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Sample records for aperture fused silica

  1. 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.

  2. Fabrication of large aperture kinoform phase plates in fused silica for smoothing focal plane intensity profiles

    SciTech Connect

    Rushford, M.; Dixit, S.; Thomas, I.; Perry, M.

    1996-04-26

    We have fabricated large aperture (40-cm) kinoform phase plates for producing super-Gaussian focal plane intensity profiles. The continuous phase screen, designed using a new iterative procedure, was fabricated in fused silica as a 16-level, one-wave deep rewrapped phase profile using a lithographic process and wet etching in buffered hydrofluoric acid. The observed far-field contains 94% of the incident energy inside the desired spot.

  3. In-situ monitoring of surface post-processing in large aperture fused silica optics with Optical Coherence Tomography

    SciTech Connect

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

    2008-02-08

    Optical Coherence Tomography is explored as a method to image laser-damage sites located on the surface of large aperture fused silica optics during post-processing via CO{sub 2} laser ablation. The signal analysis for image acquisition was adapted to meet the sensitivity requirements for this application. A long-working distance geometry was employed to allow imaging through the opposite surface of the 5-cm thick optic. The experimental results demonstrate the potential of OCT for remote monitoring of transparent material processing applications.

  4. Large aperture kinoform phase plates in fused silica for spatial beam smoothing on Nova and the Beamlet Lasers

    SciTech Connect

    Rushford, M.C.; Dixit, S.N.; Thomas, I.M.; Martin, A.M.; Perry, M.D.

    1997-03-01

    It is now widely recognized that spatial beam smoothing (homogenization) is essential in coupling the laser energy to the inertial confinement fusion (ICF) targets. For the indirect drive approach to ICF, it is desirable to distribute the laser energy into a uniformly speckled profile that has a flat-top super-Gaussian envelope (8th power or higher) and contains greater than 95% of the energy inside the super-Gaussian profile. Spatial smoothing is easily achieved by introducing a binary random phase plate (RPP) in the beam. This produces a homogenized far-field pattern which consists of an overall envelope function determined by the RPP element superimposed with a fine scale speckle pattern arising due to the interference among the various RPP elements. Although easy to fabricate and currently in routine use in many fusion laboratories, the binary RPPs do not meet the ICF requirements stated above since the far-field intensity profile is restricted to essentially an Airy function containing only 84% (an upper limit) of the energy inside the central spot. Approaches using lenslet arrays (refractive or diffractive) have limited use since they operate in the quasi-far-field and have a short depth of focus. The limitations of the RPPs can be overcome by relaxing the binary phase constraint. We have recently presented 5 continuously varying phase screens for tailoring the focal plane irradiance profiles. Called kinoform phase plates (KPPs), these phase screens offer complete flexibility in tailoring the focal plane envelope and, at the same time, increasing the energy efficiency inside the focal spot. In this paper we discuss the design and fabrication of such kinoform phase plates in fused silica for spatial beam smoothing on the Nova and the Beamlet lasers. Since the phase plates are used at the end of the laser chain, KPPs on Nova and Beamlet have to be fabricated on large aperture optics (65-cm diameter and 40-cm square substrates respectively). The following

  5. Contributions of kinematics and viscoelastic lap deformation on the suface figure during full aperture polishing of fused silica

    SciTech Connect

    Suratwala, T I; Steele, R A; Feit, M D

    2007-10-09

    A typical optical fabrication process involves a series of basic process steps including: (1) shaping, (2) grinding, (3) polishing, and sometimes (4) sub-aperture tool finishing. With significant innovation and development over the years in both the front end (shaping using CNC machines) and the back end (sup-aperture tool polishing), these processes have become much more deterministic. However, the intermediate stages (full aperture grinding/polishing) in the process, which can be very time consuming, still have much reliance on the optician's insight to get to the desired surface figure. Such processes are not presently very deterministic (i.e. require multiple iterations to get desired figure). The ability to deterministically finish an optical surface using a full aperture grinding/polishing will aid optical glass fabricators to achieve desired figure in a more repeatable, less iterative, and more economical manner. Developing a scientific understanding of the material removal rate is a critical step in accomplishing this. In the present study, the surface figure and material removal rate of a fused silica workpiece is measured as a function of polishing time using Ceria based slurry on a polyurethane pad or pitch lap under a variety of kinematic conditions (motion of the workpiece and lap) and loading configurations. The measured results have been applied to expand the Preston model of material removal (utilizing chemical, mechanical and tribological effects). The results show that under uniform loading, the surface figure is dominated by kinematics which can be predicted by calculating the relative velocity (between the workpiece and the lap) with time and position on the workpiece. However, in the case where the kinematics predict a time-averaged removal function over the workpiece that is uniform, we find experimentally that the surface deviates significantly from uniform removal. We show that this non-uniform removal is caused by the non-uniform stress

  6. Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings

    NASA Astrophysics Data System (ADS)

    Smith, Douglas J.; McCullough, Mike; Smith, Claire; Mikami, Takuya; Jitsuno, Takahisa

    2008-10-01

    Large aperture laser pulse compressor designs use several diffraction gratings in series and sometimes tiled together to compress an amplified 1 to 10 ns pulse to 0.1 to 10 ps. The wavefront of the compressed pulse must be well controlled to allow focusing to a small spot on a target. Traditionally, multilayer dielectric gratings (MLDG) have been fabricated onto high thermal expansion substrates such as BK7 glass to prevent crazing and excessive bending due to tensile coating stress when operated in high vacuum. However, the high CTE of the BK7 can cause wavefront distortion and changes in the period of the grating. This work uses ion-assisted deposition of HfO2/SiO2 films to increase the compressive stress in MLD layers to allow use of silica substrates in the compressor vacuum environment. Stress, coating uniformity, and damage results are reported. The process was scaled to full size (91cm × 42cm) MLD gratings for use in the Osaka University LFEX laser system. Diffracted wavefront results from the full scale gratings is presented.

  7. Fused Silica and Other Transparent Window Materials

    NASA Technical Reports Server (NTRS)

    Salem, Jon

    2016-01-01

    Several transparent ceramics, such as spinel and AlONs are now being produced in sufficient large areas to be used in space craft window applications. The work horse transparent material for space missions from Apollo to the International Space Station has been fused silica due in part to its low coefficient of expansion and optical quality. Despite its successful use, fused silica exhibits anomalies in its crack growth behavior, depending on environmental preconditioning and surface damage. This presentation will compare recent optical ceramics to fused silica and discuss sources of variation in slow crack growth behavior.

  8. Fluorine-Based DRIE of Fused Silica

    NASA Technical Reports Server (NTRS)

    Yee, Karl; Shcheglov, Kirill; Li, Jian; Choi, Daniel

    2007-01-01

    A process of deep reactive-ion etching (DRIE) using a fluorine-based gas mixture enhanced by induction-coupled plasma (ICP) has been demonstrated to be effective in forming high-aspect-ratio three-dimensional patterns in fused silica. The patterns are defined in part by an etch mask in the form of a thick, high-quality aluminum film. The process was developed to satisfy a need to fabricate high-aspect-ratio fused-silica resonators for vibratory microgyroscopes, and could be used to satisfy similar requirements for fabricating other fused-silica components.

  9. Inverse melting in stressed fused silica

    NASA Astrophysics Data System (ADS)

    Bouchut, Philippe

    2012-12-01

    The emissive properties of proton implanted fused silica surfaces have been studied by laser beam annealing. When submitted to a high thermal step from a focused CO2 laser, an intense near infra-red thermoluminescence peak rises at a heating rate threshold. The in plane tensile stress relaxes and silica melts. We show that in the irreversible inverse melting of stressed fused silica, the protons exo-diffuse through internal modes coupling. The heat and mass transfer is one entropy flux whose dynamics are regulated by the mass transport. Inverse melting is the thermodynamic process that initiates the glass transition when heating.

  10. Fused silica windows for solar receiver applications

    NASA Astrophysics Data System (ADS)

    Hertel, Johannes; Uhlig, Ralf; Söhn, Matthias; Schenk, Christian; Helsch, Gundula; Bornhöft, Hansjörg

    2016-05-01

    A comprehensive study of optical and mechanical properties of quartz glass (fused silica) with regard to application in high temperature solar receivers is presented. The dependence of rupture strength on different surface conditions as well as high temperature is analyzed, focussing particularly on damage by devitrification and sandblasting. The influence of typical types of contamination in combination with thermal cycling on the optical properties of fused silica is determined. Cleaning methods are compared regarding effectiveness on contamination-induced degradation for samples with and without antireflective coating. The FEM-aided design of different types of receiver windows and their support structure is presented. A large-scale production process has been developed for producing fused silica dome shaped windows (pressurized window) up to a diameter of 816 mm. Prototypes were successfully pressure-tested in a test bench and certified according to the European Pressure Vessel Directive.

  11. Quartz/fused silica chip carriers

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The primary objective of this research and development effort was to develop monolithic microwave integrated circuit (MMIC) packaging which will operate efficiently at millimeter-wave frequencies. The packages incorporated fused silica as the substrate material which was selected due to its favorable electrical properties and potential performance improvement over more conventional materials for Ka-band operation. The first step towards meeting this objective is to develop a package that meets standard mechanical and thermal requirements using fused silica and to be compatible with semiconductor devices operating up to at least 44 GHz. The second step is to modify the package design and add multilayer and multicavity capacity to allow for application specific integrated circuits (ASIC's) to control multiple phase shifters. The final step is to adapt the package design to a phased array module with integral radiating elements. The first task was a continuation of the SBIR Phase 1 work. Phase 1 identified fused silica as a viable substrate material by demonstrating various plating, machining, and adhesion properties. In Phase 2 Task 1, a package was designed and fabricated to validate these findings. Task 2 was to take the next step in packaging and fabricate a multilayer, multichip module (MCM). This package is the predecessor to the phased array module and demonstrates the ability to via fill, circuit print, laminate, and to form vertical interconnects. The final task was to build a phased array module. The radiating elements were to be incorporated into the package instead of connecting to it with wire or ribbon bonds.

  12. CO2 laser welding fused silica.

    SciTech Connect

    Reed, Scott T.; MacCallum, Danny O'Neill; Knorovsky, Gerald Albert

    2005-08-01

    The feasibility of laser welding of fused silica (aka quartz) has been demonstrated recently by others. An application requiring hermetic sealing of a thin, pressure-bearing quartz diaphragm to a thicker frame led us to explore this technique. We found that laser welding techniques normally used for metallic parts caused scorching and uneven melting. Contrary to standard practices (near focus, high travel speed, high power density), successful welds in fused silica required a broad heat source applied over a large area under a slow rotation to gradually heat the glass through the annealing, softening and finally working temperatures. Furthermore, good mechanical contact between the parts to be joined played an even more important role in this process than in typical metallic joints. A 50 W CO2 laser with 4 f.l. ZnSe2 lens and rotary head was used to weld 0.425 OD, 0.006-0.010 thick, disks to 0.500 OD tubing with 0.125 walls. Several joint geometries and beam orientations were investigated. Temperature profiles were measured and compared to an FEM thermal model. We will discuss the effects of laser power, travel speed, number of passes, joint geometry and part thicknesses on achieving hermeticity and cosmetically-acceptable joints.

  13. Subsurface damage on ground fused silica surfaces

    NASA Astrophysics Data System (ADS)

    Xu, Jiafeng; Xu, Xueke; Gao, Wenlan; Wei, Chaoyang; Yang, Minghong; Shao, Jianda

    2014-08-01

    The low surface laser damage threshold of fused silica components in high power laser systems such as NIF restricts the improvement of the output fluence of those systems. Once damage is initiated and grows under subsequent laser shots, the components will go unusable. Subsurface damage (SSD) introduced during manufacturing has been identified as a main damage initiator. A good knowledge of SSD and how manufacturing influences it is essential to optimize manufacturing processes for damage free optics. Using the magneto-rheological finishing (MRF) wedge technique of better accuracy attributed to a tip, we have characterized the subsurface damage on fused silica optical surfaces ground with loose Al2O3 abrasives of different sizes. Larger abrasives generates longer cracks and the number density of cracks decreases sharply with the depth for each size. Rogue particles account for the occurrence of trailing indent scratches. Addition of rogue abrasives into relatively small base abrasive extends SSD more deeply than that induced by rogue abrasives alone. The linear model, with the proportional coefficient 3.511, fits the relationship between SSD depth and surface roughness (SR) better than the quadratic polynomial one. We believe SSD depth relates to SR more statistically than following some specified physical law. The linear relationship between SSD depth and the abrasive size was also established. The abrasive size turned out not to be as a good indictor of SSD depth as SR.

  14. Note: Discharging fused silica test masses with ionized nitrogen

    NASA Astrophysics Data System (ADS)

    Ugolini, D.; Funk, Q.; Amen, T.

    2011-04-01

    We have developed a technique for discharging fused silica test masses in a gravitational-wave interferometer with nitrogen ionized by an electron beam. The electrons are produced from a heated filament by thermionic emission in a low-pressure region to avoid contamination and burnout. Some electrons then pass through a small aperture and ionize nitrogen in a higher-pressure region, and this ionized gas is pumped across the test mass surface, neutralizing both polarities of charge. The discharge rate varies exponentially with charge density and filament current, quadratically with filament potential, and has an optimal working pressure of ˜8 mT. Adapting the technique to larger test mass chambers is also discussed.

  15. Laser Damage Precursors in Fused Silica

    SciTech Connect

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

    2009-11-11

    There is a longstanding, and largely unexplained, correlation between the laser damage susceptibility of optical components and both the surface quality of the optics, and the presence of near surface fractures in an optic. In the present work, a combination of acid leaching, acid etching, and confocal time resolved photoluminescence (CTP) microscopy has been used to study laser damage initiation at indentation sites. The combination of localized polishing and variations in indentation loads allows one to isolate and characterize the laser damage susceptibility of densified, plastically flowed and fractured fused silica. The present results suggest that: (1) laser damage initiation and growth are strongly correlated with fracture surfaces, while densified and plastically flowed material is relatively benign, and (2) fracture events result in the formation of an electronically defective rich surface layer which promotes energy transfer from the optical beam to the glass matrix.

  16. Coated Fused Silica Fibers for Enhanced Sensitivity Torsion Pendulum

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Horowitz, Jordan; Camp, Jordan

    2007-01-01

    In order to investigate the fundamental thermal noise limit of a torsion pendulum using a fused silica fiber, we systematically measured and modeled the mechanical losses of thin fused silica fibers coated by electrically conductive thin metal films. Our results indicate that it is possible to achieve a thermal noise limit for coated silica lower by a factor between 3 and 9, depending on the silica diameter, compared to the best tungsten fibers available. This will allow a corresponding increase in sensitivity of torsion pendula used for weak force measurements, including the gravitational constant measurement and ground-based force noise testing for the Laser Interferometer Space Antenna (LISA) mission.

  17. Quantification of residual stress from photonic signatures of fused silica

    NASA Astrophysics Data System (ADS)

    Cramer, K. Elliott; Hayward, Maurice; Yost, William T.

    2014-02-01

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 ± 0.54 × 10-12 Pa-1. Fused silica specimens containing impacts artificially made at NASA's Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented.

  18. Reflecting heat shields made of microstructured fused silica

    NASA Technical Reports Server (NTRS)

    Congdon, W. M.

    1975-01-01

    Heat sheidls constructed from selected monodisperse distributions of high-purity fused-silica particles are efficient reflectors of visible and near-UV radiation generated in shock-layer of space probe during atmospheric entry.

  19. Quantification of Residual Stress from Photonic Signatures of Fused Silica

    NASA Technical Reports Server (NTRS)

    Cramer, K. Elliott; Hayward, Maurice; Yost, William E.

    2013-01-01

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 +/- 0.54 x 10(exp -12)/Pa. Fused silica specimens containing impacts artificially made at NASA's Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented. Keywords: Glass, fused silica, photoelasticity, residual stress

  20. HVI Ballistic Limit Characterization of Fused Silica Thermal Panes

    NASA Technical Reports Server (NTRS)

    Miller, J. E.; Bohl, W. D.; Christiansen, E. L.; Davis, B. A.; Deighton, K. D.

    2015-01-01

    Fused silica window systems are used heavily on crewed reentry vehicles, and they are currently being used on the next generation of US crewed spacecraft, Orion. These systems improve crew situational awareness and comfort, as well as, insulating the reentry critical components of a spacecraft against the intense thermal environments of atmospheric reentry. Additionally, these materials are highly exposed to space environment hazards like solid particle impacts. This paper discusses impact studies up to 10 km/s on a fused silica window system proposed for the Orion spacecraft. A ballistic limit equation that describes the threshold of perforation of a fuse silica pane over a broad range of impact velocities, obliquities and projectile materials is discussed here.

  1. Microwave attenuation of multiwalled carbon nanotube-fused silica composites

    SciTech Connect

    Xiang Changshu; Pan Yubai; Liu Xuejian; Sun Xingwei; Shi Xiaomei; Guo Jingkun

    2005-09-19

    Multiwalled carbon nanotubes (MWCNTs) were used to convert radome materials to microwave absorbing materials. Dense MWCNT-fused silica composites were prepared by hot-pressing technique. The composites exhibit high complex permittivities at X-band frequencies, depending on the content of MWCNTs. The value of the loss tangent increases three orders over pure fused silica only by incorporating 2.5 vol % MWCNTs into the composites. The average magnitude of microwave transmission reaches -33 dB at 11-12 GHz in the 10 vol % MWCNT-fused silica composites, which indicates the composites have excellent microwave attenuation properties. The attenuation properties mainly originate from the electric loss of MWCNTs by the motion of conducting electrons.

  2. Thermoluminescence at a heating rate threshold in stressed fused silica.

    PubMed

    Bouchut, Philippe; Milesi, Frédéric; Da Maren, Céline

    2011-12-19

    The emissive properties of proton implanted fused silica surfaces have been studied by laser beam annealing. When submitted to a high thermal step from a focused CO2 laser, an intense near infra-red transient incandescence (TI) peak rises from stressed silica. The TI presents the characteristics of a thermoluminescent (TL) emission that occurs above a thermal rate threshold. We show that TI rises at the stress relaxation. PMID:22274172

  3. Process for manufacturing hollow fused-silica insulator cylinder

    DOEpatents

    Sampayan, Stephen E.; Krogh, Michael L.; Davis, Steven C.; Decker, Derek E.; Rosenblum, Ben Z.; Sanders, David M.; Elizondo-Decanini, Juan M.

    2001-01-01

    A method for building hollow insulator cylinders that can have each end closed off with a high voltage electrode to contain a vacuum. A series of fused-silica round flat plates are fabricated with a large central hole and equal inside and outside diameters. The thickness of each is related to the electron orbit diameter of electrons that escape the material surface, loop, and return back. Electrons in such electron orbits can support avalanche mechanisms that result in surface flashover. For example, the thickness of each of the fused-silica round flat plates is about 0.5 millimeter. In general, the thinner the better. Metal, such as gold, is deposited onto each top and bottom surface of the fused-silica round flat plates using chemical vapor deposition (CVD). Eutectic metals can also be used with one alloy constituent on the top and the other on the bottom. The CVD, or a separate diffusion step, can be used to defuse the deposited metal deep into each fused-silica round flat plate. The conductive layer may also be applied by ion implantation or gas diffusion into the surface. The resulting structure may then be fused together into an insulator stack. The coated plates are aligned and then stacked, head-to-toe. Such stack is heated and pressed together enough to cause the metal interfaces to fuse, e.g., by welding, brazing or eutectic bonding. Such fusing is preferably complete enough to maintain a vacuum within the inner core of the assembled structure. A hollow cylinder structure results that can be used as a core liner in a dielectric wall accelerator and as a vacuum envelope for a vacuum tube device where the voltage gradients exceed 150 kV/cm.

  4. Form control in atmospheric pressure plasma processing of ground fused silica

    NASA Astrophysics Data System (ADS)

    Li, Duo; Wang, Bo; Xin, Qiang; Jin, Huiliang; Wang, Jun; Dong, Wenxia

    2014-08-01

    Atmospheric Pressure Plasma Processing (APPP) using inductively coupled plasma has demonstrated that it can achieve comparable removal rate on the optical surface of fused silica under the atmosphere pressure and has the advantage of inducing no sub-surface damage for its non-contact and chemical etching mechanism. APPP technology is a cost effective way, compared with traditional mechanical polishing, magnetorheological finishing and ion beam figuring. Thus, due to these advantages, this technology is being tested to fabricate large aperture optics of fused silica to help shorten the polishing time in optics fabrication chain. Now our group proposes to use inductively coupled plasma processing technology to fabricate ground surface of fused silica directly after the grinding stage. In this paper, form control method and several processing parameters are investigated to evaluate the removal efficiency and the surface quality, including the robustness of removal function, velocity control mode and tool path strategy. However, because of the high heat flux of inductively coupled plasma, the removal depth with time can be non-linear and the ground surface evolvement will be affected. The heat polishing phenomenon is founded. The value of surface roughness is reduced greatly, which is very helpful to reduce the time of follow-up mechanical polishing. Finally, conformal and deterministic polishing experiments are analyzed and discussed. The form error is less 3%, before and after the APPP, when 10μm depth of uniform removal is achieved on a 60×60mm ground fused silica. Also, a basin feature is fabricated to demonstrate the figuring capability and stability. Thus, APPP is a promising technology in processing the large aperture optics.

  5. Quantification of residual stress from photonic signatures of fused silica

    SciTech Connect

    Cramer, K. Elliott; Yost, William T.; Hayward, Maurice

    2014-02-18

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 ± 0.54 × 10{sup −12} Pa{sup −1}. Fused silica specimens containing impacts artificially made at NASA’s Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented.

  6. Fused silica mirror development for SIRTF

    NASA Technical Reports Server (NTRS)

    Barnes, W. P., Jr.

    1983-01-01

    An advanced design, lightweight, fuse-quartz mirror of sandwich construction was evaluated for optical figure performance at cryogenic temperatures. A low temperature shroud was constructed with an integral mirror mount and interface to a cryostat for use in a vacuum chamber. The mirror was tested to 13 K. Cryogenic distortion of the mirror was measured interferometrically. Separate interferometry of the chamber window during the test permitted subtraction of the small window distortions from the data. Results indicate that the imaging performance of helium cooled, infrared telescopes will be improved using this type of mirror without correction of cryogenic distortion of the primary mirror.

  7. Process for repairing large scratches on fused silica optics

    NASA Astrophysics Data System (ADS)

    Cormont, Philippe; Bourgeade, Antoine; Cavaro, Sandy; Doualle, Thomas; Gaborit, Gael; Gallais, Laurent; Rullier, Jean-Luc; Taroux, Daniel

    2015-10-01

    Scratches at the surface of fused silica optics can be detrimental for the performance of optical systems because they initiate damage on the optic but also they perturb the amplitude or phase of the transmitted laser light. Removing scratches by conventional polishing techniques can be time consuming as it is an iterative and long process, especially when hours of polishing time are required to obtain very high surface accuracy. So we have investigated ways to remove them with local laser processing. The silica is then heated at temperature higher than the softening point to heal the cracks.

  8. HVI Ballistic Limit Charaterization of Fused Silica Thermal Pane

    NASA Technical Reports Server (NTRS)

    Bohl, William E.; Miller, Joshua E.; Christiansen, Eric L.; Deighton, Kevin.; Davis, Bruce

    2015-01-01

    The Orion spacecraft's windows are exposed to the micrometeroid and orbital debris (MMOD) space environments while in space as well as the Earth entry environment at the mission's conclusion. The need for a low-mass spacecraft window design drives the need to reduce conservatism when assessing the design for loss of crew due to MMOD impact and subsequent Earth entry. Therefore, work is underway at NASA and Lockheed Martin to improve characterization of the complete penetration ballistic limit of an outer fused silica thermal pane. Hypervelocity impact tests of the window configuration at up to 10 km/s and hydrocode modeling have been performed with a variety of projectile materials to enable refinement of the fused silica ballistic limit equation.

  9. Fracture toughness of ultrashort pulse-bonded fused silica

    NASA Astrophysics Data System (ADS)

    Richter, S.; Naumann, F.; Zimmermann, F.; Tünnermann, A.; Nolte, S.

    2016-02-01

    We determined the bond interface strength of ultrashort pulse laser-welded fused silica for different processing parameters. To this end, we used a high repetition rate ultrashort pulse laser system to inscribe parallel welding lines with a specific V-shaped design into optically contacted fused silica samples. Afterward, we applied a micro-chevron test to measure the fracture toughness and surface energy of the laser-inscribed welding seams. We analyzed the influence of different processing parameters such as laser repetition rate and line separation on the fracture toughness and fracture surface energy. Welding the entire surface a fracture toughness of 0.71 {MPa} {m}^{1/2}, about 90 % of the pristine bulk material ({≈ } 0.8 {MPa} {m}^{1/2}), is obtained.

  10. Initiation Identification in Fused Silica 355-nm Optics

    SciTech Connect

    Wall, M; Plitzko, J; Fluss, M J

    2002-01-04

    Thermo-mechanical surface damage initiation and growth in fused-silica 3{omega} (355nm) optics are important performance and cost issues for high-power lasers (fluences of 4-14 J/cm{sup 2}) in the few ns pulse length regime. We are working to characterize and identify the extrinsic origins of damage initiation; impurities, particulates, and manufacturing defects. We have performed a materials characterization survey approach using transmission electron microscopy to identify the chemistry and morphology of particles, and structural defects. TEM offers high chemical or elemental specificity and small analytical spot size yielding complementary materials characterization data and powerful clues to manufacturing improvements. We will report on our characterization of the near surface of one commercially manufactures fused silica optic, where the results indicate both the efficacy and potential value of this approach.

  11. Mechanical protection of DLC films on fused silica slides

    NASA Technical Reports Server (NTRS)

    Nir, D.

    1985-01-01

    Measurements were made with a new test for improved quantitative estimation of the mechanical protection of thin films on optical materials. The mechanical damage was induced by a sand blasting system using spherical glass beads. Development of the surface damage was measured by the changes in the specular transmission and reflection, and by inspection using a surface profilometer and a scanning electron microscope. The changes in the transmittance versus the duration of sand blasting was measured for uncoated fused silica slides and coated ones. It was determined that the diamond like carbon films double the useful optical lifetime of the fused silica. Theoretical expressions were developed to describe the stages in surface deterioration. Conclusions were obtained for the SiO2 surface mechanism and for the film removal mechanism.

  12. Monolithic Cylindrical Fused Silica Resonators with High Q Factors.

    PubMed

    Pan, Yao; Wang, Dongya; Wang, Yanyan; Liu, Jianping; Wu, Suyong; Qu, Tianliang; Yang, Kaiyong; Luo, Hui

    2016-01-01

    The cylindrical resonator gyroscope (CRG) is a typical Coriolis vibratory gyroscope whose performance is determined by the Q factor and frequency mismatch of the cylindrical resonator. Enhancing the Q factor is crucial for improving the rate sensitivity and noise performance of the CRG. In this paper, for the first time, a monolithic cylindrical fused silica resonator with a Q factor approaching 8 × 10⁵ (ring-down time over 1 min) is reported. The resonator is made of fused silica with low internal friction and high isotropy, with a diameter of 25 mm and a center frequency of 3974.35 Hz. The structure of the resonator is first briefly introduced, and then the experimental non-contact characterization method is presented. In addition, the post-fabrication experimental procedure of Q factor improvement, including chemical and thermal treatment, is demonstrated. The Q factor improvement by both treatments is compared and the primary loss mechanism is analyzed. To the best of our knowledge, the work presented in this paper represents the highest reported Q factor for a cylindrical resonator. The proposed monolithic cylindrical fused silica resonator may enable high performance inertial sensing with standard manufacturing process and simple post-fabrication treatment. PMID:27483263

  13. Electrical properties of multiwalled carbon nanotube reinforced fused silica composites.

    PubMed

    Xiang, Changshu; Pan, Yubai; Liu, Xuejian; Shi, Xiaomei; Sun, Xingwei; Guo, Jingkun

    2006-12-01

    Multiwalled carbon nanotube (MWCNT)-fused silica composite powders were synthesized by solgel method and dense bulk composites were successfully fabricated via hot-pressing. This composite was characterized by XRD, HRTEM, and FESEM. MWCNTs in the hot-pressed composites are in their integrity observed by HRTEM. The electrical properties of MWCNT-fused silica composites were measured and analyzed. The electrical resistivity was found to decrease with the increase in the amount of the MWCNT loading in the composite. When the volume percentage of the MWCNTs increased to 5 vol%, the electrical resistivity of the composite is 24.99 omega cm, which is a decrease of twelve orders of value over that of pure fused silica matrix. The electrical resistivity further decreases to 1.742 omega. cm as the concentration of the MWCNTs increased to 10 vol%. The dielectric properties of the composites were also measured at the frequency ranging from 12.4 to 17.8 GHz (Ku band) at room temperature. The experimental results reveal that the dielectric properties are extremely sensitive to the volume percentage of the MWCNTs, and the permittivities, especially the imaginary permittivities, increase dramatically with the increase in the concentration of the MWCNTs. The improvement of dielectric properties in high frequency region mainly originates from the greatly increasing electrical properties of the composite. PMID:17256338

  14. Laser-driven mechanical fracture in fused silica

    NASA Astrophysics Data System (ADS)

    Dahmani, Faiz

    1999-10-01

    Fused silica, widely used as optical-window material in high-fluence requirements on glass and KrF lasers, experiences optical damage. Under fatigue conditions, the damage is initiated by slow crack growth and culminates, if not arrested, with catastrophic crack growth and implosive failure when the stress intensity approaches the critical value. Since laser-induced cracks cannot be eliminated entirely, the behavior of cracked structures under service conditions must be quantified to be predicted. Systematic scientific rules must be devised to characterize laser-induced cracks and their effects, and to predict if and when it may become necessary to replace the damaged components. This thesis makes a contribution toward this end. Measurements of fatigue failure strength of laser-cracked fused silica in air at room temperature for different number of laser pulses and laser fluences are presented. The failure-strength variability is found to be due mainly to the spectrum of crack depths. Agreement with theory suggests the incorporation of a residual term into the failure-strength equation. Experiments on residual stresses induced in fused silica by the presence of a laser-induced crack are carried out using two different techniques. Theoretical modelings show that this residual stress field is of shear nature and mouth-opening. A correlation between the reduction in fracture strength of fused silica and the increase of the residual-stress field is established, providing laser systems designers and operators with guidance on the rate of crack growth as well as on the stress-related ramifications such as laser-driven cracks entail. Specifically, a hoop-stress in the immediate vicinity of a crack growing along the beam propagation direction is identified as strongly coupling to both the laser fluence and the crack growth. This coupling prompted the question of whether or not breaking the hoop stress symmetry by some external perturbation will accelerate or stymie crack

  15. Photoluminescence defects on subsurface layer of fused silica and its effects on laser damage performance

    NASA Astrophysics Data System (ADS)

    Liu, Hongjie; Huang, Jin; Wang, Fengrui; Zhou, Xinda; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo

    2015-02-01

    Subsurface defects of polished fused silica optics are responsible for igniting laser damage in high power laser system. A non destructive measurement technique is developed to detect subsurface photoluminescence defects of fused silica. The fused silica samples polished by different vendors are applied to characterization of subsurface defects and measurement of damage performance. Subsurface photoluminescence defects of fused silica are evaluated by confocal fluorescence microscopy system. Laser induced damage threshold and damage density are measured by 355 nm nanosecond pulse laser. The results show a great differential subsurface quality of fused silica samples. Laser induced damage performance has a good correlation with subsurface defects. This paper shows a new non destructive measurement technique to detect photoluminescence defects on the subsurface layer of polished fused silica. It is very valuable to increasing laser damage performance and improving production-manufacturing engineering of optics.

  16. Temperature dependence of VUV transmission of synthetic fused silica

    NASA Astrophysics Data System (ADS)

    Franke, St.; Lange, H.; Schoepp, H.; Witzke, H.-D.

    2006-07-01

    The temperature dependence of the VUV transmission of synthetic fused silica is of interest for commercial applications as well as for fundamental research. In this work the transmission properties of Suprasil 2 from Heraeus with an absorption edge at very low wavelengths is investigated. The absorption edge of this quartz glass shifts from 170 to 180 nm between 789 and 1129 K. The Urbach rule is discussed for the characterization of the temperature dependent transmission curves. The results are applied to the diagnostics of the Hg 185 nm line from a high pressure mercury discharge lamp.

  17. Hypervelocity impact damage tolerance of fused silica glass

    NASA Technical Reports Server (NTRS)

    Edelstein, K. S.

    1992-01-01

    A test program was conducted at the NASA/Johnson Space Center (JSC) concerning hypervelocity impact damage in fused silica glass. The objectives of this test program were: to expand the penetration equation data base in the velocity range between 2 and 8 km/s; to determine how much strength remains in a glass pane that has sustained known impact damage; and to develop a relationship between crater measurements and residual strength predictions that can be utilized in the Space Shuttle and Space Station programs. The results and conclusions of the residual strength testing are discussed below. Detailed discussion of the penetration equation studies will follow in future presentations.

  18. 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.

  19. The mechanism of growth of quartz crystals into fused silica

    NASA Technical Reports Server (NTRS)

    Fratello, V. J.; Hays, J. F.; Spaepen, F.; Turnbull, D.

    1980-01-01

    It is proposed that the growth of quartz crystals into fused silica is effected by a mechanism involving the breaking of an Si-O bond and its association with an OH group, followed by cooperative motion of the nonbridging oxygen and the hydroxyl group which results in the crystallization of a row of several molecules along a crystalline-amorphous interfacial ledge. This mechanism explains, at least qualitatively, all the results of the earlier experimental study of the dependence of quartz crystal growth upon applied pressure: large negative activation volume; single activation enthalpy below Si-O bond energy; growth velocity constant in time, proportional to the hydroxyl and chlorine content, decreasing with increasing degree of reduction, and enhanced by nonhydrostatic stresses; lower pre-exponential for the synthetic than for the natural silica.

  20. High strain rate fracture behavior of fused silica

    NASA Astrophysics Data System (ADS)

    Ruggiero, Andrew; Iannitti, Gianluca; Testa, Gabriel; Limido, Jerome; Lacome, Jean; Olovsson, Lars; Ferraro, Mario; Bonora, Nicola

    2013-06-01

    Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the strain rate related effects become significant and should be accounted for in the constitutive modeling. In this study, the procedure for constitutive model validation and model parameters identification, is presented. Taylor impact tests and drop weight tests were designed and performed at different impact velocities, from 1 to 100 m/s, and strain rates, from 102 up to 104 s-1. Numerical simulation of both tests was performed with IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. Model parameters were identified by optimization using multiple validation metrics. The validity of the parameters set determined with the proposed procedure was verified comparing numerical predictions and experimental results for an independent designed test consisting in a fused silica tile impacted at prescribed velocity by a steel sphere.

  1. Thermal annealing of laser damage precursors on fused silica surfaces

    SciTech Connect

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

    2012-03-19

    Previous studies have identified two significant precursors of laser damage on fused silica surfaces at fluenes below {approx} 35 J/cm{sup 2}, photoactive impurities in the polishing layer and surface fractures. In the present work, isothermal heating is studied as a means of remediating the highly absorptive, defect structure associated with surface fractures. A series of Vickers indentations were applied to silica surfaces at loads between 0.5N and 10N creating fracture networks between {approx} 10{micro}m and {approx} 50{micro}m in diameter. The indentations were characterized prior to and following thermal annealing under various times and temperature conditions using confocal time-resolved photo-luminescence (CTP) imaging, and R/1 optical damage testing with 3ns, 355nm laser pulses. Significant improvements in the damage thresholds, together with corresponding reductions in CTP intensity, were observed at temperatures well below the glass transition temperature (T{sub g}). For example, the damage threshold on 05.N indentations which typically initiates at fluences <8 J/cm{sup 2} could be improved >35 J/cm{sup 2} through the use of a {approx} 750 C thermal treatment. Larger fracture networks required longer or higher temperature treatment to achieve similar results. At an annealing temperature > 1100 C, optical microscopy indicates morphological changes in some of the fracture structure of indentations, although remnants of the original fracture and significant deformation was still observed after thermal annealing. This study demonstrates the potential of using isothermal annealing as a means of improving the laser damage resistance of fused silica optical components. Similarly, it provides a means of further understanding the physics associated with optical damage and related mitigation processes.

  2. Morphology and structure of particles produced by femtosecond laser ablation of fused silica

    NASA Astrophysics Data System (ADS)

    Sharma, S. P.; Oliveira, V.; Vilar, Rui

    2016-04-01

    The aim of the present work was to study the morphology and structure of the nanoparticles produced by femtosecond laser ablation of fused silica. Ultrashort laser pulses of 1030 nm wavelength and 550 fs duration were tightly focused by a high numerical aperture microscope objective at the surface of fused silica samples while scanning the sample in relation to the stationary laser beam. Laser tracks were created with pulse energies in the range 5-100 μJ, resulting in ablation debris of different morphologies. The debris were examined by scanning and transmission electron microscopy for their morphology and crystal structure in relation to the incident laser pulse energy. Ejected particles with sizes ranging from a few nanometers to a few microns were found. Their morphologies can be broadly classified into three categories: very fine round nanoparticles with diameters lower than 20 nm, nanoparticles with intermediate sizes between 50 and 200 nm, and big irregular particles with typical size between 0.5 and 1.5 μm. The fine nanoparticles of the first category are predominantly observed at higher pulse energies and tend to aggregate to form web-like and arborescent-like structures. The nanoparticles with intermediate sizes are observed for all pulse energies used and may appear isolated or aggregated in clusters. Finally, the larger irregular particles of the third category are observed for all energies and appear normally isolated.

  3. 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.

  4. Optical waveguides fabricated by nitrogen ion implantation in fused silica

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Xiao; Fu, Li-Li; Zheng, Rui-Lin; Guo, Hai-Tao; Zhou, Zhi-Guang; Li, Wei-Nan; Lin, She-Bao; Wei, Wei

    2016-02-01

    We report on the fabrication of waveguides in fused silica using 4.5-MeV nitrogen ion implantation with a fluence of 5.0×1014 ions/cm2. The prism-coupling method was employed to measure the effective refractive indices of guiding modes at the wavelengths of 632.8 and 1539 nm. The effective refractive indices of the first few modes were higher than that of the substrate. The refractive index profiles at 632.8 and 1539 nm were reconstructed by the reflectivity calculation method. Positive index changes were induced in the waveguide layers. The end-face coupling method was used to measure the near-field light intensity distributions at the wavelength of 632.8 nm and the finite-difference beam propagation method was applied to simulate the guided mode profile at the wavelength of 1539 nm. The waveguide structures emerge as candidates for integrated photonic devices.

  5. Optical Properties of the DIRC Fused Silica Radiator

    SciTech Connect

    Convery, Mark R

    2003-04-15

    The DIRC detector is successfully operating as the hadronic particle identification system for the BaBar experiment at SLAC. The production of its Cherenkov radiator required much effort in practice, both in manufacture and conception, which in turn required a large number of R&D measurements. One of the major outcomes of this R&D work was an understanding of methods to select radiation hard and optically uniform fused silica material. Others included measurement of the wavelength dependency of the internal reflection coefficient, and its sensitivity to the surface pollution, selection of the radiator support, selection of good optical glue, etc. This note summarizes the optical R&D test results.

  6. Fabrication of microchannels in fused silica using femtosecond Bessel beams

    SciTech Connect

    Yashunin, D. A.; Malkov, Yu. A.; Mochalov, L. A.; Stepanov, A. N.

    2015-09-07

    Extended birefringent waveguiding microchannels up to 15 mm long were created inside fused silica by single-pulse irradiation with femtosecond Bessel beams. The birefringent refractive index change of 2–4 × 10{sup −4} is attributed to residual mechanical stress. The microchannels were chemically etched in KOH solution to produce 15 mm long microcapillaries with smooth walls and a high aspect ratio of 1:250. Bessel beams provide higher speed of material processing compared to conventional multipulse femtosecond laser micromachining techniques and permit simple control of the optical axis direction of the birefringent waveguides, which is important for practical applications [Corrielli et al., “Rotated waveplates in integrated waveguide optics,” Nat. Commun. 5, 4249 (2014)].

  7. Modification of nanostructured fused silica for use as superhydrophobic, IR-transmissive, anti-reflective surfaces

    NASA Astrophysics Data System (ADS)

    Boyd, Darryl A.; Frantz, Jesse A.; Bayya, Shyam S.; Busse, Lynda E.; Kim, Woohong; Aggarwal, Ishwar; Poutous, Menelaos; Sanghera, Jasbinder S.

    2016-04-01

    In order to mimic and enhance the properties of moth eye-like materials, nanopatterned fused silica was chemically modified to produce self-cleaning substrates that have anti-reflective and infrared transmissive properties. The characteristics of these substrates were evaluated before and after chemical modification. Furthermore, their properties were compared to fused silica that was devoid of surface features. The chemical modification imparted superhydrophobic character to the substrates, as demonstrated by the average water contact angles which exceeded 170°. Finally, optical analysis of the substrates revealed that the infrared transmission capabilities of the fused silica substrates (nanopatterned to have moth eye on one side) were superior to those of the regular fused silica substrates within the visible and near-infrared region of the light spectrum, with transmission values of 95% versus 92%, respectively. The superior transmission properties of the fused silica moth eye were virtually unchanged following chemical modification.

  8. Surface Effects on Young's Modulud and Hardness of Fused Silica by Nanoindentation Study

    SciTech Connect

    Zheng, L.; Schmid, A.W.; Lambropoulos, J.C.

    2007-01-24

    The surface Young's modulus (E) and hardness (H) of fused silica samples have been studied by nanoindentation. Two factors strongly affect the results of E and H. One factor is the polishing quality of the fused silica surface. Poor polishing quality produces much smaller E and H than the literature values for bulk fused silica. The second factor is surface flatness. Even for a well-polished silica surface, an "arch bridge effect" may hinder the measurements of the true values of E and H. A correction procedure is proposed to eliminate this effect, and the corrected results show substantial improvements.

  9. Effect of optical coating and surface treatments on mechanical loss in fused silica

    NASA Astrophysics Data System (ADS)

    Gretarsson, Andri M.; Harry, Gregory M.; Penn, Steven D.; Saulson, Peter R.; Schiller, John J.; Startin, William J.

    2000-06-01

    We report on the mechanical loss in fused silica samples with various surface treatments and compare them with samples having an optical coating. Mild surface treatments such as washing in detergent or acetone were not found to affect the mechanical loss of flame-drawn fused silica fibers stored in air. However, mechanical contact (with steel calipers) significantly increased the loss. The application of a high-reflective optical coating of the type used for the LIGO test masses was found to greatly increase the mechanical loss of commercially polished fused silica microscope slides. We discuss the implications for the noise budget of interferometers. .

  10. High strain rate fracture behaviour of fused silica

    NASA Astrophysics Data System (ADS)

    Ruggiero, A.; Iannitti, G.; Testa, G.; Limido, J.; Lacome, J. L.; Olovsson, L.; Ferraro, M.; Bonora, N.

    2014-05-01

    Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the strain rate related effects become significant and should be accounted for in the constitutive modelling. In this study, the Johnson-Holmquist (J-H) model parameters have been identified by inverse calibration technique, on selected validation test configurations, according to the procedure described hereafter. Numerical simulations were performed with LS-DYNA and IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. In order to overcome numerical drawbacks associated with element erosion, a modified version of the J-H model is proposed.

  11. Time-resolved shadowgraphy of optical breakdown in fused silica

    NASA Astrophysics Data System (ADS)

    Tran, K. A.; Grigorov, Y. V.; Nguyen, V. H.; Rehman, Z. U.; Le, N. T.; Janulewicz, K. A.

    2015-07-01

    Dynamics of a laser-induced optical breakdown in the bulk of fused silica initiated by a sub-nanosecond laser pulse of an energy fluence as high as 8.7 kJ/cm2 was investigated by using femtosecond time-resolved shadowgraphy. Plasma ignition, growth of the damaged region and accompanying hydrodynamic motion were recorded from the moment directly before the arrival of the driving laser pulse, in the time steps adapted to the rate of the occurring processes. The growth rate of the plasma channel, curvature radii and velocities of the wave fronts were extracted from the shadowgrams. It was found that the plasma channel develops with a supersonic velocity and the first observed shock front tends to transform itself from the initial bowl-like shape to the final spherical one characterising an acoustic wave. Appearance of multiple fronts accompanying the main shock front was registered and used in more detailed analysis of the optical breakdown dynamics in the transparent dielectrics.

  12. FUSED SILICA CAPILLARY COLUMN GC/MS FOR THE ANALYSIS OF PRIORITY POLLUTANTS

    EPA Science Inventory

    Operational characteristics have been determined for fused silica capillary column (FSCC) GC/MS as applied to 'extractable' priority pollutants. Chromatographic data show excellent relative retention time (RRT) intralaboratory precision and interlaboratory accuracy when multiple ...

  13. Laser-induced fluorescence of fused silica irradiated by ArF excimer laser

    SciTech Connect

    Zhang Haibo; Yuan Zhijun; Zhou Jun; Dong Jingxing; Wei Yunrong; Lou Qihong

    2011-07-01

    Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

  14. Mitigation of organic laser damage precursors from chemical processing of fused silica.

    PubMed

    Baxamusa, S; Miller, P E; Wong, L; Steele, R; Shen, N; Bude, J

    2014-12-01

    Increases in the laser damage threshold of fused silica have been driven by the successive elimination of near-surface damage precursors such as polishing residue, fractures, and inorganic salts. In this work, we show that trace impurities in ultrapure water used to process fused silica optics may be responsible for the formation of carbonaceous deposits. We use surrogate materials to show that organic compounds precipitated onto fused silica surfaces form discrete damage precursors. Following a standard etching process, solvent-free oxidative decomposition using oxygen plasma or high-temperature thermal treatments in air reduced the total density of damage precursors to as low as <50 cm(-2). Finally, we show that inorganic compounds are more likely to cause damage when they are tightly adhered to a surface, which may explain why high-temperature thermal treatments have been historically unsuccessful at removing extrinsic damage precursors from fused silica. PMID:25606889

  15. Shock-wave equation-of-state measurements in fused silica up to 1600 GPa

    DOE PAGESBeta

    McCoy, C. A.; Gregor, M. C.; Polsin, D. N.; Fratanduono, D. E.; Celliers, P. M.; Boehly, T. R.; Meyerhofer, D. D.

    2016-06-02

    The properties of silica are important to geophysical and high-pressure equation of state research. The most prevalent crystalline form, α-quartz, has been extensively studied to TPa pressures. Recent experiments with amorphous silica, commonly referred to as fused silica, provided Hugoniot and reflectivity data up to 630 GPa using magnetically-driven aluminum impactors. This article presents measurements of the fused silica Hugoniot over the range from 200 to 1600 GPa using laser-driven shocks with a quartz standard. These results extend the measured Hugoniot of fused silica to higher pressures, but more importantly, in the 200-600 GPa range, the data are very goodmore » agreement with those obtained with a different driver and standard material. As a result, a new shock velocity-particle velocity relation is derived to fit the experimental data.« less

  16. Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting

    NASA Astrophysics Data System (ADS)

    Wan, Wei; Huang, Chun-e.; Yang, Jian; Zeng, Jinzhen; Qiu, Tai

    2014-07-01

    Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N' N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densification and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum flexural strength, as high as 81.32 MPa, but, simultaneously, a high coefficient of linear expansion (2.56 × 10-6/K at 800°C) and dramatically reduced residual flexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar flexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 × 10-3 (at 1 MHz).

  17. 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

  18. Fused Silica Surface Coating for a Flexible Silica Mat Insulation System

    NASA Technical Reports Server (NTRS)

    Rhodes, W. H.

    1973-01-01

    Fused silica insulation coatings have been developed for application to a flexible mat insulation system. Based on crystalline phase nucleation and growth kinetics, a 99+% SiO2 glass was selected as the base composition. A coating was developed that incorporated the high emissivity phase NiCr2O4 as a two phase coating with goals of high emittance and minimum change in thermal expansion. A second major coating classification has a plasma sprayed emittance coating over a sealed pure amorphous SiO2 layer. A third area of development centered on extremely thin amorphous SiO2 coatings deposited by chemical vapor deposition. The coating characterization studies presented are mechanical testing of thin specimens extracted from the coatings, cyclic arc exposures, and emittance measurements before and after arc exposures.

  19. Material removal and surface figure during pad polishing of fused silica

    SciTech Connect

    Suratwala, T I; Feit, M D; Steele, W A

    2009-05-04

    The material removal and surface figure after ceria pad polishing of fused silica glass have been measured and analyzed as a function of kinematics, loading conditions, and polishing time. Also, the friction at the workpiece/lap interface, the slope of the workpiece relative to the lap plane, and lap viscoelastic properties have been measured and correlated to material removal. The results show that the relative velocity between the workpiece & lap (determined by the kinematics) and the pressure distribution determine the spatial and temporal material removal and hence the final surface figure of the workpiece. In the case where the applied loading and relative velocity distribution over the workpiece are spatially uniform, a significant non-uniform spatial material removal from the workpiece surface is observed. This is due to a non-uniform pressure distribution resulting from: (1) a moment caused by a pivot point and interface friction forces; (2) viscoelastic relaxation of the polyurethane lap; and (3) a physical workpiece/lap interface mismatch. Both the kinematics and these contributions to the pressure distribution are quantitatively described, and then combined to form a spatial and temporal Preston model & code for material removal (called Surface Figure or SurF{copyright}). The surface figure simulations are consistent with the experiment for a wide variety of polishing conditions. This study is an important step towards deterministic full-aperture polishing, which would allow optical glass fabrication to be performed in a more repeatable, less iterative, and hence more economical manner.

  20. Generation of microstripe cylindrical and toroidal mirrors by localized laser evaporation of fused silica.

    PubMed

    Wlodarczyk, Krystian L; Thomson, Ian J; Baker, Howard J; Hall, Denis R

    2012-09-10

    We report a new technique for the rapid fabrication of microstripe cylindrical and toroidal mirrors with a high ratio (>10) of the two principal radii of curvature (RoC(1)/RoC(2)), and demonstrate their effectiveness as mode-selecting resonator mirrors for high-power planar waveguide lasers. In this process, the larger radius of curvature (RoC(1)) is determined by the planar or cylindrical shape of the fused silica substrate selected for laser processing, whilst the other (RoC(2)) is produced by controlled CO(2) laser-induced vaporization of the glass. The narrow stripe mirror aperture is achieved by applying a set of partially overlapped laser scans, with the incident laser power, the number of laser scans, and their spacing being used to control the curvature produced by laser evaporation. In this work, a 1 mm diameter laser spot is used to produce grooves of cylindrical/toroidal shape with 240 μm width and 16 mm length. After high reflectance coating, these grooves are found to provide excellent mode selectivity as resonator mirrors for a 150 μm core Yb:YAG planar waveguide laser, producing high brightness output at more than 300 W. The results show clearly that the laser-generated microstripe mirrors can improve the optical performance of high-power planar waveguide lasers when applied in a low-loss mode-selective resonator configuration. PMID:22968274

  1. Colloid formation in copper-implanted fused silica and silicate glasses

    SciTech Connect

    Mazzoldi, P.; Caccavale, F.; Cattaruzza, E.

    1993-12-31

    Copper implantations (90 keV, 5{times}10{sup 16} ions/cm{sup 2}) were made into fused silica, borosilicate glasses and soda-lime glass. The copper distribution has been found to vary according to glass type. The optical absorption band characteristic of the implanted metal optical properties was observed only for copper-implanted fused silica. Absorption for all the other samples was either not observable or was negligibly small, however very small metallic particles are present also in soda-lime glass. Subsequent nitrogen implantation (100 keV, 1.5{times}10{sup 17} ions/cm{sup 2}) completely eliminated the copper-colloid induced absorption in the copper-implanted fused silica, while it facilitated formation of copper-colloids in soda-lime glass.

  2. Metallic-like photoluminescence and absorption in fused silica surface flaws

    SciTech Connect

    Laurence, T A; Bude, J D; Shen, N; Feldman, T; Miller, P; Steele, W A; Suratwala, T

    2008-09-11

    Using high-sensitivity confocal time-resolved photoluminescence (PL) techniques, we report an ultra-fast PL (40ps-5ns) from impurity-free surface flaws on fused silica, including polished, indented or fractured surfaces of fused silica, and from laser-heated evaporation pits. This PL is excited by the single photon absorption of sub-band gap light, and is especially bright in fractures. Regions which exhibit this PL are strongly absorptive well below the band gap, as evidenced by a propensity to damage with 3.5eV ns-scale laser pulses.

  3. Development of a Process Model for CO(2) Laser Mitigation of Damage Growth in Fused Silica

    SciTech Connect

    Feit, M D; Rubenchik, A M; Boley, C; Rotter, M D

    2003-11-01

    A numerical model of CO{sub 2} laser mitigation of damage growth in fused silica has been constructed that accounts for laser energy absorption, heat conduction, radiation transport, evaporation of fused silica and thermally induced stresses. This model will be used to understand scaling issues and effects of pulse and beam shapes on material removal, temperatures reached and stresses generated. Initial calculations show good agreement of simulated and measured material removal. The model has also been applied to LG-770 glass as a prototype red blocker material.

  4. Optimum inductively coupled plasma etching of fused silica to remove subsurface damage layer

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaolong; Liu, Ying; Liu, Zhengkun; Qiu, Keqiang; Xu, Xiangdong; Hong, Yilin; Fu, Shaojun

    2015-11-01

    In this work, we introduce an optimum ICP etching technique that successfully removes the subsurface damage (SSD) layer of fused silica without causing plasma induced surface damage (PISD) or lateral etching of SSD. As one of the commonest PISD initiators, metal contamination from reactor chamber is prevented by employing a simple isolation device. Based on this device, a unique low-density pitting damage is discovered and subsequently eliminated by optimizing the etching parameters. Meanwhile etching anisotropy also improves a lot, thus preventing the lateral etching of SSD. Using this proposed technique, SSD layer of fused silica is successfully removed with a surface roughness of 0.23 nm.

  5. Ion trap mass spectrometric detection of laser desorbed ions from derivatized fused silica fibers

    SciTech Connect

    Garrett, A.W.; Earl, W.L.; Cisper, M.E.; Nogar, N.S.; Hemberger, P.H.

    1994-12-31

    Solid-phase microextraction of analytes from complex matrices using fused silica fibers has many advantages over traditional chemical sample preparation technique. Microextraction requires small sample sizes little sample preparation (providing rapid sample turnaround time), and greatly reduces the amount of chemical waste generated in sample preparation. These advantages make fused silica fibers attractive for direct sampling and detection experiments using laser desorption ion trap mass spectrometry (LITMS). The drawback is the very small area ({approximately}1 mm{sup 2}) exposed to laser irradiation, which limits the amount of material desorbed into the ion trap.

  6. Shock-wave equation-of-state measurements in fused silica up to 1600 GPa

    NASA Astrophysics Data System (ADS)

    McCoy, C. A.; Gregor, M. C.; Polsin, D. N.; Fratanduono, D. E.; Celliers, P. M.; Boehly, T. R.; Meyerhofer, D. D.

    2016-06-01

    The properties of silica are important to geophysical and high-pressure equation-of-state research. Its most-prevalent crystalline form, α-quartz, has been extensively studied to TPa pressures. This article presents Hugoniot measurements on amorphous silica, commonly referred to as fused silica, over a range from 200 to 1600 GPa using laser-driven shocks and an α-quartz standard. These results extend the measured Hugoniot of fused silica to higher pressures. In the 200- to 600-GPa range, the data are in very good agreement with those obtained by Qi et al. [Phys. Plasmas 22, 062706 (2015)] using magnetically driven aluminum impactors and aluminum as a standard material. A new shock velocity/particle velocity relation is derived to fit the experimental data.

