage with vaginal microbicides. In animal models, optical coherence tomography (OCT) provided increased sensitivity over colposcopy in detecting epithelial injury. This randomized double-blinded clinical study compared OCT to colposcopy for the evaluation of epithelial injury in women using placebo or nonoxynol-9. Methods Thirty women aged 18–45 were randomized to use hydroxyethyl cellulose placebo or nonoxynol-9 vaginal gel twice daily for 5.5 days. Imaging with colposcopy and OCT was performed prior to product use, after the last dose, and 1 week later. Colposcopy was graded using standard criteria. OCT images were scored for epithelial integrity based on a published scoring system and measured for epithelial thickness. Results Colposcopy findings and OCT scores and epithelial thicknesses were similar between treatment groups at baseline. After treatment, there were significant differences between the nonoxynol-9 (1.37) and control group (1.15) OCT scores (p<0.001, indicating epithelial injury, and there was epithelial thinning in the nonoxynol-9 group (237μm) compared to the control group (292μm) (p=0.008). There were no significant posttreatment colposcopic differences in epithelial disruption between treatment groups, with only increased erythema noted after nonoxynol-9 use (p=0.02). Conclusion OCT detected epithelial disruption and thinning not identified by colposcopy. Vaginal epithelial thickness, a measure previously available only through biopsy, decreased after nonoxynol-9 use, a finding that may contribute to increased susceptibility to HIV after frequent use. OCT shows promise for the noninvasive clinical assessment of vaginal epithelial damage. Clinical Trial Registration UMIN Clinical Trials Registry, www.umin.ac.jp/ctr/index.htm, R000006186. PMID:22105265

  5. Thin gold layer in Ni electroforming process: optical surface characterization

    NASA Astrophysics Data System (ADS)

    Sironi, G.; Spiga, D.; Pareschi, G.; Missaglia, N.; Paganini, L.

    2009-08-01

    Mandrel replication by Nickel electroforming is a well-suited process to manufacture X-ray mirrors, making use of Gold layer playing the twofold role of release agent and reflective coating. To increase the optical performances of mirrors it is crucial to minimize the impact of X-ray scattering effects related to surface microroughness, especially when the mirror is intended to operate in hard X-rays. In this case, the Gold layer simply acts as release agent because the reflection is demanded to interferential over-coatings. Even though the replicated optical surface is usually believed to reproduce the smooth topography of the master, a surface degradation is commonly observed. Such a worsening can also suffer from a contribution from the spontaneous roughness growth of the Gold layer itself: if this is the case, the mirror's optical quality could potentially benefit from the utilization of a thin Gold layer (< 100 nm) instead of the traditional thick gold layer (> 100 nm). To prove the effectiveness of the Gold thickness reduction, a microroughness characterization of replicated thin gold layers has been achieved. We report here a preliminary roughness study of 3 electroformed Ni samples replicated from a super-polished Zerodur flat master with various Gold layer thicknesses, in the spectral range 0.02-1000 μm. The study is organized as follows: (a) characterization of the 3 replicated samples; (b) comparison of the Gold roughness for thin vs. thick layers; (c) comparison of the two sides of Gold layers.

  6. Optical and Chemical Characterization of Aerosols Produced from Cooked Meats

    NASA Astrophysics Data System (ADS)

    Niedziela, R. F.; Foreman, E.; Blanc, L. E.

    2011-12-01

    Cooking processes can release a variety compounds into the air immediately above a cooking surface. The distribution of compounds will largely depend on the type of food that is being processed and the temperatures at which the food is prepared. High temperatures release compounds from foods like meats and carry them away from the preparation surface into cooler regions where condensation into particles can occur. Aerosols formed in this manner can impact air quality, particularly in urban areas where the amount of food preparation is high. Reported here are the results of laboratory experiments designed to optically and chemically characterize aerosols derived from cooking several types of meats including ground beef, salmon, chicken, and pork both in an inert atmosphere and in synthetic air. The laboratory-generated aerosols are studied using a laminar flow cell that is configured to accommodate simultaneous optical characterization in the mid-infrared and collection of particles for subsequent chemical analysis by gas chromatography. Preliminary optical results in the visible and ultra-violet will also be presented.

  7. Characterization of total ionizing dose damage in COTS pinned photodiode CMOS image sensors

    NASA Astrophysics Data System (ADS)

    Wang, Zujun; Ma, Wuying; Huang, Shaoyan; Yao, Zhibin; Liu, Minbo; He, Baoping; Liu, Jing; Sheng, Jiangkun; Xue, Yuan

    2016-03-01

    The characterization of total ionizing dose (TID) damage in COTS pinned photodiode (PPD) CMOS image sensors (CISs) is investigated. The radiation experiments are carried out at a 60Co γ-ray source. The CISs are produced by 0.18-μm CMOS technology and the pixel architecture is 8T global shutter pixel with correlated double sampling (CDS) based on a 4T PPD front end. The parameters of CISs such as temporal domain, spatial domain, and spectral domain are measured at the CIS test system as the EMVA 1288 standard before and after irradiation. The dark current, random noise, dark signal non-uniformity (DSNU), photo response non-uniformity (PRNU), overall system gain, saturation output, dynamic range (DR), signal to noise ratio (SNR), quantum efficiency (QE), and responsivity versus the TID are reported. The behaviors of the tested CISs show remarkable degradations after radiation. The degradation mechanisms of CISs induced by TID damage are also analyzed.

  8. Debris and radiation-induced damage effects on EUV nanolithography source collector mirror optics performance.

    SciTech Connect

    Allain, J. P.; Nieto, M.; Hendricks, M.; Harilal, S. S.; Hassanein, A.; Mathematics and Computer Science

    2007-01-01

    Exposure of collector mirrors facing the hot, dense pinch plasma in plasma-based EUV light sources to debris (fast ions, neutrals, off-band radiation, droplets) remains one of the highest critical issues of source component lifetime and commercial feasibility of nanolithography at 13.5-nm. Typical radiators used at 13.5-nm include Xe and Sn. Fast particles emerging from the pinch region of the lamp are known to induce serious damage to nearby collector mirrors. Candidate collector configurations include either multi-layer mirrors (MLM) or single-layer mirrors (SLM) used at grazing incidence. Studies at Argonne have focused on understanding the underlying mechanisms that hinder collector mirror performance at 13.5-nm under fast Sn or Xe exposure. This is possible by a new state-of-the-art in-situ EUV reflectometry system that measures real time relative EUV reflectivity (15-degree incidence and 13.5-nm) variation during fast particle exposure. Intense EUV light and off-band radiation is also known to contribute to mirror damage. For example offband radiation can couple to the mirror and induce heating affecting the mirror's surface properties. In addition, intense EUV light can partially photo-ionize background gas (e.g., Ar or He) used for mitigation in the source device. This can lead to local weakly ionized plasma creating a sheath and accelerating charged gas particles to the mirror surface and inducing sputtering. In this paper we study several aspects of debris and radiation-induced damage to candidate EUVL source collector optics materials. The first study concerns the use of IMD simulations to study the effect of surface roughness on EUV reflectivity. The second studies the effect of fast particles on MLM reflectivity at 13.5-nm. And lastly the third studies the effect of multiple energetic sources with thermal Sn on 13.5-nm reflectivity. These studies focus on conditions that simulate the EUVL source environment in a controlled way.

  9. Holographic frequency resolved optical gating for spatio-temporal characterization of ultrashort optical pulse

    NASA Astrophysics Data System (ADS)

    Mehta, Nikhil; Yang, Chuan; Xu, Yong; Liu, Zhiwen

    2014-09-01

    We introduce a novel method for characterizing the spatio-temporal evolution of ultrashort optical field by recording the spectral hologram of frequency resolved optical gating (FROG) trace. We show that FROG holography enables the measurement of phase (up to an overall constant) and group delay of the pulse which cannot be measured by conventional FROG method. To illustrate our method, we perform numerical simulation to generate holographic collinear FROG (cFROG) trace of a chirped optical pulse and retrieve its complex profile at multiple locations as it propagates through a hypothetical dispersive medium. Further, we experimentally demonstrate our method by retrieving a 67 fs pulse at three axial locations in the vicinity of focus of an objective lens and compute its group delay.

  10. Formation of plasma induced surface damage in silica glass etching for optical waveguides

    NASA Astrophysics Data System (ADS)

    Choi, D. Y.; Lee, J. H.; Kim, D. S.; Jung, S. T.

    2004-06-01

    Ge, B, P-doped silica glass films are widely used as optical waveguides because of their low losses and inherent compatibility with silica optical fibers. These films were etched by ICP (inductively coupled plasma) with chrome etch masks, which were patterned by reactive ion etching (RIE) using chlorine-based gases. In some cases, the etched surfaces of silica glass were very rough (root-mean square roughness greater than 100 nm) and we call this phenomenon plasma induced surface damage (PISD). Rough surface cannot be used as a platform for hybrid integration because of difficulty in alignment and bonding of active devices. PISD reduces the etch rate of glass and it is very difficult to remove residues on a rough surface. The objective of this study is to elucidate the mechanism of PISD formation. To achieve this goal, PISD formation during different etching conditions of chrome etch mask and silica glass was investigated. In most cases, PISD sources are formed on a glass surface after chrome etching, and metal compounds are identified in theses sources. Water rinse after chrome etching reduces the PISD, due to the water solubility of metal chlorides. PISD is decreased or even disappeared at high power and/or low pressure in glass etching, even if PISD sources were present on the glass surface before etching. In conclusion, PISD sources come from the chrome etching process, and polymer deposition on these sources during the silica etching cause the PISD sources to grow. In the area close to the PISD source there is a higher ion flux, which causes an increase in the etch rate, and results in the formation of a pit.

  11. Mechanical force characterization in manipulating live cells with optical tweezers.

    PubMed

    Wu, Yanhua; Sun, Dong; Huang, Wenhao

    2011-02-24

    Laser trapping with optical tweezers is a noninvasive manipulation technique and has received increasing attentions in biological applications. Understanding forces exerted on live cells is essential to cell biomechanical characterizations. Traditional numerical or experimental force measurement assumes live cells as ideal objects, ignoring their complicated inner structures and rough membranes. In this paper, we propose a new experimental method to calibrate the trapping and drag forces acted on live cells. Binding a micro polystyrene sphere to a live cell and moving the mixture with optical tweezers, we can obtain the drag force on the cell by subtracting the drag force on the sphere from the total drag force on the mixture, under the condition of extremely low Reynolds number. The trapping force on the cell is then obtained from the drag force when the cell is in force equilibrium state. Experiments on numerous live cells demonstrate the effectiveness of the proposed force calibration approach. PMID:21087769

  12. Kullback relative entropy and characterization of partially polarized optical waves.

    PubMed

    Réfrégier, Philippe; Goudail, François

    2006-03-01

    Different properties of partially polarized light are discussed using the Kullback relative entropy, which provides a physically meaningful measure of proximity between probability density functions (PDFs). For optical waves with a Gaussian PDF, the standard degree of polarization is a simple function of the Kullback relative entropy between the considered optical light and a totally depolarized light of the same intensity. It is shown that the Kullback relative entropies between different PDFs allow one to define other properties such as a degree of anisotropy and a degree of non-Gaussianity. It is also demonstrated that, in dimension three, the Kullback relative entropy between a partially polarized light and a totally depolarized light can lead to natural definitions of two degrees of polarization needed to characterize the polarization state. These analyses enlighten the physical meaning of partial polarization of light waves in terms of a measure of disorder provided by the Shannon entropy. PMID:16539066

  13. System and method for laser-based, non-evaporative repair of damage sites in the surfaces of fused silica optics

    DOEpatents

    Adams, John J.; Bolourchi, Masoud; Bude, Jeffrey D.; Guss, Gabriel M.; Jarboe, Jeffery A.; Matthews, Manyalibo J.; Nostrand, Michael C; Wegner, Paul J.

    2016-09-06

    A method for repairing a damage site on a surface of an optical material is disclosed. The method may involve focusing an Infrared (IR) laser beam having a predetermined wavelength, with a predetermined beam power, to a predetermined full width ("F/W") 1/e.sup.2 diameter spot on the damage site. The focused IR laser beam is maintained on the damage site for a predetermined exposure period corresponding to a predetermined acceptable level of downstream intensification. The focused IR laser beam heats the damage site to a predetermined peak temperature, which melts and reflows material at the damage site of the optical material to create a mitigated site.

  14. Spectral-Domain Optical Coherence Tomography as a Noninvasive Method to Assess Damaged and Regenerating Adult Zebrafish Retinas

    PubMed Central

    Bailey, Travis J.; Davis, Darin H.; Vance, Joseph E.; Hyde, David R.

    2012-01-01

    Purpose. These experiments assessed the ability of spectral-domain optical coherence tomography (SD-OCT) to accurately represent the structural organization of the adult zebrafish retina and reveal the dynamic morphologic changes during either light-induced damage and regeneration of photoreceptors or ouabain-induced inner retinal damage. Methods. Retinas of control dark-adapted adult albino zebrafish were compared with retinas subjected to 24 hours of constant intense light and recovered for up to 8 weeks or ouabain-damaged retinas that recovered for up to 3 weeks. Images were captured and the measurements of retinal morphology were made by SD-OCT, and then compared with those obtained by histology of the same eyes. Results. Measurements between SD-OCT and histology were very similar for the undamaged, damaged, and regenerating retinas. Axial measurements of SD-OCT also revealed vitreal morphology that was not readily visualized by histology. Conclusions. SD-OCT accurately represented retinal lamination and photoreceptor loss and recovery during light-induced damage and subsequent regeneration. SD-OCT was less accurate at detecting the inner nuclear layer in ouabain-damaged retinas, but accurately detected the undamaged outer nuclear layer. Thus, SD-OCT provides a noninvasive and quantitative method to assess the morphology and the extent of damage and repair in the zebrafish retina. PMID:22499984

  15. Characterization of corneal damage from Pseudomonas aeruginosa infection by the use of multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Lin; Chen, Wei-Liang; Lo, Wen; Chen, Shean-Jen; Tan, Hsin-Yuan; Dong, Chen-Yuan

    2010-11-01

    Using multiphoton autofluorescence (MAF) and second harmonic generation (SHG) microscopy, we investigate the morphology and the structure of the corneal epithelium and stroma collagen of bovine cornea following injection of Pseudomonas aeruginosa. We found that corneal epithelial cells are damaged and stromal collagen becoming increasingly autofluorescent with time. We also characterized infected cornea cultured for 0, 6, 12, and 24 h by quantitative ratiometric MAF to SHG index (MAFSI) analysis. MAFSI results show that the destruction of the stromal collagen corresponds to a decrease in SHG intensity and increase of MAF signal with time.

  16. Comparisons between laser damage and optical electric field behaviors for hafnia/silica antireflection coatings

    SciTech Connect

    Bellum, John; Kletecka, Damon; Rambo, Patrick; Smith, Ian; Schwarz, Jens; Atherton, Briggs

    2011-03-20

    We compare designs and laser-induced damage thresholds (LIDTs) of hafnia/silica antireflection (AR) coatings for 1054 nm or dual 527 nm/1054 nm wavelengths and 0 deg. to 45 deg. angles of incidence (AOIs). For a 527 nm/1054 nm, 0 deg. AOI AR coating, LIDTs from three runs arbitrarily selected over three years are {approx}20 J/cm{sup 2} or higher at 1054 nm and <10 J/cm{sup 2} at 527 nm. Calculated optical electric field intensities within the coating show two intensity peaks for 527 nm but not for 1054 nm, correlating with the lower (higher) LIDTs at 527 nm (1054 nm). For 1054 nm AR coatings at 45 deg. and 32 deg. AOIs and S and P polarizations (Spol and Ppol), LIDTs are high for Spol (>35 J/cm{sup 2}) but not as high for Ppol (>30 J/cm{sup 2} at 32 deg. AOI; {approx}15 J/cm{sup 2} at 45 deg. AOI). Field intensities show that Ppol discontinuities at media interfaces correlate with the lower Ppol LIDTs at these AOIs. For Side 1 and Side 2 dual 527 nm/1054 nm AR coatings of a diagnostic beam splitter at 22.5 deg. AOI, Spol and Ppol LIDTs (>10 J/cm{sup 2} at 527 nm; >35 J/cm{sup 2} at 1054 nm) are consistent with Spol and Ppol intensity behaviors.

  17. Electrochromic conducting polymers: optical contrast characterization of chameleonic materials.

    PubMed

    Padilla, Javier; Otero, Toribio F

    2008-09-01

    The optical characterization in the visible wavelength range was obtained for an electrochromic material, poly-3, 4-ethylenedioxy-thiophene (PEDOT), as a function of its redox charge density (charge consumed for the color change between its maximum and minimum absorbance states). The experimental procedure was kept very simple and all the information can be obtained from only one film, including the identification of the maximum achievable contrast for the material. Different films of the electrochromic material were tested in order to check the validity of the predicted values, showing excellent agreement. PMID:18667759

  18. Self-characterization of linear and nonlinear adaptive optics systems.

    PubMed

    Hampton, Peter J; Conan, Rodolphe; Keskin, Onur; Bradley, Colin; Agathoklis, Pan

    2008-01-10

    We present methods used to determine the linear or nonlinear static response and the linear dynamic response of an adaptive optics (AO) system. This AO system consists of a nonlinear microelectromechanical systems deformable mirror (DM), a linear tip-tilt mirror (TTM), a control computer, and a Shack-Hartmann wavefront sensor. The system is modeled using a single-input-single-output structure to determine the one-dimensional transfer function of the dynamic response of the chain of system hardware. An AO system has been shown to be able to characterize its own response without additional instrumentation. Experimentally determined models are given for a TTM and a DM. PMID:18188192

  19. Characterization of an interferometric optical sieve for particle sorting

    NASA Astrophysics Data System (ADS)

    Volke-Sepulveda, K.; Ramos-García, R.; Ricardez-Vargas, I.

    2006-08-01

    We present a detailed theoretical discussion and experimental analysis of an interferometric optical trapping device that allows efficient sorting of particles, including biological samples, either by size or refractive index. This technique involves no microfluidic flow, but it is based on the specific response of different microparticles to an interference pattern of fringes vibrating with a periodic but non-symmetric time modulation function. The performance of the system is analyzed in terms of the different control parameters, such as the period of the fringes, the vibration amplitude and frequency, and the power level in the sample. We discuss the possibility of using this system to characterize unknown samples.

  20. Characterization of photochromic computer-generated holograms for optical testing

    NASA Astrophysics Data System (ADS)

    Pariani, Giorgio; Bertarelli, Chiara; Bianco, Andrea; Schaal, Frederik; Pruss, Christof

    2012-09-01

    We investigate the possibility to produce photochromic CGHs with maskless lithography methods. For this purpose, optical properties and requirements of photochromic materials will be shown. A diarylethene-based polyurethane is developed and characterized. The resolution limit and the in uence of the writing parameters on the produced patterns, namely speed rate and light power, have been determined. After the optimization of the writing process, gratings and Fresnel Zone Plates are produced on the photochromic layer and diraction eciencies are measured. Improvements and perspectives will be discussed.

  1. Development and characterization of monolithic multilayer Laue lens nanofocusing optics

    NASA Astrophysics Data System (ADS)

    Nazaretski, E.; Xu, W.; Bouet, N.; Zhou, J.; Yan, H.; Huang, X.; Chu, Y. S.

    2016-06-01

    We have developed an experimental approach to bond two independent linear Multilayer Laue Lenses (MLLs) together. A monolithic MLL structure was characterized using ptychography at 12 keV photon energy, and we demonstrated 12 nm and 24 nm focusing in horizontal and vertical directions, respectively. Fabrication of 2D MLL optics allows installation of these focusing elements in more conventional microscopes suitable for x-ray imaging using zone plates, and opens easier access to 2D imaging with high spatial resolution in the hard x-ray regime.

  2. Study on laser damage of high transmission single layer optical thin film for fused silica glass induced by inclusion

    NASA Astrophysics Data System (ADS)

    Hao, Ming-ming; Lu, Guo-guang; Zhu, Hong-bo; Wang, Li-na

    2015-08-01

    In order to research the laser damage mechanism of high transmission single layer optical thin film for fused silica glass, finite element method was used to calculate laser induced damage threshold (LIDT) and an optical test system with a nanosecond solid-state lasers was set up to determine the LIDT according to standard of ISO 11254. Firstly, finite element model was created at COMSOL multi-physics software and the temperature of inclusion in the optical thin film was calculated with different physical parameter. It is found that temperature at center of the inclusion firstly decreases and then increase with the increasing of inclusion depth. It is also found that the temperature constantly increase with the radius increasing from 20nm to 100nm. Moreover, the inclusion temperature for MgF2 thin film is higher than that of CaF2 thin film. Lastly, LIDT were measured by the optical test system, and the average value of LIDT is 3.7J/cm2 for MgF2 thin film and 4.6J/cm2 for CaF2 thin film, which is well fit with the value calculated by COMSOL software. The study shows that finite element method is an effective method to calculate LIDT for optical thin film and impurity has significant impact on the LIDT of optical thin film and therefore decreasing the density of the impurity would increase the LIDT of the thin film.

  3. Growth and nonlinear optical characterization of organic single crystal films

    NASA Astrophysics Data System (ADS)

    Zhou, Ligui

    1997-12-01

    Organic single crystal films are important for various future applications in photonics and integrated optics. The conventional method for inorganic crystal growth is not suitable for organic materials, and the high temperature melting method is not good for most organic materials due to decomposition problems. We developed a new method-modified shear method-to grow large area organic single crystal thin films which have exceptional nonlinear optical properties and high quality surfaces. Several organic materials (NPP, PNP and DAST) were synthesized and purified before the thin film crystal growth. Organic single crystal thin films were grown from saturated organic solutions using modified shear method. The area of single crystal films were about 1.5 cm2 for PNP, 1 cm2 for NPP and 5 mm2 for DAST. The thickness of the thin films which could be controlled by the applied pressure ranged from 1μm to 10 μm. The single crystal thin films of organic materials were characterized by polarized microscopy, x-ray diffraction, polarized UV-Visible and polarized micro-FTIR spectroscopy. Polarized microscopy showed uniform birefringence and complete extinction with the rotation of the single crystal thin films under crossed- polarization, which indicated high quality single crystals with no scattering. The surface orientation of single crystal thin films was characterized by x-ray diffraction. The molecular orientation within the crystal was further studied by the polarized UV-Visible and Polarized micro-FTIR techniques combined with the x-ray and polarized microscopy results. A Nd:YAG laser with 35 picosecond pulses at 1064nm wavelength was employed to perform the nonlinear optical characterization of the organic single crystal thin films. Two measurement techniques were used to study the crystal films: second harmonic generation (SHG) and electro-optic (EO) effect. SHG results showed that the nonlinear optical coefficient of NPP was 18 times that of LiNbO3, a standard

  4. Mitigation of Laser Damage Growth in Fused Silica NIF Optics with a Galvanometer Scanned Carbon Dioxide Laser

    SciTech Connect

    Bass, I L; Draggoo, V; Guss, G M; Hackel, R P; Norton, M A

    2006-04-06

    Economic operation of the National Ignition Facility at the Lawrence Livermore National Laboratory depends on controlling growth of laser damage in the large, high cost optics exposed to UV light at 351 nm. Mitigation of the growth of damage sites on fused silica surfaces greater than several hundred microns in diameter has been previously reported by us using galvanometer scanning of a tightly focused 10.6 {micro}m CO{sub 2} laser spot over an area encompassing the laser damage. Further investigation revealed that fused silica vapor re-deposited on the surface as ''debris'' led to laser damage at unexpectedly low fluences when exposed to multiple laser shots at 351 nm. Additionally, laser power and spatial mode fluctuations in the mitigation laser led to poor repeatability of the process. We also found that the shape of the mitigation pit could produce downstream intensification that could damage other NIF optics. Modifications were made to both the laser system and the mitigation process in order to address these issues. Debris was completely eliminated by these changes, but repeatability and downstream intensification issues still persist.

