WorldWideScience

Sample records for surface reflected laser

  1. Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

    Science.gov (United States)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2009-05-01

    We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water-air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water-air interface was approximately 12-16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water-air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

  2. Reflection of illumination laser from gas metal arc weld pool surface

    International Nuclear Information System (INIS)

    Ma, Xiaoji; Zhang, YuMing

    2009-01-01

    The weld pool is the core of the welding process where complex welding phenomena originate. Skilled welders acquire their process feedback primarily from the weld pool. Observation and measurement of the three-dimensional weld pool surface thus play a fundamental role in understanding and future control of complex welding processes. To this end, a laser line is projected onto the weld pool surface in pulsed gas metal arc welding (GMAW) and an imaging plane is used to intercept its reflection from the weld pool surface. Resultant images of the reflected laser are analyzed and it is found that the weld pool surface in GMAW does specularly reflect the projected laser as in gas tungsten arc welding (GTAW). Hence, the weld pool surface in GMAW is also specular and it is in principle possible that it may be observed and measured by projecting a laser pattern and then intercepting and imaging the reflection from it. Due to high frequencies of surface fluctuations, GMAW requires a relatively short time to image the reflected laser

  3. Vertical-cavity surface-emitting laser vapor sensor using swelling polymer reflection modulation

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgård; Dohn, Søren

    2012-01-01

    Vapor detection using a low-refractive index polymer for reflection modulation of the top mirror in a vertical-cavity surface-emitting laser (VCSEL) is demonstrated. The VCSEL sensor concept presents a simple method to detect the response of a sensor polymer in the presence of volatile organic...

  4. Morphology and phase structures of CW laser-induced oxide layers on iron surface with evolving reflectivity and colors

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Taotao, E-mail: wutaotao@nint.ac.cn; Wang, Lijun; Wei, Chenghua; Zhou, Menglian; He, Minbo; Wu, Lixiong

    2016-11-30

    Highlights: • Firstly, iron samples with different color features were obtained by continuous wave laser irradiation depending on progressive durations. The real-time reflectivity and temperature of samples were measured. The color and the reflectivity evolution were related. They were both caused by the forming oxide films. • Secondly, laser-induced oxidation process of iron was studied by microscope, X-ray diffraction and Raman spectrum. The first formed magnetite made the surface reflectivity decline rapidly and caused the “positive feedback” effect because of molecular absorption. The later formed hematite oscillated the reflectivity by interference effect. • Lastly, the laser-induced oxide films were thin, orientated and badly crystallized. The Wagner oxidation theory was incapable of describing the non-isothermal and early stage oxidation process. So we emphasized that a precise oxidation model depending on the experiment and the optical constants of the laser-induced oxides must be studied. - Abstract: Laser-induced oxidation will change the laser reflectivity and color features of metal surface. Both changes can be theoretically calculated based on the oxidation kinetics and the optical constants of oxides. For the purpose of calculation, the laser-induced oxidation process of pure polycrystalline iron was studied. Samples with various color features were obtained by continuous wave Nd:YAG fiber laser (1.06 μm) irradiation depending on progressive durations in the intensity of 1.90 W/cm{sup 2}. The real-time reflectivity and temperature were measured with integral sphere and thermocouples. The irradiated surface morphology and phase structures were characterized by microscope, X-ray diffraction and Raman spectrum. It was found that the first formed magnetite made the surface reflectivity decline rapidly and caused the “positive feedback” effect because of molecular absorption. The later formed hematite oscillated the reflectivity by

  5. RESEARCH OF THE ENTRANCE ANGLE EFFECT ON THE REFLECTANCE SPECTRA OF THE STAINLESS STEEL SURFACE OXIDIZED BY PULSED LASER RADIATION

    Directory of Open Access Journals (Sweden)

    V. P. Veiko

    2016-05-01

    Full Text Available Subject of Research.Oxide films on the metal surfaces can be obtained both by surface-uniform infrared heating and local laser treatment e.g. by sequence of nanosecond laser pulses. Due to interference in created films the coloration of treated area is observed. The present work shows the results of spectrophotometric measurements for various light entrance angles in the range of 10-60°. Method. AISI 304 stainless steel plates were oxidized by two methods: in muffle furnace FM - 10 (Т= 500-600° С, t = 5-7 min. and at line-by-line scanning by sequence of nanosecond laser pulses (λ = 1.06 μm, τ =100 ns, r = 25 μm,q=2.91∙107 W/cm2, Nx = 30, Ny = 1. Surface research in optical resolution was realized by Carl Zeiss Axio Imager A1M. Reflectance spectra were obtained with spectrophotometer Lambda Perkin 1050 with integrating sphere at different fixed light incidence angles. Topographic features were detected by scanning probe microscopy investigation with NanoEducator equipment. Main Results. The quantitative surface geometry characteristics of AISI 304 stainless steel patterns treated by different methods are obtained. It was found that the increase of light entrance angle has no influence on the form of reflection coefficient dependence from a wavelength, but a blue-shift occurs especially for the case of laser treatment. This difference can be caused by surface topology formed by laser heating and variety of oxide film thickness. This effect results in more significant change in observed sample color for laser treatment then for infrared heating. Practical Relevance. The results obtained in the present work can be used to implement a new element of product protection against forgery with the product marking.

  6. Study on the effect of ambient gas on nanostructure formation on metal surfaces during femtosecond laser ablation for fabrication of low-reflective surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Smausz, Tomi, E-mail: tomi@physx.u-szeged.hu [MTA-SZTE Research Group on Photoacoustic Spectroscopy, University of Szeged, 6720 Szeged, Dóm tér 9 (Hungary); Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Csizmadia, Tamás [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Attosecond Light Pulse Source, ELI-Hu Nkft, H-6720 Szeged, Dugonics ter 13 (Hungary); Tápai, Csaba; Kopniczky, Judit [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Oszkó, Albert [Department of Physical Chemistry and Material Science, University of Szeged, H-6720 Szeged, Aradi vértanuk tere 1 (Hungary); Ehrhardt, Martin; Lorenz, Pierre; Zimmer, Klaus; Prager, Andrea [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstr. 15, 04318 Leipzig (Germany); Hopp, Béla [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary)

    2016-12-15

    Highlights: • Metal surfaces were irradiated with femtosecond laser in different gas environments. • The reflectivity, morphology and chemical composition of the surfaces were studied. • Darkening was influenced by chemical and physical interaction of the plume and gas. • Molecular mass of the applied gas had an impact on the nanostructure formation. • For some of the used metals the oxide formation affected the reflective properties. - Abstract: Nanostructure formation on bulk metals (silver, gold, copper and titanium) by femtosecond Ti-sapphire laser irradiation (775 nm, 150 fs) is studied aiming the production of low-reflectivity surfaces and the better understanding of the development process. The experiments were performed in nitrogen, air, oxygen and helium environments at atmospheric pressure. The samples were irradiated with fluences in the 0.1–2 J/cm{sup 2} range and an average pulse number of 100 falling over a given area. The reflectivity of the treated surfaces was determined by a microspectrometer in the 450–800 nm range and their morphology was studied by scanning electron microscopy. The gas ambience influenced the results via two effects: formation processes and the chemically-induced modifications of the nanostructures. In case of He the nanoparticle aggregates–otherwise generally present–are predominantly missing, which leads to a lower darkening efficiency. The presence of oxygen enhances the darkening effect for copper mostly at lower fluences, while causes a slow increase in reflectivity in the case of titanium (in case of pure oxygen) in the high fluence range. The surface morphology in case of nitrogen and air were quite similar probably due to their close molecular mass values.

  7. Surface morphology of laser superheated Pb(100)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.H.; Lin, B.; Elsayed-Ali, H.E.

    1999-11-01

    The change in the surface vacancy density after heating of Pb(100) with {approximately}100 ps laser pulses is investigated using reflection high-energy electron diffraction. The surface vacancy density remains unchanged when the surface is superheated without melting. However, when the laser fluence is high enough to cause surface melting, the surface vacancy density increases. This increase in vacancy density is attributed to fast diffusion of atoms in the liquid film formed on Pb(100) during laser melting.

  8. Measuring Light Reflectance of BGO Crystal Surfaces

    Science.gov (United States)

    Janecek, Martin; Moses, William W.

    2008-10-01

    A scintillating crystal's surface reflectance has to be well understood in order to accurately predict and optimize the crystal's light collection through Monte Carlo simulations. In this paper, we measure the inner surface reflectance properties for BGO. The measurements include BGO crystals with a mechanically polished surface, rough-cut surface, and chemically etched surface, and with various reflectors attached, both air-coupled and with coupling compound. The measurements are performed with a laser aimed at the center of a hemispherical shaped BGO crystal. The hemispherical shape eliminates any non-perpendicular angles for light entering and exiting the crystal. The reflected light is collected with an array of photodiodes. The laser can be set at an arbitrary angle, and the photodiode array is rotated to fully cover 2pi of solid angle. The current produced in the photodiodes is readout with a digital multimeter connected through a multiplexer. The two rows of photodiodes achieve 5-degree by 4-degree resolution, and the current measurement has a dynamic range of 105:1. The acquired data was not described by the commonly assumed linear combination of specular and diffuse (Lambertian) distributions, except for a very few surfaces. Surface roughness proved to be the most important parameter when choosing crystal setup. The reflector choice was of less importance and of almost no consequence for rough-cut surfaces. Pure specular reflection distribution for all incidence angles was measured for polished surfaces with VM2000 film, while the most Lambertian distribution for any surface finish was measured for titanium dioxide paint. The distributions acquired in this paper will be used to create more accurate Monte Carlo models for light reflection distribution within BGO crystals.

  9. Characterization of 2.3 μm GaInAsSb-based vertical-cavity surface-emitting laser structures using photo-modulated reflectance

    Energy Technology Data Exchange (ETDEWEB)

    Chai, G. M. T. [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Hosea, T. J. C., E-mail: j.hosea@surrey.ac.uk [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Fox, N. E.; Hild, K.; Ikyo, A. B.; Marko, I. P.; Sweeney, S. J. [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Bachmann, A.; Arafin, S.; Amann, M.-C. [Walter Schottky Institut, Technische Universität Munchen, Am Coulombwall 4, D-85748 Garching (Germany)

    2014-01-07

    We report angle dependent and temperature dependent (9 K–300 K) photo-modulated reflectance (PR) studies on vertical-cavity surface-emitting laser (VCSEL) structures, designed for 2.3 μm mid-infrared gas sensing applications. Changing the temperature allows us to tune the energies of the quantum well (QW) transitions relative to the VCSEL cavity mode (CM) energy. These studies show that this VCSEL structure has a QW-CM offset of 21 meV at room temperature. Consequently the QW ground-state transition comes into resonance with the CM at 220 ± 2 K. The results from these PR studies are closely compared with those obtained in a separate study of actual operating devices and show how the PR technique may be useful for device optimisation without the necessity of having first to process the wafers into working devices.

  10. Characterization of 2.3 μm GaInAsSb-based vertical-cavity surface-emitting laser structures using photo-modulated reflectance

    International Nuclear Information System (INIS)

    Chai, G. M. T.; Hosea, T. J. C.; Fox, N. E.; Hild, K.; Ikyo, A. B.; Marko, I. P.; Sweeney, S. J.; Bachmann, A.; Arafin, S.; Amann, M.-C.

    2014-01-01

    We report angle dependent and temperature dependent (9 K–300 K) photo-modulated reflectance (PR) studies on vertical-cavity surface-emitting laser (VCSEL) structures, designed for 2.3 μm mid-infrared gas sensing applications. Changing the temperature allows us to tune the energies of the quantum well (QW) transitions relative to the VCSEL cavity mode (CM) energy. These studies show that this VCSEL structure has a QW-CM offset of 21 meV at room temperature. Consequently the QW ground-state transition comes into resonance with the CM at 220 ± 2 K. The results from these PR studies are closely compared with those obtained in a separate study of actual operating devices and show how the PR technique may be useful for device optimisation without the necessity of having first to process the wafers into working devices

  11. Influence of a pulsed CO2 laser operating at 9.4 μm on the surface morphology, reflectivity, and acid resistance of dental enamel below the threshold for melting

    Science.gov (United States)

    Kim, Jin Wan; Lee, Raymond; Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2017-02-01

    Below the threshold for laser ablation, the mineral phase of enamel is converted into a purer phase hydroxyapatite with increased acid resistance. Studies suggest the possibility of achieving the conversion without visible surface alteration. In this study, changes in the surface morphology, reflectivity, and acid resistance were monitored with varying irradiation intensity. Bovine enamel specimens were irradiated using a CO2 laser operating at 9.4 μm with a Gaussian spatial beam profile-1.6 to 3.1 mm in diameter. After laser treatment, samples were subjected to demineralization to simulate the acidic intraoral conditions of dental decay. The resulting demineralization and erosion were assessed using polarization-sensitive optical coherence tomography, three-dimensional digital microscopy, and polarized light microscopy. Distinct changes in the surface morphology and the degree of inhibition were found within the laser-treated area in accordance with the laser intensity profile. Subtle visual changes were noted below the melting point for enamel that appear to correspond to thresholds for denaturation of the organic phase and thermal decomposition of the mineral phase. There was significant protection from laser irradiation in areas in which the reflectivity was not increased significantly, suggesting that aesthetically sensitive areas of the tooth can be treated for caries prevention.

  12. High-resolution computer-generated reflection holograms with three-dimensional effects written directly on a silicon surface by a femtosecond laser.

    Science.gov (United States)

    Wædegaard, Kristian J; Balling, Peter

    2011-02-14

    An infrared femtosecond laser has been used to write computer-generated holograms directly on a silicon surface. The high resolution offered by short-pulse laser ablation is employed to write highly detailed holograms with resolution up to 111 kpixels/mm2. It is demonstrated how three-dimensional effects can be realized in computer-generated holograms. Three-dimensional effects are visualized as a relative motion between different parts of the holographic reconstruction, when the hologram is moved relative to the reconstructing laser beam. Potential security applications are briefly discussed.

  13. Surface morphology of laser superheated Pb(111)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. H.; Lin, Bo; Zeng, X. L.; Elsayed-Ali, H. E.

    1998-05-01

    The step density on the vicinal Pb(111) surface after laser superheating and melting is investigated using reflection high-energy electron diffraction. The (00) beam profiles parallel and perpendicular to the incident beam are analyzed. For laser heating with ˜100 ps laser pulses, surface superheating does not significantly change the density of the steps and step edge roughness. A sudden increase in the average terrace width is observed after laser surface melting. The average terrace width and the string length at the step edge become as large as those at room temperature. The average terrace width at 573 K changes from 38±15 to 64±19 Å after laser surface melting, while the average string length at the step edge changes from 50±12 to 250±38 Å.

  14. Laser surface cleaning

    International Nuclear Information System (INIS)

    Freiwald, J.G.; Freiwald, D.A.

    1994-01-01

    The objective of this work is a laboratory demonstration that red-lead primer and two-part epoxy paints can be stripped from concrete and metal surfaces using surface cleaning systems based on pulsed-repetition CO 2 lasers. The three goals are to: (1) demonstrate coatings removal, including surface pore cleaning; (2) demonstrate that there is negligible release of ablated contaminants to the environment; and (3) demonstrate that the process will generate negligible amounts of additional waste compared to competing technologies. Phase 1 involved site visits to RMI and Fernald to assess the cleaning issues for buildings and parts. In addition, Phase 1 included detailed designs of a more powerful system for industrial cleaning rates, including laser, articulating optics, ablated-material capture suction nozzle attached to a horizontal raster scanner for floor cleaning, and filtration system. Some concept development is also being done for using robots, and for parts cleaning. In Phase 2 a transportable 6 kW system will be built and tested, with a horizontal surface scanner for cleaning paint from floors. The laboratory tests will again be instrumented. Some concept development will continue for using robots, and for parts cleaning. This report describes Phase 1 results

  15. Evidence for Surface Water Ice in the Lunar Polar Regions Using Reflectance Measurements from the Lunar Orbiter Laser Altimeter and Temperature Measurements from the Diviner Lunar Radiometer Experiment

    Science.gov (United States)

    Fisher, Elizabeth A.; Lucey, Paul G.; Lemelin, Myriam; Greenhagen, Benjamin T.; Siegler, Matthew A.; Mazarico, Erwan; Aharonson, Oded; Williams, Jean-Pierre; Hayne, Paul O.; Neumann, Gregory A.; hide

    2017-01-01

    We find that the reflectance of the lunar surface within 5 deg of latitude of theSouth Pole increases rapidly with decreasing temperature, near approximately 110K, behavior consistent with the presence of surface water ice. The North polar region does not show this behavior, nor do South polar surfaces at latitudes more than 5 deg from the pole. This South pole reflectance anomaly persists when analysis is limited to surfaces with slopes less than 10 deg to eliminate false detection due to the brightening effect of mass wasting, and also when the very bright south polar crater Shackleton is excluded from the analysis. We also find that south polar regions of permanent shadow that have been reported to be generally brighter at 1064 nm do not show anomalous reflectance when their annual maximum surface temperatures are too high to preserve water ice. This distinction is not observed at the North Pole. The reflectance excursion on surfaces with maximum temperatures below 110K is superimposed on a general trend of increasing reflectance with decreasing maximum temperature that is present throughout the polar regions in the north and south; we attribute this trend to a temperature or illumination-dependent space weathering effect (e.g. Hemingway et al. 2015). We also find a sudden increase in reflectance with decreasing temperature superimposed on the general trend at 200K and possibly at 300K. This may indicate the presence of other volatiles such as sulfur or organics. We identified and mapped surfaces with reflectances so high as to be unlikely to be part of an ice-free population. In this south we find a similar distribution found by Hayne et al. 2015 based on UV properties. In the north a cluster of pixels near that pole may represent a limited frost exposure.

  16. Evidence for surface water ice in the lunar polar regions using reflectance measurements from the Lunar Orbiter Laser Altimeter and temperature measurements from the Diviner Lunar Radiometer Experiment

    Science.gov (United States)

    Fisher, Elizabeth A.; Lucey, Paul G.; Lemelin, Myriam; Greenhagen, Benjamin T.; Siegler, Matthew A.; Mazarico, Erwan; Aharonson, Oded; Williams, Jean-Pierre; Hayne, Paul O.; Neumann, Gregory A.; Paige, David A.; Smith, David E.; Zuber, Maria T.

    2017-08-01

    We find that the reflectance of the lunar surface within 5° of latitude of the South Pole increases rapidly with decreasing temperature, near ∼110 K, behavior consistent with the presence of surface water ice. The North polar region does not show this behavior, nor do South polar surfaces at latitudes more than 5° from the pole. This South pole reflectance anomaly persists when analysis is limited to surfaces with slopes less than 10° to eliminate false detection due to the brightening effect of mass wasting, and also when the very bright south polar crater Shackleton is excluded from the analysis. We also find that south polar regions of permanent shadow that have been reported to be generally brighter at 1064 nm do not show anomalous reflectance when their annual maximum surface temperatures are too high to preserve water ice. This distinction is not observed at the North Pole. The reflectance excursion on surfaces with maximum temperatures below 110 K is superimposed on a general trend of increasing reflectance with decreasing maximum temperature that is present throughout the polar regions in the north and south; we attribute this trend to a temperature or illumination-dependent space weathering effect (e.g. Hemingway et al., 2015). We also find a sudden increase in reflectance with decreasing temperature superimposed on the general trend at 200 K and possibly at 300 K. This may indicate the presence of other volatiles such as sulfur or organics. We identified and mapped surfaces with reflectances so high as to be unlikely to be part of an ice-free population. In this south we find a similar distribution found by Hayne et al. (2015) based on UV properties. In the north a cluster of pixels near that pole may represent a limited frost exposure.

  17. Excimer laser irradiation of metal surfaces

    Science.gov (United States)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  18. Study of Laser Reflectivity on Skin

    International Nuclear Information System (INIS)

    Oidor-Garcia, J. J. J.; Trevino-Palacios, C. G.

    2008-01-01

    The response to the light on the skin can be manifested as temperature increase or creation of biochemical byproducts, in which further studies are required to asset the light effect. This response changes the average response over time and can produce discrepancies between similar studies. In this work we present a Low Level Laser Therapy (LLLT) study with feedback. We study the time response reflectivity of a 980 nm laser diode of 25 mW modulated at frequencies close to 40 kHz and detect the reflected light on a silicon photodiode, finding no direct correlation between different test points or individuals, while finding reproducible responses within the same individual and test point

  19. Comparison of the bidirectional reflectance distribution function of various surfaces

    International Nuclear Information System (INIS)

    Fernandez, R.; Seasholtz, R.G.; Oberle, L.G.; Kadambi, J.R.

    1989-01-01

    This paper describes the development and use of a system to measure the bidirectional reflectance distribution function (BRDF) of various surfaces. The BRDF measurements are to be used in the analysis and design of optical measurement systems such as laser anemometers. An Ar-ion laser (514 nm) was the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand-blasted Al, unworked Al, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests. 8 refs

  20. Inspection of surface defects for cladding tube with laser

    International Nuclear Information System (INIS)

    Senoo, Shigeo; Igarashi, Miyuki; Satoh, Masakazu; Miura, Makoto

    1978-01-01

    This paper presents the results of experiment on mechanizing the visual inspection of surface defects of cladding tubes and improving the reliability of surface defect inspection. Laser spot inspection method was adopted for this purpose. Since laser speckle pattern includes many informations about surface aspects, the method can be utilized as an effective means for detection or classification of the surface defects. Laser beam is focussed on cladding tube surfaces, and the reflected laser beam forms typical stellar speckle patterns on a screen. Sample cladding tubes are driven in longitudinal direction, and a photo-detector is placed at a position where secondary reflection will fall on the detector. Reflected laser beam from defect-free surfaces shows uniform distribution on the detector. When the incident focussed laser beam is directed to defects, the intensity of the reflected light is reduced. In the second method, laser beam is scanned by a rotating cube mirror. As the results of experiment, the typical patterns caused by defects were observed. It is clear that reflection patterns change with the kinds of defects. The sensitivity of defect detection decreases with the increase in laser beam diameter. Surface defect detection by intensity change was also tested. (Kato, T.)

  1. A climatology of visible surface reflectance spectra

    International Nuclear Information System (INIS)

    Zoogman, Peter; Liu, Xiong; Chance, Kelly; Sun, Qingsong; Schaaf, Crystal; Mahr, Tobias; Wagner, Thomas

    2016-01-01

    We present a high spectral resolution climatology of visible surface reflectance as a function of wavelength for use in satellite measurements of ozone and other atmospheric species. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument is planned to measure backscattered solar radiation in the 290–740 nm range, including the ultraviolet and visible Chappuis ozone bands. Observation in the weak Chappuis band takes advantage of the relative transparency of the atmosphere in the visible to achieve sensitivity to near-surface ozone. However, due to the weakness of the ozone absorption features this measurement is more sensitive to errors in visible surface reflectance, which is highly variable. We utilize reflectance measurements of individual plant, man-made, and other surface types to calculate the primary modes of variability of visible surface reflectance at a high spectral resolution, comparable to that of TEMPO (0.6 nm). Using the Moderate-resolution Imaging Spectroradiometer (MODIS) Bidirection Reflectance Distribution Function (BRDF)/albedo product and our derived primary modes we construct a high spatial resolution climatology of wavelength-dependent surface reflectance over all viewing scenes and geometries. The Global Ozone Monitoring Experiment–2 (GOME-2) Lambertian Equivalent Reflectance (LER) product provides complementary information over water and snow scenes. Preliminary results using this approach in multispectral ultraviolet+visible ozone retrievals from the GOME-2 instrument show significant improvement to the fitting residuals over vegetated scenes. - Highlights: • Our goals was visible surface reflectance for satellite trace gas measurements. • Captured the range of surface reflectance spectra through EOF analysis. • Used satellite surface reflectance products for each given scene to anchor EOFs. • Generated a climatology of time/geometry dependent surface reflectance spectra. • Demonstrated potential to

  2. Repetitive output laser system and method using target reflectivity

    International Nuclear Information System (INIS)

    Johnson, R.R.