  7. 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.

  8. Yb/Al-codoped fused-silica planar-waveguide amplifier

    NASA Astrophysics Data System (ADS)

    Atar, Gil; Eger, David; Bruner, Ariel; Sfez, Bruno; Ruschin, Shlomo

    2016-05-01

    We report an Yb/Al-codoped fused silica planar waveguide amplifier with <0.2 dB/cm passive loss and 0.6 dB/cm gain, featuring a high damage threshold (>0.1 GW/cm2) and a relatively large core (20 μm thick). Waveguide fabrication is based on a novel silica-on-silica technology combining modified-chemical-vapor deposition and a high temperature CO2 laser treatment for making high-power photonic devices.

  9. Femtosecond laser ablation dynamics of fused silica extracted from oscillation of time-resolved reflectivity

    SciTech Connect

    Kumada, Takayuki Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Yokoyama, Atsushi

    2014-03-14

    Femtosecond laser ablation dynamics of fused silica is examined via time-resolved reflectivity measurements. After optical breakdown was caused by irradiation of a pump pulse with fluence F{sub pump} = 3.3–14.9 J/cm{sup 2}, the reflectivity oscillated with a period of 63 ± 2 ps for a wavelength λ = 795 nm. The period was reduced by half for λ = 398 nm. We ascribe the oscillation to the interference between the probe pulses reflected from the front and rear surfaces of the photo-excited molten fused silica layer. The time-resolved reflectivity agrees closely with a model comprising a photo-excited layer which expands due to the formation of voids, and then separates into two parts, one of which is left on the sample surface and the other separated as a molten thin layer from the surface by the spallation mechanism. Such oscillations were not observed in the reflectivity of soda-lime glass. Whether the reflectivity oscillates or not probably depends on the layer viscosity while in a molten state. Since viscosity of the molten fused silica is several orders of magnitude higher than that of the soda-lime glass at the same temperature, fused silica forms a molten thin layer that reflects the probe pulse, whereas the soda-lime glass is fragmented into clusters.

  10. Infrared telescope design - Implications from cryogenic tests of fused-silica mirrors

    NASA Technical Reports Server (NTRS)

    Melugin, R. K.; Miller, J. H.

    1983-01-01

    A brief review of results from recent cryogenic tests of fused-silica mirrors is given with consideration of the implications for the design of cooled infrared telescopes. Implications include optical performance with a discusion of the top-down optical error budgeting for the Shuttle Infrared Telescope Facility (SIRTF), thermal properties of the mirrors, and mirror mounting.

  11. Achieving low-wavefront specifications for DUV lithography: impact of residual stress in HPFS fused silica

    NASA Astrophysics Data System (ADS)

    Ladison, Julie L.; Ellison, Joseph F.; Allan, Douglas C.; Fladd, David R.; Fanning, Andrew W.; Priestley, Richard

    2001-09-01

    As optical lithographers push to extend optical lithography technologies to create smaller features with higher NA, lower k1 values and shorter wavelengths, transmitted wavefront specifications for HPFSR fused silica blanks continue to tighten. HPFSR fused silica blanks are typically certified for acceptance using an interferometer operating at a wavelength of 632.8 nm. As the market demands increasingly tighter homogeneity specifications, it has become critical to understand the sources of variation in wavefront measurements. Corning has recently initiated a study to identify those sources of variation. One glass attribute being studied is the impact of residual stress on the wavefront. It is known that residual stresses can alter the refractive index of fused silica. To obtain the residual stress measurements, birefringence measurements were obtained at 632.8 nm for comparison to wavefront measurements at 632.8 nm. The relationship between residual birefringence and transmitted wavefront measurements, at 632.8 nm on Corning HPFSR fused silica blanks, is explored in this paper.

  12. Multi-Length Scale Analysis of the Effect of Fused-Silica Pre-shocking on its Tendency for Devitrification

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Snipes, J. S.; Ramaswami, S.

    2016-03-01

    Recent studies have suggested that impact-induced devitrification of fused silica, or more specifically formation of high-density stishovite, can significantly improve ballistic-penetration resistance of fused silica, the material which is used in transparent armor. The studies have also shown that in order for stishovite to form during a ballistic impact event, very high projectile kinetic energy normalized by the projectile/fused-silica target-plate contact area must accompany such an event. Otherwise fused-silica devitrification, if taking place, does not substantially improve the material ballistic-penetration resistance. In the present work, all-atom molecular-level computations are carried out in order to establish if pre-shocking of fused-silica target-plates (to form stishovite) and subsequent unloading (to revert stishovite to the material amorphous structure) can increase fused silica's propensity for stishovite formation during a ballistic impact. Towards that end, molecular-level computational procedures are developed to simulate both the pre-shocking treatment of the fused-silica target-plate and its subsequent impact by a solid right-circular cylindrical projectile. The results obtained clearly revealed that when strong-enough shockwaves are used in the fused-silica target-plate pre-shocking procedure, the propensity of fused silica for stishovite formation during the subsequent ballistic impact is increased, as is the associated ballistic-penetration resistance. To rationalize these findings, a detailed post-processing microstructural analysis of the pre-shocked material is employed. The results obtained suggest that fused silica pre-shocked with shockwaves of sufficient strength retain some memory/embryos of stishovite, and these embryos facilitate stishovite formation during the subsequent ballistic impact.

  13. Bulk damage and absorption in fused silica due to high-power laser applications

    NASA Astrophysics Data System (ADS)

    Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

    2015-11-01

    Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and

  14. Direct die-to-database electron-beam inspection of fused silica imprint templates

    NASA Astrophysics Data System (ADS)

    Tsuneoka, M.; Hasebe, T.; Tokumoto, T.; Yan, C.; Yamamoto, M.; Resnick, D. J.; Thompson, E.; Wakamori, H.; Inoue, M.; Ainley, Eric; Nordquist, Kevin J.; Dauksher, William J.

    2006-10-01

    Imprint lithography has been included on the ITRS Lithography Roadmap at the 32 and 22 nm nodes. Step and Flash Imprint Lithography (S-FIL TM) is a unique method for printing sub-100 nm geometries. Relative to other imprinting processes S-FIL has the advantage that the template is transparent, thereby facilitating conventional overlay techniques. Further, S-FIL provides sub-100 nm feature resolution without the significant expense of multi-element, high quality projection optics or advanced illumination sources. However, since the technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates. With respect to inspection, although defects as small as 70 nm have been detected using optical techniques, it is clear that it will be necessary to take advantage of the resolution capabilities of electron beam inspection techniques. The challenge is in inspecting templates composed purely of fused silica. This paper reports the inspection of both fused silica wafers and plates. The die-to-database inspection of the wafers was performed on an NGR2100 inspection system. Fused silica plates were inspected using an NGR4000 system. Three different experiments were performed. In the first study, Metal 1 and Logic patterns as small as 40 nm were patterned on a 200 mm fused silica wafer. The patterns were inspected using an NGR2100 die-to-database inspection system. In the second experiment, a 6025 fused silica plate was employed. Patterns with a limited field of view (FOV) were inspected using an NGR4000 reticle-based system. To test the tool's capability for larger FOVs, 16 × 16 μm areas on a MoSi half tone plate were scanned and stitched together to evaluate the tool's ability to reliably do die-to-database comparisons across larger inspection areas.

  15. 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

  16. 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

  17. 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.

  18. The Effect of High-Pressure Devitrification and Densification on Ballistic-Penetration Resistance of Fused Silica

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Avuthu, V.; Snipes, J. S.; Ramaswami, S.; Galgalikar, R.

    2015-12-01

    Recent experimental and molecular-level computational analyses have indicated that fused silica, when subjected to pressures of several tens of GPa, can experience irreversible devitrification and densification. Such changes in the fused-silica molecular-level structure are associated with absorption and/or dissipation of the strain energy acquired by fused silica during high-pressure compression. This finding may have important practical consequences in applications for fused silica such as windshields and windows of military vehicles, portholes in ships, ground vehicles, spacecraft, etc. In the present work, our prior molecular-level computational results pertaining to the response of fused silica to high pressures (and shear stresses) are used to enrich a continuum-type constitutive model (that is, the so-called Johnson-Holmquist-2, JH2, model) for this material. Since the aforementioned devitrification and permanent densification processes modify the response of fused silica to the pressure as well as to the deviatoric part of the stress, changes had to be made in both the JH2 equation of state and the strength model. To assess the potential improvements in respect to the ballistic-penetration resistance of this material brought about by the fused-silica devitrification and permanent densification processes, a series of transient non-linear dynamics finite-element analyses of the transverse impact of a fused-silica test plate with a solid right-circular cylindrical steel projectile were conducted. The results obtained revealed that, provided the projectile incident velocity and, hence, the attendant pressure, is sufficiently high, fused silica can undergo impact-induced devitrification, which improves its ballistic-penetration resistance.

  19. 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.

  20. Origin of the damage ring pattern in fused silica induced by multiple longitudinal modes laser pulses

    NASA Astrophysics Data System (ADS)

    Chambonneau, M.; Diaz, R.; Grua, P.; Rullier, J.-L.; Duchateau, G.; Natoli, J.-Y.; Lamaignère, L.

    2014-01-01

    Ring patterns surrounding laser damage sites at the exit surface of fused silica are systematically observed when initiated by multiple longitudinal modes nanosecond laser pulses at 1064 nm. The appearance chronology of rings is found to be closely related to the temporal shape of the laser pulses. This supports that the damage morphology originates from the coupling of a laser-supported detonation wave propagating in air with an ablation mechanism in silica. In our experiments, the propagation speed of the detonation wave reaches about 20 km/s and scales as the cube root of the laser intensity, in good agreement with theory.

  1. Numerical simulations of ultrashort laser pulse multifilamentation in fused silica: plasma channels statistics

    NASA Astrophysics Data System (ADS)

    Geints, Yu E.; Zemlyanov, A. A.

    2016-01-01

    The regime of multiple filamentation of gigawatt-power femtosecond laser pulses in fused silica bars is theoretically investigated. Numerical simulations are used to analyze the fine spatial structure of the plasma region formed due to photoionization of silica and accompanying pulse filamentation. The dependence of the number, spatial position, and length of different generations of plasma channels on the energy and focusing conditions of the optical pulse is studied. The role of pulse sequential refocusing in the formation of the plasma region is discussed.

  2. 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.

  3. Experimental measurements of the spectral absorption coefficient of pure fused silica optical fibers.

    PubMed

    Moore, Travis J; Jones, Matthew R

    2015-02-20

    Knowledge of the spectral absorption coefficient of fused silica optical fibers is important in modeling heat transfer in the processes and applications in which these fibers are used. An experimental method used to measure the spectral absorption coefficient of optical fibers is presented. Radiative energy from a blackbody radiator set at different temperatures is directed through the optical fibers and into an FTIR spectrometer. Spectral instrument response functions are calculated for different fiber lengths. The ratios of the slopes of the instrument response functions for the different lengths of fibers are used to solve for the spectral absorption coefficient of the fibers. The spectral absorption coefficient of low OH pure fused silica optical fibers is measured between the wavelengths 1.5 and 2.5 μm. PMID:25968202

  4. Microwave interrogated large core fused silica fiber Michelson interferometer for strain sensing.

    PubMed

    Hua, Liwei; Song, Yang; Huang, Jie; Lan, Xinwei; Li, Yanjun; Xiao, Hai

    2015-08-20

    A Michelson-type large core optical fiber sensor has been developed, which is designed based on the optical carrier-based microwave interferometry technique, and fabricated by using two pieces of 200-μm diameter fused silica core fiber as two arms of the Michelson interferometer. The interference fringe pattern caused by the optical path difference of the two arms is interrogated in the microwave domain, where the fringe visibility of 40 dB has easily been obtained. The strain sensing at both room temperature and high temperatures has been demonstrated by using such a sensor. Experimental results show that this sensor has a linear response to the applied strain, and also has relatively low temperature-strain cross talk. The dopant-free quality of the fused silica fiber provides high possibility for the sensor to have promising strain sensing performance in a high temperature environment. PMID:26368751

  5. Numerical simulation of modulation to incident laser by submicron to micron surface contaminants on fused silica

    NASA Astrophysics Data System (ADS)

    Liang, Yang; Xia, Xiang; Xin-Xiang, Miao; Li, Li; Xiao-Dong, Yuan; Zhong-Hua, Yan; Guo-Rui, Zhou; Hai-Bing, Lv; Wan-Guo, Zheng; Xiao-Tao, Zu

    2016-01-01

    Modulation caused by surface/subsurface contaminants is one of the important factors for laser-induced damage of fused silica. In this work, a three-dimensional finite-difference time-domain (3D-FDTD) method is employed to simulate the electric field intensity distribution in the vicinity of particulate contaminants on fused silica surface. The simulated results reveal that the contaminant on both the input and output surfaces plays an important role in the electric field modulation of the incident laser. The influences of the shape, size, embedded depth, dielectric constant (ɛr), and the number of contaminant particles on the electric field distribution are discussed in detail. Meanwhile, the corresponding physical mechanism is analyzed theoretically. Project supported by the National Natural Science Foundation of China (Grant No. 61178018) and the Ph.D. Funding Support Program of Education Ministry of China (Grant No. 20110185110007).

  6. Controllable damping of high-Q violin modes in fused silica suspension fibers

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Mescheriakov, S. D.; Tokmakov, K. V.; Mitrofanov, V. P.

    2010-01-01

    Fused silica fiber suspension of the test masses will be used in the interferometric gravitational wave detectors of the next generation. This allows a significant reduction of losses in the suspension and thermal noise associated with the suspension. Unfortunately, unwanted violin modes may be accidentally excited in the suspension fibers. The Q-factor of the violin modes also exceeds 108. They have a ring-down time that is too long and may complicate the stable control of the interferometer. Results of the investigation of a violin mode active damping system are described. An original sensor and actuator were especially developed to realize the effective coupling of a thin, optically transparent, non-conducting fused silica fiber with an electric circuit. The damping system allowed the changing of the violin mode's damping rate over a wide range.

  7. Laser-induced periodic annular surface structures on fused silica surface

    SciTech Connect

    Liu, Yi; Brelet, Yohann; Forestier, Benjamin; Houard, Aurelien; Yu, Linwei; Deng, Yongkai; Jiang, Hongbing

    2013-06-24

    We report on the formation of laser-induced periodic annular surface structures on fused silica irradiated with multiple femtosecond laser pulses. This surface morphology emerges after the disappearance of the conventional laser induced periodic surface structures, under successive laser pulse irradiation. It is independent of the laser polarization and universally observed for different focusing geometries. We interpret its formation in terms of the interference between the reflected laser field on the surface of the damage crater and the incident laser pulse.

  8. Dynamics of organic compound extraction from water using liquid-coated fused silica fibers

    SciTech Connect

    Louch, D.; Motlagh, S.; Pawliszyn, J.

    1992-05-15

    Mathematical descriptions of the absorption and desorption processes were developed and compared with experimental results for solid-phase microextraction (SPME) using poly(dimethylsiloxane)-coated fused silica optical fibers. Extraction times for benzene, toluene, and p-xylene using a coating thickness of 55 {mu}m are under 10 min and can be shortened substantially using agitation. Detection limits and distribution coefficients for several organic compounds are presented. 20 refs., 13 figs., 1 tab.

  9. Theory of absorption rate of carriers in fused silica under intense laser irradiation

    SciTech Connect

    Deng, Hongxiang; Xiang, Xia; Zheng, WG; Yuan, XD; Wu, SY; Jiang, XD; Gao, Fei; Zu, Xiaotao T.; Sun, Kai

    2010-11-15

    A quantum non-perturbation theory for phonon-assisted photon absorption of conduction band electron in intense laser was developed. By carrying out the calculation in fused silica at wavelengths from ultraviolet to infrared in terawatt intensity laser, we show that the Non-perturbation approach can make a uniform description of energy absorption rate at both short wavelengths and long wavelengths on TW / cm2 intensity laser.

  10. Comparison of laser-based mitigation of fused silica surface damage using mid- versus far-infrared lasers

    SciTech Connect

    Yang, S T; Matthews, M J; Elhadj, S; Cooke, D; Guss, G M; Draggoo, V G; Wegner, P J

    2009-12-16

    Laser induced growth of optical damage can limit component lifetime and therefore operating costs of large-aperture fusion-class laser systems. While far-infrared (IR) lasers have been used previously to treat laser damage on fused silica optics and render it benign, little is known about the effectiveness of less-absorbing mid-IR lasers for this purpose. In this study, they quantitatively compare the effectiveness and efficiency of mid-IR (4.6 {micro}m) versus far-IR (10.6 {micro}m) lasers in mitigating damage growth on fused silica surfaces. The non-linear volumetric heating due to mid-IR laser absorption is analyzed by solving the heat equation numerically, taking into account the temperature-dependent absorption coefficient {alpha}(T) at {lambda} = 4.6 {micro}m, while far-IR laser heating is well-described by a linear analytic approximation to the laser-driven temperature rise. In both cases, the predicted results agree well with surface temperature measurements based on infrared radiometry, as well as sub-surface fictive temperature measurements based on confocal Raman microscopy. Damage mitigation efficiency is assessed using a figure of merit (FOM) relating the crack healing depth to laser power required, under minimally-ablative conditions. Based on their FOM, they show that for cracks up to at least 500 {micro}m in depth, mitigation with a 4.6 {micro}m mid-IR laser is more efficient than mitigation with a 10.6 {micro}m far-IR laser. This conclusion is corroborated by direct application of each laser system to the mitigation of pulsed laser-induced damage possessing fractures up to 225 {micro}m in depth.

  11. Comparing the use of mid-infrared versus far-infrared lasers for mitigating damage growth on fused silica

    SciTech Connect

    Yang, Steven T.; Matthews, Manyalibo J.; Elhadj, Selim; Cooke, Diane; Guss, Gabriel M.; Draggoo, Vaughn G.; Wegner, Paul J.

    2010-05-10

    Laser-induced growth of optical damage can limit component lifetime and, therefore, increase operating costs of large-aperture fusion-class laser systems. While far-infrared (IR) lasers have been used previously to treat laser damage on fused silica optics and render it benign, little is known about the effectiveness of less-absorbing mid-IR lasers for this purpose. In this study, we quantitatively compare the effectiveness and efficiency of mid-IR (4.6 {mu}m) versus far-IR (10.6 {mu}m) lasers in mitigating damage growth on fused silica surfaces. The nonlinear volumetric heating due to mid-IR laser absorption is analyzed by solving the heat equation numerically, taking into account the temperature-dependent absorption coefficient {alpha}(T) at {lambda}=4.6 {mu}m, while far-IR laser heating is well described by a linear analytic approximation to the laser-driven temperature rise. In both cases, the predicted results agree well with surface temperature measurements based on IR radiometry, as well as subsurface fictive temperature measurements based on confocal Raman microscopy. Damage mitigation efficiency is assessed using a figure of merit (FOM) relating the crack healing depth to laser power required, under minimally ablative conditions. Based on our FOM, we show that, for cracks up to at least 500 {mu}m in depth, mitigation with a 4.6 {mu}m mid-IR laser is more efficient than mitigation with a 10.6 {mu}m far-IR laser. This conclusion is corroborated by direct application of each laser system to the mitigation of pulsed laser-induced damage possessing fractures up to 225 {mu}m in depth.

  12. Single-Molecule Imaging of DNAs with Sticky Ends at Water/Fused Silica Interface

    SciTech Connect

    Slavica Isailovic

    2005-12-17

    Total internal reflection fluorescence microscopy (TIRFM) was used to study intermolecular interactions of DNAs with unpaired (sticky) ends of different lengths at water/fused silica interface at the single-molecule level. Evanescent field residence time, linear velocity and adsorption/desorption frequency were measured in a microchannel for individual DNA molecules from T7, Lambda, and PSP3 phages at various pH values. The longest residence times and the highest adsorption/desorption frequencies at the constant flow at pH 5.5 were found for PSP3 DNA, followed by lower values for Lambda DNA, and the lowest values for T7 DNA. Since T7, Lambda, and PSP3 DNA molecules contain none, twelve and nineteen unpaired bases, respectively, it was concluded that the affinity of DNAs for the surface increases with the length of the sticky ends. This confirms that hydrophobic and hydrogen-bonding interactions between sticky ends and fused-silica surface are driving forces for DNA adsorption at the fused-silica surface. Described single-molecule methodology and results therein can be valuable for investigation of interactions in liquid chromatography, as well as for design of DNA hybridization sensors and drug delivery systems.

  13. 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.

  14. 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.

  15. Effects of wet etch processing on laser-induced damage of fused silica surfaces

    SciTech Connect

    Battersby, C.L.; Kozlowski, M.R.; Sheehan, L.M.

    1998-12-22

    Laser-induced damage of transparent fused silica optical components by 355 nm illumination occurs primarily at surface defects produced during the grinding and polishing processes. These defects can either be surface defects or sub-surface damage.Wet etch processing in a buffered hydrogen fluoride (HF) solution has been examined as a tool for characterizing such defects. A study was conducted to understand the effects of etch depth on the damage threshold of fused silica substrates. The study used a 355 nm, 7.5 ns, 10 Hz Nd:YAG laser to damage test fused silica optics through various wet etch processing steps. Inspection of the surface quality was performed with Nomarski microscopy and Total Internal Reflection Microscopy. The damage test data and inspection results were correlated with polishing process specifics. The results show that a wet etch exposes subsurface damage while maintaining or improving the laser damage performance. The benefits of a wet etch must be evaluated for each polishing process.

  16. Heat accumulation regime of femtosecond laser writing in fused silica and Nd:phosphate glass

    NASA Astrophysics Data System (ADS)

    Bukharin, M. A.; Khudyakov, D. V.; Vartapetov, S. K.

    2015-04-01

    We investigated refractive index induced by direct femtosecond laser writing inside fused silica and Nd:phosphate glass in heat accumulation regime. Spatial profile and magnitude of induced refractive index were investigated at various pulse repetition rates and translation velocities. It was shown that the magnitude of induced refractive index significantly rises with decreasing in time interval between successive laser pulses below the time for thermal diffusion. Going from nonthermal regime to heat accumulation regime, we achieved induced refractive index growth from 4 × 10-3 up to 6.5 × 10-3 in fused silica and from -6 × 10-3 to -9 × 10-3 in Nd:phosphate glass. Aspect ratio of treated area decreased from 2.1 down to less than 1.5 without correcting optical elements. It was shown that in heat accumulation regime, the treated area was surrounded by region of alternatively changed refractive index with significant magnitude up to -2 × 10-3. Wide regions of decreased refractive index enable fabrication of depressed cladding waveguides. We demonstrated low-loss (0.3 dB/cm) tubular waveguide inside fused silica. For orthogonal polarizations of guiding light, we achieved a small difference between losses as 0.1 dB/cm using highly symmetric written tracks forming the cladding. The desired structure was simulated with the beam propagation method, and the results were in good agreement with experiment data.

  17. Ultradeep fused silica glass etching with an HF-resistant photosensitive resist for optical imaging applications

    NASA Astrophysics Data System (ADS)

    Nagarah, John M.; Wagenaar, Daniel A.

    2012-03-01

    Microfluidic and optical sensing platforms are commonly fabricated in glass and fused silica (quartz) because of their optical transparency and chemical inertness. Hydrofluoric acid (HF) solutions are the etching media of choice for deep etching into silicon dioxide substrates, but processing schemes become complicated and expensive for etching times greater than 1 h due to the aggressiveness of HF migration through most masking materials. We present here etching into fused silica more than 600 µm deep while keeping the substrate free of pits and maintaining a polished etched surface suitable for biological imaging. We utilize an HF-resistant photosensitive resist (HFPR) which is not attacked in 49% HF solution. Etching characteristics are compared for substrates masked with the HFPR alone and the HFPR patterned on top of Cr/Au and polysilicon masks. We used this etching process to fabricate suspended fused silica membranes, 8-16 µm thick, and show that imaging through the membranes does not negatively affect image quality of fluorescence microscopy of biological tissue. Finally, we realize small through-pore arrays in the suspended membranes. Such devices will have applications in planar electrophysiology platforms, especially where optical imaging is required.

  18. Precision drilling of fused silica with 157-nm excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, Klaus

    2003-07-01

    μFor drilling fused silica, mechanical techniques like with diamond drills, ultrasonic machining, sand blasting or water jet machining are used. Also chemical techniques like laser assisted wet etching or thermal drilling with CO2-lasers are established. As an extension of these technologies, the drilling of micro-holes in fused silica with VUV laser radiation is presented here. The high absorption of the 157 nm radiation emitted by the F2 excimer laser and the short pulse duration lead to a material ablation with minimised impact on the surrounding material. Contrary to CO2-laser drilling, a molten and solidified phase around the bore can thus be avoided. The high photon energy of 7.9 eV requires either high purity nitrogen flushing or operation in vacuum, which also effects the processing results. Depending on the required precision, the laser can be used for percussion drilling as well as for excimer laser trepanning, by applying rotating masks. Rotating masks are especially used for high aspect ratio drilling with well defined edges and minimised debris. The technology is suitable particularly for holes with a diameter below 200 μm down to some microns in substrates with less than 200 μm thickness, that can not be achieved with mechanical methods. Drilling times in 200 μm fused silica substrates are in the range of ten seconds, which is sufficient to compete with conventional methods while providing similar or even better accuracy.

  19. Influence of piezoceramic to fused silica plate thickness on the radii of curvature of piezoelectric bimorph mirror

    NASA Astrophysics Data System (ADS)

    Libu, M.; Susanth, S.; Vasanthakumari, K. G.; Dileep Kumar, C. J.; Raghu, N.

    2012-01-01

    Piezoelectric based bimorph mirrors (PBM) find extensive use in focusing of x-ray beams. Many optical instruments require use of PBM whose radii of curvature can be tuned precisely. The 100 mm and 300 mm PBMs were fabricated with varying piezoelectric to fused silica plate thicknesses. The radii of curvature of free standing mirrors were measured as a function of voltage and it was found to decrease with increasing voltage. For a given piezoelectric plate thickness, as the fused silica thickness increases, the radii of curvature was found to increase owing to increase in stiffness of the mirror. On the other hand, for a given fused silica plate thickness, when the piezoelectric plate thickness is increased, the radii of curvature are decreased for a given electric field, due to increase in generated force. This study brings out the influence of piezoceramic to fused silica plate thickness on the radii of curvature of PBM.

  20. A new method for synthesizing fluid inclusions in fused silica capillaries containing organic and inorganic material

    USGS Publications Warehouse

    Chou, I.-Ming; Song, Y.; Burruss, R.C.

    2008-01-01

    Considerable advances in our understanding of physicochemical properties of geological fluids and their roles in many geological processes have been achieved by the use of synthetic fluid inclusions. We have developed a new method to synthesize fluid inclusions containing organic and inorganic material in fused silica capillary tubing. We have used both round (0.3 mm OD and 0.05 or 0.1 mm ID) and square cross-section tubing (0.3 ?? 0.3 mm with 0.05 ?? 0.05 mm or 0.1 ?? 0.1 mm cavities). For microthermometric measurements in a USGS-type heating-cooling stage, sample capsules must be less than 25 mm in length. The square-sectioned capsules have the advantage of providing images without optical distortion. However, the maximum internal pressure (P; about 100 MPa at 22 ??C) and temperature (T; about 500 ??C) maintained by the square-sectioned capsules are less than those held by the round-sectioned capsules (about 300 MPa at room T, and T up to 650 ??C). The fused silica capsules can be applied to a wide range of problems of interest in fluid inclusion and hydrothermal research, such as creating standards for the calibration of thermocouples in heating-cooling stages and frequency shifts in Raman spectrometers. The fused silica capsules can also be used as containers for hydrothermal reactions, especially for organic samples, including individual hydrocarbons, crude oils, and gases, such as cracking of C18H38 between 350 and 400 ??C, isotopic exchanges between C18H38 and D2O and between C19D40 and H2O at similar temperatures. Results of these types of studies provide information on the kinetics of oil cracking and the changes of oil composition under thermal stress. When compared with synthesis of fluid inclusions formed by healing fractures in quartz or other minerals or by overgrowth of quartz at elevated P-T conditions, the new fused-silica method has the following advantages: (1) it is simple; (2) fluid inclusions without the presence of water can be formed; (3

  1. Laser-welded fused silica substrates using a luminescent fresnoite-based sealant

    NASA Astrophysics Data System (ADS)

    de Pablos-Martin, A.; Benndorf, G.; Tismer, S.; Mittag, M.; Cismak, A.; Lorenz, M.; Grundmann, M.; Höche, Th.

    2016-06-01

    The laser welding of two fused silica substrates using a fresnoitic glass thin film as a sealant by irradiation with a ns laser is studied. Two different laser parameter sets were compared in terms of bond quality, which include two different laser beam trajectories: linear and wobble (circular) trajectory. The composition of the glass sealant changes with the course of the laser welding, incorporating silica from the substrates. After joining, the bonded samples were exposed to UV light and a very intense emission in the blue spectral range is observed by naked eye, which is due to the crystallization of the fresnoite glass upon the laser irradiation. EDX analysis confirms the crystallization of fresnoite, together with a great enrichment in silica. The formation of a eutectic between both is very plausible. Bond quality and bond strength were evaluated by scanning acoustic microscopy (SAM) and tensile test, which results in a tensile stress of 7 MPa.

  2. Bond strength of composites to etched and silica-coated porcelain fusing alloys.

    PubMed

    Schneider, W; Powers, J M; Pierpont, H P

    1992-05-01

    In vitro bond strengths of two composite veneering materials to two porcelain fusing alloys were measured utilizing two storage conditions. The alloys were etched or treated with silica applied by blasted, thermal or pyrogenic techniques and then silanated. Bond strengths were higher for the Ni-Cr-Be than the Au-Pd alloy with most values greater than 18 MPa. Bond strengths to etched and silanated Au-Pd alloy were low (less than 6.5 MPa), whereas samples treated with silica and silanated had significantly higher values. Bond strengths to the Ni-Cr-Be alloy were highest with the thermal and pyrogenic silica treatments. After thermocycling, most bond strengths to the Au-Pd alloy decreased, but were the same or higher to the Ni-Cr-Be alloy. Cohesive failures of the opaquers were observed. PMID:1325930

  3. Thermal transport in CO2 laser irradiated fused silica: in situ measurements and analysis

    SciTech Connect

    Yang, S T; Matthews, M J; Elhadj, S; Draggoo, V G; Bisson, S E

    2009-07-07

    In situ spatial and temporal temperature measurements of pristine fused silica surfaces heated with a 10.6 {micro}m CO{sub 2} laser were obtained using an infrared radiation thermometer based on a Mercury Cadmium Telluride (MCT) camera. Laser spot sizes ranged from 250 {micro}m to 1000 {micro}m diameter with peak axial irradiance levels of 0.13 to 16 kW/cm{sup 2}. For temperatures below 2800K, the measured steady-state surface temperature is observed to rise linearly with both increasing beam size and incident laser irradiance. The effective thermal conductivity estimated over this range was approximately 2W/mK, in good agreement with classical calculations based on phonon heat capacities. Similarly, time-dependent temperature measurements up to 2000K yielded thermal diffusivity values which were close to reported values of 7 x 10{sup -7} m{sup 2}/s. Above {approx}2800K, the fused silica surface temperature asymptotically approaches 3100K as laser power is further increased, consistent with the onset of evaporative heat losses near the silica boiling point. These results show that in the laser heating regime studied here, the T{sup 3} temperature dependent thermal conductivity due to radiation transport can be neglected, but at temperatures above 2800K heat transport due to evaporation must be considered. The thermal transport in fused silica up to 2800K, over a range of conditions, can then be adequately described by a linear diffusive heat equation assuming constant thermal properties.

  4. Very high Q measurements on a fused silica monolithic pendulum for use in enhanced gravity wave detectors

    PubMed

    Cagnoli; Gammaitoni; Hough; Kovalik; McIntosh; Punturo; Rowan

    2000-09-18

    We present for the first time the results of very high Q factor measurements for a 2.8 kg fused silica mass suspended by two fused quartz fibers attached by a novel technique for joining fused silica or quartz. The Q for the pendulum mode at 0.93 Hz was (2.3+/-0. 2)x10(7), the highest value demonstrated to date for a mass of this size. By employing such a new suspension system the sensitivity of the gravitational wave detectors currently under construction can be increased up to 1 order of magnitude. PMID:10978077

  5. CO/sub 2/-laser polishing of fused silica surfaces for increased laser damage resistance at 1. 06. mu. m

    SciTech Connect

    Temple, P.A.; Milam, D.; Lowdermilk, W.H.

    1980-04-03

    Bare fused silica surfaces were prepared by subjecting the mechanically polished surface to a rastered cw CO/sub 2/ laser beam. Analysis shows that this processing causes: (a) removal of a uniform layer of fused silica; and (b) a probable re-fusing or healing of existing subsurface fractures. The fused silica removal rate is found to be a function of the laser intensity and scan rate. These surfaces are seen to have very low scatter and to be very smooth. In addition, they have exhibited entrance surface damage thresholds at 1.06 ..mu..m, and 1 nsec, which are substantially above those seen on the mechanically polished surface. When damage does occur, it tends to be at a few isolated points rather than the general uniform damage seen on the mechanicaly polished part. In addition to the damage results, we will discuss an observational technique used for viewing these surfaces which employs dark-field illumination.

  6. Surface roughening of ground fused silica processed by atmospheric inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Xin, Qiang; Li, Na; Wang, Jun; Wang, Bo; Li, Guo; Ding, Fei; Jin, Huiliang

    2015-06-01

    Subsurface damage (SSD) is a defect that is inevitably induced during mechanical processes, such as grinding and polishing. This defect dramatically reduces the mechanical strength and the laser damage thresholds of optical elements. Compared with traditional mechanical machining, atmospheric pressure plasma processing (APPP) is a relatively novel technology that induces almost no SSD during the processing of silica-based optical materials. In this paper, a form of APPP, inductively coupled plasma (ICP), is used to process fused silica substrates with fluorocarbon precursor under atmospheric pressure. The surface morphology evolution of ICP-processed substrates was observed and characterized by confocal laser scanning microscope (CLSM), field emission scanning electron microscope (SEM), and atomic force microscopy (AFM). The results show that the roughness evolves with the etching depth, and the roughness evolution is a single-peaked curve. This curve results from the opening and the coalescing of surface cracks and fractures. The coalescence procedure of these microstructures was simulated with two common etched pits on a polished fused silica surface. Understanding the roughness evolution of plasma-processed surface might be helpful in optimizing the optical fabrication chain that contains APPP.

  7. 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.

  8. Role of suprathermal electrons during nanosecond laser energy deposit in fused silica

    SciTech Connect

    Grua, P.; Hébert, D.; Lamaignère, L.; Rullier, J.-L.

    2014-08-25

    An accurate description of interaction between a nanosecond laser pulse and a wide band gap dielectric, such as fused silica, requires the understanding of energy deposit induced by temperature changes occurring in the material. In order to identify the fundamental processes involved in laser-matter interaction, we have used a 1D computational model that allows us to describe a wide set of physical mechanisms and intended for comparison with specially designed “1D experiments.” We have pointed out that suprathermal electrons are very likely implicated in heat conduction, and this assumption has allowed the model to reproduce the experiments.

  9. Subsurface mechanical damage during bound abrasive grinding of fused silica glass

    NASA Astrophysics Data System (ADS)

    Blaineau, P.; André, D.; Laheurte, R.; Darnis, P.; Darbois, N.; Cahuc, O.; Neauport, J.

    2015-10-01

    The subsurface damage (SSD) introduced during bound abrasive grinding of fused silica glass was measured using a wet etch technique. Various process parameters and grinding configurations were studied. The relation between the SSD depth, the process parameters and forces applied by the grinding wheel on the sample was investigated and compared to a simulation using a discrete element method to model the grinding interface. The results reveal a relation between the SSD depth and the grinding forces normalized by the abrasive concentration. Regarding the creation of the SSD, numerical simulations indicate that only a small fraction of the largest particles in the diamond wheel are responsible for the depth of the damaged layer.

  10. Interferometric measurement of the temperature dependence of an index of refraction: application to fused silica.

    PubMed

    Dupouy, Paul-Edouard; Büchner, Matthias; Paquier, Philippe; Trénec, Gérard; Vigué, Jacques

    2010-02-01

    The light reflected by an uncoated Fabry-Perot etalon presents dark rings which give a very sensitive measurement of the variations of the return optical path in the etalon. By measuring the diameters of these rings as a function of the etalon temperature T, we get a sensitive measurement of the derivative dn/dT of the index of refraction n. We have made this experiment with a fused silica etalon and we have achieved a 2% relative uncertainty on dn/dT, comparable to the uncertainty of the best experiments. PMID:20119019

  11. Gas bubble formation in fused silica generated by ultra-short laser pulses.

    PubMed

    Cvecek, Kristian; Miyamoto, Isamu; Schmidt, Michael

    2014-06-30

    During processing of glass using ultra-fast lasers the formation of bubble-like structures can be observed in several glass types such as fused silica. Their formation can be exploited to generate periodic gratings in glasses but for other glass processing techniques such as waveguide-writing or glass welding by ultra-fast lasers the bubble formation proves often detrimental. In this work we present experiments and their results in order to gain understanding of the origins and on the underlying formation and transportation mechanisms of the gas bubbles. PMID:24977843

  12. Growth of laser damage in fused silica: diameter to depth ratio

    SciTech Connect

    Norton, M A; Adams, J J; Carr, C W; Donohue, E E; Feit, M D; Hackel, R P; Hollingsworth, W G; Jarboe, J A; Matthews, M; Rubenchik, A M; Spaeth, M L

    2007-10-29

    Growth of laser initiated damage plays a major role in determining optics lifetime in high power laser systems. Previous measurements have established that the lateral diameter grows exponentially. Knowledge of the growth of the site in the propagation direction is also important, especially so when considering techniques designed to mitigate damage growth, where it is required to reach all the subsurface damage. In this work, we present data on both the diameter and the depth of a growing exit surface damage sites in fused silica. Measured growth rates with both 351 nm illumination and with combined 351 nm and 1054 nm illumination are discussed.

  13. Growth of laser initiated damage in fused silica at 1053 nm

    SciTech Connect

    Norton, M A; Donohue, E E; Hollingsworth, W G; Feit, M D; Rubenchik, A M; Hackel, R P

    2004-11-10

    The effective lifetime of a laser optic is limited by both laser-induced damage and the subsequent growth of laser initiated damage sites. We have measured the growth rate of laser-induced damage on polished fused silica surfaces in 10 torr of air at 1053 nm at 10 ns. The data shows exponential growth in the lateral size of the damage site with shot number above a threshold fluence. The size of the initial damage influences the threshold for growth. We will compare the growth rates for input and output surface damage. Possible reasons for the observed growth behavior are discussed.

  14. 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

  15. Dimensional stability of fused silica, Invar, and several ultralow thermal expansion materials

    NASA Technical Reports Server (NTRS)

    Berthold, J. W., III; Jacobs, S. F.; Norton, M. A.

    1976-01-01

    A method is developed for testing the long-term dimensional stability of an iodine-stabilized He-Ne laser, using a technique whereby thermal expansion coefficients are measured by forming a Fabry-Perot etalon from the sample and monitoring the optical resonant frequencies with tunable sidebands impressed on a laser beam from a frequency-stabilized He-Ne laser. A change of 1 ppm over a 3-yr period on the part of fused silica dimensions and the differential thermal expansion of Invar LR-35 and Super Invar materials are noted. The method is of interest for the metrology of extremely stable structures such as telescopes and optical resonators.

  16. Large-Scale Synthesis and Systematic Photoluminescence Properties of Monolayer MoS2 on Fused Silica.

    PubMed

    Wan, Yi; Zhang, Hui; Zhang, Kun; Wang, Yilun; Sheng, Bowen; Wang, Xinqiang; Dai, Lun

    2016-07-20

    Monolayer MoS2, with fascinating mechanical, electrical, and optical properties, has generated enormous scientific curiosity and industrial interest. Controllable and scalable synthesis of monolayer MoS2 on various desired substrates has significant meaning in both basic scientific research and device application. Recent years have witnessed many advances in the direct synthesis of single-crystalline MoS2 flakes or their polycrystalline aggregates on numerous diverse substrates, such as SiO2-Si, mica, sapphire, h-BN, and SrTiO3, etc. In this work, we used the dual-temperature-zone atmospheric-pressure chemical vapor deposition method to directly synthesize large-scale monolayer MoS2 on fused silica, the most ordinary transparent insulating material in daily life. We systematically investigated the photoluminescence (PL) properties of monolayer MoS2 on fused silica and SiO2-Si substrates, which have different thermal conductivity coefficients and thermal expansion coefficients. We found that there exists a stronger strain on monolayer MoS2 grown on fused silica, and the strain becomes more obvious as temperature decreases. Moreover, the monolayer MoS2 grown on fused silica exhibits the unique trait of a fractal shape with tortuous edges and has stronger adsorbability. The monolayer MoS2 grown on fused silica may find application in sensing, energy storage, and transparent optoelectronics, etc. PMID:27338112

  17. Downstream Intensification Effects Associated with CO2 Laser Mitigation of Fused Silica

    SciTech Connect

    Matthews, M J; Bass, I L; Guss, G M; Widmayer, C C; Ravizza, F L

    2007-10-29

    Mitigation of 351nm laser-induced damage sites on fused silica exit surfaces by selective CO{sub 2} treatment has been shown to effectively arrest the exponential growth responsible for limiting the lifetime of optics in high-fluence laser systems. However, the perturbation to the optical surface profile following the mitigation process introduces phase contrast to the beam, causing some amount of downstream intensification with the potential to damage downstream optics. Control of the laser treatment process and measurement of the associated phase modulation is essential to preventing downstream 'fratricide' in damage-mitigated optical systems. In this work we present measurements of the surface morphology, intensification patterns and damage associated with various CO{sub 2} mitigation treatments on fused silica surfaces. Specifically, two components of intensification pattern, one on-axis and another off-axis can lead to damage of downstream optics and are related to rims around the ablation pit left from the mitigation process. It is shown that control of the rim structure around the edge of typical mitigation sites is crucial in preventing damage to downstream optics.

  18. Molecular dynamics simulation of shock induced ejection on fused silica surface

    SciTech Connect

    Su, Rui; Xiang, Meizhen; Jiang, Shengli; Chen, Jun; Wei, Han

    2014-05-21

    Shock response and surface ejection behaviors of fused silica are studied by using non-equilibrium molecular dynamics combining with the Tersoff potential. First, bulk structure and Hugoniot curves of fused silica are calculated and compared with experimental results. Then, the dynamical process of surface ejection behavior is simulated under different loading velocities ranging from 3.5 to 5.0 km∕s, corresponding to shock wave velocities from 7.1 to 8.8 km∕s. The local atomistic shear strain parameter is used to describe the local plastic deformation under conditions of shock compression or releasing. Our result shows that the shear strain is localized in the bottom area of groove under the shock compression. Surface ejection is observed when the loading velocity exceeds 4.0 km∕s. Meanwhile, the temperature of the micro-jet is ∼5574.7 K, which is close to experiment measurement. Several kinds of structural defects including non-bridging oxygen are found in the bulk area of the sample after ejection.

  19. Time-resolved transmission study of fused silica during laser-induced backside dry etching

    NASA Astrophysics Data System (ADS)

    Smausz, T.; Zalatnai, Z.; Papdi, B.; Csákó, T.; Bor, Zs.; Hopp, B.

    2009-03-01

    Laser-induced backside dry etching (LIBDE) is a promising technique for micro- and nanomachining of transparent materials. Although several experiments have already proved the suitability and effectiveness of the technique, there are several open questions concerning the etching mechanism and the concomitant processes. In this paper time-resolved light transmission investigations of etching process of fused silica are presented. 125 nm thick silver coating was irradiated through the carrying 1 mm thick fused silica plate by single pulses of a nanosecond KrF excimer laser. The applied fluences were 0.38, 0.71 and 1 J/cm 2. During the etching process the irradiated spots were illuminated by an electronically delayed nitrogen laser pumped dye laser. The delay between the pump and probe pulses was varied in the range of 0 ns and 20 μs. It was found that the transmitted probe beam intensity strongly depends on the applied delays and fluences. Scanning electron microscopy and energy dispersive X-ray spectrometry of the etched surface showed the existence of silver droplets and fragments on the illuminated surfaces and silver atoms built into the treated surface layer influencing the transmission behavior of the studied samples.

  20. Formation of conical emission of supercontinuum during filamentation of femtosecond laser radiation in fused silica

    NASA Astrophysics Data System (ADS)

    Kandidov, V. P.; Smetanina, E. O.; Dormidonov, A. E.; Kompanets, V. O.; Chekalin, S. V.

    2011-09-01

    The formation of conical emission of supercontinuum during filamentation of femtosecond laser pulses with central wavelengths in a wide range is studied experimentally, numerically, and analytically. The frequency-angular intensity distribution of the spectral components of conical emission is determined by the interference of supercontinuum emission in a filament of a femtosecond laser pulse. The interference of supercontinuum emission has a general character, exists at different regimes of group velocity dispersion, gives rise to the fine spectral structure after the pulse splitting into subpulses and the formation of a distributed supercontinuum source in an extended filament, and causes the decomposition of the continuous spectrum of conical emission into many high-contrast maxima after pulse refocusing in the filament. In spectroscopic studies with a tunable femtosecond radiation source based on a TOPAS parametric amplifier, we used an original scheme with a wedge fused silica sample. Numerical simulations have been performed using a system of equations of nonlinear-optical interaction of laser radiation under conditions of diffraction, wave nonstationarity, and material dispersion in fused silica. The analytic study is based on the interference model of formation of conical emission by supercontinuum sources moving in a filament.

  1. Formation of conical emission of supercontinuum during filamentation of femtosecond laser radiation in fused silica

    SciTech Connect

    Kandidov, V. P. Smetanina, E. O.; Dormidonov, A. E.; Kompanets, V. O.; Chekalin, S. V.

    2011-09-15

    The formation of conical emission of supercontinuum during filamentation of femtosecond laser pulses with central wavelengths in a wide range is studied experimentally, numerically, and analytically. The frequency-angular intensity distribution of the spectral components of conical emission is determined by the interference of supercontinuum emission in a filament of a femtosecond laser pulse. The interference of supercontinuum emission has a general character, exists at different regimes of group velocity dispersion, gives rise to the fine spectral structure after the pulse splitting into subpulses and the formation of a distributed supercontinuum source in an extended filament, and causes the decomposition of the continuous spectrum of conical emission into many high-contrast maxima after pulse refocusing in the filament. In spectroscopic studies with a tunable femtosecond radiation source based on a TOPAS parametric amplifier, we used an original scheme with a wedge fused silica sample. Numerical simulations have been performed using a system of equations of nonlinear-optical interaction of laser radiation under conditions of diffraction, wave nonstationarity, and material dispersion in fused silica. The analytic study is based on the interference model of formation of conical emission by supercontinuum sources moving in a filament.

  2. Depth profiling of polishing-induced contamination on fused silica surfaces

    SciTech Connect

    Kozlowski, M.R.; Carr, J.; Hutcheon, I,; Torres, R.; Sheehan, L. Camp, D.; Yan, M.

    1997-12-20

    Laser-induced damage on optical surfaces is often associated with absorbing contaminants introduced by the polishing process. This is particularly the case for UV optics. Here secondary ion mass spectroscopy (SIMS) was used to measure depth profiles of finished process contamination on fused silica surfaces. Contaminants detected include the major polishing compound components (Ce or Zr from CeO2 or ZrO2), Al presently largely because of the use of Al2O3 in the final cleaning process (Fe, Cu,Cr) incorporated during the polishing step or earlier grinding steps. Depth profile data typically showed an exponential decay of contaminant concentration to a depth of 100-200 nm. This depth is consistent with a polishing redeposition layers formed during the chemo-mechanical polishing of fused silica. Peak contaminant levels are typically in the 10-100 ppm range, except for Al with exceeds 1000 ppm. A strong correlation has been shown between the presence of a gray haze damage morphology and the use of CeO2 polishing compound. No strong correlation was found however between high levels of Ce, or any other contaminant and the low damage threshold was observed. In fact one of the strongest indications of a correlation is between increased damage thresholds and increased Zr contamination. This suggests that the correlation between redeposition layer and laser damage threshold is not simple an absorbing contaminant issue.

  3. Laser beam shape converter using spatially variable waveplate made by nanogratings inscription in fused silica

    NASA Astrophysics Data System (ADS)

    Gertus, T.; Michailovas, A.; Michailovas, K.; PetrauskienÄ--, V.

    2015-03-01

    In this work we present a beam shaping technique based on a spatially variable phase retardation plate inscribed inside bulk of fused silica glass by femtosecond laser pulses. Formation of self-assembled periodic nanostructures was exploited to fabricate the converter. During the fabrication process we control induced nanogratings orientation and retardance. Combination of a spatially variable waveplate and a polarizer acts as a spatially variable transmission filter. With a converter fabricated to transform an initially Gaussian beam to a flat-top beam we preserve more than 50% of initial laser power. Theoretically, the efficiency of the proposed converter could be up to 70%. The proposed converter with no absorbing elements possesses resistance to optical damage similar to that of fused silica. Additionally, the already-fabricated converter allows for on-the-fly adjustment of the beam shape from flat-top to a shape with a dip in the middle. The shaped beam was tested in a high power picosecond pulse amplifier.

  4. Morphology evolution of fused silica surface during ion beam figuring of high-slope optical components.

    PubMed

    Liao, Wenlin; Dai, Yifan; Xie, Xuhui; Zhou, Lin

    2013-06-01

    Ultra-precision and ultra-smooth surfaces are vitally important for some high performance optical systems. Ion beam figuring (IBF) is a well-established, highly deterministic method for the final precision figuring of extremely high quality optical surfaces, whereas ion sputtering induced smoothing, or roughening for nanoscale surface morphology, strongly depends on the processing conditions. Usually, an improper machining method would arouse the production of nanoscale patterns leading to the coarsening of the optical surface. In this paper, the morphology evolution mechanism on a fused silica surface during IBF of high-slope optical components has been investigated by means of atomic force microscopy. Figuring experiments are implemented on two convex spherical surfaces by using different IBF methods. Both of their surface errors are rapidly reduced to 1.2 nm root mean square (RMS) after removing similar deep material, but their surfaces are characterized with obviously different nanoscale morphologies. The experimental results indicate that the ion incidence angle dominates the microscopic morphology during the IBF process. At near-normal incidence, fused silica achieves an ultra-smooth surface with an RMS roughness value R(q) down to 0.1 nm, whereas nanoscale ripple patterns are observed at a large incidence angle with an R(q) value increasing to more than 0.9 nm. Additionally, the difference of incidence angles on various machined areas would influence the uniformity of surface quality, resulting from the interplay between the smoothing and roughening effects induced by ion sputtering. PMID:23736325

  5. High power laser antireflection subwavelength grating on fused silica by colloidal lithography

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Huang, Jin; Geng, Feng; Liu, Hongjie; Sun, Laixi; Yan, Lianghong; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo

    2016-07-01

    In this study we report on an efficient and simple method to fabricate an antireflection subwavelength grating on a fused silica substrate using two-step reactive ion etching with monolayer polystyrene colloidal crystals as masks. We show that the period and spacing of the obtained subwavelength grating were determined by the initial diameter of polystyrene microspheres and the oxygen ion etching duration. The height of pillar arrays can be adjusted by tuning the second-step fluorine ion etching duration. These parameters are proved to be useful in tailoring the antireflection properties of subwavelength grating using a finite-difference time-domain (FDTD) method and effective medium theory. The subwavelength grating exhibits excellent antireflection properties. The near-field distribution of the SWG which is directly patterned into the substrate material is performed by a 3D-FDTD method. It is found that the near-field distribution is strongly dependent on the periodicity of surface structure, which has the potential to promote the ability of anti-laser-induced damage. For 10 ns pulse duration and 1064 nm wavelength, we experimentally determined their laser induced damage threshold to 32 J cm‑2, which is nearly as high as bulk fused silica with 31.5 J cm‑2.

  6. Laser-induced damage initiated on the surface of particle contamination fused silica at 1064nm

    SciTech Connect

    Michlitsch, K.J.

    1998-06-01

    An experimental study was undertaken to quantify the effects of contamination particles on the damage threshold of laser-illuminated fused silica optics and set cleanliness requirements for optics on the beam line of the National Ignition Facility at Lawrence Livermore National Laboratory. Circular contamination particles were sputter-deposited onto fused silica windows which were then illuminated repetitively using a 1064nm laser. A variety of contaminants were tested including metals, oxides, and organics. Tests were conducted with particles on the input and output surfaces of the window, and the morphological features of the damage were very reproducible. A plasma often ignited at the contamination particle; its intensity was dependent upon the mass of the contaminant. Input surface damage was characteristically more severe than output surface damage. The size of the damaged area scaled with the size of the particle. On a few occasions, catastrophic damage (cracking or ablation of the substrate) initiated on the output surface due to contamination particles on either the input or output surface. From damage growth plots, predictions can be made about the severity of damage expected from contamination particles of known size and material.

  7. Monitoring annealing via carbon dioxide laser heating of defect populations in fused silica surfaces using photoluminescence microscopy

    SciTech Connect

    Raman, R N; Matthews, M J; Adams, J J; Demos, S G

    2010-02-01

    Photoluminescence (PL) microscopy and spectroscopy under 266 nm and 355 nm laser excitation are explored as a means of monitoring defect populations in laser-modified sites on the surface of fused silica and their subsequent response to heating to different temperatures via exposure to a CO{sub 2} laser beam. Laser-induced temperature changes were estimated using an analytic solution to the heat flow equation and compared to changes in the PL emission intensity. The results indicate that the defect concentrations decrease significantly with increasing CO{sub 2} laser exposure and are nearly eliminated when the peak surface temperature exceeds the softening point of fused silica ({approx}1900K), suggesting that this method might be suitable for in situ monitoring of repair of defective sites in fused silica optical components.

  8. Investigation of surface characteristics evolution and laser damage performance of fused silica during ion-beam sputtering

    NASA Astrophysics Data System (ADS)

    Xu, Mingjin; Dai, Yifan; Zhou, Lin; Shi, Feng; Wan, Wen; Xie, Xuhui; Sui, Tingting

    2016-08-01

    Surface characteristics have great influence on the optical properties especially the laser radiation resistivity of optics. In this paper, the surface characteristics evolutions of fused silica during ion-beam sputtering and their effects on the laser damage performance were investigated. The results show that roughness change is strongly removal depth dependent and a super-smooth surface (0.25 nm RMS) can be obtained by the ion-induced smoothing effect. The concentration of metal impurities (especially Ce element) in subsurface can be effectively decreased after the removal of polishing re-deposition layer. During ion-beam sputtering process, the plastic scratches can be removed while the brittle cracks can be broadened and passivated without increase in the depth direction. Laser damage threshold of fused silica improved by 36% after ion-beam sputtering treatment. Research results have a guiding significance for ion-beam sputtering process technology of fused silica optics.