  5. Mitigation of laser damage growth in fused silica NIF optics with a galvanometer scanned CO II laser

    NASA Astrophysics Data System (ADS)

    Bass, Isaac L.; Draggoo, Vaughn G.; Guss, Gabriel M.; Hackel, Richard P.; Norton, Mary A.

    2006-05-01

    Economic operation of the National Ignition Facility at the Lawrence Livermore National Laboratory depends on controlling growth of laser damage in the large, high cost optics exposed to UV light at 351 nm. Mitigation of the growth of damage sites on fused silica surfaces greater than several hundred microns in diameter has been previously reported by us using galvanometer scanning of a tightly focused 10.6 μm CO II laser spot over an area encompassing the laser damage. Further investigation revealed that fused silica vapor re-deposited on the surface as "debris" led to laser damage at unexpectedly low fluences when exposed to multiple laser shots at 351 nm. Additionally, laser power and spatial mode fluctuations in the mitigation laser led to poor repeatability of the process. We also found that the shape of the mitigation pit could produce downstream intensification that could damage other NIF optics. Modifications were made to both the laser system and the mitigation process in order to address these issues. Debris was completely eliminated by these changes, but repeatability and downstream intensification issues still persist.

  6. Interferometric at-wavelength flare characterization of EUV optical systems

    DOEpatents

    Naulleau, Patrick P.; Goldberg, Kenneth Alan

    2001-01-01

    The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) provides the high-accuracy wavefront characterization critical to the development of EUV lithography systems. Enhancing the implementation of the PS/PDI can significantly extend its spatial-frequency measurement bandwidth. The enhanced PS/PDI is capable of simultaneously characterizing both wavefront and flare. The enhanced technique employs a hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI. Using the dual-domain technique in combination with a flare-measurement-optimized mask and an iterative calculation process for removing flare contribution caused by higher order grating diffraction terms, the enhanced PS/PDI can be used to simultaneously measure both figure and flare in optical systems.

  7. Development of integrated damage detection system for international America's Cup class yacht structures using a fiber optic distributed sensor

    NASA Astrophysics Data System (ADS)

    Akiyoshi, Shimada; Naruse, Hiroshi; Uzawa, Kyoshi; Murayama, Hideaki; Kageyama, Kazuro

    2000-06-01

    We constructed a new health monitoring system to detect damage using a fiber optic distributed sensor, namely a Brillouin optical time domain reflectometer (BOTDR), and installed it in International America's Cup Class (IACC) yachts, the Japanese entry in America's Cup 2000. IACC yachts are designed to be as fast as possible, so it is essential that they are lightweight and encounter minimum water resistance. Advanced composite sandwich structures, made with carbon fiber reinforced plastic (CFRP) skins and a honeycomb core, are used to achieve the lightweight structure. Yacht structure designs push the strength of the materials to their limit and so it is important to detect highly stressed or damaged regions that might cause a catastrophic fracture. The BOTDR measures changes in the Brillouin frequency shift caused by distributed strain along one optical fiber. We undertook two experiments: a pulling test and a four point bending test on a composite beam. The former showed that no slippage occurred between the optical fiber glass and its coating. The latter confirmed that a debonding between the skin and the core of 300 mm length could be found with the BOTDR. Next we examined the effectiveness with which this system can assess the structural integrity of IACC yachts. The results show that our system has the potential for use as a damage detection system for smart structures.

  8. X-ray Topography to Characterize Surface Damage on CdZnTe Crystals

    SciTech Connect

    Black, David; Woicik, Joseph; Duff, Martine C.; Hunter, Douglas B.; Burger, Arnold; Groza, Michael

    2008-12-05

    Synthetic CdZnTe or 'CZT' crystals can be used for room temperature detection of {gamma}-radiation. Structural/morphological heterogeneities within CZT, such as twinning, secondary phases (often referred to as inclusions or precipitates), and poly-crystallinity can affect detector performance. As part of a broader study using synchrotron radiation techniques to correlate detector performance to microstructure, x-ray topography (XRT) has been used to characterize CZT crystals. We have found that CZT crystals almost always have a variety of residual surface damage, which interferes with our ability to observe the underlying microstructure for purposes of crystal quality evaluation. Specific structures are identifiable as resulting from fabrication processes and from handling and shipping of sample crystals. Etching was found to remove this damage; however, our studies have shown that the radiation detector performance of the etched surfaces was inferior to the as-polished surface due to higher surface currents which result in more peak tailing and less energy resolution. We have not fully investigated the effects of the various types of inducible damage on radiation detector performance.

  9. X-ray Topography to Characterize Surface Damage on CdZnTe Crystals

    SciTech Connect

    Black, David; Woicik, Joseph; Duff, Martine C.; Hunter, Douglas B.; Burger, Arnold; Groza, Michael

    2008-07-01

    Synthetic CdZnTe or 'CZT' crystals can be used for room temperature detection of {gamma}-radiation. Structural/morphological heterogeneities within CZT, such as twinning, secondary phases (often referred to as inclusions or precipitates), and poly-crystallinity can affect detector performance. As part of a broader study using synchrotron radiation techniques to correlate detector performance to microstructure, x-ray topography (XRT) has been used to characterize CZT crystals. We have found that CZT crystals almost always have a variety of residual surface damage, which interferes with our ability to observe the underlying microstructure for purposes of crystal quality evaluation. Specific structures are identifiable as resulting from fabrication processes and from handling and shipping of sample crystals. Etching was found to remove this damage; however, our studies have shown that the radiation detector performance of the etched surfaces was inferior to the as-polished surface due to higher surface currents which result in more peak tailing and less energy resolution. We have not fully investigated the effects of the various types of inducible damage on radiation detector performance. (authors)

  10. Characterization of Fatigue Damage for Bonded Composite Skin/Stringer Configurations

    NASA Technical Reports Server (NTRS)

    Paris, Isabelle; Cvitkovich, Michael; Krueger, Ronald

    2008-01-01

    The fatigue damage was characterized in specimens which consisted of a tapered composite flange bonded onto a composite skin. Quasi-static tension tests were performed first to determine the failure load. Subsequently, tension fatigue tests were performed at 40%, 50%, 60% and 70% of the failure load to evaluate the debonding mechanisms. For four specimens, the cycling loading was stopped at intervals. Photographs of the polished specimen edges were taken under a light microscope to document the damage. At two diagonally opposite corners of the flange, a delamination appeared to initiate at the flange tip from a matrix crack in the top 45deg skin ply and propagated at the top 45deg/-45deg skin ply interface. At the other two diagonally opposite corners, a delamination running in the bondline initiated from a matrix crack in the adhesive pocket. In addition, two specimens were cut longitudinally into several sections. Micrographs revealed a more complex pattern inside the specimen where the two delamination patterns observed at the edges are present simultaneously across most of the width of the specimen. The observations suggest that a more sophisticated nondestructive evaluation technique is required to capture the complex damage pattern of matrix cracking and multi-level delaminations.

  11. Characterization of damage evolution in an AM60 magnesium alloy by computed tomography

    SciTech Connect

    Waters, A.; Green, R.E.; Martz, H.; Dolan, K.; Horstemeyer, M.; Derrill, R.

    1999-06-16

    Lawrence Livermore National Lab and Sandia National Laboratories, CA are collaborating on the development of new techniques to study damage evolution and growth in material specimens subjected to mechanical loading. These techniques include metallography, radiography, computed tomography (CT) and modeling. The material specimens being studied include cast magnesium and aluminum alloys, and forged stainless steel. The authors concentrate on characterizing monotonically loaded Mg alloy specimens using CT. Several notched tensile specimens were uniaxially loaded to different percentages of the failure load. Specimens were initially characterized by radiography and computed tomography to determine the preloaded state. Subsequent CT scans were performed after the samples were loaded to different percentages of the load failure. The CT volumetric data are being used to measure void size, distribution and orientation in all three dimensions nondestructively to determine the effect of void growth on the mechanical behavior of the materials.

  12. Engine materials characterization and damage monitoring by using x ray technologies

    NASA Technical Reports Server (NTRS)

    Baaklini, George Y.

    1993-01-01

    X ray attenuation measurement systems that are capable of characterizing density variations in monolithic ceramics and damage due to processing and/or mechanical testing in ceramic and intermetallic matrix composites are developed and applied. Noninvasive monitoring of damage accumulation and failure sequences in ceramic matrix composites is used during room-temperature tensile testing. This work resulted in the development of a point-scan digital radiography system and an in situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens, and the latter is used to image the failure behavior of silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. State-of-the-art x ray computed tomography is investigated to determine its capabilities and limitations in characterizing density variations of subscale engine components (e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon-carbide-fiber-reinforced beta titanium matrix rod, rotor, and ring). Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point-scan digital radiography is a viable technique for characterizing density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composites. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using microcollimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross-sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws

  13. Early characterization of occlusal overloaded cervical dental hard tissues by en face optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Marcauteanu, Corina; Negrutiu, Meda; Sinescu, Cosmin; Stoica, Eniko Tunde; Ionita, Ciprian; Florin, Topala; Vasile, Liliana; Bradu, Adrian; Dobre, George; Podoleanu, Adrian G.

    2011-06-01

    Early diagnosis of occlusal overload is an important issue in dental medicine. The high occlusal forces can cause irreversible damage to the dental hard tissues. Our study proposes the early microstructural characterization of occlusal overloaded bicuspids, with abnormal crown morphology, by en face optical coherence tomography (eFOCT). The dental samples were investigated using an eFOCT system operating at 1300 nm in B-scan and C-scan mode. The eFOCT images obtained from these teeth visualized cracks, which didn't reach the tooth surface. The μCT and histological images confirmed the microstructural defects identified on eFOCT images. In conclusion, eFOCT is a promising imaging method for the early diagnosis of occlusal overload on bicuspids with normal crown morphology and for the prophylaxis of dental wear.

  14. Characterization of Gigabit Ethernet Over Highly Turbulent Optical Wireless Links

    SciTech Connect

    Johnson, G W; Cornish, J P; Wilburn, J W; Young, R A; Ruggiero, A J

    2002-07-01

    We report on the performance characterization and issues associated with using Gigabit Ethernet (GigE) over a highly turbulent (C{sub n}{sup 2} > 10{sup -12}) 1.3 km air-optic lasercom links. Commercial GigE hardware is a cost-effective and scalable physical layer standard that can be applied to air-optic communications. We demonstrate a simple GigE hardware interface to a singlemode fiber-coupled, 1550 nm, WDM air-optic transceiver. TCPAP serves as a robust and universal foundation protocol that has some tolerance of data loss due to atmospheric fading. Challenges include establishing and maintaining a connection with acceptable throughput under poor propagation conditions. The most useful link performance diagnostic is shown to be scintillation index, where a value of 0.2 is the maximum permissible for adequate GigE throughput. Maximum GigE throughput observed was 49.7% of that obtained with a fiber jumper when scintillation index is 0.1. Shortcomings in conventional measurements such as bit error rate are apparent. Prospects for forward mor correction and other link enhancements will be discussed.

  15. Implementation of Optical Characterization for Flexible Organic Electronics Applications

    NASA Astrophysics Data System (ADS)

    Laskarakis, A.; Logothetidis, S.

    One of the most rapidly evolving sectors of the modern science and technology is the flexible organic electronic devices (FEDs) that are expected to significantly improve and revolutionize our everyday life. The FED application includes the generation of electricity by renewable sources (by organic photovoltaic cells - OPVs), power storage (thin film batteries), the visualization of information (by organic displays), the working and living environment (ambient lighting, sensors), safety, market (smart labels, radio frequency identification tags - RFID), textiles (smart fabrics with embedded display and sensor capabilities), as well as healthcare (smart sensors for vital sign monitoring), etc. Although there has been important progresses in inorganic-based Si devices, there are numerous advances in the organic (semiconducting, conducting), inorganic, and hybrid (organic-inorganic) materials that exhibit desirable properties and stability, and in the synthesis and preparation methods. The understanding of the organic material properties can lead to the fast progress of the functionality and performance of FEDs. The investigation of the optical properties of these materials can promote the understanding of the optical, electrical, structural properties of organic semiconductors and electrodes and can contribute to the optimization of the synthesis process and the tuning of their structure and morphology. In this chapter, we will describe briefly some of the advances toward the implementation of optical characterization methods, such as Spectroscopic Ellipsometry (SE) from the infrared to the visible and ultraviolet spectral region for the study of materials (flexible polymer substrates, barrier layers, transparent electrodes) to be used for application in the fabrication of FEDs.

  16. Optical distributed sensors for feedback control: Characterization of photorefractive resonator

    NASA Technical Reports Server (NTRS)

    Indebetouw, Guy; Lindner, D. K.

    1992-01-01

    The aim of the project was to explore, define, and assess the possibilities of optical distributed sensing for feedback control. This type of sensor, which may have some impacts in the dynamic control of deformable structures and the monitoring of small displacements, can be divided into data acquisition, data processing, and control design. Analogue optical techniques, because they are noninvasive and afford massive parallelism may play a significant role in the acquisition and the preprocessing of the data for such a sensor. Assessing these possibilities was the aim of the first stage of this project. The scope of the proposed research was limited to: (1) the characterization of photorefractive resonators and the assessment of their possible use as a distributed optical processing element; and (2) the design of a control system utilizing signals from distributed sensors. The results include a numerical and experimental study of the resonator below threshold, an experimental study of the effect of the resonator's transverse confinement on its dynamics above threshold, a numerical study of the resonator above threshold using a modal expansion approach, and the experimental test of this model. A detailed account of each investigation, including methodology and analysis of the results are also included along with reprints of published and submitted papers.

  17. Lung damage induced by butylated hydroxytoluene in mice. Biochemical, cellular, and morphologic characterization.

    PubMed

    Smith, L J

    1984-11-01

    This study was designed to characterize the biochemical, cellular, and morphologic events produced in mice by butylated hydroxytoluene (BHT) and to relate these events to changes in extracellular angiotensin-converting enzyme (ACE) activity. On Day 1 after the administration of BHT, bronchoalveolar lavage (BAL) ACE activity increased 4-fold (p less than 0.001), its specific activity relative to BAL protein increased 3-fold (p less than 0.001), and both type 1 cell damage and endothelial cell damage were detected by electron microscopy. The early increase in BAL ACE activity preceded changes in plasma ACE levels, BAL cell number, protein, lactate, and lactate dehydrogenase (LDH) activity in both plasma and BAL, and the ACE content of alveolar macrophages. On Day 2, BAL ACE activity increased 9-fold, BAL protein increased 4-fold (p less than 0.001), BAL LDH activity increased 34% (p less than 0.05), and the BAL cell count doubled (p less than 0.01). Changes in each animal's appearance, body weight, wet and dry lung weights, and plasma ACE levels occurred between Days 3 and 5. The BAL differential cell count, which consisted of greater than 95% macrophages in uninjured mice, did not change until Day 5 when there was a small increase in polymorphonuclear leukocytes (PMN). On Day 7, the number of PMN peaked, and some of the other measures of lung injury began returning toward normal. These results indicate that BAL ACE activity is a sensitive, early marker of BHT-induced lung injury, which appears to reflect damage to the cells of the alveolar-capillary barrier. In addition, PMN do not appear to play a major role in this model of lung injury. Because of its effects on angiotensin, bradykinin, and prostaglandins, the early release of ACE from damaged cells may modulate the subsequent injury. PMID:6093659

  18. Characterization of Indentation Response and Stiffness Reduction of Bone using a Continuum Damage Model

    PubMed Central

    Zhang, Jingzhou; Michalenko, Michelle M.; Kuhl, Ellen; Ovaert, Timothy C.

    2009-01-01

    Indentation tests can be used to characterize the mechanical properties of bone at small load/length scales offering the possibility of utilizing very small test specimens, which can be excised using minimally-invasive procedures. In addition, the need for mechanical property data from bone may be a requirement for fundamental multi-scale experiments, changes in nano- and micro-mechanical properties (e.g., as affected by changes in bone mineral density) due to drug therapies, and/or the development of computational models. Load vs. indentation depth data, however, is more complex than those obtained from typical macro-scale experiments, primarily due to the mixed state of stress, and thus interpretation of the data and extraction of mechanical properties is more challenging. Previous studies have shown that cortical bone exhibits a visco-elastic response combined with permanent deformation during indentation tests, and that the load vs. indentation depth response can be simulated using a visco-elastic/plastic material model. The model successfully captures the loading and creep displacement behavior, however, it does not adequately reproduce the unloading response near the end of the unloading cycle, where a pronounced decrease in contact stiffness is observed. It is proposed that the stiffness reduction observed in bone results from an increase in damage; therefore, a plastic-damage model was investigated and shown capable of simulating a typical bone indentation response through an axisymmetric finite element simulation. The plastic-damage model was able to reproduce the full indentation response, especially the reduced stiffness behavior exhibited during the latter stages of unloading. The results suggest that the plastic-damage model is suitable for describing the complex indentation response of bone and may provide further insight into the relationship between model parameters and mechanical/physical properties. PMID:20129418

  19. An optical characterization platform for transparent insulation materials in solar energy

    SciTech Connect

    Platzer, W.J.

    1994-12-31

    The precise optical characterization of transparent insulation materials used in windows, flat-plate collectors or for transparent insulation of buildings, is an important step to design solar collector and daylighting systems with these materials and to estimate energy benefits, peak loads, efficiencies, and different potential risks such as overheating, thermal damage or glare. Physically the aim is clear: Angle-dependent transmittance and reflectance properties for the solar and visible wavelength ranges yield the necessary information for the engineer to enable him to design a good system. However, it is far from trivial to obtain these data with sufficient precision for the rather different materials. The authors have set-up a set of radiation sources and integrating detector spheres which are able to measure directional-hemispherical and hemispherical-hemispherical reflectance and transmittance (hence also absorptance) for the visible and the solar wavelength range. This was possible by applying a PTFE-based coating to the spheres, having a unique spectrally flat response over the whole range, and using non-selective broadband detectors. Careful design tried to optimize integrating sphere geometry. Moreover, spectral measurements between 285--1,100nm are possible with an optical multichannel analyzer utilizing glass fiber optics. The whole experimental set-up will be presented and discussed together with representative results.

  20. Characterization of the optical parameters of high aspect ratio polymer micro-optical components

    NASA Astrophysics Data System (ADS)

    Krajewski, Rafal; Van Erps, Jurgen; Wissmann, Markus; Kujawinska, Malgorzata; Parriaux, Olivier; Tonchev, S.; Mohr, Jurgen; Thienpont, Hugo

    2008-04-01

    Over the last decades the significant grow of interest of photonics devices is observed in various fields of applications. Due to the market demands, the current research studies are focused on the technologies providing miniaturized, reliable low-cost micro-optical systems, particularly the ones featuring the fabrication of high aspect ratio structures. A high potential of these technologies comes from the fact that fabrication process is not limited to single optical components, but entire systems integrating sets of elements could be fabricated. This could in turn result in a significant saving on the assembly and packaging costs. We present a brief overview of the most common high aspect ratio fabrication technologies for micro-optical components followed by some characterization studies of these techniques. The sidewall quality and internal homogeneity will be considered as the most crucial parameters, having an impact on the wavefront propagation in the fabricated components. We show the characterization procedure and measurement results for components prototyped with Deep Proton Writing and glass micromachining technology replicated with Hot Embossing and Elastomeric Mould Vacuum Casting technology. We discuss the pros and cons for using these technologies for the production of miniaturized interferometers blocks. In this paper we present the status of our research on the new technology chain and we show the concept of microinterferometers to be fabricated within presented technology chain.

  1. A micron resolution optical scanner for characterization of silicon detectors.

    PubMed

    Shukla, R A; Dugad, S R; Garde, C S; Gopal, A V; Gupta, S K; Prabhu, S S

    2014-02-01

    The emergence of high position resolution (∼10 μm) silicon detectors in recent times have highlighted the urgent need for the development of new automated optical scanners of micron level resolution suited for characterizing microscopic features of these detectors. More specifically, for the newly developed silicon photo-multipliers (SiPM) that are compact, possessing excellent photon detection efficiency with gain comparable to photo-multiplier tube. In a short time, since their invention the SiPMs are already being widely used in several high-energy physics and astrophysics experiments as the photon readout element. The SiPM is a high quantum efficiency, multi-pixel photon counting detector with fast timing and high gain. The presence of a wide variety of photo sensitive silicon detectors with high spatial resolution requires their performance evaluation to be carried out by photon beams of very compact spot size. We have designed a high resolution optical scanner that provides a monochromatic focused beam on a target plane. The transverse size of the beam was measured by the knife-edge method to be 1.7 μm at 1 - σ level. Since the beam size was an order of magnitude smaller than the typical feature size of silicon detectors, this optical scanner can be used for selective excitation of these detectors. The design and operational details of the optical scanner, high precision programmed movement of target plane (0.1 μm) integrated with general purpose data acquisition system developed for recording static and transient response photo sensitive silicon detector are reported in this paper. Entire functionality of scanner is validated by using it for selective excitation of individual pixels in a SiPM and identifying response of active and dead regions within SiPM. Results from these studies are presented in this paper. PMID:24593348

  2. A micron resolution optical scanner for characterization of silicon detectors

    SciTech Connect

    Shukla, R. A.; Dugad, S. R. Gopal, A. V.; Gupta, S. K.; Prabhu, S. S.; Garde, C. S.

    2014-02-15

    The emergence of high position resolution (∼10 μm) silicon detectors in recent times have highlighted the urgent need for the development of new automated optical scanners of micron level resolution suited for characterizing microscopic features of these detectors. More specifically, for the newly developed silicon photo-multipliers (SiPM) that are compact, possessing excellent photon detection efficiency with gain comparable to photo-multiplier tube. In a short time, since their invention the SiPMs are already being widely used in several high-energy physics and astrophysics experiments as the photon readout element. The SiPM is a high quantum efficiency, multi-pixel photon counting detector with fast timing and high gain. The presence of a wide variety of photo sensitive silicon detectors with high spatial resolution requires their performance evaluation to be carried out by photon beams of very compact spot size. We have designed a high resolution optical scanner that provides a monochromatic focused beam on a target plane. The transverse size of the beam was measured by the knife-edge method to be 1.7 μm at 1 − σ level. Since the beam size was an order of magnitude smaller than the typical feature size of silicon detectors, this optical scanner can be used for selective excitation of these detectors. The design and operational details of the optical scanner, high precision programmed movement of target plane (0.1 μm) integrated with general purpose data acquisition system developed for recording static and transient response photo sensitive silicon detector are reported in this paper. Entire functionality of scanner is validated by using it for selective excitation of individual pixels in a SiPM and identifying response of active and dead regions within SiPM. Results from these studies are presented in this paper.