    1978-01-01

    An improved laser system and method for implosion of a thermonuclear fuel pellet is described in which that portion of a laser pulse reflected by the target pellet is utilized in the laser system to initiate a succeeding target implosion, and in which the energy stored in the laser system to amplify the initial laser pulse, but not completely absorbed thereby, is used to amplify succeeding laser pulses initiated by target refγlection

  3. Laser surface modification of PEEK

    Energy Technology Data Exchange (ETDEWEB)

    Riveiro, A., E-mail: ariveiro@uvigo.es [Applied Physics Department, University of Vigo ETSII, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Centro Universitario de la Defensa, Escuela Naval Militar, Plaza de Espana 2, 36920 Marin (Spain); Soto, R.; Comesana, R.; Boutinguiza, M.; Val, J. del; Quintero, F.; Lusquinos, F.; Pou, J. [Applied Physics Department, University of Vigo ETSII, Lagoas-Marcosende, 9, Vigo 36310 (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Role of laser irradiation wavelength on the surface modification of PEEK (polyether-ether-ketone) was investigated. Black-Right-Pointing-Pointer Adequate processing conditions to improve wettability, roughness, and cell adhesion characteristics are determined. Black-Right-Pointing-Pointer A design of experiments (DOE) methodology was performed. Black-Right-Pointing-Pointer UV (355 nm) radiation is the most promising laser radiation for improving the adhesive surface properties of PEEK. - Abstract: Polyether-ether-ketone (PEEK) is a synthetic thermoplastic polymer with excellent mechanical and chemical properties, which make it attractive for the field of reconstructive surgery. Nevertheless, this material has a poor interfacial biocompatibility due to its large chemical stability which induces poor adhesive bonding properties. The possibilities of enhancing the PEEK adhesive properties by laser treatments have been explored in the past. This paper presents a systematic approach to discern the role of laser irradiation wavelength on the surface modification of PEEK under three laser wavelengths ({lambda} = 1064, 532, and 355 nm) with the aim to determine the most adequate processing conditions to increase the roughness and wettability, the main parameters affecting cell adhesion characteristics of implants. Overall results show that the ultraviolet ({lambda} = 355 nm) laser radiation is the most suitable one to enhance surface wettability of PEEK.

  4. A Bayesian Reflection on Surfaces

    Directory of Open Access Journals (Sweden)

    David R. Wolf

    1999-10-01

    Full Text Available Abstract: The topic of this paper is a novel Bayesian continuous-basis field representation and inference framework. Within this paper several problems are solved: The maximally informative inference of continuous-basis fields, that is where the basis for the field is itself a continuous object and not representable in a finite manner; the tradeoff between accuracy of representation in terms of information learned, and memory or storage capacity in bits; the approximation of probability distributions so that a maximal amount of information about the object being inferred is preserved; an information theoretic justification for multigrid methodology. The maximally informative field inference framework is described in full generality and denoted the Generalized Kalman Filter. The Generalized Kalman Filter allows the update of field knowledge from previous knowledge at any scale, and new data, to new knowledge at any other scale. An application example instance, the inference of continuous surfaces from measurements (for example, camera image data, is presented.

  5. In situ reflectivity investigations of solid/liquid interface during laser backside etching

    International Nuclear Information System (INIS)

    Boehme, R.; Otto, T.; Zimmer, K.

    2006-01-01

    In situ reflectivity measurements of the solid/liquid interface with a pump-probe setup were performed during laser-induced backside wet etching (LIBWE) of fused silica with KrF excimer laser using toluene as absorbing liquid. The intensity, the temporal shape, and the duration of the reflected light measured in dependence on the laser fluence are discussed referring to the surface modification and the bubble formation. The vaporisation of the superheated liquid at the solid interface causes a considerable increase of the reflectivity and gives information about the bubble lifetime. The alterations of the reflectivity after bubbles collapse can be explained with the changed optical properties due to surface modifications of the solid surface. Comparative studies of the reflectivity at different times and the etch rate behaviour in dependence on the laser fluence show that the in situ measured surface modification begins just at the etch threshold fluence and correlates further with etch rate behaviour and the etched surface appearance. The already observed surface modification at LIBWE due to a carbon deposition and structural changes of the near surface region are approved by the changes of the interface reflectivity and emphasizes the importance of the modified surface region in the laser-induced backside wet etching process

  6. Simulation Tool for GNSS Ocean Surface Reflections

    DEFF Research Database (Denmark)

    Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

    2015-01-01

    GNSS coherent and incoherent reflected signals have the potential of deriving large scale parameters of ocean surfaces, as barotropic variability, eddy currents and fronts, Rossby waves, coastal upwelling, mean ocean surfaceheights, and patterns of the general ocean circulation. In the reflection...... zone the measurements may deriveparameters as sea surface roughness, winds, waves, heights and tilts from the spectral measurements. Previous measurements from the top of mountains and airplanes have shown such results leading.The coming satellite missions, CYGNSS, COSMIC-2, and GEROS...

  7. Use of reflective surfaces on roadway embankment

    DEFF Research Database (Denmark)

    Jørgensen, Anders Stuhr; Doré, Guy

    2007-01-01

    adherence characteristics for roadway use. In Kangerlussuaq Airport, western Greenland, ground-penetrating radar (GPR) has been used to compare the variation of the frost table underneath a normal black asphalt surface and a more reflective surface (white paint). The GPR results have shown a clear...

  8. Use of pre-pulse in laser spot welding of materials with high optical reflection

    Science.gov (United States)

    Mys, Ihor; Geiger, Manfred

    2003-11-01

    Laser micro welding has become a standard manufacturing technique, particularly in industry sectors, such as automotive and aerospace electronics or medical devices, where the requirements for strength, miniaturization and temperature resistance are constantly rising. So far the use of laser micro welding is limited due to the fluctuation of the quality of the welded joints, because the welding results for material with high optical reflection and thermal conductivity, such as copper and copper alloys, depend very strongly on the condition of the material surface. This paper presents investigations on the use of a laser pre-pulse in spot welding of electronic materials with Nd:YAG laser. In order to achieve reproducible joining results two strategies are followed-up. The first one utilizes a reflection-based process control for measuring the reflection during the short pre-pulse. The intensity of the reflected light is used to calculate an appropriated welding pulse power, which corresponds to the measured relative absorption. Adjustment of laser parameters according to the condition of the surface is done in real time before laser main pulse. A second possibility for the stabilization of copper welding is the employment of a short and powerful laser pre-pulse before laser main pulse. This pre-pulse affects the workpiece surface and creates more reproducible absorption conditions for the main pulse, independent from the initial situation on material surface.

  9. Laser study of phase changes in the surface layer of porous materials

    International Nuclear Information System (INIS)

    Wojtatowicz, T W

    2001-01-01

    The paper presents some aspects of the use of interference patterns observed upon reflection of laser radiation from the surface of a porous solid (laser speckles) for the study of moisture condensation in the near-surface layer. (interaction of laser radiation with matter. laser plasma)

  10. X-ray reflectivity and surface roughness

    International Nuclear Information System (INIS)

    Ocko, B.M.

    1988-01-01

    Since the advent of high brightness synchrotron radiation sources there has been a phenomenal growth in the use of x-rays as a probe of surface structure. The technique of x-ray reflectivity is particularly relevant to electrochemists since it is capable of probing the structure normal to an electrode surface in situ. In this paper the theoretical framework for x-ray reflectivity is reviewed and the results from previous non-electrochemistry measurements are summarized. These measurements are from the liquid/air interface (CCl 4 ), the metal crystal vacuum interface (Au(100)), and from the liquid/solid interface(liquid crystal/silicon). 34 refs., 5 figs

  11. Surface composition of Mercury from reflectance spectrophotometry

    Science.gov (United States)

    Vilas, Faith

    1988-01-01

    The controversies surrounding the existing spectra of Mercury are discussed together with the various implications for interpretations of Mercury's surface composition. Special attention is given to the basic procedure used for reducing reflectance spectrophotometry data, the factors that must be accounted for in the reduction of these data, and the methodology for defining the portion of the surface contributing the greatest amount of light to an individual spectrum. The application of these methodologies to Mercury's spectra is presented.

  12. Reflectance spectroscopy and asteroid surface mineralogy

    International Nuclear Information System (INIS)

    Gaffey, M.J.; Bell, J.F.; Cruikshank, D.P.

    1989-01-01

    Information available from reflectance spectroscopy on the surface mineralogy of asteroids is discussed. Current spectral interpretive procedures used in the investigations of asteroid mineralogy are described. Present understanding of the nature and history of asteroids is discussed together with some still unresolved issues such as the source of ordinary chondrites. 100 refs

  13. Effects of target shape and reflection on laser radar cross sections.

    Science.gov (United States)

    Steinvall, O

    2000-08-20

    Laser radar cross sections have been evaluated for a number of ideal targets such as cones, spheres, paraboloids, and cylinders by use of different reflection characteristics. The time-independent cross section is the ratio of the cross section of one of these forms to that of a plate with the same maximum radius. The time-dependent laser radar cross section involves the impulse response from the object shape multiplied by the beam's transverse profile and the surface bidirectional reflection distribution function. It can be clearly seen that knowledge of the combined effect of object shape and reflection characteristics is important for determining the shape and the magnitude of the laser radar return. The results of this study are of interest for many laser radar applications such as ranging, three-dimensional imaging-modeling, tracking, antisensor lasers, and target recognition.

  14. Surface Finish after Laser Metal Deposition

    Science.gov (United States)

    Rombouts, M.; Maes, G.; Hendrix, W.; Delarbre, E.; Motmans, F.

    Laser metal deposition (LMD) is an additive manufacturing technology for the fabrication of metal parts through layerwise deposition and laser induced melting of metal powder. The poor surface finish presents a major limitation in LMD. This study focuses on the effects of surface inclination angle and strategies to improve the surface finish of LMD components. A substantial improvement in surface quality of both the side and top surfaces has been obtained by laser remelting after powder deposition.

  15. Effects of laser radiation on surfaces and coatings

    International Nuclear Information System (INIS)

    Lowdermilk, W.H.

    1985-01-01

    A summary is given of the principal aspects of laser-induced damage to polished optical surfaces and dielectric, thin-film, high-reflectivity and antireflective coatings. Methods for producing porous antireflective surfaces and coatings and their damage properties are also reviewed. Finally, new areas of basic research to solve current and future problems are addressed

  16. On automatic visual inspection of reflective surfaces

    DEFF Research Database (Denmark)

    Kulmann, Lionel

    1995-01-01

    surfaces, providing new and exciting applications subject to automated visual inspection. Several contextual features have been surveyed along with introduction of novel methods to perform data-dependent enhancement of local surface appearance . Morphological methods have been described and utilized......This thesis descrbes different methods to perform automatic visual inspection of reflective manufactured products, with the aim of increasing productivity, reduce cost and improve the quality level of the production. We investigate two different systems performing automatic visual inspection....... The first is the inspection of highly reflective aluminum sheets, used by the Danish company Bang & Olufsen, as a part of the exterior design and general appearance of their audio and video products. The second is the inspection of IBM hard disk read/write heads for defects during manufacturing. We have...

  17. ASTER L2 Surface Reflectance SWIR and ASTER L2 Surface Reflectance VNIR V003

    Data.gov (United States)

    National Aeronautics and Space Administration — The ASTER L2 Surface Reflectance is a multi-file product that contains atmospherically corrected data for both the Visible Near-Infrared (VNIR) and Shortwave...

  18. Active laser radar (lidar) for measurement of corresponding height and reflectance images

    Science.gov (United States)

    Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

    1997-08-01

    For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments

  19. Laser ablation of liquid surface in air induced by laser irradiation through liquid medium

    Science.gov (United States)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2010-10-01

    The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally investigated. A supersonic liquid jet is observed at the liquid-air interface. The liquid surface layer is driven by a plasma plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only when an Nd:YAG laser pulse (wavelength: 1064 nm) is focused from the liquid onto air at a low fluence of 20 J/cm2. In this case, as Fresnel’s law shows, the incident and reflected electric fields near the liquid surface layer are superposed constructively. In contrast, when the incident laser is focused from air onto the liquid, a liquid jet is produced only at an extremely high fluence, several times larger than that in the former case. The similarities and differences in the liquid jets and atomization processes are studied for several liquid samples, including water, ethanol, and vacuum oil. The laser ablation of the liquid surface is found to depend on the incident laser energy and laser fluence. A pulse laser light source and high-resolution film are required to observe the detailed structure of a liquid jet.

  20. Laser welding, cutting and surface treatment

    International Nuclear Information System (INIS)

    Crafer, R.C.

    1984-01-01

    Fourteen articles cover a wide range of laser applications in welding, cutting and surface treatment. Future trends are covered as well as specific applications in shipbuilding, the manufacture of heart pacemakers, in the electronics industry, in automobile production and in the aeroengine industry. Safety with industrial lasers and the measurement of laser beam parameters are also included. One article on 'Lasers in the Nuclear Industry' is indexed separately. (U.K.)

  1. Laser surface texturing of tool steel: textured surfaces quality evaluation

    Science.gov (United States)

    Šugár, Peter; Šugárová, Jana; Frnčík, Martin

    2016-05-01

    In this experimental investigation the laser surface texturing of tool steel of type 90MnCrV8 has been conducted. The 5-axis highly dynamic laser precision machining centre Lasertec 80 Shape equipped with the nano-second pulsed ytterbium fibre laser and CNC system Siemens 840 D was used. The planar and spherical surfaces first prepared by turning have been textured. The regular array of spherical and ellipsoidal dimples with a different dimensions and different surface density has been created. Laser surface texturing has been realized under different combinations of process parameters: pulse frequency, pulse energy and laser beam scanning speed. The morphological characterization of ablated surfaces has been performed using scanning electron microscopy (SEM) technique. The results show limited possibility of ns pulse fibre laser application to generate different surface structures for tribological modification of metallic materials. These structures were obtained by varying the processing conditions between surface ablation, to surface remelting. In all cases the areas of molten material and re-cast layers were observed on the bottom and walls of the dimples. Beside the influence of laser beam parameters on the machined surface quality during laser machining of regular hemispherical and elipsoidal dimple texture on parabolic and hemispherical surfaces has been studied.

  2. Laser Surface Treatment of Sintered Alumina

    Science.gov (United States)

    Hagemann, R.; Noelke, C.; Kaierle, S.; Wesling, V.

    Sintered alumina ceramics are used as refractory materials for industrial aluminum furnaces. In this environment the ceramic surface is in permanent contact with molten aluminum resulting in deposition of oxidic material on its surface. Consequently, a lower volume capacity as well as thermal efficiency of the furnaces follows. To reduce oxidic adherence of the ceramic material, two laser-based surface treatment processes were investigated: a powder- based single-step laser cladding and a laser surface remelting. Main objective is to achieve an improved surface quality of the ceramic material considering the industrial requirements as a high process speed.

  3. Micro reflectance difference techniques: Optical probes for surface exploration

    Energy Technology Data Exchange (ETDEWEB)

    Lastras-Martinez, L.F.; Del Pozo-Zamudio, O.; Herrera-Jasso, R.; Ulloa-Castillo, N.A.; Balderas-Navarro, R.E.; Ortega-Gallegos, J.; Lastras-Martinez, A. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico)

    2012-06-15

    Micro reflectance difference spectroscopy ({mu}-RDS) is a promising tool for the in-situ and ex-situ characterization of semiconductors surfaces and interfaces. We discuss and compare two different approaches used to measure {mu}-RD spectra. One is based on a charge-coupled device (CCD) camera, while the other uses a laser and a XY translation stage. To show the performance of these systems, we have measured surface optical anisotropies of GaSb(001) sample on which anisotropic strains have been generated by preferential mechanical polishing along [110] and [1 anti 10] directions. The spectrometers are complementary and the selection of one of them depends on the sample to be investigated and on experimental conditions. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Femtosecond laser-induced surface wettability modification of polystyrene surface

    Science.gov (United States)

    Wang, Bing; Wang, XinCai; Zheng, HongYu; Lam, YeeCheong

    2016-12-01

    In this paper, we demonstrated a simple method to create either a hydrophilic or hydrophobic surface. With femtosecond laser irradiation at different laser parameters, the water contact angle (WCA) on polystyrene's surface can be modified to either 12.7° or 156.2° from its original WCA of 88.2°. With properly spaced micro-pits created, the surface became hydrophilic probably due to the spread of the water droplets into the micro-pits. While with properly spaced micro-grooves created, the surface became rough and more hydrophobic. We investigated the effect of laser parameters on WCAs and analyzed the laser-treated surface roughness, profiles and chemical bonds by surface profilometer, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). For the laser-treated surface with low roughness, the polar (such as C—O, C=O, and O—C=O bonds) and non-polar (such as C—C or C—H bonds) groups were found to be responsible for the wettability changes. While for a rough surface, the surface roughness or the surface topography structure played a more significant role in the changes of the surface WCA. The mechanisms involved in the laser surface wettability modification process were discussed.

  5. Measuring contact angle and meniscus shape with a reflected laser beam.

    Science.gov (United States)

    Eibach, T F; Fell, D; Nguyen, H; Butt, H J; Auernhammer, G K

    2014-01-01

    Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

  6. Reflectivity of transient Bragg reflection gratings in fiber laser with laser-wavelength selfsweeping

    Czech Academy of Sciences Publication Activity Database

    Peterka, Pavel; Honzátko, Pavel; Koška, Pavel; Todorov, Filip; Aubrecht, Jan; Podrazký, Ondřej; Kašík, Ivan

    2014-01-01

    Roč. 22, č. 24 (2014), s. 30024-30031 ISSN 1094-4087 R&D Projects: GA ČR(CZ) GAP205/11/1840 Institutional support: RVO:67985882 Keywords : Ytterbium-doped fiber * Laser optics * Q switched lasers Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.488, year: 2014

  7. Surface modification of polyethylene terephthalate using excimer and CO2 laser

    International Nuclear Information System (INIS)

    Mirzadeh, H.; Dadsetan, M.

    2002-01-01

    Complete text of publication follows. Attempts have been made to evaluate microstructuring which affects cell behaviour, physical and chemical changes produced by laser irradiation onto the polyethylene terephthalate (PET) surface. The surfaces of PET were irradiated using the CO 2 laser and KrF excimer pulsed laser. The changes in chemical and physical properties of the irradiated PET surface were investigated by attenuated total reflectance infrared spectroscopy (ATR-IR) and contact angle measurements. ATR-IR Spectra showed that the crystallinity in the surface region decreased due to the CO 2 laser and excimer laser irradiation. Scanning electron microscopy observations showed that the morphology of the laser irradiated PET surface changed due to laser irradiation. The results obtained from the cell behaviour studies revealed that changes of physico-chemical properties of the laser treated PET film have significantly changed in comparison with the unmodified PET

  8. Metal surface nitriding by laser induced plasma

    Science.gov (United States)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  9. Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light

    International Nuclear Information System (INIS)

    Dolotov, L E; Sinichkin, Yu P; Tuchin, Valerii V; Al'tshuler, G B; Yaroslavskii, I V

    2011-01-01

    The specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral dependence of the effective optical density of skin in the wavelength range from 650 to 700nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470nm, which correspond to the spectral ranges of maximum and minimum water absorption. (optical technologies in biophysics and medicine)

  10. Surface processing by high power excimer laser

    Energy Technology Data Exchange (ETDEWEB)

    Stehle, M [SOPRA, 92 - Bois-Colombes (France)

    1995-03-01

    Surface processing with lasers is a promising field of research and applications because lasers bring substantial advantages : laser beams work at distance, laser treatments are clean in respect of environment consideration and they offer innovative capabilities for surface treatment which cannot be reached by other way. Excimer lasers are pulsed, gaseous lasers which emit in UV spectral range - the most common are XeCl (308 nm), KrF (248 nm), ArF (193 nm). From 1980 up to 1994, many of them have been used for research, medical and industrial applications such as spectroscopy, PRK (photo-refractive keratotomy) and micro-machining. In the last six years, from 1987 up to 1993, efforts have been done in order to jump from 100 W average power up to 1 kW for XeCl laser at {lambda} = 308 nm. It was the aim of AMMTRA project in Japan as EU205 and EU213 Eureka projects in Europe. In this framework, SOPRA developed VEL (Very large Excimer Laser). In 1992, 1 kW (10 J x 100 Hz) millstone has been reached for the first time, this technology is based on X-Ray preionization and large laser medium (5 liters). Surface treatments based on this laser source are the main purpose of VEL Lasers. Some of them are given for instance : (a) Turbine blades made with metallic substrate and ceramic coatings on the top, are glazed in order to increase corrosion resistance of ceramic and metal sandwich. (b) Selective ablation of organic coatings deposited on fragile composite material is investigated in Aerospace industry. (c) Chock hardening of bulk metallic materials or alloys are investigated for automotive industry in order to increase wear resistance. (d) Ablation of thin surface oxides of polluted steels are under investigation in nuclear industry for decontamination. (J.P.N.).

  11. Surface processing by high power excimer laser

    International Nuclear Information System (INIS)

    Stehle, M.

    1995-01-01

    Surface processing with lasers is a promising field of research and applications because lasers bring substantial advantages : laser beams work at distance, laser treatments are clean in respect of environment consideration and they offer innovative capabilities for surface treatment which cannot be reached by other way. Excimer lasers are pulsed, gaseous lasers which emit in UV spectral range - the most common are XeCl (308 nm), KrF (248 nm), ArF (193 nm). From 1980 up to 1994, many of them have been used for research, medical and industrial applications such as spectroscopy, PRK (photo-refractive keratotomy) and micro-machining. In the last six years, from 1987 up to 1993, efforts have been done in order to jump from 100 W average power up to 1 kW for XeCl laser at λ = 308 nm. It was the aim of AMMTRA project in Japan as EU205 and EU213 Eureka projects in Europe. In this framework, SOPRA developed VEL (Very large Excimer Laser). In 1992, 1 kW (10 J x 100 Hz) millstone has been reached for the first time, this technology is based on X-Ray preionization and large laser medium (5 liters). Surface treatments based on this laser source are the main purpose of VEL Lasers. Some of them are given for instance : a) Turbine blades made with metallic substrate and ceramic coatings on the top, are glazed in order to increase corrosion resistance of ceramic and metal sandwich. b) Selective ablation of organic coatings deposited on fragile composite material is investigated in Aerospace industry. c) Chock hardening of bulk metallic materials or alloys are investigated for automotive industry in order to increase wear resistance. d) Ablation of thin surface oxides of polluted steels are under investigation in nuclear industry for decontamination. (J.P.N.)

  12. Laser reflection spot as a pattern in a diamond coating – a microscopic study

    Directory of Open Access Journals (Sweden)

    GORDANA S. RISTIĆ

    2009-07-01

    Full Text Available Diamond coatings were deposited by the synchronous and coupled action of a hot filament CVD method and a pulsed CO2 laser in spectro-absorbing and spectro-non-absorbing diamond precursor atmospheres. The obtained coatings were structured/patterned, i.e., they were comprised of uncovered, bare locations. An extra effect observed only in the spectro-active diamond precursor atmosphere was the creation of another laser spot in the coating – a reflection spot. In order to establish the practical usability of the latter one, extensive microscopic investigations were performed with consideration of the morphology changes in the spot of the direct laser beam. Normal incidence SEM images of this spot showed a smooth surface, without any pulse radiation damage. AFM imaging revealed the actual surface condition and gave precise data on the surface characteristics.

  13. Laser surface cladding:a literature survey

    OpenAIRE

    Gedda, Hans

    2000-01-01

    This work consists of a literature survey of a laser surface cladding in order to investigate techniques to improve the cladding rate for the process. The high local heat input caused by the high power density of the laser generates stresses and the process is consider as slow when large areas are processed. To avoid these disadvantages the laser cladding process velocity can be increased three or four times by use of preheated wire instead of the powder delivery system. If laser cladding is ...

  14. Bio-Inspired Functional Surfaces Based on Laser-Induced Periodic Surface Structures.

    Science.gov (United States)

    Müller, Frank A; Kunz, Clemens; Gräf, Stephan

    2016-06-15

    Nature developed numerous solutions to solve various technical problems related to material surfaces by combining the physico-chemical properties of a material with periodically aligned micro/nanostructures in a sophisticated manner. The utilization of ultra-short pulsed lasers allows mimicking numerous of these features by generating laser-induced periodic surface structures (LIPSS). In this review paper, we describe the physical background of LIPSS generation as well as the physical principles of surface related phenomena like wettability, reflectivity, and friction. Then we introduce several biological examples including e.g., lotus leafs, springtails, dessert beetles, moth eyes, butterfly wings, weevils, sharks, pangolins, and snakes to illustrate how nature solves technical problems, and we give a comprehensive overview of recent achievements related to the utilization of LIPSS to generate superhydrophobic, anti-reflective, colored, and drag resistant surfaces. Finally, we conclude with some future developments and perspectives related to forthcoming applications of LIPSS-based surfaces.