  9. The effect of high-pressure devitrification and densification on ballistic-penetration resistance of fused silica

    NASA Astrophysics Data System (ADS)

    Avuthu, Vasudeva Reddy

    Despite the clear benefits offered by more advanced transparent materials, (e.g. transparent ceramics offer a very attractive combination of high stiffness and high hardness levels, highly-ductile transparent polymers provide superior fragment-containing capabilities, etc.), ballistic ceramic-glass like fused-silica remains an important constituent material in a majority of transparent impact-resistant structures (e.g. windshields and windows of military vehicles, portholes in ships, ground vehicles and spacecraft) used today. Among the main reasons for the wide-scale use of glass, the following three are most frequently cited: (i) glass-structure fabrication technologies enable the production of curved, large surface-area, transparent structures with thickness approaching several inches; (ii) relatively low material and manufacturing costs; and (iii) compositional modifications, chemical strengthening, and controlled crystallization have been demonstrated to be capable of significantly improving the ballistic properties of glass. In the present work, the potential of high-pressure devitrification and densification of fused-silica as a ballistic-resistance-enhancement mechanism is investigated computationally. In the first part of the present work, all-atom molecular-level computations are carried out to infer the dynamic response and material microstructure/topology changes of fused silica subjected to ballistic impact by a nanometer-sized hard projectile. The analysis was focused on the investigation of specific aspects of the dynamic response and of the microstructural changes such as the deformation of highly sheared and densified regions, and the conversion of amorphous fused silica to SiO2 crystalline allotropic modifications (in particular, alpha-quartz and stishovite). The microstructural changes in question were determined by carrying out a post-processing atom-coordination procedure. This procedure suggested the formation of high-density stishovite (and

  10. Invited Article: CO2 laser production of fused silica fibers for use in interferometric gravitational wave detector mirror suspensions

    NASA Astrophysics Data System (ADS)

    Heptonstall, A.; Barton, M. A.; Bell, A.; Cagnoli, G.; Cantley, C. A.; Crooks, D. R. M.; Cumming, A.; Grant, A.; Hammond, G. D.; Harry, G. M.; Hough, J.; Jones, R.; Kelley, D.; Kumar, R.; Martin, I. W.; Robertson, N. A.; Rowan, S.; Strain, K. A.; Tokmakov, K.; van Veggel, M.

    2011-01-01

    In 2000 the first mirror suspensions to use a quasi-monolithic final stage were installed at the GEO600 detector site outside Hannover, pioneering the use of fused silica suspension fibers in long baseline interferometric detectors to reduce suspension thermal noise. Since that time, development of the production methods of fused silica fibers has continued. We present here a review of a novel CO_2 laser-based fiber pulling machine developed for the production of fused silica suspensions for the next generation of interferometric gravitational wave detectors and for use in experiments requiring low thermal noise suspensions. We discuss tolerances, strengths, and thermal noise performance requirements for the next generation of gravitational wave detectors. Measurements made on fibers produced using this machine show a 0.8% variation in vertical stiffness and 0.05% tolerance on length, with average strengths exceeding 4 GPa, and mechanical dissipation which meets the requirements for Advanced LIGO thermal noise performance.

  11. Invited article: CO2 laser production of fused silica fibers for use in interferometric gravitational wave detector mirror suspensions.

    PubMed

    Heptonstall, A; Barton, M A; Bell, A; Cagnoli, G; Cantley, C A; Crooks, D R M; Cumming, A; Grant, A; Hammond, G D; Harry, G M; Hough, J; Jones, R; Kelley, D; Kumar, R; Martin, I W; Robertson, N A; Rowan, S; Strain, K A; Tokmakov, K; van Veggel, M

    2011-01-01

    In 2000 the first mirror suspensions to use a quasi-monolithic final stage were installed at the GEO600 detector site outside Hannover, pioneering the use of fused silica suspension fibers in long baseline interferometric detectors to reduce suspension thermal noise. Since that time, development of the production methods of fused silica fibers has continued. We present here a review of a novel CO(2) laser-based fiber pulling machine developed for the production of fused silica suspensions for the next generation of interferometric gravitational wave detectors and for use in experiments requiring low thermal noise suspensions. We discuss tolerances, strengths, and thermal noise performance requirements for the next generation of gravitational wave detectors. Measurements made on fibers produced using this machine show a 0.8% variation in vertical stiffness and 0.05% tolerance on length, with average strengths exceeding 4 GPa, and mechanical dissipation which meets the requirements for Advanced LIGO thermal noise performance. PMID:21280809

  12. Characteristic strength, Weibull modulus, and failure probability of fused silica glass

    NASA Astrophysics Data System (ADS)

    Klein, Claude A.

    2009-11-01

    The development of high-energy lasers has focused attention on the requirement to assess the mechanical strength of optical components made of fused silica or fused quartz (SiO2). The strength of this material is known to be highly dependent on the stressed area and the surface finish, but has not yet been properly characterized in the published literature. Recently, Detrio and collaborators at the University of Dayton Research Institute (UDRI) performed extensive ring-on-ring flexural strength measurements on fused SiO2 specimens ranging in size from 1 to 9 in. in diameter and of widely differing surface qualities. We report on a Weibull statistical analysis of the UDRI data-an analysis based on the procedure outlined in Proc. SPIE 4375, 241 (2001). We demonstrate that (1) a two-parameter Weibull model, including the area-scaling principle, applies; (2) the shape parameter (m~=10) is essentially independent of the stressed area as well as the surface finish; and (3) the characteristic strength (1-cm2 uniformly stressed area) obeys a linear law, σC (in megapascals) ~=160-2.83×PBS (in parts per million per steradian), where PBS characterizes the surface/subsurface ``damage'' of an appropriate set of test specimens. In this light, we evaluate the cumulative failure probability and the failure probability density of polished and superpolished fused SiO2 windows as a function of the biaxial tensile stress, for stressed areas ranging from 0.3 to 100 cm2.

  13. Single-shot high aspect ratio bulk nanostructuring of fused silica using chirp-controlled ultrafast laser Bessel beams

    SciTech Connect

    Bhuyan, M. K.; Velpula, P. K.; Colombier, J. P.; Olivier, T.; Faure, N.; Stoian, R.

    2014-01-13

    We report single-shot, high aspect ratio nanovoid fabrication in bulk fused silica using zeroth order chirp-controlled ultrafast laser Bessel beams. We identify a unique laser pulse length and energy dependence of the physical characteristics of machined structures over which nanovoids of diameter in the range 200–400 nm and aspect ratios exceeding 1000 can be fabricated. A mechanism based on the axial energy deposition of nonlinear ultrashort Bessel beams and subsequent material densification or rarefaction in fused silica is proposed, intricating the non-diffractive nature with the diffusing character of laser-generated free carriers. Fluid flow through nanochannel is also demonstrated.

  14. Thin film contamination effects on laser-induced damage of fused silica surfaces at 355 nm

    SciTech Connect

    Burnham, A. K.; Cordillot, C.; Fornier, A.; Genin, F. Y.; Rubenchick, A. M.; Schirmann, D.; Yoshiyama, J.

    1998-07-28

    Fused silica windows were artificially contaminated to estimate the resistance of target chamber debris shields against laser damage during NIF operation. Uniform contamination thin films (1 to 5 nm thick) were prepared by sputtering various materials (Au, Al, Cu, and B4C). The loss of transmission of the samples was first measured. They were then tested at 355 nm in air with an 8-ns Nd:YAG laser. The damage morphologies were characterized by Nomarski optical microscopy and SEM. Both theory and experiments showed that metal contamination for films as thin as 1 nm leads to a substantial loss of transmission. The laser damage resistance dropped very uniformly across the entire surface (e.g. 6 J/cm2 for 5 nm of Cu). The damage morphology characterization showed that contrary to clean silica, metal coated samples did not produce pits on the surface. B4C coated silica, on the other hand, led to a higher density of such damage pits. A model for light absorption in the thin film was coupled with a simple heat deposition and diffusion model to perform preliminary theoretical estimates of damage thresholds. The estimates of the loss due to light absorption and reflection pointed out significant .differences between metals (e.g. Al and Au). The damage threshold predictions were in qualitative agreement with experimental measurements.

  15. Effects of silica-coating on surface topography and bond strength of porcelain fused to CAD/CAM pure titanium.

    PubMed

    Fukuyama, Takushi; Hamano, Naho; Ino, Satoshi

    2016-01-01

    The aim of this study was to evaluate the shear bond strength of porcelain fusing to titanium and the effects of surface treatment on surface structure of titanium. In the shear bond strength test, titanium surface treatments were: conventional, silica-coating without bonding agent, and silica-coating with bonding agent. Titanium surface treatments for analysis by the atomic force microscope (AFM) were: polishing, alumina sandblasting and silica-coating. The shear bond strength value of silica-coating with bonding agent group showed significantly higher than that of other groups. In AFM observation results, regular foamy structure which is effective for wetting was only observed in silica-coating. Therefore, this structure might indicate silicon. Silica-coating renders forms a nanoscopic regular foamy structure, involved in superhydrophilicity, to titanium surface, which is markedly different from the irregular surface generated by alumina sandblasting. PMID:27041024

  16. Mitigation of Laser Damage Growth in Fused Silica with a Galvanometer Scanned CO2 Laser

    SciTech Connect

    Bass, I L; Guss, G M; Hackel, R P

    2005-10-28

    At the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL), mitigation of laser surface damage growth on fused silica using single and multiple CO{sub 2} laser pulses has been consistently successful for damage sites whose lateral dimensions are less than 100 {micro}m, but has not been for larger sites. Cracks would often radiate outward from the damage when a CO{sub 2} pulse was applied to the larger sites. An investigation was conducted to mitigate large surface damage sites using galvanometer scanning of a tightly focused CO{sub 2} laser spot over an area encompassing the laser damage. It was thought that by initially scanning the CO{sub 2} spot outside the damage site, radiating crack propagation would be inhibited. Scan patterns were typically inward moving spirals starting at radii somewhat larger than that of the damage site. The duration of the mitigation spiral pattern was {approx}110 ms during which a total of {approx}1.3 J of energy was delivered to the sample. The CO{sub 2} laser spot had a 1/e{sup 2}-diameter of {approx}200 {micro}m. Thus, there was general heating of a large area around the damage site while rapid evaporation occurred locally at the laser spot position in the spiral. A 30 to 40 {micro}m deep crater was typically generated by this spiral with a diameter of {approx}600 {micro}m. The spiral would be repeated until there was no evidence of the original damage in microscope images. Using this technique, damage sites as large as 300 mm in size did not display new damage after mitigation when exposed to fluences exceeding 22 J/cm{sup 2} at 355 nm, 7.5 ns. It was found necessary to use a vacuum nozzle during the mitigation process to reduce the amount of re-deposited fused silica. In addition, curing spiral patterns at lower laser powers were used to presumably ''re-melt'' any re-deposited fused silica. A compact, shearing interferometer microscope was developed to permit in situ measurement of the depth of

  17. Determination of diffusion coefficients of hydrogen in fused silica between 296 and 523 K by Raman spectroscopy and application of fused silica capillaries in studying redox reactions

    USGS Publications Warehouse

    Shang, L.; Chou, I.-Ming; Lu, W.; Burruss, R.C.; Zhang, Y.

    2009-01-01

    Diffusion coefficients (D) of hydrogen in fused silica capillaries (FSC) were determined between 296 and 523 K by Raman spectroscopy using CO2 as an internal standard. FSC capsules (3.25 ?? 10-4 m OD, 9.9 ?? 10-5 m ID, and ???0.01 m long) containing CO2 and H2 were prepared and the initial relative concentrations of hydrogen in these capsules were derived from the Raman peak-height ratios between H2 (near 587 cm-1) and CO2 (near 1387 cm-1). The sample capsules were then heated at a fixed temperature (T) at one atmosphere to let H2 diffuse out of the capsule, and the changes of hydrogen concentration were monitored by Raman spectroscopy after quench. This process was repeated using different heating durations at 296 (room T), 323, 375, 430, 473, and 523 K; the same sample capsule was used repeatedly at each temperature. The values of D (in m2 s-1) in FSC were obtained by fitting the observed changes of hydrogen concentration in the FSC capsule to an equation based on Fick's law. Our D values are in good agreement with the more recent of the two previously reported experimental data sets, and both can be represented by: ln D = - (16.471 ?? 0.035) - frac(44589 ?? 139, RT) (R2 = 0.99991) where R is the gas constant (8.3145 J/mol K), T in Kelvin, and errors at 1?? level. The slope corresponds to an activation energy of 44.59 ?? 0.14 kJ/mol. The D in FSC determined at 296 K is about an order of magnitude higher than that in platinum at 723 K, indicating that FSC is a suitable membrane for hydrogen at temperature between 673 K and room temperature, and has a great potential for studying redox reactions at these temperatures, especially for systems containing organic material and/or sulphur. ?? 2009 Elsevier Ltd.

  18. Diffractive control of 3D multifilamentation in fused silica with micrometric resolution.

    PubMed

    Mendoza-Yero, Omel; Carbonell-Leal, Miguel; Doñate-Buendía, Carlos; Mínguez-Vega, Gladys; Lancis, Jesús

    2016-07-11

    We show that a simple diffractive phase element (DPE) can be used to manipulate at will the positions and energy of multiple filaments generated in fused silica under femtosecond pulsed illumination. The method allows obtaining three-dimensional distributions of controlled filaments whose separations can be in the order of few micrometers. With such small distances we are able to study the mutual coherence among filaments from the resulted interference pattern, without needing a two-arm interferometer. The encoding of the DPE into a phase-only spatial light modulator (SLM) provides an extra degree of freedom to the optical set-up, giving more versatility for implementing different DPEs in real time. Our proposal might be particularly suited for applications at which an accurate manipulation of multiple filaments is required. PMID:27410807

  19. Laser Damage Growth in Fused Silica with Simultaneous 351 nm and 1053 nm irradiation

    SciTech Connect

    Norton, M A; Carr, A V; Carr, C W; Donohue, E E; Feit, M D; Hollingsworth, W G; Liao, Z; Negres, R A; Rubenchik, A M; Wegner, P J

    2008-10-24

    Laser-induced growth of optical damage often determines the useful lifetime of an optic in a high power laser system. We have extended our previous work on growth of laser damage in fused silica with simultaneous 351 nm and 1053 nm laser irradiation by measuring the threshold for growth with various ratios of 351 nm and 1053 nm fluence. Previously we reported that when growth occurs, the growth rate is determined by the total fluence. We now find that the threshold for growth is dependent on both the magnitude of the 351 nm fluence as well as the ratio of the 351 nm fluence to the 1053 nm fluence. Furthermore, the data suggests that under certain conditions the 1053 nm fluence does not contribute to the growth.

  20. 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.

  1. Dependence of growth rate of quartz in fused silica on pressure and impurity content

    NASA Technical Reports Server (NTRS)

    Fratello, V. J.; Hays, J. F.; Turnbull, D.

    1980-01-01

    The effects of pressure, temperature, and some variations in impurity content on the growth rate u of quartz into fused silica were measured. Under all conditions the growth rate was interface controlled and increased exponentially with pressure with an activation volume averaging -21.2 cu cm/mole. The activation enthalpy for all specimens is extrapolated to a zero pressure value of 64 kcal/mole, within the experimental uncertainty. At a given stoichiometry the effect of hydroxyl content on growth rate is described entirely by a linear term C(OH) in the prefactor of the equation for the growth rate. The effect of chlorine impurity can be described similarly. Also u is increased as the ideal stoichiometry is approached from the partially reduced state.

  2. Structural modifications in fused silica induced by ultraviolet fs laser filaments

    NASA Astrophysics Data System (ADS)

    Zergioti, I.; Kyrkis, K. D.; Papazoglou, D. G.; Tzortzakis, S.

    2007-07-01

    It is shown that the tight focusing of short ultraviolet laser pulses (248 nm, 450 fs) in the bulk of high bandgap transparent solids (fused silica) can result in structural modifications in the material. These can vary from small changes of the refractive index to birefringence, cracks and voids. This restructuring of the medium is due to the high laser intensities attained, and the plasma that is generated through multi-photon processes. The restructuring comes in the form of a string, which is the result of the nonlinear propagation of the laser beam in the medium as a self-trapped filament. We resume the conditions for the generation of the different types of modifications and comment on the temporal evolution and the role of the plasma strings at the trail of the light filaments.

  3. Sub-picosecond ultraviolet laser filamentation-induced bulk modifications in fused silica

    NASA Astrophysics Data System (ADS)

    Papazoglou, D. G.; Zergioti, I.; Tzortzakis, S.; Sgouros, G.; Maravelias, G.; Christopoulos, S.; Fotakis, C.

    2005-07-01

    We present experiments with sub-picosecond ultraviolet laser pulses (248 nm, 450 fs) tightly focused in the bulk of fused-silica samples. The high laser intensities attained generate plasma through multi-photon absorption and electron avalanche processes in the bulk of the material. Depending on the initial experimental conditions three distinct types of structural changes in the material are observed, from small changes of the refractive index to birefringence, and even cracks and voids. We also observe the creation of micro-channels, up to 115 μm in length, inside the material due to self-guiding and filamentation of the laser pulses in the transparent material. The selective change of the refractive index is a promising method for the fabrication of photonic structures such as waveguides and three-dimensional integrated optical devices.

  4. Influence of temperature on period of torsion pendulum with a high-Q fused silica fiber

    NASA Astrophysics Data System (ADS)

    Luo, Jie; Wu, Wei-Huang; Shao, Cheng-Gang; Li, Qing; Liu, Jian-Ping; Zhan, Wen-Ze; Wang, Dian-Hong

    2015-09-01

    Due to the high-Q fused silica fiber's extreme sensitivity to temperature change, the period estimation of torsion pendulum with high precision depends on the effective correction of the thermoelastic effect. In the measurement of G with the time-of-swing method, we analyze the complex relation between temperature and the pendulum's period and propose a developed method to find the shear thermoelasticity coefficient as well as isolate the influence of temperature on period alone. The result shows that the shear thermoelasticity coefficient is 101(2) × 10-6/∘C, the resultant correction to Δ(ω2) is 9.16(0.18) ppm, and the relative uncertainty to G is less than 1 ppm.

  5. Fused-silica sandwiched three-port grating under second Bragg angle incidence

    NASA Astrophysics Data System (ADS)

    Li, Hongtao; Wang, Bo; Pei, Hao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2016-05-01

    The fused-silica sandwiched three-port grating under second Bragg angle incidence is presented with operation in transmission. To obtain a highly-efficient three-port grating for a working wavelength of 800 nm, the grating depth and period should be optimized by using rigorous coupled-wave analysis. With the optimized different three-port grating depths and periods, both TE-polarized and TM-polarized waves can be diffracted into three orders with nearly 33% efficiency for the given duty cycle of 0.6. Based on the grating parameters of numerical optimization, modal method may be employed to explain the physical mechanism of the beam propagation in the grating and analyze the splitting behavior. For the sandwiched three-port grating, it is feasible that the diffraction efficiencies can be enhanced for both TE and TM polarizations.

  6. Generation of laser-induced periodic surface structures on transparent material-fused silica

    NASA Astrophysics Data System (ADS)

    Schwarz, Simon; Rung, Stefan; Hellmann, Ralf

    2016-05-01

    We report on a comparison between simulated and experimental results for the generation of laser-induced periodic surface structures with low spatial frequency on dielectrics. Using the established efficacy factor theory extended by a Drude model, we determine the required carrier density for the generation of low spatial frequency LIPSS (LSFL) and forecast their periodicity and orientation. In a subsequent calculative step, we determine the fluence of ultrashort laser pulses necessary to excite this required carrier density in due consideration of the pulse number dependent ablation threshold. The later calculation is based on a rate equation including photo- and avalanche ionization and derives appropriate process parameters for a selective generation of LSFL. Exemplarily, we apply this approach to the generation of LSFL on fused silica using a 1030 nm femtosecond laser. The experimental results for the orientation and spatial periodicity of LSFL reveal excellent agreement with the simulation.

  7. Temporal femtosecond pulse shaping dependence of laser-induced periodic surface structures in fused silica

    SciTech Connect

    Shi, Xuesong; Jiang, Lan; Li, Xin Zhang, Kaihu; Yu, Dong; Yu, Yanwu; Lu, Yongfeng

    2014-07-21

    The dependence of periodic structures and ablated areas on temporal pulse shaping is studied upon irradiation of fused silica by femtosecond laser triple-pulse trains. Three types of periodic structures can be obtained by using pulse trains with designed pulse delays, in which the three-dimensional nanopillar arrays with ∼100–150 nm diameters and ∼200 nm heights are first fabricated in one step. These nanopillars arise from the break of the ridges of ripples in the upper portion, which is caused by the split of orthogonal ripples in the bottom part. The localized transient electron dynamics and corresponding material properties are considered for the morphological observations.

  8. Numerical model for light propagation and light intensity distribution inside coated fused silica capillaries

    NASA Astrophysics Data System (ADS)

    Piasecki, Tomasz; Macka, Mirek; Paull, Brett; Brabazon, Dermot

    2011-07-01

    Numerical simulations of light propagation through capillaries have been reported to a limited extent in the literature for uses such as flow-cell design. These have been restricted to prediction of light path for very specific cases to date. In this paper, a new numerical model of light propagation through multi-walled cylindrical systems, to represent coated and uncoated capillaries is presented. This model allows for light ray paths and light intensity distribution within the capillary to be predicted. Macro-scale (using PMMA and PC cylinders) and micro-scale (using PTFE coated fused silica capillaries) experiments were conducted to validate the model's accuracy. These experimental validations have shown encouragingly good agreement between theoretical predictions and measured results, which could allow for optimisation of associated regions for monolith synthesis and use in fluidic chromatography, optical detection systems and flow cells for capillary electrophoresis and flow injection analysis.

  9. Depth profiling of sol-gel multilayers on fused silica using dynamic SIMS and SNMS

    NASA Astrophysics Data System (ADS)

    Bazin, Nicholas J.; Andrew, James E.; McInnes, Hazel A.; Porter, K. J.; Morris, A. J.

    1999-07-01

    Depth profiling using Dynamic Secondary Ion Mass Spectroscopy through multilayer coatings on fused silica substrates has revealed the effect of increasing the number of layers in the stack. Results are presented for both spin and dip coated multilayers and a significant difference in the interfacial boundary is seen between the two processes. Individual layer thicknesses were estimated using this technique and compared to values gained from UV-Visible spectroscopy. Depth profiling using SNMS of a thick 2-layer system also revealed the thickness of the layers and an indication of the intermixing between them. These measurements agreed well with UV-Vis data. A comparison between these depth-profiling techniques and previous work using AES/XPS depth profiling is discussed.

  10. Open tubular capillary electrochromatography migration behavior of enkephalins in etched chemically modified fused silica capillaries.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Velpula, Sunandini

    2006-09-01

    Fused silica capillaries for use in electrophoretic analyses are etched with ammonium bifluoride in the presence of a second inorganic salt (CuCl(2), CrCl(3), NaNO(3), or (NH(4))(2)CO(3)). The effects of the presence of these inorganic components in the surface matrix on the electromigration behavior of enkephalins are evaluated. Resolution, efficiency and peak shape are used to compare the various columns. In some cases the etched surface is then modified by the addition of an octadecyl moiety using a silanization/hydrosilation procedure. The surface properties of the etched capillaries can also be evaluated by electroosmotic flow measurements. RSDs of migration times under identical experimental conditions were <1%. PMID:16720028

  11. Influence of incidence angle and polarization state on the damage site characteristics of fused silica.

    PubMed

    Ma, Bin; Zhang, Yanyun; Ma, Hongping; Jiao, Hongfei; Cheng, Xinbin; Wang, Zhanshan

    2014-02-01

    The influence of the incidence angle and polarization state on the damage site characteristics of fused silica under 355 nm laser irradiation was investigated. The initial damage morphologies and growth behaviors of the damage sites on the exit surface at incidence angles of 0° and 45° as well as in P and S states were compared to investigate the effects of various angles and polarization states. The relationships between the size of the initial damage sites and the laser fluence, as well as the growth threshold, were discussed. The damage morphologies of the craters and cracks at different incidence angles and polarization states were then investigated. Finally, the growth characteristics of the lateral size, crater depth, and crack depth were compared and analyzed. PMID:24514256

  12. Evaluation and analysis of polished fused silica subsurface quality by the nanoindenter technique

    SciTech Connect

    Ma Bin; Shen Zhengxiang; He Pengfei; Sha Fei; Wang Chunliang; Wang Bin; Ji Yiqin; Liu Huasong; Li Weihao; Wang Zhanshan

    2011-03-20

    We evaluate the subsurface quality of polished fused silica samples using the nanoindenter technique. Two kinds of samples, consisting of hundreds of nanometers and micrometers of subsurface damage layers, are fabricated by controlling the grinding and polishing processes, and the subsurface quality has been verified by the chemical etching method. Then several nanoindentation experiments are performed using the Berkovich tip to investigate the subsurface quality. Some differences are found by relative measurements in terms of the relationship between the total penetration and the peak load on the surfaces, the modulus calculated over the defined depths and from unload, and the indented morphology at a constant load near the surface collapse threshold. Finally, the capabilities of such a mechanical method for detecting subsurface flaws are discussed and analyzed.

  13. Review and assessment of measured values of the nonlinear refractive-index coefficient of fused silica

    SciTech Connect

    Milam, D.

    1998-01-01

    The literature describes more than 30 measurements, at wavelengths between 249 and 1550 nm, of the absolute value of the nonlinear refractive-index coefficient of fused silica. Results of these experiments were assessed and best currently available values were selected for the wavelengths of 351, 527, and 1053 nm. The best values are (3.6{plus_minus}0.64){times}10{sup {minus}16} cm{sup 2}/W at 351 nm, (3.0{plus_minus}0.35){times}10{sup {minus}16} cm{sup 2}/W at 527 nm, and (2.74{plus_minus}0.17){times}10{sup {minus}16} cm{sup 2}/W at 1053 nm. {copyright} 1998 Optical Society of America

  14. Detection of subsurface trace impurity in polished fused silica with biological method.

    PubMed

    Wang, Zhuo; Wang, Lin; Yang, Junhong; Peng, Wenqiang; Hu, Hao

    2014-09-01

    Subsurface damage (SSD), especially photoactive impurities, degrades the performance of high energy optics by reduction in the laser induced damage threshold. As the polishing defects are trace content and lie beneath the surface, they are difficult to detect. We herein present a biological method to measure impurities on polished fused silica, based on the intense inhibiting ability about trace level of ceria on enzyme activity. And the enzyme activity is measured in the individual etching solutions of a sequential etching process. Results show that detectability of the biological method satisfies the needs of trace impurity detection with low cost and simple apparatus. Furthermore ceria can be used to tag SSD in lapped and polished optics. PMID:25321508

  15. Unified beam splitter of fused silica grating under the second Bragg incidence.

    PubMed

    Sun, Zhumei; Zhou, Changhe; Cao, Hongchao; Wu, Jun

    2015-11-01

    A unified design for a 1×2 beam splitter of dielectric rectangular transmission gratings under the second Bragg incidence is theoretically investigated for TE- and TM-polarized light. The empirical equations of the relative grating parameters (ratio of the absolute one to incidence wavelength) for this design are also obtained with the simplified modal method (SMM). The influences of polarization of incident light and relative grating parameters on the performance of the beam splitter are thoroughly studied based on the SMM and rigorous coupled-wave analysis. Two specific gratings are demonstrated with an even split and high diffraction efficiency (>94% for TE polarization and >97% for the TM counterpart). The unified profiles of the 1×2 beam splitter are independent from the incidence wavelength since the refractive index of fused silica is roughly a constant over a wide range of wavelengths, which should be promising for future applications. PMID:26560909

  16. Scattering analysis for random antireflective structures on fused silica in the ultraviolet.

    PubMed

    Zhao, Jiaoling; Qi, Hongji; Wang, Hu; He, Hongbo; Zhang, Weili

    2015-11-15

    Random antireflective structures are fabricated on fused silica by the thermal dewetting process and reactive ion etching, which shows a broadband antireflective effect over the whole visible wavelength. However, the transmittance in the ultraviolet is limited by the scattering from the etched structures. A graded refractive index model ignoring the scattering in the visible range is applied to extract the etched profile. Then the Lubachevsky-Stillinger algorithm is used to reconstruct the random antireflective structures with the extracted profile. Bidirectional scattering distribution for the reconstructed structures is simulated with the finite-difference time-domain method, which indicates the importance of transmissive scattering the scattering directivity. The scattering directivity is explained well with an effective grating model. The period of the effective grating can guide the prepared technique in the ultraviolet. PMID:26565826

  17. Influence of temperature on period of torsion pendulum with a high-Q fused silica fiber.

    PubMed

    Luo, Jie; Wu, Wei-Huang; Shao, Cheng-Gang; Li, Qing; Liu, Jian-Ping; Zhan, Wen-Ze; Wang, Dian-Hong

    2015-09-01

    Due to the high-Q fused silica fiber's extreme sensitivity to temperature change, the period estimation of torsion pendulum with high precision depends on the effective correction of the thermoelastic effect. In the measurement of G with the time-of-swing method, we analyze the complex relation between temperature and the pendulum's period and propose a developed method to find the shear thermoelasticity coefficient as well as isolate the influence of temperature on period alone. The result shows that the shear thermoelasticity coefficient is 101(2) × 10(-6)/°C, the resultant correction to Δ(ω(2)) is 9.16(0.18) ppm, and the relative uncertainty to G is less than 1 ppm. PMID:26429460

  18. Fabrication of 250-nm-hole arrays in glass and fused silica by UV laser ablation

    NASA Astrophysics Data System (ADS)

    Karstens, R.; Gödecke, A.; Prießner, A.; Ihlemann, J.

    2016-09-01

    Parallel nanohole drilling in glass using an ArF excimer laser (193 nm) is demonstrated. For the first time, hole arrays with 500 nm pitch and individual holes with 250 nm diameter and more than 100 nm depth are fabricated by phase mask imaging using a Schwarzschild objective. Holes in soda lime glass are drilled by direct ablation; fused silica is processed by depositing a SiOx-film on SiO2, patterning the SiOx by ablation, and finally oxidizing the remaining SiOx to SiO2. Thermally induced ordered dewetting of noble metal films deposited on such templates may be used for the fabrication of plasmonic devices.

  19. Laser-induced damage and fracture in fused silica vacuum windows

    NASA Astrophysics Data System (ADS)

    Campbell, John H.; Hurst, Patricia A.; Heggins, Dwight D.; Steele, William A.; Bumpas, Stanley E.

    1997-05-01

    Laser induced damage, that initiates catastrophic fracture, has been observed in large, fused silica lenses that also serve as vacuum barriers in high-fluence positions on the Nova and Beamlet lasers. In nearly all cases damage occurs on the vacuum side of the lens. The damage can lead to catastrophic crack growth if the flaw size exceeds the critical flaw size for SiO2. If the elastic stored energy in the lens in high enough, the lens will fracture into many pieces resulting in an implosion. The consequences of such an implosion can be severe, particularly for large vacuum systems. Three parameters control the degree of fracture in the vacuum barrier window: (1) the elastic stored energy, (2) the ratio of the window thickness to flaw depth and (3) secondary crack propagation. Fracture experiments have ben carried our on 15-cm diameter fused silica windows that contain surface flaws caused by laser damage. The results of these experiments, combined with data from window failures on Beamlet and Nova have been sued to develop design criteria for a 'fail-safe' lens. Specifically the window must be made thick enough such that the peak tensile stress is less than 500 psi and the corresponding ratio of the thickness to critical flaw size is less than 6. Under these conditions a properly mounted window, upon failure, will break into only tow pieces and will not implode. One caveat to these design criteria is that the air leak through the window before secondary crack growth occurs. Finite element stress calculations of a window before and immediately following fracture into two pieces show that the elastic stored energy is redistributed if the fragments 'lock' in place and thereby bridge the opening. In such cases, the peak stresses at the flaw site can increase leading to further crack growth.

  20. Application of total internal reflection microscopy for laser damage studies on fused silica

    SciTech Connect

    Sheehan, L. M., LLNL

    1997-12-01

    Damage studies show that the majority of damage on ultraviolet grade fused silica initiates at the front or rear surface. The grinding and polishing processes used to produce the optical surfaces of transparent optics play a key role in the development of defects which can ultimately initiate damage. These defects can be on or breaking through the surface or can be sub-surface damage. Total Internal Reflection Microscopy has been documented as a tool for revealing both sub-surface and surface defects in transparent materials. Images taken which compare both Total Internal Reflection Microscopy and Atomic Force Microscopy show that the observed defects can be less than one micron in size. Total Internal Reflection Microscopy has the added benefit of being able to observe large areas (1 square millimeter) with sub-micron detection. Both off-line and in-situ systems have been applied in the Lawrence Livermore National Laboratory`s damage laboratory in order to understand defects in the surface and subsurface of polished fused silica. There is a preliminary indication that TIRM quality can be related to the damage resistance. The in-situ microscope is coupled into a 355 run, 7.5 ns, 10 Hz Nd:YAG laser system in order to study damage occurring at localized scatter sites revealed with the Total Internal Reflection Microscopy method. The tests indicate damage initiating at observed artifacts which have many different morphologies and damage behaviors. Some of the scatter sites and damage morphologies revealed have been related back to the finishing process.

  1. Disposable Polydimethylsiloxane (PDMS)-Coated Fused Silica Optical Fibers for Sampling Pheromones of Moths

    PubMed Central

    Lievers, Rik; Groot, Astrid T.

    2016-01-01

    In the past decades, the sex pheromone composition in female moths has been analyzed by different methods, ranging from volatile collections to gland extractions, which all have some disadvantage: volatile collections can generally only be conducted on (small) groups of females to detect the minor pheromone compounds, whereas gland extractions are destructive. Direct-contact SPME overcomes some of these disadvantages, but is expensive, the SPME fiber coating can be damaged due to repeated usage, and samples need to be analyzed relatively quickly after sampling. In this study, we assessed the suitability of cheap and disposable fused silica optical fibers coated with 100 μm polydimethylsiloxane (PDMS) by sampling the pheromone of two noctuid moths, Heliothis virescens and Heliothis subflexa. By rubbing the disposable PDMS fibers over the pheromone glands of females that had called for at least 15 minutes and subsequently extracting the PDMS fibers in hexane, we collected all known pheromone compounds, and we found a strong positive correlation for most pheromone compounds between the disposable PDMS fiber rubs and the corresponding gland extracts of the same females. When comparing this method to volatile collections and the corresponding gland extracts, we generally found comparable percentages between the three techniques, with some differences that likely stem from the chemical properties of the individual pheromone compounds. Hexane extraction of cheap, disposable, PDMS coated fused silica optical fibers allows for sampling large quantities of individual females in a short time, eliminates the need for immediate sample analysis, and enables to use the same sample for multiple chemical analyses. PMID:27533064

  2. Disposable Polydimethylsiloxane (PDMS)-Coated Fused Silica Optical Fibers for Sampling Pheromones of Moths.

    PubMed

    Lievers, Rik; Groot, Astrid T

    2016-01-01

    In the past decades, the sex pheromone composition in female moths has been analyzed by different methods, ranging from volatile collections to gland extractions, which all have some disadvantage: volatile collections can generally only be conducted on (small) groups of females to detect the minor pheromone compounds, whereas gland extractions are destructive. Direct-contact SPME overcomes some of these disadvantages, but is expensive, the SPME fiber coating can be damaged due to repeated usage, and samples need to be analyzed relatively quickly after sampling. In this study, we assessed the suitability of cheap and disposable fused silica optical fibers coated with 100 μm polydimethylsiloxane (PDMS) by sampling the pheromone of two noctuid moths, Heliothis virescens and Heliothis subflexa. By rubbing the disposable PDMS fibers over the pheromone glands of females that had called for at least 15 minutes and subsequently extracting the PDMS fibers in hexane, we collected all known pheromone compounds, and we found a strong positive correlation for most pheromone compounds between the disposable PDMS fiber rubs and the corresponding gland extracts of the same females. When comparing this method to volatile collections and the corresponding gland extracts, we generally found comparable percentages between the three techniques, with some differences that likely stem from the chemical properties of the individual pheromone compounds. Hexane extraction of cheap, disposable, PDMS coated fused silica optical fibers allows for sampling large quantities of individual females in a short time, eliminates the need for immediate sample analysis, and enables to use the same sample for multiple chemical analyses. PMID:27533064

  3. Internal structure of the nanogratings generated inside bulk fused silica by ultrafast laser direct writing

    SciTech Connect

    Sharma, S. P.; Vilar, R.; Oliveira, V.; Herrero, P.

    2014-08-07

    The aim of the present work was to characterize the internal structure of nanogratings generated inside bulk fused silica by ultrafast laser processing and to study the influence of diluted hydrofluoric acid etching on their structure. The nanogratings were inscribed at a depth of 100 μm within fused silica wafers by a direct writing method, using 1030 nm radiation wavelength and the following processing parameters: E = 5 μJ, τ = 560 fs, f = 10 kHz, and v = 100 μm/s. The results achieved show that the laser-affected regions are elongated ellipsoids with a typical major diameter of about 30 μm and a minor diameter of about 6 μm. The nanogratings within these regions are composed of alternating nanoplanes of damaged and undamaged material, with an average periodicity of 351 ± 21 nm. The damaged nanoplanes contain nanopores randomly dispersed in a material containing a large density of defects. These nanopores present a roughly bimodal size distribution with average dimensions for each class of pores 65 ± 20 × 16 ± 8 × 69 ± 16 nm{sup 3} and 367 ± 239 × 16 ± 8 × 360 ± 194 nm{sup 3}, respectively. The number and size of the nanopores increases drastically when an hydrofluoric acid treatment is performed, leading to the coalescence of these voids into large planar discontinuities parallel to the nanoplanes. The preferential etching of the damaged material by the hydrofluoric acid solution, which is responsible for the pores growth and coalescence, confirms its high defect density.

  4. Ultrafast laser induced electronic and structural modifications in bulk fused silica

    SciTech Connect

    Mishchik, K.; D'Amico, C.; Velpula, P. K.; Mauclair, C.; Boukenter, A.; Ouerdane, Y.; Stoian, R.

    2013-10-07

    Ultrashort laser pulses can modify the inner structure of fused silica, generating refractive index changes varying from soft positive (type I) light guiding forms to negative (type II) values with void presence and anisotropic sub-wavelength modulation. We investigate electronic and structural material changes in the type I to type II transition via coherent and incoherent secondary light emission reflecting free carrier behavior and post-irradiation material relaxation in the index change patterns. Using phase contrast microscopy, photoluminescence, and Raman spectroscopy, we determine in a space-resolved manner defect formation, redistribution and spatial segregation, and glass network reorganization paths in conditions marking the changeover between type I and type II photoinscription regimes. We first show characteristic patterns of second harmonic generation in type I and type II traces, indicating the collective involvement of free carriers and polarization memory. Second, incoherent photoemission from resonantly and non-resonantly excited defect states reveals accumulation of non-bridging oxygen hole centers (NBOHCs) in positive index domains and oxygen deficiency centers (ODCs) with O{sub 2}{sup −} ions segregation in void-like regions and in the nanostructured domains, reflecting the interaction strength. Complementary Raman investigations put into evidence signatures of the different environments where photo-chemical densification (bond rearrangements) and mechanical effects can be indicated. NBOHCs setting in before visible index changes serve as precursors for subsequent compaction build-up, indicating a scenario of cold, defect-assisted densification for the soft type I irradiation regime. Additionally, we observe hydrodynamic effects and severe bond-breaking in type II zones with indications of phase transition. These observations illuminate densification paths in fused silica in low power irradiation regimes, and equally in energetic ranges

  5. Efficiency of magnetorheological fluid finishing on the elimination of defects in fused silica optics

    NASA Astrophysics Data System (ADS)

    Catrin, R.; Taroux, D.; Cormont, P.; Maunier, C.; Corbineau, T.; Razé, G.; Néauport, J.

    2013-09-01

    The MegaJoule laser being constructed at the CEA near Bordeaux (France) is designed to focus more than 1 MJ of energy of UV light, on a millimeter scale target in the centre of an experiment chamber. After amplification and transport at the wavelength of 1053 nm, frequency conversion at 351 nm is done with KH2PO4 crystals. The final optic assembly of this system is made up of large fused silica optics, working in transmission, that are used to convey, focus or shape the laser beam. When exposed to fluences of some joules per square centimeter at 351 nm within nanosecond pulse duration, fused silica optics can exhibit localized damage. Damage sites grow exponentially after further laser exposition and therefore dramatically limit the optic lifetime. The nature of the surface finishing process has been established to determine the lifetime of these components under high UV fluences (i.e. more than 5 J/cm2 for 3 ns pulses). Being able to reduce or eliminate the damage initiators such as subsurface cracks present in subsurface damage (SSD) layer of conventionally polished optical components aims this study. Magneto-rheological fluid finishing (MRF) is chosen as a final polishing tool to remove layers of material without inducing further damages. MRF enables to process optics with very small normal stresses applied to the surface during material removal and thus permits the elimination of the residual subsurface cracks. This study offers a better understanding of the efficiency of MRF polishing on the elimination of subsurface cracks in SSD layers.

  6. Ultrafast laser induced electronic and structural modifications in bulk fused silica

    NASA Astrophysics Data System (ADS)

    Mishchik, K.; D'Amico, C.; Velpula, P. K.; Mauclair, C.; Boukenter, A.; Ouerdane, Y.; Stoian, R.

    2013-10-01

    Ultrashort laser pulses can modify the inner structure of fused silica, generating refractive index changes varying from soft positive (type I) light guiding forms to negative (type II) values with void presence and anisotropic sub-wavelength modulation. We investigate electronic and structural material changes in the type I to type II transition via coherent and incoherent secondary light emission reflecting free carrier behavior and post-irradiation material relaxation in the index change patterns. Using phase contrast microscopy, photoluminescence, and Raman spectroscopy, we determine in a space-resolved manner defect formation, redistribution and spatial segregation, and glass network reorganization paths in conditions marking the changeover between type I and type II photoinscription regimes. We first show characteristic patterns of second harmonic generation in type I and type II traces, indicating the collective involvement of free carriers and polarization memory. Second, incoherent photoemission from resonantly and non-resonantly excited defect states reveals accumulation of non-bridging oxygen hole centers (NBOHCs) in positive index domains and oxygen deficiency centers (ODCs) with O2- ions segregation in void-like regions and in the nanostructured domains, reflecting the interaction strength. Complementary Raman investigations put into evidence signatures of the different environments where photo-chemical densification (bond rearrangements) and mechanical effects can be indicated. NBOHCs setting in before visible index changes serve as precursors for subsequent compaction build-up, indicating a scenario of cold, defect-assisted densification for the soft type I irradiation regime. Additionally, we observe hydrodynamic effects and severe bond-breaking in type II zones with indications of phase transition. These observations illuminate densification paths in fused silica in low power irradiation regimes, and equally in energetic ranges, characterized by

  7. Etching of fused silica and glass with excimer laser at 351 nm

    NASA Astrophysics Data System (ADS)

    Zimmer, K.; Braun, A.; Böhme, R.

    2003-03-01

    The etching of solid surfaces at the interface to liquids is a new promising method for micro-machining of transparent materials. To extend the method to additional materials the pulsed radiation of a XeF-excimer laser (351 nm) was used for etching different types of glass (Corning Inc.: Pyrex, 7059 and Schott Group: D263, AF45) and fused silica for comparison. The etch rates of the investigated materials increase almost linear at low laser fluences. Threshold fluences for glass as low as 0.5 J/cm 2 and etch rates from 6 to 10 nm per pulse at 1 J/cm 2 have been determined. The etch rate and the threshold fluence depend also on the used liquid, consisting of a solvent (acetone, toluene) and a certain concentration of dissolved pyrene, but only little on the glass type. Due to the low etch rate typically very smooth surfaces are achieved. The surface roughness measured by AFM on Corning 7059-glass at an etch depth of 3.7 μm is as low as 4 nm. Contrary to the other glasses the surface roughness of Pyrex is much higher and dominated by typical arbitrary etch pits with micron dimensions. Comparing the etching of fused silica at a wavelength of 248 and 351 nm the used solution influences both the etch threshold and the etch rate. In accordance to earlier investigations at 248 nm also XeF-laser etching at the interface to an absorbing liquid results in a good surface quality, well defined patterns and almost no debris deposition. Thus, this technique is a good candidate for precise micro-machining applications.

  8. Hydrolysis of polycarbonate in sub-critical water in fused silica capillary reactor with in situ Raman spectroscopy

    USGS Publications Warehouse

    Pan, Z.; Chou, I.-Ming; Burruss, R.C.

    2009-01-01

    The advantages of using fused silica capillary reactor (FSCR) instead of conventional autoclave for studying chemical reactions at elevated pressure and temperature conditions were demonstrated in this study, including the allowance for visual observation under a microscope and in situ Raman spectroscopic characterization of polycarbonate and coexisting phases during hydrolysis in subcritical water. ?? 2009 The Royal Society of Chemistry.

  9. Preparation of fused-silica columns with phases immobilized by cobalt-60 gamma radiation; application to essential oil analysis

    SciTech Connect

    Hubball, J.A.

    1987-01-01

    Cobalt-60 gamma-radiation was used to immobilize polymeric stationary phases in fused silica capillary columns for gas chromatography. Surface studies of the uncoated fused silica tubing by optical and scanning electron microscopy indicated some irregularities, but overall the tubing maintained its strength and flexibility at dosages up to 25 MRads. A polydimethylsiloxane phase (OV-1) and a polyethylene glycol phase (Carbowax 20 M) were effectively immobilized on the inner surface of fused silica capillary tubing without altering the properties of the phases. The optimum radiation dosage for OV-1 was 7 MRads, while Carbowax 20 M required 25 MRads to immobilize 33% of the coated layer. Fused silica capillary columns prepared with both phases were evaluated for deactivation, efficiency, and thermal stability. Immobilization of Carbowax 20 M extended the low and high temperature limits by 30 C in each direction. Columns prepared in this study were used to analyze the essential oil of Siparuna guianensis. Several key components of the oil were identified by GC/MS and gas chromatographic techniques.

  10. Post-processing of fused silica and its effects on damage resistance to nanosecond pulsed UV lasers.

    PubMed

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

    2016-04-10

    HF-based (hydrofluoric acid) chemical etching has been a widely accepted technique to improve the laser damage performance of fused silica optics and ensure high-power UV laser systems at designed fluence. Etching processes such as acid concentration, composition, material removal amount, and etching state (etching with additional acoustic power or not) may have a great impact on the laser-induced damage threshold (LIDT) of treated sample surfaces. In order to find out the effects of these factors, we utilized the Taguchi method to determine the etching conditions that are helpful in raising the LIDT. Our results show that the most influential factors are concentration of etchants and the material etched away from the viewpoint of damage performance of fused silica optics. In addition, the additional acoustic power (∼0.6  W·cm-2) may not benefit the etching rate and damage performance of fused silica. Moreover, the post-cleaning procedure of etched samples is also important in damage performances of fused silica optics. Different post-cleaning procedures were, thus, experiments on samples treated under the same etching conditions. It is found that the "spraying + rinsing + spraying" cleaning process is favorable to the removal of etching-induced deposits. Residuals on the etched surface are harmful to surface roughness and optical transmission as well as laser damage performance. PMID:27139869

  11. Ion-beam polishing of fused silica substrates for imaging soft x-ray and extreme ultraviolet optics.

    PubMed

    Chkhalo, N I; Churin, S A; Mikhaylenko, M S; Pestov, A E; Polkovnikov, V N; Salashchenko, N N; Zorina, M V

    2016-02-20

    We have studied the surface treatment of polished fused silica by neutralized Ar ions with energy of 500-1500 eV and incidence angles of 0-90°. We found the following regularities: for samples that passed the standard procedure of deep polishing (initial effective roughness σ(eff)∼0.5  nm), the effective roughness decreases to the ultrasmooth level (i.e., σ(eff)∼0.25  nm in the range of spatial frequencies q∈[4.9×10(-2)-63]  μm(-1)). The effect begins to be noticeable at the material removal of 150 nm and reaches saturation at depths of removal greater than 1 μm. For supersmooth samples (σ(eff)<0.3  nm), the effective roughness keeps the initial level at material removal down to tens of micrometers. The optimal ion energy range is 800-1300 eV (maximum smoothing effect); at higher energy some surface roughness degradation is observed. All the smoothing effects are observed at the incidence angle range θ(in)=0-35°. Increasing the ion energy above 1300 eV increases the etching rate by up to 4 μm per hour (J(ion)=0.8  mA/cm2), which allows for deep aspherization of sized substrates. The technique allows for manufacturing the optical elements for extreme ultraviolet and soft x-ray wavelength ranges with a numerical aperture of up to 0.6. PMID:26906575

  12. Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

    SciTech Connect

    Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D; Elhadj, S; Yang, S T

    2009-10-30

    Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.

  13. Laser-induced damage morphology in fused silica at 1064 nm in the nanosecond regime

    NASA Astrophysics Data System (ADS)

    Chambonneau, Maxime; Diaz, Romain; Duchateau, Guillaume; Grua, Pierre; Natoli, Jean-Yves; Rullier, Jean-Luc; Lamaignère, Laurent

    2014-10-01

    The morphology of laser-induced damage sites at the exit surface of fused silica is tightly correlated to the mode composition of the nanosecond laser pulses at 1064 nm. In the single longitudinal mode (SLM) configuration, a molten and fractured central zone is surrounded by a funnel-shaped surface modification. Ring patterns surround the damage sites when these are initiated by multiple longitudinal modes (MLM) laser pulses. In this last mode configuration, the pulses temporal profiles as well as the damage ring patterns differ from pulse to pulse. The appearance chronology of the rings is found to be closely related to the temporal shape of the laser pulses. This supports that the damage morphology originates from the coupling of a laser-supported detonation wave propagating in air with an ablation mechanism in silica. In our experiments, the propagation speed of the detonation wave reaches about 20 km/s and scales as the cube root of the laser intensity, in good agreement with theory.

  14. Laser-induced damage of fused silica at 355 nm initiated at scratches

    NASA Astrophysics Data System (ADS)

    Salleo, Alberto; Genin, Francois Y.; Yoshiyama, J. M.; Stolz, Christopher J.; Kozlowski, Mark R.

    1998-04-01

    Scratches of measured width were produced on the surface of a IV grade fused silica window using a diamond tip. Two scratch morphologies were observed: plastic and brittle. The scratches were irradiated with a 355 nm laser pulse. The laser-induced damage threshold (LIDT) of the unscratched output surface was 15 J/cm2 at 3-ns. The LIDT of the scratched surface as a function of scratch width was then measured for both input and output surface scratches. Input surface scratches of width smaller than 10 micrometers did not influence the LIDT of the silica window. On the output surface, 7 $mUm wide scratches lowered the LIDT by a factor of two. For larger scratches, the LIDT reached an asymptotic value of 5 J/cm2 on both input and output surface. Possible reasons for this LIDT drop could be electric field enhancement in the cracks below the scratch, the presence of contamination particles in the scratch, or the weakening of the material because of existing mechanical flaws.

  15. Study of laser-induced damage at 1064nm in fused silica samples in vacuum environment

    NASA Astrophysics Data System (ADS)

    Diaz, R.; Chambonneau, M.; Grua, P.; Rullier, J.-L.; Natoli, J.-Y.; Lamaignère, L.

    2015-11-01

    The influence of vacuum on nanosecond laser-induced damage at the exit surface of fused silica components is investigated at 1064 nm. In the present study, as previously observed in air, ring patterns surrounding laserinduced damage sites are systematically observed on a plane surface when initiated by multiple longitudinal modes laser pulses. Compared to air, the printed pattern is clearly more concentrated. The obtained correlation between the damage morphology and the temporal structure of the pulses suggests a laser-driven ablation mechanism resulting in a thorough imprint of energy deposit. The ablation process is assumed to be subsequent to an activation of the surface by hot electrons related to the diffusive expansion of a plasma formed from silica. This interpretation is strongly reinforced with additional experiments performed on an optical grating in vacuum on which damage sites do not show any ring pattern. Qualitatively, in vacuum, the intensity-dependent ring appearance speed V ~ I1/2 is shown to be different than in air where V ~ I1/3 . This demonstrates that the mechanisms of formation of ring patterns are different in vacuum than in air. Moreover, the mechanism responsible of the propagation of the activation front in vacuum is shown to be outdone when experiments are performed in air.

  16. 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

  17. Accelerated life time testing of fused silica upon ArF laser irradiation

    NASA Astrophysics Data System (ADS)

    Mühlig, Ch.; Triebel, W.; Kufert, S.; Natura, U.

    2008-10-01

    We report on two approaches to strongly shorten life time testing of fused silica's absoption degradation upon 193 nm laser irradiation. Both approaches are based on enhancing the two photon absorption (TPA) induced generation of E' and NBOH defects centers in fused silica compared to common marathon test irradiation parameters. For the first approach the irradiation fluence is increased from typical values H<1 mJ/cm2 to H=10 mJ/cm2, therefore increasing the peak laser power for a more efficient TPA process. To avoid microchannel formation in the samples, being a common break-down criterion in marathon tests based on transmission measurements, a small sample of 10 mm length is irradiated and the absorption is measured directly by the laser induced deflection (LID) technique. For comparing the experimental results with a real marathon test at H=1.3 mJ/cm2, an experimental grade sample with very low hydrogen content, i.e. fast absorption changes due to reduced defect annealing, is choosen. During the fluence dependent absorption measurements after the prolonged irradiation at H=10 mJ/cm2 it is found, that both experiments reveal very comparable absorption data for H=1.3 mJ/cm2. For investigating standard material with high hydrogen content, i.e. slow absorption increase due to effective defect annealing, a sample is cooled down to -180 °C in a special designed experimental setup and irradiated at a laser fluence H=10 mJ/cm2. To control the increase of the defect density and to determine the end of the TPA induced defect generation, the fluorescence at 650 nm of the generated NBOH centers is monitored. Before and after the low temperature experiment, the absorption coefficient is measured directly by LID technique. By applying both, elevated laser fluence and low temperature, the ArF laser induced generation of E' and NBOH centers in the investigated sample is terminated after about 1.2*107 laser pulses. Therefore, a strong reduction of irradiation time is achieved

  18. Transmissivity Reduction Of Fracture Due To Silica Precipitation Is Faster For Variable Aperture

    NASA Astrophysics Data System (ADS)

    Pandey, S. N.; Chaudhuri, A.; Kelkar, S.; Rajaram, H.

    2013-12-01

    Geothermal energy have certain ecological benefits as it does not disturb the local ecosystem. It is also able to generate power with minimum operating cost. The extraction of geothermal energy has grown significantly in the past few decades. One of the major challenges for reservoir scale modeling of geothermal system is to describe the exact configuration of aperture fields. Hence the sustainability of geothermal power plant and future estimation of power production is affected during continuous evolution by geochemical and geomechanical processes. The formation of scale due to precipitation of silica in the wells and the fault creates major problem in the sustainability of the geothermal heat extraction. In this study we simulated the reduction of fracture transmissivity due to precipitation by 3-D simulation of coupled thermo-hydro-chemical (THC) processes a simple geothermal system with a horizontal fault, which connects the injection and production wells to facilitate the cold water circulation. The variability of aperture within the fracture/fault is more realistic and it is known that the reduction of effective transmissivity is accelerated by the heterogeneity of the aperture field. The objective of the study is to understand the results of aperture field heterogeneity on the power production. For comparison among different heterogeneous cases, the initial effective transmissivity has been taken same for each. Using numerical simulation of flow between the wells, the same initial effective transmissivity (i.e. same pressure drop between the wells for same mass flow rate) was attained through iteration. The values of standard deviations were taken in the range of 0 to 0.4. Temperature dependent kinetic rate laws were used for the reactive transport modeling. Here the numerical simulations were performed for injection concentration as the solubility at the temperature in the production well. This extreme case is based on the assumption that there is no

  19. Quantitative measurement of CO2 laser-induced residual stress in fused silica optics

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Liao, Wei; Miao, Xinxiang; Yuan, Xiaodong; Zheng, Wanguo; Lv, Haibin; Zhou, Guorui; Zu, Xiaotao; Xiang, Xia

    2015-05-01

    The residual stress field of fused silica induced by continuous wave CO2 laser irradiation is investigated with specific photoelastic methods. Both hoop stress and axial stress in the irradiated zone are measured quantitatively. For the hoop stress along the radial direction, the maximum phase retardance of 30 nm appears at the boundary of the laser distorted zone (680-μm distance to center), and the phase retardance decreases rapidly and linearly inward, and decreases slowly and exponentially outward. For the axial stress, tensile stress lies in a thin surface layer (<280 μm) and compressive stress lies just below the tensile region. Both tensile and compressive stresses increase first and then decrease along the depth direction. The maximum phase retardance induced by axial tensile stress is 150 nm, and the maximum phase retardance caused by axial compression stress is about 75 nm. In addition, the relationship between the maximum axial stress and the deformation height of the laser irradiated zone is also discussed.