  3. Characterization of energetic formulations optimized for optical initiation

    SciTech Connect

    Zucker, Jonathan M; Tappan, Bryce C; Oschwald, David M; Preston, Daniel N; Burnside, Nathan

    2010-01-01

    . By characterizing the energy required to initiate several different materials, more effective formulations can be designed using the better performing materials. Presented here are the results of laser initiation tests on a variety of compositions, principally combinations of PETN, DAATO{sub 3.5}, HMX, Ag{sub 2}BTA (silver bistetrazolamine), CuBTA, BNCP (bis-5-nitrotetrazolato tetraamine cobalt perchloriate), nm Ag, and a variety of MICs (metastable intermolecular compounds). Also presented are the conclusions as to which formulations are most suitable for optically initiated systems.

  4. Optical properties and radiation damages of cerium fluoride crystals doped with alkali-earth and rare-earth elements

    SciTech Connect

    Gusev, Y.I.; Melchakov, E.N.; Mironov, I.A.; Panteleev, L.A.; Reiterov, V.M.; Rodnyi, P.A.; Seliverstov, D.M.; Shchetkowsky, A.I.; Yazikov, D.M.; Zakharov, N.G.

    1994-12-31

    The most essential contribution in the investigation of CeF{sub 3} crystals having the goal to construct high precision electromagnetic calorimeters has been done by Crystal Clear Collaboration. Study of optical properties and radiation damages of Cerium Fluoride crystals doped with Ca, Ba, Sr, La, Nd, Zr and Hf in the wide range of concentrations has been performed with the goal to obtain high optical transparency of crystals at different cumulative doses under {gamma}-irradiation. Time decay curves and relative light yields of scintillators as a function of doping level were measured using X-ray excitation of samples and single photon counting method.

  5. Synthesis, crystal growth and characterization of nonlinear optical organic crystal: p-Toluidinium p-toluenesulphonate

    SciTech Connect

    Vijayakumar, P.; Anandha Babu, G.; Ramasamy, P.

    2012-04-15

    Graphical abstract: p-Toluidinium p-toluenesulphonate (p-TTS) an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that p-TTS crystallizes in monoclinic crystal system. p-TTS single crystal belongs to negative birefringence crystal. Second harmonic conversion efficiency of p-TTS has been found to be 1.3 times higher than that of KDP. Multiple shot surface laser damage threshold is determined to be 0.30 GW/cm{sup 2} at 1064 nm laser radiation. Highlights: Black-Right-Pointing-Pointer It deals with the synthesis, growth and characterization of p-TTS an organic NLO crystal. Black-Right-Pointing-Pointer Wide optical transparency window between 280 nm and 1100 nm. Black-Right-Pointing-Pointer Negative birefringence crystal and dispersion of birefringence is negligibly small. Black-Right-Pointing-Pointer Thermal study reveals that the grown crystal is stable up to 210 Degree-Sign C. Black-Right-Pointing-Pointer Multiple shot surface laser damage threshold is 0.30 GW/cm{sup 2} at 1064 nm laser radiation. -- Abstract: p-Toluidinium p-toluenesulphonate (p-TTS) an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that p-TTS crystallizes in monoclinic crystal system. The structural perfection of the grown p-TTS single crystal has been analyzed by high-resolution X-ray diffraction rocking curve measurements. Fourier transform infrared spectral studies have been performed to identify the functional groups. The optical transmittance window and the lower cutoff wavelength of the grown crystals have been identified by UV-vis-IR studies. Birefringence of p-TTS crystal has been studied using channel spectrum measurement. The laser damage threshold value was measured using Nd:YAG laser. The second harmonic conversion efficiency of p-TTS has

  6. Optical characterization of vitreous structure in health and disease

    NASA Astrophysics Data System (ADS)

    Sampathkumar, Ashwin; Khoshnevis, Matin; Ketterling, Jeffrey A.; Sebag, J.

    2015-03-01

    Patients with myopic vitreopathy (MV) and posterior vitreous detachment (PVD) see floaters, which often can degrade contrast sensitivity to a significant extent. The floaters are associated with irregularly shaped vitreous opacities. In contrast, asteroid hyalosis (AH), which is characterized by microscopic, spherical, white asteroid bodies (ABs) that move with vitreous displacement during eye movements, does not interfere significantly with vision. We hypothesize that the irregular surface of vitreous opacities associated with MV distinguish MV from AH and its smooth-surfaced ABs. A finite-element model was developed to characterize the light-scattering field of vitreous opacities in MV and AH. Vitreous opacities were modeled as spherical bodies and illuminated by a plane wave of light in the optical wavelength of 400-1000 nm. The model has provisions to add random perturbations to the spherical surfaces to vary light-scattering properties and mimic disturbances in vision from simple diffraction rings to more-complex patterns. Samples of ex vivo porcine vitreous (0.4-0.5 ml) were placed in a custom spectrophotometer and the static, light-scattering field of the sample was measured in the spectral range of 400-1000 nm with a resolution of 0.3 nm. Model solutions mimicking healthy vitreous and AH were experimentally validated using a laboratory optical apparatus. Model-based estimates of scattering cross-sections of calibrated gold nanoparticles were found to be in good agreement with experimental measurements. Simulation results potentially can complement experimental data to quantitatively characterize vitreous opacities and distinguish between structures that significantly impact vision, such as those due to myopic vitreopathy and aging, from those that have little impact, like ABs. Such techniques to determine the structural significance of vitreous opacification would be very useful in selecting patients for surgery as well as evaluating the efficacy of

  7. Characterization of damage mechanisms associated with reference point indentation in human bone.

    PubMed

    Beutel, Bryan G; Kennedy, Oran D

    2015-06-01

    Measurement of bone mineral density (BMD) is the clinical gold standard in cases of compromised skeletal integrity, such as with osteoporosis. While BMD is a useful measurement to index skeletal health, it is also limited since it cannot directly assess any mechanical properties. The ability to directly assess mechanical properties of bone tissue would be clinically important. Reference point indentation (RPI) is a technology that has been designed to try and achieve this goal. While RPI has been shown to detect altered bone tissue properties, the underlying physical mechanism of these measurements has not been characterized. Thus, we designed a study whereby the contribution of (1) test cycle number and (2) test load level to RPI test-induced sub-surface damage was characterized and quantified. Standardized specimens were prepared from cadaveric human tibiae (n=6), such that 12 replicates of each testing condition could be carried out. A custom rig was fabricated to accurately position and map indentation sites. One set of tests was carried out with 1, 5, 10, 15 and 20 cycles (Max Load: 8 N, Freq: 2 Hz), and a second set of tests was carried out with Load levels of 2, 4, 6, 8 or 10 N (Cycle number: 20, Freq: 2 Hz). The RPI parameter Loading Slope (LS) was cycle dependent at 5, 10, 15 and 20 cycles (p<0.05). First Cycle Indentation Distance (ID 1st), Total Indentation Distance (TID), Mean Energy Dissipation (ED), First Cycle Unloading Slope (US 1st), Mean Unloading Slope (US) and LS were significantly different at 6, 8 and 10 N compared to 2 N (p<0.05). From the histomorphometric measurements, damage zone span was significantly different after 5, 10, 15 and 20 cycles compared with 1 cycle while indent profile width and indent profile depth were significantly different at 10, 15 and 20 cycles (p<0.05). With the load varying protocol, each of these parameters differed significantly at each increased load level (4, 6, 8, 10 N) compared with the basal level of 2 N (p<0

  8. Increase in the optical damage threshold of a ZnSe-passivated front mirror of a laser diode

    SciTech Connect

    Davydova, Evgeniya I; Dmitriev, V V; Kozlov, Yu Yu; Kukushkin, I A; Uspenskiy, Mikhail B; Shishkin, Viktor A

    2011-05-31

    The operation of single-mode diode lasers with a front mirror passivated by ZnSe films of different thicknesses is studied in the pulsed regime (pulse duration {tau} = 0.2 - 10 {mu}s). It is found that in the case of short (0.2 {mu}s) pulses, the catastrophic optical damage threshold grows almost linearly as the film thickness on the front mirror increases from 0.1 to 0.5 {mu}m. It is shown that lasers with mirrors passivated by 'thick' (0.4 - 0.6 {mu}m) ZnSe films can operate stably in the case of 'long' (2 - 10 {mu}s) pulses. It is assumed that in this pulsed regime the ZnSe film provides an additional heat removal from the hot zone of the front mirror, and consequently increases the optical damage threshold. (lasers)

  9. Long-pulse laser-induced damage in an optical anti-reflective film: II. Experimental research

    NASA Astrophysics Data System (ADS)

    Li, Changli; Ma, Yao; Wang, Di; Wang, Zhiyang; Zhang, Xihe; Liu, Haiming

    2014-12-01

    In order to verify the result of theoretical analysis about long-pulse flat-topped multi-Gaussian laser-induced damage in an optical anti-reflection film with HfO2/SiO2 composite film coating on a BK7 substrate (BK7:HfO2/SiO2), an experimental system was built, which carried out the experiment and analysis, focusing on the pulse-length 1.0 ms, flat-topped laser-induced damage. The result shows that the thermal effect is the main reason for damage under the long-pulse flat-topped laser. Moreover, the stripping and shedding occur because of the heating stress of the film happening at an early stage of the laser irradiation. However, the crack happens at laser irradiation termination. The correctness of the theoretical analysis results is verified.

  10. Fluence Thresholds for Laser-Induced Damage of Optical Components in the Injector Laser of the SSRL Gun Test Facility

    SciTech Connect

    Boton, P

    2005-01-31

    Damage threshold fluences for several optical components were measured at three wavelengths using the injector laser at SSRL's Gun Test Facility. Measurements were conducted using the fundamental ir wavelength at 1053 nanometers and harmonics at 526 nm and 263 nm with 3.4ps pulses (1/e{sup 2} full width intensity); ir measurements were also conducted with 850 ps pulses. Practical surfaces relevant to the laser system performance are emphasized. Damage onset was evidenced by an alteration of the specular reflection of a cw probe laser (650 nm) from the irradiated region of the target surface. For the case of stretched ir pulses, damage to a Nd:glass rod was observed to begin at a site within the bulk material and to progress back toward the incident surface.

  11. Development of 66kV XLPE submarine cable using optical fiber as a mechanical-damage-detection-sensor

    SciTech Connect

    Nishimoto, Toshio; Miyahara, Tsutomu; Takehana, Hajime; Tateno, Fuminori

    1995-10-01

    Submarine cables are exposed to great risk of serious mechanical damage by ship anchors or equipment used for fishing. Detection of such damage in a submarine cable is a very useful technology for improving the reliability of a submarine cable transmission line. A mechanical-damage-detection-sensor using optical fiber was developed. A prototype 66kV XLPE submarine cable incorporating the sensor was manufactured for trial, and the ability of a sensor was confirmed by compression test. Actual 66kV XLPE submarine cable incorporating the sensor was manufactured for trial, and the ability of a sensor was confirmed by compression test. Actual 66kV XLPE submarine cable with the sensor was manufactured and installed as an operating transmission line in Japan.

  12. Structural integrity and damage assessment of high performance arresting cable systems using an embedded distributed fiber optic sensor (EDIFOS) system

    NASA Astrophysics Data System (ADS)

    Mendoza, Edgar A.; Kempen, Cornelia; Sun, Sunjian; Esterkin, Yan; Prohaska, John; Bentley, Doug; Glasgow, Andy; Campbell, Richard

    2010-04-01

    Redondo Optics in collaboration with the Cortland Cable Company, TMT Laboratories, and Applied Fiber under a US Navy SBIR project is developing an embedded distributed fiber optic sensor (EDIFOSTM) system for the real-time, structural health monitoring, damage assessment, and lifetime prediction of next generation synthetic material arresting gear cables. The EDIFOSTM system represents a new, highly robust and reliable, technology that can be use for the structural damage assessment of critical cable infrastructures. The Navy is currently investigating the use of new, all-synthetic- material arresting cables. The arresting cable is one of the most stressed components in the entire arresting gear landing system. Synthetic rope materials offer higher performance in terms of the strength-to-weight characteristics, which improves the arresting gear engine's performance resulting in reduced wind-over-deck requirements, higher aircraft bring-back-weight capability, simplified operation, maintenance, supportability, and reduced life cycle costs. While employing synthetic cables offers many advantages for the Navy's future needs, the unknown failure modes of these cables remains a high technical risk. For these reasons, Redondo Optics is investigating the use of embedded fiber optic sensors within the synthetic arresting cables to provide real-time structural assessment of the cable state, and to inform the operator when a particular cable has suffered impact damage, is near failure, or is approaching the limit of its service lifetime. To date, ROI and its collaborators have developed a technique for embedding multiple sensor fibers within the strands of high performance synthetic material cables and use the embedded fiber sensors to monitor the structural integrity of the cable structures during tensile and compressive loads exceeding over 175,000-lbsf without any damage to the cable structure or the embedded fiber sensors.

  13. Physical property characterization of a damage zone in granitic rock - Implications for geothermal reservoir properties

    NASA Astrophysics Data System (ADS)

    Wenning, Quinn; Madonna, Claudio; Amann, Florian; Gischig, Valentin; Burg, Jean-Pierre

    2016-04-01

    Geothermal energy offers a viable alternative to mitigate greenhouse gas emitting energy production. A tradeoff between less expensive drilling costs and increased permeability at shallow depths versus increased heat production at deeper depths stipulates the economic energy potential of a given reservoir. From a geological perspective, successful retrieval of geothermal energy from the subsurface requires sufficient knowledge of the structural and stratigraphic relationship of the target formations, which govern the thermal conditions, physical properties, and fluid flow properties of reservoir rocks. In Switzerland, deep basement rocks (~5 km) with fluid conducting damage zones and enhanced fractured systems stimulated by hydraulic shearing are seen as a potential geothermal reservoir system. Damage zones, both natural and induced, provide permeability enhancement that is especially important for creating fluid conductivity where the matrix permeability is low. This study concentrates on characterizing the elastic and transport properties entering into a natural damage zone penetrated by a borehole at the Grimsel underground research laboratory. The borehole drilled from a cavern at 480 m below ground surface penetrates approximately 20 m of mostly intact Grimsel granodiorite before entering the first phyllosilicate-rich shear zone (~0.2 m thick). The borehole intersects a second shear zone at approximately 23.8m. Between the two shear zones the Grimsel granodiorite is heavily fractured. The minimum principle stress magnitude from in-situ measurements decreases along the borehole into the first shear zone. Two mutually perpendicular core samples of Grimsel granodiorite were taken every 0.1 m from 19.5 to 20.1 m to characterize the physical properties and anisotropy changes as a gradient away from the damage zone. Measurements of ultrasonic compressional (Vp) and shear (Vs) velocities at 1 MHz frequency are conducted at room temperature and hydrostatic pressures

  14. Characterization of impact damage in metallic/nonmetallic composites using x-ray computed tomography imaging

    SciTech Connect

    Green, William H.; Wells, Joseph M.

    1999-12-02

    Characterizing internal impact damage in composites can be difficult, especially in structurally complex composites or those consisting of many materials. Many methods for nondestructive inspection/nondestructive testing (NDI/NDT) of materials have been known and in use for many years, including x-ray film, real-time, and digital radiographic techniques, and ultrasonic techniques. However, these techniques are generally not capable of three-dimensional (3D) mapping of complex damage patterns, which is necessary to visualize and understand damage cracking modes. Conventional x-ray radiography suffers from the loss of 3D information. Structural complexity and signal dispersion in materials with many interfaces significantly effect ultrasonic inspection techniques. This makes inspection scan interpretation difficult, especially in composites containing a number of different materials (i.e., polymer, ceramic, and metallic). X-ray computed tomography (CT) is broadly applicable to any material or test object through which a beam of penetrating radiation may be passed and detected, including metals, plastics, ceramics, metallic/nonmetallic composites, and assemblies. The principal advantage of CT is that it provides densitometric (that is, radiological density and geometry) images of thin cross sections through an object. Because of the absence of structural superposition, images are much easier to interpret than conventional radiological images. The user can quickly learn to read CT data because images correspond more closely to the way the human mind visualizes 3D structures than projection radiology (that is, film radiography, real-time radiography (RTR), and digital radiography (DR)). Any number of CT images, or slices, from scanning an object can be volumetrically reconstructed to produce a 3D attenuation map of the object. The 3D attenuation data can be rendered using multiplanar or 3D solid visualization. In multiplanar visualization there are four planes of view

  15. Characterization of impact damage in metallic/nonmetallic composites using x-ray computed tomography imaging

    NASA Astrophysics Data System (ADS)

    Green, William H.; Wells, Joseph M.

    1999-12-01

    Characterizing internal impact damage in composites can be difficult, especially in structurally complex composites or those consisting of many materials. Many methods for nondestructive inspection/nondestructive testing (NDI/NDT) of materials have been known and in use for many years, including x-ray film, real-time, and digital radiographic techniques, and ultrasonic techniques. However, these techniques are generally not capable of three-dimensional (3D) mapping of complex damage patterns, which is necessary to visualize and understand damage cracking modes. Conventional x-ray radiography suffers from the loss of 3D information. Structural complexity and signal dispersion in materials with many interfaces significantly effect ultrasonic inspection techniques. This makes inspection scan interpretation difficult, especially in composites containing a number of different materials (i.e., polymer, ceramic, and metallic). X-ray computed tomography (CT) is broadly applicable to any material or test object through which a beam of penetrating radiation may be passed and detected, including metals, plastics, ceramics, metallic/nonmetallic composites, and assemblies. The principal advantage of CT is that it provides densitometric (that is, radiological density and geometry) images of thin cross sections through an object. Because of the absence of structural superposition, images are much easier to interpret than conventional radiological images. The user can quickly learn to read CT data because images correspond more closely to the way the human mind visualizes 3D structures than projection radiology (that is, film radiography, real-time radiography (RTR), and digital radiography (DR)). Any number of CT images, or slices, from scanning an object can be volumetrically reconstructed to produce a 3D attenuation map of the object. The 3D attenuation data can be rendered using multiplanar or 3D solid visualization. In multiplanar visualization there are four planes of view

  16. Analysis of the light-field intensity dependence of catastrophic optical damage in high-power AlGaInP lasers using an asymmetrical tapered laser

    NASA Astrophysics Data System (ADS)

    Bou Sanayeh, Marwan

    2016-04-01

    Catastrophic optical damage (COD) in semiconductor lasers is a major limiting effect for high-power operation. Several techniques like microphotoluminescence (μPL) mapping, focused ion beam (FIB) microscopy, and micro- Raman spectroscopy were employed to reveal the physics behind catastrophic optical damage, its related temperature dynamics, as well as associated defect and near-field patterns. High-resolution μPL images demonstrated that during COD, nonradiative dark line defects (DLDs) originate from the front mirror of the laser and propagate deep inside the cavity. Furthermore, FIB microscopy identified the epitaxial layers affected by COD, revealing that the DLDs are confined to the active region. In addition, deep-etching uncovered the DLDs by making them visible, and showed that they are composed of complex dislocation networks. Lasers that underwent a spontaneous breakdown where also studied. One missing piece to complete the characterization of COD is to analyze if the DLDs actually follow certain crystal direction lines inside the laser cavity, which are in general perpendicular to the output facet, or follow the path of the light-field intensity-maximum. Using a specially designed innovative device, namely an asymmetrical AlGaInP tapered laser, it is proven in this study that the COD is strongly dependent on the light-field intensity inside the laser cavity and not on certain crystal direction lines.

  17. Advanced Mitigation Process (AMP) for Improving Laser Damage Threshold of Fused Silica Optics.

    PubMed

    Ye, Xin; Huang, Jin; Liu, Hongjie; Geng, Feng; Sun, Laixi; Jiang, Xiaodong; Wu, Weidong; Qiao, Liang; Zu, Xiaotao; Zheng, Wanguo

    2016-01-01

    The laser damage precursors in subsurface of fused silica (e.g. photosensitive impurities, scratches and redeposited silica compounds) were mitigated by mineral acid leaching and HF etching with multi-frequency ultrasonic agitation, respectively. The comparison of scratches morphology after static etching and high-frequency ultrasonic agitation etching was devoted in our case. And comparison of laser induce damage resistance of scratched and non-scratched fused silica surfaces after HF etching with high-frequency ultrasonic agitation were also investigated in this study. The global laser induce damage resistance was increased significantly after the laser damage precursors were mitigated in this case. The redeposition of reaction produce was avoided by involving multi-frequency ultrasonic and chemical leaching process. These methods made the increase of laser damage threshold more stable. In addition, there is no scratch related damage initiations found on the samples which were treated by Advanced Mitigation Process. PMID:27484188

  18. Advanced Mitigation Process (AMP) for Improving Laser Damage Threshold of Fused Silica Optics

    PubMed Central

    Ye, Xin; Huang, Jin; Liu, Hongjie; Geng, Feng; Sun, Laixi; Jiang, Xiaodong; Wu, Weidong; Qiao, Liang; Zu, Xiaotao; Zheng, Wanguo

    2016-01-01

    The laser damage precursors in subsurface of fused silica (e.g. photosensitive impurities, scratches and redeposited silica compounds) were mitigated by mineral acid leaching and HF etching with multi-frequency ultrasonic agitation, respectively. The comparison of scratches morphology after static etching and high-frequency ultrasonic agitation etching was devoted in our case. And comparison of laser induce damage resistance of scratched and non-scratched fused silica surfaces after HF etching with high-frequency ultrasonic agitation were also investigated in this study. The global laser induce damage resistance was increased significantly after the laser damage precursors were mitigated in this case. The redeposition of reaction produce was avoided by involving multi-frequency ultrasonic and chemical leaching process. These methods made the increase of laser damage threshold more stable. In addition, there is no scratch related damage initiations found on the samples which were treated by Advanced Mitigation Process. PMID:27484188

  19. Advanced Mitigation Process (AMP) for Improving Laser Damage Threshold of Fused Silica Optics

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Huang, Jin; Liu, Hongjie; Geng, Feng; Sun, Laixi; Jiang, Xiaodong; Wu, Weidong; Qiao, Liang; Zu, Xiaotao; Zheng, Wanguo

    2016-08-01

    The laser damage precursors in subsurface of fused silica (e.g. photosensitive impurities, scratches and redeposited silica compounds) were mitigated by mineral acid leaching and HF etching with multi-frequency ultrasonic agitation, respectively. The comparison of scratches morphology after static etching and high-frequency ultrasonic agitation etching was devoted in our case. And comparison of laser induce damage resistance of scratched and non-scratched fused silica surfaces after HF etching with high-frequency ultrasonic agitation were also investigated in this study. The global laser induce damage resistance was increased significantly after the laser damage precursors were mitigated in this case. The redeposition of reaction produce was avoided by involving multi-frequency ultrasonic and chemical leaching process. These methods made the increase of laser damage threshold more stable. In addition, there is no scratch related damage initiations found on the samples which were treated by Advanced Mitigation Process.

  20. The effect of lattice temperature on surface damage in fused silica optics

    SciTech Connect

    Bude, J; Guss, G; Matthews, M; Spaeth, M L

    2007-10-31

    We examine the effect of lattice temperature on the probability of surface damage initiation for 355nm, 7ns laser pulses for surface temperatures below the melting point to temperatures well above the melting point of fused silica. At sufficiently high surface temperatures, damage thresholds are dramatically reduced. Our results indicate a temperature activated absorption and support the idea of a lattice temperature threshold of surface damage. From these measurements, we estimate the temperature dependent absorption coefficient for intrinsic silica.