  15. Bio-Inspired Functional Surfaces Based on Laser-Induced Periodic Surface Structures

    Directory of Open Access Journals (Sweden)

    Frank A. Müller

    2016-06-01

    Full Text Available Nature developed numerous solutions to solve various technical problems related to material surfaces by combining the physico-chemical properties of a material with periodically aligned micro/nanostructures in a sophisticated manner. The utilization of ultra-short pulsed lasers allows mimicking numerous of these features by generating laser-induced periodic surface structures (LIPSS. In this review paper, we describe the physical background of LIPSS generation as well as the physical principles of surface related phenomena like wettability, reflectivity, and friction. Then we introduce several biological examples including e.g., lotus leafs, springtails, dessert beetles, moth eyes, butterfly wings, weevils, sharks, pangolins, and snakes to illustrate how nature solves technical problems, and we give a comprehensive overview of recent achievements related to the utilization of LIPSS to generate superhydrophobic, anti-reflective, colored, and drag resistant surfaces. Finally, we conclude with some future developments and perspectives related to forthcoming applications of LIPSS-based surfaces.

  16. Surface laser marking optimization using an experimental design approach

    Science.gov (United States)

    Brihmat-Hamadi, F.; Amara, E. H.; Lavisse, L.; Jouvard, J. M.; Cicala, E.; Kellou, H.

    2017-04-01

    Laser surface marking is performed on a titanium substrate using a pulsed frequency doubled Nd:YAG laser ( λ= 532 nm, τ pulse=5 ns) to process the substrate surface under normal atmospheric conditions. The aim of the work is to investigate, following experimental and statistical approaches, the correlation between the process parameters and the response variables (output), using a Design of Experiment method (DOE): Taguchi methodology and a response surface methodology (RSM). A design is first created using MINTAB program, and then the laser marking process is performed according to the planned design. The response variables; surface roughness and surface reflectance were measured for each sample, and incorporated into the design matrix. The results are then analyzed and the RSM model is developed and verified for predicting the process output for the given set of process parameters values. The analysis shows that the laser beam scanning speed is the most influential operating factor followed by the laser pumping intensity during marking, while the other factors show complex influences on the objective functions.

  17. Remote measurement of surface roughness, surface reflectance, and body reflectance with LiDAR.

    Science.gov (United States)

    Li, Xiaolu; Liang, Yu

    2015-10-20

    Light detection and ranging (LiDAR) intensity data are attracting increasing attention because of the great potential for use of such data in a variety of remote sensing applications. To fully investigate the data potential for target classification and identification, we carried out a series of experiments with typical urban building materials and employed our reconstructed built-in-lab LiDAR system. Received intensity data were analyzed on the basis of the derived bidirectional reflectance distribution function (BRDF) model and the established integration method. With an improved fitting algorithm, parameters involved in the BRDF model can be obtained to depict the surface characteristics. One of these parameters related to surface roughness was converted to a most used roughness parameter, the arithmetical mean deviation of the roughness profile (Ra), which can be used to validate the feasibility of the BRDF model in surface characterizations and performance evaluations.

  18. Reflection effects in multimode fiber systems utilizing laser transmitters

    Science.gov (United States)

    Bates, Harry E.

    1991-11-01

    A number of optical communication lines are now in use at NASA-Kennedy for the transmission of voice, computer data, and video signals. Now, all of these channels use a single carrier wavelength centered near 1300 or 1550 nm. Engineering tests in the past have given indications of the growth of systematic and random noise in the RF spectrum of a fiber network as the number of connector pairs is increased. This noise seems to occur when a laser transmitter is used instead of a LED. It has been suggested that the noise is caused by back reflections created at connector fiber interfaces. Experiments were performed to explore the effect of reflection on the transmitting laser under conditions of reflective feedback. This effort included computer integration of some of the instrumentation in the fiber optic lab using the Lab View software recently acquired by the lab group. The main goal was to interface the Anritsu Optical and RF spectrum analyzers to the MacIntosh II computer so that laser spectra and network RF spectra could be simultaneously and rapidly acquired in a form convenient for analysis. Both single and multimode fiber is installed at Kennedy. Since most are multimode, this effort concentrated on multimode systems.

  19. Precision metrology of NSTX surfaces using coherent laser radar ranging

    International Nuclear Information System (INIS)

    Kugel, H.W.; Loesser, D.; Roquemore, A. L.; Menon, M. M.; Barry, R. E.

    2000-01-01

    A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 microm laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of < 100microm at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated

  20. Optimization of plasma mirror reflectivity and optical quality using double laser pulses

    International Nuclear Information System (INIS)

    Scott, G G; Clarke, R J; Green, J S; Heathcote, R I; Neely, D; Bagnoud, V; Brabetz, C; Zielbauer, B; Powell, H W; McKenna, P; Arber, T D

    2015-01-01

    We measure a record 96 ±2.5% specularly reflected energy fraction from an interaction with a plasma mirror (PM) surface preionized by a controlled prepulse and find that the optical quality is dependent on the inter pulse time delay. Simulations show that the main pulse reflected energy is a strong function of plasma density scale length, which increases with the time delay and reaches a peak reflectivity for a scale length of 0.3 μm, which is achieved here for a pulse separation time of 3 ps. It is found that the incident laser quasi near field intensity distribution leads to nonuniformities in this plasma expansion and consequent critical surface position distribution. The PM optical quality is found to be governed by the resultant perturbations in the critical surface position, which become larger with inter pulse time delay. (paper)

  1. Craterlike structures on the laser cut surface

    Science.gov (United States)

    Shulyatyev, V. B.; Orishich, A. M.

    2017-10-01

    Analysis of the laser cut surface morphology remain topical. It is related with the fact that the surface roughness is the main index of the cut quality. The present paper deals with the experimental study of the relatively unstudied type of defects on the laser cut surface, dimples, or craters. According to the measurement results, amount of craters per unit of the laser cut surface area rises as the sheet thickness rises. The crater diameter rises together with the sheet thickness and distance from the upper sheet edge. The obtained data permit concluding that the defects like craters are observed predominantly in the case of thick sheets. The results agree with the hypothesis of crater formation as impact structures resulting from the melt drops getting on the cut channel walls upon separation from the cut front by the gas flow.

  2. The differential equation of an arbitrary reflecting surface

    Science.gov (United States)

    Melka, Richard F.; Berrettini, Vincent D.; Yousif, Hashim A.

    2018-05-01

    A differential equation describing the reflection of a light ray incident upon an arbitrary reflecting surface is obtained using the law of reflection. The derived equation is written in terms of a parameter and the value of this parameter determines the nature of the reflecting surface. Under various parametric constraints, the solution of the differential equation leads to the various conic surfaces but is not generally solvable. In addition, the dynamics of the light reflections from the conic surfaces are executed in the Mathematica software. Our derivation is the converse of the traditional approach and our analysis assumes a relation between the object distance and the image distance. This leads to the differential equation of the reflecting surface.

  3. ArF laser surface modification of polyethersulfone film: Effect of laser fluence in improving surface biocompatibility

    International Nuclear Information System (INIS)

    Pazokian, H.; Jelvani, S.; Mollabashi, M.; Barzin, J.; Azizabadi Farahani, G.

    2011-01-01

    ArF laser treatment of polyethersulfone (PES) films was performed to improve biocompatibility of surfaces. For this purpose, the threshold fluence for laser ablation of PES was obtained from experimental measurements and then samples were irradiated at 2 separate ranges of fluences, i.e. below and above the ablation threshold. In order to investigate the physico-chemical changes, the modified surfaces were characterized by attenuated total reflectance (ATR) infrared spectroscopy and contact-angle measurements. The biocompatibility of the treated samples in comparison to those untreated was examined in vitro using a platelet adhesion test. The number of adhered platelets was obtained using the lactate dehydrogenase (LDH) method. For surfaces irradiated below the ablation threshold, a high reduction in the number of the adhered platelets was observed; while this number increased in samples treated at the fluence above the ablation threshold. The change in platelet adhesion was attributed to the change in chemistry and roughness of the irradiated surfaces.

  4. Excimer laser surface modification: Process and properties

    Energy Technology Data Exchange (ETDEWEB)

    Jervis, T.R.; Nastasi, M. [Los Alamos National Lab., NM (United States); Hirvonen, J.P. [Technical Research Institute, Espoo (Finland). Metallurgy Lab.

    1992-12-01

    Surface modification can improve materials for structural, tribological, and corrosion applications. Excimer laser light has been shown to provide a rapid means of modifying surfaces through heat treating, surface zone refining, and mixing. Laser pulses at modest power levels can easily melt the surfaces of many materials. Mixing within the molten layer or with the gas ambient may occur, if thermodynamically allowed, followed by rapid solidification. The high temperatures allow the system to overcome kinetic barriers found in some ion mixing experiments. Alternatively, surface zone refinement may result from repeated melting-solidification cycles. Ultraviolet laser light couples energy efficiently to the surface of metallic and ceramic materials. The nature of the modification that follows depends on the properties of the surface and substrate materials. Alloying from both gas and predeposited layer sources has been observed in metals, semiconductors, and ceramics as has surface enrichment of Cr by zone refinement of stainless steel. Rapid solidification after melting often results in the formation of nonequilibrium phases, including amorphous materials. Improved surface properties, including tribology and corrosion resistance, are observed in these materials.

  5. Laser surface treatment of grey cast iron for automotive applications

    NARCIS (Netherlands)

    Ocelik, V.; Tang, P.N.; de Boer, M.C.; de Oliveira, U.; de Hosson, J.T.M.; DeHosson, JTM; Brebbia, CA; Nishida, SI

    2005-01-01

    The surface of pearlitic grey cast iron was treated using a 2 kW Nd:YAG laser beam with the final aim to improve its surface properties, mainly for automotive applications. Two kinds of laser surface treatments were experimentally applied. In the laser surface hardening approach the surface of cast

  6. Critical reflection activation analysis - a new near-surface probe

    International Nuclear Information System (INIS)

    Gunn, J.M.F.; Trohidou, K.N.

    1988-09-01

    We propose a new surface analytic technique, Critical Reflection Activation Analysis (CRAA). This technique allows accurate depth profiling of impurities ≤ 100A beneath a surface. The depth profile of the impurity is simply related to the induced activity as a function of the angle of reflection. We argue that the technique is practical and estimate its accuracy. (author)

  7. Infrared spectral reflectances of asteroid surfaces

    Science.gov (United States)

    Larson, H. P.; Veeder, G. J.

    1979-01-01

    This review compares the types of compositional information produced by three complementary techniques used in infrared observations of asteroid surfaces: broadband JHKL photometry, narrow band photometry, and multiplex spectroscopy. The high information content of these infrared observations permits definitive interpretations of asteroid surface compositions in terms of the major meteoritic minerals (olivine, pyroxene, plagioclase feldspar, hydrous silicates, and metallic Ni-Fe). These studies emphasize the individuality of asteroid surface compositions, the inadequacy of simple comparisons with spectra of meteorites, and the need to coordinate spectral measurements of all types to optimize diagnostic capabilities.

  8. Laser microstructuring for fabricating superhydrophobic polymeric surfaces

    Science.gov (United States)

    Cardoso, M. R.; Tribuzi, V.; Balogh, D. T.; Misoguti, L.; Mendonça, C. R.

    2011-02-01

    In this paper we show the fabrication of hydrophobic polymeric surfaces through laser microstructuring. By using 70-ps pulses from a Q-switched and mode-locked Nd:YAG laser at 532 nm, we were able to produce grooves with different width and separation, resulting in square-shaped pillar patterns. We investigate the dependence of the morphology on the surface static contact angle for water, showing that it is in agreement with the Cassie-Baxter model. We demonstrate the fabrication of a superhydrophobic polymeric surface, presenting a water contact angle of 157°. The surface structuring method presented here seems to be an interesting option to control the wetting properties of polymeric surfaces.

  9. Laser surface wakefield in a plasma column

    International Nuclear Information System (INIS)

    Gorbunov, L.M.; Mora, P.; Ramazashvili, R.R.

    2003-01-01

    The structure of the wakefield in a plasma column, produced by a short intense laser pulse, propagating through a gas affected by tunneling ionization is investigated. It is shown that besides the usual plasma waves in the bulk part of the plasma column [see Andreev et al., Phys. Plasmas 9, 3999 (2002)], the laser pulse also generates electromagnetic surface waves propagating along the column boundary. The length of the surface wake wave substantially exceeds the length of the plasma wake wave and its electromagnetic field extends far outside the plasma column

  10. Optical Fiber Sensing Based on Reflection Laser Spectroscopy

    Directory of Open Access Journals (Sweden)

    Gianluca Gagliardi

    2010-03-01

    Full Text Available An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques. Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy. Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented.

  11. Reflection of attosecond x-ray free electron laser pulses

    International Nuclear Information System (INIS)

    Hau-Riege, Stefan P.; Chapman, Henry N.

    2007-01-01

    In order to utilize hard x-ray free electron lasers (XFEL's) when they are extended to attosecond pulse lengths, it is necessary to choose optical elements with minimal response time. Specular grazing-incidence optics made of low-Z materials are popular candidates for reflectors since they are likely to withstand x-ray damage and provide sufficiently large reflectivities. Using linear-optics reflection theory, we calculated the transient reflectivity of a delta-function electric pulse from a homogenous semi-infinite medium as a function of angle of incidence for s- and p-polarized light. We specifically considered the pulse response of beryllium, diamond, silicon carbide, and silicon, all of which are of relevance to the XFEL's that are currently being built. We found that the media emit energy in a damped oscillatory way, and that the impulse-response times are shorter than 0.3 fs for normal incidence. For grazing incidence, the impulse-response time is substantially shorter, making grazing-incidence mirrors a good choice for deep subfemtosecond reflective optics

  12. The reflection of airborne UV laser pulses from the ocean

    Science.gov (United States)

    Hoge, F. E.; Krabill, W. B.; Swift, R. N.

    1984-01-01

    It is experimentally shown here for the first time that the normalized laser backscatter cross-section of the sea surface is a function of elevation or height position on teh ocean wave. All data were taken off-nadir, resulting in incidence angles of about 6.5 deg measured relative to the normal to mean sea level (MSL). In the limited data sets analyzed to date, the normalized backscatter cross-section was found to be higher in wave crest regions and lower in wave troughs for a swell-dominated sea over which the wind speed was 5 m/s. The reverse was found to be the case for a sea that was driven by a 14 m/s wind. These isolated results show that the MSL, as measured by an off-nadir and/or multibeam type satellite laser altimeter, will be found above, at, or below the true MSL, depending on the local sea conditions existing in the footprint of the altimeter. Airborne nadir-pointed laser altimeter data for a wide variety of sea conditions are needed before a final determination can be made of the effect of sea state on the backscatter cross-section as measured by a down-looking satellite laser system.

  13. Computation of Mach reflection from rigid and yielding surfaces

    International Nuclear Information System (INIS)

    Buckingham, A.C.; Wilson, S.S.

    1976-01-01

    The present discussion centers on a theoretical description of one aspect of the irregular or Mach reflection from solid surfaces. The discussion is restricted to analytical considerations and some preliminary results using model approximations to the surface interaction phenomena. Currently, full numerical simulations of the irregular reflection surface interaction dynamics have not been obtained since the method is still under development. Discussion of the numerical method is, therefore, restricted to some special procedures for the gas-solid surface boundary dynamics. The discussion is divided into an introductory section briefly describing a particular Mach reflection process. Subsequently, some of the considerations on boundary conditions are submitted for numerical treatment of the gas-solid interface. Analysis and discussion of a yielding solid surface subjected to impulsive loading from an intense gas shock wave follows. This is used as a guide for the development of the numerical procedure. Mach reflection processes are then briefly reviewed with special attention for similitude and singular perturbation features

  14. Reduction of short wavelength reflectance of multi-wall carbon nanotubes through ultraviolet laser irradiation

    Science.gov (United States)

    Stephens, Michelle S.; Simonds, Brian J.; Yung, Christopher S.; Conklin, Davis; Livigni, David J.; Oliva, Alberto Remesal; Lehman, John H.

    2018-05-01

    Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications and for stray light control. They are also used as high emittance blackbody radiators. Irradiation of single wall carbon nanotubes with ultraviolet (UV) laser light has been shown to remove amorphous carbon debris, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure reduces the reflectivity at wavelengths below 600 nm and present modeling of the thermal cycling the UV exposure causes at the surface of the carbon nanotubes. This effect can be used to flatten the spectral shape of the reflectivity curve of carbon nanotube absorber coatings used for broadband applications. Finally, we find that the effect of UV exposure depends on the nanotube growth process.

  15. A Method of Retrieving BRDF from Surface-Reflected Radiance Using Decoupling of Atmospheric Radiative Transfer and Surface Reflection

    Directory of Open Access Journals (Sweden)

    Alexander Radkevich

    2018-04-01

    Full Text Available Bi-directional reflection distribution function (BRDF defines anisotropy of the surface reflection. It is required to specify the boundary condition for radiative transfer (RT modeling used in aerosol retrievals, cloud retrievals, atmospheric modeling, and other applications. Ground based measurements of reflected radiance draw increasing attention as a source of information about anisotropy of surface reflection. Derivation of BRDF from surface radiance requires atmospheric correction. This study develops a new method of retrieving BRDF on its whole domain, making it immediately suitable for further atmospheric RT modeling applications. The method is based on the integral equation relating surface-reflected radiance, BRDF, and solutions of two auxiliary atmosphere-only RT problems. The method requires kernel-based BRDF. The weights of the kernels are obtained with a quickly converging iterative procedure. RT modeling has to be done only one time before the start of iterative process.

  16. Laser Surface Hardening of Groove Edges

    Science.gov (United States)

    Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.

    2013-06-01

    Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.

  17. Influence of laser surface modifying of polyethylene terephthalate on fibroblast cell adhesion

    International Nuclear Information System (INIS)

    Mirzadeh, H.; Dadsetan, M.

    2003-01-01

    Attempts have been made to evaluate the changes in physical and chemical properties of the polyethylene terephthalate (PET) surface due to laser irradiation. These changes have been investigated from viewpoints of microstructuring and its effect on fibroblast cell behavior. The surfaces of PET were irradiated using CO 2 and KrF excimer pulsed laser. The changes were characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM) and contact angle measurements. The data from ATR-FTIR spectra showed that the crystallinity in the surface region decreased due to the CO 2 and excimer laser irradiation. SEM observations showed that specific microstructures were created on the PET surface due to laser irradiation. In order to study biocompatibility and cell behavior, we utilized standard in vitro L929-fibroblast cell culture system. Fibroblast cell adhesion and spreading were significantly correlated to the morphology and wettability of the laser irradiated PET surface

  18. Surface modification of UHMWPE with infrared femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Pradas, J.M., E-mail: jmfernandez@ub.edu [Departament de Fisica Aplicada i Optica, Universitat de Barcelona Marti i Franques 1, E-08028 Barcelona (Spain); Naranjo-Leon, S.; Morenza, J.L.; Serra, P. [Departament de Fisica Aplicada i Optica, Universitat de Barcelona Marti i Franques 1, E-08028 Barcelona (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Ultra High Molecular Weight Polyethylene surface was modified with femtosecond laser pulses at 1027 nm wavelength. Black-Right-Pointing-Pointer Surface roughness is increased. Black-Right-Pointing-Pointer Ablation efficiency is maximum for 6 {mu}J pulses. Black-Right-Pointing-Pointer Irradiated surfaces remain almost chemically unaltered. - Abstract: Ultra-high-molecular-weight polyethylene (UHMWPE) is a polymer with mechanical and corrosion properties, which make it appropriate for using in biomedical devices such as hip and knee prostheses. The surface morphology and chemistry of UHMWPE influence its biocompatibility. A laser with wavelength at 1027 nm delivering 450 fs pulses at a repetition rate of 1 kHz is used to modify the surface of UHMWPE samples with 0.45 {mu}m root mean square surface roughness. Micrometric resolution is achieved with the use of a focusing lens of 0.25 NA and pulse energies of few microjoules. The study focuses in the influence of different pulse energies and pulse overlaps on the laser-induced surface roughness and ablation yield. Confocal microscopy is used to characterize changes in the morphology of the irradiated surfaces, and their chemical structure is analyzed by attenuated total reflectance infrared and Raman spectroscopies. The roughness increases as the pulse energy increases until it reaches a maximum. The ablation yield increases with the pulse energy and pulse overlap. However, the ablation yield per pulse is lower for higher pulse overlap. Pulses of 6 {mu}J have the highest ablation efficiency. Infrared and Raman spectra of samples irradiated with low energy pulses are similar to those of the pristine sample. However, some C=C and C=O bonds can be detected after irradiation with the highest pulse energies.

  19. Nanoscale surface characterization using laser interference microscopy

    Science.gov (United States)

    Ignatyev, Pavel S.; Skrynnik, Andrey A.; Melnik, Yury A.

    2018-03-01

    Nanoscale surface characterization is one of the most significant parts of modern materials development and application. The modern microscopes are expensive and complicated tools, and its use for industrial tasks is limited due to laborious sample preparation, measurement procedures, and low operation speed. The laser modulation interference microscopy method (MIM) for real-time quantitative and qualitative analysis of glass, metals, ceramics, and various coatings has a spatial resolution of 0.1 nm for vertical and up to 100 nm for lateral. It is proposed as an alternative to traditional scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. It is demonstrated that in the cases of roughness metrology for super smooth (Ra >1 nm) surfaces the application of a laser interference microscopy techniques is more optimal than conventional SEM and AFM. The comparison of semiconductor test structure for lateral dimensions measurements obtained with SEM and AFM and white light interferometer also demonstrates the advantages of MIM technique.

  20. On the reflection point where light reflects to a known destination on quadratic surfaces.

    Science.gov (United States)

    Gonçalves, Nuno

    2010-01-15

    We address the problem of determining the reflection point on a specular surface where a light ray that travels from a source to a target is reflected. The specular surfaces considered are those expressed by a quadratic equation. So far, there is no closed form explicit equation for the general solution of this determination of the reflection point, and the usual approach is to use the Snell law or the Fermat principle whose equations are derived in multidimensional nonlinear minimizations. We prove in this Letter that one can impose a set of three restrictions to the reflection point that can impose a set of three restrictions that culminates in a very elegant formalism of searching the reflection point in a unidimensional curve in space. This curve is the intersection of two quadratic equations. Some applications of this framework are also discussed.

  1. Fabrication of multi-functional silicon surface by direct laser writing

    Science.gov (United States)

    Verma, Ashwani Kumar; Soni, R. K.

    2018-05-01

    We present a simple, quick and one-step methodology based on nano-second laser direct writing for the fabrication of micro-nanostructures on silicon surface. The fabricated surfaces suppress the optical reflection by multiple reflection due to light trapping effect to a much lower value than polished silicon surface. These textured surfaces offer high enhancement ability after gold nanoparticle deposition and then explored for Surface Enhanced Raman Scattering (SERS) for specific molecular detection. The effect of laser scanning line interval on optical reflection and SERS signal enhancement ability was also investigated. Our results indicate that low optical reflection substrates exhibit uniform SERS enhancement with enhancement factor of the order of 106. Furthermore, this methodology provide an alternative approach for cost-effective large area fabrication with good control over feature size.

  2. LASER SURFACE CLADDING FOR STRUCTURAL REPAIR

    OpenAIRE

    SANTANU PAUL

    2018-01-01

    Laser cladding is a powder deposition technique, which is used to deposit layers of clad material on a substrate to improve its surface properties. It has widespread application in the repair of dies and molds used in the automobile industry. These molds and dies are subjected to cyclic thermo-mechanical loading and therefore undergo localized damage and wear. The final clad quality and integrity is influenced by various physical phenomena, namely, melt pool morphology, microst...

  3. Micropatterning on cylindrical surfaces via electrochemical etching using laser masking

    International Nuclear Information System (INIS)

    Cho, Chull Hee; Shin, Hong Shik; Chu, Chong Nam

    2014-01-01

    Highlights: • Various micropatterns were fabricated on the cylindrical surface of a stainless steel shaft. • Selective electrochemical dissolution was achieved via a series process of laser masking and electrochemical etching. • Laser masking characteristics on the non-planar surface were investigated. • A uniform mask layer was formed on the cylindrical surface via synchronized laser line scanning with a rotary system. • The characteristics of electrochemical etching on the non-planar surface were investigated. - Abstract: This paper proposes a method of selective electrochemical dissolution on the cylindrical surfaces of stainless steel shafts. Selective electrochemical dissolution was achieved via electrochemical etching using laser masking. A micropatterned recast layer was formed on the surface via ytterbium-doped pulsed fiber laser irradiation. The micropatterned recast layer could be used as a mask layer during the electrochemical etching process. Laser masking condition to form adequate mask layer on the planar surface for etching cannot be used directly on the non-planar surface. Laser masking condition changes depending on the morphological surface. The laser masking characteristics were investigated in order to form a uniform mask layer on the cylindrical surface. To minimize factors causing non-uniformity in the mask layer on the cylindrical surface, synchronized laser line scanning with a rotary system was applied during the laser masking process. Electrochemical etching characteristics were also investigated to achieve deeper etched depth, without collapsing the recast layer. Consequently, through a series process of laser masking and electrochemical etching, various micropatternings were successfully performed on the cylindrical surfaces

  4. [INVITED] Laser treatment of Inconel 718 alloy and surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Al-Aqeeli, N.; Karatas, C.