  20. Spherical fused silica cells filled with pure helium for nuclear magnetic resonance-magnetometry

    NASA Astrophysics Data System (ADS)

    Maul, Andreas; Blümler, Peter; Heil, Werner; Nikiel, Anna; Otten, Ernst; Petrich, Andreas; Schmidt, Thomas

    2016-01-01

    High magnetic fields (>1 T) are measured by NMR magnetometers with unrivaled precision if the precessing spin sample provides long coherence times. The longest coherence times are found in diluted 3He samples, which can be hyperpolarized for sufficient signal strength. In order to have minimal influence on the homogeneity and value of the measured magnetic field, the optimal container for the 3He should be a perfect sphere. A fused silica sphere with an inner diameter of 8 mm and an outer diameter of 12 mm was made from two hemispheres by diffusion bonding leaving only a small hole for cleaning and evacuation. This hole was closed in vacuum by a CO2 laser and the inner volume was filled with a few mbars of 3He via wall permeation. NMR-measurements on such a sample had coherence times of 5 min. While the hemispheres were produced with <1 μm deviation from sphericity, the bonding left a step of ca. 50 μm at maximum. The influence of such a mismatch, its orientation, and the immediate environment of the sample is analyzed by FEM-simulations and discussed in view of coherence times and absolute field measurements.

  1. Determination of laser damage initiation probability and growth on fused silica scratches

    SciTech Connect

    Norton, M A; Carr, C W; Cross, D A; Negres, R A; Bude, J D; Steele, W A; Monticelli, M V; Suratwala, T I

    2010-10-26

    Current methods for the manufacture of optical components inevitably leaves a variety of sub-surface imperfections including scratches of varying lengths and widths on even the finest finishes. It has recently been determined that these finishing imperfections are responsible for the majority of laser-induced damage for fluences typically used in ICF class lasers. We have developed methods of engineering subscale parts with a distribution of scratches mimicking those found on full scale fused silica parts. This much higher density of scratches provides a platform to measure low damage initiation probabilities sufficient to describe damage on large scale optics. In this work, damage probability per unit scratch length was characterized as a function of initial scratch width and post fabrication processing including acid-based etch mitigation processes. The susceptibility of damage initiation density along scratches was found to be strongly affected by the post etching material removal and initial scratch width. We have developed an automated processing procedure to document the damage initiations per width and per length of theses scratches. We show here how these tools can be employed to provide predictions of the performance of full size optics in laser systems operating at 351 nm. In addition we use these tools to measure the growth rate of a damage site initiated along a scratch and compare this to the growth measured on an isolated damage site.

  2. Stable structure and optical properties of fused silica with NBOHC-E‧ defect

    NASA Astrophysics Data System (ADS)

    Lu, Peng-Fei; Wu, Li-Yuan; Yang, Yang; Wang, Wei-Zheng; Zhang, Chun-Fang; Yang, Chuang-Hua; Su, Rui; Chen, Jun

    2016-08-01

    First-principles method is used to simulate the stable structure and optical properties of a 96-atom fused silica. The preferable structure of NBOHC-E‧ (non-bridging oxygen hole center (NBOHC) and E‧ center) pair defect is predicted to be located at 2.4 Å for the Si–O bond length. The quasi-particle G0W0 calculations are performed and an accurate band gap is obtained in order to calculate the optical absorption properties. With the stretching of the Si1–O1 bond, an obvious redshift can be observed in the absorption spectrum. In the case of NBOHC-E‧ pair, the p-orbital DOS of Si1 atom will shift to the conduction band. Two obvious absorption peaks can be observed in the absorption spectrum. The calculation reproduced the peak positions of the well-known optical absorption bands. Project supported by the National Basic Research Program of China (Grant No. 2014CB643900), the Open Fund of IPOC (BUPT), the Open Program of State Key Laboratory of Functional Materials for Informatics, the National Natural Science Foundation for Theoretical Physics Special Fund “Cooperation Program” (Grant No. 11547039), and Shaanxi Provincial Institute of Scientific Research Plan Projects, China (Grant No. SLGKYQD2-05).

  3. Dynamics of femtosecond laser absorption of fused silica in the ablation regime

    SciTech Connect

    Lebugle, M. Sanner, N.; Varkentina, N.; Sentis, M.; Utéza, O.

    2014-08-14

    We investigate the ultrafast absorption dynamics of fused silica irradiated by a single 500 fs laser pulse in the context of micromachining applications. A 60-fs-resolution pump-probe experiment that measures the reflectivity and transmissivity of the target under excitation is developed to reveal the evolution of plasma absorption. Above the ablation threshold, an overcritical plasma with highly non-equilibrium conditions is evidenced in a thin layer at the surface. The maximum electron density is reached at a delay of 0.5 ps after the peak of the pump pulse, which is a strong indication of the occurrence of electronic avalanche. The results are further analyzed to determine the actual feedback of the evolution of the optical properties of the material on the pump pulse. We introduce an important new quantity, namely, the duration of absorption of the laser by the created plasma, corresponding to the actual timespan of laser absorption by inverse Bremsstrahlung. Our results indicate an increasing contribution of plasma absorption to the total material absorption upon raising the excitation fluence above the ablation threshold. The role of transient optical properties during the energy deposition stage is characterized and our results emphasize the necessity to take it into account for better understanding and control of femtosecond laser-dielectrics interaction.

  4. Nanocrystalline diamond microelectrode on fused silica optical fibers for electrochemical and optical sensing

    NASA Astrophysics Data System (ADS)

    Bogdanowicz, Robert; Sobaszek, Michał; Ficek, Mateusz; Gnyba, Marcin; Ryl, Jacek; Siuzdak, Katarzyna; Śmietana, Mateusz

    2015-07-01

    Fabrication process of thin boron-doped nanocrystalline diamond (B-NCD) microelectrode on fused silica single mode optical fiber has been investigated. The B-NCD films were deposited on the fibers using Microwave Plasma Assisted Chemical Vapor Deposition (MW PA CVD) at glass substrate temperature of 475 ºC. We have obtained homogenous, continuous and polycrystalline surface morphology with the mean grain size in the range of 100-250 nm and high sp3 content in B-NCD films. The films deposited on glass reference samples exhibit high refractive index (n≍2.05 at λ=550 nm) and low extinction coefficient. Furthermore, cyclic voltammograms (CV) were recorded to determine the electrochemical window and reaction reversibility at the B-NCD fibre-based electrode. Cyclic voltammetry (CV) measurements in aqueous media consisting of 5mM K3[Fe(CN)6] in 0.1M Na2SO4 demonstrated a width of the electrochemical window up to 2.5 V and relatively fast kinetics expressed by a redox peak splitting below 500 mV. Moreover, thanks to high-n B-NCD overlay, the coated fibers can be also used for enhancing sensitivity of long-period gratings (LPGs) induced in the fibers. The LPG is capable for measuring variations in refractive index of surrounding liquid by tracing shift in resonance appearing in transmitted spectrum. Possible combined CV and LPG-based measurements are discussed in this work.

  5. Examination of Relationship Between Photonic Signatures and Fracture Strength of Fused Silica Used in Orbiter Windows

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cramer, K. Elliott; Estes, Linda R.; Salem, Jonathan A.; Lankford, James, Jr.; Lesniak, Jon

    2011-01-01

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outermost pane of the orbiter windows. Four categories of damage: hyper-velocity impacts that occur during space-flight (HVI); hypervelocity impacts artificially made at the Hypervelocity Impact Technology Facility (HIT-F); impacts made by larger objects falling onto the pane surface to simulate dropped items on the window during service/storage of vehicle (Bruises); and light scratches from dull objects designed to mimic those that might occur by dragging a dull object across the glass surface (Chatter Checks) are examined. The damage sites are cored from fused silica window carcasses, examined with the GFP and other methodologies, and broken using the ASTM Standard C1499-09 to measure the fracture strength. A correlation is made between the fracture strength and damage-site measurements including geometrical measurements and GFP measurements of photoelastic retardation (stress patterns) surrounding the damage sites. An analytical damage model to predict fracture strength from photoelastic retardation measurements is presented and compared with experimental results.

  6. Fracture Strength of Fused Silica From Photonic Signatures Around Collision Sites

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cramer, K Elliott

    2015-01-01

    Impact sites in glass affect its fracture strength. An analytical model that predicts fracture strength from grey-field polariscope (GFP) readings (photoelastic retardations) has been developed and reported in the literature. The model is suggestive that stress fields, resulting from impact damage, destablizes sites within the glass, which lead to pathways that cause strength degradation. Using data collected from fused silica specimens fabricated from outer window panes that were designed for the space shuttle, the model was tested against four categories of inflicted damage. The damage sites were cored from the window carcasses, examined with the GFP and broken using the ASTM Standard C1499-09 to measure the fracture strength. A correlation is made between the fracture strength and the photoelastic retardation measured at the damage site in each specimen. A least-squares fit is calculated. The results are compared with the predictions from the model. A plausible single-sided NDE damage site inspection method (a version of which is planned for glass inspection in the Orion Project) that relates photoelastic retardation in glass components to its fracture strength is presented.

  7. MRF, ELSM and STED: tools to study defects in fused silica optics

    NASA Astrophysics Data System (ADS)

    Catrin, R.; Taroux, D.; Cormont, P.; Maunier, C.; Neauport, J.

    2013-11-01

    The MegaJoule laser being constructed at the CEA near Bordeaux (France) is designed to focus more than 1 MJ of energy at 351 nm, on a millimetre scale target in the centre of an experiment chamber. The final optic assembly of this system operating at a wavelength of 351 nm is made up of large fused silica optics, working in transmission, that are used to convey and focus the laser beam. Under high fluences (i.e. more than 5 J/cm2 for 3 ns pulses), the limited lifetime of final optical assembly is a major concern for fusion scale laser facilities. Previous works have shown that surface finishing processes applied to manufacture these optical components can leave subsurface cracks (SSD), pollution or similar defects that act as initiators of the laser damage. In this work, we used epi-fluorescent light scanning microscopy (ELSM) and Stimulated Emission Depletion (STED) in confocal mode with fluorescent dye tagging to get a better knowledge of size and depth of these subsurface cracks. Magnetorheological fluid finishing technique (MRF) was also used as a tool to remove these cracks and thus assess depths measured by confocal microscopy. Subsurface cracks with a width of about 120 nm are observed up to ten micrometers below the surface.

  8. Microstructuring of fused silica using femtosecond laser pulses of various wavelengths

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Manuel; Engel, Andy; Reisse, Guenter; Weissmantel, Steffen

    2015-11-01

    Experimental results on ablation and microstructuring of fused silica (Corning 7980 HPFS Standard Grade) using femtosecond laser pulses will be presented. In particular, the ablation behavior of the material at the laser wavelengths of 775, 387 and 258 nm was investigated. The qualities of selected microstructures produced at the different wavelengths are compared with respect to roughness, crack formation and exactness. The investigations were carried out using an automated microstructuring system equipped with a femtosecond laser Clark-MXR CPA 2010 (1 mJ maximum pulse energy, 1 kHz repetition rate and 150 fs pulse duration). Layer-by-layer ablation is realized for producing 3D microstructures, where the layer thickness depends on the ablated depth per laser pulse. Those ablation depths depend on the material and the laser parameters and were determined for the three wavelengths in preparatory investigations. Therefore, the laser fluence and the pulse-to-pulse distance were varied independently. We will present the results of our fundamental studies on fs-laser ablation at the three wavelengths and show several structures, such as pyramids, half spheres and cones. Best results were obtained at 258 nm wavelength. There, the exactness was highest and the roughness of the surfaces of the structures was lowest. In addition, absolutely no crack formation occurred.

  9. Comprehensive modeling of structural modification induced by a femtosecond laser pulse inside fused silica glass

    NASA Astrophysics Data System (ADS)

    Najafi, Somayeh; Sadat Arabanian, Atoosa; Massudi, Reza

    2016-06-01

    A comprehensive theoretical model is proposed based on equations describing the nonlinear propagation of an ultrashort pulse inside transparent material, electron density evolution, non-Fourier heat conduction, and thermo-elasto plastic displacement which are respectively solved by various methods. These methods include the split-step finite difference technique and alternating-direction implicit algorithm, fourth-order Range–Kutta algorithm, hybrid finite-element method/finite-difference method, and finite-element method in both space and time to achieve refractive index changes. The whole chain of processes occurring in the interaction of a focused ultrashort laser pulse with fused silica glass in prevalent conditions of micromachining applications is numerically investigated. By optimizing the numerical method and by using an adaptive mesh approach, the execution time of the program is significantly reduced so that the calculations are done at each time step in a fraction of a second. Simulation results show that the energy and duration of the input pulse are very important parameters in induced changes, but the chirp of the input pulse is not an effective parameter. Consequently, by appropriate setting of those parameters one can design a desired refractive index profile.

  10. Effect of a Silicone Contaminant Film on the Transmittance Properties of AR-coated Fused Silica

    NASA Technical Reports Server (NTRS)

    Boeder, Paul A.; Visentine, James T.; Shaw, Christopher G.; Carniglia, Charles K.; Ledbury, Eugene A.; Alred, John W.; Soares, Carlos E.

    2004-01-01

    We present the results of a laboratory test to determine the effects of bulk deposited, DC-704 silicone contaminant film on the transmittance properties of an anti-reflective (AR) coated fused silica optical substrate. Testing and optical measurements were performed in vacuum in the Boeing Combined Effects Test Facility (CETF). The test and measurement procedures are described herein. Measurement results are presented showing the change in transmittance characteristics as a function of contaminant deposit thickness and vacuum ultra-violet (vuv) exposure levels. Measurement results show an initial degradation in the transmittance of the contaminated sample. This is followed by a partial recovery in sample transmittance as the sample is exposed to additional VUV radiation. Transmittance results also show a loss of transmission in the ultraviolet portion of the spectrum and an increase in transmission in the infrared portion of the spectrum. These transmittance results are characteristic of thin-film interference effects. Thin-film analyses indicate that some of the observed transmittance results can be successfully modeled, but only if the contaminant film is assumed to be SiO2 rather than DC-704 silicone. Post-test Scanning Electron Microscope (SEM) scans of the test sample indicate the formation of contaminant islands and the presence of a thin uniform coating of contaminant deposit on the sample

  11. Laser-induced gas plasma etching of fused silica under ambient conditions

    NASA Astrophysics Data System (ADS)

    Elhadj, Selim; Guss, Gabe; Matthews, Manyalibo J.; Bass, Isaac

    2012-11-01

    Laser machining of optics to mitigate surface defects has greatly enhanced the ability to process large optics such as those found in fusion-class lasers. Recently, the use of assist reactive gases has shown promise in enhancing manifold etching rates relative to ambient conditions for CW-laser exposures. However, these methods still require significant heating of the substrate that induce residual stress, redeposit coverage, material flow, and compromise the final surface finish and damage threshold. While very reactive fluorinated gases are capable to reduce treatment temperatures even further, they are also inherently toxic and not readily transferable to large processing facilities. In this report, we look at whether a short-lived gas plasma could provide the safe and effective etchant sought, while still reducing the thermal load on the surface. We test this approach using a YAG laserinduced gas plasma to act as a source of the etchant for fused silica, a common optical material. The configuration and orientation of the beam and optical apparatus with respect to the surface was critical in preventing surface damage while etching the surface. Results with N2 and air gas plasmas are shown, along with a description of the various experimental implementations attempted.

  12. Two-photon induced fluorescence and other optical effects in irradiated and doped fused silica

    SciTech Connect

    Kramer, S.D.

    1986-07-01

    The objective of this program was to assess and identify irradiation techniques which could be used to modify the optical charactistics of doped fused silica. Primary emphasis was placed on determining if gamma ray or neutron bombardment of the glass would enhance certain Raman and nonlinear optical effects. In particular, the effect of irradiation on optical two photon induced fluorescence was studied in detail. The maximum radiation exposures used were 10/sup 6/ rads (Si) of gamma rays and neutron fluences of 1 x 10/sup 14/ neutrons/cm/sup 2/. The optical measurements were made at room temperature between one and four months after irradiation. The maximum input light intensity was 10/sup 9/ watts/cm/sup 2/ at a near infrared (1.06 ..mu..) input wavelength which was chosen to lie in a transparent spectral region of the glass. Under these experimental conditions a careful search revealed no detectable two-photon induced fluorescence in the region from 550 to 900 nm. The upper limit for the photon efficiency of this process was determined to be less than 1 x 10/sup -10/%. 89 refs., 12 figs.

  13. Study of laser-induced fatigue effects in synthetic fused silica in the UV

    NASA Astrophysics Data System (ADS)

    Gouldieff, C.; Wagner, F. R.; Natoli, J.-Y.

    2014-10-01

    In the last decades, the resistance to high-power laser flux was largely improved in most of optical components insofar as 1-on-1 measurements are concerned. Another challenge lies in improving their resistance to multiple laser shots for highpower laser applications. Indeed, in multi-pulse irradiation, a decrease of the laser-induced damage threshold with increasing number of pulse was observed in various optical materials as in glasses, crystals, and thin-films. This effect, commonly denominated "fatigue" effect, is a limiting factor in many applications where optics have to be long-lifetime, as for example for space applications. Representing the laser damage probability as a function of pulse number for a given fluence allows to distinguish statistical pseudo-fatigue and fatigue which is due to cumulative material modifications. Investigating on the fatigue effects in the bulk of synthetic fused silica (Suprasil 1®) for different wavelengths, we evidenced that the fatigue effect was due to statistical pseudo-fatigue when irradiated at 1064 nm while the fatigue effect at 355 nm came from cumulative material modifications. The current work is dedicated a more detailed study of fatigue effects in Suprasil 1®, testing the influence of the beam size on the fatigue effects. Moreover, an estimation of the lifetime of the created defects is performed using a destructive technique.

  14. Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Frey, Bradley J.

    2006-01-01

    Using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have measured the absolute refractive index of five specimens taken from a very large boule of Corning 7980 fused silica from temperatures ranging from 30 to 310 K at wavelengths from 0.4 to 2.6 microns with an absolute uncertainty of plus or minus 1 x 10 (exp -5). Statistical variations in derived values of the thermo-optic coefficient (dn/dT) are at the plus or minus 2 x 10 (exp -8)/K level. Graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient are presented for selected wavelengths and temperatures along with estimates of uncertainty in index. Coefficients for temperature-dependent Sellmeier fits of measured refractive index are also presented to allow accurate interpolation of index to other wavelengths and temperatures. We compare our results to those from an independent investigation (which used an interferometric technique for measuring index changes as a function of temperature) whose samples were prepared from the same slugs of material from which our prisms were prepared in support of the Kepler mission. We also compare our results with sparse cryogenic index data from measurements of this material from the literature.

  15. Multi-pulse LIBDE of fused silica at different thicknesses of the organic absorber layer

    NASA Astrophysics Data System (ADS)

    Pan, Yunxiang; Ehrhardt, Martin; Lorenz, Pierre; Han, Bing; Hopp, Bela; Vass, Csaba; Ni, Xiaowu; Zimmer, Klaus

    2015-12-01

    Laser-induced etching techniques feature several unique characteristics that enable ultraprecise machining of transparent materials. However, LIBDE (laser-induced back side dry etching) and LIBWE (laser-induced back side wet etching) are preferentially studied due to experimental feasibilities either using a very thin or a bulk absorber at the rear side of the transparent material. This study aims to fill the gap by examining the thickness dependence of the absorbing material. Multi-pulse-LIBDE (MP-LIBDE) of fused silica using different thick photoresist absorber layers (dL = 0.2-11.7 μm) was performed with a KrF excimer laser (λ = 248 nm, tp ≈ 20 ns). The influence of several experimental parameters, such as laser fluence, pulse number, film thickness, on the ablation morphology and the etching rate were investigated. Especially at moderate fluences (F = 0.7-1.5 J/cm2) MP-LIBDE and LIBWE show several similar process characteristics such as the etching rate dependence on the laser fluence and the pulse number with a typical etching rate of approx. 12 nm at 1 J/cm2. However, the specific etching rate values depend on the absorber layer thickness, for instance. The morphology of the etched surface is smooth with a roughness of below 5 nm rms. Further, the modification of the surface has been observed and will be discussed in relation to the multi-pulse laser etching mechanism.

  16. Filamentation and damage in fused silica induced by tightly focused femtosecond laser pulses

    SciTech Connect

    Couairon, A.; Sudrie, L.; Franco, M.; Prade, B.; Mysyrowicz, A.

    2005-03-15

    We investigate experimentally and numerically the damage tracks induced by tightly focused (NA=0.5) infrared femtosecond laser pulses in the bulk of a fused silica sample. Two types of irreversible damage are observed. The first damage corresponds to a permanent change of refractive index without structural modifications (type I). It appears for input pulse energies beyond 0.1 {mu}J. It takes the form of a narrow track extending over more than 100 {mu}m at higher input powers. It is attributed to a change of the polarizability of the medium, following a filamentary propagation which generates an electron-hole plasma through optical field ionization. A second type of damage occurs for input pulse energies beyond 0.3 {mu}J (type II). It takes the form of a pear-shaped structural damage associated with an electron-ion plasma triggered by avalanche. The temporal evolution of plasma absorption is studied by pump-probe experiments. For type I damage, a fast electron-hole recombination is observed. Type II damage is linked with a longer absorption.

  17. Capillary isoelectric focusing of proteins and microorganisms in dynamically modified fused silica with UV detection.

    PubMed

    Horká, Marie; Růzicka, Filip; Horký, Jaroslav; Holá, Veronika; Slais, Karel

    2006-09-01

    We suggest a method for the reproducible and efficient capillary isoelectric focusing of proteins and microorganisms in the pH gradient 3-10. The method involves the segmental injection of the simple ampholytes, the solution of the selected electrolytes, and the sample mixture of bioanalytes and carrier ampholytes to the fused silica capillaries dynamically modified by poly(ethylene glycol), PEG 4000, which is added to the catholyte, the anolyte and injected solutions. In order to receive the reproducible results, the capillaries were rinsed by the mixture of acetone/ethanol between analyses. For the tracing of the pH gradients the low-molecular-mass pI markers were used. The simple proteins and the mixed cultures of microorganisms, Saccharomyces cerevisiae CCM 8191, Escherichia coli CCM 3954, Candida albicans CCM 8180, Candida parapsilosis, Candida krusei, Staphylococcus aureus, Streptococcus agalactiae CCM 6187, Enterococcus faecalis CCM 4224, Staphylococcus epidermidis CCM 4418 and Stenotrophomonas maltophilia, were focused and separated by the method suggested. The minimum detectable number of microbial cells was 5x10(2) to 1x10(3) with on-column UV detection at 280 nm. PMID:16765111

  18. Measuring sub-nm adsorbed water layer thickness and desorption rate using a fused-silica whispering-gallery microresonator

    NASA Astrophysics Data System (ADS)

    Ganta, D.; Dale, E. B.; Rosenberger, A. T.

    2014-05-01

    We report an optical method for measuring the thickness of the water layer adsorbed onto the surface of a high-Q fused-silica microresonator. Light from a tunable diode laser operating near 1550 nm is coupled into the microresonator to excite whispering-gallery modes (WGMs). By observing thermal distortion or even bistability of the WGM resonances caused by absorption in the water layer, the contribution of that absorption to the total loss is determined. Thereby, the thickness of the water layer is found to be ˜0.1 nm (approximately one monolayer). This method is further extended to measure the desorption rate of the adsorbed water, which is roughly exponential with a decay time of ˜40 h when the fused-silica microresonator is held in a vacuum chamber at low pressure.

  19. 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

  20. Subwavelength structures for high power laser antireflection application on fused silica by one-step reactive ion etching

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Jiang, Xiao-Dong; Huang, Jin; Sun, Lai-Xi; Geng, Feng; Yi, Zao; Zu, Xiao-Tao; Wu, Wei-Dong; Zheng, Wanguo

    2016-03-01

    In this paper we report a simple method to fabricate a novel subwavelength structure surface on fused silica substrate using one-step reactive ion etching with two-dimensional polystyrene colloidal crystals as masks. The etching process and the morphologies of the obtained structure are controlled. We show that the period of the obtained fused silica pillar-like arrays were determined by the initial polystyrene nanoparticle size. The height of pillar arrays can be adjusted by controlling the etching duration, which is proved to be of importance in tailoring the antireflection properties of subwavelength structures surface. The novel subwavelength structures surface exhibit excellent broadband antireflection properties, but the size of the pillar affects the antireflective properties in short wavelength region. We anticipate this method would offer a convenient and scalable way for inexpensive and high-efficiency high power laser field designs.

  1. An AC phase measuring interferometer for measuring dn/dT of fused silica and calcium fluoride at 193 nm

    SciTech Connect

    Shagam, R.N.

    1998-09-01

    A novel method for the measurement of the change in index of refraction vs. temperature (dn/dT) of fused silica and calcium fluoride at the 193 nm wavelength has been developed in support of thermal modeling efforts for the development of 193 nm-based photolithographic exposure tools. The method, based upon grating lateral shear interferometry, uses a transmissive linear grating to divide a 193 nm laser beam into several beam paths by diffraction which propagate through separate identical material samples. One diffracted order passing through one sample overlaps the undiffracted beam from a second sample and forms interference fringes dependent upon the optical path difference between the two samples. Optical phase delay due to an index change from heating one of the samples causes the interference fringes to change sinusoidally with phase. The interferometer also makes use of AC phase measurement techniques through lateral translation of the grating. Results for several samples of fused silica and calcium fluoride are demonstrated.

  2. 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.

  3. Improve the laser damage resistance of fused silica by wet surface cleaning and optimized HF etch process

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaolong; Liu, Ying; Rao, Huanle; Fu, Shaojun

    2013-07-01

    Fabrication-induced metal contaminations and subsurface damage are generally identified as the laser damage initiators that are responsible for the laser induced damage in fused silica. In this paper, the removal of those two initiators are realized by two methods: wet chemical surface cleaning and optimized HF-based etch process. Two kinds of chemical leaching are used to removing the Ce and other metal impurities respectively. In order prevent the redeposition of the reactive byproducts during HF etch process, we optimized the traditional HF etch process in two ways: absence of NH4F in etch solution and presence of megasonic and ultrasonic agitation during and after etch respectively. And laser damage tests show that these two treatments greatly improve the laser damage resistance of fused silica.

  4. Time-resolved shadowgraphs of transient plasma induced by spatiotemporally focused femtosecond laser pulses in fused silica glass.

    PubMed

    Wang, Zhaohui; Zeng, Bin; Li, Guihua; Xie, Hongqiang; Chu, Wei; He, Fei; Liao, Yang; Liu, Weiwei; Gao, Hui; Cheng, Ya

    2015-12-15

    We report on experimental observations of formation and evolution of transient plasma produced in fused silica glass with spatiotemporally focused (STF) femtosecond laser pulses using a pump-probe shadow imaging technique. Surprisingly, the observation shows that the track of the plasma is significantly curved, which is attributed to an asymmetric density distribution of the transient plasma produced in the focal volume caused by the pulse front tilt of the STF laser field. PMID:26670497

  5. Study of the effects of polishing, etching, cleaving, and water leaching on the UV laser damage of fused silica

    SciTech Connect

    Yoshiyama, J.; Genin, F.Y.; Salleo, A.; Thomas, I.; Kozlowski, M.R.; Sheehan, L.M.; Hutcheon, I.D.; Camp, D.W.

    1997-12-23

    A damage morphology study was performed with a 355 nm Nd:YAG laser on synthetic UV-grade fused silica to determine the effects of post- polish chemical etching on laser-induced damage, compare damage morphologies of cleaved and polished surfaces, and understand the effects of the hydrolyzed surface layer and waste-crack interactions. The samples were polished , then chemically etched in buffered HF solution to remove 45,90,135, and 180 nm of surface material. Another set of samples was cleaved and soaked in boiling distilled water for 1 second and 1 hour. All the samples were irradiated at damaging fluencies and characterized by Normarski optical microscopy and scanning electron microscopy. Damage was initiated as micro-pits on both input and output surfaces of the polished fused silica sample. At higher fluencies, the micro-pits generated cracks on the surface. Laser damage of the polished surface showed significant trace contamination levels within a 50 nm surface layer. Micro-pit formation also appeared after irradiating cleaved fused silica surfaces at damaging fluences. Linear damage tracks corresponding cleaving tracks were often observed on cleaved surfaces. Soaking cleaved samples in water produced wide laser damage tracks.

  6. Optical absorption in fused silica at elevated temperatures during 1.5-MeV electron irradiation

    NASA Technical Reports Server (NTRS)

    Smith, A. B.

    1972-01-01

    An experimental determination of the optical transmission of Corning 7940 UV and Suprasil 1 and 2 fused silica has been made during 1.5-MeV electron bombardment. The fused silica reached temperatures ranging from 150 to 1000 C. The Lewis Research Center dynamitron provided electron current densities which corresponded to a dose rate of 2.6 to 20 Mrad/sec. The irradiation induced absorption was measured at 215.0, 270.0, and 450.0 nm (2150, 2700, 4500 A). The length of each irradiation was sufficient so that an equilibrium between radiation induced coloration and high temperature annealing was reached. The experimental results indicate a significant optical absorption, with values of the induced absorption coefficient at 215.0 nm (2150 A) of 14.5 to 2.2/cm, at 270.0 nm (2700 A) of 9.7 to 3.0/cm and at 450.0 nm (4500 A) of 3.7 to 0.5/cm. This would make the use of fused silica as the separating wall material in the nuclear light bulb propulsion concept questionable.

  7. Signal Enhancement of Abiotically-Synthesized RNA Oligonucleotides and other Biopolymers using Unmodified Fused Silica in MALDI-MS

    NASA Astrophysics Data System (ADS)

    Cassidy, Lauren M.; Dong, Yingying; Joshi, Prakash C.; Aldersley, Michael F.; Ferris, James P.; McGown, Linda B.

    2011-06-01

    Metal is the standard desorption platform for MALDI-MS but other surfaces have been shown to offer advantages for particular types of analytes or applications. One such substrate is fused silica, which has been employed for matrix-free detection of low mass analytes and for affinity MALDI-MS in which binding ligands are immobilized at the fused silica surface. The present work reports improved MALDI-MS detection of RNA oligonucleotides, including polyA, polyU, and polyA/U, at the high end of the mass range when unmodified fused silica is used instead of stainless steel as the MALDI target. The RNA oligonucleotides were abiotically synthesized from activated monomers on catalytic clay surfaces. Further investigation found enhanced signals as well for other anionic biopolymers, including DNA oligonucleotides and heparin. Enhancement also was observed for dextran, which is neutral, indicating that the effect is not restricted to anionic biopolymers. Among more general analytical applications, the results are particularly relevant to rapid screening of abiotic RNA polymerization toward elucidating pathways to life on Earth.

  8. Imaging the early material response associated with exit surface damage in fused silica

    SciTech Connect

    Demos, S G; Raman, R N; Negres, R A

    2010-11-05

    The processes involved at the onset of damage initiation on the surface of fused silica have been a topic of extensive discussion and thought for more than four decades. Limited experimental results have helped develop models covering specific aspects of the process. In this work we present the results of an experimental study aiming at imaging the material response from the onset of the observation of material modification during exposure to the laser pulse through the time point at which material ejection begins. The system involves damage initiation using a 355 nm pulse, 7.8 ns FWHM in duration and imaging of the affected material volume with spatial resolution on the order of 1 {micro}m using as strobe light a 150 ps laser pulse that is appropriately timed with respect to the pump pulse. The observations reveal that the onset of material modification is associated with regions of increased absorption, i.e., formation of an electronic excitation, leading to a reduction in the probe transmission to only a few percent within a time interval of about 1 ns. This area is subsequently rapidly expanding with a speed of about 1.2 {micro}m/ns and is accompanied by the formation and propagation of radial cracks. These cracks appear to initiate about 2 ns after the start of the expansion of the modified region. The damage sites continue to grow for about 25 ns but the mechanism of expansion after the termination of the laser pulse is via formation and propagation of lateral cracks. During this time, the affected area of the surface appears to expand forming a bulge of about 40 {micro}m in height. The first clear observation of material cluster ejection is noted at about 50 ns delay.

  9. Imaging of single-chromophore molecules in aqueous solution near a fused-silica interface

    NASA Astrophysics Data System (ADS)

    Davis, Lloyd M.; Parker, Wesley C.; Ball, David A.; Williams, John G.; Bashford, Greg R.; Sheaff, Pamela; Eckles, Robert D.; Lamb, Don T.; Middendorf, Lyle R.

    2001-04-01

    Single molecules of unconjugated Bodipy-Texas Red (BTR), BTR-dimer, and BTR conjugated to cysteine, in aqueous solutions are imaged using total-internal-reflection excitation and through-sample collection of fluorescence onto an intensified CCD camera, or a back-illuminated frame transfer CCD. The sample excitation is provided by the beam from a continuous-wave krypton ion laser, or a synchronously-pumped dye laser, operating at 568 nm. In order to essentially freeze molecular motion due to diffusion and thereby enhance image contrast, the laser beam is first passed through a mechanical shutter, which yields a 3-millisecond laser exposure for each camera frame. The laser beam strikes the fused-silica/sample interface at an angle exceeding the critical angle by about 1 degree. The resultant evanescent wave penetrates into the sample a depth of approximately 0.3 microns. Fluorescence from the thin plane of illumination is then imaged onto the camera by a water immersion apochromat (NA 1.2, WD 0.2mm). A Raman notch filter blocks Rayleigh and specular laser scatter and a band-pass-filter blocks most Raman light scatter that originates from the solvent. Single molecules that have diffused into the evanescent zone at the time of laser exposure yield near-diffraction-limited Airy disk images with diameters of ~5 pixels. While most molecules diffuse out of the evanescent zone before the next laser exposure, stationary or slowly moving molecules persisting over several frames, and blinking of such molecules are occasionally observed.

  10. Effect of liquid environment on laser-induced backside wet etching of fused silica

    NASA Astrophysics Data System (ADS)

    Lee, Taehwa; Jang, Deoksuk; Ahn, Daehwan; Kim, Dongsik

    2010-02-01

    In laser-induced backside wet etching (LIBWE), the liquid absorbent indirectly heats the transparent material, causing explosive phase change and cavitation. Accordingly, the hydrodynamics of the absorbing liquid, including the size of the liquid chamber, is strongly related to the ablation process. Because the hydrodynamics is dependent on the elastic deformation of the sample, the sample thickness also affects the performance of LIBWE. In this work, experimental analyses were performed to elucidate the hydrodynamics in LIBWE and the effect on the etch rate by varying the liquid chamber size and sample thickness. A KrF excimer laser was used to ablate fused silica samples in toluene and the etch rate was quantified using a scanning profilometer. Laser flash shadowgraphy and photodeflection probing techniques were employed for in situ measurement of the laser-induced hydrodynamics and displacement of the sample, respectively, with a time resolution of approximately nanoseconds. To directly observe the effect of increased liquid pressure on LIBWE, the liquid pressure on the etching spot was locally increased by an external shock wave and the etch results are examined. This study confirms that the photomechanical effects from the laser-induced bubble plays a key role in the LIBWE process, revealing a linear relationship between the etch rate the applied recoil momentum. However, the dependence of the etch rate on the chamber size and sample thickness could not be explained by the change in recoil momentum, i.e., by the bubble pressure. Instead, transient deformation of the sample by the pressure impact was estimated to be mainly responsible for the dependence.

  11. Crystallization of fused silica surfaces by ultra-violet laser irradiation

    NASA Astrophysics Data System (ADS)

    Hirata, Kazuya; Haraguchi, Koshi

    2012-07-01

    In recent years, the increased use of high power lasers has created problems in optical elements due to laser damage. The International Organization for Standardization (ISO) describes in a publication ISO 11254 a laser-power resilience (LPR) test which we used to verify that by flattening the glass substrate of an optical element, we could improve the resistance to laser damage. We report on an evaluation of two types of samples of fused silica substrate whose surface roughness differed (Ra = 0.20 nm and Ra = 0.13 nm) using customized on-line laser damage testing. To induce laser damage to samples, we used the fifth harmonic generation from a Nd:YAG pulse laser (wavelength: 213 nm, pulse width: 4 ns, repetition frequency: 20 Hz). Results show that flattening reduced the progression of laser damage in the meta-phase laser damage phase by 1/3 of that without flattening. However, pro-phase laser damage which started at fluence 2.39 J/cm2 was unrelated to surface roughness. To analyze the pro-phase laser damage, we used x-ray diffraction (XRD), Raman spectroscopy, and variable pressure-type scanning electron microscopy (VP-SEM). From XRD data, we observed XRD patterns of cristobalite (111), cristobalite (102), α-quartz (111), and β-quartz (102). Raman spectrum data showed an increase in the three-membered ring vibration (600 cm-1), four-membered ring vibration (490 cm-1), and many-membered ring vibration (450 cm-1, 390 cm-1, and 300 cm-1). We observed patchy crystallized areas on the sample surfaces in the VP-SEM images. Based on these experimental results, we believe that the dominant factors in pro-phase laser damage are their physical properties. Substrate and thin film material must be appropriately selected in producing an optical element with a high level of resilience to laser exposure.

  12. Sub-surface mechanical damage distributions during grinding of fused silica

    SciTech Connect

    Suratwala, T I; Wong, L L; Miller, P E; Feit, M D; Menapace, J A; Steele, R A; Davis, P A; Walmer, D

    2005-11-28

    The distribution and characteristics of surface cracking (i.e. sub-surface damage or SSD) formed during standard grinding processes has been investigated on fused silica glass. The SSD distributions of the ground surfaces were determined by: (1) creating a shallow (18-108 {micro}m) wedge/taper on the surface by magneto-rheological finishing; (2) exposing the SSD by HF acid etching; and (3) performing image analysis of the observed cracks from optical micrographs taken along the surface taper. The observed surface cracks are characterized as near-surface lateral and deeper trailing indent type fractures (i.e., chatter marks). The SSD depth distributions are typically described by a single exponential distribution followed by an asymptotic cutoff in depth (c{sub max}). The length of the trailing indent is strongly correlated with a given process. Using established fracture indentation relationships, it is shown that only a small fraction of the abrasive particles are being mechanically loaded and causing fracture, and it is likely the larger particles in the abrasive particle size distribution that bear the higher loads. The SSD depth was observed to increase with load and with a small amount of larger contaminant particles. Using a simple brittle fracture model for grinding, the SSD depth distribution has been related to the SSD length distribution to gain insight into ''effective'' size distribution of particles participating in the fracture. Both the average crack length and the surface roughness were found to scale linearly with the maximum SSD depth (c{sub max}). These relationships can serve as useful rules-of-thumb for nondestructively estimating SSD depth and to identify the process that caused the SSD. In certain applications such as high intensity lasers, SSD on the glass optics can serve as a reservoir for minute amounts of impurities that absorb the high intensity laser light and lead to subsequent laser-induced surface damage. Hence a more scientific

  13. On-machine precision preparation and dressing of ball-headed diamond wheel for the grinding of fused silica

    NASA Astrophysics Data System (ADS)

    Chen, Mingjun; Li, Ziang; Yu, Bo; Peng, Hui; Fang, Zhen

    2013-09-01

    In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter, the existing dressing methods are not suitable to dress the ball-headed diamond wheel precisely due to that they are either on-line in process dressing which may causes collision problem or without consideration for the effects of the tool setting error and electrode wear. An on-machine precision preparation and dressing method is proposed for ball-headed diamond wheel based on electrical discharge machining. By using this method the cylindrical diamond wheel with small diameter is manufactured to hemispherical-headed form. The obtained ball-headed diamond wheel is dressed after several grinding passes to recover geometrical accuracy and sharpness which is lost due to the wheel wear. A tool setting method based on high precision optical system is presented to reduce the wheel center setting error and dimension error. The effect of electrode tool wear is investigated by electrical dressing experiments, and the electrode tool wear compensation model is established based on the experimental results which show that the value of wear ratio coefficient K' tends to be constant with the increasing of the feed length of electrode and the mean value of K' is 0.156. Grinding experiments of fused silica are carried out on a test bench to evaluate the performance of the preparation and dressing method. The experimental results show that the surface roughness of the finished workpiece is 0.03 μm. The effect of the grinding parameter and dressing frequency on the surface roughness is investigated based on the measurement results of the surface roughness. This research provides an on-machine preparation and dressing method for ball-headed metal bonded diamond wheel used in the grinding of fused silica, which provides a solution to the tool setting method and the effect of electrode tool wear.

  14. Fabrication of microcapillaries in fused silica using axicon focusing of femtosecond laser radiation and chemical etchingion/ms

    SciTech Connect

    Yashunin, D A; Malkov, Yu A; Stepanov, A N

    2013-04-30

    Fabrication of microcapillaries with a diameter of 50 - 80 {mu}m and a length up to 2.5 mm in fused silica by axicon focusing of femtosecond laser radiation and subsequent chemical etching in a 8 % hydrofluoric acid solution is demonstrated. The etching rate is {approx}6 {mu}m min{sup -1}. It is shown that the microcapillaries have optical waveguiding properties, which testifies to the optical quality of the walls of obtained structures. (extreme light fields and their applications)

  15. Tuning etch selectivity of fused silica irradiated by femtosecond laser pulses by controlling polarization of the writing pulses

    SciTech Connect

    Yu Xiaoming; Zeng Bin; Liao Yang; He Fei; Cheng Ya; Xu Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2011-03-01

    We report on experimental study on chemical etch selectivity of fused silica irradiated by femtosecond laser with either linear or circular polarization in a wide range of pulse energies. The relationships between the etch rates and pulse energies are obtained for different polarization states, which can be divided into three different regions. A drop of the etch rate for high pulse energy region is observed and the underlying mechanism is discussed. The advantage of using circularly polarized laser is justified owing to its unique capability of providing a 3D isotropic etch rate.

  16. Analysis of micro-structural relaxation phenomena in laser-modified fused silica using confocal Raman microscopy

    SciTech Connect

    Matthews, M; Vignes, R; Cooke, J; Yang, S; Stolken, J

    2009-12-15

    Fused silica micro-structural changes associated with localized 10.6 {micro}m CO{sub 2} laser heating are reported. Spatially-resolved shifts in the high-frequency asymmetric stretch transverse-optic (TO) phonon mode of SiO{sub 2} were measured using confocal Raman microscopy, allowing construction of axial fictive temperature (T{sub f}) maps for various laser heating conditions. A Fourier conduction-based finite element model was employed to compute on-axis temperature-time histories, and, in conjunction with a Tool-Narayanaswamy form for structural relaxation, used to fit T{sub f}(z) profiles to extract relaxation parameters. Good agreement between the calculated and measured T{sub f} was found, yielding reasonable values for relaxation time and activation enthalpy in the laser-modified silica.

  17. Formation of broadband antireflective and superhydrophilic subwavelength structures on fused silica using one-step self-masking reactive ion etching

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Jiang, Xiaodong; Huang, Jin; Geng, Feng; Sun, Laixi; Zu, Xiaotao; Wu, Weidong; Zheng, Wanguo

    2015-08-01

    Fused silica subwavelength structures (SWSs) with an average period of ~100 nm were fabricated using an efficient approach based on one-step self-masking reactive ion etching. The subwavelength structures exhibited excellent broadband antireflection properties from the ultraviolet to near-infrared wavelength range. These properties are attributable to the graded refractive index for the transition from air to the fused silica substrate that is produced by the ideal nanocone subwavelength structures. The transmittance in the 400-700 nm range increased from approximately 93% for the polished fused silica to greater than 99% for the subwavelength structure layer on fused silica. Achieving broadband antireflection in the visible and near-infrared wavelength range by appropriate matching of the SWS heights on the front and back sides of the fused silica is a novel strategy. The measured antireflection properties are consistent with the results of theoretical analysis using a finite-difference time-domain (FDTD) method. This method is also applicable to diffraction grating fabrication. Moreover, the surface of the subwavelength structures exhibits significant superhydrophilic properties.

  18. Formation of broadband antireflective and superhydrophilic subwavelength structures on fused silica using one-step self-masking reactive ion etching

    PubMed Central

    Ye, Xin; Jiang, Xiaodong; Huang, Jin; Geng, Feng; Sun, Laixi; Zu, Xiaotao; Wu, Weidong; Zheng, Wanguo

    2015-01-01

    Fused silica subwavelength structures (SWSs) with an average period of ~100 nm were fabricated using an efficient approach based on one-step self-masking reactive ion etching. The subwavelength structures exhibited excellent broadband antireflection properties from the ultraviolet to near-infrared wavelength range. These properties are attributable to the graded refractive index for the transition from air to the fused silica substrate that is produced by the ideal nanocone subwavelength structures. The transmittance in the 400–700 nm range increased from approximately 93% for the polished fused silica to greater than 99% for the subwavelength structure layer on fused silica. Achieving broadband antireflection in the visible and near-infrared wavelength range by appropriate matching of the SWS heights on the front and back sides of the fused silica is a novel strategy. The measured antireflection properties are consistent with the results of theoretical analysis using a finite-difference time-domain (FDTD) method. This method is also applicable to diffraction grating fabrication. Moreover, the surface of the subwavelength structures exhibits significant superhydrophilic properties. PMID:26268896

  19. 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.

  20. Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica

    SciTech Connect

    Adams, J J; Bolourchi, M; Bude, J D; Guss, G M; Matthews, M J; Nostrand, M C

    2010-10-26

    We present results from a study to determine an acceptable CO{sub 2} laser-based non-evaporative mitigation protocol for use on surface damage sites in fused-silica optics. A promising protocol is identified and evaluated on a set of surface damage sites created under ICF-type laser conditions. Mitigation protocol acceptability criteria for damage re-initiation and growth, downstream intensification, and residual stress are discussed. In previous work, we found that a power ramp at the end of the protocol effectively minimizes the residual stress (<25 MPa) left in the substrate. However, the biggest difficulty in determining an acceptable protocol was balancing between low re-initiation and problematic downstream intensification. Typical growing surface damage sites mitigated with a candidate CO{sub 2} laser-based mitigation protocol all survived 351 nm, 5 ns damage testing to fluences >12.5 J/cm{sup 2}. The downstream intensification arising from the mitigated sites is evaluated, and all but one of the sites has 100% passing downstream damage expectation values. We demonstrate, for the first time, a successful non-evaporative 10.6 {micro}m CO{sub 2} laser mitigation protocol applicable to fused-silica optics used on fusion-class lasers like the National Ignition Facility (NIF).

  1. 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.

  2. 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.

  3. Absorption of a single 500 fs laser pulse at the surface of fused silica: Energy balance and ablation efficiency

    SciTech Connect

    Varkentina, N.; Sanner, N.; Lebugle, M.; Sentis, M.; Utéza, O.

    2013-11-07

    Ablation of fused silica by a single femtosecond laser pulse of 500 fs pulse duration is investigated from the perspective of efficiency of incident photons to remove matter. We measure the reflected and transmitted fractions of the incident pulse energy as a function of fluence, allowing us to recover the evolution of absorption at the material surface. At the ablation threshold fluence, 25% of incident energy is absorbed. At high fluences, this ratio saturates around 70% due to the appearance of a self-triggered plasma mirror (or shielding) effect. By using the energy balance retrieved experimentally and measurements of the ablated volume, we show that the amount of absorbed energy is far above the bonding energy of fused silica at rest and also above the energy barrier to ablate the material under non-equilibrium thermodynamic conditions. Our results emphasize the crucial role of transient plasma properties during the laser pulse and suggest that the major part of the absorbed energy has been used to heat the plasma formed at the surface of the material. A fluence range yielding an efficient and high quality ablation is also defined, which makes the results relevant for femtosecond micromachining processes.

  4. Formation of carbon nanoclusters by implantation of keV carbon ions in fused silica followed by thermal annealing

    NASA Astrophysics Data System (ADS)

    Olivero, P.; Peng, J. L.; Liu, A.; Reichart, P.; McCallum, J. C.; Sze, J. Y.; Lau, S. P.; Tay, B. K.; Kalish, R.; Dhar, S.; Feldman, Leonard; Jamieson, David N.; Prawer, Steven

    2005-02-01

    In the last decade, the synthesis and characterization of nanometer sized carbon clusters have attracted growing interest within the scientific community. This is due to both scientific interest in the process of diamond nucleation and growth, and to the promising technological applications in nanoelectronics and quantum communications and computing. Our research group has demonstrated that MeV carbon ion implantation in fused silica followed by thermal annealing in the presence of hydrogen leads to the formation of nanocrystalline diamond, with cluster size ranging from 5 to 40 nm. In the present paper, we report the synthesis of carbon nanoclusters by the implantation into fused silica of keV carbon ions using the Plasma Immersion Ion Implantation (PIII) technique, followed by thermal annealing in forming gas (4% 2H in Ar). The present study is aimed at evaluating this implantation technique that has the advantage of allowing high fluence-rates on large substrates. The carbon nanostructures have been characterized with optical absorption and Raman spectroscopies, cross sectional Transmission Electron Microscopy (TEM), and Parallel Electron Energy Loss Spectroscopy (PEELS). Nuclear Reaction Analysis (NRA) has been employed to evaluate the deuterium incorporation during the annealing process, as a key mechanism to stabilize the formation of the clusters.

  5. Effect of annealing on the laser induced damage of polished and CO2 laser-processed fused silica surfaces

    NASA Astrophysics Data System (ADS)

    Doualle, T.; Gallais, L.; Cormont, P.; Donval, T.; Lamaignère, L.; Rullier, J. L.

    2016-06-01

    We investigate the effect of different heat treatments on the laser-induced damage probabilities of fused silica samples. Isothermal annealing in a furnace is applied, with different temperatures in the range 700-1100 °C and 12 h annealing time, to super-polished fused silica samples. The surface flatness and laser damage probabilities at 3 ns, 351 nm are measured before and after the different annealing procedures. We have found a significant improvement of the initial laser damage probabilities of the silica surface after annealing at 1050 °C for 12 h. A similar study has been conducted on CO2 laser-processed sites on the surface of the samples. Before and after annealing, we have studied the morphology of the sites, the evolution of residual stress, and the laser-induced damage threshold measured at 351 nm, 3 ns. In this case, we observe that the laser damage resistance of the laser created craters can reach the damage level of the bare fused silica surface after the annealing process, with a complete stress relieve. The obtained results are then compared to the case of local annealing process by CO2 laser irradiation during 1 s, and we found similar improvements in both cases. The different results obtained in the study are compared to numerical simulations made with a thermo-mechanical model based on finite-element method that allows the simulation of the isothermal or the local annealing process, the evolution of stress and fictive temperature. The simulation results were found to be very consistent with experimental observations for the stresses evolution after annealing and estimation of the heat affected area during laser-processing based on the density dependence with fictive temperature. Following this work, the temperature for local annealing should reach 1330-1470 °C for an optimized reduction of damage probability and be below the threshold for material removal, whereas furnace annealing should be kept below the annealing point to avoid sample

  6. Infrared, spectral, directional-hemispherical reflectance of fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating.

    PubMed

    Persky, Merle J; Szczesniak, Martin

    2008-04-01

    Infrared, spectral, directional-hemispherical reflectivity measurements of polished fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating are provided. The reflectance was measured with an estimated accuracy of 0.01 to 0.02 units and a precision of 0.005 units. All the surfaces were measured at ambient temperatures. Additionally, the chrome oxide ceramic particle surface was measured at 486 K and the Pyromark 2500 at four temperatures to 877 K. Polarization measurements are also provided for fused silica, Duraflect, chrome oxide ceramic particle surface, and Pyromark 2500 paint. Separate diffuse and specular reflectance components for the Duraflect and chrome oxide ceramic surfaces are included. Fresnel-based predictions for fused silica parallel and perpendicular polarized reflections are compared to measurements. It is notable that the Pyromark 2500 and chrome oxide ceramic particle surfaces exhibit a significant lack of manufacturing repeatability. PMID:18382562

  7. The Effect of HF/NH4F Etching on the Morphology of Surface Fractures on Fused Silica

    SciTech Connect

    Wong, L; Suratwala, T; Feit, M D; Miller, P E; Steele, R A

    2008-04-03

    The effects of HF/NH{sub 4}F, wet chemical etching on the morphology of individual surface fractures (indentations, scratches) and of an ensemble of surface fractures (ground surfaces) on fused silica glass has been characterized. For the individual surface fractures, a series of static or dynamic (sliding) Vickers and Brinnell indenters were used to create radial, lateral, Hertzian cone and trailing indentation fractures on a set of polished fused silica substrates which were subsequently etched. After short etch times, the visibility of both surface and subsurface cracks is significantly enhanced when observed by optical microscopy. This is attributed to the removal of the polishing-induced Bielby layer and the increased width of the cracks following etching allowing for greater optical scatter at the fracture interface. The removal of material during etching was found to be isotropic except in areas where the etchant has difficulty penetrating or in areas that exhibit significant plastic deformation/densification. Isolated fractures continue to etch, but will never be completely removed since the bottom and top of the crack both etch at the same rate. The etching behavior of ensembles of closely spaced cracks, such as those produced during grinding, has also been characterized. This was done using a second set of fused silica samples that were ground using either fixed or loose abrasives. The resulting samples were etched and both the etch rate and the morphology of the surfaces were monitored as a function of time. Etching results in the formation of a series of open cracks or cusps, each corresponding to the individual fractures originally on the surface of the substrate. During extended etching, the individual cusps coalesce with one another, providing a means of reducing the depth of subsurface damage and the peak-to-valley roughness. In addition, the material removal rate of the ground surfaces was found to scale with the surface area of the cracks as a

  8. Ad-hoc design of temporally shaped fs laser pulses based on plasma dynamics for deep ablation in fused silica

    NASA Astrophysics Data System (ADS)

    Hernandez-Rueda, J.; Siegel, J.; Puerto, D.; Galvan-Sosa, M.; Gawelda, W.; Solis, J.

    2013-07-01

    We have analyzed the ablation depth yield of fused silica irradiated with shaped pulse trains with a separation of 500 fs and increasing or decreasing intensity envelopes. This temporal separation value is extracted from previous studies on ablation dynamics upon irradiation with transform-limited 100 fs laser pulses. The use of decreasing intensity pulse trains leads to a strong increase of the induced ablation depth when compared to the behavior, at the same pulse fluence, of intensity increasing pulse trains. In addition, we have studied the material response under stretched (500 fs, FWHM) and transform-limited (100 fs, FWHM) pulses, for which avalanche or multiphoton ionization respectively dominates the carrier generation process. The comparison of the corresponding evolution of the ablated depth vs. fluence suggests that the use of pulse trains with decreasing intensity at high fluences should lead to enhanced single exposure ablation depths, beyond the limits corresponding to MPI- or AI-alone dominated processes.

  9. Transmittance and reflectance of crystalline quartz and highand low-water content fused silica from 2 microns to 1 mm

    NASA Technical Reports Server (NTRS)

    Heaney, J. B.; Stewart, K. P.; Hass, G.