  1. Optical characterization of CMOS compatible micro optics fabricated by mask-based and mask-less hybrid lithography

    NASA Astrophysics Data System (ADS)

    Wang, Sunglin; Summitt, Chris; Johnson, Lee; Zaverton, Melissa; Milster, Tom; Takashima, Yuzuru

    2014-09-01

    We report a CMOS compatible fabrication and optical characterization of the micrometer scale optical coupler, a 45° mirror-based optical coupler for inter-layer optical coupling. A newly proposed mask-based and mask-less hybrid lithography process enables accurate surface profile of the micrometer sized 45° mirror by using a CMOS compatible buffer coat material. Surface profile inspected by an optical interferometry agrees well with SEM based inspection results. Experimental and theoretical results for routing and coupling of laser beam in 90° will be discussed.

  2. Characterization of eosinophilic esophagitis murine models using optical coherence tomography

    PubMed Central

    Alex, Aneesh; Noti, Mario; Wojno, Elia D. Tait; Artis, David; Zhou, Chao

    2014-01-01

    Pre-clinical studies using murine models are critical for understanding the pathophysiological mechanisms underlying immune-mediated disorders such as Eosinophilic esophagitis (EoE). In this study, an optical coherence tomography (OCT) system capable of providing three-dimensional images with axial and transverse resolutions of 5 µm and 10 µm, respectively, was utilized to obtain esophageal images from a murine model of EoE-like disease ex vivo. Structural changes in the esophagus of wild-type (Tslpr+/+) and mutant (Tslpr−/−) mice with EoE-like disease were quantitatively evaluated and food impaction sites in the esophagus of diseased mice were monitored using OCT. Here, the capability of OCT as a label-free imaging tool devoid of tissue-processing artifacts to effectively characterize murine EoE-like disease models has been demonstrated. PMID:24575353

  3. Characterization of Talbot pattern illumination for scanning optical microscopy

    NASA Astrophysics Data System (ADS)

    Liu, Guangshuo; Yang, Changhuei; Wu, Jigang

    2013-09-01

    We studied the use of Talbot pattern illumination in scanning optical microscopy (SOM). Unlike conventional illumination spots used in SOM, the focal spots in Talbot pattern are more complicated and do not have a simple Gaussian intensity distribution. To find out the resolution of SOM using Talbot pattern, we characterized the evolution of the full-width-at-half-maximum spot size of the Talbot focal spots by computer simulation. We then simulated the SOM imaging under Talbot pattern illumination using the razor blade and the U.S. Air Force target as the sample objects, and compared the results with those performed with Gaussian spots as illumination. Using several foci searching algorithms, the optimal focal distances were found to be shorter than the theoretical Talbot distances. The simulation results were consistent with the experiment results published previously. We then provide a practical guidance for searching for optimal focal distances in the SOM based on these studies.

  4. Characterization of Fibre Channel over Highly Turbulent Optical Wireless Links

    SciTech Connect

    Johnson, G W; Henderer, B D; Wilburn, J W; Ruggiero, A J

    2003-07-28

    We report on the performance characterization and issues associated with using Fibre Channel (FC) over a highly turbulent free-space optical (FSO) link. Fibre Channel is a storage area network standard that provides high throughput with low overhead. Extending FC to FSO links would simplify data transfer from existing high-bandwidth sensors such as synthetic aperture radars and hyperspectral imagers. We measured the behavior of FC protocol at 1 Gbps in the presence of synthetic link dropouts that are typical of turbulent FSO links. Results show that an average bit error rate of less than 2 x 10{sup -8} is mandatory for adequate throughput. More importantly, 10 ns dropouts at a 2 Hz rate were sufficient to cause long (25 s) timeouts in the data transfer. Although no data was lost, this behavior is likely to be objectionable for most applications. Prospects for improvements in hardware and software will be discussed.

  5. Non-Intrusive Optical Diagnostic Methods for Flowfield Characterization

    NASA Technical Reports Server (NTRS)

    Tabibi, Bagher M.; Terrell, Charles A.; Spraggins, Darrell; Lee, Ja. H.; Weinstein, Leonard M.

    1997-01-01

    Non-intrusive optical diagnostic techniques such as Electron Beam Fluorescence (EBF), Laser-Induced Fluorescence (LIF), and Focusing Schlieren (FS) have been setup for high-speed flow characterization and large flowfield visualization, respectively. Fluorescence emission from the First Negative band of N2(+) with the (0,0) vibration transition (at lambda =391.44 nm) was obtained using the EBF technique and a quenching rate of N2(+)* molecules by argon gas was reported. A very high sensitivity FS system was built and applied in the High-Speed Flow Generator (HFG) at NASA LaRC. A LIF system is available at the Advanced Propulsion Laboratory (APL) on campus and a plume exhaust velocity measurement, measuring the Doppler shift from lambda = 728.7 nm of argon gas, is under way.

  6. Synthesis, characterization and optical properties of zinc oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, Surabhi Siva; Venkateswarlu, Putcha; Rao, Vanka Ranga; Rao, Gollapalli Nagewsara

    2013-05-01

    Zinc oxide nanoparticles were synthesized using a simple precipitation method with zinc sulfate and sodium hydroxide as starting materials. The synthesized sample was calcined at different temperatures for 2 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and proton-induced X-ray emission (PIXE) analysis. SEM images show various morphological changes of ZnO obtained by the above method. The average crystallite sizes of the samples were calculated from the full width at half maximum of XRD peaks by using Debye-Scherrer's formula and were found to be in the nanorange. EDS shows that the above route produced highly pure ZnO nanostructures. PIXE technique was used for trace elemental analysis of ZnO. The optical band gaps of various ZnO powders were calculated from UV-visible diffuse reflectance spectroscopic studies.

  7. Fabrication, characterization, and optical properties of gold nanobowl submonolayer structures.

    PubMed

    Ye, Jian; Van Dorpe, Pol; Van Roy, Willem; Borghs, Gustaaf; Maes, Guido

    2009-02-01

    We report on a versatile method to fabricate hollow gold nanobowls and complex gold nanobowls (with a core) based on an ion milling and a vapor HF etching technique. Two different sized hollow gold nanobowls are fabricated by milling and etching submonolayers of gold nanoshells deposited on a substrate, and their sizes and morphologies are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties of hollow gold nanobowls with different sizes are investigated experimentally and theoretically, showing highly tunable plasmon resonance ranging from the visible to the near-infrared region. Additionally, finite difference time domain (FDTD) calculations show an enhanced localized electromagnetic field around hollow gold nanobowl structures, which indicates a potential application in surface-enhanced Raman scattering (SERS) spectroscopy for biomolecular detection. Finally, we demonstrate the fabrication of complex gold nanobowls with a gold nanoparticle core which offers the capability to create plasmon hybridized nanostructures. PMID:19125593

  8. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    SciTech Connect

    Manigandan, R.; Suresh, R.; Giribabu, K.; Narayanan, V.; Vijayalakshmi, L.; Stephen, A.

    2014-01-28

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  9. Techniques for nonlinear optical characterization of materials: a review

    NASA Astrophysics Data System (ADS)

    de Araújo, Cid B.; Gomes, Anderson S. L.; Boudebs, Georges

    2016-03-01

    Various techniques to characterize the nonlinear (NL) optical response of centro-symmetric materials are presented and evaluated with emphasis on the relationship between the macroscopic measurable quantities and the microscopic properties of photonic materials. NL refraction and NL absorption of the materials are the phenomena of major interest. The dependence of the NL refraction and NL absorption coefficients on the nature of the materials was studied as well as on the laser excitation characteristics of wavelength, intensity, spatial profile, pulse duration and pulses repetition rate. Selected experimental results are discussed and illustrated. The various techniques currently available were compared and their relative advantages and drawbacks were evaluated. Critical comparisons among established techniques provided elements to evaluate their accuracies and sensitivities with respect to novel methods that present improvements with respect to the conventional techniques.

  10. Applying hafnia mixtures to enhance the laser-induced damage threshold of coatings for third-harmonic generation optics

    NASA Astrophysics Data System (ADS)

    Mende, Mathias; Jensen, Lars O.; Ehlers, Henrik; Bruns, Stefan; Vergöhl, Michael; Burdack, Peer; Ristau, Detlev

    2012-11-01

    The generation of third harmonic radiation (THG) is required for many pulsed solid-state laser applications in industry and science. In this contribution, the coatings for two necessary optical components, dichroic mirrors and nonlinear optical (NLO) crystals are in the focus of investigation. Because of the high bulk damage threshold lithium triborate (LBO) crystals are applied for this study. HfO2/SiO2 mixtures are employed as high refractive index material to improve the power handling capability of the multilayers. All coatings are produced by ion beam sputtering (IBS) using a zone target assembly for the deposition of material mixtures. The atomic composition and the oxidation ratio of different HfO2/SiO2 mixtures are analyzed by X-ray photoelectron spectroscopy (XPS). The influence of different deposition temperatures and post annealing on the optical properties and the amorphous micro structure of the films is investigated by UV/Vis/NIR spectroscopy and X-ray diffraction (XRD). The laser induced damage thresholds at 355 nm wavelength for nanosecond pulse durations are measured in a 10,000on1 experiment according with the standard ISO21254. Furthermore, the optical components are tested under real application conditions.

  11. Tomographic characterization of a linear optical quantum Toffoli gate

    NASA Astrophysics Data System (ADS)

    Mičuda, M.; Miková, M.; Straka, I.; Sedlák, M.; Dušek, M.; Ježek, M.; Fiurášek, J.

    2015-09-01

    We report on a detailed characterization of a three-qubit linear optical quantum Toffoli gate. Our experiment utilizes correlated photon pairs generated in the process of spontaneous parametric down-conversion. Two qubits are encoded into polarization and spatial degrees of freedom of a signal photon, and the third qubit is represented by polarization of an idler photon. The linear optical Toffoli gate is implemented by interference of photons on a partially polarizing beam splitter inserted inside a Mach Zehnder interferometer formed by two calcite beam displacers. We have measured 4032 different two-photon coincidences, which allows us to estimate the fidelity of the gate to be 90%. Although these data are not tomographically complete, we show that they are sufficient for a reliable reconstruction of the quantum process matrix of the gate via the recently proposed maximum likelihood-maximum entropy estimation procedure. To probe the entangling capability of the gate, we have investigated generation of three-qubit GHZ states from fully and partially separable input states and we have performed a full tomography of the output states. We compare the reconstructed states with theoretical predictions obtained with the use of the estimated quantum process matrix and obtain a very good agreement.

  12. Optical characterization and measurements of autostereoscopic 3D displays

    NASA Astrophysics Data System (ADS)

    Salmimaa, Marja; Järvenpää, Toni

    2008-04-01

    3D or autostereoscopic display technologies offer attractive solutions for enriching the multimedia experience. However, both characterization and comparison of 3D displays have been challenging when the definitions for the consistent measurement methods have been lacking and displays with similar specifications may appear quite different. Earlier we have investigated how the optical properties of autostereoscopic (3D) displays can be objectively measured and what are the main characteristics defining the perceived image quality. In this paper the discussion is extended to cover the viewing freedom (VF) and the definition for the optimum viewing distance (OVD) is elaborated. VF is the volume inside which the eyes have to be to see an acceptable 3D image. Characteristics limiting the VF space are proposed to be 3D crosstalk, luminance difference and color difference. Since the 3D crosstalk can be presumed to be dominating the quality of the end user experience and in our approach is forming the basis for the calculations of the other optical parameters, the reliability of the 3D crosstalk measurements is investigated. Furthermore the effect on the derived VF definition is evaluated. We have performed comparison 3D crosstalk measurements with different measurement device apertures and the effect of different measurement geometry on the results on actual 3D displays is reported.

  13. Optical characterization of contaminant film. [long duration exposure facility

    NASA Technical Reports Server (NTRS)

    Blakkolb, Brian K.; Yaung, James Y.; Kosic, Tom; Bowen, Howard

    1992-01-01

    The so called 'nicotine stain' documented at many locations on the Long Duration Exposure Facility is still unexplained as to the exact origin and mechanism of deposition, although enough is known to have some understanding of the conditions coincident for the formation of the deposits. Direct and scattered atomic oxygen flux, and solar ultraviolet radiation interacting with materials outgassing products have all been implicated in the formation of the dark brown contamination deposits. The nicotine stain represents a potential of performance degradation for spacecraft designed for long term operation in low Earth orbit and therefore, a need exists to characterize this form of spacecraft self contamination and quantify the impact on thermal/optical systems. Optical property measurements in the spectral range of 2 to 10 microns were performed on specimens of the contaminated film. Reflectance measurements of the contaminant film as deposited on the surface and as free standing films are presented along with transmission spectra for the bulk material. Thickness measurements along with micrographic examination of the cross section of the deposit reveal the layered structure of the deposit which further implicates solar illumination as a factor in the deposition mechanism.

  14. Optical Characterization of Bulk ZnSeTe Solid Solutions

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, S.; Zhu, Shen; Lehoczky, S. L.; Wang, Ling Jun

    2000-01-01

    Optical characterization was performed on wafers sliced from crystals of ZnSe, ZnTe, and ZnSe(1-x)Te(x)(0 less than x less than 0.4) grown by physical vapor transport. Energy band gaps at room temperature were determined from optical transmission measurements on 11 wafers. A best fit curve to the band gap versus composition x data gives a bowing parameter of 1.45. This number lies between the value of 1.23 determined previously on ZnSeTe bulk crystals and the value of 1.621 reported on ZnSeTe epilayers. Low-temperature photoluminescence (PL) spectra were measured on six samples. The spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for each of the ZnSe(1-x)Te(x) samples, 0.09 less than x less than 0.39. For x=0.09, this emission energy is about 0.2 eV lower than the band gap energy measured at low temperature. As x increases the energy discrepancy gradually decreases and reduces to almost zero at x=0.4. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted as being associated with the exciton bound to Te clusters because of the high Te content in these samples.

  15. Characterization of LGALS3 (galectin-3) as a player in DNA damage response

    PubMed Central

    Carvalho, Renato S; Fernandes, Vanessa C; Nepomuceno, Thales C; Rodrigues, Deivid C; Woods, Nicholas T; Suarez-Kurtz, Guilherme; Chammas, Roger; Monteiro, Alvaro N; Carvalho, Marcelo A

    2014-01-01

    DNA damage repair (DDR) is an orchestrated process encompassing the injury detection to its complete resolution. DNA double-strand break lesions are repaired mainly by two distinct mechanisms: the error-free homologous recombination (HR) and the error-prone non-homologous end-joining. Galectin-3 (GAL3) is the unique member of the chimeric galectins subfamily and is reported to be involved in several cancer development and progression related events. Recently our group described a putative protein interaction between GAL3 and BARD1, the main partner of breast and ovarian cancer susceptibility gene product BRCA1, both involved in HR pathway. In this report we characterized GAL3/BARD1 protein interaction and evaluated the role of GAL3 in DDR pathways using GAL3 silenced human cells exposed to different DNA damage agents. In the absence of GAL3 we observed a delayed DDR response activation, as well as a decrease in the G2/M cell cycle checkpoint arrest associated with HR pathway. Moreover, using a TAP-MS approach we also determined the protein interaction network of GAL3. PMID:24755837

  16. Radiation damage characterization in reactor pressure vessel steels with nonlinear ultrasound

    SciTech Connect

    Matlack, K. H.; Kim, J.-Y.; Wall, J. J.; Qu, J.; Jacobs, L. J.

    2014-02-18

    Nuclear generation currently accounts for roughly 20% of the US baseload power generation. Yet, many US nuclear plants are entering their first period of life extension and older plants are currently undergoing assessment of technical basis to operate beyond 60 years. This means that critical components, such as the reactor pressure vessel (RPV), will be exposed to higher levels of radiation than they were originally intended to withstand. Radiation damage in reactor pressure vessel steels causes microstructural changes such as vacancy clusters, precipitates, dislocations, and interstitial loops that leave the material in an embrittled state. The development of a nondestructive evaluation technique to characterize the effect of radiation exposure on the properties of the RPV would allow estimation of the remaining integrity of the RPV with time. Recent research has shown that nonlinear ultrasound is sensitive to radiation damage. The physical effect monitored by nonlinear ultrasonic techniques is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave, arising from the interaction of the ultrasonic wave with microstructural features such as dislocations, precipitates, and their combinations. Current findings relating the measured acoustic nonlinearity parameter to increasing levels of neutron fluence for different representative RPV materials are presented.

  17. Characterization and damaging law of CFC for high heat flux actively cooled plasma facing components

    NASA Astrophysics Data System (ADS)

    Chevet, G.; Martin, E.; Boscary, J.; Camus, G.; Herb, V.; Schlosser, J.; Escourbiac, F.; Missirlian, M.

    2011-10-01

    The carbon fiber reinforced carbon composite (CFC) Sepcarb N11 has been used in the Tore Supra (TS) tokamak (Cadarache, France) as armour material for the plasma facing components. For the fabrication of the Wendelstein 7-X (W7-X) divertor (Greifswald, Germany), the NB31 material was chosen. For the fabrication of the ITER divertor, two potential CFC candidates are the NB31 and NB41 materials. In the case of Tore Supra, defects such as microcracks or debonding were found at the interface between CFC tile and copper heat sink. A mechanical characterization of the behaviour of N11 and NB31 was undertaken, allowing the identification of a damage model and finite element calculations both for flat tiles (TS and W7-X) and monoblock (ITER) armours. The mechanical responses of these CFC materials were found almost linear under on-axis tensile tests but highly nonlinear under shear tests or off-axis tensile tests. As a consequence, damage develops within the high shear-stress zones.

  18. Modeling nonlinearities of ultrasonic waves for fatigue damage characterization: theory, simulation, and experimental validation.

    PubMed

    Hong, Ming; Su, Zhongqing; Wang, Qiang; Cheng, Li; Qing, Xinlin

    2014-03-01

    A dedicated modeling technique for comprehending nonlinear characteristics of ultrasonic waves traversing in a fatigued medium was developed, based on a retrofitted constitutive relation of the medium by considering the nonlinearities originated from material, fatigue damage, as well as the "breathing" motion of fatigue cracks. Piezoelectric wafers, for exciting and acquiring ultrasonic waves, were integrated in the model. The extracted nonlinearities were calibrated by virtue of an acoustic nonlinearity parameter. The modeling technique was validated experimentally, and the results showed satisfactory consistency in between, both revealing: the developed modeling approach is able to faithfully simulate fatigue crack-incurred nonlinearities manifested in ultrasonic waves; a cumulative growth of the acoustic nonlinearity parameter with increasing wave propagation distance exists; such a parameter acquired via a sensing path is nonlinearly related to the offset distance from the fatigue crack to that sensing path; and neither the incidence angle of the probing wave nor the length of the sensing path impacts on the parameter significantly. This study has yielded a quantitative characterization strategy for fatigue cracks using embeddable piezoelectric sensor networks, facilitating deployment of structural health monitoring which is capable of identifying small-scale damage at an embryo stage and surveilling its growth continuously. PMID:24156928

  19. Damage Characterization of EBC-SiCSiC Ceramic Matrix Composites Under Imposed Thermal Gradient Testing

    NASA Technical Reports Server (NTRS)

    Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

    2014-01-01

    Due to their high temperature capabilities, Ceramic Matrix Composite (CMC) components are being developed for use in hot-section aerospace engine applications. Harsh engine environments have led to the development of Environmental Barrier Coatings (EBCs) for silicon-based CMCs to further increase thermal and environmental capabilities. This study aims at understanding the damage mechanisms associated with these materials under simulated operating conditions. A high heat-flux laser testing rig capable of imposing large through-thickness thermal gradients by means of controlled laser beam heating and back-side air cooling is used. Tests are performed on uncoated composites, as well as CMC substrates that have been coated with state-of-the-art ceramic EBC systems. Results show that the use of the EBCs may help increase temperature capability and creep resistance by reducing the effects of stressed oxidation and environmental degradation. Also, the ability of electrical resistance (ER) and acoustic emission (AE) measurements to monitor material condition and damage state during high temperature testing is shown; suggesting their usefulness as a valuable health monitoring technique. Micromechanics models are used to describe the localized stress state of the composite system, which is utilized along with ER modeling concepts to develop an electromechanical model capable of characterizing material behavior.

  20. Damage characterization in dimension limestone cladding using noncollinear ultrasonic wave mixing

    NASA Astrophysics Data System (ADS)

    McGovern, Megan; Reis, Henrique

    2016-01-01

    A method capable of characterizing artificial weathering damage in dimension stone cladding using access to one side only is presented. Dolomitic limestone test samples with increasing levels of damage were created artificially by exposing undamaged samples to increasing temperature levels of 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, and 700°C for a 90 min period of time. Using access to one side only, these test samples were nondestructively evaluated using a nonlinear approach based upon noncollinear wave mixing, which involves mixing two critically refracted dilatational ultrasonic waves. Criteria were used to assure that the detected scattered wave originated via wave interaction in the limestone and not from nonlinearities in the testing equipment. Bending tests were used to evaluate the flexure strength of beam samples extracted from the artificially weathered samples. It was observed that the percentage of strength reduction is linearly correlated (R2=98) with the temperature to which the specimens were exposed; it was noted that samples exposed to 400°C and 600°C had a strength reduction of 60% and 90%, respectively. It was also observed that results from the noncollinear wave mixing approach correlated well (R2=0.98) with the destructively obtained percentage of strength reduction.

  1. Biophysical characterization of skin damage and recovery after exposure to different surfactants.

    PubMed

    Bárány, E; Lindberg, M; Lodén, M

    1999-02-01

    The majority of adverse skin reactions to personal-care products are presumed to be caused by irritant substances, like surfactants. In this study, different aspects of the irritant reaction after a single exposure to 8 surfactants were characterized during 2 weeks. Solutions of 2% sodium lauryl sulfate, 5% sodium C12-15 pareth sulfate, 5% sodium cocoyl isethionate, 10% disodium laureth sulfosuccinate, 10% sodium cocoamphoacetate, 10% cocamide DEA, 10% cocamidopropyl betaine and 10% lauryl glucoside, respectively, were applied to the forearm of 12 volunteers. Clinical assessment, an evaporimeter, a laser Doppler flowmeter and a corneometer were used for evaluation. The surfactants induced different degrees of irritation. Erythema, transepidermal water loss and skin blood flow exhibited a similar time course, which seemed to be inversely related to the delayed scaling and reduced skin capacitance. The mechanism of the damaging effect of the surfactants seems to be similar, although some minor differences were noted. PMID:10048655

  2. Improved Climatological Characterization of Optical Turbulence for Space Optical Imaging and Communications

    NASA Astrophysics Data System (ADS)

    Alliss, R.; Felton, B.