    2016-04-01

    Laser surface texturing of Inconel 718 alloy is carried out under the high pressure nitrogen assisting gas. The combination of evaporation and melting at the irradiated surface is achieved by controlling the laser scanning speed and the laser output power. Morphological and metallurgical changes in the treated surface are analyzed using the analytical tools including optical, electron scanning, and atomic force microscopes, energy dispersive spectroscopy, and X-ray diffraction. Microhardnes and friction coefficient of the laser treated surface are measured. Residual stress formed in the surface region is determined from the X-ray diffraction data. Surface hydrophobicity of the laser treated layer is assessed incorporating the sessile drop method. It is found that laser treated surface is free from large size asperities including cracks and the voids. Surface microhardness increases significantly after the laser treatment process, which is attributed to the dense layer formation at the surface under the high cooling rates, dissolution of Laves phase in the surface region, and formation of nitride species at the surface. Residual stress formed is compressive in the laser treated surface and friction coefficient reduces at the surface after the laser treatment process. The combination of evaporation and melting at the irradiated surface results in surface texture composes of micro/nano-poles and pillars, which enhance the surface hydrophobicity.

  5. LASER SURFACE MODIFICATION OF TITANIUM ALLOYS — A REVIEW

    OpenAIRE

    Y. S. TIAN; C. Z. CHEN; D. Y. WANG; T. Q. LEI

    2005-01-01

    Recent developments of laser surface modification of titanium alloys for increasing their corrosion, wear and oxidation resistance are introduced. The effects of laser processing parameters on the resulting surface properties of titanium alloys are reviewed. The problems to be solved and the prospects in the field of laser modification of Ti alloys are discussed. Due to the intrinsic properties, a laser beam can be focused onto the metallic surface to produce a broad range of treatments depen...

  6. Effect of reflective surfaces on a greenhouse lettuce crop

    Energy Technology Data Exchange (ETDEWEB)

    Warman, P.R.; Mayhew, W.J.

    1979-01-01

    The Canadian greenhouse industry is an important segment of horticultural production, providing employment for thousands of people. Continuing increases in the costs of conventional fuel supplies, however, has placed the industry in some jeopardy since the cost of heating during the winter months is also escalating. In response to this problem the Brace Research Institute has developed a single roofed greenhouse designed to capture and store the sun's energy, and to increase the amount of downward solar radiation inside the greenhouse through the use of specularly-reflecting back and side walls. The research investigated the effect of a reflective surface on plant growth, development, and nutritional uptake during fall and the early months of winter. The inside walls of the greenhouse were lined with aluminized polyester to act as a reflective surface and flat black roofing felt paper to provide a non-reflecting surface. Grand Rapids Forcing lettuce was planted from seed into a peat-vermiculite bed and total solar radiation was monitored on the horizontal. Over the duration of the experiment, the reflective side of the greenhouse received more than twice as much solar radiation as the non-reflective side leading to significantly larger plant yields on the reflective side. There were no significant differences in the uptake of the plant macronutrients, N, P, K, Ca, and Mg.

  7. Internal reflection spectroscopic analysis of sulphide mineral surfaces

    International Nuclear Information System (INIS)

    Kaoma, J.

    1989-01-01

    To establish the reason for flotation of sulfide minerals in the absence of any conventional collector, internal reflection spectroscopic analysis (IRS) of their surfaces was conducted. sulfur, sulfates, thiosulfates, and hydrocarbonates have been detected on the surface of as-grand sulfide minerals. On sodium sulfide-treated surfaces, both sulfur and polysulfide have also been found to be present. From these findings, the flotation of sulfide minerals without collectors is discussed. (author). 26 refs

  8. Ring cavity surface emitting semiconductor lasers

    International Nuclear Information System (INIS)

    Mujagic, E.

    2010-01-01

    Quantum cascade lasers (QCLs) are electrically driven semiconductor lasers, which have undergone a steady improvement since the first demonstration in 1994. These are now well established as reliable sources of coherent light in the mid-infrared (MIR) and terahertz (THz)range of the electromagnetic spectrum (3-300 μm). The rapid progress of this type of lasers is based on a high degree of freedom in tailoring the emission wavelength within a large variety of semiconductor heterostructure designs and materials. These properties have attracted the attention of various applications such as gas analysis, chemical sensing, spectral imaging and free-space telecommunication. In order to improve the selectivity, sensitivity and efficiency of today's sensor systems, high optical power, continuous wave and room temperature performance, single-mode operation and low divergence optical beams, are highly desirable qualities of a compact laser source in this field of research. Since all of these features cannot be provided by a conventional edge-emitting device at the same time, research has put focus on the development of surface emitting devices. Nowadays, the vertical cavity surface emitting lasers (VCSELs) are the most prominent representative for this type of light emitters. With its capability of producing narrow circular beams, the feasibility of two-dimensional arrays and on-wafer testing, such a coherent light source results in a reduction of the fabrication effort and production costs. Since the radiation in QCLs is strictly polarized normal to the epitaxial layer plane, fabrication of VCSELs based on QC structures is not viable. The subject of this work is the design and realization of 'ring cavity surface emitting lasers' (ring-CSELs). This type of lasers employs a circular ring cavity and a resonant distributed feedback (DFB) surface grating. Ring-CSELs were fabricated on the basis of MIR and THz QC structures, which cover a wavelength range from 4 μm to 93

  9. Topography and Reflectance of Mercury After Two Years of Laser Altimetry

    Science.gov (United States)

    Neumann, G. A.; Sun, X.; Mazarico, E.; Smith, D. E.; Zuber, M. T.; Ernst, C. M.; Barnouin, O. S.; Chabot, N. L.; Paige, D. A.; Solomon, S. C.

    2013-12-01

    The Mercury Laser Altimeter (MLA) on the MESSENGER spacecraft has been ranging to the planet Mercury since March 2011, first in a 12-h, 83.5°-inclination orbit, and currently in an 8-h orbit. The orbital periapsis latitude, initially at 60°N, moved slowly northward during the first two years of the orbital mission, enabling near-complete coverage of the northern hemisphere with ~15 million measured radii. Targeted observations during the first extended mission allowed mapping of nearly all regions of extensive shadow within northern high-latitude craters. The refined topography provides a comprehensive dataset for geological studies, illumination and thermal modeling, and studies of the interior. The strength of laser returns in relation to the 10-20 mJ energy of the outgoing laser pulses has provided ~8.7 million active measurements of surface reflectance. Initial results, in conjunction with neutron spectrometry and Earth-based radar, confirmed the existence of water ice exposed at the surface within the deepest shadows of Prokofiev Crater at 85° N and other regions of high radar cross-section, as well as darker volatile species that provide an insulating surficial layer for most radar-bright polar deposits. Refined measurements of reflectance, corroborated by imaging of shadowed regions illuminated by scattered light, reveal the areal extent of polar deposits. These deposits expose water ice at the surface only in limited regions where surface temperatures are predicted never to exceed the long-term stability limit of water ice, whereas subsurface temperatures in other areas of permanent shadow predict the long-term preservation of more extensive deposits of water ice and other volatiles if that material is overlain by an insulating layer.

  10. Wavelength selectivity of on-axis surface plasmon laser filters

    International Nuclear Information System (INIS)

    Harmer, S W; Townsend, P D

    2002-01-01

    Excitation of surface plasmons on a metal substrate, via the attenuated total reflection method can theoretically offer preferential absorption of light at one particular wavelength, whilst reflecting the nearby spectrum. Normally this 'filtering' action is limited to removal of p-polarized light, and the acceptance angle of such a filtering device is very narrow, which limits practical applications, such as separation of fundamental and laser harmonics. The possibility of avoiding this angular precision is explored by considering the complex permittivity of metal composites. By using a two or more layer structure, as opposed to a single metal substrate, the acceptance angle of the device can be broadened, by a factor of about 15 times. An example is discussed for separation of the fundamental and harmonics from a Nd : YAG laser. Variants of the structure allow the design of an in-line transmission filter for the various wavelengths with sufficient angular tolerance to include focusing lenses. Avoidance of laser ablation of the metal is discussed

  11. Reflection properties of hydrogen ions at helium irradiated tungsten surfaces

    International Nuclear Information System (INIS)

    Doi, K; Tawada, Y; Kato, S; Sasao, M; Kenmotsu, T; Wada, M; Lee, H T; Ueda, Y; Tanaka, N; Kisaki, M; Nishiura, M; Matsumoto, Y; Yamaoka, H

    2016-01-01

    Nanostructured W surfaces prepared by He bombardment exhibit characteristic angular distributions of hydrogen ion reflection upon injection of 1 keV H + beam. A magnetic momentum analyzer that can move in the vacuum chamber has measured the angular dependence of the intensity and the energy of reflected ions. Broader angular distributions were observed for He-irradiated tungsten samples compared with that of the intrinsic polycrystalline W. Both intensity and energy of reflected ions decreased in the following order: the polycrystalline W, the He-bubble containing W, and the fuzz W. Classical trajectory Monte Carlo simulations based on Atomic Collision in Amorphous Target code suggests that lower atom density near the surface can make the reflection coefficients lower due to increasing number of collisions. (paper)

  12. Formation of surface nanolayers in chalcogenide crystals using coherent laser beams

    Science.gov (United States)

    Ozga, K.; Fedorchuk, A. O.; El-Naggar, A. M.; Albassam, A. A.; Kityk, V.

    2018-03-01

    We have shown a possibility to form laser modified surface nanolayers with thickness up to 60 nm in some ternary chalcogenide crystals (Ag3AsS3, Ag3SbS3, Tl3SbS3) The laser treatment was performed by two coherent laser beams split in a space. As the inducing lasers we have applied continuous wave (cw) Hesbnd Cd laser at wavelength 441 nm and doubled frequency cw Nd: YAG laser at 532 nm. The spectral energies of these lasers were higher with respect to the energy gaps of the studied crystals. The optical anisotropy was appeared and defected by monitoring of birefringence at probing wavelength of cw Hesbnd Ne laser at λ = 3390 nm. The changes of the laser stimulated near the surface layer morphology was monitored by TEM and AFM methods as well as by the reflected optical second harmonic generation at fundamental wavelength of microsecond CO2 laser generating at wavelength 10600 nm. This technique may open a new approach for the formation of the near the surface nanolayers in chalcogenides using external cw laser illumination.

  13. Geometrical considerations in analyzing isotropic or anisotropic surface reflections.

    Science.gov (United States)

    Simonot, Lionel; Obein, Gael

    2007-05-10

    The bidirectional reflectance distribution function (BRDF) represents the evolution of the reflectance with the directions of incidence and observation. Today BRDF measurements are increasingly applied and have become important to the study of the appearance of surfaces. The representation and the analysis of BRDF data are discussed, and the distortions caused by the traditional representation of the BRDF in a Fourier plane are pointed out and illustrated for two theoretical cases: an isotropic surface and a brushed surface. These considerations will help characterize either the specular peak width of an isotropic rough surface or the main directions of the light scattered by an anisotropic rough surface without misinterpretations. Finally, what is believed to be a new space is suggested for the representation of the BRDF, which avoids the geometrical deformations and in numerous cases is more convenient for BRDF analysis.

  14. Use of reflectance spectrophotometry to predict the response of port wine stains to pulsed dye laser.

    Science.gov (United States)

    Halachmi, Shlomit; Azaria, Ron; Inbar, Roy; Ad-El, Dean; Lapidoth, Moshe

    2014-01-01

    Reflectance spectroscopy can be used to quantitate subtle differences in color. We applied a portable reflectance spectrometer to determine its utility in the evaluation of pulsed dye laser treatment of port wine stains (PWS) and in prediction of clinical outcome, in a prospective study. Forty-eight patients with PWS underwent one to nine pulsed dye laser treatments. Patient age and skin color as well as PWS surface area, anatomic location, and color were recorded. Pretreatment spectrophotometric measurements were performed. The subjective clinical results of treatment and the quantitative spectrophotometry results were evaluated by two independent teams, and the findings were correlated. The impact of the clinical characteristics on the response to treatment was assessed as well. Patients with excellent to good clinical results of laser treatments had pretreatment spectrophotometric measurements which differed by more than 10%, whereas patients with fair to poor results had spectrophotometric measurements with a difference of of less than 10%. The correlation between the spectrophotometric results and the clinical outcome was 73% (p Spectrophotometry has a higher correlation with clinical outcome and a better predictive value than other nonmeasurable, nonquantitative, dependent variables.

  15. Implementation of real-time multiple reflection and Fresnel absorption of laser beam in keyhole

    International Nuclear Information System (INIS)

    Cho, Jung-Ho; Na, Suck-Joo

    2006-01-01

    A computational analysis of laser keyhole welding is achieved. The main driving force to make the molten pool as a narrow and deep keyhole is the recoil pressure induced by evaporation of the material. Also, the multiple reflection effect on the keyhole wall plays an important role in making the keyhole deeper and raising its total energy absorption rate. Multiple reflection and Fresnel absorption are implemented simultaneously with the proposed ray tracing technique in a discrete grid cell system during the simulation for every single time step. In particular, the Fresnel absorption model is chosen as an energy transfer mechanism from laser beam to workpiece. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity. A pulsed Nd : YAG laser was used for keyhole welding experiments on mild steel plates of 7 mm thickness. It was observed that the generated keyhole maintains its solidified shape without any closing phenomenon both in the experiments and in the simulations

  16. Implementation of real-time multiple reflection and Fresnel absorption of laser beam in keyhole

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jung-Ho; Na, Suck-Joo [Department of Mechanical Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2006-12-21

    A computational analysis of laser keyhole welding is achieved. The main driving force to make the molten pool as a narrow and deep keyhole is the recoil pressure induced by evaporation of the material. Also, the multiple reflection effect on the keyhole wall plays an important role in making the keyhole deeper and raising its total energy absorption rate. Multiple reflection and Fresnel absorption are implemented simultaneously with the proposed ray tracing technique in a discrete grid cell system during the simulation for every single time step. In particular, the Fresnel absorption model is chosen as an energy transfer mechanism from laser beam to workpiece. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity. A pulsed Nd : YAG laser was used for keyhole welding experiments on mild steel plates of 7 mm thickness. It was observed that the generated keyhole maintains its solidified shape without any closing phenomenon both in the experiments and in the simulations.

  17. Reflection of slow hydrogen and helium ions from solid surfaces

    International Nuclear Information System (INIS)

    Akkerman, A.F.

    1978-01-01

    Some characteristics of the proton and helium ion flux (E < 10 keV), reflected from solid surfaces are presented. A 'condensed walk' scheme, previously used for electron transport calculations, was adapted. Results obtained either by the scheme or by a more detailed 'consequent' scheme agreed closely. The presented data permit calculations of the mean energy of reflected particles and other values for various energy and angular distributions of incident particles. (author)

  18. Strain of laser annealed silicon surfaces

    Science.gov (United States)

    Nemanich, R. J.; Haneman, D.

    1982-05-01

    High resolution Raman scattering measurements have been carried out on pulse and continuous-wave laser annealed silicon samples with various surface preparations. These included polished and ion-bombarded wafers, and saw-cut crystals. The pulse annealing treatments were carried out in ultrahigh vacuum and in air. The residual strain was inferred from the frequency shift of the first-order Raman active mode of Si, and was detectable in the range 10-2-10-3 in all except the polished samples.

  19. Quality Assessment of Landsat Surface Reflectance Products Using MODIS Data

    Science.gov (United States)

    Feng, Min; Huang, Chengquan; Channan, Saurabh; Vermote, Eric; Masek, Jeffrey G.; Townshend, John R.

    2012-01-01

    Surface reflectance adjusted for atmospheric effects is a primary input for land cover change detection and for developing many higher level surface geophysical parameters. With the development of automated atmospheric correction algorithms, it is now feasible to produce large quantities of surface reflectance products using Landsat images. Validation of these products requires in situ measurements, which either do not exist or are difficult to obtain for most Landsat images. The surface reflectance products derived using data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS), however, have been validated more comprehensively. Because the MODIS on the Terra platform and the Landsat 7 are only half an hour apart following the same orbit, and each of the 6 Landsat spectral bands overlaps with a MODIS band, good agreements between MODIS and Landsat surface reflectance values can be considered indicators of the reliability of the Landsat products, while disagreements may suggest potential quality problems that need to be further investigated. Here we develop a system called Landsat-MODIS Consistency Checking System (LMCCS). This system automatically matches Landsat data with MODIS observations acquired on the same date over the same locations and uses them to calculate a set of agreement metrics. To maximize its portability, Java and open-source libraries were used in developing this system, and object-oriented programming (OOP) principles were followed to make it more flexible for future expansion. As a highly automated system designed to run as a stand-alone package or as a component of other Landsat data processing systems, this system can be used to assess the quality of essentially every Landsat surface reflectance image where spatially and temporally matching MODIS data are available. The effectiveness of this system was demonstrated using it to assess preliminary surface reflectance products derived using the Global Land Survey (GLS) Landsat

  20. Laser modification of macroscopic properties of metal surface layer

    Science.gov (United States)

    Kostrubiec, Franciszek

    1995-03-01

    Surface laser treatment of metals comprises a number of diversified technological operations out of which the following can be considered the most common: oxidation and rendering surfaces amorphous, surface hardening of steel, modification of selected physical properties of metal surface layers. In the paper basic results of laser treatment of a group of metals used as base materials for electric contacts have been presented. The aim of the study was to test the usability of laser treatment from the viewpoint of requirements imposed on materials for electric contacts. The results presented in the paper refer to two different surface treatment technologies: (1) modification of infusible metal surface layer: tungsten and molybdenum through laser fusing of their surface layer and its crystallization, and (2) modification of surface layer properties of other metals through laser doping of their surface layer with foreign elements. In the paper a number of results of experimental investigations obtained by the team under the author's supervision are presented.

  1. DETERMINING REFLECTANCE SPECTRA OF SURFACES AND CLOUDS ON EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Cowan, Nicolas B.; Strait, Talia E., E-mail: n-cowan@northwestern.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 2131 Tech Dr., IL 60208 (United States)

    2013-03-01

    Planned missions will spatially resolve temperate terrestrial planets from their host star. Although reflected light from such a planet encodes information about its surface, it has not been shown how to establish surface characteristics of a planet without assuming known surfaces to begin with. We present a reanalysis of disk-integrated, time-resolved, multiband photometry of Earth obtained by the Deep Impact spacecraft as part of the EPOXI Mission of Opportunity. We extract reflectance spectra of clouds, ocean, and land without a priori knowledge of the numbers or colors of these surfaces. We show that the inverse problem of extracting surface spectra from such data is a novel and extreme instance of spectral unmixing, a well-studied problem in remote sensing. Principal component analysis is used to determine an appropriate number of model surfaces with which to interpret the data. Shrink-wrapping a simplex to the color excursions of the planet yields a conservative estimate of the planet's endmember spectra. The resulting surface maps are unphysical, however, requiring negative or larger-than-unity surface coverage at certain locations. Our ''rotational unmixing'' supersedes the endmember analysis by simultaneously solving for the surface spectra and their geographical distributions on the planet, under the assumption of diffuse reflection and known viewing geometry. We use a Markov Chain Monte Carlo to determine best-fit parameters and their uncertainties. The resulting albedo spectra are similar to clouds, ocean, and land seen through a Rayleigh-scattering atmosphere. This study suggests that future direct-imaging efforts could identify and map unknown surfaces and clouds on exoplanets.

  2. Earth surface reflectance climatology from 3 years of OMI data

    NARCIS (Netherlands)

    Kleipool, Q.L.; Dobber, M.R.; Haan, de J.F.; Levelt, P.F.

    2008-01-01

    Global maps of the Earth's surface Lambertian equivalent reflectance (LER) are constructed using 3 years of Ozone Monitoring Instrument (OMI) measurements obtained between October 2004 and October 2007 at 23 wavelengths between 328 and 500 nm. The maps are constructed on a 0.5° by 0.5°

  3. Nanoimprinted reflecting gratings for long-range surface plasmon polaritons

    DEFF Research Database (Denmark)

    Pedersen, Rasmus Haugstrup; Boltasseva, Alexandra; Johansen, Dan Mario

    2007-01-01

    We present a novel design, fabrication, and characterization of reflecting gratings for long-range surface plasmon polaritons (LR-SPPs) at telecom wavelengths. LR-SPP waveguides consisting of a thin (12 nm) gold film embedded in a thick (45 μm) layer of dielectric polymer cladding are structured...

  4. An instrument for the measurement of road surface reflection properties

    DEFF Research Database (Denmark)

    Corell, Dennis Dan; Sørensen, K.

    2017-01-01

    Road surface reflection data in the form of standard r-tables serve as input for design calculations of road lighting installations on traffic roads. However, in several countries the use of the standard r-tables has not been verified by measurement in a long period of time, while the types of road...

  5. Copper-assisted, anti-reflection etching of silicon surfaces

    Science.gov (United States)

    Toor, Fatima; Branz, Howard

    2014-08-26

    A method (300) for etching a silicon surface (116) to reduce reflectivity. The method (300) includes electroless deposition of copper nanoparticles about 20 nanometers in size on the silicon surface (116), with a particle-to-particle spacing of 3 to 8 nanometers. The method (300) includes positioning (310) the substrate (112) with a silicon surface (116) into a vessel (122). The vessel (122) is filled (340) with a volume of an etching solution (124) so as to cover the silicon surface (116). The etching solution (124) includes an oxidant-etchant solution (146), e.g., an aqueous solution of hydrofluoric acid and hydrogen peroxide. The silicon surface (116) is etched (350) by agitating the etching solution (124) with, for example, ultrasonic agitation, and the etching may include heating (360) the etching solution (124) and directing light (365) onto the silicon surface (116). During the etching, copper nanoparticles enhance or drive the etching process.

  6. Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

    Science.gov (United States)

    Winslow, Reka M.; Johnson, Catherine L.; Anderson, Brian J.; Gershman, Daniel J.; Raines, Jim M.; Lillis, Robert J.; Korth, Haje; Slavin, James A.; Solomon, Sean C.; Zurbuchen, Thomas H.; hide

    2014-01-01

    Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind.

  7. An instrument for the measurement of road surface reflection properties

    DEFF Research Database (Denmark)

    Corell, Dennis Dan; Sørensen, K.

    2017-01-01

    surfaces in use have changed - for instance to road surface types with less noise from wheel passages. Because of this, a co-operation between the road administrations of the Nordic countries (abbreviated NMF) decided to construct a portable instrument to be used on selections of traffic roads within......Road surface reflection data in the form of standard r-tables serve as input for design calculations of road lighting installations on traffic roads. However, in several countries the use of the standard r-tables has not been verified by measurement in a long period of time, while the types of road...

  8. Repulsive Casimir-Polder potential by a negative reflecting surface

    Science.gov (United States)

    Yuan, Qi-Zhang

    2015-07-01

    We present a scheme to generate an all-range long repulsive Casimir-Polder potential between a perfect negative reflecting surface and a ground-state atom. The repulsive potential is stable and does not decay with time. The Casimir-Polder potential is proportional to z-2 at short atom-surface distances and to z-4 at long atom-surface distances. Because of these advantages, this potential can help in building quantum reflectors, quantum levitating devices, and waveguides for matter waves.

  9. Excitations of surface plasmon polaritons by attenuated total reflection, revisited

    International Nuclear Information System (INIS)

    Barchesi, D.; Otto, A.

    2013-01-01

    Many textbooks and review papers are devoted to plasmonics based on a selection of the numerous bibliography. But none describes the details of the first culmination of plasmonics in 1968, when surface plasmons become a field of optics. The coupling of light with the surface plasmon leads to the surface plasmon polariton (SPP). Therefore, the authors chose to associate historical insight (not avoiding a personal touch), a modern mathematical formulation of the excitation of the SPP by attenuated total reflection (ATR), considered as well understood since decades, and experimental applications since 1969, including recent developments.