    1983-01-01

    The transmittances and reflectances of cultured crystalline quartz, Suprasil, Suprasil W, and Infrasil were compared over the wavelength region from 2 to 1000 microns. The high-water content of Suprasil and the low-water content of cultured crystalline quartz, Suprasil W, and Infrasil were determined by their transmittances measured at 2.73 microns where water content causes high absorption in optical materials. The fact that the fused silicas, both with high- and low-water content, had identical far-IR transmittances and that their transmittances were greatly inferior to that of crystalline quartz led to the conclusion that their inferior transmittance is due to their amorphous structure and not to their water content.

  10. Optical diagnostics of the laser-induced phase transformations in thin germanium films on silicon, sapphire, and fused silica

    NASA Astrophysics Data System (ADS)

    Novikov, H. A.; Batalov, R. I.; Bayazitov, R. M.; Faizrakhmanov, I. A.; Ivlev, G. D.; Prokop'ev, S. L.

    2015-03-01

    The in-situ procedure is used to study the modification of thin (200-600 nm) germanium films induced by nanosecond pulses of a ruby laser. The films are produced using the ion-beam or magnetron sputtering on single-crystalline silicon (Si), sapphire (Al2O3), and fused silica (α-SiO2) substrates. The results on the dynamics of the laser-induced processes are obtained using the optical probing of the irradiated region at wavelengths of λ = 0.53 and 1.06 μm. The results of probing make it possible to determine the threshold laser energy densities that correspond to the Ge and Si melting and the generation of the Ge ablation plasma versus the amount of deposited Ge and thermophysical parameters of the substrate. The reflection oscillograms are used to obtain the dependences of the melt lifetime on the laser-pulse energy density.

  11. Deep wet etching of borosilicate glass and fused silica with dehydrated AZ4330 and a Cr/Au mask

    NASA Astrophysics Data System (ADS)

    Jin, Joo-Young; Yoo, Sunghyun; Bae, Jae-Sung; Kim, Yong-Kweon

    2014-01-01

    This research highlights a superior glass-wet-etch technique which enables a glass wafer to be etched for more than 20 h in 49 wt% hydrofluoric acid (HF) only with Cr/Au film and a common positive photoresist, AZ4330. We demonstrated that pits on the wet-etched glass wafer were generated not only due to HF diffusion through the Cr/Au film but also due to pinholes on the Cr/Au films created by the diffusion of the Cr/Au etchant through a photoresist etching-mask during the Cr/Au wet etching process. These two types of diffusion, HF diffusion and Cr/Au etchant diffusion, were eliminated by the thermal curing of a photoresist (PR), AZ4330, before the Cr/Au wet etching process. The curing process allowed the PR to dehydrate, increased the hydrophobicity, and prevented the diffusion of the hydrophilic HF and Cr/Au etchant. Optimization of the curing process was performed, showing that curing at 130 °C for 20 min was the proper condition. With the optimized process, a 525 µm thick borosilicate glass wafer was penetrated with 49%wt HF. A fused silica wafer 525 µm thick was also wet-etched and penetrated with 49 wt% HF at 10 h. Moreover, no pits were found in wet etching of the fused silica for 20 h in 49 wt% HF. These findings demonstrate that the proposed technique allows the wet etching of a glass wafer for more than 20 h in 49%wt HF, the best result thus far. We fabricated a glass substrate with a 217.0 µm deep cavity and a penetrating through-via using the proposed technique, proving the feasibility of the product as an optical component with a surface roughness of 45.5 Å in the cavity.

  12. PRECISION AND ACCURACY IN THE DETERMINATION OF ORGANICS IN WATER BY FUSED SILICA CAPILLARY COLUMN GAS CHROMOTOGRAPHY/MASS SPECTROMETRY AND PACKED COLUMN GAS CHROMATOGRAPHY/MASS SPECTROMETRY

    EPA Science Inventory

    Two general methods for the identification and measurement of organic compounds in water are compared. One method employs packed column chromatography and the other fused silica capillary column chromatography. The two gas chromatography/mass spectrometry (GC/MS) methods use diff...

  13. Identification of the formation phases of filamentary damage induced by nanosecond laser pulses in bulk fused silica

    SciTech Connect

    Shen, Chao; Xu, Zhongjie; Chambonneau, Maxime E-mail: jiangtian198611@163.com; Cheng, Xiang'ai; Jiang, Tian E-mail: jiangtian198611@163.com

    2015-09-14

    Employing a pump-probe polarization-based two-frame shadowgraphy setup, the formation of filamentary damage induced in bulk fused silica by a nanosecond pulse at 1064 nm is investigated with a picosecond probe. Three different phases are exhibited in the damage experiments. The first phase is the formation of a micrometric plasma channel along the laser direction during the beginning of the pulse likely caused by multi-photon ionization. This channel exhibits growth during ∼400 ps, and the newly grown plasma is discrete. Then, during the end of the pulse, this channel evolves into a tadpole-like morphology showing an elliptical head upstream the laser flux followed by a thin tail. This observed asymmetry is attributed to shielding effects caused by both the plasma and hot modified silica. Once the damage shows its almost final morphology, a last phase consists in the launch of a pressure wave enlarging it after the laser pulse. The physical mechanisms that might be involved in the formation of plasma channels are discussed. The experimental data are first confronted to the moving breakdown model which overestimates the filamentary damage length. Finally, taking into account the temporal shape of the laser pulses, the coupling between Kerr-induced self-focusing and stimulated Brillouin scattering is discussed to interpret the observations.

  14. Influence of vacuum on nanosecond laser-induced surface damage morphology in fused silica at 1064 nm

    NASA Astrophysics Data System (ADS)

    Diaz, R.; Chambonneau, M.; Grua, P.; Rullier, J.-L.; Natoli, J.-Y.; Lamaignère, L.

    2016-01-01

    The influence of vacuum on nanosecond laser-induced damage at the exit surface of fused silica components is investigated at 1064 nm. In the present study, as previously observed in air, ring patterns surrounding laser-induced damage sites are systematically observed on a plane surface when initiated by multiple longitudinal modes laser pulses. Compared to air, the printed pattern is clearly more concentrated. The obtained correlation between the damage morphology and the temporal structure of the pulses suggests a laser-driven ablation mechanism resulting in a thorough imprint of energy deposit. The ablation process is assumed to be subsequent to an activation of the surface by hot electrons related to the diffusive expansion of a plasma formed from silica. This interpretation is strongly reinforced with additional experiments performed on an optical grating in vacuum on which damage sites do not show any ring pattern. Qualitatively, in vacuum, the intensity-dependent ring appearance speed V ∝ I1/2 is shown to be different than in air where V ∝ I1/3. This demonstrates that the mechanisms of formation of ring patterns are different in vacuum than in air. Moreover, the mechanism responsible of the propagation of the activation front in vacuum is shown to be outdone when experiments are performed in air.

  15. Identification of the formation phases of filamentary damage induced by nanosecond laser pulses in bulk fused silica

    NASA Astrophysics Data System (ADS)

    Shen, Chao; Chambonneau, Maxime; Cheng, Xiang'ai; Xu, Zhongjie; Jiang, Tian

    2015-09-01

    Employing a pump-probe polarization-based two-frame shadowgraphy setup, the formation of filamentary damage induced in bulk fused silica by a nanosecond pulse at 1064 nm is investigated with a picosecond probe. Three different phases are exhibited in the damage experiments. The first phase is the formation of a micrometric plasma channel along the laser direction during the beginning of the pulse likely caused by multi-photon ionization. This channel exhibits growth during ˜400 ps, and the newly grown plasma is discrete. Then, during the end of the pulse, this channel evolves into a tadpole-like morphology showing an elliptical head upstream the laser flux followed by a thin tail. This observed asymmetry is attributed to shielding effects caused by both the plasma and hot modified silica. Once the damage shows its almost final morphology, a last phase consists in the launch of a pressure wave enlarging it after the laser pulse. The physical mechanisms that might be involved in the formation of plasma channels are discussed. The experimental data are first confronted to the moving breakdown model which overestimates the filamentary damage length. Finally, taking into account the temporal shape of the laser pulses, the coupling between Kerr-induced self-focusing and stimulated Brillouin scattering is discussed to interpret the observations.

  16. Thermo-mechanical simulations of CO2 laser-fused silica interactions

    NASA Astrophysics Data System (ADS)

    Doualle, T.; Gallais, L.; Cormont, P.; Hébert, D.; Combis, P.; Rullier, J.-L.

    2016-03-01

    CO2 laser heating of silica glass is used in many scientific and industrial applications. Particularly, localized CO2 laser heating of silica glass has demonstrated its ability to mitigate surface damage on optics used for high power laser applications. To develop such applications, the control of temperature, heat affected area, and resulting mechanical stresses are critical. Therefore, it is necessary to understand the silica transformation, the material ejection, and the thermo-mechanical stresses induced by the laser heating and subsequent cooling. In this paper, we detail the development of comprehensive thermo-mechanical numerical simulations of these physical processes, based on finite-element method. The approach is developed for 2D or 3D cases to tackle the case of a moving beam at the surface of the sample, and we particularly discuss the choice of the different parameters based on bibliographic inputs. The thermal and mechanical numerical results have been compared to different dedicated experimental studies: infrared thermography measurements at the surface of the irradiated area, optical profilometry measurements of the laser-processed sites, and photo-elastic measurements. Very consistent results are obtained between numerical and experimental results for the description of the temperature gradients, the material ejection, and the residual stresses.

  17. Picosecond-nanosecond bulk damage of fused silica at 1064nm

    NASA Astrophysics Data System (ADS)

    Smith, Arlee V.; Do, Binh T.

    2008-10-01

    We are interested in maximizing the performance of fiber lasers and amplifiers, particularly for amplification of ps-ns pulses. The observed pulse energies from large mode area fiber amplifiers routinely exceed the reported bulk damage threshold of silica. We have undertaken a program to establish the intrinsic damage thresholds of silica that are relevant for fiber applications. We use a single transverse / single longitudinal mode Q-switched Nd:YAG laser focused to an 8-µm spot several Rayleigh ranges deep in silica windows for the nanosecond measurement, and a Q-switched, mode locked Nd:YAG laser for the picoseconds measurements. Our key findings include: 1. The damage threshold is deterministic rather than statistical for both ns and ps pulses. The threshold varies less than 1% from location to location. 2. The intrinsic damage threshold of silica is 475+/-25 GW/cm2 (fluence = 3850 J/cm2) for 8 ns pulses and approximately 3 times higher for 14 ps pulses. 3. There is no difference in damage thresholds among Corning's A0, B1, C1, D1, D2, and D5 grades of silica. 4. A tight focus is required to avoid large self focusing corrections and to avoid SBS for the 8-ns pulses. 5. Damage morphologies are reproducible from pulse to pulse but change with focal spot size and pulse duration. In all cases, damage appears to begin exactly at the focus and then move upstream approximately one Rayleigh range. 6. The dependence of the damage threshold fluence on pulse duration is nearly linear for pulse durations longer than 50 ps. The square root of duration dependence reported by several investigators for the 50 ps to 10 ns range is refuted. 7. The variation of damage fluence with pulse duration from 20 fs to 20 ns and beyond is well described by a single electron avalanche rate equation with three fixed rates for the avalanche, multiphoton ionization, and electron recombination terms. 8. Our damage threshold is consistent with the most reliable DC field breakdown threshold. 9

  18. 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.

  19. Study of CO2 laser smoothing of surface roughness in fused silica

    SciTech Connect

    Shen, N; Matthews, J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D; Elhadj, S; Henshaw, D; Guss, G M; Guss, G M; Yang, T

    2009-11-03

    Small micrometer-sized roughness on optical surfaces, caused by laser damage and/or redeposition of laser ablated material, can cause local electric field intensification which may lead to damage initiation both on the optics and/or downstream. We examined the smoothing of etched periodic surface structures on SiO{sub 2} substrate with 10.6 {micro}m CO{sub 2} laser using atomic force microscopy. The characteristic surface tension driven mass flow of the glass under different laser parameters were simulated using computational fluid dynamics and correlated with experimental results. We found that during CO{sub 2} laser polishing the estimate viscosity of the silica glass appears to be higher than typical literature values measured at a temperature similar to the laser heating conditions. This discrepancy can be explained by the observation that at high temperature, a significant portion of the hydroxyl content in the layer of heated silica glass can diffuse out resulting in a much stiffer glass.

  20. Comparing the use of 4.6 um lasers versus 10.6 um lasers for mitigating damage site growth on fused silica surfaces

    SciTech Connect

    Yang, S T; Matthews, M J; Elhadj, S; Cooke, D; Guss, G M; Draggoo, V G; Wegner, P J

    2010-10-21

    The advantage of using mid-infrared (IR) 4.6 {micro}m lasers, versus far-infrared 10.6 {micro}m lasers, for mitigating damage growth on fused silica is investigated. In contrast to fused silica's high absorption at 10.6 {micro}m, silica absorption at 4.6 {micro}m is two orders of magnitude less. The much reduced absorption at 4.6 {micro}m enables deep heat penetration into fused silica when it is heated using the mid-IR laser, which in turn leads to more effective mitigation of damage sites with deep cracks. The advantage of using mid-IR versus far-IR laser for damage growth mitigation under non-evaporative condition is quantified by defining a figure of merit (FOM) that relates the crack healing depth to laser power required. Based on our FOM, we show that for damage cracks up to at least 500 {micro}m in depth, mitigation using a 4.6 {micro}m mid-IR laser is more efficient than mitigation using a 10.6 {micro}m far-IR laser.

  1. Effect of rogue particles on the sub-surface damage of fused silica during grinding/polishing

    SciTech Connect

    Suratwala, T I; Steele, R; Feit, M D; Wong, L; Miller, P E; Menapace, J A; Davis, P J

    2007-05-02

    The distribution and characteristics of surface cracks (i.e., sub-surface damage or scratching) on fused silica formed during grinding/polishing resulting from the addition of rogue particles in the base slurry has been investigated. Fused silica samples (10 cm diameter x 1 cm thick) were: (1) ground by loose abrasive grinding (alumina particles 9-30 {micro}m) on a glass lap with the addition of larger alumina particles at various concentrations with mean sizes ranging from 15-30 {micro}m, or (2) polished (using 0.5 {micro}m cerium oxide slurry) on various laps (polyurethanes pads or pitch) with the addition of larger rogue particles (diamond (4-45 {micro}m), pitch, dust, or dried Ceria slurry agglomerates) at various concentrations. For the resulting ground samples, the crack distributions of the as-prepared surfaces were determined using a polished taper technique. The crack depth was observed to: (1) increase at small concentrations (>10{sup -4} fraction) of rogue particles; and (2) increase with rogue particle concentration to crack depths consistent with that observed when grinding with particles the size of the rogue particles alone. For the polished samples, which were subsequently etched in HF:NH{sub 4}F to expose the surface damage, the resulting scratch properties (type, number density, width, and length) were characterized. The number density of scratches increased exponentially with the size of the rogue diamond at a fixed rogue diamond concentration suggesting that larger particles are more likely to lead to scratching. The length of the scratch was found to increase with rogue particle size, increase with lap viscosity, and decrease with applied load. At high diamond concentrations, the type of scratch transitioned from brittle to ductile and the length of the scratches dramatically increased and extended to the edge of the optic. The observed trends can explained semi-quantitatively in terms of the time needed for a rogue particle to penetrate into a

  2. Infrared thermometry and interferential microscopy for analysis of crater formation at the surface of fused silica under CO{sub 2} laser irradiation

    SciTech Connect

    Robin, Lucile; Cormont, Philippe; Hebert, David; Mainfray, Christelle; Rullier, Jean-Luc; Combis, Patrick; Gallais, Laurent

    2012-03-15

    In situ spatial and temporal temperature measurements of a fused silica surface heated by a 10.6 {mu}m CO{sub 2} laser were performed using an infrared camera. These measurements were derived from heat flux emission of the fused silica. High temperature measurements--in the range 400-2500 K--were performed at the surface of a semi-transparent media with a high spatial resolution. Particular attention was given to the experimental conception and to the calibration of the infrared device. Moreover, both conventional and interferential microscopes were used to characterize the silica surfaces after CO{sub 2} laser irradiation. By associating these results with thermal camera measurements we identified the major surface temperature levels of silica transformation when heated during 250 ms. Surface deformation of silica is observed for temperatures <2000 K. This is consistent with other recent work using CO{sub 2} laser heating. At higher temperatures, matter ejection, as deduced from microscope observations, occurs at temperatures that are still much lower than the standard boiling point. Such evaporation is described by a thermodynamical approach, and calculations show very good agreement with experiment.

  3. Time-Resolved Imaging of Material Response Following Laser-Induced Breakdown in the Bulk and Surface of Fused Silica

    SciTech Connect

    Raman, R N; Negres, R A; DeMange, P; Demos, S G

    2010-02-04

    Optical components within high energy laser systems are susceptible to laser-induced material modification when the breakdown threshold is exceeded or damage is initiated by pre-existing impurities or defects. These modifications are the result of exposure to extreme conditions involving the generation of high temperatures and pressures and occur on a volumetric scale of the order of a few cubic microns. The response of the material following localized energy deposition, including the timeline of events and the individual processes involved during this timeline, is still largely unknown. In this work, we investigate the events taking place during the entire timeline in both bulk and surface damage in fused silica using a set of time-resolved microscopy systems. These microscope systems offer up to 1 micron spatial resolution when imaging static or dynamic effects, allowing for imaging of the entire process with adequate temporal and spatial resolution. These systems incorporate various pump-probe geometries designed to optimize the sensitivity for detecting individual aspects of the process such as the propagation of shock waves, near-surface material motion, the speed of ejecta, and material transformations. The experimental results indicate that the material response can be separated into distinct phases, some terminating within a few tens of nanoseconds but some extending up to about 100 microseconds. Overall the results demonstrate that the final characteristics of the modified region depend on the material response to the energy deposition and not on the laser parameters.

  4. An Improved Method of Mitigating Laser Induced Surface Damage Growth in Fused Silica Using a Rastered, Pulsed CO2 Laser

    SciTech Connect

    Bass, I L; Guss, G M; Nostrand, M J; Wegner, P L

    2010-10-21

    A new method of mitigating (arresting) the growth of large (>200 m diameter and depth) laser induced surface damage on fused silica has been developed that successfully addresses several issues encountered with our previously-reported large site mitigation technique. As in the previous work, a tightly-focused 10.6 {micro}m CO{sub 2} laser spot is scanned over the damage site by galvanometer steering mirrors. In contrast to the previous work, the laser is pulsed instead of CW, with the pulse length and repetition frequency chosen to allow substantial cooling between pulses. This cooling has the important effect of reducing the heat-affected zone capable of supporting thermo-capillary flow from scale lengths on the order of the overall scan pattern to scale lengths on the order of the focused laser spot, thus preventing the formation of a raised rim around the final mitigation site and its consequent down-stream intensification. Other advantages of the new method include lower residual stresses, and improved damage threshold associated with reduced amounts of redeposited material. The raster patterns can be designed to produce specific shapes of the mitigation pit including cones and pyramids. Details of the new technique and its comparison with the previous technique will be presented.

  5. 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.

  6. Imaging System to Measure Kinetics of Material Cluster Ejection During Exit-Surface Damage Initiation and Growth in Fused Silica

    SciTech Connect

    Raman, R N; Negres, R A; Demos, S G

    2009-10-29

    Laser-induced damage on the surface of optical components typically is manifested by the formation of microscopic craters that can ultimately degrade the optics performance characteristics. It is believed that the damage process is the result of the material exposure to high temperatures and pressures within a volume on the order of several cubic microns located just below the surface. The response of the material following initial localized energy deposition by the laser pulse, including the timeline of events and the individual processes involved during this timeline, is still largely unknown. In this work we introduce a time-resolved microscope system designed to enable a detailed investigation of the sequence of dynamic events involved during surface damage. To best capture individual aspects of the damage timeline, this system is employed in multiple imaging configurations (such as multi-view image acquisition at a single time point and multi-image acquisition at different time points of the same event) and offers sensitivity to phenomena at very early delay times. The capabilities of this system are demonstrated with preliminary results from the study of exit-surface damage in fused silica. The time-resolved images provide information on the material response immediately following laser energy deposition, the processes later involved during crater formation or growth, the material ejecta kinetics, and overall material motion and transformation. Such results offer insight into the mechanisms governing damage initiation and growth in the optical components of ICF class laser systems.

  7. Morphology And Microstructure in Fused Silica Induced By High Fluence Ultraviolet 3omega (355 Nm) Laser Pulses

    SciTech Connect

    Wong, J.; Ferriera, J.L.; Lindsey, E.F.; Haupt, D.L.; Hutcheon, I.D.; Kinney, J.H.

    2007-08-08

    The morphology and microstructure induced in high quality fused silica by UV (355 nm) laser pulses at high fluence (10-45 J/cm{sup 2}) have been investigated using a suite of microscopic and spectroscopic tools. The laser beam has a near-Gaussian profile with a 1/e{sup 2} diameter of 0.98 mm at the sample plane and a pulse length FWHM (full width at half maximum) of 7.5 ns. The damage craters consist of a molten core region (thermal explosion), surrounded by a near concentric region of fractured material. The latter arises from propagation of lateral cracks induced by the laser-generated shock waves, which also compact the crater wall, {approx} 10 {micro}m thick and {approx} 20% higher in density. The size of the damage crater varies with laser fluence, number of pulses, and laser irradiation history. In the compaction layer, there is no detectable change in the Si/O stoichiometry to within {+-} 1.6% and no crystalline nano-particles of Si were observed. Micro- (1-10 {micro}m) and nano- (20-200 nm) cracks are found, however. A lower valence Si{sup 3+} species on the top 2-3 nm of the compaction layer is evident from the Si 2p XPS. The results are used to construct a physical model of the damage crater and to gain critical insight into laser damage process.

  8. Parametric study of the damage ring pattern in fused silica induced by multiple longitudinal modes laser pulses

    SciTech Connect

    Chambonneau, M. Grua, P.; Rullier, J.-L.; Lamaignère, L.; Natoli, J.-Y.

    2015-03-14

    With the use of multiple longitudinal modes nanosecond laser pulses at 1064 nm, laser damage sites at the exit surface of fused silica clearly and systematically exhibit ring patterns. It has been shown in our previous works that the apparent chronology of rings was closely related to the temporal shape of the laser pulses. This particular correspondence had suggested an explanation of the ring morphology formation based on the displacement of an ionization front in the surrounding air. To provide a former basis for this hypothesis and deeper understanding of ring pattern formation, additional experiments have been performed. First, the impact of fluence has been investigated, revealing that a wide variety of damage sites are produced within a very narrow fluence range; this fact involves the chronology of appearance of a surface plasma during the laser pulse. The sizes of the damage sites are proportional to the fluence of their expansion occurring between the beginning of the plasma and the end of the laser pulse. Second, specific experiments have been carried out at different angles of incidence, resulting in egg-shaped patterns rather than circular ones. This behavior can be explained by our previous hypothesis of creation of a plasma in air, its expansion being tightly conditioned by the illumination angle. This series of experiments, in which the angle of incidence is varied up to 80°, permits us to link quantitatively the working hypothesis of ionization front propagation with theoretical hydrodynamics modeling.

  9. Verifying an all fused silica miniature optical fiber tip pressure sensor performance with turbine engine field test

    NASA Astrophysics Data System (ADS)

    Wang, Xingwei; Xu, Juncheng; Zhu, Yizheng; Yu, Bing; Han, Ming; Wang, Zhuang; Cooper, Kristie L.; Pickrell, Gary R.; Wang, Anbo; Ringshia, Aditya; Ng, Wing

    2005-11-01

    Pressure sensors are the key elements for industrial monitoring and control systems to lower equipment maintenance cost, improve fuel economy, reduce atmospheric pollution, and provide a safer workplace. However, the testing environment is usually harsh. For example, inside the turbine engine, temperatures might exceed 600°C and pressures might exceed 100psi (690kPa), where most current available sensors cannot survive. Moreover, due to the restricted space for installation, miniature size of the sensor is highly desirable. To meet these requirements, a novel type of all fused silica optic fiber tip pressure sensor with a 125μm diameter was developed. It is a diaphragm based pressure sensor in which a Fabry-Perot interferometer is constructed by the end face of an optical fiber and the surface of a diaphragm connected by a short piece of hollow fiber. The FP cavity length and the interference pattern will change according to ambient pressure variation. Its main improvement with respect to previously developed optical sensors, such as those utilizing techniques of wet etching, anodic bonding and sol-gel bonding, is the fact that no chemical method is needed during the cavity fabrication. Its dynamic pressure performance was verified in a turbine engine field test, demonstrating not only that it can safely and reliably function near the fan of a turbine engine for more than two hours, but also that its performance is consistent with that of a commercial Kulite sensor.

  10. Laser-based dynamic evaporation and surface shaping of fused silica with assist gases: a path to rimless laser machining

    NASA Astrophysics Data System (ADS)

    Elhadj, S.; Matthews, M. J.; Guss, G. M.; Bass, I. L.

    2013-12-01

    Evaporation and ablation are fundamental processes which drive laser-material processing performance. In applications where surface shape is important, control of the temperature field and the resulting spatially varying material response must be considered. For that purpose, assist gases are useful in, first, lowering treatment temperatures and, second, in changing interfacial and bulk chemistry to limit capillary-driven flow. Additionally, laser-matter coupling is influenced by pulse length as it determines the heat affected zone. Using infrared imaging of CO2 laser-heated fused silica and surface profile measurements, we derive temperature and time dependent pitting rates along with shapes for a range of gases that include hydrogen, nitrogen, air, and helium. In the range of 1,500-4,500 K, evaporation, flow, and densification are shown to contribute to the pit shape. Analysis reveals a strong and complex dependence of rim formation on heating time and gas chemistry, mostly by lowering treatment temperature. Under dynamic heating, chemicapillarity appears to help in lowering rim height, in spite of the reactants mass transport limitations. Results on this gas-assisted approach suggest the possibility for sub-nanometer "rimless" laser-based machining.

  11. High-temperature measurement with Brillouin optical time domain analysis of an annealed fused-silica single-mode fiber.

    PubMed

    Bao, Yi; Chen, Genda

    2016-07-15

    The effect of annealing is experimentally studied for a fused silica, fully distributed fiber optic sensor based on the pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). Within a heating rate of 4.3°C/min and 30.6°C/min, and a sustained peak temperature for 120 and 240 min, annealing extended the sensor's upper operation temperature from 800°C to 1000°C and reduced the sensor's measurement variability over a temperature range of 22°C to 1000°C with a maximum Brillouin frequency variation of 1%. The annealed sensor had a linearly decreasing Brillouin frequency sensitivity from 1.349×10-3  GHz/°C at 22°C to 0.419×10-3  GHz/°C at 1000°C. The time required to achieve a stable annealing effect decayed exponentially with annealing temperature. PMID:27420489

  12. Rapid micromachining of high aspect ratio holes in fused silica glass by high repetition rate picosecond laser

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Abolghasemi, Ladan; Herman, Peter R.

    2014-01-01

    We present multiple methods of high aspect ratio hole drilling in fused silica glass, taking advantage of high power and high repetition rate picosecond lasers and flexible beam delivery methods to excise deep holes with minimal collateral damage. Combinations of static and synchronous scanning of laser focus were explored over a range of laser repetition rates and burst-train profiles that dramatically vary laser plume interaction dynamics, heat-affected zone, and heat accumulation physics. Chemically assisted etching of picosecond laser modification tracks are also presented as an extension from femtosecond laser writing of volume nanograting to form high aspect ratio (77) channels. Processing windows are identified for the various beam delivery methods that optimize the laser exposure over energy, wavelength, and repetition rate to reduce microcracking and deleterious heating effects. The results show the benefits of femtosecond laser interactions in glass extend into the picosecond domain, where the attributes of higher power further yield wide processing windows and significantly faster fabrication speed. High aspect ratio holes of 400 μm depth were formed over widely varying rates of 333 holes per second for mildly cracked holes in static-focal positioning through to one hole per second for low-damage and taper free holes in synchronous scanning.

  13. A Spectroscopic Comparison of Femtosecond Laser Modified Fused Silica using kHz and MHz Laser Systems.

    SciTech Connect

    Reichman, W J; Krol, D M; Shah, L; Yoshino, F; Arai, A; Eaton, S M; Herman, P R

    2005-09-29

    Waveguides were written in fused silica using both a femtosecond fiber laser with a 1 MHz pulse repetition rate and a femtosecond amplified Ti:sapphire laser with a 1 kHz repetition rate. Confocal Raman and fluorescence microscopy were used to study structural changes in the waveguides written with both systems. A broad fluorescence band, centered at 650 nm, associated with non-bridging oxygen hole center (NBOHC) defects was observed after waveguide fabrication with the MHz laser. With the kHz laser system these defects were only observed for pulse energies above 1 {mu}J. Far fewer NBOHC defects were formed with the MHz laser than with kHz writing, possibly due to thermal annealing driven by heat accumulation effects at 1 MHz. When the kHz laser was used with pulse energies below 1 {mu}J, the predominant fluorescence was centered at 550 nm, a band assigned to the presence of silicon clusters (E{prime}{sub {delta}}). We also observed an increase in the intensity of the 605 cm{sup -1} Raman peak relative to the total Raman intensity, corresponding to an increase in the concentration of 3-membered rings in the lines fabricated with both laser systems.

  14. 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.

  15. Residual stress and damage-induced critical fracture on CO2 laser treated fused silica

    SciTech Connect

    Matthews, M; Stolken, J; Vignes, R; Norton, M

    2009-11-02

    Localized damage repair and polishing of silica-based optics using mid- and far-IR CO{sub 2} lasers has been shown to be an effective method for increasing optical damage threshold in the UV. However, it is known that CO{sub 2} laser heating of silicate surfaces can lead to a level of residual stress capable of causing critical fracture either during or after laser treatment. Sufficient control of the surface temperature as a function of time and position is therefore required to limit this residual stress to an acceptable level to avoid critical fracture. In this work they present the results of 351 nm, 3 ns Gaussian damage growth experiments within regions of varying residual stress caused by prior CO{sub 2} laser exposures. Thermally stressed regions were non-destructively characterized using polarimetry and confocal Raman microscopy to measure the stress induced birefringence and fictive temperature respectively. For 1 {approx} 40s square pulse CO{sub 2} laser exposures created over 0.5-1.25 kW/cm{sup 2} with a 1-3 mm 1/e{sup 2} diameter beam (T{sub max} {approx} 1500-3000 K), the critical damage site size leading to fracture increases weakly with peak temperature, but shows a stronger dependence on cooling rate, as predicted by finite element hydrodynamics simulations. Confocal micro-Raman was used to probe structural changes to the glass over different thermal histories and indicated a maximum fictive temperature of 1900K for T{sub max} {ge} 2000 K. The effect of cooling rate on fictive temperature caused by CO{sub 2} laser heating are consistent with finite element calculations based on a Tool-Narayanaswamy relaxation model.

  16. Self-compression to 24 MW peak power in a fused silica solid-core fiber using a high-repetition rate thulium-based fiber laser system

    NASA Astrophysics Data System (ADS)

    Gebhardt, Martin; Gaida, Christian; Stutzki, Fabian; Hädrich, Steffen; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2016-03-01

    Complementing ultrafast thulium-doped fiber-laser systems with a subsequent nonlinear pulse compression stage can enable unique laser parameters at around 2 μm operation wavelength. Significant pulse shortening and peak power enhancement have been accomplished using a fused silica solid-core fiber. In this fiber a pulse peak power of 24 MW was achieved without catastrophic damage due to self-focusing. As compared to operation in the well-explored 1 μm wavelength region, increasing the emission wavelength to 2 μm has a twofold advantage for nonlinear compression in fused-silica solid-core fibers. This is because, on the one hand the self-focusing limit scales quadratically with the wavelength. On the other hand the dispersion properties of fused silica allow for self-compression of ultrashort pulses beyond 1.3 μm wavelength, which leads to strong spectral broadening from very compact setups without the need for external compression. Using this technique we have generated 1.1 μJpulses with 24 fs FWHM pulse duration (<4 optical cycles), 24 MW peak power and 24.6 W of average power. To the best of our knowledge, this is the highest average power obtained from any nonlinear compression experiment around 2 μm wavelength and the first demonstration of peak powers beyond 20 MW within a fused-silica solid-core fiber. This result emphasizes that thulium-doped fiber-based chirped-pulse amplification systems may outperform their ytterbiumdoped counterparts in terms of peak power due to the fourfold increase of the critical power of self-focusing.

  17. Centimeter-long microfluidic channel with an aspect ratio above 1,000 directly fabricated in fused silica by femtosecond laser micromachining

    NASA Astrophysics Data System (ADS)

    He, Fei; Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2010-02-01

    Femtosecond laser micromachining has emerged as a promising technique for creating three dimensional (3D) microstructures. As an essential building block for microfluidics, homogeneous microfluidic channel with high aspectratio is indispensable for lab-on-a-chip (LOC) applications. Fused silica is considered to be an excellent substrate material for LOC applications due to its low thermal expansion coefficient, low autofluorescence, and exceptional transmittance over a wide spectral range. Microfluidic channels can be directly fabricated inside fused silica by femtosecond laser direct writing followed by a subsequent wet chemical etching. However, the fabricated channels usually display a tapered feature and highly elliptical cross-section with limited length (usually <5 mm) and poor inner surface smoothness, which would hamper their applications. Herein, we demonstrate direct fabrication of homogeneous microfluidic channels embedded in fused silica by femtosecond laser direct writing, followed by wet chemical etching and glass drawing. With these procedures, the homogeneity of the fabricated channels has become excellent. Namely, the taper of the microchannels is greatly reduced while their cross-sectional shape becomes circular after the drawing. In addition, an inner surface smoothness of ~0.2 nm can be realized by this method. Finally, the glass drawing method can lead to centimeters long microfluidic channels with an aspect ratio as high as ~1,000. We expect that these microfluidic channels will have important applications in optofluidics in the future.

  18. Investigation of surface damage precursor evolutions and laser-induced damage threshold improvement mechanism during Ion beam etching of fused silica.

    PubMed

    Shi, Feng; Zhong, Yaoyu; Dai, Yifan; Peng, Xiaoqiang; Xu, Mingjin; Sui, Tingting

    2016-09-01

    Surface damage precursor evolution has great influence on laser-induced damage threshold improvement of fused silica surface during Ion beam etching. In this work, a series of ion sputtering experiment are carried out to obtain the evolutions of damage precursors (dot-form microstructures, Polishing-Induced Contamination, Hertz scratches, and roughness). Based on ion sputtering theory, surface damage precursor evolutions are analyzed. The results show that the dot-form microstructures will appear during ion beam etching. But as the ion beam etching depth goes up, the dot-form microstructures can be mitigated. And ion-beam etching can broaden and passivate the Hertz scratches without increasing roughness value. A super-smooth surface (0.238nm RMS) can be obtained finally. The relative content of Fe and Ce impurities both significantly reduce after ion beam etching. The laser-induced damage threshold of fused silica is improved by 34% after ion beam etching for 800nm. Research results can be a reference on using ion beam etching process technology to improve laser-induced damage threshold of fused silica optics. PMID:27607688

  19. Array of Chemically Etched Fused Silica Emitters for Improving the Sensitivity and Quantitation of Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Kelly, Ryan T.; Page, Jason S.; Tang, Keqi; Smith, Richard D.

    2007-06-01

    An array of emitters has been developed for increasing the sensitivity of electrospray ionization mass spectrometry (ESI-MS). The linear array consists of 19 chemically etched fused silica capillaries arranged with 500 µm (center-to-center) spacing. The multi-emitter device has a low dead volume to facilitate coupling to capillary liquid chromatography (LC) separations. The high aspect ratio of the emitters enables operation at flow rates as low as 20 nL/min/emitter, effectively extending the benefits of nanoelectrospray to higher flow rate analyses. To accommodate the larger ion current produced by the emitter array, a multi-capillary inlet to the mass spectrometer was also constructed. The inlet, which matched the dimensions of the emitter array, effectively preserved ion transmission efficiency. Standard reserpine solutions of varying concentration were electrosprayed at 1 µL/min using the multi-emitter/multi-inlet combination, and compared to a standard, single emitter configuration. A nine-fold sensitivity enhancement was observed for the multi-emitter relative to the single emitter. A bovine serum albumin tryptic digest was also analyzed and resulted in a sensitivity increase ranging from 2.4 to 12.3-fold for the detected tryptic peptides; the varying response was attributed to reduced ion suppression under the nano-ESI conditions afforded by the emitter array. An equimolar mixture of leucine enkephalin and maltopentaose was studied to verify that ion suppression is indeed reduced for the multi-ESI array relative to a single emitter over a range of flow rates.

  20. Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold.

    PubMed

    Nomura, Wataru; Kawazoe, Tadashi; Yatsui, Takashi; Naruse, Makoto; Ohtsu, Motoichi

    2014-01-01

    The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component's resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. Therefore, here we focused on the degradation in performance of an optical component caused by continuous irradiation with femtosecond laser light having a low energy density, i.e., laser-induced degradation. We performed an in situ observation and analysis of an increase in scattering light intensity in fused silica substrates. In experiments conducted using a pulsed laser with a wavelength of 800 nm, a pulse width of 160 fs and pulse repetition rate of 1 kHz, we found that the scattered light intensity increased starting from a specific accumulated fluence, namely, that the laser-induced degradation had a threshold. We evaluated the threshold fluence F t as 6.27 J/cm(2) and 9.21 J/cm(2) for the fused silica substrates with surface roughnesses of 0.20 nm and 0.13 nm in R a value, respectively, showing that the threshold decreased as the surface roughness increased. In addition, we found that the reflected light spectrum changed as degradation proceeded. We analyzed the details of the degradation by measuring instantaneous reflectance changes with a pump-probe method; we observed an increase in the generation probability of photogenerated carriers in a degraded silica substrate and a damaged silica substrate and observed a Raman signal originating from a specific molecular structure of silica. From these findings, we concluded that compositional changes in the molecular structure occurred during degradation due to femtosecond laser irradiation having an energy density below the LIDT. PMID:25247116

  1. The preparation of silver nanoparticle decorated silica nanowires on fused quartz as reusable versatile nanostructured surface-enhanced Raman scattering substrates.

    PubMed

    Hwang, Jih-Shang; Chen, Kuan-Yu; Hong, Shih-Jay; Chen, Shih-Wei; Syu, Wun-Shing; Kuo, Chi-Wen; Syu, Wei-Yi; Lin, Tai Yuan; Chiang, Hai-Pang; Chattopadhyay, Surojit; Chen, Kuei-Hsien; Chen, Li-Chyong

    2010-01-15

    We introduce a platform, comprised of silver nanoparticle decorated silica nanowires (SiONWs) dispersed on fused quartz substrates, for high sensitivity surface-enhanced Raman scattering (SERS) measurements using both frontal (through the analytes) and back-face (through the transparent substrate) excitation. Quasi-quantitative SERS performances on the specialized substrate, vis-à-vis a silver deposited bare fused quartz plate, showed: (i) the suitability of the Ag modified SiONW substrate for frontal as well as back-face excitation; (ii) a wider detection range with high sensitivity to Rhodamine 6G; and (iii) good underwater metal-oxide adhesion of the specialized substrates. Capable of surviving ultrasonic cleaning, the substrate introduced is one of the few reusable low-cost Ag-based nanostructured SERS substrates, requiring only a simple silver reload process (the silver mirror reaction). PMID:19955621

  2. Determination of Hydrogen Diffusion Coefficients in Fused Silica From 23 to 250°C Using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Shang, L.; Chou, I.; Lu, W.; Burruss, R. C.

    2008-12-01

    The oxygen buffer technique is routinely used in experimental studies of redox sensitive geochemical reactions at elevated pressures (P) and temperatures (T). However, this technique is limited to T above about 400°C due to the low permeability of sample containers (Pt or Ag-Pd alloys) to hydrogen at lower T. Preliminary results of Chou et al. (Geochim. Cosmochim. Acta, 2008, doi:10.1016/j.gca.2008.07.030) indicate that the use of fused silica capillary (FSC) container may extend this technique to lower T. In this study, hydrogen diffusion coefficients (D) in FSC were determined from 23 to 250°C by measuring the loss of hydrogen from the FSC containers (0.3 mm OD, 0.1 mm ID, and ~10 mm long) with Raman spectroscopy using CO2 as an internal standard. First, CO2 was loaded cryogenically in a FSC capsule (Chou et al., ibid.). The capsule was then inserted in a protective ceramic tube, sealed in a gold capsule containing Fe powder and water, and heated at 300°C under 100 MPa of Ar external P in a cold-seal pressure vessel for several days allowing H2 to diffuse into the capsule. After quench, the Raman spectra were collected and the initial relative concentration of hydrogen in the silica capsule was derived from the peak height ratios between H2 (near 587 cm-1) and CO2 (near 1387 cm- 1). The sample capsule was then heated at a fixed T at one atmosphere to let H2 diffuse out of the capsule, and the changes of hydrogen concentration were monitored by Raman spectroscopy after quench. This process was repeated with different heating durations at 23 (room T), 50, 102, 157, 200, and 250°C. The values of D (in cm2s-1) in FSC were obtained by fitting the observed changes of hydrogen concentration to an equation based on Fick's second law. Our results can be represented by: Ln D (±0.14) = (-39810/RT) - 9.5491 (r2 = 0.9985) where R is the gas constant, and T in Kelvin. The slope corresponds to an activation energy of 39.81 kJ/mol. Our D values are about a half order of

  3. Invisible two-dimensional barcode fabrication inside a synthetic fused silica by femtosecond laser processing using a computer-generated hologram

    NASA Astrophysics Data System (ADS)

    Kawashima, Hayato; Yamaji, Masahiro; Suzuki, Jun'ichi; Tanaka, Shuhei

    2011-03-01

    We report an invisible two-dimensional (2D) barcode embedded into a synthetic fused silica by femtosecond laser processing using a computer-generated hologram (CGH) that generates a spatially extended femtosecond pulse beam in the depth direction. When we illuminate the irradiated 2D barcode pattern with a 254 nm ultraviolet (UV) light, a strong red photoluminescence (PL) is observed, and we can read it by using a complementary metal oxide semiconductor (CMOS) camera and image processing technology. This work provides a novel barcode fabrication method by femtosecond laser processing using a CGH and a barcode reading method by a red PL.

  4. Fabrication and characterization of a silicon cantilever probe with an integrated quartz-glass (fused-silica) tip for scanning near-field optical microscopy.

    PubMed

    Schürmann, G; Noell, W; Staufer, U; de Rooij, N F; Eckert, R; Freyland, J M; Heinzelmann, H

    2001-10-01

    A cantilever-based probe is introduced for use in scanning near-field optical microscopy (SNOM) combined with scanning atomic-force microscopy (AFM). The probes consist of silicon cantilevers with integrated 25-mum-high fused-silica tips. The probes are batch fabricated by microfabrication technology. Transmission electron microscopy reveals that the transparent quartz tips are completely covered with an opaque aluminum layer before the SNOM measurement. Static and dynamic AFM imaging was performed. SNOM imaging in transmission mode of single fluorescent molecules shows an optical resolution better than 32 nm. PMID:18364783

  5. A simple and efficient frit preparation method for one-end tapered-fused silica-packed capillary columns in nano-LC-ESI MS.

    PubMed

    Tan, Feng; Chen, Shuo; Zhang, Yangjun; Cai, Yun; Qian, Xiaohong

    2010-04-01

    A novel frit preparation method for one-end tapered-fused silica-packed capillary columns in nano-LC-ESI MS was developed. A hollow-fused silica capillary column with a tapered tip as nano-spray emitter was filled with 5 microm C(18) beads, and then a sintered frit about 0.25 mm in length was prepared at the tip by butane flame. A stainless steel protection tube with 0.5 mm id was used to control the length of the frit and to protect the packed C(18) beads behind the sintered frit during the sintering. C(18) sintered frits were evaluated by BSA tryptic digests with nano-LC-LTQ. The sintered frits did not produce post-column band broadening due to very small volume (about 0.2 nL) and did not produce adsorption to sample. The sintered frit columns had good separation reproducibility and separation performance compared with self-assembled particles frit columns and commercial columns. PMID:20162556

  6. Experimental study of 351-nm and 527-nm laser-initiated surface damage on fused silica surfaces due to typical contaminants

    SciTech Connect

    Honig, J; Norton, M A; Hollingsworth, W G; Donohue, E E; Johnson, M A

    2004-11-08

    Optics damage under high-intensity illumination may be the direct result of laser light interaction with a contaminant on the surface. Contaminants of interest are small particles of the materials of construction of large laser systems and include aluminum, various absorbing glasses, and fused silica. In addition, once a damage site occurs and begins to grow, the ejecta from the growing damage site create contamination on nearby optic surfaces and may initiate damage on these surfaces via a process we call ''fratricide.'' We report on a number of experiments that we have performed on fused silica optics that were deliberately contaminated with materials of interest. The experiments were done using 527-nm light as well as 351-nm light. We have found that many of the contaminant particles are removed by the interaction with the laser and the likelihood of removal and/or damage is a function of both fluence and contaminant size. We have developed an empirical model for damage initiation in the presence of contaminants.

  7. Comparison of three modifications of fused-silica capillaries and untreated capillaries for protein profiling of maize extracts by capillary electrophoresis.

    PubMed

    Pobozy, Ewa; Sentkowska, Aleksandra; Piskor, Anna

    2014-09-01

    In this work, capillary electrophoresis was applied to protein profiling of fractionated extracts of maize. A comparative study on the application of uncoated fused-silica capillaries and capillaries modified with hydroxypropylmethylcellulose, ω-iodoalkylammonium salt and a commercially available neutral capillary covalently coated with polyacrylamide is presented. The coating stability, background electrolyte composition, and separation efficiency were investigated. It was found that for zeins separation, the most stable and efficient was the capillary coated with polyacrylamide. Finally, the usefulness of these methods was studied for the differentiation of zein fraction in transgenic and nontransgenic maize. Zeins extracted from maize standards containing 0 and 5% m/m genetic modification were successfully separated, but slight differences were observed in terms of the zein content. Albumin and globulin fractions were analyzed with the use of unmodified fused-silica capillary with borate buffer pH 9 and the capillary coated with polyacrylamide with phosphate buffer pH 3. In the albumin fraction, additional peaks were found in genetically modified samples. PMID:24931305

  8. The effect of pulse duration on the growth rate of laser-induced damage sites at 351 nm on fused silica surfaces

    SciTech Connect

    Negres, R A; Norton, M A; Liao, Z M; Cross, D A; Bude, J D; Carr, C W

    2009-10-29

    Past work in the area of laser-induced damage growth has shown growth rates to be primarily dependent on the laser fluence and wavelength. More recent studies suggest that growth rate, similar to the damage initiation process, is affected by a number of additional parameters including pulse duration, pulse shape, site size, and internal structure. In this study, we focus on the effect of pulse duration on the growth rate of laser damage sites located on the exit surface of fused silica optics. Our results demonstrate, for the first time, a significant dependence of growth rate at 351 nm on pulse duration from 1 ns to 15 ns as {tau}{sup 0.3} for sites in the 50-100 {micro}m size range.

  9. Parallel generation of nanochannels in fused silica with a single femtosecond laser pulse: Exploiting the optical near fields of triangular nanoparticles

    SciTech Connect

    Hubenthal, F.; Morarescu, R.; Englert, L.; Haag, L.; Baumert, T.; Traeger, F.

    2009-08-10

    We present experiments to prepare highly ordered nanochannels with subdiffraction dimensions on fused silica surfaces with femtosecond laser light. For this purpose, we exploit the strongly enhanced near field of highly ordered triangular gold nanoparticles. We demonstrate that after a single laser shot, 6 {mu}m long nanochannels with a mean depth of 4 nm and an average width of 96 nm, i.e., well below the diffraction limit, are generated. These nanochannels are prepared by ablation, caused by the localization of the near field. The crucial parameters, besides the applied fluence, are the polarization direction of the incoming laser light with respect to the triangular nanoparticles and the size of the nanoparticles.

  10. EVALUATION OF FUSED-SILICA CAPILLARY COLUMNS FOR GC/ECD (GAS CHROMATOGRAPHY WITH ELECTRON CAPTURE DETECTION) ANALYSIS OF CHLORINATED HYDROCARBONS LISTED IN EPA (ENVIRONMENTAL PROTECTION AGENCY) METHOD 8120 (JOURNAL VERSION)

    EPA Science Inventory

    Four mega-bore, one wide-bore, and one narrow-bore fused-silica capillary columns were evaluated for their applicability to the GC/ECD analysis of 22 chlorinated hydrocarbons, some of which are currently targeted by EPA Method 8120. No one column can resolve all 22 compounds. Fou...

  11. Temperature-dependent strain and temperature sensitivities of fused silica single mode fiber sensors with pulse pre-pump Brillouin optical time domain analysis

    NASA Astrophysics Data System (ADS)

    Bao, Yi; Chen, Genda

    2016-06-01

    This paper reports a distributed temperature and strain sensor based on pulse pre-pump Brillouin optical time domain analysis. An uncoated, telecom-grade fused silica single-mode fiber as a distributed sensor was calibrated for its sensitivity coefficients under various strains and temperatures up to 800 °C. The Brillouin frequency of fiber samples changed nonlinearly with temperature and linearly with strain. The temperature sensitivity decreased from 1.113 to 0.830 MHz /°C in the range of 22–800 °C. The strain sensitivity was reduced from 0.054 to 0.042 MHz /με as the temperature increased from 22 to 700 °C and became unstable at higher temperatures due to creep effect. The strain measurement range was reduced from 19 100 to 6000 με in the temperature range of 22–800 °C due to fused silica’s degradation. The calibrated fiber optic sensor demonstrated adequate accuracy and precision for strain and temperature measurements and stable performance in heating–cooling cycles. It was validated in an application setting.

  12. Implantation of plasmonic nanoparticles in SiO2 by pulsed laser irradiation of gold films on SiOx-coated fused silica and subsequent thermal annealing

    NASA Astrophysics Data System (ADS)

    Stolzenburg, H.; Peretzki, P.; Wang, N.; Seibt, M.; Ihlemann, J.

    2016-06-01

    The pulsed UV-laser irradiation of thin noble metal films deposited on glass substrates leads to the incorporation of metal particles in the glass, if a sufficiently high laser fluence is applied. This process is called laser implantation. For the implantation of gold into pure fused silica, high laser fluences (∼1 J/cm2 at 193 nm laser wavelength) are required. Using a SiOx (x ≈ 1) coated SiO2-substrate, the implantation of gold into this coating can be accomplished at significantly lower fluences starting from 0.2 J/cm2 (comparable to those used for standard glass). Particles with diameters in the range of 10-60 nm are implanted to a depth of about 40 nm as identified by transmission electron microscopy. An additional high temperature annealing step in air leads to the oxidation of SiOx to SiO2, without influencing the depth distribution of particles significantly. Only superficial, weakly bound particles are released and can be wiped away. Absorption spectra show a characteristic plasmon resonance peak at 540 nm. Thus, pure silica glass (SiO2) with near surface incorporated plasmonic particles can be fabricated with this method. Such material systems may be useful for example as robust substrates for surface enhanced Raman spectroscopy (SERS).

  13. Extracting the distribution of laser damage precursors on fused silica surfaces for 351 nm, 3 ns laser pulses at high fluences (20-150 J/cm2).

    PubMed

    Laurence, Ted A; Bude, Jeff D; Ly, Sonny; Shen, Nan; Feit, Michael D

    2012-05-01

    Surface laser damage limits the lifetime of optics for systems guiding high fluence pulses, particularly damage in silica optics used for inertial confinement fusion-class lasers (nanosecond-scale high energy pulses at 355 nm/3.5 eV). The density of damage precursors at low fluence has been measured using large beams (1-3 cm); higher fluences cannot be measured easily since the high density of resulting damage initiation sites results in clustering. We developed automated experiments and analysis that allow us to damage test thousands of sites with small beams (10-30 µm), and automatically image the test sites to determine if laser damage occurred. We developed an analysis method that provides a rigorous connection between these small beam damage test results of damage probability versus laser pulse energy and the large beam damage results of damage precursor densities versus fluence. We find that for uncoated and coated fused silica samples, the distribution of precursors nearly flattens at very high fluences, up to 150 J/cm2, providing important constraints on the physical distribution and nature of these precursors. PMID:22565775

  14. Cryogenic surface distortion and hysteresis of a 50 cm diameter fused silica mirror cooled to 77 K

    NASA Technical Reports Server (NTRS)

    Young, Jeffrey A.; Howard, Steven D.; Augason, Gordon C.; Melugin, Ramsey K.

    1990-01-01

    A 50 cm diameter, lightweight, Amersil TO8E, fused-natural-quartz mirror with a single arch cross section was tested at the NASA/Ames Research Center Cryogenic Optics Test Facility to measure cryogenic distortion and hysteresis. The mirror was cooled to 77 K in four serial tests and the mirror figure was measured with a phase-measuring interferometer. On the basis of the repeatability of room temperature and cryogenic optical measurements, it was determined that the Single Arch Mirror had no measurable hysteresis and displayed repeatable cryogenic distortion. The Cryogenic Optics Test Facility, optical and thermal test methods, test results, and measurement accuracy are described.

  15. Final report: Interamerican Metrology System (SIM) Regional Metrology Organization (RMO) capacitance comparison. SIM.EM-K4.1, 10 pF fused-silica standard capacitor at 1000 Hz and SIM.EM-S4.1, 100 pF fused-silica standard capacitor at 1000 Hz

    NASA Astrophysics Data System (ADS)

    Sanchez, H.; Castro, B. I.; Koffman, A. D.; Zhang, N. F.; Wang, Y.; Shields, S.

    2015-01-01

    Two bilateral capacitance comparisons between the National Institute of Standards and Technology (NIST) and the Instituto Costarricense de Electricidad (ICE) were carried out to demonstrate the significant improvements achieved in capacitance metrology by ICE. These comparisons were a follow-up to the 2006 SIM.EM-K4, -S3, and -S4 capacitance comparisons. These bilateral activities consist of capacitance comparison SIM.EM-K4.1, comparing a 10 pF fused-silica standard at 1000 Hz, and comparison SIM.EM-S4.1, comparing a 100 pF fused-silica standard at 1000 Hz. The result of these bilateral comparisons have provided improved degrees of equivalence between ICE and the participants of the SIM.EM-K4, -S3, and -S4 capacitance comparisons. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  16. Absorption cross sections of surface-adsorbed H2O in the 295-370 nm region and heterogeneous nucleation of H2O on fused silica surfaces.

    PubMed

    Du, Juan; Huang, Li; Zhu, Lei

    2013-09-12

    We have determined absorption cross sections of a monolayer of H2O adsorbed on the fused silica surfaces in the 295-370 nm region at 293 ± 1 K by using Brewster angle cavity ring-down spectroscopy. Absorption cross sections of surface-adsorbed H2O vary between (4.66 ± 0.83) × 10(-20) and (1.73 ± 0.52) × 10(-21) cm(2)/molecule over this wavelength range, where errors quoted represent experimental scatter (1σ). Our experimental study provides direct evidence that surface-adsorbed H2O is an absorber of the near UV solar radiation. We also varied the H2O pressure in the surface study cell over the 0.01-17 Torr range and obtained probe laser absorptions at 295, 340, and 350 nm by multilayer of adsorbed H2O molecules until the heterogeneous nucleation of water occurred on fused silica surfaces. The average absorption cross sections of multilayer adsorbed H2O are (2.17 ± 0.53) × 10(-20), (2.48 ± 0.67) × 10(-21), and (2.34 ± 0.59) × 10(-21) cm(2)/molecule at 295, 340, and 350 nm. The average absorption cross sections of transitional H2O layer are (6.06 ± 2.73) × 10(-20), (6.48 ± 3.85) × 10(-21), and (8.04 ± 4.92) × 10(-21) cm(2)/molecule at 295, 340, and 350 nm. The average thin water film absorption cross sections are (2.39 ± 0.50) × 10(-19), (3.21 ± 0.81) × 10(-20), and (3.37 ± 0.94) × 10(-20) cm(2)/molecule at 295 nm, 340 nm, and 350 nm. Atmospheric implications of the results are discussed. PMID:23947798

  17. Overcritical plasma ignition and diagnostics from oncoming interaction of two color low energy tightly focused femtosecond laser pulses inside fused silica

    NASA Astrophysics Data System (ADS)

    Potemkin, F. V.; Bravy, B. G.; Bezsudnova, Yu I.; Mareev, E. I.; Starostin, V. M.; Platonenko, V. T.; Gordienko, V. M.