    2010-09-01

    Optical turbulence (OT) acts to distort light in the atmosphere, degrading imagery from astronomical or other telescopes. In addition, the quality of service of a free space optical communications link may also be impacted. Some of the degradation due to turbulence can be corrected by adaptive optics. However, the severity of optical turbulence, and thus the amount of correction required, is largely dependent upon the turbulence at the location of interest. Therefore, it is vital to understand the climatology of optical turbulence at such locations. In many cases, it is impractical and expensive to setup instrumentation to characterize the climatology of OT, particularly for OCONUS locations, so simulations become a less expensive and convenient alternative. The strength of OT is characterized by the refractive index structure function Cn2, which in turn is used to calculate atmospheric seeing parameters. While attempts have been made to characterize Cn2 using empirical models, Cn2 can be calculated more directly from Numerical Weather Prediction (NWP) simulations using pressure, temperature, thermal stability, vertical wind shear, turbulent Prandtl number, and turbulence kinetic energy (TKE). In this work we use the Weather Research and Forecast (WRF) NWP model to generate Cn2 climatologies in the planetary boundary layer and free atmosphere, allowing for both point-to-point and ground-to-space seeing estimates of the Fried Coherence length (ro) and other seeing parameters. Simulations are performed using the Maui High Performance Computing Centers (MHPCC) Mana cluster. The WRF model is configured to run at 1km horizontal resolution over a domain covering several hundreds of kilometers. The vertical resolution varies from 25 meters in the boundary layer to 500 meters in the stratosphere. The model top is 20 km. We are interested in the variations in Cn2 and the Fried Coherence Length (ro). Nearly two years of simulations have been performed over various regions

  3. Mueller based scatterometry and optical characterization of semiconductor materials

    NASA Astrophysics Data System (ADS)

    Muthinti, Gangadhara Raja

    Scatterometry is one of the most useful metrology methods for the characterization and control of critical dimensions (CD) and the detailed topography of periodic structures found in microelectronics fabrication processes. Spectroscopic ellipsometry (SE) and normal incidence reflectometry (NI) based scatterometry are the most widely used optical methodologies for metrology of these structures. Evolution of better optical hardware and faster computing capabilities led to the development of Mueller Matrix (MM) based Scatterometry (MMS). Dimensional metrology using full Mueller Matrix (16 element) scatterometry in the wavelength range of 245nm-1000nm was discussed in this work. Unlike SE and NI, MM data provides complete information about the optical reflection and transmission of polarized light reflected from a sample. MM is a 4x4 transformation matrix (16 elements) describing the change in the intensities of incident polarized light expressed by means of a Stokes Vector. The symmetry properties associated with MM provide an excellent means of measuring and understanding the topography of the periodic nanostructures. Topography here refers to uniformity of the periodic order of arrayed structure. The advantage of MMS over traditional SE Scatterometry is the ability of MMS to measure samples that have anisotropic optical properties and depolarize light. The present work focuses on understanding the Mueller based Scatterometry with respect to other methodologies by a systematic approach. Several laterally complex nano-scale structures with dimensions in the order of nanometers were designed and fabricated using e-beam lithography. Also Mueller based analysis was used to extract profile information and anisotropy coefficients of complex 3D FinFET, SOI fin grating structures. Later, Spectroscopic Mueller matrix (all 16 elements) and SE data were collected in planar diffraction mode for the samples using a J.A. Woollam RC2(TM) Spectroscopic Ellipsometer. Nano

  4. Prostate cancer characterization by optical contrast enhanced photoacoustics

    NASA Astrophysics Data System (ADS)

    Xu, Guan; Qin, Ming; Mukundan, Ananya; Siddiqui, Javed; Takada, Marilia; Vilar-Saavedra, Paulo; Tomlins, Scott A.; Kopelman, Raoul; Wang, Xueding

    2016-03-01

    During the past decades, prostate cancer (PCa), with an annual incident rate much higher than any other cancer, is the most commonly diagnosed cancer in American men. PCa has a relatively low progression rate yet the survival percentage decreases dramatically once the cancer has metastasized. Identifying aggressive from indolent PCa to prevent metastasis and death is critical to improving outcomes for patients with PCa. Standard procedure for assessing the aggressiveness of PCa involves the removal of tumor tissues by transrectal (TR) ultrasound (US) guided needle biopsy. The microscopic architecture of the biopsied tissue is visualized by histological or immunohistochemical staining procedures. The heterogeneity of the microscopic architecture is characterized by a Gleason score, a quantitative description of the aggressiveness of PCa. Due to the inability to identify the cancer cells, most noninvasive imaging modalities can only provide diagnosis of PCa at limited accuracy. This study investigates the feasibility of identifying PCa tumors and characterizing the aggressiveness of PCa by photoacoustic imaging assisted by cancer targeting polyacrylamide (PAA) nanoparticles (NPs). PAA is a biocompatible material used in clinics for the past 20 years. PAA NPs can protect capsulated optical contrast agents from interference by enzymes and enable prolonged systematic circulation in the living biological environment. The cancer targeting mechanism is achieved by conjugating the NPs to F3 peptides, which trace nucleolin overexpressed on the surface of cancer cells. Preliminary studies have shown that the NPs are capable of staining the PCa cells in vivo.

  5. Preparation and characterization of {sup 238}Pu-ceramics for radiation damage experiments

    SciTech Connect

    DM Strachan; RD Scheele; WC Buchmiller; JD Vienna; RL Sell; RJ Elovich

    2000-06-15

    become metamict and the damage saturates. They will characterize and test these specimens every 6 months by (1) monitoring the dimensions, (2) monitoring the geometric and pycnometric densities, (3) monitoring the appearance, (4) determining the normalized amount leached during a 3-day, static, 90 C leach test in high purity water, and (5) monitoring the crystal structure with x-ray diffraction crystallography (XRD). In this paper, the authors document the preparation and initial characterization of the materials that were made in this study. The initial XRD characterizations indicate that the phase assemblages appear to be correct with the exception of the {sup 238}Pu-zirconolite baseline material. They made this latter material using too much Pu, so this material contains unreacted PuO{sub 2}. The characterization of the physical properties of these materials found that the densities for all but three materials appear to be > 94% of theoretical, and only a few of the specimens have significant cracking. Those with cracking were the {sup 239}Pu-zirconolite specimens, which were sintered with a heat-up rate of 5 C/min. They sintered the {sup 238}Pu-zirconolite specimens with a heat-up rate of 2.5 C/min and obtained specimens with only minor surface cracking. Elemental releases during the 3-day MCC leach tests show that the normalized elemental releases depend on (1) whether the Pu is {sup 239}Pu or {sup 238}Pu, (2) the material type, and (3) the identity of the constituent. The effect of the Pu isotope in the ceramic is most dramatic for Pu release, with nominally 50 to 100 times more Pu activity released from the {sup 238}Pu specimens. This is unlikely to be an early indicator of radiation damage, because of the short time between specimen preparation and testing. In contrast greater amounts of Mo are released from the {sup 239}Pu specimens. Of the contained constituents, Ca Al, Pu, and U are the species found at relatively higher levels in the leachates.

  6. Determining beam resistance of large-scale optics by measuring thresholds for surface damage caused by low-size laser beams

    NASA Astrophysics Data System (ADS)

    Dmitriev, D. I.; Ivanova, I. V.; Pasunkin, V. N.; Sirazetdinov, V. S.

    2010-07-01

    The paper describes an experimental method of determining probability density distribution for random threshold values of laser fluence, damaging surface of optical components. The method is as follows. Numerous surface sites of an optical component have been irradiated by a laser beam with a known non-uniform fluence distribution and magnitude sufficient for surface damage. Subsequently, the minimal fluence value ɛ has beens determined at the boundary of the damaged zone for each irradiation spot. It is shown that the sampling of minimal damage threshold values obtained from the above-described data assembly makes it possible to construct the probability density distribution f(ɛ). Knowledge of this distribution provides for the use of order statistics in damage threshold fluence data analysis and, thus, enhances accuracy and reliability of determination of surface strength for sizable optic components tested by small-diameter beams.

  7. Determining beam resistance of large-scale optics by measuring thresholds for surface damage caused by low-size laser beams

    NASA Astrophysics Data System (ADS)

    Dmitriev, D. I.; Ivanova, I. V.; Pasunkin, V. N.; Sirazetdinov, V. S.

    2011-03-01

    The paper describes an experimental method of determining probability density distribution for random threshold values of laser fluence, damaging surface of optical components. The method is as follows. Numerous surface sites of an optical component have been irradiated by a laser beam with a known non-uniform fluence distribution and magnitude sufficient for surface damage. Subsequently, the minimal fluence value ɛ has beens determined at the boundary of the damaged zone for each irradiation spot. It is shown that the sampling of minimal damage threshold values obtained from the above-described data assembly makes it possible to construct the probability density distribution f(ɛ). Knowledge of this distribution provides for the use of order statistics in damage threshold fluence data analysis and, thus, enhances accuracy and reliability of determination of surface strength for sizable optic components tested by small-diameter beams.

  8. Suppression of nano-absorbing precursors and damage mechanism in optical coatings for 3ω mirrors.

    PubMed

    Wang, Hu; Qi, Hongji; Zhang, Weili; Sun, Jian; Chai, Yingjie; Tu, Feifei; Zhao, Jiaoling; Yu, Zhen; Wang, Bin; Zhu, Meiping; Yi, Kui; Shao, Jianda

    2016-03-15

    Damage precursors in the 3ω (351 nm) mirror for a high-power laser system are investigated as well as the relevant damage mechanisms. The precursors are classified into two ensembles according to the different laser resistance and damage features. The former is nano-absorbing precursors, which are sensitive to the standing wave electric field and vulnerable to the laser irradiation. The latter is submicrometer nodular defects, which have higher laser resistance and are sensitive to the adhesion strength between the fluoride coatings and oxide coatings. The damage due to nano-absorbing precursors is efficiently suppressed with the double stack design that screens the electric field in the oxides. Currently, the nodular seed is major originating from the Al2O3/SiO2 stack. Even for the same defect type and mirror, the final damage features are dependent on the local mechanical properties at the irradiation location. The investigations of the damage mechanisms provide a direction to further improve the laser-induced damage threshold of the 3ω mirror. PMID:26977671

  9. Micromirrors for multiobject spectroscopy: optical and cryogenic characterization

    NASA Astrophysics Data System (ADS)

    Waldis, Severin; Zamkotsian, Frederic; Lanzoni, Patrick; Noell, Wilfried; de Rooij, Nico

    2008-02-01

    We are developing micromirror arrays (MMA) for future generation infrared multiobject spectroscopy (MOS) requiring cryogenic environment. So far we successfully realized small arrays of 5×5 single-crystalline silicon micromirrors. The 100μm ×200μm micromirrors show excellent surface quality and can be tilted by electrostatic actuation yielding 20° mechanical tilt-angle. An electromechanical locking mechanism has been demonstrated that provides uniform tilt-angle within one arc minute precision over the whole array. Infrared MOS requires cryogenic environment and coated mirrors, silicon being transparent in the infrared. We report on the influence of the reflective coating on the mirror quality and on the characterization of the MMA in cryogenic environment. A Veeco/Wyko optical profiler was used to measure the flatness of uncoated and coated mirrors. The uncoated and unactuated micromirrors showed a peak-to-valley deformation (PTV) of below 10nm. An evaporated 10nm chrome/50nm gold coating on the mirror increased the PTV to 35nm; by depositing the same layers on both sides of the mirrors the PTV was reduced down to 17nm. Cryogenic characterization was carried out on a custom built interferometric characterization bench onto which a cryogenic chamber was mounted. The chamber pressure was at 10e-6 mbar and the temperature measured right next to the micromirror device was 86K. The micromirrors could be actuated before, during and after cryogenic testing. The PTV of the chrome/gold coated mirrors increased from 35nm to 50nm, still remaining in the requirements of < lambda/20 for lambda=1μm.

  10. THz optics and metamaterials: Design, fabrication and characterization

    NASA Astrophysics Data System (ADS)

    Turaga, Shuvan Prashant

    In the past decade, terahertz(THz) based optics and metamaterials have been extensively researched to create components and devices in the frequency range of 0.1 to 5 THz also known as 'THz gap'. Metamaterials, in particular, have realized concepts such as negative refraction, slow light and superlensing through artificially engineered media. The naturally available materials have very weak interaction of terahertz light. Therefore, the design of THz metamaterials to manipulate THz radiation is an important task towards furthering the usage of terahertz light for practical applications. The thesis involved the development of two lab facilities for fabrication and characterization. A state-of-the-art two photon lithography( TPL) system was developed which enables us to manufacture 3D structures with sub-diffraction limit resolution(280nm at 800 nm wavelength). The software was written to enable easy fabrication of multiple structures with different algorithms. For characterizing our metamaterial structures in the terahertz regime, a THz time-domain spectroscopy(THz-TDS) and imaging system was built. This transmission based spectrometer has a dynamic range of 50 dB at 0.5 THz and a bandwidth of about 2.5 THz. To demonstrate the application of these home-built facilities, the metamaterials in the THz regime were fabricated using TPL and UV lithography. To investigate conductive coupling effects in meta-atoms, a new design was proposed, fabricated and characterized. As an application of TPL, free standing polymer helices were fabricated and coated with silver electroless plating. These silver helical metamaterials have potential application as circular polarizers in the MIR and THz regimes. The aspect ratio effects of these helical metamaterials were also studied in order to improve their polarizing performance.

  11. Experimental Determination of Damage Threshold Characteristics of IR Compatible Optical Materials

    SciTech Connect

    Soong, Ken

    2011-05-20

    The accelerating gradient in a laser-driven dielectric accelerating structure is often limited by the laser damage threshold of the structure. For a given laser-driven dielectric accelerator design, we can maximize the accelerating gradient by choosing the best combination of the accelerator's constituent material and operating wavelength. We present here a model of the damage mechanism from ultrafast infrared pulses and compare that model with experimental measurements of the damage threshold of bulk silicon. Additionally, we present experimental measurements of a variety of candidate materials, thin films, and nanofabricated accelerating structures.

  12. A ruggedness evaluation of procedures for damage threshold testing optical materials

    NASA Technical Reports Server (NTRS)

    Hooker, Matthew W.; Thomas, Milfred E.; Wise, Stephanie A.; Tappan, Nina D.

    1995-01-01

    A ruggedness evaluation of approaches to damage threshold testing was performed to determine the influence of three procedural variables on damage threshold data. The differences between the number of test sites evaluated at an applied fluence level (1 site versus 10 sites), the number of laser pulses at each test site (1 pulse versus 200 pulses), and the beam diameter (0.35 mm versus 0.70 mm) were all found to significantly influence the damage threshold data over a 99-percent confidence interval.

  13. Limestone characterization to model damage from acidic precipitation: Effect of pore structure on mass transfer

    USGS Publications Warehouse

    Leith, S.D.; Reddy, M.M.; Irez, W.F.; Heymans, M.J.

    1996-01-01

    The pore structure of Salem limestone is investigated, and conclusions regarding the effect of the pore geometry on modeling moisture and contaminant transport are discussed based on thin section petrography, scanning electron microscopy, mercury intrusion porosimetry, and nitrogen adsorption analyses. These investigations are compared to and shown to compliment permeability and capillary pressure measurements for this common building stone. Salem limestone exhibits a bimodal pore size distribution in which the larger pores provide routes for convective mass transfer of contaminants into the material and the smaller pores lead to high surface area adsorption and reaction sites. Relative permeability and capillary pressure measurements of the air/water system indicate that Salem limestone exhibits high capillarity end low effective permeability to water. Based on stone characterization, aqueous diffusion and convection are believed to be the primary transport mechanisms for pollutants in this stone. The extent of contaminant accumulation in the stone depends on the mechanism of partitioning between the aqueous and solid phases. The described characterization techniques and modeling approach can be applied to many systems of interest such as acidic damage to limestone, mass transfer of contaminants in concrete and other porous building materials, and modeling pollutant transport in subsurface moisture zones.

  14. Field and airborne spectral characterization of suspected damage in red spruce (picea rubens) from Vermont

    NASA Technical Reports Server (NTRS)

    Rock, B. N.; Vogelmann, J. E.; Williams, D. L.

    1985-01-01

    The utilization of remote sensing to monitor forest damage due to acid deposition is investigated. Spectral and water measurements and aircraft radiance data of red spruce and balsam fir, collected in Camels Hump Mountain and Ripton, Vermont between August 13-20, 1984, are analyzed to evaluate the damage levels of the trees. Variations in reflectance features and canopy moisture content are studied. It is observed that damage correlates with elevation (greater damage at higher elevations); xylem water column tension is greater at higher damage sites; and a 'blue shift' is indicated in the spectral data at high damage sites.

  15. Fractal mechanism for characterizing singularity of mode shape for damage detection

    SciTech Connect

    Cao, M. S.; Ostachowicz, W.; Bai, R. B.; Radzieński, M.

    2013-11-25

    Damage is an ordinary physical phenomenon jeopardizing structural safety; damage detection is an ongoing interdisciplinary issue. Waveform fractal theory has provided a promising resource for detecting damage in plates while presenting a concomitant problem: susceptibility to false features of damage. This study proposes a fractal dimension method based on affine transformation to address this problem. Physical experiments using laser measurement demonstrate that this method can substantially eliminate false features of damage and accurately identify complex cracks in plates, providing a fundamental mechanism that brings the merits of waveform fractal theory into full play in structural damage detection applications.

  16. A high accuracy femto-/picosecond laser damage test facility dedicated to the study of optical thin films

    SciTech Connect

    Mangote, B.; Gallais, L.; Zerrad, M.; Lemarchand, F.; Gao, L. H.; Commandre, M.; Lequime, M.

    2012-01-15

    A laser damage test facility delivering pulses from 100 fs to 3 ps and designed to operate at 1030 nm is presented. The different details of its implementation and performances are given. The originality of this system relies the online damage detection system based on Nomarski microscopy and the use of a non-conventional energy detection method based on the utilization of a cooled CCD that offers the possibility to obtain the laser induced damage threshold (LIDT) with high accuracy. Applications of this instrument to study thin films under laser irradiation are presented. Particularly the deterministic behavior of the sub-picosecond damage is investigated in the case of fused silica and oxide films. It is demonstrated that the transition of 0-1 damage probability is very sharp and the LIDT is perfectly deterministic at few hundreds of femtoseconds. The damage process in dielectric materials being the results of electronic processes, specific information such as the material bandgap is needed for the interpretation of results and applications of scaling laws. A review of the different approaches for the estimation of the absorption gap of optical dielectric coatings is conducted and the results given by the different methods are compared and discussed. The LIDT and gap of several oxide materials are then measured with the presented instrument: Al{sub 2}O{sub 3}, Nb{sub 2}O{sub 5}, HfO{sub 2}, SiO{sub 2}, Ta{sub 2}O{sub 5}, and ZrO{sub 2}. The obtained relation between the LIDT and gap at 1030 nm confirms the linear evolution of the threshold with the bandgap that exists at 800 nm, and our work expands the number of tested materials.

  17. Damage of multilayer optics with varying capping layers induced by focused extreme ultraviolet beam

    SciTech Connect

    Jody Corso, Alain; Nicolosi, Piergiorgio; Nardello, Marco; Guglielmina Pelizzo, Maria; Department of Information Engineering, University of Padova, via Gradenigo 6 Zuppella, Paola; Barkusky, Frank; KLA-Tencor, 5 Technology Dr., Milpitas, California 95035 ; Mann, Klaus; Mueller, Matthias

    2013-05-28

    Extreme ultraviolet Mo/Si multilayers protected by capping layers of different materials were exposed to 13.5 nm plasma source radiation generated with a table-top laser to study the irradiation damage mechanism. Morphology of single-shot damaged areas has been analyzed by means of atomic force microscopy. Threshold fluences were evaluated for each type of sample in order to determine the capability of the capping layer to protect the structure underneath.

  18. Damage testing of critical optical components for high power ultra-fast lasers

    NASA Astrophysics Data System (ADS)

    Chowdhury, Enam; Poole, Patrick; Jiang, Sheng; Taylor, Brittany; Daskalova, Rebecca; Van Woerkom, Linn; Freeman, Richard; Smith, Douglas

    2010-11-01

    Mirrors and gratings used in high power ultra fast lasers require a broad bandwidth and high damage fluence, which is essential to the design and construction of petawatt class short pulse lasers. Damage fluence of several commercially available high energy broad band dielectric mirrors with over 100 nm bandwidth at 45 degree angle of incidence, and pulse compression reflection gratings with gold coating with varying processing conditions is studied using a 25 femtosecond ultra-fast laser.

  19. Pulse-width and pulse-shape dependencies of laser-induced damage threshold to transparent optical materials

    NASA Astrophysics Data System (ADS)

    Koldunov, M. F.; Manenkov, Alexander A.; Pokotilo, I. L.

    1996-05-01

    Theory of pulsewidth dependence of laser induced damage threshold (LIDT) in transparent solids is presented. The damage is supposed to be initiated by thermal explosion of absorbing inclusions. The investigation of thermal explosion is based on an analysis of the heat transfer equation and a new approach to solving this equation is developed allowing to study kinetics of thermal explosion without any modeling presentation of an absorption mechanism. It is shown that the key parameter determining a dependence of LIDT upon a laser pulsewidth, (tau) p, is the heat transfer time, (tau) , from an inclusion to a surrounding medium. At (tau) p >> (tau) a damage threshold is characterized by a laser radiation intensity, whereas at (tau) p << (tau) --by an energy density. The pulsewidth dependence of the LIDT has been investigated for rectangular and gaussian shapes of laser pulses and it has been established that the dependencies considerably differ in these two cases in a range of (tau) p approximately (tau) . An effect of damage statistics, connected with a random spatial distribution of inclusions in a material, is also investigated. For the case of one-type inclusions (single-(tau) inclusions) it is shown: the statistics does not change a functional form of the pulsewidth dependence of the LIDT and correct only the LIDT values by a spot-size factor. Theoretical results are compared with experimental data published by different research groups for the laser damage in a nanosecond-picosecond region.

  20. Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location

    DOEpatents

    Weiss, J.D.

    1995-08-29

    A shock velocity and damage location sensor providing a means of measuring shock speed and damage location is disclosed. The sensor consists of a long series of time-of-arrival ``points`` constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the ``points`` of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor. 6 figs.

  1. Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location

    DOEpatents

    Weiss, Jonathan D.

    1995-01-01

    A shock velocity and damage location sensor providing a means of measuring shock speed and damage location. The sensor consists of a long series of time-of-arrival "points" constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the "points" of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor.

  2. Electrical, Electrochemical, and Optical Characterization of Ceria Films

    NASA Astrophysics Data System (ADS)

    Oh, Tae-Sik

    Acceptor-doped ceria has been recognized as a promising intermediate temperature solid oxide fuel cell electrode/electrolyte material. For practical implementation of ceria as a fuel cell electrolyte and for designing model experiments for electrochemical activity, it is necessary to fabricate thin films of ceria. Here, metal-organic chemical vapor deposition was carried out in a homemade reactor to grow ceria films for further electrical, electrochemical, and optical characterization. Doped/undoped ceria films are grown on single crystalline oxide wafers with/without Pt line pattern or Pt solid layer. Deposition conditions were varied to see the effect on the resultant film property. Recently, proton conduction in nanograined polycrystalline pellets of ceria drew much interest. Thickness-mode (through-plane, z-direction) electrical measurements were made to confirm the existence of proton conductivity and investigate the nature of the conduction pathway: exposed grain surfaces and parallel grain boundaries. Columnar structure presumably favors proton conduction, and we have found measurable proton conductivity enhancement. Electrochemical property of gas-columnar ceria interface on the hydrogen electrooxidation is studied by AC impedance spectroscopy. Isothermal gas composition dependence of the electrode resistance was studied to elucidate Sm doping level effect and microstructure effect. Significantly, preferred orientation is shown to affect the gas dependence and performance of the fuel cell anode. A hypothesis is proposed to explain the origin of this behavior. Lastly, an optical transmittance based methodology was developed to obtain reference refractive index and microstructural parameters (thickness, roughness, porosity) of ceria films via subsequent fitting procedure.