  10. The Effect of Glare on Regan Contrast Letter Acuity Scores Using Dye-Based and Reflective Laser Eye Protection

    National Research Council Canada - National Science Library

    Ghani, Nadeem

    2001-01-01

    Current laser eye protection devices (LEPDs) are dye-based or reflective. While both technologies block the laser wavelengths, reflective LEPDs generally transmit more visible light than do dye-based LEPDs...

  11. Spectral curves of surface reflectance in some Antarctic regions

    International Nuclear Information System (INIS)

    Lupi, A.; Tomasi, C.; Orsini, A.; Cacciari, A.; Vitale, V.; Georgiadis, T.; Casacchia, R.; Salvatori, R.; Salvi, S.

    2001-01-01

    Four surface reflectance models of solar radiation were determined by examining several sets of field measurements taken for clear-sky conditions at various sites in Antarctica. Each model consists of the mean spectral curve of surface reflectance in the 0.25-2.7 μm wavelength range and of the dependence curve of total abedo on the solar elevation angle h, within the range from 5 0 to 55 0 . The TNB (Terra Nova Bay) model refers to a rocky terrain where granites are predominant; the NIS (Nansen Ice Sheet) model to a glacier surface made uneven by sastrugi and streaked by irregular fractures; the HAP (High Altitude Plateau) model to a flat ice surface covered by fresh snow and scored by light sastrugi; and the RIS (Ross Ice Shelf) model to an area covered by the sea ice pack presenting many discontinuities in the reflectance features, due to melt water lakes, puddles, refrozen ice and snow pots. The reflectance curve obtained for the TNB model presents gradually increasing values as wavelength increases through the visible spectral range and almost constant values at infrared wavelengths, giving a total albedo value equal to 0.264 at = 30 0 , which increases by about 80% through the lower range of h and decreases by 12% through the upper range. The reflectance curves of the NIS, HAP and RIS models are all peaked at visible wavelengths and exhibit decreasing values throughout the infrared spectral range, giving values of total albedo equal to 0.464, 0.738 and 0.426 at h 30 0 , respectively. These values were estimated to increase by 8-14% as h decreases from 30 0 to 5 0 and to decrease by 2-4% only as h increases from 30 0 to 55 0

  12. Reflectance variability of surface coatings reveals characteristic eigenvalue spectra

    Science.gov (United States)

    Medina, José M.; Díaz, José A.; Barros, Rui

    2012-10-01

    We have examined the trial-to-trial variability of the reflectance spectra of surface coatings containing effect pigments. Principal component analysis of reflectances was done at each detection angle separately. A method for classification of principal components is applied based on the eigenvalue spectra. It was found that the eigenvalue spectra follow characteristic power laws and depend on the detection angle. Three different subsets of principal components were examined to separate the relevant spectral features related to the pigments from other noise sources. Reconstruction of the reflectance spectra by taking only the first subset indicated that reflectance variability was higher at near-specular reflection, suggesting a correlation with the trial-to-trial deposition of effect pigments. Reconstruction by using the second subset indicates that variability was higher at short wavelengths. Finally, reconstruction by using only the third subset indicates that reflectance variability was not totally random as a function of the wavelength. The methods employed can be useful in the evaluation of color variability in industrial paint application processes.

  13. Laser decontamination and cleaning of metal surfaces: modelling and experimental studies

    International Nuclear Information System (INIS)

    Leontyev, A.

    2011-01-01

    Metal surface cleaning is highly required in different fields of modern industry. Nuclear industry seeks for new methods for oxidized surface decontamination, and thermonuclear installations require the cleaning of plasma facing components from tritium-containing deposited layer. The laser ablation is proposed as an effective and safe method for metal surface cleaning and decontamination. The important factor influencing the laser heating and ablation is the in-depth distribution of laser radiation. The model of light propagation in a scattering layer on a metal substrate is developed and applied to analyse the features of light distribution. To simulate the contaminated surfaces, the stainless steel AISI 304L was oxidized by laser and in a furnace. Radioactive contamination of the oxide layer was simulated by introducing europium and/or sodium. The decontamination factor of more than 300 was demonstrated with found optimal cleaning regime. The decreasing of the corrosion resistance was found after laser cleaning. The ablation thresholds of ITER-like surfaces were measured. The cleaning productivity of 0.07 m 2 /hour.W was found. For mirror surfaces, the damage thresholds were determined to avoid damage during laser cleaning. The possibility to restore reflectivity after thin carbon layer deposition was demonstrated. The perspectives of further development of laser cleaning are discussed. (author) [fr

  14. Simultaneous time-space resolved reflectivity and interferometric measurements of dielectrics excited with femtosecond laser pulses

    Science.gov (United States)

    Garcia-Lechuga, M.; Haahr-Lillevang, L.; Siegel, J.; Balling, P.; Guizard, S.; Solis, J.

    2017-06-01

    Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results have been simulated in the frame of a multiple-rate equation model including light propagation. The comparison of the temporal evolution of the reflectivity and the interferometric measurements at 400 nm clearly shows that the two techniques interrogate different material volumes during the course of the process. While the former is sensitive to the evolution of the plasma density in a very thin ablating layer at the surface, the second yields an averaged plasma density over a larger volume. It is shown that self-trapped excitons do not appreciably contribute to carrier relaxation in fused silica at fluences above the ablation threshold, most likely due to Coulomb screening effects at large excited carrier densities. For both materials, at fluences well above the ablation threshold, the maximum measured plasma reflectivity shows a saturation behavior consistent with a scattering rate proportional to the plasma density in this fluence regime. Moreover, for both materials and for pulse energies above the ablation threshold and delays in the few tens of picoseconds range, a simultaneous "low reflectivity" and "low transmission" behavior is observed. Although this behavior has been identified in the past as a signature of femtosecond laser-induced ablation, its origin is alternatively discussed in terms of the optical properties of a material undergoing strong isochoric heating, before having time to substantially expand or exchange energy with the surrounding media.

  15. Effect of laser parameters on surface roughness of laser modified tool steel after thermal cyclic loading

    Science.gov (United States)

    Lau Sheng, Annie; Ismail, Izwan; Nur Aqida, Syarifah

    2018-03-01

    This study presents the effects of laser parameters on the surface roughness of laser modified tool steel after thermal cyclic loading. Pulse mode Nd:YAG laser was used to perform the laser surface modification process on AISI H13 tool steel samples. Samples were then treated with thermal cyclic loading experiments which involved alternate immersion in molten aluminium (800°C) and water (27°C) for 553 cycles. A full factorial design of experiment (DOE) was developed to perform the investigation. Factors for the DOE are the laser parameter namely overlap rate (η), pulse repetition frequency (f PRF) and peak power (Ppeak ) while the response is the surface roughness after thermal cyclic loading. Results indicate the surface roughness of the laser modified surface after thermal cyclic loading is significantly affected by laser parameter settings.

  16. Surface wettability of silicon substrates enhanced by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Shih-Feng [National Applied Research Laboratories, Instrument Technology Research Center, Hsinchu (China); National Chiao Tung University, Department of Mechanical Engineering, Hsinchu (China); Hsiao, Wen-Tse; Huang, Kuo-Cheng; Hsiao, Sheng-Yi [National Applied Research Laboratories, Instrument Technology Research Center, Hsinchu (China); Chen, Ming-Fei [National Changhua University of Education, Department of Mechatronics Engineering, Changhua (China); Lin, Yung-Sheng [Hungkuang University, Department of Applied Cosmetology and Graduate Institute of Cosmetic Science, Taichung (China); Chou, Chang-Pin [National Chiao Tung University, Department of Mechanical Engineering, Hsinchu (China)

    2010-11-15

    Laser-ablation techniques have been widely applied for removing material from a solid surface using a laser-beam irradiating apparatus. This paper presents a surface-texturing technique to create rough patterns on a silicon substrate using a pulsed Nd:YAG laser system. The different degrees of microstructure and surface roughness were adjusted by the laser fluence and laser pulse duration. A scanning electron microscope (SEM) and a 3D confocal laser-scanning microscope are used to measure the surface micrograph and roughness of the patterns, respectively. The contact angle variations between droplets on the textured surface were measured using an FTA 188 video contact angle analyzer. The results indicate that increasing the values of laser fluence and laser pulse duration pushes more molten slag piled around these patterns to create micro-sized craters and leads to an increase in the crater height and surface roughness. A typical example of a droplet on a laser-textured surface shows that the droplet spreads very quickly and almost disappears within 0.5167 s, compared to a contact angle of 47.9 on an untextured surface. This processing technique can also be applied to fabricating Si solar panels to increase the absorption efficiency of light. (orig.)

  17. Metallic surfaces decontamination by using laser light

    International Nuclear Information System (INIS)

    Moggia, Fabrice; Lecardonnel, Xavier

    2013-01-01

    Metal surface cleaning appears to be one of the major priorities for industries especially for nuclear industries. The research and the development of a new technology that is able to meet the actual requirements (i.e. waste volume minimization, liquid effluents and chemicals free process...) seems to be the main commitment. Currently, a wide panel of technologies already exists (e.g. blasting, disk sander, electro-decontamination...) but for some of them, the efficiency is limited (e.g, Dry Ice blasting) and for others, the wastes production (liquid and/or solid) remains an important issue. One answer could be the use of a LASER light process. Since a couple of years, the Clean- Up Business Unit of the AREVA group investigates this decontamination technology. Many tests have been already performed in inactive (i.e. on simulants such as paints, inks, resins, metallic oxides) or active conditions (i.e. pieces covered with a thick metallic oxide layer and metallic pieces covered with grease). The paper will describe the results obtained in term of decontamination efficiency during all our validation process. Metallographic characterizations (i.e. SEM, X-ray scattering) and radiological analysis will be provided. We will also focus our paper on the future deployment of the LASER technology and its commercial use at La Hague reprocessing facility in 2013. (authors)

  18. GLOBAL LAND COVER CLASSIFICATION USING MODIS SURFACE REFLECTANCE PROSUCTS

    Directory of Open Access Journals (Sweden)

    K. Fukue

    2016-06-01

    Full Text Available The objective of this study is to develop high accuracy land cover classification algorithm for Global scale by using multi-temporal MODIS land reflectance products. In this study, time-domain co-occurrence matrix was introduced as a classification feature which provides time-series signature of land covers. Further, the non-parametric minimum distance classifier was introduced for timedomain co-occurrence matrix, which performs multi-dimensional pattern matching for time-domain co-occurrence matrices of a classification target pixel and each classification classes. The global land cover classification experiments have been conducted by applying the proposed classification method using 46 multi-temporal(in one year SR(Surface Reflectance and NBAR(Nadir BRDF-Adjusted Reflectance products, respectively. IGBP 17 land cover categories were used in our classification experiments. As the results, SR and NBAR products showed similar classification accuracy of 99%.

  19. Unmanned aerial system nadir reflectance and MODIS nadir BRDF-adjusted surface reflectances intercompared over Greenland

    Science.gov (United States)

    Faulkner Burkhart, John; Kylling, Arve; Schaaf, Crystal B.; Wang, Zhuosen; Bogren, Wiley; Storvold, Rune; Solbø, Stian; Pedersen, Christina A.; Gerland, Sebastian

    2017-07-01

    Albedo is a fundamental parameter in earth sciences, and many analyses utilize the Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF)/albedo (MCD43) algorithms. While derivative albedo products have been evaluated over Greenland, we present a novel, direct comparison with nadir surface reflectance collected from an unmanned aerial system (UAS). The UAS was flown from Summit, Greenland, on 210 km transects coincident with the MODIS sensor overpass on board the Aqua and Terra satellites on 5 and 6 August 2010. Clear-sky acquisitions were available from the overpasses within 2 h of the UAS flights. The UAS was equipped with upward- and downward-looking spectrometers (300-920 nm) with a spectral resolution of 10 nm, allowing for direct integration into the MODIS bands 1, 3, and 4. The data provide a unique opportunity to directly compare UAS nadir reflectance with the MODIS nadir BRDF-adjusted surface reflectance (NBAR) products. The data show UAS measurements are slightly higher than the MODIS NBARs for all bands but agree within their stated uncertainties. Differences in variability are observed as expected due to different footprints of the platforms. The UAS data demonstrate potentially large sub-pixel variability of MODIS reflectance products and the potential to explore this variability using the UAS as a platform. It is also found that, even at the low elevations flown typically by a UAS, reflectance measurements may be influenced by haze if present at and/or below the flight altitude of the UAS. This impact could explain some differences between data from the two platforms and should be considered in any use of airborne platforms.

  20. Implementation of solar-reflective surfaces: Materials and utility programs

    Energy Technology Data Exchange (ETDEWEB)

    Bretz, S.; Akbari, H.; Rosenfeld, A.; Taha, H.

    1992-06-01

    This report focuses on implementation issues for using solar-reflective surfaces to cool urban heat islands, with specific examples for Sacramento, California. Advantages of solar-reflective surfaces for reducing energy use are: (1) they are cost-effective if albedo is increased during routine maintenance; (2) the energy savings coincide with peak demand for power; (3) there are positive effects on environmental quality; and (4) the white materials have a long service life. Important considerations when choosing materials for mitigating heat islands are identified as albedo, emissivity, durability, cost, pollution and appearance. There is a potential for increasing urban albedo in Sacramento by an additional 18%. Of residential roofs, we estimate that asphalt shingle and modified bitumen cover the largest area, and that built-up roofing and modified bitumen cover the largest area of commercial buildings. For all of these roof types, albedo may be increased at the time of re-roofing without any additional cost. When a roof is repaired, a solar-reflective roof coating may be applied to significantly increase albedo and extend the life of the root Although a coating may be cost-effective if applied to a new roof following installation or to an older roof following repair, it is not cost-effective if the coating is applied only to save energy. Solar-reflective pavement may be cost-effective if the albedo change is included in the routine resurfacing schedule. Cost-effective options for producing light-colored pavement may include: (1) asphalt concrete, if white aggregate is locally available; (2) concrete overlays; and (3) newly developed white binders and aggregate. Another option may be hot-rolled asphalt, with white chippings. Utilities could promote solar-reflective surfaces through advertisement, educational programs and cost-sharing of road resurfacing.

  1. Duplex stainless steel surface bay laser cladding

    International Nuclear Information System (INIS)

    Amigo, V.; Pineda, Y.; Segovia, F.; Vicente, A.

    2004-01-01

    Laser cladding is one of the most promising techniques to restore damaged surfaces and achieve properties similar to those of the base metal. In this work, duplex stainless steels have been cladded by a nickel alloy under different processing conditions. The influence of the beam speed and defocusing variables ha been evaluated in the microstructure both of the cladding and heat affected zone, HAZ. These results have been correlated to mechanical properties by means of microhardness measurements from cladding area to base metal through the interface. This technique has shown to be very appropriate to obtain controlled mechanical properties as they are determined by the solidification microstructure, originated by the transfer of mass and heat in the system. (Author) 21 refs

  2. Laser ablation surface-enhanced Raman microspectroscopy.

    Science.gov (United States)

    Londero, Pablo S; Lombardi, John R; Leona, Marco

    2013-06-04

    Improved identification of trace organic compounds in complex matrixes is critical for a variety of fields such as material science, heritage science, and forensics. Surface-enhanced Raman scattering (SERS) is a vibrational spectroscopy technique that can attain single-molecule sensitivity and has been shown to complement mass spectrometry, but lacks widespread application without a robust method that utilizes the effect. We demonstrate a new, highly sensitive, and widely applicable approach to SERS analysis based on laser ablation in the presence of a tailored plasmonic substrate. We analyze several challenging compounds, including non-water-soluble pigments and dyed leather from an ancient Egyptian chariot, achieving sensitivity as high as 120 amol for a 1:1 signal-to-noise ratio and 5 μm spatial resolution. This represents orders of magnitude improvement in spatial resolution and sensitivity compared to those of other SERS approaches intended for widespread application, greatly increasing the applicability of SERS.

  3. Surface modifications induced by pulsed-laser texturing—Influence of laser impact on the surface properties

    Energy Technology Data Exchange (ETDEWEB)

    Costil, S., E-mail: sophie.costil@utbm.fr [IRTES-LERMPS, Université de Technologie de Belfort - Montbéliard, site de Sévenans, 90010 Belfort Cedex (France); Lamraoui, A.; Langlade, C. [IRTES-LERMPS, Université de Technologie de Belfort - Montbéliard, site de Sévenans, 90010 Belfort Cedex (France); Heintz, O.; Oltra, R. [ICB, Université de Bourgogne, 21078 Dijon Cedex (France)

    2014-01-01

    Laser cleaning technology provides a safe, environmentally friendly and very cost effective way to improve cleaning and surface preparation of metallic materials. Compared with efficient cleaning processes, it can avoid the disadvantages of ductile materials prepared by conventional technologies (cracks induced by sand-blasting for example) and treat only some selected areas (due to the optical fibers). By this way, laser technology could have several advantages and expand the range of thermal spraying. Moreover, new generations of lasers (fiber laser, disc laser) allow the development of new methods. Besides a significant bulk reduction, no maintenance, low operating cost, laser fibers can introduce alternative treatments. Combining a short-pulse laser with a scanner allows new applications in terms of surface preparation. By multiplying impacts using scanning laser, it is possible to shape the substrate surface to improve the coating adhesion as well as the mechanical behaviour. In addition, during the interactions of the laser beam with metallic surfaces, several modifications can be induced and particularly thermal effects. Indeed, under ambient conditions, a limited oxidation of the clean surface can occur. This phenomenon has been investigated in detail for silicon but few works have been reported concerning metallic materials. This paper aims at studying the surface modifications induced on aluminium alloy substrates after laser texturing. After morphological observations (SEM), a deeper surface analysis will be performed using XPS (X-ray photoelectron spectroscopy) measures and microhardness testing.

  4. Laser grooving of surface cracks on hot work tool steel

    Directory of Open Access Journals (Sweden)

    D. Klobčar

    2011-10-01

    Full Text Available The paper presents the analysis of laser grooving of 1.2343 tool steel hardened to 46 HRC. The effect of laser power and grooving speed on groove shape (i.e. depth and width, the material removal rate and the purity of produced groove as a measure of groove quality was investigated and analyzed using response surface methodology. Optimal parameters of laser grooving were found, which enables pure grooves suitable for laser welding.

  5. Comparative study between fundus autofluorescence and red reflectance imaging of choroidal nevi using ultra-wide-field scanning laser ophthalmoscopy.

    Science.gov (United States)

    Zapata, Miguel Angel; Leila, Mahmoud; Teixidor, Teresa; Garcia-Arumi, Jose

    2015-06-01

    To explore the utility of fundus autofluorescence (FAF) and red reflectance (RR) imaging using ultra-wide-field scanning laser ophthalmoscope in choroidal nevi. Retrospective observational case study reviewing clinical data, color, FAF, and RR images of patients with choroidal nevi and comparing the findings. The ultra-wide-field scanning laser ophthalmoscope uses green laser 532 nm and red laser 633 nm that enabled FAF and RR imaging, respectively in separate channels. Superimposition of both images yielded a composite color image. The study included 46 eyes of 45 patients. Nevi were unilateral in 44 patients (98%). Forty-one nevi (89.1%) were located temporally between the macula and the equator. All nevi (100%) were deeply pigmented. The most frequent surface changes were lipofuscin pigments, zones of retinal pigment epithelium atrophy, and retinal pigment epithelium pigment clumps in 31 (67.3%), 18 (39.1%), and 8 eyes (17.3%), respectively. Color photographs were superior to FAF in detecting nevus boundaries and surface changes. Red reflectance correlated strongly with color images, although the nevus boundaries and surface changes were better delineated in RR mode. Red reflectance was superior to FAF in delineating the boundaries and surface changes of the nevus; clear visibility (3+) for RR versus no or poor visibility (0/1+) for FAF. Nevertheless, the areas of retinal pigment epithelium atrophy were better delineated in FAF mode; clear visibility (3+) for FAF versus poor visibility (1+) for FAF. Red reflectance imaging is more sensitive than conventional photography for follow-up of choroidal nevi. Fundus autofluorescence should be considered only as a complementary tool to RR imaging.

  6. Micro-Bulges Investigation on Laser Modified Tool Steel Surface

    Directory of Open Access Journals (Sweden)

    Fauzun Fazliana

    2017-01-01

    Full Text Available This paper presents micro-bulges investigation on laser modified tool steel. The aim of this study is to understand the effect of laser irradiance and interaction time on surface morphology configuration. An Nd:YAG laser system with TEM00 pulse processing mode was used to modify the samples. Metallographic study shows samples were analyzed for focal position effect on melted pool size, angle of peaks geometry and laser modified layer depth. Surface morphology were analyzed for surface roughness. Laser modified layer shows depth ranged between 42.22 and 420.12 μm. Angle of peak bulge was found to be increase with increasing peak power. The maximum roughness, Ra, achieved in modified H13 was 21.10 μm. These findings are significant to enhance surface properties of laser modified steel and cast iron for dies and high wear resistance applications.

  7. Real-time defect detection on highly reflective curved surfaces

    Science.gov (United States)

    Rosati, G.; Boschetti, G.; Biondi, A.; Rossi, A.

    2009-03-01

    This paper presents an automated defect detection system for coated plastic components for the automotive industry. This research activity came up as an evolution of a previous study which employed a non-flat mirror to illuminate and inspect high reflective curved surfaces. According to this method, the rays emitted from a light source are conveyed on the surface under investigation by means of a suitably curved mirror. After the reflection on the surface, the light rays are collected by a CCD camera, in which the coating defects appear as shadows of various shapes and dimensions. In this paper we present an evolution of the above-mentioned method, introducing a simplified mirror set-up in order to reduce the costs and the complexity of the defect detection system. In fact, a set of plane mirrors is employed instead of the curved one. Moreover, the inspection of multiple bend radius parts is investigated. A prototype of the machine vision system has been developed in order to test this simplified method. This device is made up of a light projector, a set of plane mirrors for light rays reflection, a conveyor belt for handling components, a CCD camera and a desktop PC which performs image acquisition and processing. Like in the previous system, the defects are identified as shadows inside a high brightness image. At the end of the paper, first experimental results are presented.

  8. Laser ablation method for cleaning of mirror surfaces for optical diagnostic systems at the ITER

    International Nuclear Information System (INIS)

    Aleksandrova, A.S.; Kuznetsov, A.P.; Gubskij, K.L.; Petrovskij, V.N.; Savelov, A.S.; Shtamm, V.G.; Buzhinskij, O.I.

    2012-01-01

    The possibility of cleaning metallic mirrors from films with complex composition by pulsed radiation from a fiber laser has been experimentally examined. It has been shown that the high initial reflection characteristics of optical elements can be recovered by choosing regimes of the action of radiation on the surface with a deposited film [ru

  9. Ray splitting in the reflection and refraction of surface acoustic waves in anisotropic solids.

    Science.gov (United States)

    Every, A G; Maznev, A A

    2010-05-01

    This paper examines the conditions for, and provides examples of, ray splitting in the reflection and refraction of surface acoustic waves (SAW) in elastically anisotropic solids at straight obstacles such as edges, surface breaking cracks, and interfaces between different solids. The concern here is not with the partial scattering of an incident SAW's energy into bulk waves, but with the occurrence of more than one SAW ray in the reflected and/or transmitted wave fields, by analogy with birefringence in optics and mode conversion of bulk elastic waves at interfaces. SAW ray splitting is dependent on the SAW slowness curve possessing concave regions, which within the constraint of wave vector conservation parallel to the obstacle allows multiple outgoing SAW modes for certain directions of incidence and orientation of obstacle. The existence of pseudo-SAW for a given surface provides a further channel for ray splitting. This paper discusses some typical material configurations for which SAW ray splitting occurs. An example is provided of mode conversion entailing backward reflection or negative refraction. Experimental demonstration of ray splitting in the reflection of a laser generated SAW in GaAs(111) is provided. The calculation of SAW mode conversion amplitudes lies outside the scope of this paper.

  10. Improving Image Matching by Reducing Surface Reflections Using Polarising Filter Techniques

    Science.gov (United States)

    Conen, N.; Hastedt, H.; Kahmen, O.; Luhmann, T.