    2016-04-01

    We report overcritical (3.3  ×  1021 cm-3) microplasma produced by low energy colliding IR (infrared) (1.24 μm) and visible (0.62 μm) femtosecond pulses tightly focused (NA  =  0.5) into the bulk of fused silica with on-line monitoring based on third harmonic generated by the IR beam. It was established that the absorbed energy density is the key parameter that determines the micromodification formation threshold and in our experimental conditions it is close to 4.5 kJ cm-3. Non-monotonic behavior of the third harmonic signal as a function of time delay between visible (0.62 μm) and IR (1.24 μm) femtosecond pulses demonstrates the qualitative differences about the two phenomena: one is the seed electrons generation by the visible pulse via multiphoton ionization and second is the avalanche ionization by the IR pulse. We predict that the tandem two-color excitation of wide-bandgap dielectric in comparison with single-color pulse interaction regime allows providing a much higher absorbed energy density and overcritical plasma.

  18. Optical Evaluation of Digital Micromirror Devices (DMDs) with UV-Grade Fused Silica, Sapphire, and Magnesium Fluoride Windows and Longterm Reflectance of Bare Devices

    NASA Technical Reports Server (NTRS)

    Quijada, Manuel A.; Travinsky, Anton; Vorobiev, Dmitry; Ninkov, Zoran; Raisanen, Alan; Robberto, Massimo; Heap, Sara

    2016-01-01

    Digital micromirror devices (DMDs) are commercial micro-electromechanical systems, consisting of millions of mirrors which can be individually addressed and tilted into one of two states (+/-12deg). These devices were developed to create binary patterns in video projectors, in the visible range. Commercially available DMDs are hermetically sealed and extremely reliable. Recently, DMDs have been identified as an alternative to microshutter arrays for space-based multi-object spectrometers (MOS). Specifically, the MOS at the heart of the proposed Galactic Evolution Spectroscopic Explorer (GESE) uses the DMD as a reprogrammable slit mask. Unfortunately, the protective borosilicate windows limit the use of DMDs in the UV and IR regimes, where the glass has insufficient throughput. In this work, we present our efforts to replace standard DMD windows with custom windows made from UV-grade fused silica, low-absorption optical sapphire (LAOS) and magnesium fluoride (MgF2). We present transmission measurements of the antireflection coated windows and the reflectance of bare (window removed) DMDs. Furthermore, we investigated the long-term stability of the DMD reflectance and experiments for coating DMD active area with a layer of pure aluminum (Al) to boost reflectance performance in the UV spectral range (200-400 nm).

  19. High-Speed Photographic Study of Wave Propagation and Impact Damage in Fused Silica and AlON Using the Edge-On Impact (EOI) Method

    NASA Astrophysics Data System (ADS)

    Strassburger, E.; Patel, P.; McCauley, J. W.; Templeton, D. W.

    2006-07-01

    An Edge-on Impact (EOI) technique, developed at the Ernst-Mach-Institute (EMI), coupled with a Cranz-Schardin high-speed camera, has been successfully utilized to visualize dynamic fracture in many brittle materials. In a typical test, the projectile strikes one edge of a specimen and damage formation and fracture propagation is recorded during the first 20 μs after impact. In the present study, stress waves and damage propagation in fused silica and AlON were examined by means of two modified Edge-on Impact arrangements. In one arrangement, fracture propagation was observed simultaneously in side and top views of the specimens by means of two Cranz-Schardin cameras. In another arrangement, the photographic technique was modified by placing the specimen between crossed polarizers and using the photo-elastic effect to visualize the stress waves. Pairs of impact tests at approximately equivalent velocities were carried out in transmitted plane (shadowgraphs) and crossed polarized light.

  20. High-Speed Photographic Study of Wave Propagation and Impact Damage in Fused Silica and AlON Using the Edge-On Impact (EOI) Method

    SciTech Connect

    Strassburger, E.; Patel, P.; McCauley, J. W.; Templeton, D. W.

    2006-07-28

    An Edge-on Impact (EOI) technique, developed at the Ernst-Mach-Institute (EMI), coupled with a Cranz-Schardin high-speed camera, has been successfully utilized to visualize dynamic fracture in many brittle materials. In a typical test, the projectile strikes one edge of a specimen and damage formation and fracture propagation is recorded during the first 20 {mu}s after impact. In the present study, stress waves and damage propagation in fused silica and AlON were examined by means of two modified Edge-on Impact arrangements. In one arrangement, fracture propagation was observed simultaneously in side and top views of the specimens by means of two Cranz-Schardin cameras. In another arrangement, the photographic technique was modified by placing the specimen between crossed polarizers and using the photo-elastic effect to visualize the stress waves. Pairs of impact tests at approximately equivalent velocities were carried out in transmitted plane (shadowgraphs) and crossed polarized light.

  1. High-speed Photographic Study of Wave Propagation and Impact Damage in Fused Silica and AlON Using the Edge-on Impact (EOI) Method

    NASA Astrophysics Data System (ADS)

    Patel, Parimal; Strassburger, Elmar; Templeton, Douglas

    2005-07-01

    An Edge-on Impact (EOI) test method coupled with a high speed Cranz-Schardin camera has been developed at the Fraunhofer-Institute for High-Speed Dynamics, Ernst-Mach-Institut (EMI), Efringen-Kirchen, Germany to visualize damage propagation and dynamic fracture in structural ceramics. Most work in the past has been carried out in a reflection mode from the surface of impacted ceramics. In the current study, the test was reconfigured to photograph the propagation of damage in the transmission mode using shadowgraphs. In addition to plain light observations, the stress wave was also visualized in crossed polarizers using the photoelastic effect. Plates of fused silica measuring 100X100X13mm were impacted at velocities from 151 to 350 m/s. Plates of AlON measuring 100X100X10mm were impacted using solid cylinder steel projectiles with velocities ranging from 270 to 925 m/s. Detailed analysis of the macroscopic fracture patterns, stress wave characteristics and velocity, various damage zones structures, single crack and crack front velocities will be presented.

  2. Change in transmittance of fused silica as a means of detecting material sputtered from components on a 5-cm ion thruster

    NASA Technical Reports Server (NTRS)

    Weigand, A. J.; Mirtich, M. J.

    1972-01-01

    Two endurance tests of a 5-cm mercury bombardment thruster are reported. Both tests used a translational screen-grid system with the beam vectored 10 degrees. The first test lasted 141 hours and the second test operated for 2026 hours. In each test two fused silica samples (solar cell covers), 2.0 cm by 2.1 cm, were placed in shielded holders to detect materials sputtered from the thruster. Spectral optical properties between 0.398 and 2.16 microns were measured on each sample, both before and after the endurance tests. The deposition on each sample was spectrographically analyzed to determine the type of materials sputtered from the thruster. It was found that sputtering from the neutralizer is highly dependent on its position with respect to the beam edge. The sputtering from the accelerator grid of the translational screen-grid system of the 2026 hour test was sufficient to form an opaque film on the sample located in the direction opposite to the vectored beam.

  3. Fiber-based solid phase microextraction using fused silica lined bottles to collect, store, and stabilize a multianalyte headspace gas sample for offline analyses.

    PubMed

    Harvey, Chris A; Carter, J Chance; Ertel, John R; Alviso, Cindy T; Chinn, Sarah C; Maxwell, Robert S

    2015-07-01

    We have developed a solid phase microextraction (SPME) sampling method using fused silica lined bottles (400 ml) to collect, store, and stabilize a headspace subsample from the source for subsequent offline, repetitive analyses of the gas using fiber-based SPME. The method enables long-term stability for repeated offline analysis of the organic species collected from the source headspace and retains all the advantages of fiber SPME sampling (e.g. rapid extraction, solvent free, simple and inexpensive) while providing additional advantages. Typically, the analytes collected on the SPME fiber must be desorbed and analyzed immediately to mitigate analyte loss or contamination. The new SPME sampling method, conducted offline using carboxen/polydimethylsiloxane (carboxen/PDMS - 85 μm) coated fibers, has been shown to be identical to in situ SPME sampling of a headspace acquired from an 80 component organic matrix with reproducibility demonstrated to be less than %RSD=7.0% for replicate samples measured over a 30-day period. In addition, repetitive samplings from one headspace aliquot are possible using one or more fibers and fiber types as well as quantitative options such as internal standard addition as demonstrated in a feasibility study using a benzene/toluene/xylene (BTX; 1 ppmv) certified gas standard, in which the SPME measurement precision (%RSD) was improved by a factor of 1.5-1.9 compared to the use of an external standard. PMID:26008594

  4. Raman spectroscopic measurements of CO2 density: Experimental calibration with high-pressure optical cell (HPOC) and fused silica capillary capsule (FSCC) with application to fluid inclusion observations

    USGS Publications Warehouse

    Wang, X.; Chou, I.-Ming; Hu, W.; Burruss, R.C.; Sun, Q.; Song, Y.

    2011-01-01

    Raman spectroscopy is a powerful method for the determination of CO2 densities in fluid inclusions, especially for those with small size and/or low fluid density. The relationship between CO2 Fermi diad split (??, cm-1) and CO2 density (??, g/cm3) has been documented by several previous studies. However, significant discrepancies exist among these studies mainly because of inconsistent calibration procedures and lack of measurements for CO2 fluids having densities between 0.21 and 0.75g/cm3, where liquid and vapor phases coexist near room temperature.In this study, a high-pressure optical cell and fused silica capillary capsules were used to prepare pure CO2 samples with densities between 0.0472 and 1.0060g/cm3. The measured CO2 Fermi diad splits were calibrated with two well established Raman bands of benzonitrile at 1192.6 and 1598.9cm-1. The relationship between the CO2 Fermi diad split and density can be represented by: ??=47513.64243-1374.824414????+13.25586152????2-0.04258891551????3 (r2=0.99835, ??=0.0253g/cm3), and this relationship was tested by synthetic fluid inclusions and natural CO2-rich fluid inclusions. The effects of temperature and the presence of H2O and CH4 on this relationship were also examined. ?? 2011 Elsevier Ltd.

  5. Time-resolved imaging of filamentary damage on the exit surface of fused silica induced by 1064 nm nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Chao, Shen; Xiang'ai, Cheng; Tian, Jiang; Zhiwu, Zhu; Yifan, Dai

    2015-04-01

    Laser-induced damage on the exit surface of fused silica with a filament was observed. The filament has a central hollow core surrounded by molten materials and no obvious cracks could be observed. The critical intensity for the transition from pure surface damage (SD) to filamentary damage (FD) was measured. Time-resolved shadowgraphic microscopy with nanosecond time resolution was employed to compare the propagation of shock wave and material response in the SD and FD process. The main different features during the material response process include: (i) thermoelastic shock waves launched in FD were multiple and a column envelope was observed in the lateral direction; (ii) more energy is deposited in the bulk for FD resulting to a lower speed of shock wave in air; (iii) the overall time for establishing the main character of the damage site for FD was shorter because of the absence of crack expansion. Self-focusing and temperature-activated optical absorption enhancement of the bulk material are discussed to explain the morphology difference between SD and FD and the evolution of filament length under different incident intensities.

  6. FY07 LDRD Final Report A Fracture Mechanics and Tribology Approach to Understanding Subsurface Damage on Fused Silica during Grinding and Polishing

    SciTech Connect

    Suratwala, T I; Miller, P E; Menapace, J A; Wong, L L; Steele, R A; Feit, M D; Davis, P J; Walmer, C D

    2008-02-05

    The objective of this work is to develop a solid scientific understanding of the creation and characteristics of surface fractures formed during the grinding and polishing of brittle materials, specifically glass. In this study, we have experimentally characterized the morphology, number density, and depth distribution of various surface cracks as a function of various grinding and polishing processes (blanchard, fixed abrasive grinding, loose abrasive, pitch polishing and pad polishing). Also, the effects of load, abrasive particle (size, distribution, foreign particles, geometry, velocity), and lap material (pitch, pad) were examined. The resulting data were evaluated in terms of indentation fracture mechanics and tribological interactions (science of interacting surfaces) leading to several models to explain crack distribution behavior of ground surfaces and to explain the characteristics of scratches formed during polishing. This project has greatly advanced the scientific knowledge of microscopic mechanical damage occurring during grinding and polishing and has been of general interest. This knowledge-base has also enabled the design and optimization of surface finishing processes to create optical surfaces with far superior laser damage resistance. There are five major areas of scientific progress as a result of this LDRD. They are listed in Figure 1 and described briefly in this summary below. The details of this work are summarized through a number of published manuscripts which are included this LDRD Final Report. In the first area of grinding, we developed a technique to quantitatively and statistically measure the depth distribution of surface fractures (i.e., subsurface damage) in fused silica as function of various grinding processes using mixtures of various abrasive particles size distributions. The observed crack distributions were explained using a model that extended known, single brittle indentation models to an ensemble of loaded, sliding

  7. Optical and structural properties of polycrystalline CVD diamond films grown on fused silica optical fibres pre-treated by high-power sonication seeding

    NASA Astrophysics Data System (ADS)

    Bogdanowicz, R.; Śmietana, M.; Gnyba, M.; Gołunski, Ł.; Ryl, J.; Gardas, M.

    2014-09-01

    In this paper, the growth of polycrystalline chemical vapour deposition (CVD) diamond thin films on fused silica optical fibres has been investigated. The research results show that the effective substrate seeding process can lower defect nucleation, and it simultaneously increases surface encapsulation. However, the growth process on glass requires high seeding density. The effects of suspension type and ultrasonic power were the specific objects of investigation. In order to increase the diamond density, glass substrates were seeded using a high-power sonication process. The highest applied power of sonotrode reached 72 W during the performed experiments. The two, most common diamond seeding suspensions were used, i.e. detonation nanodiamond dispersed in (a) dimethyl sulfoxide and (b) deionised water. The CVD diamond nucleation and growth processes were performed using microwave plasma assisted chemical vapour deposition system. Next, the seeding efficiency was determined and compared using the numerical analysis of scanning electron microscopy images. The molecular composition of nucleated diamond was examined with micro-Raman spectroscopy. The sp3/sp2 band ratio was calculated using Raman spectra deconvolution method. Thickness, roughness, and optical properties of the nanodiamond films in UV-vis wavelength range were investigated by means of spectroscopic ellipsometry. It has been demonstrated that the high-power sonication process can improve the seeding efficiency on glass substrates. However, it can also cause significant erosion defects at the fibre surface. We believe that the proposed growth method can be effectively applied to manufacture the novel optical fibre sensors. Due to high chemical and mechanical resistance of CVD diamond films, deposition of such films on the sensors is highly desirable. This method enables omitting the deposition of an additional adhesion interlayer at the glass-nanocrystalline interface, and thus potentially increases

  8. Laser damage by ns and sub-ps pulses on hafnia/silica anti-reflection coatings on fused silica double-sided polished using zirconia or ceria and washed with or without an alumina wash step.

    SciTech Connect

    Bellum, John Curtis; Rambo, Patrick K.; Schwarz, Jens; Kletecka, Damon; Atherton, Briggs W.; Kimmel, Mark W.; Smith, Ian Craig; Smith, Douglas; Hobbs, Zachary

    2010-10-01

    Sandia's Large Optics Coating Operation has extensive results of laser induced damage threshold (LIDT) testing of its anti-reflection (AR) and high reflection coatings on substrates pitch polished using ceria and washed in a process that includes an alumina wash step. The purpose of the alumina wash step is to remove residual polishing compound to minimize its role in laser damage. These LIDT tests are for multi longitudinal mode, ns class pulses at 1064 nm and 532 nm (NIF-MEL protocol) and mode locked, sub-ps class pulses at 1054 nm (Sandia measurements), and show reasonably high and adequate laser damage resistance for coatings in the beam trains of Sandia's Z-Backlighter terawatt and petawatt lasers. An AR coating in addition to coatings of our previous reports confirms this with LIDTs of 33.0 J/cm{sup 2} for 3.5 ns pulses and 1.8 J/cm{sup 2} for 350 fs pulses. In this paper, we investigate both ceria and zirconia in doublesided polishing (common for large flat Z-Backlighter laser optics) as they affect LIDTs of an AR coating on fused silica substrates washed with or without the alumina wash step. For these AR coated, double-sided polished surfaces, ceria polishing in general affords better resistance to laser damage than zirconia polishing and laser damage is less likely with the alumina wash step than without it. This is supported by specific results of laser damage tests with 3.5 ns, multi longitudinal mode, single shot pulses at 1064 nm and 532 nm, with 7.0 ns, single and multi longitudinal mode, single and multi shot pulses at 532 nm, and with 350 fs, mode-locked, single shot pulses at 1054 nm.

  9. FUSE - Australia

    ERIC Educational Resources Information Center

    South Australian Science Teachers Journal, 1974

    1974-01-01

    Announces the establishment of a division of FUSE in Australia, at Sturt College of Advanced Education, for the purpose of disseminating the concept of unified science and to facilitate the development of unified science programs. (BR)

  10. Fabrication of Efficient, Large Aperture Transmission Diffraction Gratings by Ion-Beam Etching

    SciTech Connect

    Nguyen, H T; Bryan, S R; Britten, J A; Perry, M D

    2000-09-14

    The utilization of high-power short pulse laser employing chirped-pulse amplification (CPA) for material processing and inertial confinement research is widely increasing. The performance of these high-power CPA laser system continues to be limited by the ability of the pulse compression gratings to hold up to the high-average-power or high-peak-power of the laser. Pulse compression gratings used in transmission and fabricated out of bulk fused silica have intrinsically the highest laser damage threshold when compared with metal or multilayer dielectric gratings that work in reflection. LLNL has developed processing capability to produce high efficiency fused silica transmission gratings at sizes useful to future Petawatt-class systems, and has demonstrated high efficiency at smaller aperture. This report shows that fused silica diffraction exhibiting >95% efficiency into the -1 diffraction order in transmission (90{sup o} deflection of the incident light, at an incidence angle of 45{sup o} to the grating face). The microstructure of this grating consisted of grooves ion-beam etched to a depth of 1.6 microns with a pitch of 0.75 microns, using a holographically produced photoresist mask that was subsequently stripped away in significance to the fabrication of the small scale high efficiency grating was the development of the processing technology and infrastructure for production of such gratings at up to 65 cm diameter. LLNL is the currently the only location in the world with the ability to coat, interferometrically expose, and ion etch diffractive optics at this aperture. Below, we describe the design, fabrication, performance and, the scaleup process for a producing a high-efficiency transmission grating on a 65 cm fused silica substrate.

  11. Temporally focused femtosecond laser pulses for low numerical aperture micromachining through optically transparent materials

    PubMed Central

    Vitek, Dawn N.; Adams, Daniel E.; Johnson, Adrea; Tsai, Philbert S.; Backus, Sterling; Durfee, Charles G.; Kleinfeld, David; Squier, Jeffrey A.

    2010-01-01

    Temporal focusing of spatially chirped femtosecond laser pulses overcomes previous limitations for ablating high aspect ratio features with low numerical aperture (NA) beams. Simultaneous spatial and temporal focusing reduces nonlinear interactions, such as self-focusing, prior to the focal plane so that deep (~1 mm) features with parallel sidewalls are ablated at high material removal rates (25 µm3 per 80 µJ pulse) at 0.04-0.05 NA. This technique is applied to the fabrication of microfluidic devices by ablation through the back surface of thick (6 mm) fused silica substrates. It is also used to ablate bone under aqueous immersion to produce craniotomies. PMID:20721196

  12. Guard For Fuse Caps

    NASA Technical Reports Server (NTRS)

    Atwell, D. C.

    1985-01-01

    L-shaped guard attached to fuse holder. Guard prevents casual tampering with fuses in electrical junction box or fuse block. Protects fuses from being damaged by handling or by rope or string used to secure them. With fuse-cap guard, only responsible people have access to fuses.

  13. Boron doped Si rich oxide/SiO2 and silicon rich nitride/SiNx bilayers on molybdenum-fused silica substrates for vertically structured Si quantum dot solar cells

    NASA Astrophysics Data System (ADS)

    Lin, Ziyun; Wu, Lingfeng; Jia, Xuguang; Zhang, Tian; Puthen-Veettil, Binesh; Yang, Terry Chien-Jen; Conibeer, Gavin; Perez-Wurfl, Ivan

    2015-07-01

    Vertically structured Si quantum dots (QDs) solar cells with molybdenum (Mo) interlayer on quartz substrates would overcome current crowding effects found in mesa-structured cells. This study investigates the compatibility between boron (B) doped Si QDs bilayers and Mo-fused silica substrate. Both Si/SiO2 and Si/SiNx based QDs bilayers were studied. The material compatibility under high temperature treatment was assessed by examining Si crystallinity, microstress, thin film adhesion, and Mo oxidation. It was observed that the presence of Mo interlayer enhanced the Si QDs size confinement, crystalline fraction, and QDs size uniformity. The use of B doping was preferred compared to phosphine (PH3) doping studied previously in terms of better surface and interface properties by reducing oxidized spots on the film. Though crack formation due to thermal mismatch after annealing remained, methods to overcome this problem were proposed in this paper. Schematic diagram to fabricate full vertical structured Si QDs solar cells was also suggested.

  14. Boron doped Si rich oxide/SiO{sub 2} and silicon rich nitride/SiN{sub x} bilayers on molybdenum-fused silica substrates for vertically structured Si quantum dot solar cells

    SciTech Connect

    Lin, Ziyun Wu, Lingfeng; Jia, Xuguang; Zhang, Tian; Puthen-Veettil, Binesh; Yang, Terry Chien-Jen; Conibeer, Gavin; Perez-Wurfl, Ivan

    2015-07-28

    Vertically structured Si quantum dots (QDs) solar cells with molybdenum (Mo) interlayer on quartz substrates would overcome current crowding effects found in mesa-structured cells. This study investigates the compatibility between boron (B) doped Si QDs bilayers and Mo-fused silica substrate. Both Si/SiO{sub 2} and Si/SiN{sub x} based QDs bilayers were studied. The material compatibility under high temperature treatment was assessed by examining Si crystallinity, microstress, thin film adhesion, and Mo oxidation. It was observed that the presence of Mo interlayer enhanced the Si QDs size confinement, crystalline fraction, and QDs size uniformity. The use of B doping was preferred compared to phosphine (PH{sub 3}) doping studied previously in terms of better surface and interface properties by reducing oxidized spots on the film. Though crack formation due to thermal mismatch after annealing remained, methods to overcome this problem were proposed in this paper. Schematic diagram to fabricate full vertical structured Si QDs solar cells was also suggested.

  15. Single-pulse laser ablation threshold of borosilicate, fused silica, sapphire, and soda-lime glass for pulse widths of 500  fs, 10  ps, 20  ns.

    PubMed

    Nieto, Daniel; Arines, Justo; O'Connor, Gerard M; Flores-Arias, María Teresa

    2015-10-10

    In this work, we report a comparative study of the laser ablation threshold of borosilicate, fused silica, sapphire, and soda-lime glass as a function of the pulse width and for IR laser wavelengths. We determine the ablation threshold for three different pulse durations: τ=500  fs, 10 ps, and 20 ns. Experiments have been performed using a single laser pulse per shot in an ambient (air) environment. The results show a significant difference, of two orders of magnitude, between the group of ablation thresholds obtained for femtosecond, picosecond, and nanosecond pulses. This difference is reduced to 1 order of magnitude in the soda-lime substrate with tin impurities, pointing out the importance of the incubation effect. The morphology of the marks generated over the different glass materials by one single pulse of different pulse durations has been analyzed using a scanning electron microscope (FESEM ULTRA Plus). Our results are important for practical purposes, providing the ablation threshold data of four commonly used substrates at three different pulse durations in the infrared regime (1030-1064 nm) and complete data for increasing the understanding of the differences in the mechanism's leading ablation in the nanosecond, picosecond, and femtosecond regimes. PMID:26479792

  16. Fused silica fine grinding with low roughness

    NASA Astrophysics Data System (ADS)

    Dai, Lei; Gu, Yongqiang; Wu, Di

    2014-08-01

    Lithography-optics is one of the most complex optical systems. The fine grinding process is the most important step before polishing. Roughness and sub-surface damage (SSD) are essential outputs of fine grinding. We demonstrate the method that use fix abrasive cup tool with CNC grinding machine to complete the fine grinding process, even instead of lapping process. And experiment sample roughness can reach 23.40nm rms and Ra 18.554nm. The SSD estimate is about 2 μm which is also smaller than commercial lapping process. The fine grinding output can satisfy the lithography optic fabrication demands and efficiently reduce the polishing time.

  17. The Advanced Virgo monolithic fused silica suspension

    NASA Astrophysics Data System (ADS)

    Aisa, D.; Aisa, S.; Campeggi, C.; Colombini, M.; Conte, A.; Farnesini, L.; Majorana, E.; Mezzani, F.; Montani, M.; Naticchioni, L.; Perciballi, M.; Piergiovanni, F.; Piluso, A.; Puppo, P.; Rapagnani, P.; Travasso, F.; Vicerè, A.; Vocca, H.

    2016-07-01

    The detection of gravitational waves is one of the most challenging prospects faced by experimental physicists. Suspension thermal noise is an important noise source at operating frequencies between approximately 10 and 30 Hz, and represents a limit to the sensitivity of the ground based interferometric gravitational wave detectors. Its effects can be reduced by minimizing the losses and by optimizing the geometry of the suspension fiber as well as its attachment system. In this proceeding we will describe the mirrors double stage monolithic suspension system to be used in the Advanced Virgo (AdV) detector. We also present the results of the thermal noise study, performed with the help of a finite elements model, taking into account the precise geometry of the fibers attachment systems on the suspension elements. We shall demonstrate the suitability of this suspension for installation in AdV.

  18. Self-healing fuse

    NASA Technical Reports Server (NTRS)

    Jones, N. D.; Kinsinger, R. E.; Harris, L. P.

    1974-01-01

    Fast-acting current limiting device provides current overload protection for vulnerable circuit elements and then re-establishes conduction path within milliseconds. Fuse can also perform as fast-acting switch to clear transient circuit overloads. Fuse takes advantage of large increase in electrical resistivity that occurs when liquid metal vaporizes.

  19. Aperture lamp

    DOEpatents

    MacLennan, Donald A.; Turner, Brian P.

    2003-01-01

    A discharge lamp includes means for containing a light emitting fill, the fill being capable of absorbing light at one wavelength and re-emitting the light at a different wavelength, the light emitted from the fill having a first spectral power distribution in the absence of reflection of light back into the fill; means for exciting the fill to cause the fill to emit light; and means for reflecting some of the light emitted by the fill back into the fill while allowing some light to exit, the exiting light having a second spectral power distribution with proportionately more light in the visible region as compared to the first spectral power distribution, wherein the light re-emitted by the fill is shifted in wavelength with respect to the absorbed light and the magnitude of the shift is in relation to an effective optical path length. Another discharge lamp includes an envelope; a fill which emits light when excited disposed in the envelope; a source of excitation power coupled to the fill to excite the fill and cause the fill to emit light; and a reflective ceramic structure disposed around the envelope and defining an light emitting opening, wherein the structure comprises a sintered body built up directly on the envelope and made from a combination of alumina and silica.

  20. The COronal Solar Magnetism Observatory (COSMO) Large Aperture Coronagraph

    NASA Astrophysics Data System (ADS)

    Tomczyk, Steve; Gallagher, Dennis; Wu, Zhen; Zhang, Haiying; Nelson, Pete; Burkepile, Joan; Kolinksi, Don; Sutherland, Lee

    2013-04-01

    The COSMO is a facility dedicated to observing coronal and chromospheric magnetic fields. It will be located on a mountaintop in the Hawaiian Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will provide unique observations of the global coronal magnetic fields and its environment to enhance the value of data collected by other observatories on the ground (e.g. SOLIS, BBO NST, Gregor, ATST, EST, Chinese Giant Solar Telescope, NLST, FASR) and in space (e.g. SDO, Hinode, SOHO, GOES, STEREO, Solar-C, Solar Probe+, Solar Orbiter). COSMO will employ a fleet of instruments to cover many aspects of measuring magnetic fields in the solar atmosphere. The dynamics and energy flow in the corona are dominated by magnetic fields. To understand the formation of CMEs, their relation to other forms of solar activity, and their progression out into the solar wind requires measurements of coronal magnetic fields. The large aperture coronagraph, the Chromospheric and Prominence Magnetometer and the K-Coronagraph form the COSMO instrument suite to measure magnetic fields and the polarization brightness of the low corona used to infer electron density. The large aperture coronagraph will employ a 1.5 meter fuse silica singlet lens, birefringent filters, and a spectropolarimeter to cover fields of view of up to 1 degree. It will observe the corona over a wide range of emission lines from 530.3 nm through 1083.0 nm allowing for magnetic field measurements over a wide range of coronal temperatures (e.g. FeXIV at 530.3 nm, Fe X at 637.4 nm, Fe XIII at 1074.7 and 1079.8 nm. These lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the large aperture coronagraph to a preliminary design review state by the end of 2013. As with all data from Mauna Loa, the data products from COSMO will be available to the community via the Mauna Loa website: http://mlso.hao.ucar.edu

  1. The FUSE Approach

    ERIC Educational Resources Information Center

    Showalter, Victor M.

    1973-01-01

    A description of the present position of the FUSE organization relative to the development of unified science programs is discussed, including the related purposes and directions that characterize the newly established center. (DF)

  2. Sealed silica pressure ampoules for crystal growth

    NASA Technical Reports Server (NTRS)

    Holland, L. R.

    1984-01-01

    The properties of vitreous silica and the mechanics of thick walled pressure vessels are reviewed with regard to the construction of sealed silica crucibles such as are used in the growth of mercury-cadmium telluride crystals. Data from destructive rupture tests are reported, failure modes discussed, and recommendations for design given. Ordinary commercial clear vitreous silica from flame fused quartz can withstand a surface stress of 20 MPa or more in this application.

  3. Tropone-fused carbaporphyrins.

    PubMed

    Lash, Timothy D; Gilot, Gean C; AbuSalim, Deyaa I

    2014-10-17

    Previous attempts to prepare tropone-fused carbaporphyrins by reacting peroxides with azuliporphyrins under basic conditions afforded benzocarbaporphyrins instead. In this study, a methoxyazulitripyrrane condensed with a pyrrole dialdehyde in the presence of TFA, followed by oxidation with ferric chloride, to give a tropone-fused carbaporphyrin following a spontaneous demethylation. The porphyrinoid gave a modified UV-vis spectrum showing multiple bands in the Soret region, and the proton NMR spectrum showed that it has a reduced diamagnetic ring current in comparison to other carbaporphyrins. The tropone-fused derivative failed to react with tert-butyl hydroperoxide and potassium hydroxide, demonstrating that this type of structure is not an intermediate in the formation of benzocarbaporphyrins. However, the reaction with silver(I) acetate gave the corresponding silver(III) complex. Condensation of the methoxyazulitripyrrane with 2,5-thiophenedicarbaldehyde gave a related tropone-fused thiacarbaporphyrin together with a methoxythiaazuliporphyrin. Treatment of the carbaporphyrins with DBU resulted in the formation of anionic species, while addition of acid afforded dicationic structures. DFT studies were performed on a series of tautomers, protonated species, and anionic structures related to these tropone-fused carbaporphyrins, and NICS calculations were carried out. These results allowed favorable conjugation pathways to be identified. In addition, these studies predicted that protonation initially occurs on the carbonyl moiety rather than on the expected interior pyrrolenine nitrogen atom. PMID:25229306

  4. Self-healing fuse development

    NASA Technical Reports Server (NTRS)

    Jones, N. D.; Kinsinger, R. E.; Harris, L. P.

    1973-01-01

    The mercury-filled self-healing fuses developed for this program afford very good protection from circuit faults with rapid reclosure. Fuse performance and design parameters have been characterized. Life tests indicate a capability of 500 fuse operations. Fuse ratings are 150 v at 5, 15, 25 and 50 circuit A. A series of sample fuses using alumina and beryllia insulation have been furnished to NASA for circuit evaluation.

  5. Triphenylsilane-fused Porphyrins.

    PubMed

    Kato, Kenichi; Kim, Jun Oh; Yorimitsu, Hideki; Kim, Dongho; Osuka, Atsuhiro

    2016-06-01

    A reaction sequence of 2-(diphenylsilyl)phenylation by Negishi coupling and intramolecular sila-Friedel-Crafts reaction has been explored for the synthesis of mono-triphenylsilane-fused porphyrins 5 M and 6 M (M= Ni, Zn) and bis-triphenylsilane-fused porphyrins 7 M and 8 Ni. A triply linked triphenylsilane-fused Ni(II) porphyrin, 13 Ni, was synthesized in a stepwise manner involving the above reaction sequence and a final Pd-catalyzed C-H activating arylative cyclization. The silicon atom in 13 Ni takes a distorted planarized structure with an almost perpendicular Si-phenyl group, causing an electronic effect due to effective σ*-π* interaction. PMID:27124659

  6. High purity silica reflecting heat shield development

    NASA Technical Reports Server (NTRS)

    Congdon, W.

    1974-01-01

    A reflecting heat shield composed of fused silica in which the scattering results from the refractive index mismatch between silica particles and the voids introduced during the fabrication process is developed. Major considerations and conclusions of the development are: the best material to use is Type A, which is capable of ultra-high-purity and which does not show the 0.243 micrometer absorption band; the reflection efficiency of fused silica is decreased at higher temperatures due to the bathochromic shift of the ultraviolet cut-off; for a given silica material, over the wavelength region and particle sizes tested, the monodisperse particle size configurations produce higher reflectances than continuous particle size configurations; and the smaller monodisperse particle size configurations give higher reflectance than the larger ones. A reflecting silica configuration that is an efficient reflector of shock layer radiation at high ablation temperatures is achieved by tailoring the matrix for optimum scattering and using an ultra-high-purity material.

  7. OLED panel with fuses

    DOEpatents

    Levermore, Levermore; Pang, Huiqing; Rajan, Kamala

    2014-09-16

    Embodiments may provide a first device that may comprise a substrate, a plurality of conductive bus lines disposed over the substrate, and a plurality of OLED circuit elements disposed on the substrate, where each of the OLED circuit elements comprises one and only one pixel electrically connected in series with a fuse. Each pixel may further comprise a first electrode, a second electrode, and an organic electroluminescent (EL) material disposed between the first and the second electrodes. The fuse of each of the plurality of OLED circuit elements may electrically connect each of the OLED circuit elements to at least one of the plurality of bus lines. Each of the plurality of bus lines may be electrically connected to a plurality of OLED circuit elements that are commonly addressable and at least two of the bus lines may be separately addressable.

  8. Debuncher Momentum Aperture Measurements

    SciTech Connect

    O'Day, S.

    1991-01-01

    During the November 1990 through January 1991 {bar p} studies period, the momentum aperture of the beam in the debuncher ring was measured. The momentum aperture ({Delta}p/p) was found to be 4.7%. The momentum spread was also measured with beam bunch rotation off. A nearly constant particle population density was observed for particles with {Delta}p/p of less than 4.3%, indicating virtually unobstructed orbits in this region. The population of particles with momenta outside this aperture was found to decrease rapidly. An absolute or 'cut-off' momentum aperture of {Delta}p/p = 5.50% was measured.

  9. Method for fusing bone

    DOEpatents

    Mourant, Judith R.; Anderson, Gerhard D.; Bigio, Irving J.; Johnson, Tamara M.

    1996-01-01

    Method for fusing bone. The present invention is a method for joining hard tissue which includes chemically removing the mineral matrix from a thin layer of the surfaces to be joined, placing the two bones together, and heating the joint using electromagnetic radiation. The goal of the method is not to produce a full-strength weld of, for example, a cortical bone of the tibia, but rather to produce a weld of sufficient strength to hold the bone halves in registration while either external fixative devices are applied to stabilize the bone segments, or normal healing processes restore full strength to the tibia.

  10. Variable-aperture screen

    DOEpatents

    Savage, George M.

    1991-01-01

    Apparatus for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function.

  11. Rotating Aperture System

    DOEpatents

    Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

    2005-01-18

    A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

  12. Analytical model for CO(2) laser ablation of fused quartz.

    PubMed

    Nowak, Krzysztof M; Baker, Howard J; Hall, Denis R

    2015-10-10

    This paper reports the development of an analytical model, with supporting experimental data, which quite accurately describes the key features of CO2 laser ablation of fused silica glass. The quantitative model of nonexplosive, evaporative material removal is shown to match the experimental data very well, to the extent that it can be used as a tool for ablative measurements of absorption coefficient and vaporization energy. The experimental results indicated that a minimum of 12  MJ kg-1 is required to fully vaporize fused quartz initially held at room temperature, which is in good agreement with the prediction of the model supplied with input data available in the literature. An optimal window for the machining of fused quartz was revealed in terms of pulse duration 20-80 μs and CO2 laser wavelength optimized for maximum absorption coefficient. Material removal rates of 0.33 μm per J cm-2 allow for a high-precision depth control with modest laser stability. The model may also be used as a parameter selection guide for CO2 laser ablation of fused silica or other materials of similar thermophysical properties. PMID:26479800

  13. Fused fiber micro-knots.

    PubMed

    Shahal, Shir; Klein, Avi; Masri, Gilad; Fridman, Moti

    2016-06-10

    We present fusing of a fiber micro-knot by a CO2 laser beam. We demonstrate tuning of the coupling strength and tuning of the spectral resonance of the micro-knot by the fusing process. The experimental results reveal that fusing the fiber micro-knots increases the coupling efficiency and improves the robustness and the stability of the micro-knots. PMID:27409009

  14. FUSE Observations of K--M Stars

    NASA Astrophysics Data System (ADS)

    Ake, T. B.; Dupree, A. K.; Linsky, J. L.; Harper, G. M.; Young, P. R.

    2000-12-01

    As part of the FUSE PI program, a representative sample of cool stars is being surveyed in the LWRS (30 x 30 arcsec) aperture. We report on recent observations of three late-type stars, AU Mic (HD 197481, M0 Ve), β Gem (HD 62509, K0 IIIb), and α Ori (HD 39801, M1-2 Ia--Iab). AU Mic and β Gem show strong emission lines of O VI 1032/1037 and C III 977/1176 and weaker lines of C II, N II, N III, S IV, Si III, Si IV, and perhaps Fe III. AU Mic has evidence of He II and S III emission, and β Gem shows S I emission. Differences are seen in line ratios and line profiles between these stars. In α Ori, these features are very weak or non-existent, and Fe II fluorescent lines in the 1100-1150 Å region, pumped by H I Lyman α , are present. Several emission lines are still unidentified in all spectra. Prospects for future cool star observations will be discussed. This work is based on data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by the Johns Hopkins University. Financial support to U. S. participants has been provided by NASA contract NAS5-32985.

  15. Self-healing fuse development.

    NASA Technical Reports Server (NTRS)

    Jones, N. D.

    1972-01-01

    The self-healing fuse is a very fast acting current overload protective device which opens and recloses in a few milliseconds. The fuse confines a mercury column in an insulated channel and returns the mercury to the channel after firing. Ratings 5 to 50 A at 600 peak volts are possible with a life of hundreds of cycles. Compared to conventional fuses, much less fault current energy fires the fuse by heating the mercury to boiling temperature. Next an arc discharge develops while explosive forces expel the liquid mercury from the channel. Then the high impedance arc either extinguishes immediately, or operates for a few milliseconds, until a switch opens the circuit.

  16. Calibration and display of distributed aperture sensor systems

    NASA Astrophysics Data System (ADS)

    Dale, Jason; Dwyer, David

    2007-04-01

    Distributed aperture sensor (DAS) systems can enhance the situational awareness of operators in both manned and unmanned platforms. In such a system, images from multiple sensors must be registered and fused into a seamless panoramic mosaic in real time, whilst being displayed with very low latency to an operator. This paper describes an algorithm for solving the multiple-image alignment problem and an architecture that leverages the power of consumer graphics processing units (GPU) to provide a live panoramic mosaic display. We also describe other developments aimed at integrating high resolution imagery from an independently steerable fused TV/IR sensor into the mosaic, panorama stabilisation and automatic target detection.

  17. Sub-Aperture Interferometers

    NASA Technical Reports Server (NTRS)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  18. Variable-aperture screen

    DOEpatents

    Savage, G.M.

    1991-10-29

    Apparatus is described for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function. 10 figures.

  19. Operations with the FUSE observatory

    NASA Astrophysics Data System (ADS)

    Blair, William P.; Kruk, Jeffrey W.; Moos, Henry W.; Oegerle, William R.

    2003-02-01

    The Far Ultraviolet Spectroscopic Explorer satellite (FUSE) is a NASA Origins mission launched on 1999 June 24 and operated from the Johns Hopkins University Homewood campus in Baltimore, MD. FUSE consists of four aligned telescopes feeding twin far-ultraviolet spectrographs that achieve a spectral resolution of R=20,000 over the 905-1187 Å spectral region. This makes FUSE complementary to the Hubble Space Telescope and of broad general interest to the astronomical community. FUSE is operated as a general-purpose observatory with proposals evaluated and selected by NASA. The FUSE mission concept evolved dramatically over time. The version of FUSE that was built and flown was born out of the "faster, better, cheaper" era, which drove not only the mission development but also plans for operations. Fixed price contracts, a commercial spacecraft, and operations in the University environment were all parts of the low cost strategy. The satellite performs most functions autonomously, with ground contacts limited typically to seven 12-minute contacts per day through a dedicated ground station. All support functions are managed by a staff of 40 scientists and engineers located at Johns Hopkins. In this configuration, we have been able to achieve close to 30% average on-target science efficiency. In short, FUSE is a successful example of the "faster, better, cheaper" philosophy.

  20. The distribution of subsurface damage in fused silica

    SciTech Connect

    Miller, P E; Suratwala, T I; Wong, L L; Feit, M D; Menapace, J A; Davis, P J; Steele, R A

    2005-11-21

    Managing subsurface damage during the shaping process and removing subsurface damage during the polishing process is essential in the production of low damage density optical components, such as those required for use on high peak power lasers. Removal of subsurface damage, during the polishing process, requires polishing to a depth which is greater than the depth of the residual cracks present following the shaping process. To successfully manage, and ultimately remove subsurface damage, understanding the distribution and character of fractures in the subsurface region introduced during fabrication process is important. We have characterized the depth and morphology of subsurface fractures present following fixed abrasive and loose abrasive grinding processes. At shallow depths lateral cracks and an overlapping series of trailing indentation fractures were found to be present. At greater depths, subsurface damage consists of a series of trailing indentation fractures. The area density of trailing fractures changes as a function of depth, however the length and shape of individual cracks remain nearly constant for a given grinding process. We have developed and applied a model to interpret the depth and crack length distributions of subsurface surface damage in terms of key variables including abrasive size and load.

  1. Computer Models of Micrometeoroid Impact on Fused Silica Glass Mirrors

    NASA Technical Reports Server (NTRS)

    Davison, David; Cour-Palais, Burton; Quan, X.; Holmquist, T. J.; Cohen, Lester; Ramsey, Ron; Cummings, Ramona; Hadaway, James (Technical Monitor)

    2002-01-01

    For the first (low energy) calculation both the particle and crater parameters (from tests at AU/HIF) were known, For the second (high energy) calculation, only the particle parameters were known. In both cases the computed craters agreed with historical data of impact on glass. Additional tests at AU/HIF are expected to confirm the results of the second calculation and to validate the technique for use at higher velocities.

  2. Optical Performance Modeling of FUSE Telescope Mirror

    NASA Technical Reports Server (NTRS)

    Saha, Timo T.; Ohl, Raymond G.; Friedman, Scott D.; Moos, H. Warren

    2000-01-01

    We describe the Metrology Data Processor (METDAT), the Optical Surface Analysis Code (OSAC), and their application to the image evaluation of the Far Ultraviolet Spectroscopic Explorer (FUSE) mirrors. The FUSE instrument - designed and developed by the Johns Hopkins University and launched in June 1999 is an astrophysics satellite which provides high resolution spectra (lambda/Delta(lambda) = 20,000 - 25,000) in the wavelength region from 90.5 to 118.7 nm The FUSE instrument is comprised of four co-aligned, normal incidence, off-axis parabolic mirrors, four Rowland circle spectrograph channels with holographic gratings, and delay line microchannel plate detectors. The OSAC code provides a comprehensive analysis of optical system performance, including the effects of optical surface misalignments, low spatial frequency deformations described by discrete polynomial terms, mid- and high-spatial frequency deformations (surface roughness), and diffraction due to the finite size of the aperture. Both normal incidence (traditionally infrared, visible, and near ultraviolet mirror systems) and grazing incidence (x-ray mirror systems) systems can be analyzed. The code also properly accounts for reflectance losses on the mirror surfaces. Low frequency surface errors are described in OSAC by using Zernike polynomials for normal incidence mirrors and Legendre-Fourier polynomials for grazing incidence mirrors. The scatter analysis of the mirror is based on scalar scatter theory. The program accepts simple autocovariance (ACV) function models or power spectral density (PSD) models derived from mirror surface metrology data as input to the scatter calculation. The end product of the program is a user-defined pixel array containing the system Point Spread Function (PSF). The METDAT routine is used in conjunction with the OSAC program. This code reads in laboratory metrology data in a normalized format. The code then fits the data using Zernike polynomials for normal incidence

  3. Differential Synthetic Aperture Ladar

    SciTech Connect

    Stappaerts, E A; Scharlemann, E

    2005-02-07

    We report a differential synthetic aperture ladar (DSAL) concept that relaxes platform and laser requirements compared to conventional SAL. Line-of-sight translation/vibration constraints are reduced by several orders of magnitude, while laser frequency stability is typically relaxed by an order of magnitude. The technique is most advantageous for shorter laser wavelengths, ultraviolet to mid-infrared. Analytical and modeling results, including the effect of speckle and atmospheric turbulence, are presented. Synthetic aperture ladars are of growing interest, and several theoretical and experimental papers have been published on the subject. Compared to RF synthetic aperture radar (SAR), platform/ladar motion and transmitter bandwidth constraints are especially demanding at optical wavelengths. For mid-IR and shorter wavelengths, deviations from a linear trajectory along the synthetic aperture length have to be submicron, or their magnitude must be measured to that precision for compensation. The laser coherence time has to be the synthetic aperture transit time, or transmitter phase has to be recorded and a correction applied on detection.

  4. Eyeglass: A Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, R; Dixit, S; Weisberg, A; Rushford, M

    2002-07-29

    Eyeglass is a very large aperture (25-100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage. Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48-0.72 {micro}m). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 m thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 {micro}m thick glass sheets, diffractively patterned to operate as coherent f/50 lens.

  5. Confocal coded aperture imaging

    DOEpatents

    Tobin, Jr., Kenneth William; Thomas, Jr., Clarence E.

    2001-01-01

    A method for imaging a target volume comprises the steps of: radiating a small bandwidth of energy toward the target volume; focusing the small bandwidth of energy into a beam; moving the target volume through a plurality of positions within the focused beam; collecting a beam of energy scattered from the target volume with a non-diffractive confocal coded aperture; generating a shadow image of said aperture from every point source of radiation in the target volume; and, reconstructing the shadow image into a 3-dimensional image of the every point source by mathematically correlating the shadow image with a digital or analog version of the coded aperture. The method can comprise the step of collecting the beam of energy scattered from the target volume with a Fresnel zone plate.

  6. FUSE Observations of Luminous Cool Stars

    NASA Astrophysics Data System (ADS)

    Dupree, A. K.; Young, P. R.; Ake, T. B.

    2000-12-01

    Luminous cool stars can address the evolution of magnetic activity and the dynamics of stellar winds and mass loss. The region of yellow supergiants in the HR diagram contains stars of intermediate mass both with coronas and those possessing a hot outer atmosphere in the presence of a strong wind (the ``hybrid'' stars). These hybrid objects hold particular significance for evolution studies because they represent the physically important connection between solar-like stars (with coronas and fast winds of low-mass loss rate) and the cool supergiant stars (Alpha Ori-like) with cool outer atmospheres and massive winds. The Far Ultraviolet Spectroscopic Explorer (FUSE) measured the chromospheric and transition region emissions of the bright G2 Ib supergiant Beta Draconis (HD 159181) on 9 May 2000. Two exposures through the large aperture totaled 7695 s and were obtained in all channels covering the region λ λ 912-1180. Emission from chromospheric and transition region ions (C III, O VI, Si III, S IV, S VI) is detected along with a number of low ion stages. Profiles of strong lines are asymmetric suggesting the presence of a wind. A short exposure (3260 s) of Alpha Aquarii (HD 209750), a hybrid supergiant also of spectral type G2 Ib was obtained June 29, 2000. Dynamics of the atmospheres can be inferred from line profiles. The atmospheric temperature distribution, densities, and scale sizes can be evaluated from line fluxes to characterize the differences between a coronal star and a hybrid supergiant. FUSE is a NASA Origins mission operated by The Johns Hopkins University. Funding for this research is provided through NASA Contract NAS-532985.

  7. Silica nephropathy.

    PubMed

    Ghahramani, N

    2010-07-01

    Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2) is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600-7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents. PMID:23022796

  8. Apodizer aperture for lasers

    DOEpatents

    Jorna, Siebe; Siebert, Larry D.; Brueckner, Keith A.

    1976-11-09

    An aperture attenuator for use with high power lasers which includes glass windows shaped and assembled to form an annulus chamber which is filled with a dye solution. The annulus chamber is shaped such that the section in alignment with the axis of the incident beam follows a curve which is represented by the equation y = (r - r.sub.o).sup.n.

  9. Coded aperture computed tomography

    NASA Astrophysics Data System (ADS)

    Choi, Kerkil; Brady, David J.

    2009-08-01

    Diverse physical measurements can be modeled by X-ray transforms. While X-ray tomography is the canonical example, reference structure tomography (RST) and coded aperture snapshot spectral imaging (CASSI) are examples of physically unrelated but mathematically equivalent sensor systems. Historically, most x-ray transform based systems sample continuous distributions and apply analytical inversion processes. On the other hand, RST and CASSI generate discrete multiplexed measurements implemented with coded apertures. This multiplexing of coded measurements allows for compression of measurements from a compressed sensing perspective. Compressed sensing (CS) is a revelation that if the object has a sparse representation in some basis, then a certain number, but typically much less than what is prescribed by Shannon's sampling rate, of random projections captures enough information for a highly accurate reconstruction of the object. This paper investigates the role of coded apertures in x-ray transform measurement systems (XTMs) in terms of data efficiency and reconstruction fidelity from a CS perspective. To conduct this, we construct a unified analysis using RST and CASSI measurement models. Also, we propose a novel compressive x-ray tomography measurement scheme which also exploits coding and multiplexing, and hence shares the analysis of the other two XTMs. Using this analysis, we perform a qualitative study on how coded apertures can be exploited to implement physical random projections by "regularizing" the measurement systems. Numerical studies and simulation results demonstrate several examples of the impact of coding.

  10. Optical sparse aperture imaging.

    PubMed

    Miller, Nicholas J; Dierking, Matthew P; Duncan, Bradley D

    2007-08-10

    The resolution of a conventional diffraction-limited imaging system is proportional to its pupil diameter. A primary goal of sparse aperture imaging is to enhance resolution while minimizing the total light collection area; the latter being desirable, in part, because of the cost of large, monolithic apertures. Performance metrics are defined and used to evaluate several sparse aperture arrays constructed from multiple, identical, circular subapertures. Subaperture piston and/or tilt effects on image quality are also considered. We selected arrays with compact nonredundant autocorrelations first described by Golay. We vary both the number of subapertures and their relative spacings to arrive at an optimized array. We report the results of an experiment in which we synthesized an image from multiple subaperture pupil fields by masking a large lens with a Golay array. For this experiment we imaged a slant edge feature of an ISO12233 resolution target in order to measure the modulation transfer function. We note the contrast reduction inherent in images formed through sparse aperture arrays and demonstrate the use of a Wiener-Helstrom filter to restore contrast in our experimental images. Finally, we describe a method to synthesize images from multiple subaperture focal plane intensity images using a phase retrieval algorithm to obtain estimates of subaperture pupil fields. Experimental results from synthesizing an image of a point object from multiple subaperture images are presented, and weaknesses of the phase retrieval method for this application are discussed. PMID:17694146

  11. Synthetic Aperture Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  12. Phasing rectangular apertures.

    PubMed

    Baker, K L; Homoelle, D; Utterback, E; Jones, S M

    2009-10-26

    Several techniques have been developed to phase apertures in the context of astronomical telescopes with segmented mirrors. Phasing multiple apertures, however, is important in a wide range of optical applications. The application of primary interest in this paper is the phasing of multiple short pulse laser beams for fast ignition fusion experiments. In this paper analytic expressions are derived for parameters such as the far-field distribution, a line-integrated form of the far-field distribution that could be fit to measured data, enclosed energy or energy-in-a-bucket and center-of-mass that can then be used to phase two rectangular apertures. Experimental data is taken with a MEMS device to simulate the two apertures and comparisons are made between the analytic parameters and those derived from the measurements. Two methods, fitting the measured far-field distribution to the theoretical distribution and measuring the ensquared energy in the far-field, produced overall phase variance between the 100 measurements of less than 0.005 rad(2) or an RMS displacement of less than 12 nm. PMID:19997175

  13. Temporal Aperture Modulation

    NASA Technical Reports Server (NTRS)

    Proctor, R. J.

    1981-01-01

    The two types of modulation techniques useful to X-ray imaging are reviewed. The use of optimum coded temporal aperature modulation is shown, in certain cases, to offer an advantage over a spatial aperture modulator. Example applications of a diffuse anisotropic X-ray background experiment and a wide field of view hard X-ray imager are discussed.

  14. Silica substrate or portion formed from oxidation of monocrystalline silicon

    DOEpatents

    Matzke, Carolyn M.; Rieger, Dennis J.; Ellis, Robert V.

    2003-07-15

    A method is disclosed for forming an inclusion-free silica substrate using a monocrystalline silicon substrate as the starting material and oxidizing the silicon substrate to convert it entirely to silica. The oxidation process is performed from both major surfaces of the silicon substrate using a conventional high-pressure oxidation system. The resulting product is an amorphous silica substrate which is expected to have superior etching characteristics for microfabrication than conventional fused silica substrates. The present invention can also be used to convert only a portion of a monocrystalline silicon substrate to silica by masking the silicon substrate and locally thinning a portion the silicon substrate prior to converting the silicon portion entirely to silica. In this case, the silica formed by oxidizing the thinned portion of the silicon substrate can be used, for example, as a window to provide optical access through the silicon substrate.

  15. Genetic apertures: an improved sparse aperture design framework.

    PubMed

    Salvaggio, Philip S; Schott, John R; McKeown, Donald M

    2016-04-20

    The majority of optical sparse aperture imaging research in the remote sensing field has been confined to a small set of aperture layouts. While these layouts possess some desirable properties for imaging, they may not be ideal for all applications. This work introduces an optimization framework for sparse aperture layouts based on genetic algorithms as well as a small set of fitness functions for incoherent sparse aperture image quality. The optimization results demonstrate the merits of existing designs and the opportunity for creating new sparse aperture layouts. PMID:27140086

  16. Aperture center energy showcase

    SciTech Connect

    Torres, J. J.