  3. Characterizing inertial and convective optical turbulence by detrended fluctuation analysis

    NASA Astrophysics Data System (ADS)

    Funes, Gustavo; Figueroa, Eduardo; Gulich, Damián.; Zunino, Luciano; Pérez, Darío. G.

    2013-10-01

    Atmospheric turbulence is usually simulated at the laboratory by generating convective free flows with hot surfaces, or heaters. It is tacitly assumed that propagation experiments in this environment are comparable to those usually found outdoors. Nevertheless, it is unclear under which conditions the analogy between convective and isotropic turbulence is valid; that is, obeying Kolmogorov isotropic models. For instance, near-ground-level turbulence often is driven by shear ratchets deviating from established inertial models. In this case, a value for the structure constant can be obtained but it would be unable to distinguish between both classes of turbulence. We have performed a conceptually simple experiment of laser beam propagation through two types of artificial turbulence: isotropic turbulence generated by a turbulator [Proc. SPIE 8535, 853508 (2012)], and convective turbulence by controlling the temperature of electric heaters. In both cases, a thin laser beam propagates across the turbulent path, and its wandering is registered by a position sensor detector. The strength of the optical turbulence, in terms of the structure constant, is obtained from the wandering variance. It is expressed as a function of the temperature difference between cold and hot sources in each setup. We compare the time series behaviour for each turbulence with increasing turbulence strength by estimating the Hurst exponent, H, through detrended fluctuation analysis (DFA). Refractive index fluctuations are inherently fractal; this characteristic is reflected in their spectra power-law dependence—in the inertial range. This fractal behaviour is inherited by time series of optical quantities, such as the wandering, by the occurrence of long-range correlations. By analyzing the wandering time series with this technique, we are able to correlate the turbulence strength to the value of the Hurt exponent. Ultimately, we characterize both types of turbulence.

  4. Optical Characterization of Bulk ZnSeTe Solid Solutions

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, S.; Zhu, Shen; Lehoczky, S. L.; Wang, Ling Jun

    2000-01-01

    Optical characterization was performed on wafers sliced from crystals of ZnSe, ZnTe and ZnSe (sub 1-x) Te (sub x) (0 less than x less than 0.4) grown by physical vapor transport technique. The energy band gaps at room temperature were determined from optical transmission measurements on 11 wafers. The best fit to the band gap vs. composition, x, data gives a bowing parameter of 1.336 which is between the value of 1.23 determined previously on ZnSeTe bulk crystals by reflectivity and the value of 1.621 reported on epilayers by photoconductivity. Low-temperature photoluminescence (PL) spectra were measured on 6 samples. The spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for each of the ZnSe (sub 1-x) Te (sub x) samples, 0.09 less than x less than 0.39. For x = 0.09, this emission energy is about 0.2eV lower than the band gap energy measured at low temperature. As x increases the energy discrepancy gradually decreases and reduces to almost zero at x = 0.4. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted to be associated with the exciton bound to Te clusters because of the high Te content in these samples.

  5. Co-validation of three methods for optical characterization of point-focus concentrators

    NASA Astrophysics Data System (ADS)

    Wendelin, T. J.; Grossman, J. W.

    Three different methods for characterizing point-focus solar concentrator optical performance have been developed for specific applications. These methods include a laser ray trace technique called the Scanning Hartmann Optical Test, a video imaging process called the 2f Technique and actual on-sun testing in conjunction with optical computer modeling. Three concentrator test articles, each of a different design, were characterized using at least two of the methods and, in one case, all three. The results of these tests are compared in order to validate the methods. Excellent agreement is observed in the results, suggesting that the techniques provide consistent and accurate characterizations of solar concentrator optics.

  6. Co-validation of three methods for optical characterization of point-focus concentrators

    SciTech Connect

    Wendelin, T.J.; Grossman, J.W.

    1994-10-01

    Three different methods for characterizing point-focus solar concentrator optical performance have been developed for specific applications. These methods include a laser ray trace technique called the Scanning Hartmann Optical Test, a video imaging process called the 2f Technique and actual on-sun testing in conjunction with optical computer modeling. Three concentrator test articles, each of a different design, were characterized using at least two of the methods and, in one case, all three. The results of these tests are compared in order to validate the methods. Excellent agreement is observed in the results, suggesting that the techniques provide consistent and accurate characterizations of solar concentrator optics.

  7. The SCITEAS experiment: Optical characterizations of sublimating icy planetary analogues

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Jost, B.; Poch, O.; El-Maarry, M. R.; Vuitel, B.; Thomas, N.

    2015-05-01

    We have designed and built a laboratory facility to investigate the spectro-photometric and morphologic properties of different types of ice-bearing planetary surface analogs and follow their evolution upon exposure to a low pressure and low temperature environment. The results obtained with this experiment are used to verify and improve our interpretations of current optical remote-sensing datasets. They also provide valuable information for the development and operation of future optical instruments. The Simulation Chamber for Imaging the Temporal Evolution of Analogue Samples (SCITEAS) is a small thermal vacuum chamber equipped with a variety of ports and feedthroughs that permit both in-situ and remote characterizations as well as interacting with the sample. A large quartz window located directly above the sample is used to observe its surface from outside with a set of visible and near-infrared cameras. The sample holder can be easily and quickly inserted and removed from the chamber and is compatible with the other measurement facilities of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern. We report here on the results of two of the first experiments performed in the SCITEAS chamber. In the first experiment, fine-grained water ice mixed with dark organic and mineral matter was left to sublime in vacuum and at low temperature, simulating the evolution of the surface of a comet nucleus approaching the Sun. We observed and characterized the formation and evolution of a crust of refractory organic and mineral matter at the surface of the sample and linked the evolution of its structure and texture to its spectro-photometric properties. In the second experiment, a frozen soil was prepared by freezing a mixture of smectite mineral and water. The sample was then left to sublime for 6 h to simulate the loss of volatiles from icy soil at high latitudes on Mars. Colour images were produced using the definitions of the

  8. Spatiotemporal characterization of ionizing radiation induced DNA damage foci and their relation to chromatin organization

    SciTech Connect

    Costes, Sylvain V; Chiolo, Irene; Pluth, Janice M.; Barcellos-Hoff, Mary Helen; Jakob, Burkhard

    2009-09-15

    DNA damage sensing proteins have been shown to localize to the sites of DSB within seconds to minutes following ionizing radiation (IR) exposure, resulting in the formation of microscopically visible nuclear domains referred to as radiation-induced foci (RIF). This review characterizes the spatio-temporal properties of RIF at physiological doses, minutes to hours following exposure to ionizing radiation, and it proposes a model describing RIF formation and resolution as a function of radiation quality and nuclear densities. Discussion is limited to RIF formed by three interrelated proteins ATM (Ataxia telangiectasia mutated), 53BP1 (p53 binding protein 1) and ?H2AX (phosphorylated variant histone H2AX). Early post-IR, we propose that RIF mark chromatin reorganization, leading to a local nuclear scaffold rigid enough to keep broken DNA from diffusing away, but open enough to allow the repair machinery. We review data indicating clear kinetic and physical differences between RIF emerging from dense and uncondensed regions of the nucleus. At later time post-IR, we propose that persistent RIF observed days following exposure to ionizing radiation are nuclear ?scars? marking permanent disruption of the chromatin architecture. When DNA damage is resolved, such chromatin modifications should not necessarily lead to growth arrest and it has been shown that persistent RIF can replicate during mitosis. Thus, heritable persistent RIF spanning over tens of Mbp may affect the transcriptome of a large progeny of cells. This opens the door for a non DNA mutation-based mechanism of radiation-induced phenotypes.

  9. Detection of vesicant-induced upper airway mucosa damage in the hamster cheek pouch model using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Hammer-Wilson, Marie J.; Nguyen, Vi; Jung, Woong-Gyu; Ahn, Yehchen; Chen, Zhongping; Wilder-Smith, Petra

    2010-01-01

    Hamster cheek pouches were exposed to 2-chloroethyl ethyl sulfide [CEES, half-mustard gas (HMG)] at a concentration of 0.4, 2.0, or 5.0 mg/ml for 1 or 5 min. Twenty-four hours post-HMG exposure, tissue damage was assessed by both stereomicrography and optical coherence tomography (OCT). Damage that was not visible on gross visual examination was apparent in the OCT images. Tissue changes were found to be dependent on both HMG concentration and exposure time. The submucosal and muscle layers of the cheek pouch tissue showed the greatest amount of structural alteration. Routine light microscope histology was performed to confirm the OCT observations.

  10. Detection of vesicant-induced upper airway mucosa damage in the hamster cheek pouch model using optical coherence tomography.

    PubMed

    Hammer-Wilson, Marie J; Nguyen, Vi; Jung, Woong-Gyu; Ahn, Yehchen; Chen, Zhongping; Wilder-Smith, Petra

    2010-01-01

    Hamster cheek pouches were exposed to 2-chloroethyl ethyl sulfide [CEES, half-mustard gas (HMG)] at a concentration of 0.4, 2.0, or 5.0 mg/ml for 1 or 5 min. Twenty-four hours post-HMG exposure, tissue damage was assessed by both stereomicrography and optical coherence tomography (OCT). Damage that was not visible on gross visual examination was apparent in the OCT images. Tissue changes were found to be dependent on both HMG concentration and exposure time. The submucosal and muscle layers of the cheek pouch tissue showed the greatest amount of structural alteration. Routine light microscope histology was performed to confirm the OCT observations. PMID:20210463

  11. Surface acoustic wave characterization of optical sol-gel thin layers.

    PubMed

    Fall, Dame; Compoint, François; Duquennoy, Marc; Piombini, Hervé; Ouaftouh, Mohammadi; Jenot, Frédéric; Piwakowski, Bogdan; Belleville, Philippe; Ambard, Chrystel

    2016-05-01

    Controlling the thin film deposition and mechanical properties of materials is a major challenge in several fields of application. We are more particularly interested in the characterization of optical thin layers produced using sol-gel processes to reduce laser-induced damage. The mechanical properties of these coatings must be known to control and maintain optimal performance under various solicitations during their lifetime. It is therefore necessary to have means of characterization adapted to the scale and nature of the deposited materials. In this context, the dispersion of ultrasonic surface waves induced by a micrometric layer was studied on an amorphous substrate (fused silica) coated with a layer of ormosil using a sol-gel process. Our ormosil material is a silica-PDMS mixture with a variable polydimethylsiloxane (PDMS) content. The design and implementation of Surface Acoustic Wave InterDigital Transducers (SAW-IDT) have enabled quasi-monochromatic Rayleigh-type SAW to be generated and the dispersion phenomenon to be studied over a wide frequency range. Young's modulus and Poisson's ratio of coatings were estimated using an inverse method. PMID:26930248

  12. Acousto-optic tunable filter for dispersion characterization of time-domain optical coherence tomography systems.

    PubMed

    Chin, Catherine; Toadere, Florin; Feuchter, Thomas; Leick, Lasse; Moselund, Peter; Bradu, Adrian; Podoleanu, Adrian

    2016-07-20

    A broadband supercontinuum light source with an acousto-optic tunable filter (AOTF) are used to characterize dispersion in two time-domain OCT systems, at 850 and 1300 nm. The filter is designed to sweep across two spectral ranges, which are restricted here from 800 to 900 nm and from 1200 to 1500 nm, respectively. Dispersion compensation for 850 nm was achieved with a spectral delay line. Dispersion compensation for 1300 nm was achieved using BK 7 rod glasses in the reference arm. The AOTF allows evaluation of dispersion in under as well as overcompensated systems. The AOTF method is based on wavelength dependence of the optical path difference corresponding to the maximum strength of the interference signal recorded using a mirror as object. Comparison is made between the AOTF method and the more usual method based on measurement of the full width at half-maximum of the autocorrelation peak. This comparison shows that the AOTF method is more accurate in terms of evaluation of the dispersion left uncompensated after each adjustment. The AOTF method additionally provides information on the direction of dispersion compensation. PMID:27463927

  13. HF-based etching processes for improving laser damage resistance of fused silica optical surfaces

    SciTech Connect

    Suratwala, T I; Miller, P E; Bude, J D; Steele, R A; Shen, N; Monticelli, M V; Feit, M D; Laurence, T A; Norton, M A; Carr, C W; Wong, L L

    2010-02-23

    The effect of various HF-based etching processes on the laser damage resistance of scratched fused silica surfaces has been investigated. Conventionally polished and subsequently scratched fused silica plates were treated by submerging in various HF-based etchants (HF or NH{sub 4}F:HF at various ratios and concentrations) under different process conditions (e.g., agitation frequencies, etch times, rinse conditions, and environmental cleanliness). Subsequently, the laser damage resistance (at 351 or 355 nm) of the treated surface was measured. The laser damage resistance was found to be strongly process dependent and scaled inversely with scratch width. The etching process was optimized to remove or prevent the presence of identified precursors (chemical impurities, fracture surfaces, and silica-based redeposit) known to lead to laser damage initiation. The redeposit precursor was reduced (and hence the damage threshold was increased) by: (1) increasing the SiF{sub 6}{sup 2-} solubility through reduction in the NH4F concentration and impurity cation impurities, and (2) improving the mass transport of reaction product (SiF{sub 6}{sup 2-}) (using high frequency ultrasonic agitation and excessive spray rinsing) away from the etched surface. A 2D finite element crack-etching and rinsing mass transport model (incorporating diffusion and advection) was used to predict reaction product concentration. The predictions are consistent with the experimentally observed process trends. The laser damage thresholds also increased with etched amount (up to {approx}30 {micro}m), which has been attributed to: (1) etching through lateral cracks where there is poor acid penetration, and (2) increasing the crack opening resulting in increased mass transport rates. With the optimized etch process, laser damage resistance increased dramatically; the average threshold fluence for damage initiation for 30 {micro}m wide scratches increased from 7 to 41 J/cm{sup 2}, and the statistical

  14. Fabrication and optical characterization of Bragg resonance luminescence porous silicon

    NASA Astrophysics Data System (ADS)

    Park, Mi-Ae; Sohn, Honglae

    2016-01-01

    The synthesis and characterization of Bragg resonance luminescence porous silicon (BRL PS) exhibiting both optical reflectivity and strong narrow visible photoluminescence (PL) prepared from highly doped n-type silicon wafers through the electrochemical etching are reported. BRL PS showing the luminescence at 702 nm with an excitation wavelength of 400 nm was prepared by applying the current of 360 mA cm-2 for 1.6 s and 75 mA cm-2 for 3.6 s with 50 repeats in etching solution of 1:1 volume mixture of absolute ethanol and aqueous 48% HF. BRL PS exhibited sharp PL peak which reached full width at half maximum of 14 nm, originated from the result of Bragg resonance in PS multilayer. The sharp PL peak at 702 nm of BRL PS is the second-order transmitted luminescence peak by Bragg resonance phenomenon. The simultaneous measurement of reflectivity and luminescence in the BRL PS under an exposure to a vapor flux of acetone showed that a narrow transmitted luminescence based on Bragg resonance in BRL PS quenched as well as the red-shifted by 37 nm of reflection wavelength was observed. A dramatic quenching PL of BRL PS compare to that of the monolayer PS, is probably due to the Bragg resonance effect on luminescence.

  15. Mechanical characterization of unplasticised polyvinylchloride thick pipes by optical methods

    NASA Astrophysics Data System (ADS)

    Mihaylova, E.; Potelon, B.; Reddy, S.; Toal, V.; Smith, C.

    2004-06-01

    In this work a number of techniques (electronic speckle pattern interferometry, holographic interferometry, strain gauge and finite element method) are brought to bear in order to establish consistency in the results of strain measurement. This is necessary if optical non-destructive testing methods, such as those used here, are to gain acceptance for routine industrial use. The FE model provides a useful check. Furthermore, ESPI fringe data facilitates the extension of FE models, an approach that is of growing importance in component testing. The use of in-plane and out-of-plane sensitive electronic speckle pattern interferometry (ESPI) for non-destructive material characterization of thick unplasticised polyvinylchloride (uPVC) pipes is presented. A test rig has been designed for stressing pipes by internal pressure. ESPI gives a complete mapping of the displacement field over the area imaged by the video camera. The results for the strain of uPVC obtained from ESPI data and from strain gauges are in good agreement. The value of Young's modulus has been obtained from the fringe data and compared with results obtained using holographic interferometry and from strain gauge measurements. The FE model also produces fringe data that is consistent with the ESPI results.

  16. Advanced optical measurements for characterizing photophysical properties of single nanoparticles.

    SciTech Connect

    Polsky, Ronen; Davis, Ryan W.; Arango, Dulce C.; Brozik, Susan Marie; Wheeler, David Roger

    2009-09-01

    Formation of complex nanomaterials would ideally involve single-pot reaction conditions with one reactive site per nanoparticle, resulting in a high yield of incrementally modified or oriented structures. Many studies in nanoparticle functionalization have sought to generate highly uniform nanoparticles with tailorable surface chemistry necessary to produce such conjugates, with limited success. In order to overcome these limitations, we have modified commercially available nanoparticles with multiple potential reaction sites for conjugation with single ssDNAs, proteins, and small unilamellar vesicles. These approaches combined heterobifunctional and biochemical template chemistries with single molecule optical methods for improved control of nanomaterial functionalization. Several interesting analytical results have been achieved by leveraging techniques unique to SNL, and provide multiple paths for future improvements for multiplex nanoparticle synthesis and characterization. Hyperspectral imaging has proven especially useful for assaying substrate immobilized fluorescent particles. In dynamic environments, temporal correlation spectroscopies have been employed for tracking changes in diffusion/hydrodynamic radii, particle size distributions, and identifying mobile versus immobile sample fractions at unbounded dilution. Finally, Raman fingerprinting of biological conjugates has been enabled by resonant signal enhancement provided by intimate interactions with nanoparticles and composite nanoshells.

  17. Characterization of PET preforms using spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Hosseiny, Hamid; Ferreira, Manuel João.; Martins, Teresa; Carmelo Rosa, Carla

    2013-11-01

    Polyethylene terephthalate (PET) preforms are massively produced nowadays with the purpose of producing food and beverages packaging and liquid containers. Some varieties of these preforms are produced as multilayer structures, where very thin inner film(s) act as a barrier for nutrients leakage. The knowledge of the thickness of this thin inner layer is important in the production line. The quality control of preforms production requires a fast approach and normally the thickness control is performed by destructive means out of the production line. A spectral domain optical coherence tomography (SD-OCT) method was proposed to examine the thin layers in real time. This paper describes a nondestructive approach and all required signal processing steps to characterize the thin inner layers and also to improve the imaging speed and the signal to noise ratio. The algorithm was developed by using graphics processing unit (GPU) with computer unified device architecture (CUDA). This GPU-accelerated white light interferometry technique nondestructively assesses the samples and has high imaging speed advantage, overcoming the bottlenecks in PET performs quality control.

  18. Using a Novel Optical Sensor to Characterize Methane Ebullition Processes

    NASA Astrophysics Data System (ADS)

    Delwiche, K.; Hemond, H.; Senft-Grupp, S.

    2015-12-01

    We have built a novel bubble size sensor that is rugged, economical to build, and capable of accurately measuring methane bubble sizes in aquatic environments over long deployment periods. Accurate knowledge of methane bubble size is important to calculating atmospheric methane emissions from in-land waters. By routing bubbles past pairs of optical detectors, the sensor accurately measures bubbles sizes for bubbles between 0.01 mL and 1 mL, with slightly reduced accuracy for bubbles from 1 mL to 1.5 mL. The sensor can handle flow rates up to approximately 3 bubbles per second. Optional sensor attachments include a gas collection chamber for methane sampling and volume verification, and a detachable extension funnel to customize the quantity of intercepted bubbles. Additional features include a data-cable running from the deployed sensor to a custom surface buoy, allowing us to download data without disturbing on-going bubble measurements. We have successfully deployed numerous sensors in Upper Mystic Lake at depths down to 18 m, 1 m above the sediment. The resulting data gives us bubble size distributions and the precise timing of bubbling events over a period of several months. In addition to allowing us to characterize typical bubble size distributions, this data allows us to draw important conclusions about temporal variations in bubble sizes, as well as bubble dissolution rates within the water column.

  19. Characterization of Damage Progression in SCS-6/timetal 21S (0)4 Under Thermomechanical Fatigue Loadings

    NASA Technical Reports Server (NTRS)

    Castelli, Michael G.

    1994-01-01

    A detailed experimental investigation was performed at a single maximum cyclic stress (sigma max) level to physically characterize the progression of thermomechanical fatigue (lW) damage in continuously reinforced (0 deg) SCS-6/Timetal 21S, a titanium matrix composite. In-phase (IP) and out of-phase (OP) loadings were investigated at sigma max = 1000 MPa with a temperature cycle from 150 to 6500 C. Damage progression, in terms of macroscopic property degradation, was experimentally quantified through an advanced TMF test methodology which incorporates explicit measurements of the isothermal static moduli at the TMF temperature extremes and the coefficient of thermal expansion (CTE) as functions of the TMF cycles. Detailed characterization of the physical damage progression at the microstructural level was performed by interrupting multiple TMF tests at various stages of mechanical property degradation and analyzing the microstructure through extensive destructive metallography. Further, the extent of damage was also quantified through residual static strength measurements. Results indicated that damage initiation occurred very early in cyclic life (N less than 0.1Nf) for both the IP and OP TMF loadings. IP TMF damage was found to be dominated by fiber breakage with a physical damage progression in the microstructure which was difficult to quantify. OP TMF loadings produced matrix cracking exclusively associated with surface initiations. Here, damage progression was easily distinguished in terms of both the number of cracks and their relative inward progressions toward the outer fiber rows with increased cycling. The point at which the leading cracks reached the outer fiber rows (when localized fiber/matrix de-bonding and matrix crack bridging occurred) appeared to be reflected in the macroscopic property degradation curves.

  20. Synthesis and characterization of a family of nonlinear optical materials

    NASA Astrophysics Data System (ADS)

    Brott, Lawrence Langenbach

    The development of nonlinear optical (NLO) materials represents an exciting field with applications in areas such as optical signal processing and coherent laser light generation. Second-order NLO chromophore containing materials are being used as frequency doublers or electro-optical modulators while third order NLO chromophores are being designed with large two-photon absorption coefficients for upconverted lasing and imaging applications. This dissertation describes the synthesis and characterization of a group of NLO chromophores containing aromatic heterocyclic rings as π-electron donors, acceptors, and bridging groups. Thiophene, 3,4- ethylenedioxythiophene (EDOT), and diphenyl amine were used here as the electron donor groups while pyridine was used as the electron acceptor. Fluorene ring units were incorporated as aromatic π-electron bridging groups with n-decyl or ethyl chains attached at the C-9 position of the fluorene in order to promote solubility in common organic solvents. One asymmetrical chromophore was made via a three step technique in which a thiophene- and pyridine-propargyl amine reacted with a 2,7-(bisallylbromide)fluorene to form a salt. The bonds underwent a Stevens rearrangement after the addition of a base and finally were thermally cyclized to create a new phenyl ring. Consequently, a new chromophore was made resulting in a molecule with a thiophene and pyridine group separated by four phenyl rings. Other chromophores were made with carbon-carbon bond formation via a Stille coupling process. Thiophene, EDOT, and pyridine rings were functionalized with tributyltin groups, and the resulting molecules coupled with halogenated di-n-decyl-fluorenes. Two asymmetrical chromophores were made using a thiophene and pyridine as the π-electron donor and acceptor rings, respectively, and either one or two fluorene groups as the π-electron bridge. Three symmetrical chromophores were also made in the same manner to yield molecules with thiophene

  1. Surface characterization based on optical phase shifting interferometry

    DOEpatents

    Mello, Michael , Rosakis; Ares J.