    2018-05-01

    In dense stereo matching applications surface reflections may lead to incorrect measurements and blunders in the resulting point cloud. To overcome the problem of disturbing reflexions polarising filters can be mounted on the camera lens and light source. Reflections in the images can be suppressed by crossing the polarising direction of the filters leading to homogeneous illuminated images and better matching results. However, the filter may influence the camera's orientation parameters as well as the measuring accuracy. To quantify these effects, a calibration and an accuracy analysis is conducted within a spatial test arrangement according to the German guideline VDI/VDE 2634.1 (2002) using a DSLR with and without polarising filter. In a second test, the interior orientation is analysed in more detail. The results do not show significant changes of the measuring accuracy in object space and only very small changes of the interior orientation (Δc ≤ 4 μm) with the polarising filter in use. Since in medical applications many tiny reflections are present and impede robust surface measurements, a prototypic trinocular endoscope is equipped with polarising technique. The interior and relative orientation is determined and analysed. The advantage of the polarising technique for medical image matching is shown in an experiment with a moistened pig kidney. The accuracy and completeness of the resulting point cloud can be improved clearly when using polarising filters. Furthermore, an accuracy analysis using a laser triangulation system is performed and the special reflection properties of metallic surfaces are presented.

  11. Reflectivity of transient Bragg reflection gratings in fiber laser with laser-wavelength self-sweeping: erratum

    Czech Academy of Sciences Publication Activity Database

    Peterka, Pavel; Honzátko, Pavel; Koška, Pavel; Todorov, Filip; Aubrecht, Jan; Podrazký, Ondřej; Kašík, Ivan

    2016-01-01

    Roč. 24, č. 14 (2016), s. 16222-16223 ISSN 1094-4087 R&D Projects: GA ČR(CZ) GA16-13306S Institutional support: RVO:67985882 Keywords : Ytterbium-doped fiber * Laser optics * Q switched lasers Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.307, year: 2016

  12. High-efficient Nd:YAG microchip laser for optical surface scanning

    Science.gov (United States)

    Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

    2017-12-01

    A CW operating, compact, high-power, high-efficient diode pumped 1064nm laser, based on Nd:YAG active medium, was developed for optical surface scanning and mapping applications. To enhance the output beam quality, laser stability, and compactness, a microchip configuration was used. In this arrangement the resonator mirrors were deposited directly on to the laser crystal faces. The Nd-doping concentration was 1 at.% Nd/Y. The Nd:YAG crystal was 5mm long. The laser resonator without pumping radiation recuperation was investigated {the output coupler was transparent for pumping radiation. For the generated laser radiation the output coupler reflectivity was 95%@1064 nm. The diameter of the samples was 5 mm. For the laser pumping two arrangements were investigated. Firstly, a fibre coupled laser diode operating at wavelength 808nm was used in CW mode. The 400 ¹m fiber was delivering up to 14W of pump power amplitude to the microchip laser. The maximum CW output power of 7.2W @ 1064nm in close to TEM00 beam was obtained for incident pumping power 13.7W @ 808 nm. The differential efficiency in respect to the incident pump power reached 56 %. Secondly, a single-emitter, 1W laser diode operating at 808nm was used for Nd:YAG microchip pumping. The laser pumping was directly coupled into the microchip laser using free-space lens optics. Slope efficiency up to 70% was obtained in stable, high-quality, 1064nm laser beam with CW power up to 350mW. The system was successfully used for scanning of super-Gaussian laser mirrors reflectivity profile.

  13. Three body abrasion of laser surface alloyed aluminium AA1200

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2012-06-01

    Full Text Available Laser surface alloying of aluminium AA1200 was performed with a 4 kW Nd:YAG laser to improve the abrasion wear resistance. Aluminium surfaces reinforced with metal matrix composites and intermetallic phases were achieved. The phases present depended...

  14. Self-reflection and self-transmission of pulsed radiation by laser-evaporated media

    Science.gov (United States)

    Furzikov, Nickolay P.

    1991-05-01

    Analysis of the known laser-induced evaporation (thermodestruction) model predicts the quasiperiodic oscillation of the effective absorption depth between its normal value and some minute quantity consisting of a part of the incident wavelength. This prediction explains the experimental data on the polymer laser ablation depth as well as the reflection transient drop of the laserdestructed aluminum.

  15. Modeling and validation of multiple joint reflections for ultra- narrow gap laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Milewski, J.; Keel, G. [Los Alamos National Lab., NM (United States); Sklar, E. [Opticad Corp., Santa Fe, New Mexico (United States)

    1995-12-01

    The effects of multiple internal reflections within a laser weld joint as a function of joint geometry and processing conditions have been characterized. A computer model utilizing optical ray tracing is used to predict the reflective propagation of laser beam energy focused into the narrow gap of a metal joint for the purpose of predicting the location of melting and coalescence which form the weld. The model allows quantitative analysis of the effects of changes to joint geometry, laser design, materials and processing variables. This analysis method is proposed as a way to enhance process efficiency and design laser welds which display deep penetration and high depth to width aspect ratios, reduced occurrence of defects and enhanced melting. Of particular interest to laser welding is the enhancement of energy coupling to highly reflective materials. The weld joint is designed to act as an optical element which propagates and concentrates the laser energy deep within the joint to be welded. Experimentation has shown that it is possible to produce welds using multiple passes to achieve deep penetration and high depth to width aspect ratios without the use of filler material. The enhanced laser melting and welding of aluminum has been demonstrated. Optimization through modeling and experimental validation has resulted in the development of a laser welding process variant we refer to as Ultra-Narrow Gap Laser Welding.

  16. An investigation of laser processing of silica surfaces

    International Nuclear Information System (INIS)

    Weber, A.J.; Stewart, A.F.; Exarhos, G.J.; Stowell, W.K.

    1988-01-01

    An initial set of experiments has been conducted to determine the practicality of laser processing of optical substrates. In contrast to earlier work, a high average power CO 2 laser was used to flood load the entire surface of each test sample. Fused silica substrates were laser polished on both surfaces at power densities ranging from 150 to 350 W/cm 2 . During each test sequence sample surface temperatures were recorded using a thermal imaging system. Extensive pre- and post-test characterization revealed that surface roughness and scattering of bare silica surfaces were reduced while internal stress increased. Laser damage thresholds were found to increase only for certain conditions. Changes in the microstructure were observed. These preliminary experiments demonstrate that laser processing can dramatically improve the optical properties of fused silica substrates

  17. Laser induced damage threshold on metallic surfaces during laser cleaning

    CSIR Research Space (South Africa)

    Labuschagne, K

    2005-07-01

    Full Text Available laser paint removal. Laser induced damage on 316L stainless steel was studied, with the target subjected to single and multiple pulse irradiations using a Q-switched Nd:YAG, with fluences between 0.15 and 11.8 J/cm2. Several different damage morphologies...

  18. Surface improvement for inside surface of small diameter pipes by laser cladding technique

    International Nuclear Information System (INIS)

    Irisawa, Toshio; Morishige, Norio; Umemoto, Tadahiro; Ono, Kazumichi; Hamaoka, Tadashi; Tanaka, Atsushi

    1991-01-01

    A laser cladding technique has been used for surface improvement in controlling the composition of a metal surface. Recent high power YAG laser development gives an opportunity to use this laser cladding technique for various applications. A YAG laser beam can be transmitted through an optical fiber for a long distance and through narrow spaces. YAG laser cladding was studied for developing alloy steel to prevent stress corrosion cracking in austenitic stainless steel piping. In order to make a cladding layer, mixed metal powder was on the inside surface of the piping using an organic binder. Subsequently the powder beds were melted with a YAG laser beam transmitted through an optical fiber. This paper introduces the Laser cladding technique for surface improvement for the inside surface of a small diameter pipe. (author)

  19. Anti-reflection textured structures by wet etching and island lithography for surface-enhanced Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Bo-Kai [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Cheng, Hsin-Hung [Department of Marine Engineering, Taipei College of Maritime Technology, Taipei 11174, Taiwan (China); Nien, Li-Wei; Chen, Miin-Jang [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Nagao, Tadaaki [Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Li, Jia-Han [Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Hsueh, Chun-Hway, E-mail: hsuehc@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

    2015-12-01

    Graphical abstract: - Highlights: • We fabricated textured SERS substrate with a high surface area and low reflectance. • Large surface area of substrate contains more gold nanodroplets to absorb analytes. • Low reflectance of textured SERS substrate enabled multiple reflections of incident laser light. • We obtained strong SERS enhancement from nanopillar-on-pyramid SERS substrate. - Abstract: A high surface area and low reflection textured surface-enhanced Raman scattering (SERS) substrate with plasmonic gold nanodroplets fabricated by wet etching and island lithography was reported in the present study. Specifically, four textured substrates, planar, pyramid, nanopillar, and nanopillar-on-pyramid, were fabricated. The fabricated structures were simulated using the finite-difference time-domain method and the results agreed with the reflection and dark-field scattering measurements. Although the SERS signals varied in different measured regions because of the random nanostructure, the SERS substrates with nanopillar-on-pyramid structure always have the stronger enhancement factor than the SERS substrates with only pyramids or nanopillars. Based on the atomic force microscope and reflection measurements, the nanopillar-on-pyramid structure provided a large surface area and multiple reflections for SERS enhancement, which was about 3 orders of magnitude larger than that of the planar substrate. Our results can be applied to fabricate the inexpensive, large surface area, and high SERS enhancement substrates.

  20. Research on effect of rough surface on FMCW laser radar range accuracy

    Science.gov (United States)

    Tao, Huirong

    2018-03-01

    The non-cooperative targets large scale measurement system based on frequency-modulated continuous-wave (FMCW) laser detection and ranging technology has broad application prospects. It is easy to automate measurement without cooperative targets. However, the complexity and diversity of the surface characteristics of the measured surface directly affects the measurement accuracy. First, the theoretical analysis of range accuracy for a FMCW laser radar was studied, the relationship between surface reflectivity and accuracy was obtained. Then, to verify the effect of surface reflectance for ranging accuracy, a standard tool ball and three standard roughness samples were measured within 7 m to 24 m. The uncertainty of each target was obtained. The results show that the measurement accuracy is found to increase as the surface reflectivity gets larger. Good agreements were obtained between theoretical analysis and measurements from rough surfaces. Otherwise, when the laser spot diameter is smaller than the surface correlation length, a multi-point averaged measurement can reduce the measurement uncertainty. The experimental results show that this method is feasible.

  1. Measurements of plasma mirror reflectivity and focal spot quality for tens of picosecond laser pulses

    Science.gov (United States)

    Forestier-Colleoni, Pierre; Williams, Jackson; Scott, Graeme; Mariscal, Dereck. A.; McGuffey, Christopher; Beg, Farhat N.; Chen, Hui; Neely, David; Ma, Tammy

    2017-10-01

    The Advanced Radiographic Capability (ARC) laser at the NIF (LLNL) is high-energy ( 4 kJ) with a pulse length of 30ps, and is capable of focusing to an intensity of 1018W/cm2 with a 100 μm focal spot. The ARC laser is at an intensity which can be used to produce proton beams. However, for applications such as radiography and warm dense matter creation, a higher laser intensity may be desired to generate more energetic proton beams. One possibility to increase the intensity is to decrease the focused spot size by employing a smaller f-number optic. But it is difficult to implement such an optic or to bring the final focusing parabola closer to the target within the complicated NIF chamber geometry. A proposal is to use ellipsoidal plasma mirrors (PM) for fast focusing of the ARC laser light, thereby increasing the peak intensity. There is uncertainty, however, in the survivability and reflectivity of PM at such long pulse durations. Here, we show experimental results from the Titan laser to study the reflectivity of flat PM as a function of laser pulse length. A calorimeter was used to measure the PM reflectivity. We also observed degradation of the far and near field energy distribution of the laser after the reflection by the PM for pulse-lengths beyond 10ps. Contract DE-AC52-07NA27344. Funded by the LLNL LDRD program: tracking code 17-ERD-039.

  2. Surface emitting ring quantum cascade lasers for chemical sensing

    Science.gov (United States)

    Szedlak, Rolf; Hayden, Jakob; Martín-Mateos, Pedro; Holzbauer, Martin; Harrer, Andreas; Schwarz, Benedikt; Hinkov, Borislav; MacFarland, Donald; Zederbauer, Tobias; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Acedo, Pablo; Lendl, Bernhard; Strasser, Gottfried

    2018-01-01

    We review recent advances in chemical sensing applications based on surface emitting ring quantum cascade lasers (QCLs). Such lasers can be implemented in monolithically integrated on-chip laser/detector devices forming compact gas sensors, which are based on direct absorption spectroscopy according to the Beer-Lambert law. Furthermore, we present experimental results on radio frequency modulation up to 150 MHz of surface emitting ring QCLs. This technique provides detailed insight into the modulation characteristics of such lasers. The gained knowledge facilitates the utilization of ring QCLs in combination with spectroscopic techniques, such as heterodyne phase-sensitive dispersion spectroscopy for gas detection and analysis.

  3. Characterization of a Laser Surface-Treated Martensitic Stainless Steel

    OpenAIRE

    S.R. Al-Sayed; A.A. Hussein; A.A. Nofal; S.I. Hassab Elnaby; H. Elgazzar

    2017-01-01

    Laser surface treatment was carried out on AISI 416 machinable martensitic stainless steel containing 0.225 wt.% sulfur. Nd:YAG laser with a 2.2-KW continuous wave was used. The aim was to compare the physical and chemical properties achieved by this type of selective surface treatment with those achieved by the conventional treatment. Laser power of different values (700 and 1000 W) with four corresponding different laser scanning speeds (0.5, 1, 2, and 3 m?min?1) was adopted to reach the op...

  4. SURFACE CAST IRON STRENGTHENING USING COMBINED LASER AND ULTRASONIC PROCESSING

    Directory of Open Access Journals (Sweden)

    O. G. Devojno

    2013-01-01

    Full Text Available The paper provides an analysis of ultrasonic surface plastic deformation and subsequent laser thermal strengthening of gray cast iron parts in the regime of hardening from a solid state with the purpose to obtain strengthened surface layers of bigger depth and less roughness of the processed surface. Program complex ANSYS 11.0 has been used for calculation of temperature fields induced by laser exposure.  The appropriate regime of laser processing without surface fusion has been selected on the basis of the applied complex. The possibility of displacement in the bottom boundary of α–γ-transformation temperature  for СЧ20 with 900 °С up to 800 °С is confirmed due to preliminary ultrasonic surface plastic deformation of the surface that allows to expand technological opportunities of laser quenching  of gray  cast iron from a solid state. 

  5. Power Spectral Density Evaluation of Laser Milled Surfaces

    Directory of Open Access Journals (Sweden)

    Raoul-Amadeus Lorbeer

    2017-12-01

    Full Text Available Ablating surfaces with a pulsed laser system in milling processes often leads to surface changes depending on the milling depth. Especially if a constant surface roughness and evenness is essential to the process, structural degradation may advance until the process fails. The process investigated is the generation of precise thrust by laser ablation. Here, it is essential to predict or rather control the evolution of the surfaces roughness. Laser ablative milling with a short pulse laser system in vacuum (≈1 Pa were performed over depths of several 10 µm documenting the evolution of surface roughness and unevenness with a white light interference microscope. Power spectral density analysis of the generated surface data reveals a strong influence of the crystalline structure of the solid. Furthermore, it was possible to demonstrate that this effect could be suppressed for gold.

  6. Research progress on laser surface modification of titanium alloys

    International Nuclear Information System (INIS)

    Tian, Y.S.; Chen, C.Z.; Li, S.T.; Huo, Q.H.

    2005-01-01

    Recent developments on laser surface modification of titanium and its alloys are reviewed. Due to the intrinsic properties of high coherence and directionality, laser beam can be focus onto metallic surface to perform a broad range of treatments such as remelting, alloying and cladding, which are used to improve the wear and corrosion resistance of titanium alloys. In addition, the fabrication of bioactive films on the surface of titanium alloys to improve their biocompatibility can be performed by the method of laser ablation deposition. The effect of some laser processing parameters on the resulting surface properties of titanium alloys is discussed. The problems to be solved and the prospects in the field of laser modification of titanium and its alloys are elucidated

  7. Heat Flow In Cylindrical Bodies During Laser Surface Transformation Hardening

    Science.gov (United States)

    Sandven, Ole A.

    1980-01-01

    A mathematical model for the transient heat flow in cylindrical specimens is presented. The model predicts the temperature distribution in the vicinity of a moving ring-shaped laser spot around the periphery of the outer surface of a cylinder, or the inner surface of a hollow cylinder. It can be used to predict the depth of case in laser surface transformation hardening. The validity of the model is tested against experimental results obtained on SAE 4140 steel.

  8. Using a terrestrial laser scanner to measure spatiotemporal surface moisture dynamics

    Science.gov (United States)

    Smit, Y.; Donker, J.; Ruessink, G.

    2017-12-01

    A terrestrial laser scanner (TLS) is an active remote sensing technique that utilizes the round trip time of an emitted laser beam to provide the range between the laser scanner and the backscattering object. It is routinely used for topographic mapping, forest measurements or 3D city models since it derives useful object representations by means of a dense three-dimensional (3D) point cloud. Here, we present a novel application using the returned intensity of the emitted beam to detect surface moisture with the RIEGL VZ-400. Because this TLS operates at a wavelength near a water absorption band (1550 nm), reflectance is an accurate parameter to measure surface moisture over its full range. Five days of intensive laser scanning were performed on a Dutch beach to illustrate the applicability of the TLS. Concurrent gravimetric surface moisture samples were collected to calibrate the relation between reflectance and surface moisture. Results reveal the reflectance output is a robust parameter to measure surface moisture from the thin upper layer over its full range from 0% to 25%. The obtained calibration curve of the presented TLS, describing the relationship between reflectance and surface moisture, has a root-mean-square error of 2.7% and a correlation coefficient squared of 0.85. This relation holds to about 60 m from the TLS. Within this distance the TLS typically produces O(10^6-10^7) data points, which we averaged into surface moisture maps with a 1 x 1 m resolution. This grid size largely removes small moisture disturbances induced by, for example, footprints or tire tracks, while retaining larger scale trends. Concluding, TLS (RIEGL-VZ 400) is a highly suited technique to accurately and robustly measure spatiotemporal surface moisture variations on a coastal beach with high spatial ( 1 x 1 m) and temporal ( 15-30min.) resolution.

  9. Mars analog minerals' spectral reflectance characteristics under Martian surface conditions

    Science.gov (United States)

    Poitras, J. T.; Cloutis, E. A.; Salvatore, M. R.; Mertzman, S. A.; Applin, D. M.; Mann, P.

    2018-05-01

    We investigated the spectral reflectance properties of minerals under a simulated Martian environment. Twenty-eight different hydrated or hydroxylated phases of carbonates, sulfates, and silica minerals were selected based on past detection on Mars through spectral remote sensing data. Samples were ground and dry sieved to <45 μm grain size and characterized by XRD before and after 133 days inside a simulated Martian surface environment (pressure 5 Torr and CO2 fed). Reflectance spectra from 0.35 to 4 μm were taken periodically through a sapphire (0.35-2.5 μm) and zinc selenide (2.5-4 μm) window over a 133-day period. Mineral stability on the Martian surface was assessed through changes in spectral characteristics. Results indicate that the hydrated carbonates studied would be stable on the surface of Mars, only losing adsorbed H2O while maintaining their diagnostic spectral features. Sulfates were less stable, often with shifts in the band position of the SO, Fe, and OH absorption features. Silicas displayed spectral shifts related to SiOH and hydration state of the mineral surface, while diagnostic bands for quartz were stable. Previous detection of carbonate minerals based on 2.3-2.5 μm and 3.4-3.9 μm features appears to be consistent with our results. Sulfate mineral detection is more questionable since there can be shifts in band position related to SO4. The loss of the 0.43 μm Fe3+ band in many of the sulfates indicate that there are fewer potential candidates for Fe3+ sulfates to permanently exist on the Martian surface based on this band. The gypsum sample changed phase to basanite during desiccation as demonstrated by both reflectance and XRD. Silica on Mars has been detected using band depth ratio at 1.91 and 1.96 μm and band minimum position of the 1.4 μm feature, and the properties are also used to determine their age. This technique continues to be useful for positive silica identifications, however, silica age appears to be less consistent

  10. Degradation of Silicon Carbide Reflective Surfaces in the LEO Environment

    Science.gov (United States)

    Mileti, Sandro; Coluzzi, Plinio; Marchetti, Mario

    2009-01-01

    Space mirrors in Low Earth Orbit (LEO) encounter a degradation problem caused by the impact of atomic oxygen (ATOX) in the space environment. This paper presents an experiment of the atomic oxygen impact degradation and UV synergic effects on ground simulation. The experiment was carried out in a dedicated ATOX simulation vacuum chamber. As target materials, a polished CVD Beta-silicon carbide (SiC) coating was investigated. The selection of silicon carbide is due to its high potential candidate as a mirror layer substrate material for its good reflectance at UV wavelengths and excellent thermal diffusivity. It has highly desirable mechanical and thermal properties and can achieve an excellent surface finish. The deposition of the coatings were on carbon-based material substrate; i.e., silicon impregnated carbon fiber composite (C/SiC). Mechanical and thermal properties of the coatings such as hardness and Coefficient of Thermal Expansion (CTE) were achieved. Several atomic oxygen impact angles were studied tilting the target samples respect to the flux direction. The various impact angles permitted to analyze the different erosion rates and typologies which the mirrors would encounter in LEO environment. The degradation was analyzed in various aspects. Macroscopic mass loss per unit area, surface roughness and morphology change were basically analyzed. The exposed surfaces of the materials were observed through a Scanning Electron Microscope (SEM). Secondly, optical diagnostic of the surfaces were performed in order to investigate their variation in optical properties as the evaluation of reflectance degradation. The presence of micro-cracks caused by shrinkage, grinding, polishing or thermal cycling and the porosity in the coatings, could have led to the undercutting phenomenon. Observation of uprising of undercutting was also conducted. Remarks are given regarding capabilities in short-term mission exposures to the LEO environment of this coating.

  11. Laser reflection method for determination of shear stress in low density transitional flows

    Science.gov (United States)

    Sathian, Sarith P.; Kurian, Job

    2006-03-01

    The details of laser reflection method (LRM) for the determination of shear stress in low density transitional flows are presented. The method is employed to determine the shear stress due to impingement of a low density supersonic free jet issuing out from a convergent divergent nozzle on a flat plate. The plate is smeared with a thin oil film and kept parallel to the nozzle axis. For a thin oil film moving under the action of aerodynamic boundary layer, the shear stress at the air-oil interface is equal to the shear stress between the surface and air. A direct and dynamic measurement of the oil film slope generated by the shear force is done using a position sensing detector (PSD). The thinning rate of the oil film is directly measured which is the major advantage of the LRM. From the oil film slope history, calculation of the shear stress is done using a three-point formula. The range of Knudsen numbers investigated is from 0.028 to 0.516. Pressure ratio across the nozzle varied from 3,500 to 8,500 giving highly under expanded free jets. The measured values of shear, in the overlapping region of experimental parameters, show fair agreement with those obtained by force balance method and laser interferometric method.

  12. Laser-Based Surface Modification of Microstructure for Carbon Fiber-Reinforced Plastics

    Science.gov (United States)

    Yang, Wenfeng; Sun, Ting; Cao, Yu; Li, Shaolong; Liu, Chang; Tang, Qingru

    2018-05-01

    Bonding repair is a powerful feature of carbon fiber-reinforced plastics (CFRP). Based on the theory of interface bonding, the interface adhesion strength and reliability of the CFRP structure will be directly affected by the microscopic features of the CFRP surface, including the microstructure, physical, and chemical characteristics. In this paper, laser-based surface modification was compared to Peel-ply, grinding, and polishing to comparatively evaluate the surface microstructure of CFRP. The surface microstructure, morphology, fiber damage, height and space parameters were investigated by scanning electron microscopy (SEM) and laser confocal microscopy (LCM). Relative to the conventional grinding process, laser modification of the CFRP surface can result in more uniform resin removal and better processing control and repeatability. This decreases the adverse impact of surface fiber fractures and secondary damage. The surface properties were significantly optimized, which has been reflected such things as the obvious improvement of surface roughness, microstructure uniformity, and actual area. The improved surface microstructure based on laser modification is more conducive to interface bonding of CFRP structure repair. This can enhance the interfacial adhesion strength and reliability of repair.