    2012-03-01

    Sandia and Forest City have established a Cooperative Research and Development Agreement (CRADA), and the partnership provides a unique opportunity to take technology research and development from demonstration to application in a sustainable community. A project under that CRADA, Aperture Center Energy Showcase, offers a means to develop exhibits and demonstrations that present feedback to community members, Sandia customers, and visitors. The technologies included in the showcase focus on renewable energy and its efficiency, and resilience. These technologies are generally scalable, and provide secure, efficient solutions to energy production, delivery, and usage. In addition to establishing an Energy Showcase, support offices and conference capabilities that facilitate research, collaboration, and demonstration were created. The Aperture Center project focuses on establishing a location that provides outreach, awareness, and demonstration of research findings, emerging technologies, and project developments to Sandia customers, visitors, and Mesa del Sol community members.

  17. Configurable Aperture Space Telescope

    NASA Technical Reports Server (NTRS)

    Ennico, Kimberly; Bendek, Eduardo

    2015-01-01

    In December 2014, we were awarded Center Innovation Fund to evaluate an optical and mechanical concept for a novel implementation of a segmented telescope based on modular, interconnected small sats (satlets). The concept is called CAST, a Configurable Aperture Space Telescope. With a current TRL is 2 we will aim to reach TLR 3 in Sept 2015 by demonstrating a 2x2 mirror system to validate our optical model and error budget, provide straw man mechanical architecture and structural damping analyses, and derive future satlet-based observatory performance requirements. CAST provides an alternative access to visible and/or UV wavelength space telescope with 1-meter or larger aperture for NASA SMD Astrophysics and Planetary Science community after the retirement of HST

  18. Synthetic Aperture Radiometer Systems

    NASA Technical Reports Server (NTRS)

    LeVine, David M.

    1999-01-01

    Aperture synthesis is a new technology for passive microwave remote sensing from space which has the potential to overcome the limitations set in the past by antenna size. This is an interferometric technique in which pairs of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has been demonstrated successfully at L-band with the aircraft prototype instrument, ESTAR. Proposals have been submitted to demonstrate this technology in space (HYDROSTAR and MIRAS).

  19. Integrated electrochromic aperture diaphragm

    NASA Astrophysics Data System (ADS)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

    In the last years, the triumphal march of handheld electronics with integrated cameras has opened amazing fields for small high performing optical systems. For this purpose miniaturized iris apertures are of practical importance because they are essential to control both the dynamic range of the imaging system and the depth of focus. Therefore, we invented a micro optical iris based on an electrochromic (EC) material. This material changes its absorption in response to an applied voltage. A coaxial arrangement of annular rings of the EC material is used to establish an iris aperture without need of any mechanical moving parts. The advantages of this device do not only arise from the space-saving design with a thickness of the device layer of 50μm. But it also benefits from low power consumption. In fact, its transmission state is stable in an open circuit, phrased memory effect. Only changes of the absorption require a voltage of up to 2 V. In contrast to mechanical iris apertures the absorption may be controlled on an analog scale offering the opportunity for apodization. These properties make our device the ideal candidate for battery powered and space-saving systems. We present optical measurements concerning control of the transmitted intensity and depth of focus, and studies dealing with switching times, light scattering, and stability. While the EC polymer used in this study still has limitations concerning color and contrast, the presented device features all functions of an iris aperture. In contrast to conventional devices it offers some special features. Owing to the variable chemistry of the EC material, its spectral response may be adjusted to certain applications like color filtering in different spectral regimes (UV, optical range, infrared). Furthermore, all segments may be switched individually to establish functions like spatial Fourier filtering or lateral tunable intensity filters.

  20. Aperture excited dielectric antennas

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

    1974-01-01

    The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

  1. Performance of large aperture tapered fiber phase conjugate mirror with high pulse energy and 1-kHz repetition rate.

    PubMed

    Zhao, Zhigang; Dong, Yantao; Pan, Sunqiang; Liu, Chong; Chen, Jun; Tong, Lixin; Gao, Qingsong; Tang, Chun

    2012-01-16

    A large aperture fused silica tapered fiber phase conjugate mirror is presented with a maximum 70% stimulated Brillouin scattering (SBS) reflectivity, which is obtained with 1 kHz repetition rate, 15 ns pulse width and 38 mJ input pulse energy. To the best of our knowledge, this is the highest SBS reflectivity ever reported by using optical fiber as a phase conjugate mirror for such high pulse repetition rate (1 kHz) and several tens of millijoule (mJ) input pulse energy. The influences of fiber end surface quality and pump pulse widths on SBS reflectivity are investigated experimentally. The results show that finer fiber end surface quality and longer input pulse widths are preferred for obtaining higher SBS reflectivity with higher input pulse energy. Double passing amplification experiments are also performed. 52 mJ pulse energy is achieved at 1 kHz repetition rate, with a reflected SBS pulse width of 1.5 ns and a M(2) factor of 2.3. The corresponding peak power reaches 34.6 MW. Obvious beam quality improvement is observed. PMID:22274534

  2. [Amorphous silica. Types, health effects of exposure, NDS].

    PubMed

    Woźniak, H; Wiecek, E

    1995-01-01

    Maximum allowable concentration (MAC) values for amorphous silica dust have not been identified in the Polish legal regulations up-to-date. In this work the authors review values of allowable (recommended) amorphous silica dust concentrations in other countries. Data on other types of amorphous silica (natural and synthetic) used in industry as well as data on health effects of exposure to these types of dust are presented. The work encompasses 42 entries in the references and one Table which includes the following proposed MAC values: Non-calcinate diatomaceous earth (diatomite) and synthetic silica: Total dust--10 mg/m3 Respirable dust--2 mg/m3 Calcinate diatomaceous earth (diatomite) and fused silica (vitreous silica): Total dust--2 mg/m3 Respirable dust--1 mg/m3. PMID:7637638

  3. 30 CFR 28.2 - Approved fuses.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... MINING PRODUCTS FUSES FOR USE WITH DIRECT CURRENT IN PROVIDING SHORT-CIRCUIT PROTECTION FOR TRAILING... this part, fuses shall be considered to be approved for use with direct current in providing...

  4. 30 CFR 28.2 - Approved fuses.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... MINING PRODUCTS FUSES FOR USE WITH DIRECT CURRENT IN PROVIDING SHORT-CIRCUIT PROTECTION FOR TRAILING... this part, fuses shall be considered to be approved for use with direct current in providing...

  5. 30 CFR 28.2 - Approved fuses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... MINING PRODUCTS FUSES FOR USE WITH DIRECT CURRENT IN PROVIDING SHORT-CIRCUIT PROTECTION FOR TRAILING... this part, fuses shall be considered to be approved for use with direct current in providing...

  6. 30 CFR 28.2 - Approved fuses.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... MINING PRODUCTS FUSES FOR USE WITH DIRECT CURRENT IN PROVIDING SHORT-CIRCUIT PROTECTION FOR TRAILING... this part, fuses shall be considered to be approved for use with direct current in providing...

  7. 16 CFR 1507.3 - Fuses.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS FIREWORKS DEVICES § 1507.3 Fuses. (a) Fireworks devices that require a fuse shall: (1) Utilize only a fuse that has been... it will support either the weight of the fireworks device plus 8 ounces of dead weight or double...

  8. 16 CFR 1507.3 - Fuses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS FIREWORKS DEVICES § 1507.3 Fuses. (a) Fireworks devices that require a fuse shall: (1) Utilize only a fuse that has been... it will support either the weight of the fireworks device plus 8 ounces of dead weight or double...

  9. 16 CFR 1507.3 - Fuses.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS FIREWORKS DEVICES § 1507.3 Fuses. (a) Fireworks devices that require a fuse shall: (1) Utilize only a fuse that has been... it will support either the weight of the fireworks device plus 8 ounces of dead weight or double...

  10. 16 CFR 1507.3 - Fuses.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS FIREWORKS DEVICES § 1507.3 Fuses. (a) Fireworks devices that require a fuse shall: (1) Utilize only a fuse that has been... it will support either the weight of the fireworks device plus 8 ounces of dead weight or double...

  11. 16 CFR 1507.3 - Fuses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS FIREWORKS DEVICES § 1507.3 Fuses. (a) Fireworks devices that require a fuse shall: (1) Utilize only a fuse that has been... it will support either the weight of the fireworks device plus 8 ounces of dead weight or double...

  12. 30 CFR 28.2 - Approved fuses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Approved fuses. 28.2 Section 28.2 Mineral... MINING PRODUCTS FUSES FOR USE WITH DIRECT CURRENT IN PROVIDING SHORT-CIRCUIT PROTECTION FOR TRAILING CABLES IN COAL MINES General Provisions § 28.2 Approved fuses. (a) On and after the effective date...

  13. Differential Optical Synthetic Aperture Radar

    DOEpatents

    Stappaerts, Eddy A.

    2005-04-12

    A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal "subapertures", each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

  14. New Aperture Partitioning Element

    NASA Astrophysics Data System (ADS)

    Griffin, S.; Calef, B.; Williams, S.

    Postprocessing in an optical system can be aided by adding an optical element to partition the pupil into a number of segments. When imaging through the atmosphere, the recorded data are blurred by temperature-induced variations in the index of refraction along the line of sight. Using speckle imaging techniques developed in the astronomy community, this blurring can be corrected to some degree. The effectiveness of these techniques is diminished by redundant baselines in the pupil. Partitioning the pupil reduces the degree of baseline redundancy, and therefore improves the quality of images that can be obtained from the system. It is possible to implement the described approach on an optical system with a segmented primary mirror, but not very practical. This is because most optical systems do not have segmented primary mirrors, and those that do have relatively low bandwidth positioning of segments due to their large mass and inertia. It is much more practical to position an active aperture partitioning element at an aft optics pupil of the optical system. This paper describes the design, implementation and testing of a new aperture partitioning element that is completely reflective and reconfigurable. The device uses four independent, annular segments that can be positioned with a high degree of accuracy without impacting optical wavefront of each segment. This mirror has been produced and is currently deployed and working on the 3.6 m telescope.

  15. FUSE satellite electrical power subsystem

    SciTech Connect

    Roufberg, L.; Noah, K.

    1998-07-01

    The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite will be placed into a low earth orbit to investigate astrophysical processes related to the formation and development of the early universe. The FUSE satellite is considered a pathfinder for NASA's Mid-Class Explorers (MIDEX). To reduce mission cost and development time while delivering quality science, NASA has enforced strict cost caps with a clear definition of high-level science objectives. As a result, a significant design driver for the electrical power subsystem (EPS) was to minimize cost. The FUSE EPS is a direct energy transfer, unregulated bus architecture, with batteries directly on the bus and solar array power limted by pulse-width-modulated shunt regulators. The power subsystem electronics (PSE) contains circuitry to control battery charging, provide power to the loads, and provide fault protection. The electronics is based on the PSE which Orbital (formerly, Fairchild Space) designed and built for NASA/GSFC's XTE spacecraft. However, the FUSE PSE design incorporates a number of unique features to meet the mission requirements. To minimize size of the solar panels due to stowed attachment constraints, GaAs/Ge solar cells were selected. This is the first time this type of large area, thinned solar cell with integral bypass diodes are being used for a NASA LEO mission. The solar panels support a satellite load power of 520W. Nickel Cadmium (NiCd) batteries are used which are identical to the RADARSAT-I design, except for different temperature sensors. This is the first mission for which Orbital is using SAFT NiCd batteries. The spacecraft bus, including the EPS, has successfully completed environmental testing and has been delivered for instrument integration. Tradeoffs involved in designing the EPS and selecting components based on the requirements are discussed. Analyses including solar array and battery sizing and energy balance are presented in addition to results from testing the flight

  16. Compounding in synthetic aperture imaging.

    PubMed

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-09-01

    A method for obtaining compound images using synthetic aperture data is investigated using a convex array transducer. The new approach allows spatial compounding to be performed for any number of angles without reducing the frame rate or temporal resolution. This important feature is an intrinsic property of how the compound images are constructed using synthetic aperture data and an improvement compared with how spatial compounding is obtained using conventional methods. The synthetic aperture compound images are created by exploiting the linearity of delay-and-sum beamformation for data collected from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance measure for tissue contrast resolution which quantifies the tradeoff between resolution loss and speckle reduction. The speckle information density is improved by 25% when comparing synthetic aperture compounding to a similar setup for compounding using dynamic receive focusing. The cystic resolution and clutter levels are measured using a wire phantom setup and compared with conventional application of the array, as well as to synthetic aperture imaging without compounding. If the full aperture is used for synthetic aperture compounding, the cystic resolution is improved by 41% compared with conventional imaging, and is at least as good as what can be obtained using synthetic aperture imaging without compounding. PMID:23007781

  17. Diagnostic for dynamic aperture

    SciTech Connect

    Morton, P.L.; Pellegrin, J.L.; Raubenheimer, T.; Rivkin, L.; Ross, M.; Ruth, R.D.; Spence, W.L.

    1985-04-01

    In large accelerators and low beta colliding beam storage rings, the strong sextupoles, which are required to correct the chromatic effects, produce strong nonlinear forces which act on particles in the beam. In addition in large hadron storage rings the superconducting magnets have significant nonlinear fields. To understand the effects of these nonlinearities on the particle motion there is currently a large theoretical effort using both analytic techniques and computer tracking. This effort is focused on the determination of the 'dynamic aperture' (the stable acceptance) of both present and future accelerators and storage rings. A great deal of progress has been made in understanding nonlinear particle motion, but very little experimental verification of the theoretical results is available. In this paper we describe 'dynamic tracking', a method being studied at the SPEAR storage ring, which can be used to obtain experimental results which are in a convenient form to be compared with the theoretical predictions.

  18. Optica aperture synthesis

    NASA Astrophysics Data System (ADS)

    van der Avoort, Casper

    2006-05-01

    Optical long baseline stellar interferometry is an observational technique in astronomy that already exists for over a century, but is truly blooming during the last decades. The undoubted value of stellar interferometry as a technique to measure stellar parameters beyond the classical resolution limit is more and more spreading to the regime of synthesis imaging. With optical aperture synthesis imaging, the measurement of parameters is extended to the reconstruction of high resolution stellar images. A number of optical telescope arrays for synthesis imaging are operational on Earth, while space-based telescope arrays are being designed. For all imaging arrays, the combination of the light collected by the telescopes in the array can be performed in a number of ways. In this thesis, methods are introduced to model these methods of beam combination and compare their effectiveness in the generation of data to be used to reconstruct the image of a stellar object. One of these methods of beam combination is to be applied in a future space telescope. The European Space Agency is developing a mission that can valuably be extended with an imaging beam combiner. This mission is labeled Darwin, as its main goal is to provide information on the origin of life. The primary objective is the detection of planets around nearby stars - called exoplanets- and more precisely, Earth-like exoplanets. This detection is based on a signal, rather than an image. With an imaging mode, designed as described in this thesis, Darwin can make images of, for example, the planetary system to which the detected exoplanet belongs or, as another example, of the dust disk around a star out of which planets form. Such images will greatly contribute to the understanding of the formation of our own planetary system and of how and when life became possible on Earth. The comparison of beam combination methods for interferometric imaging occupies most of the pages of this thesis. Additional chapters will

  19. Material Measurements Using Groundplane Apertures

    NASA Technical Reports Server (NTRS)

    Komisarek, K.; Dominek, A.; Wang, N.

    1995-01-01

    A technique for material parameter determination using an aperture in a groundplane is studied. The material parameters are found by relating the measured reflected field in the aperture to a numerical model. Two apertures are studied which can have a variety of different material configurations covering the aperture. The aperture cross-sections studied are rectangular and coaxial. The material configurations involved combinations of single layer and dual layers with or without a resistive exterior resistive sheet. The resistivity of the resistive sheet can be specified to simulate a perfect electric conductor (PEC) backing (0 Ohms/square) to a free space backing (infinity Ohms/square). Numerical parameter studies and measurements were performed to assess the feasibility of the technique.

  20. Optical and transport properties of dense liquid silica

    SciTech Connect

    Qi, Tingting; Millot, Marius; Kraus, Richard G.; Hamel, Sebastien; Root, Seth

    2015-06-15

    Using density-functional-theory based molecular dynamics and the Kubo-Greenwood linear response theory, we evaluated the high-pressure equation of state and the optical and transport properties of quartz and fused silica shock-compressed to 2000 GPa. The computed Hugoniots and corresponding optical reflectivity values are in very good agreement with published data for quartz, and new data that we obtained on fused silica using magnetically launched flyer plate experiments. The rise of optical reflectivity upon shock compression appears to be primarily a temperature-driven mechanism, which is relatively insensitive to small density variation. We observed that the electrical conductivity does not display Drude-like frequency dependence, especially at lower temperatures. In addition, the Wiedemann-Franz relation between electrical and thermal conductivities was found to be invalid. It suggests that even at three-fold compression, warm dense liquid silica on the Hugoniot curve is still far away from the degenerate limit.

  1. Optical and transport properties of dense liquid silica

    NASA Astrophysics Data System (ADS)

    Qi, Tingting; Millot, Marius; Kraus, Richard G.; Root, Seth; Hamel, Sebastien

    2015-06-01

    Using density-functional-theory based molecular dynamics and the Kubo-Greenwood linear response theory, we evaluated the high-pressure equation of state and the optical and transport properties of quartz and fused silica shock-compressed to 2000 GPa. The computed Hugoniots and corresponding optical reflectivity values are in very good agreement with published data for quartz, and new data that we obtained on fused silica using magnetically launched flyer plate experiments. The rise of optical reflectivity upon shock compression appears to be primarily a temperature-driven mechanism, which is relatively insensitive to small density variation. We observed that the electrical conductivity does not display Drude-like frequency dependence, especially at lower temperatures. In addition, the Wiedemann-Franz relation between electrical and thermal conductivities was found to be invalid. It suggests that even at three-fold compression, warm dense liquid silica on the Hugoniot curve is still far away from the degenerate limit.

  2. Interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    Ralston, Tyler S.; Marks, Daniel L.; Scott Carney, P.; Boppart, Stephen A.

    2007-02-01

    State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the light-sample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe and demonstrate a novel computational image-formation technique called interferometric synthetic aperture microscopy (ISAM). ISAM has the potential to broadly impact real-time three-dimensional microscopy and analysis in the fields of cell and tumour biology, as well as in clinical diagnosis where in vivo imaging is preferable to biopsy.

  3. Interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    Ralston, Tyler S.

    State-of-the-art interferometric microscopies have problems representing objects that lie outside of the focus because the defocus and diffraction effects are not accounted for in the processing. These problems occur because of the lack of comprehensive models to include the scattering effects in the processing. In this dissertation, a new modality in three-dimensional (3D) optical microscopy, Interferometric Synthetic Aperture Microscopy (ISAM), is introduced to account for the scattering effects. Comprehensive models for interferometric microscopy, such as optical coherence tomography (OCT) are developed, for which forward, adjoint, normal, and inverse operators are formulated. Using an accurate model for the probe beam, the resulting algorithms demonstrate accurate linear estimation of the susceptibility of an object from the interferometric data. Using the regularized least squares solution, an ISAM reconstruction of underlying object structure having spatially invariant resolution is obtained from simulated and experimental interferometric data, even in regions outside of the focal plane of the lens. Two-dimensional (2D) and 3D interferometric data is used to resolve objects outside of the confocal region with minimal loss of resolution, unlike in OCT. Therefore, high-resolution details are recovered from outside of the confocal region. Models and solutions are presented for the planar-scanned, the rotationally scanned, and the full-field illuminated geometry. The models and algorithms presented account for the effects of a finite beam width, the source spectrum, the illumination and collection fields, as well as defocus, diffraction and dispersion effects.

  4. Sparse aperture endoscope

    DOEpatents

    Fitch, Joseph P.

    1999-07-06

    An endoscope which reduces the volume needed by the imaging part thereof, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases the utility thereof. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing.

  5. Sparse aperture endoscope

    DOEpatents

    Fitch, J.P.

    1999-07-06

    An endoscope is disclosed which reduces the volume needed by the imaging part, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases it's utility. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing. 7 figs.

  6. FUSE observations of Luminous Blue Variables

    NASA Astrophysics Data System (ADS)

    Iping, Rosina C.; Sonneborn, George; Massa, Derck L.

    P Cyg, AG Car, HD 5980 and η Car were observed with the Far Ultraviolet Spectroscopic Explorer ( FUSE) satellite. FUSE covers the spectral range from 980 Å to 1187 Å at a resolution of 0.05 Å. In this paper we discuss the far-UV properties of these LBVs and explore their similarities and differences. The FUSE observations of P Cyg and AG Car, both spectral type B2pe, are very similar. The atmospheres of both η Car and HD 5980 appear to be somewhat hotter and have much higher ionization stages (Si IV, S IV, and P V) in the FUSE spectrum than P Cyg and AG Car. There is a very good agreement between the FUSE spectrum of P Cygni and the model atmosphere computed by John Hillier with his code CMFGEN. The FUSE spectrum of η Car, however, does not agree very well with existing model spectra.

  7. Lucky imaging and aperture synthesis with low-redundancy apertures.

    PubMed

    Ward, Jennifer E; Rhodes, William T; Sheridan, John T

    2009-01-01

    Lucky imaging, used with some success in astronomical and even horizontal-path imaging, relies on fleeting conditions of the atmosphere that allow momentary improvements in image quality, at least in portions of an image. Aperture synthesis allows a larger aperture and, thus, a higher-resolution imaging system to be synthesized through the superposition of image spatial-frequency components gathered by cooperative combinations of smaller subapertures. A combination of lucky imaging and aperture synthesis strengthens both methods for obtaining improved images through the turbulent atmosphere. We realize the lucky imaging condition appropriate for aperture synthesis imaging for a pair of rectangular subapertures and demonstrate that this condition occurs when the signal energy associated with bandpass spatial-frequency components achieves its maximum value. PMID:19107157

  8. Internal fuse modules for solid tantalum capacitors

    NASA Technical Reports Server (NTRS)

    Dematos, H. V.

    1981-01-01

    Miniature fuse modules were designed for and incorporated into two styles of solid tantalum capacitors. One is an epoxy molded, radial leaded, high frequency decoupling capacitor; the other is an hermetically sealed device with axial lead wires. The fusible element for both devices consists of a fine bimetallic wire which reacts exothermically upon reaching a critical temperature and then disintegrates. The desirability of having fused devices is discussed and design constraints, in particular those which minimize inductance and series resistance while optimizing fuse actuation characteristics, are reviewed. Factors affecting the amount of energy required to actuate the fuse and reliability of acuation are identified.

  9. Integrated fuses for OLED lighting device

    DOEpatents

    Pschenitzka, Florian

    2007-07-10

    An embodiment of the present invention pertains to an electroluminescent lighting device for area illumination. The lighting device is fault tolerant due, in part, to the patterning of one or both of the electrodes into strips, and each of one or more of these strips has a fuse formed on it. The fuses are integrated on the substrate. By using the integrated fuses, the number of external contacts that are used is minimized. The fuse material is deposited using one of the deposition techniques that is used to deposit the thin layers of the electroluminescent lighting device.

  10. Bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Yates, Gillian

    Synthetic aperture radar (SAR) allows all-weather, day and night, surface surveillance and has the ability to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and the receiver are on separate platforms, is seen as a potential means of countering the vulnerability of conventional monostatic SAR to electronic countermeasures, particularly directional jamming, and avoiding physical attack of the imaging platform. As the receiving platform can be totally passive, it does not advertise its position by RF emissions. The transmitter is not susceptible to jamming and can, for example, operate at long stand-off ranges to reduce its vulnerability to physical attack. This thesis examines some of the complications involved in producing high-resolution bistatic SAR imagery. The effect of bistatic operation on resolution is examined from a theoretical viewpoint and analytical expressions for resolution are developed. These expressions are verified by simulation work using a simple 'point by point' processor. This work is extended to look at using modern practical processing engines for bistatic geometries. Adaptations of the polar format algorithm and range migration algorithm are considered. The principal achievement of this work is a fully airborne demonstration of bistatic SAR. The route taken in reaching this is given, along with some results. The bistatic SAR imagery is analysed and compared to the monostatic imagery collected at the same time. Demonstrating high-resolution bistatic SAR imagery using two airborne platforms represents what I believe to be a European first and is likely to be the first time that this has been achieved outside the US (the UK has very little insight into US work on this topic). Bistatic target characteristics are examined through the use of simulations. This also compares bistatic imagery with monostatic and gives further insight into the utility of bistatic SAR.

  11. Superresolution and Synthetic Aperture Radar

    SciTech Connect

    DICKEY,FRED M.; ROMERO,LOUIS; DOERRY,ARMIN W.

    2001-05-01

    Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. A criterion for judging superresolution processing of an image is presented.

  12. The effect of heat treatment on the magnitude and composition of residual gas in sealed silica glass ampoules

    NASA Technical Reports Server (NTRS)

    Palosz, W.; Szofran, F. R.; Lehoczky, S. L.

    1994-01-01

    The residual gas pressure and composition in sealed silica glass ampoules as a function of different treatment procedures has been investigated. The dependence of the residual gas on the outgassing and annealing parameters has been determined. The effects of the fused silica brand, of the ampoule fabrication, and of post-outgassing procedures have been evaluated.

  13. Precise Sealing of Fused-Quartz Ampoules

    NASA Technical Reports Server (NTRS)

    Debnan, W. J. J.; Clark, I. O.

    1982-01-01

    New technique rapidly evacuates and seals fused-quartz ampoule with precise clearance over contents without appreciably thinning ampoule walls. Quartz plug is lowered into working section of ampoule after ampoule has been evacuated. Plug is then fused to ampoule walls, forming vacuum seal. New technique maintains wall strength and pumping speed.

  14. Blast Off into Space Science with Fuses.

    ERIC Educational Resources Information Center

    Bombaugh, Ruth

    2000-01-01

    Introduces an activity in which students build a fuse with steel, wood, light bulbs, copper wire, clay, and batteries. Uses the cross-age instructional approach to teach about the value of instructional time. Contains directions for building a fuse. (YDS)

  15. 30 CFR 18.52 - Renewal of fuses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Renewal of fuses. 18.52 Section 18.52 Mineral... § 18.52 Renewal of fuses. Enclosure covers that provide access to fuses, other than headlight, control-circuit, and handheld-tool fuses, shall be interlocked with a circuit-interrupting device. Fuses shall...

  16. Large Aperture Multiplexed Diffractive Lidar Optics

    NASA Technical Reports Server (NTRS)

    Rallison, Richard D.; Schwemmer, Geary K. (Technical Monitor)

    1999-01-01

    We have delivered only 2 or 3 UV Holographic Optical Elements (HOEs) thus far and have fallen short of the intended goal in size and in dual wavelength function. Looking back, it has been fortuitous that we even made anything work in the UV region. It was our good fortune to discover that the material we work with daily was adequate for use at 355 nm, if well rinsed during processing. If we had stuck to our original plan of etching in small pieces of fused silica, we would still be trying to make the first small section in our ion mill, which is not yet operational. The original plan was far too ambitious and would take another 2 years to complete beginning where we left off this time. In order to make a HOE for the IR as well as the UV we will likely have to learn to sensitize some film to the 1064 line and we have obtained sensitizer that is reported to work in that region already. That work would also take an additional year to complete.

  17. Microgravity Manufacturing Via Fused Deposition

    NASA Technical Reports Server (NTRS)

    Cooper, K. G.; Griffin, M. R.

    2003-01-01

    Manufacturing polymer hardware during space flight is currently outside the state of the art. A process called fused deposition modeling (FDM) can make this approach a reality by producing net-shaped components of polymer materials directly from a CAE model. FDM is a rapid prototyping process developed by Stratasys, Inc.. which deposits a fine line of semi-molten polymer onto a substrate while moving via computer control to form the cross-sectional shape of the part it is building. The build platen is then lowered and the process is repeated, building a component directly layer by layer. This method enables direct net-shaped production of polymer components directly from a computer file. The layered manufacturing process allows for the manufacture of complex shapes and internal cavities otherwise impossible to machine. This task demonstrated the benefits of the FDM technique to quickly and inexpensively produce replacement components or repair broken hardware in a Space Shuttle or Space Station environment. The intent of the task was to develop and fabricate an FDM system that was lightweight, compact, and required minimum power consumption to fabricate ABS plastic hardware in microgravity. The final product of the shortened task turned out to be a ground-based breadboard device, demonstrating miniaturization capability of the system.

  18. Laser welding of fused quartz

    DOEpatents

    Piltch, Martin S.; Carpenter, Robert W.; Archer, III, McIlwaine

    2003-06-10

    Refractory materials, such as fused quartz plates and rods are welded using a heat source, such as a high power continuous wave carbon dioxide laser. The radiation is optimized through a process of varying the power, the focus, and the feed rates of the laser such that full penetration welds may be accomplished. The process of optimization varies the characteristic wavelengths of the laser until the radiation is almost completely absorbed by the refractory material, thereby leading to a very rapid heating of the material to the melting point. This optimization naturally occurs when a carbon dioxide laser is used to weld quartz. As such this method of quartz welding creates a minimum sized heat-affected zone. Furthermore, the welding apparatus and process requires a ventilation system to carry away the silicon oxides that are produced during the welding process to avoid the deposition of the silicon oxides on the surface of the quartz plates or the contamination of the welds with the silicon oxides.

  19. Temperature dependence of the absorption edge of vitreous silica

    NASA Technical Reports Server (NTRS)

    Bates, C. W., Jr.

    1976-01-01

    During an investigation of the optical properties of high-purity vitreous silica (fused quartz), which is being developed by NASA as a reflective and ablative heat shield, some interesting properties of theoretical and experimental nature have become apparent which otherwise may have remained unnoticed. Of particular interest for the NASA application is the shift of the absorption edge toward longer wavelengths with increasing temperature. The results of studies of this shift and of the spectral dependence of the absorption edge are summarized in the present paper. Plots of the absorption edge and the absorption spectrum of fused quartz vs temperature are given and discussed.

  20. Metamaterial Apertures for Computational Imaging

    NASA Astrophysics Data System (ADS)

    Hunt, John; Driscoll, Tom; Mrozack, Alex; Lipworth, Guy; Reynolds, Matthew; Brady, David; Smith, David R.

    2013-01-01

    By leveraging metamaterials and compressive imaging, a low-profile aperture capable of microwave imaging without lenses, moving parts, or phase shifters is demonstrated. This designer aperture allows image compression to be performed on the physical hardware layer rather than in the postprocessing stage, thus averting the detector, storage, and transmission costs associated with full diffraction-limited sampling of a scene. A guided-wave metamaterial aperture is used to perform compressive image reconstruction at 10 frames per second of two-dimensional (range and angle) sparse still and video scenes at K-band (18 to 26 gigahertz) frequencies, using frequency diversity to avoid mechanical scanning. Image acquisition is accomplished with a 40:1 compression ratio.

  1. Launch of NASA's FUSE satellite from CCAS.

    NASA Technical Reports Server (NTRS)

    1999-01-01

    As light peers over the horizon at the crack of dawn, NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite waits for launch on Launch Pad 17A, Cape Canaveral Air Station, aboard the Boeing Delta II rocket. Liftoff is scheduled for 11:39 a.m. EDT. FUSE was developed to investigate the origin and evolution of the lightest elements in the universe - hydrogen and deuterium. In addition, the FUSE satellite will examine the forces and process involved in the evolution of the galaxies, stars and planetary systems by investigating light in the far ultraviolet portion of the electromagnetic spectrum.

  2. Workers at CCAS move the FUSE satellite.

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite stands in the Hangar A&E, Cape Canaveral Air Station (CCAS), ready for its launch, targeted for June 23 from Launch Pad 17A, CCAS aboard a Boeing Delta II rocket. FUSE was developed by The Johns Hopkins University under contract to Goddard Space Flight Center, Greenbelt, Md., to investigate the origin and evolution of the lightest elements in the universe - hydrogen and deuterium. In addition, the FUSE satellite will examine the forces and process involved in the evolution of the galaxies, stars and planetary systems by investigating light in the far ultraviolet portion of the electromagnetic spectrum.

  3. Launch of NASA's FUSE satellite from CCAS.

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The Boeing Delta II rocket carrying NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite clears the tower after liftoff at 11:44 a.m. EDT from Launch Pad 17A, Cape Canaveral Air Station. FUSE was developed to investigate the origin and evolution of the lightest elements in the universe - hydrogen and deuterium. In addition, the FUSE satellite will examine the forces and process involved in the evolution of the galaxies, stars and planetary systems by investigating light in the far ultraviolet portion of the electromagnetic spectrum.

  4. Launch of NASA's FUSE satellite from CCAS.

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Clouds of smoke and steam billow around the Boeing Delta II rocket as it roars into the sky after liftoff at 11:44 a.m. EDT from Launch Pad 17A, Cape Canaveral Air Station. The rocket is carrying NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. FUSE was developed to investigate the origin and evolution of the lightest elements in the universe - hydrogen and deuterium. In addition, the FUSE satellite will examine the forces and process involved in the evolution of the galaxies, stars and planetary systems by investigating light in the far ultraviolet portion of the electromagnetic spectrum.

  5. Launch of NASA's FUSE satellite from CCAS.

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite sits on Launch Pad 17A, Cape Canaveral Air Station, aboard the Boeing Delta II rocket waiting for launch. Liftoff is scheduled for 11:39 a.m. EDT. FUSE was developed to investigate the origin and evolution of the lightest elements in the universe - hydrogen and deuterium. In addition, the FUSE satellite will examine the forces and process involved in the evolution of the galaxies, stars and planetary systems by investigating light in the far ultraviolet portion of the electromagnetic spectrum.

  6. Regioselective Oxidation of Fused-Pentagon Chlorofullerenes.

    PubMed

    Zhang, Zhen-Qiang; Chen, Shu-Fen; Gao, Cong-Li; Zhou, Ting; Shan, Gui-Juan; Tan, Yuan-Zhi; Xie, Su-Yuan; Huang, Rong-Bin; Zheng, Lan-Sun

    2016-01-19

    Two monoxides of typical smaller chlorofullerenes, (#271)C50Cl10O and (#913)C56Cl10O, featured with double-fused-pentagons, were synthesized to demonstrate further regioselective functionalization of non-IPR (IPR = isolated pentagon rule) chlorofullerenes. Both non-IPR chlorofullerene oxides exhibit an epoxy structure at the ortho-site of fused pentagons. In terms of the geometrical analysis and theoretical calculations, the principles for regioselective epoxy oxidation of non-IPR chlorofullerenes are revealed to follow both "fused-pentagon ortho-site" and "olefinic bond" rules, which are valuable for prediction of oxidation of non-IPR chlorofullerenes. PMID:26726707

  7. A flat laser array aperture

    NASA Astrophysics Data System (ADS)

    Papadakis, Stergios J.; Ricciardi, Gerald F.; Gross, Michael C.; Krill, Jerry A.

    2010-04-01

    We describe a design concept for a flat (or conformal) thin-plate laser phased-array aperture. The aperture consists of a substrate supporting a grid of single-mode optical waveguides fabricated from a linear electro-optic material. The waveguides are coupled to a single laser source or detector. An arrangement of electrodes provides for two-dimensional beam steering by controlling the phase of the light entering the grid. The electrodes can also be modulated to simultaneously provide atmospheric turbulence modulation for long-range free-space optical communication. An approach for fabrication is also outlined.

  8. Mosaic of coded aperture arrays

    DOEpatents

    Fenimore, Edward E.; Cannon, Thomas M.

    1980-01-01

    The present invention pertains to a mosaic of coded aperture arrays which is capable of imaging off-axis sources with minimum detector size. Mosaics of the basic array pattern create a circular on periodic correlation of the object on a section of the picture plane. This section consists of elements of the central basic pattern as well as elements from neighboring patterns and is a cyclic version of the basic pattern. Since all object points contribute a complete cyclic version of the basic pattern, a section of the picture, which is the size of the basic aperture pattern, contains all the information necessary to image the object with no artifacts.

  9. High resolution non-iterative aperture synthesis.

    PubMed

    Kraczek, Jeffrey R; McManamon, Paul F; Watson, Edward A

    2016-03-21

    The maximum resolution of a multiple-input multiple-output (MIMO) imaging system is determined by the size of the synthetic aperture. The synthetic aperture is determined by a coordinate shift using the relative positions of the illuminators and receive apertures. Previous methods have shown non-iterative phasing for multiple illuminators with a single receive aperture for intra-aperture synthesis. This work shows non-iterative phasing with both multiple illuminators and multiple receive apertures for inter-aperture synthesis. Simulated results show that piston, tip, and tilt can be calculated using inter-aperture phasing after intra-aperture phasing has been performed. Use of a fourth illuminator for increased resolution is shown. The modulation transfer function (MTF) is used to quantitatively judge increased resolution. PMID:27136816

  10. Coordination chemistry in fused-salt solutions

    NASA Technical Reports Server (NTRS)

    Gruen, D. M.

    1969-01-01

    Spectrophotometric work on structural determinations with fused-salt solutions is reviewed. Constraints placed on the method, as well as interpretation of the spectra, are discussed with parallels drawn to aqueous spectrophotometric curves of the same materials.

  11. The Legacy of the FUSE Mission

    NASA Technical Reports Server (NTRS)

    Sonneborne, George

    2012-01-01

    The Far Ultraviolet Spectroscopic Explorer (FUSE) mission was a far-ultraviolet space telescope that performed high resolution (R=20,OOO) spectroscopy in the 905 - 1187 A spectral range. FUSE primarily observed stars and distant galaxies to study interstellar and intergalactic gas through absorption spectroscopy, as well as the properties of the objects themselves. This capability complemented the Hubble Space Telescope at longer wavelengths, and provided the international astronomical community with access to an important part of the electromagnetic spectrum. FUSE was a joint project of NASA, CNES, and CSA. The mission operated from 1999 to 2007. This review talk will summarize the scientific impact of the FUSE mission on several key scientific problems, as well as lessons learned for future mission concepts.

  12. Process for energy reduction with flash fusing

    SciTech Connect

    Berkes, J.S.

    1987-10-06

    This patent describes a process for affecting a reduction in the energy needed for accomplishing the flash fusing of a developed image which comprises (1) providing a toner composition with resin particles, pigment articles, and wax. The wax possesses a lower melting temperature than the resin particles and is selected from the group consisting of polyethylene and polypropylene with a molecular weight of less than about 6,000; (2) introducing the aforementioned toner composition into a xerographic imaging apparatus having incorporated therein a flash fusing device; (3) generating an electrostatic latent image in the imaging apparatus, and subsequently developing this image with the toner composition; (4) transferring the image to a supporting substrate; and (5) permanently attaching the image to the substrate with energy emitted from a flash fusing device, and wherein there is formed between the supporting substrate and the toner composition during fusing a wax layer.

  13. Electrodeposition of microcrystalline chromium from fused salts

    SciTech Connect

    Vargas, T.; Varma, R.; Brown, A.

    1987-01-01

    Chromium can be conveniently electroplated from fused chloride electrolytes. The deposition from LiCl-KCl (eutectic)-CrCl/sub 2/ melts is known to produce large crystal grains. Large grain size and other problems encountered in the electrodeposition of microcrystalline chromium from fused salt are discussed. The results indicate that combined use of forced electrolyte convection and a nucleating pulse in conjunction with a periodic reverse pulse produces fine-grained deposits.

  14. Dynamic aperture measurement on Aladdin

    SciTech Connect

    Bridges, J.; Cho, Y.; Chou, W.; Crosbie, E.; Kramer, S.; Kustom, R.; Voss, D.; Teng, L.; Kleman, K.; Otte, R.; Trzeciak, W.; Symon, K.; Wisconsin Univ., Stoughton, WI . Synchrotron Radiation Center; Wisconsin Univ., Madison, WI . Dept. of Physics)

    1989-01-01

    The sextupole-induced non-linear transverse beam dynamics in the synchrotron radiation storage ring Aladdin is studied. Specifically, the dynamic aperture is measured as function of the sextupole strength. The results agree reasonably well with computer simulations. 1 ref., 8 figs., 1 tab.

  15. Large aperture diffractive space telescope

    DOEpatents

    Hyde, Roderick A.

    2001-01-01

    A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

  16. Future of synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Barath, F. T.

    1978-01-01

    The present status of the applications of Synthetic Aperture Radars (SARs) is reviewed, and the technology state-of-the art as represented by the Seasat-A and SIR-A SARs examined. The potential of SAR applications, and the near- and longer-term technology trends are assessed.

  17. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  18. Multifunctional mesoporous silica catalyst

    DOEpatents

    Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

    2015-03-31

    The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

  19. What Is Crystalline Silica?

    MedlinePlus

    ... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

  20. Silica extraction from geothermal water

    SciTech Connect

    Bourcier, William L; Bruton, Carol J

    2014-09-23

    A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

  1. Processing pathway dependence of amorphous silica nanoparticle toxicity: colloidal vs pyrolytic.

    PubMed

    Zhang, Haiyuan; Dunphy, Darren R; Jiang, Xingmao; Meng, Huan; Sun, Bingbing; Tarn, Derrick; Xue, Min; Wang, Xiang; Lin, Sijie; Ji, Zhaoxia; Li, Ruibin; Garcia, Fred L; Yang, Jing; Kirk, Martin L; Xia, Tian; Zink, Jeffrey I; Nel, Andre; Brinker, C Jeffrey

    2012-09-26

    We have developed structure/toxicity relationships for amorphous silica nanoparticles (NPs) synthesized through low-temperature colloidal (e.g., Stöber silica) or high-temperature pyrolysis (e.g., fumed silica) routes. Through combined spectroscopic and physical analyses, we have determined the state of aggregation, hydroxyl concentration, relative proportion of strained and unstrained siloxane rings, and potential to generate hydroxyl radicals for Stöber and fumed silica NPs with comparable primary particle sizes (16 nm in diameter). On the basis of erythrocyte hemolytic assays and assessment of the viability and ATP levels in epithelial and macrophage cells, we discovered for fumed silica an important toxicity relationship to postsynthesis thermal annealing or environmental exposure, whereas colloidal silicas were essentially nontoxic under identical treatment conditions. Specifically, we find for fumed silica a positive correlation of toxicity with hydroxyl concentration and its potential to generate reactive oxygen species (ROS) and cause red blood cell hemolysis. We propose fumed silica toxicity stems from its intrinsic population of strained three-membered rings (3MRs) along with its chainlike aggregation and hydroxyl content. Hydrogen-bonding and electrostatic interactions of the silanol surfaces of fumed silica aggregates with the extracellular plasma membrane cause membrane perturbations sensed by the Nalp3 inflammasome, whose subsequent activation leads to secretion of the cytokine IL-1β. Hydroxyl radicals generated by the strained 3MRs in fumed silica, but largely absent in colloidal silicas, may contribute to the inflammasome activation. Formation of colloidal silica into aggregates mimicking those of fumed silica had no effect on cell viability or hemolysis. This study emphasizes that not all amorphous silicas are created equal and that the unusual toxicity of fumed silica compared to that of colloidal silica derives from its framework and surface

  2. Processing pathway dependence of amorphous silica nanoparticle toxicity - colloidal versus pyrolytic

    PubMed Central

    Zhang, Haiyuan; Dunphy, Darren R.; Jiang, Xingmao; Meng, Huan; Sun, Bingbing; Tarn, Derrick; Xue, Min; Wang, Xiang; Lin, Sijie; Ji, Zhaoxia; Li, Ruibin; Garcia, Fred L.; Yang, Jing; Kirk, Martin L.; Xia, Tian; Zink, Jeffrey I; Nel, Andre; Brinker, C. Jeffrey

    2012-01-01

    We have developed structure/toxicity relationships for amorphous silica nanoparticles (NPs) synthesized through low temperature, colloidal (e.g. Stöber silica) or high temperature pyrolysis (e.g. fumed silica) routes. Through combined spectroscopic and physical analyses, we have determined the state of aggregation, hydroxyl concentration, relative proportion of strained and unstrained siloxane rings, and potential to generate hydroxyl radicals for Stöber and fumed silica NPs with comparable primary particle sizes (16-nm in diameter). Based on erythrocyte hemolytic assays and assessment of the viability and ATP levels in epithelial and macrophage cells, we discovered for fumed silica an important toxicity relationship to post-synthesis thermal annealing or environmental exposure, whereas colloidal silicas were essentially non-toxic under identical treatment conditions. Specifically, we find for fumed silica a positive correlation of toxicity with hydroxyl concentration and its potential to generate reactive oxygen species (ROS) and cause red blood cell hemolysis. We propose fumed silica toxicity stems from its intrinsic population of strained three-membered rings (3MRs) along with its chain-like aggregation and hydroxyl content. Hydrogen-bonding and electrostatic interactions of the silanol surfaces of fumed silica aggregates with the extracellular plasma membrane cause membrane perturbations sensed by the Nalp3 inflammasome, whose subsequent activation leads to secretion of the cytokine IL-1β. Hydroxyl radicals generated by the strained 3MRs in fumed silica but largely absent in colloidal silicas may contribute to the inflammasome activation. Formation of colloidal silica into aggregates mimicking those of fumed silica had no effect on cell viability or hemolysis. This study emphasizes that not all amorphous silica is created equal and that the unusual toxicity of fumed silica compared to colloidal silica derives from its framework and surface chemistry along

  3. Fresnel diffraction of aperture with rough edge

    NASA Astrophysics Data System (ADS)

    Cui, Yuwei; Zhang, Wei; Wang, Junhong; Zhang, Meina; Teng, Shuyun

    2015-06-01

    The Fresnel diffraction of an aperture with a rough edge is studied in this paper. Circular and elliptical apertures with sinusoidal and random edges are chosen as examples to investigate the influence of the aperture edge on the diffraction. The numerical calculation results indicate intuitively the variations of the transverse and longitude diffraction intensity distributions with the edge parameters of the aperture. The data files of aperture models are obtained through the numerical calculations, and the aperture samples are obtained with the help of a liquid crystal light modulator (LCLM). Thus, the practical experiments of the diffractions of apertures with rough edges are carried out. The measured results are consistent with the calculated ones. The approximate analytic expressions of the diffraction by the modified aperture are deduced on the basis of the Fresnel diffraction theory and the statistic optics, and the reasonable explanations for the influence of edge parameters on the diffraction are given through the theoretical analysis.

  4. Quantitative evaluation of fiber fuse initiation with exposure to arc discharge provided by a fusion splicer

    NASA Astrophysics Data System (ADS)

    Todoroki, Shin-Ichi

    2016-05-01

    The optical communication industry and power-over-fiber applications face a dilemma as a result of the expanding demand of light power delivery and the potential risks of high-power light manipulation including the fiber fuse phenomenon, a continuous destruction of the fiber core pumped by the propagating light and triggered by a heat-induced strong absorption of silica glass. However, we have limited knowledge on its initiation process in the viewpoint of energy flow in the reactive area. Therefore, the conditions required for a fiber fuse initiation in standard single-mode fibers were determined quantitatively, namely the power of a 1480 nm fiber laser and the arc discharge intensity provided by a fusion splicer for one second as an outer heat source. Systematic investigation on the energy flow balance between these energy sources revealed that the initiation process consists of two steps; the generation of a precursor at the heated spot and the transition to a stable fiber fuse. The latter step needs a certain degree of heat accumulation at the core where waveguide deformation is ongoing competitively. This method is useful for comparing the tolerance to fiber fuse initiation among various fibers with a fixed energy amount that was not noticed before.

  5. Quantitative evaluation of fiber fuse initiation with exposure to arc discharge provided by a fusion splicer.

    PubMed

    Todoroki, Shin-Ichi

    2016-01-01

    The optical communication industry and power-over-fiber applications face a dilemma as a result of the expanding demand of light power delivery and the potential risks of high-power light manipulation including the fiber fuse phenomenon, a continuous destruction of the fiber core pumped by the propagating light and triggered by a heat-induced strong absorption of silica glass. However, we have limited knowledge on its initiation process in the viewpoint of energy flow in the reactive area. Therefore, the conditions required for a fiber fuse initiation in standard single-mode fibers were determined quantitatively, namely the power of a 1480 nm fiber laser and the arc discharge intensity provided by a fusion splicer for one second as an outer heat source. Systematic investigation on the energy flow balance between these energy sources revealed that the initiation process consists of two steps; the generation of a precursor at the heated spot and the transition to a stable fiber fuse. The latter step needs a certain degree of heat accumulation at the core where waveguide deformation is ongoing competitively. This method is useful for comparing the tolerance to fiber fuse initiation among various fibers with a fixed energy amount that was not noticed before. PMID:27140935

  6. Quantitative evaluation of fiber fuse initiation with exposure to arc discharge provided by a fusion splicer

    PubMed Central

    Todoroki, Shin-ichi

    2016-01-01

    The optical communication industry and power-over-fiber applications face a dilemma as a result of the expanding demand of light power delivery and the potential risks of high-power light manipulation including the fiber fuse phenomenon, a continuous destruction of the fiber core pumped by the propagating light and triggered by a heat-induced strong absorption of silica glass. However, we have limited knowledge on its initiation process in the viewpoint of energy flow in the reactive area. Therefore, the conditions required for a fiber fuse initiation in standard single-mode fibers were determined quantitatively, namely the power of a 1480 nm fiber laser and the arc discharge intensity provided by a fusion splicer for one second as an outer heat source. Systematic investigation on the energy flow balance between these energy sources revealed that the initiation process consists of two steps; the generation of a precursor at the heated spot and the transition to a stable fiber fuse. The latter step needs a certain degree of heat accumulation at the core where waveguide deformation is ongoing competitively. This method is useful for comparing the tolerance to fiber fuse initiation among various fibers with a fixed energy amount that was not noticed before. PMID:27140935

  7. Alternative aperture stop position designs for SIRTF

    NASA Technical Reports Server (NTRS)

    Davis, Paul K.; Dinger, Ann S.

    1990-01-01

    Three designs of the Space Infrared Telescope Facility (SIRTF) for a 100,000 high earth orbit are considered with particular attention given to the evaluation of the aperture stop position. The choice of aperture stop position will be based on stray light considerations which are being studied concurrently. It is noted that there are advantages in cost, mass, and astronomical aperture to placing the aperture stop at or near the primary mirror, if the stray light circumstances allow.

  8. Fused Bead Analysis of Diogenite Meteorites

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D.W.; Beck, B.W.; McSween, H.Y.; Lee, C.T. A.

    2009-01-01

    Bulk rock chemistry is an essential dataset in meteoritics and planetary science [1]. A common method used to obtain the bulk chemistry of meteorites is ICP-MS. While the accuracy, precision and low detection limits of this process are advantageous [2], the sample size used for analysis (approx.70 mg) can be a problem in a field where small and finite samples are the norm. Fused bead analysis is another bulk rock analytical technique that has been used in meteoritics [3]. This technique involves forming a glass bead from 10 mg of sample and measuring its chemistry using a defocused beam on a microprobe. Though the ICP-MS has lower detection limits than the microprobe, the fused bead method destroys a much smaller sample of the meteorite. Fused bead analysis was initially designed for samples with near-eutectic compositions and low viscosities. Melts generated of this type homogenize at relatively low temperatures and produce primary melts near the sample s bulk composition [3]. The application of fused bead analysis to samples with noneutectic melt compositions has not been validated. The purpose of this study is to test if fused bead analysis can accurately determine the bulk rock chemistry of non-eutectic melt composition meteorites. To determine this, we conduct two examinations of the fused bead. First, we compare ICP-MS and fused bead results of the same samples using statistical analysis. Secondly, we inspect the beads for the presence of crystals and chemical heterogeneity. The presence of either of these would indicate incomplete melting and quenching of the bead.

  9. Provocation Lumbar Diskography at Previously Fused Levels

    PubMed Central

    Dulai, H.S.; Bartynski, W.S.; Rothfus, W.S.; Gerszten, P.C.

    2010-01-01

    Summary Recurrent or persistent low back pain (LBP) after lumbar fusion can be related to many factors. We reviewed the provocation lumbar diskogram (PLD) features and redo-fusion outcome in our patients evaluated for recurrent/persistent LBP after technically successful fusion. LD was performed in 27 patients with recurrent/persistent LBP after prior successful lumbar surgical fusion (31 fused levels: single-level fusion-23; two-level fusion-4). PLD response and imaging characteristics at fused and non-fused levels were assessed including: intra-diskal lidocaine response, diskogram-image/post-diskogram CT appearance, presence/absence of diskographic contrast leakage, and evidence of fusion integrity or hardware failure. Outcomes in patients having redo-fusion were assessed. Concordant pain was encountered at 15 out of 23 (65%) single-level fusions, non-concordant pain in one fusion with non-painful response in seven. Adjacent-level concordant pain was identified in seven out of 23 (30%) patients (three of 15 with painful fused levels; four of seven with non-painful fusions). In two-level fusions, concordant pain was encountered at one fused level in each patient. In painful fused levels, leaking and contained disks were encountered with partial or complete pain elimination after intra-diskal lidocaine injection. In anterior fusions, space or contrast surrounding the cage was noted at five of 11 levels. Pseudoarthrosis was noted only with trans-sacral screw fusions. Redo-fusion in 13 patients resulted in significant improvement in nine and moderate improvement in one. Patients with recurrent/persistent LBP after technically successful fusion may have a diskogenic pain source at the surgically fused or adjacent level confirmed by lidocaine-assisted PLD. PMID:20977869

  10. Light bullets and supercontinuum spectrum during femtosecond pulse filamentation under conditions of anomalous group-velocity dispersion in fused silicalicati

    SciTech Connect

    Chekalin, Sergei V; Kompanets, V O; Smetanina, E O; Kandidov, V P

    2013-04-30

    We report the results of theoretical and experimental research on spectrum transformation and spatiotemporal distribution of the femtosecond laser radiation intensity during filamentation in fused silica. The formation of light bullets with a high power density is first observed in a femtosecond laser pulse in the anomalous group velocity dispersion regime at a wavelength of 1800 nm. The minimum duration of the light bullet is about two oscillation cycles of the light field. (extreme light fields and their applications)

  11. VSATs - Very small aperture terminals

    NASA Astrophysics Data System (ADS)

    Everett, John L.

    The present volume on very small aperture terminals (VSATs) discusses antennas, semiconductor devices, and traveling wave tubes and amplifiers for VSAT systems, VSAT low noise downconverters, and modems and codecs for VSAT systems. Attention is given to multiaccess protocols for VSAT networks, protocol software in Ku-band VSAT network systems, system design of VSAT data networks, and the policing of VSAT networks. Topics addressed include the PANDATA and PolyCom systems, APOLLO - a satellite-based information distribution system, data broadcasting within a satellite television channel, and the NEC NEXTAR VSAT system. Also discussed are small aperture military ground terminals, link budgets for VSAT systems, capabilities and experience of a VSAT service provider, and developments in VSAT regulation.

  12. Broadband synthetic aperture geoacoustic inversion.

    PubMed

    Tan, Bien Aik; Gerstoft, Peter; Yardim, Caglar; Hodgkiss, William S

    2013-07-01

    A typical geoacoustic inversion procedure involves powerful source transmissions received on a large-aperture receiver array. A more practical approach is to use a single moving source and/or receiver in a low signal to noise ratio (SNR) setting. This paper uses single-receiver, broadband, frequency coherent matched-field inversion and exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time creates a synthetic aperture due to relative source-receiver motion. This approach is illustrated by studying the transmission of multiple linear frequency modulated (LFM) pulses which results in a multi-tonal comb spectrum that is Doppler sensitive. To correlate well with the measured field across a receiver trajectory and to incorporate transmission from a source trajectory, waveguide Doppler and normal mode theory is applied. The method is demonstrated with low SNR, 100-900 Hz LFM pulse data from the Shallow Water 2006 experiment. PMID:23862809

  13. Large aperture scanning airborne lidar

    NASA Technical Reports Server (NTRS)

    Smith, J.; Bindschadler, R.; Boers, R.; Bufton, J. L.; Clem, D.; Garvin, J.; Melfi, S. H.