    2011-08-02

    Apparatus, techniques and systems for implementing an optical interferometer to measure surfaces, including mapping of instantaneous curvature or in-plane and out-of-plane displacement field gradients of a sample surface based on obtaining and processing four optical interferograms from a common optical reflected beam from the sample surface that are relatively separated in phase by .pi./2.

  2. Continuous-wave laser damage of uniform and nanolaminate hafnia and titania optical coatings.

    PubMed

    Taylor, Lucas N; Brown, Andrew K; Pung, Aaron J; Johnson, Eric G; Talghader, Joseph J

    2013-11-01

    The laser-damage thresholds of single material and nanolaminate thin films were compared under continuous-wave (CW) illumination conditions. Nanolaminate films consist of uniform material interrupted by the periodic insertion of one or more atomic layers of an alternative material. Hafnia and titania were used as the base materials, and the films were deposited using atomic-layer deposition. The nanolaminates were less polycrystalline than the uniform films, as quantified using x-ray diffraction. It was found that the nanolaminate films had reduced laser-damage thresholds on smooth and patterned substrates as compared to uniform single-material films. This behavior is unusual as prior art indicates that amorphous (less polycrystalline) materials have higher laser-damage thresholds under short-pulse excitation. It is speculated that this may indicate that local thermal conduction affects breakdown more strongly under CW excitation than the dielectric properties that are important for short-pulse excitation. PMID:24177076

  3. Improved laser damage threshold performance of calcium fluoride optical surfaces via Accelerated Neutral Atom Beam (ANAB) processing

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, S.; Walsh, M.; Svrluga, R.; Thomas, M.

    2015-11-01

    Optics are not keeping up with the pace of laser advancements. The laser industry is rapidly increasing its power capabilities and reducing wavelengths which have exposed the optics as a weak link in lifetime failures for these advanced systems. Nanometer sized surface defects (scratches, pits, bumps and residual particles) on the surface of optics are a significant limiting factor to high end performance. Angstrom level smoothing of materials such as calcium fluoride, spinel, magnesium fluoride, zinc sulfide, LBO and others presents a unique challenge for traditional polishing techniques. Exogenesis Corporation, using its new and proprietary Accelerated Neutral Atom Beam (ANAB) technology, is able to remove nano-scale surface damage and particle contamination leaving many material surfaces with roughness typically around one Angstrom. This surface defect mitigation via ANAB processing can be shown to increase performance properties of high intensity optical materials. This paper describes the ANAB technology and summarizes smoothing results for calcium fluoride laser windows. It further correlates laser damage threshold improvements with the smoothing produced by ANAB surface treatment. All ANAB processing was performed at Exogenesis Corporation using an nAccel100TM Accelerated Particle Beam processing tool. All surface measurement data for the paper was produced via AFM analysis on a Park Model XE70 AFM, and all laser damage testing was performed at Spica Technologies, Inc. Exogenesis Corporation's ANAB processing technology is a new and unique surface modification technique that has demonstrated to be highly effective at correcting nano-scale surface defects. ANAB is a non-contact vacuum process comprised of an intense beam of accelerated, electrically neutral gas atoms with average energies of a few tens of electron volts. The ANAB process does not apply mechanical forces associated with traditional polishing techniques. ANAB efficiently removes surface

  4. A new characterization approach for studying relationships between microstructure and creep damage mechanisms of uranium dioxide

    NASA Astrophysics Data System (ADS)

    Iltis, X.; Ben Saada, M.; Mansour, H.; Gey, N.; Hazotte, A.; Maloufi, N.

    2016-06-01

    Four batches of UO2 pellets were studied comparatively, before and after creep tests, to evaluate a characterization methodology aimed to determine the links between microstructure and damage mechanisms induced by compressive creep of uranium dioxide at 1500 °C. They were observed by means of scanning electron microscopy (SEM) coupled with image analysis, to quantify their fabrication porosity and the occurrence of inter-granular cavities after creep, and electron back scattered diffraction (EBSD), especially to characterize sub-structures development associated with plastic deformation. Electron channeling contrast imaging (ECCI) was also applied to evidence dislocations, at an exploratory stage, on one of the deformed pellets. This approach helped to identify and quantify microstructural differences between batches. Their as-fabricated microstructures differed in terms of grain size and fabrication porosity distribution. The pellets which had the lowest strain rates were those with the largest number of intra-granular pores, regardless of their grain size. They also exhibited less numerous sub-boundaries within the grains. These first results clearly illustrate the benefit of systematic examinations of crept UO2 pellets at a mesoscopic scale, by SEM and EBSD, to study their deformation process. In addition, ECCI appears as a powerful tool to evidence local dislocations arrangements, in bulk samples. Even if the sampling was limited, the results of this study also tend to indicate that the intra-granular pores population, resulting from the manufacturing of the samples by powder metallurgy, could have a significant influence on the UO2 viscoplastic deformation mechanisms.

  5. A new characterization approach for studying relationships between microstructure and creep damage mechanisms of uranium dioxide

    NASA Astrophysics Data System (ADS)

    Iltis, X.; Ben Saada, M.; Mansour, H.; Gey, N.; Hazotte, A.; Maloufi, N.

    2016-06-01

    Four batches of UO2 pellets were studied comparatively, before and after creep tests, to evaluate a characterization methodology aimed to determine the links between microstructure and damage mechanisms induced by compressive creep of uranium dioxide at 1500 °C. They were observed by means of scanning electron microscopy (SEM) coupled with image analysis, to quantify their fabrication porosity and the occurrence of inter-granular cavities after creep, and electron back scattered diffraction (EBSD), especially to characterize sub-structures development associated with plastic deformation. Electron channeling contrast imaging (ECCI) was also applied to evidence dislocations, at an exploratory stage, on one of the deformed pellets. This approach helped to identify and quantify microstructural differences between batches. Their as-fabricated microstructures differed in terms of grain size and fabrication porosity distribution. The pellets which had the lowest strain rates were those with the largest number of intra-granular pores, regardless of their grain size. They also exhibited less numerous sub-boundaries within the grains. These first results clearly illustrate the benefit of systematic examinations of crept UO2 pellets at a mesoscopic scale, by SEM and EBSD, to study their deformation process. In addition, ECCI appears as a powerful tool to evidence local dislocations arrangements, in bulk samples. Even if the sampling was limited, the results of this study also tend to indicate that the intra-granular pores population, resulting from the manufacturing of the samples by powder metallurgy, could have a significant influence on the UO2 viscoplastic deformation mechanisms.

  6. Rapid, Nonmechanical, Damage-Free Figuring Of Optical Surfaces Using Plasma-Assisted Chemical Etching (PACE): Part I Experimental Results

    NASA Astrophysics Data System (ADS)

    Bollinger, L. D.; Zarowin, Charles B.

    1989-01-01

    We present experimental results of an ongoing investigation demonstrating that Plasma Assisted Chemical Etching (PACE) can rapidly and controllably figure and smooth optical surfaces without mechanical contact; thus, removing the constraints on the design of optical elements imposed by mechanical processes, and, allowing higher quality optical surfaces. This process employs a plasma etch process originally developed to pattern micro-electronic circuits by etching through a relatively non-erodable lithographically patterned mask. The PACE process shapes the optical surface by removing material in a small area under a confined reactive gas plasma moved over the surface. Rates of removal as high as 10 m per minute are obtainable with accurate control. The removal footprint can be varied during the process. PACE inherently smooths or polishes while removing material, exposing a virgin surface free of process generated contamination and subsurface damage. Although other materials can also be figured by a PACE process, for this study, apparatus and processes were developed to explore the figuring of fused silica. Results will be shown demonstrating: repeatability and control of removal rate and footprint; predictability of material removal with plasma "tool" motion; and smoothing.

  7. Mass spectrometer for quantification and characterization of DNA damage in mammalian and human systems. Final report

    SciTech Connect

    1997-12-31

    The instrument grant was used to purchase a Finnigan TSQ 7000 tandem quadruple mass spectrometer with electrospray and atmospheric-pressure chemical-ionization ion sources for the amount of the grant, $371,857. MIT contributed $50,000 in refurbishing costs for the laboratory in which the instrument is used. This mass spectrometer has been in operation since July, 1995 in professor Steven Tannenbaum`s Laboratory in the MIT Division of Toxicology, under the direct supervision of Dr. John S. Wishnok. Its current location is in MIT Building 56, room 747. It is in good operating condition, and is being actively used. Since the original purchase, the instrument has been upgraded by the addition of a (1) dedicated high-performance liquid chromatograph with an autosampler and (2) a nanoelectrospray ion source. The instrument has been used in a number of research projects including the identification of proteins and oligonucleotides, identification of PAH-DNA and PAH-protein adducts, quantitation of food-related carcinogens, and characterization of nitric oxide- and peroxynitrite-related DNA damage.

  8. Synthesis and characterization of gold nanorods and their application for photothermal cell damage

    PubMed Central

    Samim, Mohd; Prashant, CK; Dinda, AK; Maitra, AN; Arora, Indu

    2011-01-01

    Background Gold nanorods show a surface plasmon resonance (SPR) band at the near infra-red (NIR) region which enables them to produce heat on irradiation with a NIR laser. As a result of this, gold nanorods have the potential to be used as thermal therapeutic agents for selective damage to cancer cells, bacterial cells, viruses, and DNA. Methods Gold nanorods with an aspect ratio of approximately 5 were prepared by exploiting the normal micellar route of a water/dioctyl sulfosuccinate (Aerosol-T)/hexane system. The shape and size of the gold nanorods were characterized by surface plasmon bands at 520 nm and 980 nm, and by atomic force microscopy and transmission electron microscopy. Results The length of the gold nanorods was 100 nm and their diameter was 20 nm. X-ray diffraction analysis demonstrated that the gold nanorods formed were metallic in nature. The gold nanorods showed good photothermolysis activity. Conclusion Gold nanorods injected subcutaneously and irradiated with 980 nm laser caused injury to rat tissue, demonstrating that gold nanorods may be used to kill cancerous cells in tumor tissue. PMID:22114472

  9. The simultaneous enhancement of photorefraction and optical damage resistance in MgO and Bi2O3 co-doped LiNbO3 crystals.

    PubMed

    Zheng, Dahuai; Kong, Yongfa; Liu, Shiguo; Chen, Muling; Chen, Shaolin; Zhang, Ling; Rupp, Romano; Xu, Jingjun

    2016-01-01

    For a long time that optical damage was renamed as photorefraction, here we find that the optical damage resistance and photorefraction can be simultaneously enhanced in MgO and Bi2O3 co-doped LiNbO3 (LN:Bi,Mg). The photorefractive response time of LN:Bi,Mg was shortened to 170 ms while the photorefractive sensitivity reached up to 21 cm(2)/J. Meanwhile, LN:Bi,Mg crystals could withstand a light intensity higher than 10(6)  W/cm(2) without apparent optical damage. Our experimental results indicate that photorefraction doesn't equal to optical damage. The underground mechanism was analyzed and attributed to that diffusion dominates the transport process of charge carriers, that is to say photorefraction causes only slight optical damage under diffusion mechanism, which is very important for the practical applications of photorefractive crystals, such as in holographic storage, integrated optics and 3D display. PMID:26837261

  10. The simultaneous enhancement of photorefraction and optical damage resistance in MgO and Bi2O3 co-doped LiNbO3 crystals

    PubMed Central

    Zheng, Dahuai; Kong, Yongfa; Liu, Shiguo; Chen, Muling; Chen, Shaolin; Zhang, Ling; Rupp, Romano; Xu, Jingjun

    2016-01-01

    For a long time that optical damage was renamed as photorefraction, here we find that the optical damage resistance and photorefraction can be simultaneously enhanced in MgO and Bi2O3 co-doped LiNbO3 (LN:Bi,Mg). The photorefractive response time of LN:Bi,Mg was shortened to 170 ms while the photorefractive sensitivity reached up to 21 cm2/J. Meanwhile, LN:Bi,Mg crystals could withstand a light intensity higher than 106  W/cm2 without apparent optical damage. Our experimental results indicate that photorefraction doesn’t equal to optical damage. The underground mechanism was analyzed and attributed to that diffusion dominates the transport process of charge carriers, that is to say photorefraction causes only slight optical damage under diffusion mechanism, which is very important for the practical applications of photorefractive crystals, such as in holographic storage, integrated optics and 3D display. PMID:26837261

  11. Laser induced damage characteristics of fused silica optics treated by wet chemical processes

    NASA Astrophysics Data System (ADS)

    Ye, Hui; Li, Yaguo; Yuan, Zhigang; Wang, Jian; Yang, Wei; Xu, Qiao

    2015-12-01

    Laser damage to fused silica continues a main issue of high-power/energy laser systems. HF-based etching technique is known to mitigate laser damage initiation and growth under UV laser illumination. The responses of material surface properties, especially surface damage characteristics to various etching parameters are questioned in the article. Fused silica was submerged into HF-based etchants (HF, NH4F:HF, HF:HNO3 with diverse concentrations) in an attempt to improve its laser-induced damage threshold (LIDT). The results have evidenced that the LIDT relies on, to a greater degree, the etched thickness and the etchant composition. The secondary ion mass spectrometer (SIMS) testing was aimed at relating the LIDT to certain metallic contaminant; however, the LIDT exhibits weak direct correlation with Ce, La, Ca, Fe contaminants. The surfaces with the highest LIDT are, more often than not, such that the surface roughness is <10 nm RMS and few metallic impurities are present. In addition, we tried to link the LIDT to the hardness and Young's modulus of fused silica, but no testing data show that there exists direct dependence of the LIDT on hardness and Young's modulus, which are actually independent of the removed thickness.

  12. Evaluation of visual and optical sorting of Fusarium damaged kernels in winter wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fusarium head blight (FHB) of wheat, caused by Fusarium graminearum, often results in shriveled and/or discolored kernels referred to as Fusarium damaged kernels (FDK). Determination of FDK usually is done visually. Visual sorting can be laborious and is subject to inconsistencies resulting from v...

  13. Femtosecond laser written optical waveguides in z-cut MgO:LiNbO3 crystal: Fabrication and optical damage investigation

    NASA Astrophysics Data System (ADS)

    Lv, Jinman; Cheng, Yazhou; Lu, Qingming; Vázquez de Aldana, Javier R.; Hao, Xiaotao; Chen, Feng

    2016-07-01

    We report on the fabrication of the dual-line waveguides and cladding waveguide in z-cut MgO:LiNbO3 crystal by femtosecond laser inscription. Due to the diverse modification of refractive index along TE/TM polarization induced by femtosecond laser pulses, the two geometries exhibit different guiding performances: the dual-line waveguides only support extraordinary index polarization, whilst the depressed cladding waveguide supports guidance along both extraordinary and ordinary index polarizations. The measured optical damage of these waveguides at the wavelength of 532 nm is higher than that of the previously reported ion-implanted waveguides in Zr-doped LiNbO3. The propagation loss of depressed cladding waveguide is measured as low as 0.94 dB/cm at 632.8 nm wavelength. It is found that the optical damage threshold (∼105 W/cm2) of the dual-line waveguide is one order of magnitude higher than that of the cladding waveguide (∼104 W/cm2).

  14. Optical Characterization and Applications of Single Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Strano, Michael S.

    2005-03-01

    Recent advances in the dispersion and separation of single walled carbon nanotubes have led to new methods of optical characterization and some novel applications. We find that Raman spectroscopy can be used to probe the aggregation state of single-walled carbon nanotubes in solution or as solids with a range of varying morphologies. Carbon nanotubes experience an orthogonal electronic dispersion when in electrical contact that broadens (from 40 meV to roughly 80 meV) and shifts the interband transition to lower energy (by 60 meV). We show that the magnitude of this shift is dependent on the extent of bundle organization and the inter-nanotube contact area. In the Raman spectrum, aggregation shifts the effective excitation profile and causes peaks to increase or decrease, depending on where the transition lies, relative to the excitation wavelength. The findings are particularly relevant for evaluating nanotube separation processes, where relative peak changes in the Raman spectrum can be confused for selective enrichment. We have also used gel electrophoresis and column chromatography conducted on individually dispersed, ultrasonicated single-walled carbon nanotubes to yield simultaneous separation by tube length and diameter. Electroelution after electrophoresis is shown to produce highly resolved fractions of nanotubes with average lengths between 92 and 435 nm. Separation by diameter is concomitant with length fractionation, and nanotubes that have been cut shortest also possess the greatest relative enrichments of large-diameter species. The relative quantum yield decreases nonlinearly as the nanotube length becomes shorter. These findings enable new applications of nanotubes as sensors and biomarkers. Particularly, molecular detection using near infrared (n-IR) light between 0.9 and 1.3 eV has important biomedical applications because of greater tissue penetration and reduced auto-fluorescent background in thick tissue or whole blood media. Carbon nanotubes

  15. Characterization of Magneto-Optical Media and Systems

    NASA Astrophysics Data System (ADS)

    Bernacki, Bruce Edward

    This dissertation is concerned with the characterization of both the magneto-optic (MO) media and optical system used in MO recording. Amorphous rare earth-transition metal (RE-TM) thin films give rise to magnetic domain walls that are not smooth, but possess varying degrees of jaggedness. A figure-of-merit for domain wall jaggedness could be used to rank films with respect to their suitability for use in MO recording, since domain wall jaggedness has been shown to increase readout noise. Using a specially-constructed static tester, the measured fractal dimension of MO domain walls provides this figure of merit. The basic theory of fractal structures, two measurement techniques, and data from MO samples is presented. At the system level, accurate focusing and tracking is required to reliably and repeatedly write and read data on the media, while track position and focus are maintained. Three focusing and tracking methods are analyzed using scalar diffraction theory, including the effects of residual aberrations and misalignments on their performance. Feedthrough, the false focus error signal due to track crossing in pre-grooved media is also examined and its origin in the astigmatic method is compared with the cause of feedthrough in the obscuration method. The performance of the double astigmatic method, a novel differential method that eliminates feedthrough caused by astigmatism is analyzed. Birefringence of the polycarbonate disk substrate affects tracking and data readout. The focus offset between the position for the best tracking error signal, and that for maximum data readout is shown to be caused by birefringence-induced astigmatism. The effects reducing the track pitch, proper choice of groove depth and pre-format mark depth and their effect on the track crossing signal are investigated. An experimental static focusing/tracking testbed is described along with example data showing the dependence of the tracking error signal on track pitch, objective

  16. Characterization of the interactions of PARP-1 with UV-damaged DNA in vivo and in vitro.

    PubMed

    Purohit, Nupur K; Robu, Mihaela; Shah, Rashmi G; Geacintov, Nicholas E; Shah, Girish M

    2016-01-01

    The existing methodologies for studying robust responses of poly (ADP-ribose) polymerase-1 (PARP-1) to DNA damage with strand breaks are often not suitable for examining its subtle responses to altered DNA without strand breaks, such as UV-damaged DNA. Here we describe two novel assays with which we characterized the interaction of PARP-1 with UV-damaged DNA in vivo and in vitro. Using an in situ fractionation technique to selectively remove free PARP-1 while retaining the DNA-bound PARP-1, we demonstrate a direct recruitment of the endogenous or exogenous PARP-1 to the UV-lesion site in vivo after local irradiation. In addition, using the model oligonucleotides with single UV lesion surrounded by multiple restriction enzyme sites, we demonstrate in vitro that DDB2 and PARP-1 can simultaneously bind to UV-damaged DNA and that PARP-1 casts a bilateral asymmetric footprint from -12 to +9 nucleotides on either side of the UV-lesion. These techniques will permit characterization of different roles of PARP-1 in the repair of UV-damaged DNA and also allow the study of normal housekeeping roles of PARP-1 with undamaged DNA. PMID:26753915

  17. Characterization of the interactions of PARP-1 with UV-damaged DNA in vivo and in vitro

    PubMed Central

    Purohit, Nupur K.; Robu, Mihaela; Shah, Rashmi G.; Geacintov, Nicholas E.; Shah, Girish M.

    2016-01-01

    The existing methodologies for studying robust responses of poly (ADP-ribose) polymerase-1 (PARP-1) to DNA damage with strand breaks are often not suitable for examining its subtle responses to altered DNA without strand breaks, such as UV-damaged DNA. Here we describe two novel assays with which we characterized the interaction of PARP-1 with UV-damaged DNA in vivo and in vitro. Using an in situ fractionation technique to selectively remove free PARP-1 while retaining the DNA-bound PARP-1, we demonstrate a direct recruitment of the endogenous or exogenous PARP-1 to the UV-lesion site in vivo after local irradiation. In addition, using the model oligonucleotides with single UV lesion surrounded by multiple restriction enzyme sites, we demonstrate in vitro that DDB2 and PARP-1 can simultaneously bind to UV-damaged DNA and that PARP-1 casts a bilateral asymmetric footprint from −12 to +9 nucleotides on either side of the UV-lesion. These techniques will permit characterization of different roles of PARP-1 in the repair of UV-damaged DNA and also allow the study of normal housekeeping roles of PARP-1 with undamaged DNA. PMID:26753915

  18. High precision geometrical characterization and alignment of miniaturized optics

    NASA Astrophysics Data System (ADS)

    Langehanenberg, Patrik; Heinisch, Josef; Dumitrescu, Eugen

    2012-03-01

    Miniaturized optical systems like endoscopy or cell phone lenses systems comprise several optical elements like lenses, doublets and plane optics. To receive a good imaging quality the distances and angles between the different optical elements have to be as accurate as possible. In the first step we will describe how the distances and angles between different elements can be monitored and finally we will describe a technique to actively align small optics (diameter approx. 1mm and smaller) with respect to each other. For the measurement electronic autocollimators combined with white-light-interferometers are used. The electronic autocollimator reveals the exact centration errors between optical elements and the low coherence interferometer reveals the distances between surfaces. The accuracy of the centration error measurement is in the range of 0.1μm and the accuracy of the distance measurement is 1μm. Both methods can be applied to assembled multi-element optics. That means geometrical positions of all single surfaces of the final optical system can be analysed without loss of information. Both measurement techniques complement one another. Once the exact x,y,z - Position of each optical surface and element is known computer controlled actuators will be used to improve the alignment of the optics. For this purpose we use piezo-electric-actuators. This method had been applied to cement e.g. doublets for endoscope optics. In this case the optical axis of one lens has been aligned with respect to the optical axis of a second reference lens. Traditional techniques usually rely on an uncertain mechanical reference.

  19. Experimental characterization of creep damage in a welded steel pipe section using a nonlinear ultrasonic technique

    NASA Astrophysics Data System (ADS)

    Ehrlich, C.; Kim, J.-Y.; Jacobs, L. J.; Qu, J.; Wall, J.