  13. Inexpensive laser-induced surface modification in bismuth thin films

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, A. Reyes [Facultad de Ciencias, Universidad Autónoma del Estado de México, Carretera Toluca, Ixtlahuaca Kilómetro 15.5, C.P. 50200 Edo. de México (Mexico); Hautefeuille, M., E-mail: mathieu_h@ciencias.unam.mx [Facultad de Ciencias, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Circuito Exterior S/N, Coyoacán, Ciudad Universitaria, C.P. 04510 D.F. Mexico (Mexico); García, A. Esparza [Fotofísica y Películas Delgadas, Departamento de Tecnociencias, CCADET-UNAM, Circuito exterior s/n C.P. 04510 Cd. Universitaria, D.F. Mexico (Mexico); Mejia, O. Olea [Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, Km 14.5, Unidad El Rosedal, 50200 San Cayetano, Estado de México (Mexico); López, M.A. Camacho [Facultad de Química, Universidad Autónoma del Estado de México, Tollocan s/n, esq. Paseo Colón, Toluca, Estado de México 50110 (Mexico)

    2015-05-01

    Highlights: • Laser-induced microbumps were formed on bismuth films using a simple, low-cost, laser setup. • The patterns, similar to those typically obtained with high-power lasers, were characterized. • Control of laser ablation conditions is critical in the fabrication of surface microbumps. - Abstract: In this work, we present results on texturing a 500 nm thick bismuth film, deposited by sputtering onto a glass slide using a low-cost homemade, near-infrared pulsed laser platform. A 785 nm laser diode of a CD–DVD pickup head was precisely focused on the sample mounted on a motorized two-axis translation stage to generate localized surface microbumps on the bismuth films. This simple method successfully transferred desired micropatterns on the films in a computer-numerical control fashion. Irradiated zones were characterized by atomic force microscopy and scanning electron microscopy. It was observed that final results are strongly dependent on irradiation parameters.

  14. Reflection properties of road surfaces. Contribution to OECD Scientific Expert Group AC4 on Road Surface Characteristics.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1983-01-01

    Photometric characteristics of road surfaces are dealt with. Representation of reflection properties in public lighting; quality criteria of road lighting installations; classification of road surfaces; the relation between reflection characteristics and other properties of road pavements in public

  15. Impact toughness of laser surface alloyed Aluminium

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2012-03-01

    Full Text Available with intermetallic phases and metal matrix composites were achieved during laser alloying. Brittle fracture of the SiC particles and transgranular cracking of the intermetallic phases was observed for the laser alloyed samples, while ductile fracture was observed...

  16. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Mthunzi, P. [National Laser Centre, Council for Scientific and Industrial Research, 0001 Pretoria (South Africa); Muller, T.F.G. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Julies, B. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Ramponi, R. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa)

    2014-12-01

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr{sub 2}O{sub 3} layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr{sub 2}O{sub 3} layer. The α-Cr{sub 2}O{sub 3} layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%.

  17. Biocompatibility of Er:YSGG laser radiated root surfaces

    Science.gov (United States)

    Benthin, Hartmut; Ertl, Thomas P.; Schmidt, Dirk; Purucker, Peter; Bernimoulin, J.-P.; Mueller, Gerhard J.

    1996-01-01

    Pulsed Er:YAG and Er:YSGG lasers are well known to be effective instruments for the ablation of dental hard tissues. Developments in the last years made it possible to transmit the laser radiation at these wavelengths with flexible fibers. Therefore the application in the periodontal pocket may be possible. The aim of this study was to evaluate the in-vitro conditions to generate a bioacceptable root surface. Twenty extracted human teeth, stored in an antibiotic solution, were conventionally scaled, root planed and axially separated into two halves. Two main groups were determined. With the first group laser radiation was carried out without and in the second group with spray cooling. The laser beam was scanned about root surface areas. Laser parameters were varied in a selected range. The biocompatibility was measured with the attachment of human gingival fibroblasts and directly compared to conventionally treated areas of the root surfaces. The fibroblasts were qualified and counted in SEM investigations. On conventionally treated areas gingival fibroblasts show the typical uniform cover. In dependance on the root roughness after laser treatment the fibroblasts loose the typical parallel alignment to the root surface. With spray cooling a better in-vitro attachment could be obtained. Without spray cooling the higher increase in temperature conducted to less bioacceptance by the human gingival fibroblasts to the root surface. These results show the possibility of producing bioacceptable root surfaces with pulsed laser radiation in the range of very high water absorption near 3 micrometer.

  18. Airborne laser: a tool to study landscape surface features

    International Nuclear Information System (INIS)

    Ritchie, J.C.; Jackson, T.J.; Everitt, J.H.; Escobar, D.E.; Murphey, J.B.; Grissinger, E.H.

    1992-01-01

    Landscape surface features related to erosion and hydrology were measured using an airborne laser profiler. The airborne laser profiler made 4,000 measurements per second with a recording accuracy of 5 cm (1.9 inches) on a single measurement. Digital data from the laser are recorded and analyzed with a personal computer. These airborne laser profiles provide information on surface landscape features. Topography and canopy heights, cover, and distribution of natural vegetation were determined in studies in South Texas. Laser measurements of shrub cover along flightlines were highly correlated (R 2 = 0.98) with ground measurements made with line-intercept methods. Stream channel cross sections on Goodwin Creek in Mississippi were measured quickly and accurately with airborne laser data. Airborne laser profile data were used to measure small gullies in a level fallow field and in field with mature soybeans. While conventional ground-based techniques can be used to make these measurements, airborne laser profiler techniques allow data to be collected quickly, at a high density, and in areas that are essentially inaccessible for ground surveys. Airborne laser profiler data can quantify landscape features related to erosion and runoff, and the laser proler has the potential to be a useful tool for providing other data for studying and managing natural resources

  19. Laser surface modification of polyethersulfone films: effect of laser wavelength on biocompatibility

    International Nuclear Information System (INIS)

    Pazokian, H; Jelvani, S; Mollabashi, M; Barzin, J

    2013-01-01

    In this paper laser ablation of polyethersulfone (PES) films regarding to the change in biocompatibility of the surface is investigated at 3 different wavelengths of 193nm (ArF), 248 nm (KrF) and 308 nm (XeCl). The optimum laser fluence and number of pulses for the improvement of the surface biocompatibility is found by examination of the surface behavior in contact with platelets and fibroblasts cells at 3 wavelengths. These biological modifications are explained by alteration of the surface morphology and chemistry following irradiation. The results show that the KrF laser is the best choice for treatment of PES in biological applications.

  20. Barium fluoride surface preparation, analysis and UV reflective coatings at Lawrence Livermore National Laboratory

    International Nuclear Information System (INIS)

    Wuest, C.R.

    1992-01-01

    Lawrence Livermore National Laboratory (LLNL) has begun a program of study on barium fluoride scintillating crystals for the Barium Fluoride Electromagnetic Calorimeter Collaboration. This program has resulted in a number of significant improvements in the mechanical processing, polishing and coating of barium fluoride crystals. Techniques have been developed using diamond-loaded pitch lapping that can produce 15 angstrom RMS surface finishes over large areas. These lapped surfaces have been shown to be crystalline using Rutherford Back-scattering (RBS). Also, special polishing fixtures have been designed based on mounting technology developed for the 1.1 m diameter optics used in LLNL's Nova Laser. These fixtures allow as many as five 25--50 cm long barium fluoride crystals to be polished and lapped at a time with the necessary tolerances for the 16,000 crystal Barium Fluoride Calorimeter. In addition, results will be presented on coating barium fluoride with UV reflective layers of magnesium fluoride and aluminum

  1. Surface plasmon-enhanced two-photon excited whispering-gallery modes ultraviolet laser from Zno microwire

    Directory of Open Access Journals (Sweden)

    Yunpeng Wang

    2017-11-01

    Full Text Available The two-photon excited UV laser with narrow line width and high Q value was obtained. The total internal reflection from the four side surfaces of the quadrilateral-ZnO microwire offered the whispering gallery mode (WGM resonant cavity. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail for this special type of micro-cavity. In addition, in order to enhance the power of the two-photon excited UV laser, the surface plasmon enhancement by the Au nanoparticles was also performed and explained well by the theory of the localized surface plasmon.

  2. Laser shock wave assisted patterning on NiTi shape memory alloy surfaces

    Science.gov (United States)

    Seyitliyev, Dovletgeldi; Li, Peizhen; Kholikov, Khomidkhodza; Grant, Byron; Karaca, Haluk E.; Er, Ali O.

    2017-02-01

    An advanced direct imprinting method with low cost, quick, and less environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni50Ti50 shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generates pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface. Scanning electron microscope (SEM) and optical microscope images of square pattern with different sizes were studied. One dimensional profile analysis shows that the depth of the patterned sample initially increase linearly with the laser energy until 125 mJ/pulse where the plasma further absorbs and reflects the laser beam. In addition, light the microscope image show that the surface of NiTi alloy was damaged due to the high power laser energy which removes the graphite layer.

  3. Towards friction control using laser-induced periodic surface structures

    NARCIS (Netherlands)

    Eichstädt, J.; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert; Schmidt, M.; Zaeh, M.

    2011-01-01

    This paper aims at contributing to the study of laser-induced periodic surface structures (LIPSS) and the description of their tribological properties in order to facilitate the knowledge for contact mechanical applications. To obtain laser parameters for LIPSS formation, we propose to execute two

  4. Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

    International Nuclear Information System (INIS)

    Zhang, Haisu; Tzortzakis, Stelios

    2016-01-01

    We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

  5. Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haisu [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Heraklion 71110 (Greece); Tzortzakis, Stelios, E-mail: stzortz@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Heraklion 71110 (Greece); Materials Science and Technology Department, University of Crete, 71003 Heraklion (Greece); Science Program, Texas A& M University at Qatar, P.O. Box 23874, Doha (Qatar)

    2016-05-23

    We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

  6. Direct modification of silicon surface by nanosecond laser interference lithography

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dapeng [JR3CN and CNM (Changchun University of Science and Technology), Changchun 130022 (China); JR3CN and IRAC (University of Bedfordshire), Luton LU1 3JU (United Kingdom); Wang, Zuobin, E-mail: wangz@cust.edu.cn [JR3CN and CNM (Changchun University of Science and Technology), Changchun 130022 (China); JR3CN and IRAC (University of Bedfordshire), Luton LU1 3JU (United Kingdom); Zhang, Ziang [JR3CN and CNM (Changchun University of Science and Technology), Changchun 130022 (China); Yue, Yong [JR3CN and CNM (Changchun University of Science and Technology), Changchun 130022 (China); JR3CN and IRAC (University of Bedfordshire), Luton LU1 3JU (United Kingdom); Li, Dayou [JR3CN and IRAC (University of Bedfordshire), Luton LU1 3JU (United Kingdom); Maple, Carsten [JR3CN and CNM (Changchun University of Science and Technology), Changchun 130022 (China); JR3CN and IRAC (University of Bedfordshire), Luton LU1 3JU (United Kingdom)

    2013-10-01

    Periodic and quasi-periodic structures on silicon surface have numerous significant applications in photoelectronics and surface engineering. A number of technologies have been developed to fabricate the structures in various research fields. In this work, we take the strategy of direct nanosecond laser interference lithography technology, and focus on the silicon material to create different well-defined surface structures based on theoretical analysis of the formation of laser interference patterns. Two, three and four-beam laser interference systems were set up to fabricate the grating, regular triangle and square structures on silicon surfaces, respectively. From the AFM micrographs, the critical features of structures have a dependence on laser fluences. For a relative low laser fluence, grating and dot structures formed with bumps due to the Marangoni Effect. With the increase of laser fluences, melt and evaporation behaviors can be responsible for the laser modification. By properly selecting the process parameters, well-defined grating and dot structures can been achieved. It can be demonstrated that direct laser interference lithography is a facile and efficient technology with the advantage of a single process procedure over macroscale areas for the fabrication of micro and nano structures.

  7. Portable laser-induced breakdown spectroscopy/diffuse reflectance hybrid spectrometer for analysis of inorganic pigments

    Science.gov (United States)

    Siozos, Panagiotis; Philippidis, Aggelos; Anglos, Demetrios

    2017-11-01

    A novel, portable spectrometer, combining two analytical techniques, laser-induced breakdown spectroscopy (LIBS) and diffuse reflectance spectroscopy, was developed with the aim to provide an enhanced instrumental and methodological approach with regard to the analysis of pigments in objects of cultural heritage. Technical details about the hybrid spectrometer and its operation are presented and examples are given relevant to the analysis of paint materials. Both LIBS and diffuse reflectance spectra in the visible and part of the near infrared, corresponding to several neat mineral pigment samples, were recorded and the complementary information was used to effectively distinguish different types of pigments even if they had similar colour or elemental composition. The spectrometer was also employed in the analysis of different paints on the surface of an ancient pottery sherd demonstrating the capabilities of the proposed hybrid diagnostic approach. Despite its instrumental simplicity and compact size, the spectrometer is capable of supporting analytical campaigns relevant to archaeological, historical or art historical investigations, particularly when quick data acquisition is required in the context of surveys of large numbers of objects and samples.

  8. Multiple reflections and Fresnel absorption in an actual 3D keyhole during deep penetration laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Jin Xiangzhong [Laser Institute of Hunan University, Changsha, Hunan, 410082 (China); Berger, Peter [Institut fuer Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany); Graf, Thomas [Institut fuer Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany)

    2006-11-07

    In laser welding experiments of glass, keyhole shapes are observed by two high-speed cameras from two perpendicular directions. From the obtained keyhole pictures, it can be seen that in medium- and low-speed laser penetration welding, the main distortion of the keyhole is not the section metamorphosis from rotational symmetry, but the bending of its centre line. Based on such a keyhole photograph, the keyhole profiles and its centre line are determined by the method of polynomial fitting. Then, under the assumption of a circular cross section at each depth of the keyhole, the behaviour of the laser beam in the keyhole is analysed by tracing a ray of light using geometrical optics theory; the Fresnel absorption and multiple reflections in the keyhole are systematically studied, and the laser intensities absorbed on the keyhole walls are calculated. The absorbed laser intensity is not distributed uniformly on the keyhole wall. The keyhole wall absorbs laser intensity mainly on the half-part of the keyhole wall near the front wall. Because of the high absorptivity of the glass, Fresnel absorption from the first incidence of a laser beam plays a dominant role in the final laser intensity distribution on the keyhole wall, multiple reflections have some minor effects on the intensity distribution on the bottom part of the keyhole.

  9. Near-Infrared Confocal Laser Reflectance Cytoarchitectural Imaging of the Substantia Nigra and Cerebellum in the Fresh Human Cadaver.

    Science.gov (United States)

    Cheyuo, Cletus; Grand, Walter; Balos, Lucia L

    2017-01-01

    Cytoarchitectural neuroimaging remains critical for diagnosis of many brain diseases. Fluorescent dye-enhanced, near-infrared confocal in situ cellular imaging of the brain has been reported. However, impermeability of the blood-brain barrier to most fluorescent dyes limits clinical utility of this modality. The differential degree of reflectance from brain tissue with unenhanced near-infrared imaging may represent an alternative technique for in situ cytoarchitectural neuroimaging. We assessed the utility of unenhanced near-infrared confocal laser reflectance imaging of the cytoarchitecture of the cerebellum and substantia nigra in 2 fresh human cadaver brains using a confocal near-infrared laser probe. Cellular images based on near-infrared differential reflectance were captured at depths of 20-180 μm from the brain surface. Parts of the cerebellum and substantia nigra imaged using the probe were subsequently excised and stained with hematoxylin and eosin for histologic correlation. Near-infrared reflectance imaging revealed the 3-layered cytoarchitecture of the cerebellum, with Purkinje cells appearing hyperreflectant. In the substantia nigra, neurons appeared hyporeflectant with hyperreflectant neuromelanin cytoplasmic inclusions. Cytoarchitecture of the cerebellum and substantia nigra revealed on near-infrared imaging closely correlated with the histology on hematoxylin-eosin staining. We showed that unenhanced near-infrared reflectance imaging of fresh human cadaver brain can reliably identify and distinguish neurons and detailed cytoarchitecture of the cerebellum and substantia nigra. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Atomic diffusion in laser surface modified AISI H13 steel

    Science.gov (United States)

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2013-07-01

    This paper presents a laser surface modification process of AISI H13 steel using 0.09 and 0.4 mm of laser spot sizes with an aim to increase surface hardness and investigate elements diffusion in laser modified surface. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, pulse repetition frequency (PRF), and overlap percentage. The hardness properties were tested at 981 mN force. Metallographic study and energy dispersive X-ray spectroscopy (EDXS) were performed to observe presence of elements and their distribution in the sample surface. Maximum hardness achieved in the modified surface was 1017 HV0.1. Change of elements composition in the modified layer region was detected in the laser modified samples. Diffusion possibly occurred for C, Cr, Cu, Ni, and S elements. The potential found for increase in surface hardness represents an important method to sustain tooling life. The EDXS findings signify understanding of processing parameters effect on the modified surface composition.

  11. Dependence of laser assisted cleaning of clad surfaces on the laser fluence

    International Nuclear Information System (INIS)

    Nilaya, J.P.; Raote, P.; Sai Prasad, M.B.; Biswas, D.J.; Aniruddha Kumar

    2005-01-01

    The decontamination factor is studied as a function of laser fluence for three kinds of clad surfaces viz., plain zircaloy, autoclaved zircaloy and SS with cesium as the test contamination. It has been found that the decontamination factor exhibits a maximal behaviour with the laser fluence and its maximum value occurs at different laser fluences in the three cases. The maximal behaviour is attributed to reduced coupling of energy from the laser beam to the substrate due to the initiation of surface-assisted optical breakdown. The results obtained in the experiment carried out in helium environment qualitatively support this explanation (author)

  12. Diffuse Reflectance Spectroscopy for Surface Measurement of Liver Pathology.

    Science.gov (United States)

    Nilsson, Jan H; Reistad, Nina; Brange, Hannes; Öberg, Carl-Fredrik; Sturesson, Christian

    2017-01-01

    Liver parenchymal injuries such as steatosis, steatohepatitis, fibrosis, and sinusoidal obstruction syndrome can lead to increased morbidity and liver failure after liver resection. Diffuse reflectance spectroscopy (DRS) is an optical measuring method that is fast, convenient, and established. DRS has previously been used on the liver with an invasive technique consisting of a needle that is inserted into the parenchyma. We developed a DRS system with a hand-held probe that is applied to the liver surface. In this study, we investigated the impact of the liver capsule on DRS measurements and whether liver surface measurements are representative of the whole liver. We also wanted to confirm that we could discriminate between tumor and liver parenchyma by DRS. The instrumentation setup consisted of a light source, a fiber-optic contact probe, and two spectrometers connected to a computer. Patients scheduled for liver resection due to hepatic malignancy were included, and DRS measurements were performed on the excised liver part with and without the liver capsule and alongside a newly cut surface. To estimate the scattering parameters and tissue chromophore volume fractions, including blood, bile, and fat, the measured diffuse reflectance spectra were applied to an analytical model. In total, 960 DRS spectra from the excised liver tissue of 18 patients were analyzed. All factors analyzed regarding tumor versus liver tissue were significantly different. When measuring through the capsule, the blood volume fraction was found to be 8.4 ± 3.5%, the lipid volume fraction was 9.9 ± 4.7%, and the bile volume fraction was 8.2 ± 4.6%. No differences could be found between surface measurements and cross-sectional measurements. In measurements with/without the liver capsule, the differences in volume fraction were 1.63% (0.75-2.77), -0.54% (-2.97 to 0.32), and -0.15% (-1.06 to 1.24) for blood, lipid, and bile, respectively. This study shows that it is possible to manage DRS

  13. Application of Faraday rotator to suppression of target-reflected radiation in the optical path of a laser installation

    International Nuclear Information System (INIS)

    Bykovskiy, N.E.; Denus, S.; Dubik, A.; Ovsik, Y.; Lisunov, V.V.; Senatskiy, Y.V.; Fedotov, S.I.

    1988-01-01

    The interaction conditions between powerful laser radiation and a target are examined together with the Faraday rotators designed for suppressing target-reflected backward radiation in the neodymium glass laser optical path

  14. A simulation of laser energy absorption by nanowired surface

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, Miguel F.S.; Ramos, Alexandre F., E-mail: miguel.vasconcelos@usp.br, E-mail: alex.ramos@usp.br [Universidade de São Paulo (USP), SP (Brazil). Escola de Artes, Ciências e Humanidades

    2017-07-01

    Despite recent advances on research about laser inertial fusion energy, to increase the portion of energy absorbed by the target's surface from lasers remains as an important challenge. The plasma formed during the initial instants of laser arrival shields the target and prevents the absorption of laser energy by the deeper layers of the material. One strategy to circumvent that effect is the construction of targets whose surfaces are populated with nanowires. The nanowired surfaces have increased absorption of laser energy and constitutes a promising pathway for enhancing laser-matter coupling. In our work we present the results of simulations aiming to investigate how target's geometrical properties might contribute for maximizing laser energy absorption by material. Simulations have been carried out using the software FLASH, a multi-physics platform developed by researchers from the University of Chicago, written in FORTRAN 90 and Python. Different tools for generating target's geometry and analysis of results were developed using Python. Our results show that a nanowired surfaces has an increased energy absorption when compared with non wired surface. The software for visualization developed in this work also allowed an analysis of the spatial dynamics of the target's temperature, electron density, ionization levels and temperature of the radiation emitted by it. (author)

  15. A simulation of laser energy absorption by nanowired surface

    International Nuclear Information System (INIS)

    Vasconcelos, Miguel F.S.; Ramos, Alexandre F.

    2017-01-01

    Despite recent advances on research about laser inertial fusion energy, to increase the portion of energy absorbed by the target's surface from lasers remains as an important challenge. The plasma formed during the initial instants of laser arrival shields the target and prevents the absorption of laser energy by the deeper layers of the material. One strategy to circumvent that effect is the construction of targets whose surfaces are populated with nanowires. The nanowired surfaces have increased absorption of laser energy and constitutes a promising pathway for enhancing laser-matter coupling. In our work we present the results of simulations aiming to investigate how target's geometrical properties might contribute for maximizing laser energy absorption by material. Simulations have been carried out using the software FLASH, a multi-physics platform developed by researchers from the University of Chicago, written in FORTRAN 90 and Python. Different tools for generating target's geometry and analysis of results were developed using Python. Our results show that a nanowired surfaces has an increased energy absorption when compared with non wired surface. The software for visualization developed in this work also allowed an analysis of the spatial dynamics of the target's temperature, electron density, ionization levels and temperature of the radiation emitted by it. (author)

  16. Pulsed laser stereophotography of plasmas and dynamically moving surfaces

    International Nuclear Information System (INIS)

    Paisley, D.L.

    1987-01-01

    A pulsed laser is used as a light source for illuminating the surface of a dynamic event of 3 mm//μs. At a predetermined time during the dynamic action, a stereo camera is used to record a pair of images of the dynamically moving surface. The stereoimage pair can be quantified for surface contour

  17. Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 μm on surface morphology, permeability, and acid resistance.

    Science.gov (United States)

    Chang, Nai-Yuan N; Jew, Jamison M; Simon, Jacob C; Chen, Kenneth H; Lee, Robert C; Fried, William A; Cho, Jinny; Darling, Cynthia L; Fried, Daniel

    2017-12-01

    Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO 2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO 2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO 2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  18. WATER SURFACE RECONSTRUCTION IN AIRBORNE LASER BATHYMETRY FROM REDUNDANT BED OBSERVATIONS

    Directory of Open Access Journals (Sweden)

    G. Mandlburger

    2017-09-01

    Full Text Available In airborne laser bathymetry knowledge of exact water level heights is a precondition for applying run-time and refraction correction of the raw laser beam travel path in the medium water. However, due to specular reflection especially at very smooth water surfaces often no echoes from the water surface itself are recorded (drop outs. In this paper, we first discuss the feasibility of reconstructing the water surface from redundant observations of the water bottom in theory. Furthermore, we provide a first practical approach for solving this problem, suitable for static and locally planar water surfaces. It minimizes the bottom surface deviations of point clouds from individual flight strips after refraction correction. Both theoretical estimations and practical results confirm the potential of the presented method to reconstruct water level heights in dm precision. Achieving good results requires enough morphological details in the scene and that the water bottom topography is captured from different directions.