    1988-01-01

    A large aperture scanning airborne lidar facility is being developed to provide important new capabilities for airborne lidar sensor systems. The proposed scanning mechanism allows for a large aperture telescope (25 in. diameter) in front of an elliptical flat (25 x 36 in.) turning mirror positioned at a 45 degree angle with respect to the telescope optical axis. The lidar scanning capability will provide opportunities for acquiring new data sets for atmospheric, earth resources, and oceans communities. This completed facility will also make available the opportunity to acquire simulated EOS lidar data on a near global basis. The design and construction of this unique scanning mechanism presents exciting technological challenges of maintaining the turning mirror optical flatness during scanning while exposed to extreme temperatures, ambient pressures, aircraft vibrations, etc.

  14. Aperture masking behind AO systems

    NASA Astrophysics Data System (ADS)

    Ireland, Michael J.

    2012-07-01

    Sparse Aperture-Mask Interferometry (SAM or NRM) behind Adaptive Optics (AO) has now come of age, with more than a dozen astronomy papers published from several 5-10m class telescopes around the world. I will describe the reasons behind its success in achieving relatively high contrasts ( 1000:1 at lambda/ D) and repeatable binary astronomy at the diffraction limit, even when used behind laser-guide star adaptive optics. Placed within the context of AO calibration, the information in an image can be split into pupil-plane phase, Fourier amplitude and closure-phase. It is the closure-phase observable, or its generalisation to Kernel phase, that is immune to pupil-plane phase errors at first and second-order and has been the reason for the technique's success. I will outline the limitations of the technique and the prospects for aperture-masking and related techniques in the future.

  15. Wafer-fused semiconductor radiation detector

    DOEpatents

    Lee, Edwin Y.; James, Ralph B.

    2002-01-01

    Wafer-fused semiconductor radiation detector useful for gamma-ray and x-ray spectrometers and imaging systems. The detector is fabricated using wafer fusion to insert an electrically conductive grid, typically comprising a metal, between two solid semiconductor pieces, one having a cathode (negative electrode) and the other having an anode (positive electrode). The wafer fused semiconductor radiation detector functions like the commonly used Frisch grid radiation detector, in which an electrically conductive grid is inserted in high vacuum between the cathode and the anode. The wafer-fused semiconductor radiation detector can be fabricated using the same or two different semiconductor materials of different sizes and of the same or different thicknesses; and it may utilize a wide range of metals, or other electrically conducting materials, to form the grid, to optimize the detector performance, without being constrained by structural dissimilarity of the individual parts. The wafer-fused detector is basically formed, for example, by etching spaced grooves across one end of one of two pieces of semiconductor materials, partially filling the grooves with a selected electrical conductor which forms a grid electrode, and then fusing the grooved end of the one semiconductor piece to an end of the other semiconductor piece with a cathode and an anode being formed on opposite ends of the semiconductor pieces.

  16. Multiple aperture imager component development

    NASA Astrophysics Data System (ADS)

    Lees, David E.; Henshaw, Philip D.

    1991-03-01

    This final report presents results of an experimental and analytical effort to develop multiple aperture imagers built from unphased, direct-detection subapertures. An object was imaged using wave length shift instead of object motion to create multiple speckle pattern realizations. An analysis of subaperture geometry effects of autocorrelation estimate was performed. Experimental measurements of detector modulator transfer function were made. Finally, a new algorithm to reconstruct imagery with improved signal-to-noise ratio was developed.

  17. Coherent sub-aperture ultraviolet imagery

    NASA Astrophysics Data System (ADS)

    Morton, R. G.; Connally, W. J.; Avicola, K.; Monjo, D.; Olson, T.

    1989-09-01

    Laboratory targets have been imaged by a multi-sub-aperture, coherent receiver technique in which a common local oscillator illuminates the sub-aperture array to preserve both phase and intensity information. The target, receiver and range dimensions were chosen such that each sub-aperture was smaller than the speckle size. Various targets were illuminated by microsecond pulses from an e-beam pumped XeF power amplifier, which was seeded by a coherent ultraviolet beam generated with a frequency doubled visible dye laser. Data is presented showing comparisons between the coherent multi-sub-aperture approach and conventional, full aperture photography of the same traget(s).

  18. Propagation mechanism of polymer optical fiber fuse

    PubMed Central

    Mizuno, Yosuke; Hayashi, Neisei; Tanaka, Hiroki; Nakamura, Kentaro; Todoroki, Shin-ichi

    2014-01-01

    A fiber fuse phenomenon in polymer optical fibers (POFs) has recently been observed, and its unique properties such as slow propagation, low threshold power density, and the formation of a black oscillatory damage curve, have been reported. However, its characterization is still insufficient to well understand the mechanism and to avoid the destruction of POFs. Here, we present detailed experimental and theoretical analyses of the POF fuse propagation. First, we clarify that the bright spot is not a plasma but an optical discharge, the temperature of which is ~3600 K. We then elucidate the reasons for the oscillation of the damage curve along with the formation of newly-observed gas bubbles as well as for the low threshold power density. We also present the idea that the POF fuse can potentially be exploited to offer a long photoelectric interaction length. PMID:24762949

  19. Stability of fuses under cyclic load

    NASA Astrophysics Data System (ADS)

    Namitokov, K. K.; Shklovskiy, I. G.

    1984-05-01

    Thermal stresses in fuses, stimulated by the high degree of mechanical stiffness and the cause of low stability under cyclic current loads, can be reduced by reducing the stiffness of the fuse element, which is typically a strap welded to contact caps at both ends. It is indicated that the stiffness can be reduced by increasing the length and decreasing the cross section. A thin strap consists of flat and bend segments. Simple bending and multiple bending were evaluated. It is indicated that bent fuse segments are less stiff than straight segments, that the relation between stiffness and amplitude of the bend is an inverse power law with the amplitude to a power much higher than squared, that the decrease of overall stiffness is approximately proportional to the number of bends, and that rectangular or circular bending reduce the stiffness most efficiently, inasmuch as such contours envelop the largest areas on the basis of fixed length.

  20. Controlled-aperture wave-equation migration

    SciTech Connect

    Huang, L.; Fehler, Michael C.; Sun, H.; Li, Z.

    2003-01-01

    We present a controlled-aperture wave-equation migration method that no1 only can reduce migration artiracts due to limited recording aperlurcs and determine image weights to balance the efl'ects of limited-aperture illumination, but also can improve thc migration accuracy by reducing the slowness perturbations within thc controlled migration regions. The method consists of two steps: migration aperture scan and controlled-aperture migration. Migration apertures for a sparse distribution of shots arc determined using wave-equation migration, and those for the other shots are obtained by interpolation. During the final controlled-aperture niigration step, we can select a reference slowness in c;ontrollecl regions of the slowness model to reduce slowncss perturbations, and consequently increase the accuracy of wave-equation migration inel hods that makc use of reference slownesses. In addition, the computation in the space domain during wavefield downward continuation is needed to be conducted only within the controlled apertures and therefore, the computational cost of controlled-aperture migration step (without including migration aperture scan) is less than the corresponding uncontrolled-aperture migration. Finally, we can use the efficient split-step Fourier approach for migration-aperture scan, then use other, more accurate though more expensive, wave-equation migration methods to perform thc final controlled-apertio.ee migration to produce the most accurate image.

  1. High-purity silica reflecting heat shield development

    NASA Technical Reports Server (NTRS)

    Congdon, W. M.

    1974-01-01

    A high-purity, fused-silica reflecting heat shield for the thermal protection of outer-planet probes was developed. Factors that strongly influence the performance of a silica heat shield were studied. Silica-bonded silica configurations, each prepared by a different technique, were investigated and rated according to its relative merits. Slip-casting was selected as the preferred fabrication method because it produced good reflectivity and good strength, and is relatively easy to scale up for a full-size outer-planet probe. The slips were cast using a variety of different particle sizes: continuous particle-size slips; monodisperse particle-size slips; and blends of monodisperse particle-size slips were studied. In general, smaller particles gave the highest reflectance. The monodisperse slips as well as the blend slips gave a higher reflectance than the continuous particle-size slips. An upgraded and fused natural quartz was used to study the effects of microstructure on reflectance and as the baseline to ascertain the increase in reflectance obtained from using a higher-purity synthetic material.

  2. Silica-alumina trihydrate filled epoxy castings resistant to arced SF.sub.6

    DOEpatents

    Chenoweth, Terrence E.; Yeoman, Frederick A.

    1978-01-01

    A cured, insulating, casting composition, having a coefficient of linear thermal expansion of below about 38 .times. 10.sup.-6 in./in./.degree. C and being resistant to arced sulfur hexafluoride gas, in contact with a metal surface in a sulfur hexafluoride gas environment, is made from hydantoin epoxy resin, anhydride curing agent and a filler combination of fused silica and alumina trihydrate.

  3. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  4. Crystal growth in fused solvent systems

    NASA Technical Reports Server (NTRS)

    Ulrich, D. R.; Noone, M. J.; Spear, K. E.; White, W. B.; Henry, E. C.

    1973-01-01

    Research is reported on the growth of electronic ceramic single crystals from solution for the future growth of crystals in a microgravity environment. Work included growth from fused or glass solvents and aqueous solutions. Topics discussed include: crystal identification and selection; aqueous solution growth of triglycine sulphate (TGS); and characterization of TGS.

  5. Fusing face-verification algorithms and humans.

    PubMed

    O'Toole, Alice J; Abdi, Hervé; Jiang, Fang; Phillips, P Jonathon

    2007-10-01

    It has been demonstrated recently that state-of-the-art face-recognition algorithms can surpass human accuracy at matching faces over changes in illumination. The ranking of algorithms and humans by accuracy, however, does not provide information about whether algorithms and humans perform the task comparably or whether algorithms and humans can be fused to improve performance. In this paper, we fused humans and algorithms using partial least square regression (PLSR). In the first experiment, we applied PLSR to face-pair similarity scores generated by seven algorithms participating in the Face Recognition Grand Challenge. The PLSR produced an optimal weighting of the similarity scores, which we tested for generality with a jackknife procedure. Fusing the algorithms' similarity scores using the optimal weights produced a twofold reduction of error rate over the most accurate algorithm. Next, human-subject-generated similarity scores were added to the PLSR analysis. Fusing humans and algorithms increased the performance to near-perfect classification accuracy. These results are discussed in terms of maximizing face-verification accuracy with hybrid systems consisting of multiple algorithms and humans. PMID:17926698

  6. 30 CFR 56.6502 - Safety fuse.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Safety fuse. 56.6502 Section 56.6502 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Nonelectric Blasting §...

  7. 30 CFR 57.6502 - Safety fuse.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Safety fuse. 57.6502 Section 57.6502 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Nonelectric...

  8. 30 CFR 57.6502 - Safety fuse.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Safety fuse. 57.6502 Section 57.6502 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Nonelectric...

  9. 30 CFR 56.6502 - Safety fuse.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Safety fuse. 56.6502 Section 56.6502 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Nonelectric Blasting §...

  10. 30 CFR 57.6502 - Safety fuse.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... least the minimum burning time for a particular size round, as specified in the following table: Table E... blasthole detonates. (d) Fuse shall be cut and capped in dry locations. (e) Blasting caps shall be crimped... with devices designed for that purpose. Carbide lights, liquefied petroleum gas torches, and...

  11. 30 CFR 57.6502 - Safety fuse.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... least the minimum burning time for a particular size round, as specified in the following table: Table E... blasthole detonates. (d) Fuse shall be cut and capped in dry locations. (e) Blasting caps shall be crimped... with devices designed for that purpose. Carbide lights, liquefied petroleum gas torches, and...

  12. 30 CFR 56.6502 - Safety fuse.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... a particular size round, as specified in the following table: Table E-1—Safety Fuse—Minimum Burning... be cut and capped in dry locations. (e) Blasting caps shall be crimped to fuse only with implements... purpose. Carbide lights, liquefied petroleum gas torches, and cigarette lighters shall not be used...

  13. 30 CFR 56.6502 - Safety fuse.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... a particular size round, as specified in the following table: Table E-1—Safety Fuse—Minimum Burning... be cut and capped in dry locations. (e) Blasting caps shall be crimped to fuse only with implements... purpose. Carbide lights, liquefied petroleum gas torches, and cigarette lighters shall not be used...

  14. 30 CFR 57.6502 - Safety fuse.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... least the minimum burning time for a particular size round, as specified in the following table: Table E... blasthole detonates. (d) Fuse shall be cut and capped in dry locations. (e) Blasting caps shall be crimped... with devices designed for that purpose. Carbide lights, liquefied petroleum gas torches, and...

  15. 30 CFR 56.6502 - Safety fuse.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... a particular size round, as specified in the following table: Table E-1—Safety Fuse—Minimum Burning... be cut and capped in dry locations. (e) Blasting caps shall be crimped to fuse only with implements... purpose. Carbide lights, liquefied petroleum gas torches, and cigarette lighters shall not be used...

  16. Silazane to silica

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1992-01-01

    Thin film silica and/or methyl silicone were detected on most external surfaces of the retrieved LDEF. Known sources of silicone in or on the LDEF appear inadequate to explain the ubiquitous presence of the silica and silicone films. Hexamethyldisilazane (HMDS) was used as the Challenger tile waterproofing compound for the Challenger/LDEF deployment mission. HMDS releases NH3 which depolymerizes silicone RTV's. Polyurethanes were also attacked. Much of the silica/silicone contamination of LDEF resulted from HMDS.

  17. Reconstruction of coded aperture images

    NASA Technical Reports Server (NTRS)

    Bielefeld, Michael J.; Yin, Lo I.

    1987-01-01

    Balanced correlation method and the Maximum Entropy Method (MEM) were implemented to reconstruct a laboratory X-ray source as imaged by a Uniformly Redundant Array (URA) system. Although the MEM method has advantages over the balanced correlation method, it is computationally time consuming because of the iterative nature of its solution. Massively Parallel Processing, with its parallel array structure is ideally suited for such computations. These preliminary results indicate that it is possible to use the MEM method in future coded-aperture experiments with the help of the MPP.

  18. Aperture scanning Fourier ptychographic microscopy

    PubMed Central

    Ou, Xiaoze; Chung, Jaebum; Horstmeyer, Roarke; Yang, Changhuei

    2016-01-01

    Fourier ptychographic microscopy (FPM) is implemented through aperture scanning by an LCOS spatial light modulator at the back focal plane of the objective lens. This FPM configuration enables the capturing of the complex scattered field for a 3D sample both in the transmissive mode and the reflective mode. We further show that by combining with the compressive sensing theory, the reconstructed 2D complex scattered field can be used to recover the 3D sample scattering density. This implementation expands the scope of application for FPM and can be beneficial for areas such as tissue imaging and wafer inspection. PMID:27570705

  19. TELESCOPES: Astronomers Overcome 'Aperture Envy'.

    PubMed

    Irion, R

    2000-07-01

    Many users of small telescopes are disturbed by the trend of shutting down smaller instruments in order to help fund bigger and bolder ground-based telescopes. Small telescopes can thrive in the shadow of giant new observatories, they say--but only if they are adapted to specialized projects. Telescopes with apertures of 2 meters or less have unique abilities to monitor broad swaths of the sky and stare at the same objects night after night, sometimes for years; various teams are turning small telescopes into robots, creating networks that span the globe and devoting them to survey projects that big telescopes don't have a prayer of tackling. PMID:17832960

  20. Dual aperture multispectral Schmidt objective

    NASA Technical Reports Server (NTRS)

    Minott, P. O. (Inventor)

    1984-01-01

    A dual aperture, off-axis catadioptic Schmidt objective is described. It is formed by symmetrically aligning two pairs of Schmidt objectives on opposite sides of a common plane (x,z). Each objective has a spherical primary mirror with a spherical focal plane and center of curvature aligned along an optic axis laterally spaced apart from the common plane. A multiprism beamsplitter with buried dichroic layers and a convex entrance and concave exit surfaces optically concentric to the center of curvature may be positioned at the focal plane. The primary mirrors of each objective may be connected rigidly together and may have equal or unequal focal lengths.

  1. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  2. Tuning the mechanical properties of silica microcapsules.

    PubMed

    Zhang, Lijuan; D'Acunzi, Maria; Kappl, Michael; Imhof, Arnout; van Blaaderen, Alfons; Butt, Hans-Jürgen; Graf, Robert; Vollmer, Doris

    2010-12-21

    Heat treatment is a standard method to increase the hardness of silica in various applications. Here, we tested the effect of high temperature annealing on the mechanical properties of silica microcapsules by force spectroscopy under point loads applied to the particle shell. The Young's modulus of the shells moderately increases after annealing at temperatures above 500 °C. Temperatures over 850 °C result in a much stronger increase and the Young's modulus is close to that of fused silica after annealing at 1100 °C. NMR analysis revealed that in untreated microcapsules synthesized by seeded growth using the Stöber method only 55% of the silicon atoms form siloxane bonds with four neighbors, whereas the remaining ones only form three or less siloxane bonds each and, thus, a large number of ethoxy and silanol groups still exist. During annealing at 500 °C, these are successively transformed into siloxane bonds through condensation reactions. This process correlates with only a moderate increase in Young's modulus. The strong increase at temperatures above 850 °C was associated with a densification which was associated by a decrease in capsule size and shell thickness while the shells remained homogenous and of spherical shape. The main strengthening of the shells is thus mainly due to compaction by sintering at length scales significantly larger than that of local siloxane bonds. PMID:20963236

  3. Silazine to silica

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1993-01-01

    Thin film silica and/or methyl silicone were detected on most external surfaces of the retrieved LDEF. Both solar ultraviolet radiation and atomic oxygen can convert silicones to silica. Known sources of silicone in or on the LDEF appear inadequate to explain the ubiquitous presence of the silica and silicone films. Hexamethyldisilazane (HMDS) was used as the Challenger tile waterproofing compound for the Challenger/LDEF deployment mission. HMDS is both volatile and chemically reactive at STP. In addition, HMDS releases NH3 which depolymerizes silicone RTV's. Polyurethanes are also depolymerized. Experiments are reported that indicate much of the silicone and silica contamination of LDEF resulted directly or indirectly from HMDS.

  4. Resonant Effects in Nanoscale Bowtie Apertures

    NASA Astrophysics Data System (ADS)

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-06-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing.

  5. DAVINCI a Dilute Aperture Coronagraph

    NASA Astrophysics Data System (ADS)

    Shao, Michael

    2009-01-01

    The motivation for DAVINCI was originally to make use of the technology developed for space interferometers like SIM to build a coronagraph from four 1.1m telescopes that was dramatically lower in cost than a 4 5m filled aperture offaxis coronagraph. Our initial studies through team X have shown this cost savings to be real. But a more careful analysis showed that DAVINCI would have an inner working angle of 35mas a factor of 2 smaller than a 2 lambda/D 4 meter coronagraph or 70m external occulter, resulting in a 10X increase in the number of potential Earth-Clone targets. DAVINCI uses a nulling interferometer as a coronagraph, a nulling interferometer is one the few coronagraph architectures that are compatible with segmented and dilute aperture telescopes. Combined with a post coronagraph wavefront sensor several ultra-demanding tolerances of conventional coronagraphs can be relaxed by factors of 100. The post coronagraph wavefront sensor is also much less affected by local and exozodi background than wavefront sensors that use the science camera as the wavefront sensor. The post coronagraph interferometer is also used on ground based extreme AO coronagraphs, GPI, and P1640.

  6. Synthetic aperture sonar image statistics

    NASA Astrophysics Data System (ADS)

    Johnson, Shawn F.

    Synthetic Aperture Sonar (SAS) systems are capable of producing photograph quality seafloor imagery using a lower frequency than other systems of comparable resolution. However, as with other high-resolution sonar systems, SAS imagery is often characterized by heavy-tailed amplitude distributions which may adversely affect target detection systems. The constant cross-range resolution with respect to range that results from the synthetic aperture formation process provides a unique opportunity to improve our understanding of system and environment interactions, which is essential for accurate performance prediction. This research focused on the impact of multipath contamination and the impact of resolution on image statistics, accomplished through analyses of data collected during at-sea experiments, analytical modeling, and development of numerical simulations. Multipath contamination was shown to have an appreciable impact on image statistics at ranges greater than the water depth and when the levels of the contributing multipath are within 10 dB of the direct path, reducing the image amplitude distribution tails while also degrading image clarity. Image statistics were shown to depend strongly upon both system resolution and orientation to seafloor features such as sand ripples. This work contributes to improving detection systems by aiding understanding of the influences of background (i.e. non-target) image statistics.

  7. Diffraction smoothing aperture for an optical beam

    DOEpatents

    Judd, O'Dean P.; Suydam, Bergen R.

    1976-01-01

    The disclosure is directed to an aperture for an optical beam having an irregular periphery or having perturbations imposed upon the periphery to decrease the diffraction effect caused by the beam passing through the aperture. Such apertures are particularly useful with high power solid state laser systems in that they minimize the problem of self-focusing which frequently destroys expensive components in such systems.

  8. Ion mobility spectrometer with virtual aperture grid

    DOEpatents

    Pfeifer, Kent B.; Rumpf, Arthur N.

    2010-11-23

    An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

  9. 30 CFR 18.52 - Renewal of fuses.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements...-circuit, and handheld-tool fuses, shall be interlocked with a circuit-interrupting device. Fuses shall...

  10. 30 CFR 18.52 - Renewal of fuses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements...-circuit, and handheld-tool fuses, shall be interlocked with a circuit-interrupting device. Fuses shall...

  11. 30 CFR 18.52 - Renewal of fuses.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements...-circuit, and handheld-tool fuses, shall be interlocked with a circuit-interrupting device. Fuses shall...

  12. 30 CFR 18.52 - Renewal of fuses.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements...-circuit, and handheld-tool fuses, shall be interlocked with a circuit-interrupting device. Fuses shall...

  13. 49 CFR 173.184 - Highway or rail fusee.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... consecutive hours. (b) Fusees (highway and railway) must be packaged in steel drums (1A2), steel jerricans...), plywood (1D) or fiber (1G) drums. If the fusees are equipped with spikes packagings must have...

  14. 49 CFR 173.184 - Highway or rail fusee.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... consecutive hours. (b) Fusees (highway and railway) must be packaged in steel drums (1A2), steel jerricans...), plywood (1D) or fiber (1G) drums. If the fusees are equipped with spikes packagings must have...

  15. An electron-conducting pyrene-fused phenazinothiadiazole.

    PubMed

    Marco, A Belen; Cortizo-Lacalle, Diego; Gozalvez, Cristian; Olano, Mikel; Atxabal, Ainhoa; Sun, Xiangnan; Melle-Franco, Manuel; Hueso, Luis E; Mateo-Alonso, Aurelio

    2015-07-01

    A pyrene-fused phenazinothiadiazole that shows electron mobilities (μe = 0.016 cm(2) V(-1) s(-1)) two orders of magnitude higher than those reported for pyrene-fused pyrazaacenes is described. PMID:26051680

  16. Retrograde intrarenal surgery in cross-fused ectopic kidney.

    PubMed

    Resorlu, Mustafa; Kabar, Mucahit; Resorlu, Berkan; Doluoglu, Omer Gokhan; Kilinc, Muhammet Fatih; Karakan, Tolga

    2015-02-01

    Cross-fused renal ectopia is a rare congenital anomaly in which both kidneys are fused and located on the same side. We report a case of right-to-left cross-fused renal ectopia and nephrolithiasis, in whom retrograde intrarenal surgery was used to treat the stone disease. To our knowledge, this is the first case of retrograde intrarenal surgery of a crossed-fused ectopic kidney. PMID:25481231

  17. Control of silicification by genetically engineered fusion proteins: Silk–silica binding peptides

    PubMed Central

    Zhou, Shun; Huang, Wenwen; Belton, David J.; Simmons, Leo O.; Perry, Carole C.; Wang, Xiaoqin; Kaplan, David L.

    2014-01-01

    In the present study, an artificial spider silk gene, 6mer, derived from the consensus sequence of Nephila clavipes dragline silk gene, was fused with different silica-binding peptides (SiBPs), A1, A3 and R5, to study the impact of the fusion protein sequence chemistry on silica formation and the ability to generate a silk–silica composite in two different bioinspired silicification systems: solution–solution and solution– solid. Condensed silica nanoscale particles (600–800 nm) were formed in the presence of the recombinant silk and chimeras, which were smaller than those formed by 15mer-SiBP chimeras [1], revealing that the molecular weight of the silk domain correlated to the sizes of the condensed silica particles in the solution system. In addition, the chimeras (6mer-A1/A3/R5) produced smaller condensed silica particles than the control (6mer), revealing that the silica particle size formed in the solution system is controlled by the size of protein assemblies in solution. In the solution–solid interface system, silicification reactions were performed on the surface of films fabricated from the recombinant silk proteins and chimeras and then treated to induce β-sheet formation. A higher density of condensed silica formed on the films containing the lowest β-sheet content while the films with the highest β-sheet content precipitated the lowest density of silica, revealing an inverse correlation between the β-sheet secondary structure and the silica content formed on the films. Intriguingly, the 6mer-A3 showed the highest rate of silica condensation but the lowest density of silica deposition on the films, compared with 6mer-A1 and -R5, revealing antagonistic crosstalk between the silk and the SiBP domains in terms of protein assembly. These findings offer a path forward in the tailoring of biopolymer–silica composites for biomaterial related needs. PMID:25462851

  18. Control of silicification by genetically engineered fusion proteins: silk-silica binding peptides.

    PubMed

    Zhou, Shun; Huang, Wenwen; Belton, David J; Simmons, Leo O; Perry, Carole C; Wang, Xiaoqin; Kaplan, David L

    2015-03-01

    In the present study, an artificial spider silk gene, 6mer, derived from the consensus sequence of Nephila clavipes dragline silk gene, was fused with different silica-binding peptides (SiBPs), A1, A3 and R5, to study the impact of the fusion protein sequence chemistry on silica formation and the ability to generate a silk-silica composite in two different bioinspired silicification systems: solution-solution and solution-solid. Condensed silica nanoscale particles (600-800 nm) were formed in the presence of the recombinant silk and chimeras, which were smaller than those formed by 15mer-SiBP chimeras, revealing that the molecular weight of the silk domain correlated to the sizes of the condensed silica particles in the solution system. In addition, the chimeras (6mer-A1/A3/R5) produced smaller condensed silica particles than the control (6mer), revealing that the silica particle size formed in the solution system is controlled by the size of protein assemblies in solution. In the solution-solid interface system, silicification reactions were performed on the surface of films fabricated from the recombinant silk proteins and chimeras and then treated to induce β-sheet formation. A higher density of condensed silica formed on the films containing the lowest β-sheet content while the films with the highest β-sheet content precipitated the lowest density of silica, revealing an inverse correlation between the β-sheet secondary structure and the silica content formed on the films. Intriguingly, the 6mer-A3 showed the highest rate of silica condensation but the lowest density of silica deposition on the films, compared with 6mer-A1 and -R5, revealing antagonistic crosstalk between the silk and the SiBP domains in terms of protein assembly. These findings offer a path forward in the tailoring of biopolymer-silica composites for biomaterial related needs. PMID:25462851

  19. Silica, Silicosis, and Autoimmunity

    PubMed Central

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  20. Silica, Silicosis, and Autoimmunity.

    PubMed

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  1. 30 CFR 57.12036 - Fuse removal or replacement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Fuse removal or replacement. 57.12036 Section 57.12036 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Electricity Surface and Underground § 57.12036 Fuse removal or replacement. Fuses shall not be removed...

  2. 30 CFR 57.12036 - Fuse removal or replacement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Fuse removal or replacement. 57.12036 Section 57.12036 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Electricity Surface and Underground § 57.12036 Fuse removal or replacement. Fuses shall not be removed...

  3. Interactions of spatial solitons with fused couplers

    NASA Astrophysics Data System (ADS)

    Harel, Alon; Malomed, Boris A.

    2014-04-01

    We study dynamical and stationary states of solitons in dual-core waveguides which are locally coupled (fused) at one or several short segments. The model applies to planar optical waveguides, and to Bose-Einstein condensate in dual traps. Collisions of an incident soliton with single and double locally fused couplers are investigated by means of systematic simulations and several analytical methods (quasilinear, fast-soliton, and adiabatic approximations). Excitation dynamics of a soliton trapped by a local coupler is studied by means of the variational approximation, and verified by simulations. Shuttle motion of a soliton trapped in a cavity between two local couplers, and in a finite array of couplers, is studied too.

  4. Fused methods for visual saliency estimation

    NASA Astrophysics Data System (ADS)

    Danko, Amanda S.; Lyu, Siwei

    2015-02-01

    In this work, we present a new model of visual saliency by combing results from existing methods, improving upon their performance and accuracy. By fusing pre-attentive and context-aware methods, we highlight the abilities of state-of-the-art models while compensating for their deficiencies. We put this theory to the test in a series of experiments, comparatively evaluating the visual saliency maps and employing them for content-based image retrieval and thumbnail generation. We find that on average our model yields definitive improvements upon recall and f-measure metrics with comparable precisions. In addition, we find that all image searches using our fused method return more correct images and additionally rank them higher than the searches using the original methods alone.

  5. Multimodal Plasmonics in Fused Colloidal Networks

    PubMed Central

    Teulle, Alexandre; Bosman, Michel; Girard, Christian; Gurunatha, Kargal L.; Li, Mei; Mann, Stephen; Dujardin, Erik

    2014-01-01

    Harnessing the optical properties of noble metals down to the nanometer-scale is a key step towards fast and low-dissipative information processing. At the 10-nm length scale, metal crystallinity and patterning as well as probing of surface plasmon (SP) properties must be controlled with a challenging high level of precision. Here, we demonstrate that ultimate lateral confinement and delocalization of SP modes are simultaneously achieved in extended self-assembled networks comprising linear chains of partially fused gold nanoparticles. The spectral and spatial distributions of the SP modes associated with the colloidal superstructures are evidenced by performing monochromated electron energy loss spectroscopy with a nanometer-sized electron probe. We prepare the metallic bead strings by electron beam-induced interparticle fusion of nanoparticle networks. The fused superstructures retain the native morphology and crystallinity but develop very low energy SP modes that are capable of supporting long range and spectrally tunable propagation in nanoscale waveguides. PMID:25344783

  6. Multifocal interferometric synthetic aperture microscopy

    PubMed Central

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G.; Boppart, Stephen A.; Scott Carney, P.

    2014-01-01

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  7. Multifocal interferometric synthetic aperture microscopy.

    PubMed

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G; Boppart, Stephen A; Carney, P Scott

    2014-06-30

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  8. Large aperture Fresnel telescopes/011

    SciTech Connect

    Hyde, R.A., LLNL

    1998-07-16

    At Livermore we`ve spent the last two years examining an alternative approach towards very large aperture (VLA) telescopes, one based upon transmissive Fresnel lenses rather than on mirrors. Fresnel lenses are attractive for VLA telescopes because they are launchable (lightweight, packagable, and deployable) and because they virtually eliminate the traditional, very tight, surface shape requirements faced by reflecting telescopes. Their (potentially severe) optical drawback, a very narrow spectral bandwidth, can be eliminated by use of a second (much smaller) chromatically-correcting Fresnel element. This enables Fresnel VLA telescopes to provide either single band ({Delta}{lambda}/{lambda} {approximately} 0.1), multiple band, or continuous spectral coverage. Building and fielding such large Fresnel lenses will present a significant challenge, but one which appears, with effort, to be solvable.

  9. Synthetic aperture interferometry: error analysis

    SciTech Connect

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt.42, 701 (2003)].APOPAI0003-693510.1364/AO.42.000701 A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt.47, 1705 (2008)].APOPAI0003-693510.1364/AO.47.001705 Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process.

  10. Thermal fuse for high-temperature batteries

    DOEpatents

    Jungst, Rudolph G.; Armijo, James R.; Frear, Darrel R.

    2000-01-01

    A thermal fuse, preferably for a high-temperature battery, comprising leads and a body therebetween having a melting point between approximately 400.degree. C. and 500.degree. C. The body is preferably an alloy of Ag--Mg, Ag--Sb, Al--Ge, Au--In, Bi--Te, Cd--Sb, Cu--Mg, In--Sb, Mg--Pb, Pb--Pd, Sb--Zn, Sn--Te, or Mg--Al.

  11. FUSE: lessons learned for future FUV missions

    NASA Astrophysics Data System (ADS)

    Moos, H. W.; McCandliss, Stephan R.; Kruk, Jeffrey W.

    2004-10-01

    The far ultraviolet spectral region (roughly 900 - 1200 Å) is densely packed with strong atomic, ionic and molecular transitions of astrophysical importance. Many of these transitions provide unique access to the associated species. This spectral region is also technically challenging: optical reflectivities are limited, contamination control requirements are severe and detectors must be windowless. The Far Ultraviolet Spectroscopic Explorer (FUSE) covers the spectral region 905 -1187 Å with a resolution ~ 15 km s-1. The mission, launched in June 1999 and now in its fifth year of science operations, has reaped a rich scientific harvest from this spectral region. This paper will examine the lessons learned from the FUSE mission with the perspective of looking ahead to possible future missions. In order to build on the scientific advances of the FUSE mission, such a mission would require both increased sensitivity and higher spectral resolution. We conclude that achieving these requirements will necessitate, among other advances, new approaches to far ultraviolet mirror coating technology. We also examine the possibility of accessing the far ultraviolet using an ultraviolet observatory designed for longer wavelength ultraviolet radiation.

  12. Immobilized β-cyclodextrin-based silica vs polymer monoliths for chiral nano liquid chromatographic separation of racemates.

    PubMed

    Ghanem, Ashraf; Ahmed, Marwa; Ishii, Hideaki; Ikegami, Tohru

    2015-01-01

    The enantioselectivity of immobilized β-cyclodextrin phenyl carbamate-based silica monolithic capillary columns was compared to our previously described polymer counterpart. 2,3,6-Tris(phenylcarbamoyl)-β-cyclodextrin-6-methacrylate was used as a functional monomer for the preparation of β-cyclodextrin (β-CD)-based silica and polymer monoliths. The silica monoliths were prepared via the sol-gel technique in fused silica capillary followed by modification of the bare silica monoliths with an anchor group prior to polymerization with β-CD methacrylate using either 2,2'-azobis(isobutyronitrile) or benzoylperoxide as radical initiators. On the other hand, the polymer monoliths were prepared via the copolymerization of β-CD methacrylate and ethylene glycol dimethacrylate in different ratios in situ in fused silica capillary. The prepared silica/polymer monoliths were investigated for the chiral separation of different classes of pharmaceuticals namely; α- and β-blockers, anti-inflammatory drugs, antifungal drugs, dopamine antagonists, norepinephrine-dopamine reuptake inhibitors, catecholamines, sedative hypnotics, diuretics, antihistaminics, anticancer drugs and antiarrhythmic drugs. Baseline separation was achieved for alprenolol, bufuralol, carbuterol, cizolertine, desmethylcizolertine, eticlopride, ifosfamide, 1-indanol, propranolol, tebuconazole, tertatolol and o-methoxymandelic acid under reversed phase conditions using mobile phase composed of methanol and water. The silica-based monoliths showed a comparative enantioselectivity to the polymer monoliths. PMID:25476312

  13. A systematic review of aperture shapes

    NASA Astrophysics Data System (ADS)

    Schultz, A. B.; Frazier, T. V.

    The paper discusses the application of apodization to reflecting telescopes. The diffraction pattern of a telescope, which is the image of a star, can be changed considerably by using different aperture shapes in combination with appropriately shaped occulting masks on the optical axis. Aperture shapes studied were the circular, square, and hexagonal. Polaris (α-UMin) was used as the test system.

  14. ABCD matrix for apertured spherical waves.

    PubMed

    Wang, S; Bernabeu, E; Alda, J

    1991-05-01

    An ABCD matrix for describing the hard aperture under a large Fresnel number is defined in this Technical Note based on Li and Wolf's formula. It is useful for analyzing focal shifts of complicated optical systems with hard apertures. PMID:20700324

  15. Application of silica nanoparticles for increased silica availability in maize

    NASA Astrophysics Data System (ADS)

    Suriyaprabha, R.; Karunakaran, G.; Yuvakkumar, R.; Prabu, P.; Rajendran, V.; Kannan, N.

    2013-02-01

    Silica nanoparticles were extracted from rice husk and characterised comprehensively. The synthesised silica powders were amorphous in size with 99.7% purity (20-40 nm). Nanosilica was amended with red soil at 15 kg ha-1 along with micron silica. The influence of nanoscale on silica uptake, accumulation and nutritional variations in maize roots were evaluated through the studies such as root sectioning, elemental analysis and physiological parameters (root length and silica content) and compared with micron silica and control. Nanosilica treated soil reveals enhanced silica uptake and elongated roots which make the plant to resist in stress conditions like drought.

  16. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2002-12-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127-22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg II, Fe II, V II, etc observed in STIS/E230H spectra (see accompanying posters by Gull, Vieira, and Danks). The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-1 above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30x30 arcsec for FUSE, 0.2x0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic miniumum in 2003.

  17. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2003-01-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127- 22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg 11, Fe II, V II, etc observed in STIS/E230H spectra. The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-l above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30 x 30 arcsec for FUSE, 0.2 x 0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic minimum in 2003.

  18. New antifouling silica hydrogel.

    PubMed

    Beltrán-Osuna, Ángela A; Cao, Bin; Cheng, Gang; Jana, Sadhan C; Espe, Matthew P; Lama, Bimala

    2012-06-26

    In this work, a new antifouling silica hydrogel was developed for potential biomedical applications. A zwitterionic polymer, poly(carboxybetaine methacrylate) (pCBMA), was produced via atom-transfer radical polymerization and was appended to the hydrogel network in a two-step acid-base-catalyzed sol-gel process. The pCBMA silica aerogels were obtained by drying the hydrogels under supercritical conditions using CO(2). To understand the effect of pCBMA on the gel structure, pCBMA silica aerogels with different pCBMA contents were characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and the surface area from Brauner-Emmet-Teller (BET) measurements. The antifouling property of pCBMA silica hydrogel to resist protein (fibrinogen) adsorption was measured using enzyme-linked immunosorbent assay (ELISA). SEM images revealed that the particle size and porosity of the silica network decreased at low pCBMA content and increased at above 33 wt % of the polymer. The presence of pCBMA increased the surface area of the material by 91% at a polymer content of 25 wt %. NMR results confirmed that pCBMA was incorporated completely into the silica structure at a polymer content below 20 wt %. A protein adsorption test revealed a reduction in fibrinogen adsorption by 83% at 25 wt % pCBMA content in the hydrogel compared to the fibrinogen adsorption in the unmodified silica hydrogel. PMID:22607091

  19. Thermal emission by a subwavelength aperture

    NASA Astrophysics Data System (ADS)

    Joulain, Karl; Ezzahri, Younès; Carminati, Rémi

    2016-04-01

    We calculate, by means of fluctuational electrodynamics, the thermal emission of an aperture separating from the outside, vacuum or a material at temperature T. We show that thermal emission is very different whether the aperture size is large or small compared to the thermal wavelength. Subwavelength apertures separating vacuum from the outside have their thermal emission strongly decreased compared to classical blackbodies which have an aperture much larger than the wavelength. A simple expression of their emissivity can be calculated and their total emissive power scales as T8 instead of T4 for large apertures. Thermal emission of disk of materials with a size comparable to the wavelength is also discussed. It is shown in particular that emissivity of such a disk is increased when the material can support surface waves such as phonon polaritons.

  20. Micro Ring Grating Spectrometer with Adjustable Aperture

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

    2012-01-01

    A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

  1. Variable aperture collimator for high energy radiation

    DOEpatents

    Hill, Ronald A.

    1984-05-22

    An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated energy from emerging from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

  2. Outbursts In Symbiotic Binaries (FUSE 2000)

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J.; Sonneborn, George (Technical Monitor)

    2002-01-01

    During the past year, we made good progress on analysis of FUSE observations of the symbiotic binary Z And. For background, Z And is a binary system composed of a red giant and a hot component of unknown status. The orbital period is roughly 750 days. The hot component undergoes large-scale eruptions every 10-20 yr. An outburst began several years ago, triggering this FUSE opportunity. First, we obtained an excellent set of ground-based optical data in support, of the FUSE observations. We used FAST, a high throughput low resolution spectrograph on the 1.5-m telescope at Mt. Hopkins, Arizona. A 300 g/ mm grating blazed at 4750 A, a 3 in. slit, and a thinned Loral 512 x 2688 CCD gave us spectra covering 3800-7500 A at a resolution of 6 A. The wavelength solution for each spectrum has a probable error of +/- 0.5 A or better. Most of the resulting spectra have moderate signal-to-noise, S/.N approx. greater than 30 per pixel. The time coverage for these spectra is excellent. Typically, we acquired spectra every 1-2 nights during dark runs at Mt. Hopkins. These data cover most of the rise and all of the decline of the recent outburst. The spectra show a wealth of emission lines, including H I, He I, He II, [Fe V11], and the Raman scattering bands at 6830 A and 7088 A. The Raman bands and other high ionization features vary considerably throughout the outburst. These features will enable us to correlate variations in the FUSE spectra with variations in the optical spectra. Second, we began an analysis of FUSE spectra of Z And. We have carefully examined the spectra, identifying real features and defects. We have identified and measured fluxes for all strong emission lines, including the O VI doublet at 1032 A and 1038 A. These and several other strong emission lines display pronounced P Cygni absorption components indicative of outgrowing gas. We will attempt to correlate these velocities with similar profiles observed on optical spectra. The line velocities - together

  3. Novel 3-hydroxypropyl bonded phase by direct hydrosilylation of allyl alcohol on amorphous hydride silica

    PubMed Central

    Gómez, Jorge E.; Navarro, Fabián H.; Sandoval, Junior E.

    2015-01-01

    A novel 3-hydroxypropyl (propanol) bonded silica phase has been prepared by hydrosilylation of allyl alcohol on a hydride silica intermediate, in the presence of platinum (0)-divinyltetramethyldisiloxane (Karstedt's catalyst). The regio-selectivity of this synthetic approach had been correctly predicted by previous reports involving octakis(dimethylsiloxy)octasilsesquioxane (Q8M8H) and hydrogen silsesquioxane (T8H8), as molecular analogs of hydride amorphous silica. Thus, C-silylation predominated (~ 94%) over O-silylation, and high surface coverages of propanol groups (5±1 µmol/m2) were typically obtained in this work. The propanol-bonded phase was characterized by spectroscopic (IR and solid state NMR on silica microparticles), contact angle (on fused-silica wafers) and CE (on fused-silica tubes) techniques. CE studies of the migration behavior of pyridine, caffeine, tris(2,2’-bipyridine)Ru(II) chloride and lysozyme on propanol-modified capillaries were carried out. The adsorption properties of these select silanol-sensitive solutes were compared to those on the unmodified and hydride-modified tubes. It was found that hydrolysis of the SiH species underlying the immobilized propanol moieties leads mainly to strong ion-exchange based interactions with the basic solutes at pH 4, particularly with lysozyme. Interestingly, and in agreement with water contact angle and electroosmotic mobility figures, the silanol-probe interactions on the buffer-exposed (hydrolyzed) hydride surface are quite different from those of the original unmodified tube. PMID:24934906

  4. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  5. Oxygen configurations in silica

    SciTech Connect

    Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

    2000-07-15

    We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O{sub 2} bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society.

  6. Central aperture detection for auto direct read-write photoresist fabrication and inspection

    NASA Astrophysics Data System (ADS)

    Sierchio, Justin M.; Zaverton, Melissa; Johnson, Lee; Densmore, Victor; Milster, Thomas

    2014-08-01

    We show the design for a laser scanning microscopy defect detection system based upon the idea that the light can reflect off a photoresist-laden fused-silica sample containing defects, allowing height and depth information to be obtained through changes in light intensity. Image registration using predefined points is employed. Image processing techniques involving median and deconvolution filtering are used. Results show that the 2.1-μm resolution of these defects is obtainable, and receiver operating characteristic curves are used for quantifying results. Discriminabilities of 0.73 are achieved. Preliminary results for larger-array patterns through stitching processes are also shown.

  7. Cellulose-silica aerogels.

    PubMed

    Demilecamps, Arnaud; Beauger, Christian; Hildenbrand, Claudia; Rigacci, Arnaud; Budtova, Tatiana

    2015-05-20

    Aerogels based on interpenetrated cellulose-silica networks were prepared and characterised. Wet coagulated cellulose was impregnated with silica phase, polyethoxydisiloxane, using two methods: (i) molecular diffusion and (ii) forced flow induced by pressure difference. The latter allowed an enormous decrease in the impregnation times, by almost three orders of magnitude, for a sample with the same geometry. In both cases, nanostructured silica gel was in situ formed inside cellulose matrix. Nitrogen adsorption analysis revealed an almost threefold increase in pores specific surface area, from cellulose aerogel alone to organic-inorganic composite. Morphology, thermal conductivity and mechanical properties under uniaxial compression were investigated. Thermal conductivity of composite aerogels was lower than that of cellulose aerogel due to the formation of superinsulating mesoporous silica inside cellulose pores. Furthermore, composite aerogels were stiffer than each of reference aerogels. PMID:25817671

  8. Interferometric Synthetic Aperture Microscopy (ISAM)

    NASA Astrophysics Data System (ADS)

    Adie, Steven G.; Shemonski, Nathan D.; Ralston, Tyler S.; Carney, P. Scott; Boppart, Stephen A.

    The trade-off between transverse resolution and depth-of-field, and the mitigation of optical aberrations, are long-standing problems in optical imaging. The deleterious impact of these problems on three-dimensional tomography increases with numerical aperture (NA), and so they represent a significant impediment for real-time cellular resolution tomography over the typical imaging depths achieved with OCT. With optical coherence microscopy (OCM), which utilizes higher-NA optics than OCT, the depth-of-field is severely reduced, and it has been postulated that aberrations play a major role in reducing the useful imaging depth in OCM. Even at lower transverse resolution, both these phenomena produce artifacts that degrade the imaging of fine tissue structures. Early approaches to the limited depth-of-field problem in time-domain OCT utilized dynamic focusing. In spectral-domain OCT, this focus-shifting approach to data acquisition leads to long acquisition times and large datasets. Adaptive optics (AO) has been utilized to correct optical aberrations, in particular for retinal OCT, but in addition to requiring elaborate and expensive setups, the real-time optimization requirements at the time of imaging, and the correction of spatially varying effects of aberrations throughout an imaged volume, remain as significant challenges. This chapter presents computed imaging solutions for the reconstruction of sample structure when imaging with ideal and aberrated Gaussian beams.

  9. Smov Fos/fgs Fine Alignment (small Apertures)

    NASA Astrophysics Data System (ADS)

    Kinney, Anne

    1994-01-01

    The goal is to measure the precise aperture locations and sizes. The analysis of the observations will result in database changes to the table of aperture locations. Precise aperture locations will be determined by performing a raster step and dwell sequence in the FOS apertures along the edges of the apertures. An aperture map is required at each step of the dwell sequence. This test has to be conducted for both the RED and BLUE detectors.

  10. Smov Fos/fgs Fine Alignment (small Apertures) Revitalized

    NASA Astrophysics Data System (ADS)

    Kinney, Anne

    1994-01-01

    The goal is to measure the precise aperture locations and sizes. The analysis of the observations will result in database changes to the table of aperture locations. Precise aperture locations will be determined by performing a raster step and dwell sequence in the FOS apertures along the edges of the apertures. An aperture map is required at each step of the dwell sequence. This test has to be conducted for both the RED and BLUE detectors.

  11. Crystalline Silica Primer

    USGS Publications Warehouse

    Staff- Branch of Industrial Minerals

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  12. Synthetic aperture methods for angular scatter imaging

    NASA Astrophysics Data System (ADS)

    Guenther, Drake A.; Ranganathan, Karthik; McAllister, Michael J.; Rigby, K. W.; Walker, William F.

    2004-04-01

    Angular scatter offers a new source of tissue contrast and an opportunity for tissue characterization in ultrasound imaging. We have previously described the application of the translating apertures algorithm (TAA) to coherently acquire angular scatter data over a range of scattering angles. While this approach works well at the focus, it suffers from poor depth of field (DOF) due to a finite aperture size. Furthermore, application of the TAA with large focused apertures entails a tradeoff between spatial resolution and scattering angle resolution. While large multielement apertures improve spatial resolution, they encompass many permutations of transmit/receive element pairs. This results in the simultaneous interrogation of multiple scattering angles, limiting angular resolution. We propose a synthetic aperture imaging scheme that achieves both high spatial resolution and high angular resolution. In backscatter acquisition mode, we transmit successively from single transducer elements, while receiving on the same element. Other scattering angles are interrogated by successively transmitting and receiving on different single elements chosen with the appropriate spatial separation between them. Thus any given image is formed using only transmit/receive element pairs at a single separation. This synthetic aperture approach minimizes averaging across scattering angles, and yields excellent angular resolution. Likewise, synthetic aperture methods allow us to build large effective apertures to maintain a high spatial resolution. Synthetic dynamic focusing and dynamic apodization are applied to further improve spatial resolution and DOF. We present simulation results and experimental results obtained using a GE Logiq 700MR system modified to obtain synthetic aperture TAA data. Images of wire targets exhibit high DOF and spatial resolution. We also present a novel approach for combining angular scatter data to effectively reduce grating lobes. With this approach we have

  13. Synthesis of novel fused quinazolinone derivatives.

    PubMed

    Mahdavi, Mohammad; Lotfi, Vahid; Saeedi, Mina; Kianmehr, Ebrahim; Shafiee, Abbas

    2016-08-01

    A four-step synthetic route was developed for the synthesis of novel fused quinazolinones, quinazolino[3,4-a]quinazolinones, and isoinodolo[2,1-a]quinazolino[1,2-c]quinazolineones. Reaction of isatoic anhydride and different amines gave various 2-aminobenzamides. Then, reaction of 2-aminobenzamides with 2-nitrobenzaldehyde followed by the reduction of nitro group afforded 2-(2-aminophenyl)-3-aryl-2,3-dihydroquinazolin-4(1H)-one derivatives. Finally, reaction of the latter compounds with aromatic aldehydes or 2-formylbenzoic acid led to the formation of the corresponding products. PMID:27209476

  14. Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

    PubMed

    Borges, Endler M

    2015-04-01

    Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed. PMID:25234386

  15. Synthesis and characterization of a multimode stationary phase: Congo red derivatized silica in nano-flow HPLC.

    PubMed

    Zhang, Yi; Zhang, Yan; Wang, Guan; Chen, Wujuan; He, Pingang; Wang, Qingjiang

    2016-02-01

    A novel Congo red (CR) derivatized silica stationary phase was prepared and packed into a fused silica capillary tube for nano-flow HPLC. A variety of analytes including poly-aromatic hydrocarbons, parabens, acids, sulfonamides, bases, and nucleosides were successfully separated using the CR. In comparison with commercial ODS columns, this new stationary phase has a different separation mechanism (hydrophobically-assisted ion-exchange), which was evident in the separation of benzoic acid derivatives and sulfonamides. The successful application of CR-bonded silica stationary phase in the HILIC and PALC modes demonstrates the effectiveness of this potential chromatographic material in nano flow HPLC. PMID:26646316

  16. Longwave infrared (LWIR) coded aperture dispersive spectrometer.

    PubMed

    Fernandez, C; Guenther, B D; Gehm, M E; Brady, D J; Sullivan, M E

    2007-04-30

    We describe a static aperture-coded, dispersive longwave infrared (LWIR) spectrometer that uses a microbolometer array at the detector plane. The two-dimensional aperture code is based on a row-doubled Hadamard mask with transmissive and opaque openings. The independent column code nature of the matrix makes for a mathematically well-defined pattern that spatially and spectrally maps the source information to the detector plane. Post-processing techniques on the data provide spectral estimates of the source. Comparative experimental results between a slit and coded aperture for emission spectroscopy from a CO(2) laser are demonstrated. PMID:19532832

  17. Scalar wave diffraction from a circular aperture

    SciTech Connect

    Cerjan, C.

    1995-01-25

    The scalar wave theory is used to evaluate the expected diffraction patterns from a circular aperture. The standard far-field Kirchhoff approximation is compared to the exact result expressed in terms of oblate spheroidal harmonics. Deviations from an expanding spherical wave are calculated for circular aperture radius and the incident beam wavelength using suggested values for a recently proposed point diffractin interferometer. The Kirchhoff approximation is increasingly reliable in the far-field limit as the aperture radius is increased, although significant errors in amplitude and phase persist.

  18. Three dimensional digital holographic aperture synthesis.

    PubMed

    Crouch, Stephen; Kaylor, Brant M; Barber, Zeb W; Reibel, Randy R

    2015-09-01

    Aperture synthesis techniques are applied to temporally and spatially diverse digital holograms recorded with a fast focal-plane array. Because the technique fully resolves the downrange dimension using wide-bandwidth FMCW linear-chirp waveforms, extremely high resolution three dimensional (3D) images can be obtained even at very long standoff ranges. This allows excellent 3D image formation even when targets have significant structure or discontinuities, which are typically poorly rendered with multi-baseline synthetic aperture ladar or multi-wavelength holographic aperture ladar approaches. The background for the system is described and system performance is demonstrated through both simulation and experiments. PMID:26368474

  19. Dissociation of silica at high pressure

    NASA Astrophysics Data System (ADS)

    Hicks, Damien; Boehly, Tom

    2005-07-01

    Measurements of the temperature and optical reflectivity of quartz and fused silica under shock loading from 100 to 1000 GPa have revealed evidence for dissociation of silica between ˜150 and 400 GPa. Using attenuating laser-driven shock waves a continuous record of the temperature and reflectivity dependence on pressure has been obtained in both materials allowing the specific heat capacity and electronic conductivity to be deduced. Results show that between 150 and 400 GPa the specific heat rises significantly above that expected from the Dulong-Petit law, indicating the presence of a latent energy. Coincident with this anomalous specific heat is a rapid rise in electronic conductivity. Both these observables suggest that dissociation is occurring in the dense fluid. In addition temperature measurements near 5000 K detect a discontinuity at the melt transition, as measured earlier on gas gun experiments. This work was performed under the auspices of the US DOE by LLNL under Contract No. W-7405-ENG-48 and by the University of Rochester under Cooperative Agreement No. DE-FC03-92SF19460.

  20. Photodecomposition of chloromethanes adsorbed on silica surfaces

    NASA Technical Reports Server (NTRS)

    Ausloos, P.; Rebbert, R. E.; Glasgow, L.

    1977-01-01

    Irradiation of CCl4, CFCl3, and CF2Cl2 in the presence of C2H6 in vessels containing silica sand or fused quartz tubing results in the formation of chlorine-containing products. The formation of these compounds occurs at wavelengths extending up to approximately 400 nm, that is, at wavelengths well beyond the absorption threshold of the chloromethanes in the gas phase. It is suggested that CCl4 adsorbed on silica surfaces photodissociates to yield CCl3 and CCl2 species. The poor material balance obtained in these experiments indicates that several of the chlorine-containing fragments are strongly adsorbed on the surface. At a CCl4 pressure of 13 Pa (0.1 torr), photolysis with 366 nm light in the presence of sand results in the decomposition of one molecule for every 10,000 photons striking the surface. Under otherwise identical conditions, the photon-induced breadkdown of CFCl3 and CF2Cl2 is respectively only 10% or 3% as efficient.