    2012-05-01

    To ensure the long and safe operation of power plants, structural parts must be monitored for damage. In the case of welded steel pipes that maintain high pressures in high temperature environments, a common cause of failure is creep damage. Severe creep damage often occurs in the heat affected zone (HAZ). Previous research has shown that nonlinear acoustic techniques are sensitive to creep damage. This research develops a procedure using longitudinal waves to obtain the nonlinearity parameter on a welded steel pipe in order to detect creep damage. These experiments show higher levels of nonlinearity in the HAZ. Additional measurements on an undamaged, welded sample suggest that the high nonlinearity is due to creep (stresses at a high temperature for extended time) damage and not welding (high temperature only for a short time).

  20. Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, J. A.; Dharmadhikari, A. K.; Kasuba, K. C.; Bharambe, H.; D’Souza, J. S.; Rathod, K. D.; Mathur, D.

    2016-06-01

    We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage.

  1. Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses.

    PubMed

    Dharmadhikari, J A; Dharmadhikari, A K; Kasuba, K C; Bharambe, H; D'Souza, J S; Rathod, K D; Mathur, D

    2016-01-01

    We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage. PMID:27279565

  2. Laser microbeams for DNA damage induction, optical tweezers for the search on blood pressure relaxing drugs: contributions to ageing research

    NASA Astrophysics Data System (ADS)

    Grigaravicius, P.; Monajembashi, S.; Hoffmann, M.; Altenberg, B.; Greulich, K. O.

    2009-08-01

    One essential cause of human ageing is the accumulation of DNA damages during lifetime. Experimental studies require quantitative induction of damages and techniques to visualize the subsequent DNA repair. A new technique, the "immuno fluorescent comet assay", is used to directly visualize DNA damages in the microscope. Using DNA repair proteins fluorescently labeled with green fluorescent protein, it could be shown that the repair of the most dangerous DNA double strand breaks starts with the inaccurate "non homologous end joining" pathway and only after 1 - 1 ½ minutes may switch to the more accurate "homologous recombination repair". One might suggest investigating whether centenarians use "homologous recombination repair" differently from those ageing at earlier years and speculate whether it is possible, for example by nutrition, to shift DNA repair to a better use of the error free pathway and thus promote healthy ageing. As a complementary technique optical tweezers, and particularly its variant "erythrocyte mediated force application", is used to simulate the effects of blood pressure on HUVEC cells representing the inner lining of human blood vessels. Stimulating one cell induces in the whole neighbourhood waves of calcium and nitric oxide, known to relax blood vessels. NIFEDIPINE and AMLODIPINE, both used as drugs in the therapy of high blood pressure, primarily a disease of the elderly, prolong the availability of nitric oxide. This partially explains their mode of action. In contrast, VERAPAMILE, also a blood pressure reducing drug, does not show this effect, indicating that obviously an alternative mechanism must be responsible for vessel relaxation.

  3. Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses

    PubMed Central

    Dharmadhikari, J. A.; Dharmadhikari, A. K.; Kasuba, K. C.; Bharambe, H.; D’Souza, J. S.; Rathod, K. D.; Mathur, D.

    2016-01-01

    We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage. PMID:27279565

  4. Modeling the effect of nanosecond laser conditioning on the femtosecond laser-induced damage of optical films.

    PubMed

    Li, Zehan; Du, Juan; Zhao, Yuanan; Wang, Yueliang; Leng, Yuxin; Shao, Jianda

    2015-06-01

    The effect of nanosecond laser conditioning on the femtosecond laser-induced damage behaviors of Al2O3, HfO2, SiO2 single layers and Al2O3/SiO2 high reflectors (HR) are explored. During femtosecond laser damage test, negative effects on enhancing the femtosecond laser-induced damage threshold (LIDT) of optical films after the nanosecond laser conditioning is found, which is opposite to the LIDT improvement in the nanosecond range. To explain the mechanism after nanosecond laser conditioning, a theoretical model including multiphoton ionization (MPI), avalanche ionization (AI) and decays of electrons with one defect state is built to simulate the evolution of electron density in the conduction band. A permanent mid-gap defect state resulting from the process of laser conditioning is introduced in our model, which is found to contribute seed electrons to conduction band and hence accelerate the final breakdown. Both the experimental result and theoretical calculation agree very well with each other. PMID:26072836

  5. Stability Characterization of Quinazoline Derivative BG1188 by Optical Methods

    NASA Astrophysics Data System (ADS)

    Militaru, Andra; Smarandache, Adriana; Mahamoud, Abdallah; Damian, Victor; Ganea, Paul; Alibert, Sandrine; Pagès, Jean-Marie; Pascu, Mihail-Lucian

    2011-08-01

    3-[2-(dimethylamino)ethyl]-6-nitroquinazolin-4(3H)-one, labeled BG1188, is a new synthesized compound, out of a series of quinazoline derivatives developed to fight the multidrug resistance of antibiotics acquired by bacteria. A characterization of the BG1188 powder was made using FTIR spectra in order to evidence the functional groups in the medicine's molecule. The ultraviolet-visible (UV-Vis) absorption spectra were used to study the stability of the BG1188 solutions in two solvents and at different temperatures. BG1188 concentration in ultrapure water was varied between 2×10-3 M (stock solution) and 10-6 M. The concentration recommended by higher activity on bacteria was 10-3 M. For the same reason, this was the utilized concentration of BG1188 in dimethyl sulfoxide (DMSO). Time stability was characterized by comparing the time evolution of the UV-Vis absorption spectra of the BG1188 solutions in ultrapure de-ionized water or in DMSO. The spectra were recorded daily for about 4 months after the preparation for the BG1188 solutions in ultrapure water. Generally, samples are stable within the experimental errors at concentrations higher than 10-5 M, but the stability time interval may vary from 119 days at 10-4 M to 34 days at 10-5 M. Time evolution of the absorption spectra at 10-3 M in ultrapure water shows reproducibility within the measuring errors (±1.045%) for time intervals up to 1032 hours (more than 40 days) after preparation. On the other hand, BG1188 solutions in DMSO may be considered unstable because the absorption spectra modify in terms of peak shapes and intensities, indicating that the samples exhibit modifications immediately after preparation. Regardless the solvent used, some aggregation phenomena took place and wire-like aggregates were observed in all the solutions with the naked eye. These aggregates were analyzed, tentatively, using optical microscopy and FTIR.

  6. [Characterization of the damage of Spodoptera eridania (Cramer) and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) to structures of cotton plants].

    PubMed

    Santos, Karen B Dos; Meneguim, Ana M; Santos, Walter J Dos; Neves, Pedro M O J; Santos, Rachel B Dos

    2010-01-01

    The cotton plant, Gossypium hirsutum, hosts various pests that damage different structures. Among these pests, Spodoptera cosmioides (Walker) and Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae) are considered important. The objectives of this study were to characterize and to quantify the potential damage of S. eridania and S. cosmioides feeding on different structures of cotton plants. For this purpose, newly-hatched larvae were reared on the following plant parts: leaf and flower bud; leaf and boll; flower bud or boll; and leaf, flower bud and boll. The survival of S. cosmioides and S. eridania was greater than 80% and 70% for larvae fed on cotton plant parts offered separately or together, respectively. One larva of S. eridania damaged 1.7 flower buds, but did not damage bolls, while one larva of S. cosmioides damaged 5.2 flower buds and 3.0 cotton bolls. Spodoptera eridania and S. cosmioides can be considered species with potential to cause economic damage to cotton plants because they can occur throughout cotton developmental stages causing defoliation and losses of reproductive structures. Therefore, the results validate field observations that these two species of Spodoptera are potential pests for cotton. PMID:20878002

  7. Inertial focusing cytometer with integrated optics for particle characterization

    PubMed Central

    Kotz, Kenneth T.; Petrofsky, Anne C.; Haghgooie, Ramin; Granier, Robert; Toner, Mehmet; Tompkins, Ronald G.

    2014-01-01

    Microfluidic inertial focusing has been shown as a simple and effective method to localize cells and particles within a flow cell for interrogation by an external optical system. To enable portable point of care optical cytometry, however, requires a reduction in the complexity of the large optical systems that are used in standard flow cytometers. Here, we present a new design that incorporates optical waveguides and focusing elements with an inertial focusing flow cell to make a compact robust cytometer capable of enumerating and discriminating beads, cells, and platelets. PMID:25346940

  8. Electro-optical and Magneto-optical Sensing Apparatus and Method for Characterizing Free-space Electromagnetic Radiation

    DOEpatents

    Zhang, Xi-Cheng; Riordan, Jenifer Ann; Sun, Feng-Guo

    2000-08-29

    Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric (or magnetic) field and a laser beam in an electro-optic (or magnetic-optic) crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field-optical beam interaction length, thereby making imaging applications practical.

  9. Calculating the shrapnel generation and subsequent damage to first wall and optics components for the National Ignition Facility

    SciTech Connect

    Tokheim, R.E.; Seaman, L.; Cooper, T.; Lew, B.; Curran, D.R.; Sanchez, J.; Anderson, A.; Tobin, M.

    1996-08-06

    The purpose of this work is to computationally assess the threat from shrapnel generation on the National Ignition Facility (NIF) first wall, final optics, and ultimately other target chamber components. Shrapnel is defined as material.that is in a solid, liquid, or clustered-vapor phase with sufficient velocity to become a threat to exposed surfaces as a consequence of its impact. Typical NIF experiments will be of two types, low neutron yield shots in which the capsule is not cryogenically cooled, and high yield shots for which cryogenic cooling of the capsule is required. For non-cryogenic shots, shrapnel would be produced by spaIIing, melting and vaporizing of ``shine shields`` by absorption and shock wave loading following 1-{omega} and 2-{omega} laser radiation. For cryogenic shots, shrapnel would be generated through shock wave splitting, spalling, and droplet formation of the cryogenic tubes following neutron energy deposition. Motion of the shrapnel is determined not only by particle velocities resulting from the neutron deposition, but also by both x-ray and debris loading arising from explosion of the hohlraum. Material responses of different target area components are computed from one- dimensional and two-dimensional stress wave propagation codes. Well developed rate-dependent spall computational models are used for stainless steel spall and splitting,. Severe cell distortion is accounted for in shine-shield and hohlraum-loading computations. Resulting distributions of shrapnel particles are traced to the first wall and optics and damage is estimated for candidate materials. First wall and optical material damage from shrapnel includes crater formation and associated extended cracking.

  10. Interaction of 1.319 μm laser with skin: an optical-thermal-damage model and experimental validation

    NASA Astrophysics Data System (ADS)

    Jiao, Luguang; Yang, Zaifu; Wang, Jiarui

    2014-09-01

    With the widespread use of high-power laser systems operating within the wavelength region of approximately 1.3 to 1.4 μm, it becomes very necessary to refine the laser safety guidelines setting the exposure limits for the eye and skin. In this paper, an optical-thermal-damage model was developed to simulate laser propagation, energy deposition, heat transfer and thermal damage in the skin for 1.319 μm laser irradiation. Meanwhile, an experiment was also conducted in vitro to measure the tempreture history of a porcine skin specimen irradiated by a 1.319 μm laser. Predictions from the model included light distribution in the skin, temperature response and thermal damge level of the tissue. It was shown that the light distribution region was much larger than that of the incident laser at the wavelength of 1.319 μm, and the maximum value of the fluence rate located on the interior region of the skin, not on the surface. By comparing the calculated temperature curve with the experimentally recorded temperautre data, good agreement was shown betweeen them, which validated the numerical model. The model also indicated that the damage integral changed little when the temperature of skin tissue was lower than about 55 °C, after that, the integral increased rapidly and denatunation of the tissue would occur. Based on this model, we can further explore the damage mechanisms and trends for the skin and eye within the wavelength region of 1.3 μm to 1.4 μm, incorporating with in vivo experimental investigations.

  11. Impact of different cleaning processes on the laser damage threshold of antireflection coatings for Z-Backlighter optics at Sandia National Laboratories

    SciTech Connect

    Field, Ella; Bellum, John; Kletecka, Damon

    2014-11-06

    We have examined how different cleaning processes affect the laser-induced damage threshold of antireflection coatings for large dimension, Z-Backlighter laser optics at Sandia National Laboratories. Laser damage thresholds were measured after the coatings were created, and again 4 months later to determine which cleaning processes were most effective. There is a nearly twofold increase in laser-induced damage threshold between the antireflection coatings that were cleaned and those that were not cleaned. Aging of the coatings after 4 months resulted in even higher laser-induced damage thresholds. Also, the laser-induced damage threshold results revealed that every antireflection coating had a high defect density, despite the cleaning process used, which indicates that improvements to either the cleaning or deposition processes should provide even higher laser-induced damage thresholds.

  12. Impact of different cleaning processes on the laser damage threshold of antireflection coatings for Z-Backlighter optics at Sandia National Laboratories

    DOE PAGESBeta

    Field, Ella; Bellum, John; Kletecka, Damon

    2014-11-06

    We have examined how different cleaning processes affect the laser-induced damage threshold of antireflection coatings for large dimension, Z-Backlighter laser optics at Sandia National Laboratories. Laser damage thresholds were measured after the coatings were created, and again 4 months later to determine which cleaning processes were most effective. There is a nearly twofold increase in laser-induced damage threshold between the antireflection coatings that were cleaned and those that were not cleaned. Aging of the coatings after 4 months resulted in even higher laser-induced damage thresholds. Also, the laser-induced damage threshold results revealed that every antireflection coating had a high defectmore » density, despite the cleaning process used, which indicates that improvements to either the cleaning or deposition processes should provide even higher laser-induced damage thresholds.« less

  13. Plume mass flow and optical damage distributions for an MMH/N2O4 RCS thruster. [exhaust plume contamination of spacecraft components

    NASA Technical Reports Server (NTRS)

    Spisz, E. W.; Bowman, R. L.; Jack, J. R.

    1973-01-01

    The data obtained from two recent experiments conducted in a continuing series of experiments at the Lewis Research Center into the contamination characteristics of a 5-pound thrust MMH/N2O4 engine are presented. The primary objectives of these experiments were to establish the angular distribution of condensible exhaust products within the plume and the corresponding optical damage angular distribution of transmitting optical elements attributable to this contaminant. The plume mass flow distribution was measured by five quartz crystal microbalances (QCM's) located at the engine axis evaluation. The fifth QCM was located above the engine and 15 deg behind the nozzle exit plane. The optical damage was determined by ex-situ transmittance measurements for the wavelength range from 0.2 to 0.6 microns on 2.54 cm diameter fused silica discs also located at engine centerline elevation. Both the mass deposition and optical damage angular distributions followed the expected trend of decreasing deposition and damage as the angle between sensor or sample and the nozzle axis increased. A simple plume gas flow equation predicted the deposition distribution reasonably well for angles of up to 55 degrees. The optical damage measurements also indicated significant effects at large angles.

  14. Single crystal growth, structural characterization, thermal and optical properties of a novel organometallic nonlinear optical crystal: MnHg(SCN) 4(C 2H 5NO) 2

    NASA Astrophysics Data System (ADS)

    Wang, X. Q.; Cheng, X. F.; Zhang, S. J.; Xu, D.; Zhang, G. H.; Sun, Z. H.; Yu, F. P.; Liu, X. J.; Liu, W. L.; Chen, C. L.

    2010-02-01

    A novel potentially useful organometallic nonlinear optical crystal, manganese mercury thiocyanate-bis(N-methylformamide), MnHg(SCN) 4(C 2H 5NO) 2 (MMTN) has been prepared, and large highly-optical quality single crystals with dimensions up to 29×28×14 mm 3 have been grown. The structural characterization, thermal and optical properties of the grown crystals are investigated. The growth morphology was obtained by indexing the X-ray powder diffraction data and compared with that deducing from the single crystal structure data using the Bravais-Friedel-Donnay-Harker model. The thermal analysis reveals that MMTN crystal possesses good physicochemical stability. The specific heat of the crystal is 635.1 J mol -1 K -1 at 300 K. The thermal expansion coefficient along the a, b, and c axis is α1=6.18×10 -5 K -1, α2=3.91×10 -5 K -1 and α3=9.53×10 -6 K -1, respectively. The laser damage threshold of MMTN crystal is about 225.7 MW/cm 2 with pulse width of 18 ns at 1064 nm. The powder second harmonic efficiency of the crystal is about 1.1 pm/V and the UV transparency cutoff is 354 nm, which are interpreted on the basis of the crystal structure with the Molecular Orbital theory using a GAUSSIAN03 program.

  15. Characterization of the DNA damage-inducible helicase DinG from Escherichia coli.

    PubMed

    Voloshin, Oleg N; Vanevski, Filip; Khil, Pavel P; Camerini-Otero, R Daniel

    2003-07-25

    The dinG promoter was first isolated in a genetic screen scoring for damage-inducible loci in Escherichia coli (Lewis, L. K., Jenkins, M. E., and Mount, D. W. (1992) J. Bacteriol. 174, 3377-3385). Sequence analysis suggests that the dinG gene encodes a putative helicase related to a group of eukaryotic helicases that includes mammalian XPD (Koonin, E. V. (1993) Nucleic Acids Res. 21, 1497), an enzyme involved in transcription-coupled nucleotide excision repair and basal transcription. We have characterized the dinG gene product from E. coli using genetic and biochemical approaches. Deletion of dinG has no severe phenotype, indicating that it is non-essential for cell viability. Both dinG deletion and over-expression of the DinG protein from a multicopy plasmid result in a slight reduction of UV resistance. DinG, purified as a fusion protein from E. coli cells, behaves as a monomer in solution, as judged from gel filtration experiments. DinG is an ATP-hydrolyzing enzyme; single-stranded (ss) DNA stimulates the ATPase activity 15-fold. Kinetic data yield a Hill coefficient of 1, consistent with one ATP-hydrolyzing site per DinG molecule. DinG possesses a DNA helicase activity; it translocates along ssDNA in a 5' --> 3' direction, as revealed in experiments with substrates containing non-natural 5'-5' and 3'-3' linkages. The ATP-dependent DNA helicase activity of DinG requires divalent cations (Mg2+, Ca2+, and Mn2+) but is not observed in the presence of Zn2+. The DinG helicase does not discriminate between ribonucleotide and deoxyribonucleotide triphosphates, and it unwinds duplex DNA with similar efficiency in the presence of ATP or dATP. We discuss the possible involvement of the DinG helicase in DNA replication and repair processes. PMID:12748189

  16. Characterization of radiation-induced damage in high performance polymers by electron paramagnetic resonance imaging spectroscopy

    NASA Technical Reports Server (NTRS)

    Suleman, Naushadalli K.

    1992-01-01

    The potential for long-term human activity beyond the Earth's protective magnetosphere is limited in part by the lack of detailed information on the effectiveness and performance of existing structural materials to shield the crew and spacecraft from highly penetrating space radiations. The two radiations of greatest concern are high energy protons emitted during solar flares and galactic cosmic rays which are energetic ions ranging from protons to highly oxidized iron. Although the interactions of such high-energy radiations with matter are not completely understood at this time, the effects of the incident radiation are clearly expected to include the formation of paramagnetic spin centers via ionization and bond-scission reactions in the molecular matrices of structural materials. Since this type of radiation damage is readily characterized by Electron Paramagnetic Resonance (EPR) spectroscopy, the NASA Langley Research Center EPR system was repaired and brought on-line during the 1991 ASEE term. A major goal of the 1992 ASEE term was to adapt the existing core of the LaRC EPR system to meet the requirements for EPR Imaging--a powerful new technique which provides detailed information on the internal structure of materials by mapping the spatial distribution of unpaired spin density in bulk media. Major impetus for this adaptation arises from the fact that information derived from EPRI complements other methods such as scanning electron microscopy which primarily characterize surface phenomena. The modification of the EPR system has been initiated by the construction of specially designed, counterwound Helmholtz coils which will be mounted on the main EPR electromagnet. The specifications of the coils have been set to achieve a static linear magnetic field gradient of 10 gauss/mm/amp along the principal (Z) axis of the Zeeman field. Construction is also in progress of a paramagnetic standard in which the spin distribution is known in all three dimensions. This

  17. Nondestructive evaluation and characterization of damage and repair to continuous-fiber ceramic composite panels.

    SciTech Connect

    Sun, J. G.; Petrak, D. R.; Pillai, T. A. K.; Deemer, C.; Ellingson, W. A.

    1998-04-01

    Continuous fiber ceramic matrix composites are currently being developed for a variety of high-temperature applications. Because of the high costs of making these components, minor damage incurred during manufacturing or operation must be rewired in order to extend the life of the components. In this study, five ceramic-grade Nicalon{trademark} fiber/SiNC-matrix composite panels were intentionally damaged with a pendulum-type impactor during an impact test. The damaged panels were then repaired at Dow Corning Corporation. Three nondestructive evaluation (NDE) methods were used to study the characteristics of the panels after the damage and again after the panels were repaired. The NDE methods were X-ray radiography, infrared thermal imaging, and air-coupled ultrasound. The results showed that the impact test induced various types of damage in the panels. The NDE data that were obtained by the three NDE methods were correlated with each other.

  18. Characterization of novel microsphere chain fiber optic tips for potential use in ophthalmic laser surgery

    NASA Astrophysics Data System (ADS)

    Hutchens, Thomas C.; Darafsheh, Arash; Fardad, Amir; Antoszyk, Andrew N.; Ying, Howard S.; Astratov, Vasily N.; Fried, Nathaniel M.

    2012-06-01

    Ophthalmic surgery may benefit from use of more precise fiber delivery systems during laser surgery. Some current ophthalmic surgical techniques rely on tedious mechanical dissection of tissue layers. In this study, chains of sapphire microspheres integrated into a hollow waveguide distal tip are used for erbium:YAG laser ablation studies in contact mode with ophthalmic tissues, ex vivo. The laser's short optical penetration depth combined with the small spot diameters achieved with this fiber probe may provide more precise tissue removal. One-, three-, and five-microsphere chain structures were characterized, resulting in FWHM diameters of 67, 32, and 30 μm in air, respectively, with beam profiles comparable to simulations. Single Er:YAG pulses of 0.1 mJ and 75-μs duration produced ablation craters with average diameters of 44, 30, and 17 μm and depths of 26, 10, and 8 μm, for one-, three-, and five-sphere structures, respectively. Microsphere chains produced spatial filtering of the multimode Er:YAG laser beam and fiber, providing spot diameters not otherwise available with conventional fiber systems. Because of the extremely shallow treatment depth, compact focused beam, and contact mode operation, this probe may have potential for use in dissecting epiretinal membranes and other ophthalmic tissues without damaging adjacent retinal tissue.

  19. Characterization of the Optical Properties of Normal and Defective Pickling Cucumbers and Whole Pickles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Internal defect in pickling cucumbers can cause bloater damage during brining, which lowers the quality of final pickled products and results in economic loss for the pickle industry. Hence it is important to have an effective optical inspection system for detection and segregation of defective pick...

  20. The collagen structure of equine articular cartilage, characterized using polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Ugryumova, Nadya; Attenburrow, Don P.; Winlove, C. Peter; Matcher, Stephen J.

    2005-08-01

    Optical coherence tomography and polarization-sensitive optical coherence tomography images of equine articular cartilage are presented. Measurements were made on intact joint surfaces. Significant (e.g. × 2) variations in the intrinsic birefringence were found over spatial scales of a few millimetres, even on samples taken from young (18 month) animals that appeared visually homogeneous. A comparison of data obtained on a control tissue (equine flexor tendon) further suggests that significant variations in the orientation of the collagen fibres relative to the plane of the joint surface exist. Images of visually damaged cartilage tissue show characteristic features both in terms of the distribution of optical scatterers and of the birefringent components.