  19. Viscoelasticity evaluation of rubber by surface reflection of supersonic wave.

    Science.gov (United States)

    Omata, Nobuaki; Suga, Takahiro; Furusawa, Hirokazu; Urabe, Shinichi; Kondo, Takeru; Ni, Qing-Qing

    2006-12-22

    The main characteristic of rubber is a viscoelasticity. So it is important to research the characteristic of the viscoelasticity of the high frequency band for the friction between a rubber material and the hard one with roughness, for instance, the tire and the road. As for the measurement of the viscoelasticity of rubber, DMA (dynamic mechanical analysis) is general. However, some problems are pointed out to the measurement of the high frequency band by DMA. Then, we evaluated the viscoelasticity characteristic by the supersonic wave measurement. However, attenuation of rubber is large, and when the viscoelasticity is measured by the supersonic wave therefore, it is inconvenient and limited in a past method by means of bottom reflection. In this report, we tried the viscoelasticity evaluation by the method of using complex surface reflection coefficient and we compared with the friction coefficient under wide-range friction velocity. As a result, some relationships had been found for two properties. We report the result that character of viscoelasticity of rubber was comparable to friction coefficient.

  20. IRAS surface brightness maps of reflection nebulae in the Pleiades

    Science.gov (United States)

    Castelaz, Michael W.; Werner, M. W.; Sellgren, K.

    1987-01-01

    Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.

  1. Robust Non-Wetting PTFE Surfaces by Femtosecond Laser Machining

    Directory of Open Access Journals (Sweden)

    Fang Liang

    2014-08-01

    Full Text Available Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE. The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications.

  2. Robust non-wetting PTFE surfaces by femtosecond laser machining.

    Science.gov (United States)

    Liang, Fang; Lehr, Jorge; Danielczak, Lisa; Leask, Richard; Kietzig, Anne-Marie

    2014-08-08

    Nature shows many examples of surfaces with extraordinary wettability,which can often be associated with particular air-trapping surface patterns. Here,robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters,both of which make it a strong candidate for industrial applications.

  3. Single-mode surface plasmon distributed feedback lasers.

    Science.gov (United States)

    Karami Keshmarzi, Elham; Tait, R Niall; Berini, Pierre

    2018-03-29

    Single-mode surface plasmon distributed feedback (DFB) lasers are realized in the near infrared using a two-dimensional non-uniform long-range surface plasmon polariton structure. The surface plasmon mode is excited onto a 20 nm-thick, 1 μm-wide metal stripe (Ag or Au) on a silica substrate, where the stripe is stepped in width periodically, forming a 1st order Bragg grating. Optical gain is provided by optically pumping a 450 nm-thick IR-140 doped PMMA layer as the top cladding, which covers the entire length of the Bragg grating, thus creating a DFB laser. Single-mode lasing peaks of very narrow linewidth were observed for Ag and Au DFBs near 882 nm at room temperature. The narrow linewidths are explained by the low spontaneous emission rate into the surface plasmon lasing mode as well as the high quality factor of the DFB structure. The lasing emission is exclusively TM polarized. Kinks in light-light curves accompanied by spectrum narrowing were observed, from which threshold pump power densities can be clearly identified (0.78 MW cm-2 and 1.04 MW cm-2 for Ag and Au DFB lasers, respectively). The Schawlow-Townes linewidth for our Ag and Au DFB lasers is estimated and very narrow linewidths are predicted for the lasers. The lasers are suitable as inexpensive, recyclable and highly coherent sources of surface plasmons, or for integration with other surface plasmon elements of similar structure.

  4. Surface characterization and wear behaviour of laser surface melted AISI 316L stainless steel

    CSIR Research Space (South Africa)

    Kumar, A

    2010-01-01

    Full Text Available The present study concerns an in depth investigation of the influence of laser surface melting of AISI 316L stainless steel using Ar and N2 as shrouding atmosphere. Laser surface melting has been carried out using a 5 kW continuous wave (CW) fibre...

  5. Non-thermal effects on femtosecond laser ablation of polymers extracted from the oscillation of time-resolved reflectivity

    Energy Technology Data Exchange (ETDEWEB)

    Kumada, Takayuki, E-mail: kumada.takayuki@jaea.go.jp; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Nishikino, Masaharu; Yokoyama, Atsushi [Kansai Photon Science Institute, Japan Atomic Energy Agency, Umemidai, Kizugawa, Kyoto 619-0215 (Japan)

    2015-06-01

    The dynamics of femtosecond laser ablation of transparent polymers were examined using time-resolved reflectivity. When these polymers were irradiated by a pump pulse with fluence above the ablation threshold of 0.8–2.0 J/cm{sup 2}, we observed the oscillation of the reflectivity caused by the interference between the reflected probe pulses from the sample surface and the thin layer due to the non-thermal photomechanical effects of spallation. As the fluence of the pump pulse increased, the separation velocity of the thin layer increased from 6 km/s to the asymptotic value of 11 km/s. It is suggested that the velocities are determined by shock-wave velocities of the photo-excited layer.

  6. Study of the laser-induced damage of reflective components in the sub-picosecond regime

    International Nuclear Information System (INIS)

    Sozet, Martin

    2016-01-01

    In this thesis, laser-induced damage phenomenon of reflective components is investigated in the sub-picosecond regime. These components, made of stacks of dielectric materials, are widely used in powerful laser facilities such as PETAL laser. PETAL laser has been built at the CEA-CESTA in France to deliver multi-kJ/500 fs pulses at 1053 nm and reach a power higher than 6 PW. For this kind of laser systems, reflective components are commonly used instead of optics operating in transmission to limit the accumulation of non-linear phase along the beam propagation due to the high intensities. Optical components irradiated by the highest power densities are the pulse compression gratings, transport mirrors and the focusing parabola, located at the end of the laser chain. Nowadays, laser-induced damage is the main factor that limits the overall performances of powerful laser systems. This manuscript presents three study axes to better understand and control damage phenomenon. The first one concerns the conception of reflective optics for the peta-watt applications. The design of new structures has been investigated to reach high diffraction efficiencies in the case of pulse compression gratings and a high reflectivity in the case of mirrors, while reducing the Electric-field enhancement which is one of the causes of the laser-induced damage. The second axis deals with the development of a precise damage metrology with new testing tools which brings new perspectives and a new viewpoint for the assessment of the laser resistance of optical components. Finally, the third axis concerns the study the damage growth after several irradiations in the sub-picosecond regime. The evolution of the damage area during growth sequences is observed and compared to numerical simulations. It enables to improve the understanding in the growth phenomenon. In the end, these studies will allow to develop predictive models of the laser-induced damage and new tools for the conception of

  7. Effect of liquid film on near-threshold laser ablation of a solid surface

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dongsik; Oh, Bukuk; Lee, Ho

    2004-01-30

    Enhancement of material ablation and photoacoustic excitation by an artificially deposited liquid film in the process of pulsed-laser ablation (PLA) is investigated in this paper. Ablation threshold, ablation rate, surface topography, and acoustic-transient emission are also measured for dry and liquid film-coated surfaces. The physical mechanisms of enhanced ablation in the liquid-assisted process are analyzed at relatively low laser fluences with negligible effect of laser-produced plasma. Particularly, correlation between material ablation and acoustic-transient generation is examined. In the experiment, aluminum thin-films and bulk foils are ablated by Q-switched Nd:YAG laser pulses. The dependence of ablation rate and laser-induced topography on liquid film thickness and chemical composition is also examined. Photoacoustic emission is measured by the probe beam deflection method utilizing a CW HeNe laser and a microphone. In comparison with a dry ablation process, the liquid-assisted ablation process results in substantially augmented ablation efficiency and reduced ablation threshold. The results indicate that both increased laser-energy coupling, i.e., lowered reflectance, and amplified photoacoustic excitation in explosive vaporization of liquid are responsible for the enhanced material ablation.

  8. X-Ray Reflectivity from the Surface of a Liquid Crystal:

    DEFF Research Database (Denmark)

    Pershan, P.S.; Als-Nielsen, Jens Aage

    1984-01-01

    X-ray reflectivity from the surface of a nematic liquid crystal is interpreted as the coherent superposition of Fresnel reflection from the surface and Bragg reflection from smectic order induced by the surface. Angular dependence of the Fresnel effect yields information on surface structure....... Measurement of the intensity of diffuse critical scattering relative to the Fresnel reflection yields the absolute value of the critical part of the density-density correlation function....

  9. IMPROVING IMAGE MATCHING BY REDUCING SURFACE REFLECTIONS USING POLARISING FILTER TECHNIQUES

    Directory of Open Access Journals (Sweden)

    N. Conen

    2018-05-01

    Full Text Available In dense stereo matching applications surface reflections may lead to incorrect measurements and blunders in the resulting point cloud. To overcome the problem of disturbing reflexions polarising filters can be mounted on the camera lens and light source. Reflections in the images can be suppressed by crossing the polarising direction of the filters leading to homogeneous illuminated images and better matching results. However, the filter may influence the camera’s orientation parameters as well as the measuring accuracy. To quantify these effects, a calibration and an accuracy analysis is conducted within a spatial test arrangement according to the German guideline VDI/VDE 2634.1 (2002 using a DSLR with and without polarising filter. In a second test, the interior orientation is analysed in more detail. The results do not show significant changes of the measuring accuracy in object space and only very small changes of the interior orientation (Δc ≤ 4 μm with the polarising filter in use. Since in medical applications many tiny reflections are present and impede robust surface measurements, a prototypic trinocular endoscope is equipped with polarising technique. The interior and relative orientation is determined and analysed. The advantage of the polarising technique for medical image matching is shown in an experiment with a moistened pig kidney. The accuracy and completeness of the resulting point cloud can be improved clearly when using polarising filters. Furthermore, an accuracy analysis using a laser triangulation system is performed and the special reflection properties of metallic surfaces are presented.

  10. Laser spectroscopy and photochemistry on metal surfaces, pt.1

    CERN Document Server

    Dai, HL

    1995-01-01

    Using lasers to induce and probe surface processes has the advantages of quantum state specificity, species selectivity, surface sensitivity, fast time-resolution, high frequency resolution, and accessibility to full pressure ranges. These advantages make it highly desirable to use light to induce, control, or monitor surface chemical and physical processes. Recent applications of laser based techniques in studying surface processes have stimulated new developments and enabled the understanding of fundamental problems in energy transfer and reactions. This volume will include discussions on sp

  11. Laser spectroscopy and photochemistry on metal surfaces, pt.2

    CERN Document Server

    Dai, HL

    1995-01-01

    Using lasers to induce and probe surface processes has the advantages of quantum state specificity, species selectivity, surface sensitivity, fast time-resolution, high frequency resolution, and accessibility to full pressure ranges. These advantages make it highly desirable to use light to induce, control, or monitor surface chemical and physical processes. Recent applications of laser based techniques in studying surface processes have stimulated new developments and enabled the understanding of fundamental problems in energy transfer and reactions. This volume will include discussions on sp

  12. NIMONIC 263 microstructure and surface characterization after laser shock peening

    Directory of Open Access Journals (Sweden)

    P. Drobnjak

    2015-07-01

    Full Text Available The Laser Shock Peening (LSP is applied to the surface of Nimonic 263 alloy. The changes in microstructure and surface topography are observed and analyzed by Scanning Electron Microscopy (SEM, profilometer and microhardness tester. Various laser regimes are chosen which provoke effects of both mechanical and thermo-mechanical treatments of the sample surface. The optimal process parameters, that result in the finest microstructure, smooth and clean surface, are determined. Some wanted and unwanted phases leading to the crack formation are observed.

  13. Modification of BSCCO surface by excimer laser annealing

    International Nuclear Information System (INIS)

    Ibi, A.; Akitsu, T.; Matsuzawa, H.

    2002-01-01

    Irradiation of Kr-F excimer laser onto the BSCCO calcined pellets changed their surface to be amorphous. SEM micrographs showed that sintering of the irradiated pellets recrystallized the surface layer and much reduced the intergrain gaps as compared with only sintered pellets, whereas the internal structure of the irradiated pellets remained unchanged. This processing made the surface-layer grains be tightly connected, resulting in the higher critical temperature than the conventionally sintered samples. We can say that excimer laser annealing process is a novel scheme to reduce the surface weak-link of the high Tc superconductors. (author)

  14. A noncontact laser system for measuring soil surface topography

    International Nuclear Information System (INIS)

    Huang, C.; White, I.; Thwaite, E.G.; Bendeli, A.

    1988-01-01

    Soil surface topography profoundly influences runoff hydrodynamics, soil erosion, and surface retention of water. Here we describe an optical noncontact system for measuring soil surface topography. Soil elevation is measured by projecting a laser beam onto the surface and detecting the position of the interception point. The optical axis of the detection system is oriented at a small angle to the incident beam. A low-power HeNe (Helium-Neon) laser is used as the laser source, a photodiode array is used as the laser image detector and an ordinary 35-mm single lens reflex camera provides the optical system to focus the laser image onto the diode array. A wide spectrum of measurement ranges (R) and resolutions are selectable, from 1 mm to 1 m. These are determined by the laser-camera distance and angle, the focal length of the lens, and the sensing length of the diode array and the number of elements (N) contained in the array. The resolution of the system is approximately R/2N. We show for the system used here that this resolution is approximately 0.2%. In the configuration selected, elevation changes of 0.16 mm could be detected over a surface elevation range of 87 mm. The sampling rate of the system is 1000 Hz, which permits soil surfaces to be measured at speeds of up to 1 m s −1 with measurements taken at 1-mm spacing. Measurements of individual raindrop impacts on the soil and of soil surfaces before and after rain show the versatility of the laser surface profiler, which has applications in studies of erosion processes, surface storage and soil trafficability

  15. Surface hardening using cw CO2 laser: laser heat treatment, modelation, and experimental work

    Science.gov (United States)

    Muniz, German; Alum, Jorge

    1996-02-01

    In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.

  16. Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

    Directory of Open Access Journals (Sweden)

    Qinghua Zhu

    2015-04-01

    Full Text Available The near-infrared (NIR absorption below band gap energy of crystalline silicon is significantly increased after the silicon is irradiated with femtosecond laser pulses at a simple experimental condition. The absorption increase in the NIR range primarily depends on the femtosecond laser pulse energy, pulse number, and pulse duration. The Raman spectroscopy analysis shows that after the laser irradiation, the silicon surface consists of silicon nanostructure and amorphous silicon. The femtosecond laser irradiation leads to the formation of a composite of nanocrystalline, amorphous, and the crystal silicon substrate surface with microstructures. The composite has an optical absorption enhancement at visible wavelengths as well as at NIR wavelength. The composite may be useful for an NIR detector, for example, for gas sensing because of its large surface area.

  17. Laser surface alloying of aluminium-transition metal alloys

    International Nuclear Information System (INIS)

    Almeida, A.; Vilar, R.

    1998-01-01

    Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM) alloys. Cr and Mo are particularly interesting alloying elements to produce stable high-strength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO 2 laser . This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloy, over the last years. (Author) 16 refs

  18. Improved ion acceleration via laser surface plasma waves excitation

    Energy Technology Data Exchange (ETDEWEB)

    Bigongiari, A. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); TIPS/LULI, Université Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilée, 94200 Ivry-sur-Seine (France); Raynaud, M. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Riconda, C. [TIPS/LULI, Université Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilée, 94200 Ivry-sur-Seine (France); Héron, A. [CPHT, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France)

    2013-05-15

    The possibility of enhancing the emission of the ions accelerated in the interaction of a high intensity ultra-short (<100 fs) laser pulse with a thin target (<10λ{sub 0}), via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed for laser intensities ranging from 10{sup 19} to 10{sup 20} Wcm{sup −2}μm{sup 2}. The surface wave is resonantly excited by the laser via the coupling with a modulation at the target surface. In the cases where the surface wave is excited, we find an enhancement of the maximum ion energy of a factor ∼2 compared to the cases where the target surface is flat.

  19. Laser surface processing with controlled nitrogen-argon concentration levels for regulated surface life time

    Science.gov (United States)

    Obeidi, M. Ahmed; McCarthy, E.; Brabazon, D.

    2018-03-01

    Laser surface modification can be used to enhance the mechanical properties of a material, such as hardness, toughness, fatigue strength, and corrosion resistance. Surface nitriding is a widely used thermochemical method of surface modification, in which nitrogen is introduced into a metal or other material at an elevated temperature within a furnace. It is used on parts where there is a need for increased wear resistance, corrosion resistance, fatigue life, and hardness. Laser nitriding is a novel method of nitriding where the surface is heated locally by a laser, either in an atmosphere of nitrogen or with a jet of nitrogen delivered to the laser heated site. It combines the benefits of laser modification with those of nitriding. Recent work on high toughness tool steel samples has shown promising results due to the increased nitrogen gas impingement onto the laser heated region. Increased surface activity and nitrogen adsorption was achieved which resulted in a deeper and harder surface compared to conventional hardening methods. In this work, the effects of the laser power, pulse repetition frequency, and overlap percentage on laser surface treatment of 316 L SST steel samples with an argon-nitrogen jet will be presented. Resulting microstructure, phase type, microhardness, and wear resistance are presented.

  20. Quantification of the optical surface reflection and surface roughness of articular cartilage using optical coherence tomography

    Energy Technology Data Exchange (ETDEWEB)

    Saarakkala, Simo; Wang Shuzhe; Huang Yanping; Zheng Yongping [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hong Kong (China)], E-mail: simo.saarakkala@uku.fi, E-mail: ypzheng@ieee.org

    2009-11-21

    Optical coherence tomography (OCT) is a promising new technique for characterizing the structural changes of articular cartilage in osteoarthritis (OA). The calculation of quantitative parameters from the OCT signal is an important step to develop OCT as an effective diagnostic technique. In this study, two novel parameters for the quantification of optical surface reflection and surface roughness from OCT measurements are introduced: optical surface reflection coefficient (ORC), describing the amount of a ratio of the optical reflection from cartilage surface with respect to that from a reference material, and OCT roughness index (ORI) indicating the smoothness of the cartilage surface. The sensitivity of ORC and ORI to detect changes in bovine articular cartilage samples after enzymatic degradations of collagen and proteoglycans using collagenase and trypsin enzymes, respectively, was tested in vitro. A significant decrease (p < 0.001) in ORC as well as a significant increase (p < 0.001) in ORI was observed after collagenase digestion. After trypsin digestion, no significant changes in ORC or ORI were observed. To conclude, the new parameters introduced were demonstrated to be feasible and sensitive to detect typical OA-like degenerative changes in the collagen network. From the clinical point of view, the quantification of OCT measurements is of great interest since OCT probes have been already miniaturized and applied in patient studies during arthroscopy or open knee surgery in vivo. Further studies are still necessary to demonstrate the clinical capability of the introduced parameters for naturally occurring early OA changes in the cartilage.

  1. Laser surface modification of medical grade alloys for reduced heating in a magnetic resonance imaging environment

    Energy Technology Data Exchange (ETDEWEB)

    Benafan, O., E-mail: othmane.benafan@nasa.gov, E-mail: raj@ucf.edu; Vaidyanathan, R., E-mail: othmane.benafan@nasa.gov, E-mail: raj@ucf.edu [Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering, Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816 (United States); Chen, S.-Y.; Kar, A. [Laser-Advanced Materials Processing Laboratory, Center for Research and Education in Optics and Lasers (CREOL), College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States)

    2015-12-15

    Nanoscale surface modification of medical grade metallic alloys was conducted using a neodymium-doped yttrium aluminum garnet laser-based dopant diffusion technique. The objective of this approach was to minimize the induction heating by reducing the absorbed radio frequency field. Such an approach is advantageous in that the dopant is diffused into the alloy and is not susceptible to detachment or spallation as would an externally applied coating, and is expected to not deteriorate the mechanical and electrical properties of the base alloy or device. Experiments were conducted using a controlled environment laser system with the ability to control laser properties (i.e., laser power, spot size, and irradiation time) and dopant characteristics (i.e., temperature, concentration, and pressure). The reflective and transmissive properties of both the doped and untreated samples were measured in a radio frequency (63.86 MHz) magnetic field using a system comprising a high power signal generator, a localized magnetic field source and sensor, and a signal analyzer. The results indicate an increase in the reflectivity of the laser-treated samples compared to untreated samples. The effect of reflectivity on the heating of the alloys is investigated through a mathematical model incorporating Maxwell’s equations and heat conduction.

  2. Changes of electrical conductivity of the metal surface layer by the laser alloying with foreign elements

    Science.gov (United States)

    Kostrubiec, Franciszek; Pawlak, Ryszard; Raczynski, Tomasz; Walczak, Maria

    1994-09-01

    Laser treatment of the surface of materials is of major importance for many fields technology. One of the latest and most significant methods of this treatment is laser alloying consisting of introducing foreign atoms into the metal surface layer during the reaction of laser radiation with the surface. This opens up vast possibilities for the modification of properties of such a layer (obtaining layers of increased microhardness, increased resistance to electroerosion in an electric arc, etc.). Conductivity of the material is a very important parameter in case of conductive materials used for electrical contacts. The paper presents the results of studies on change in electrical conductivity of the surface layer of metals alloyed with a laser. A comparative analysis of conductivity of base metal surface layers prior to and following laser treatment has been performed. Depending on the base metal and the alloying element, optical treatment parameters allowing a required change in the surface layer conductivity have been selected. A very important property of the contact material is its resistance to plastic strain. It affects the real value of contact surface coming into contact and, along with the material conductivity, determines contact resistance and the amount of heat generated in place of contact. These quantities are directly related to the initiation and the course of an arc discharge, hence they also affect resistance to electroerosion. The parameter that reflects plastic properties with loads concentrated on a small surface, as is the case with a reciprocal contact force of two real surfaces with their irregularities being in contact, is microhardness. In the paper, the results of investigations into microhardness of modified surface layers compared with base metal microhardness have been presented.

  3. Evidence of liquid phase during laser-induced periodic surface structures formation induced by accumulative ultraviolet picosecond laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, T. T. D.; Petit, A.; Semmar, N., E-mail: nadjib.semmar@univ-orleans.fr [GREMI, UMR7344, CNRS/University of Orleans, 14 rue d' Issoudun, BP6744, 45067 Orleans Cedex 2 (France); Vayer, M. [ICMN, UMR 7374, CNRS/University of Orleans, 1b rue de la Ferollerie, CS 40059, 45071 Orleans Cedex (France); Sauldubois, A. [CME, UFR Sciences, University of Orleans, 1 Rue de Chartres, BP 6759, 45067 Orleans Cedex 2 (France)

    2015-11-09

    Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10 Hz, and 30 mJ/cm{sup 2}). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation. Atomic Force Microscopy (AFM) analyses have shown the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phase during the LIPSS formation in the picosecond regime.

  4. Directed Acceleration of Electrons from a Solid Surface by Sub-10-fs Laser Pulses

    International Nuclear Information System (INIS)

    Brandl, F.; Hidding, B.; Osterholz, J.; Hemmers, D.; Pretzler, G.; Karmakar, A.; Pukhov, A.

    2009-01-01

    Electrons have been accelerated from solid target surfaces by sub-10-fs laser pulses of 120 μJ energy which were focused to an intensity of 2x10 16 W/cm 2 . The electrons have a narrow angular distribution, and their observed energies exceed 150 keV. We show that these energies are not to be attributed to collective plasma effects but are mainly gained directly via repeated acceleration in the transient field pattern created by incident and reflected laser, alternating with phase-shift-generating scattering events in the solid.

  5. Self-mixing interferometry in vertical-cavity surface-emitting lasers for nanomechanical cantilever sensing

    Science.gov (United States)

    Larsson, David; Greve, Anders; Hvam, Jørn M.; Boisen, Anja; Yvind, Kresten

    2009-03-01

    We have experimentally investigated self-mixing interference produced by the feedback of light from a polymer micrometer-sized cantilever into a vertical-cavity surface-emitting laser for sensing applications. In particular we have investigated how the visibility of the optical output power and the junction voltage depends on the laser injection current and the distance to the cantilever. The highest power visibility obtained from cantilevers without reflective coatings was ˜60%, resulting in a very high sensitivity of 45 mV/nm with a noise floor below 1.2 mV. Different detection schemes are discussed.

  6. Self-mixing interferometry in vertical-cavity surface-emitting lasers for nanomechanical cantilever sensing

    DEFF Research Database (Denmark)

    Larsson, David; Greve, Anders; Hvam, Jørn Märcher

    2009-01-01

    We have experimentally investigated self-mixing interference produced by the feedback of light from a polymer micrometer-sized cantilever into a vertical-cavity surface-emitting laser for sensing applications. In particular we have investigated how the visibility of the optical output power...... and the junction voltage depends on the laser injection current and the distance to the cantilever. The highest power visibility obtained from cantilevers without reflective coatings was 60%, resulting in a very high sensitivity of 45 mV/nm with a noise floor below 1.2 mV. Different detection schemes are discussed....

  7. Laser surface modification of stainless steels for cavitation erosion resistance

    Science.gov (United States)

    Kwok, Chi Tat

    1999-12-01

    Austenitic stainless steel UNS S31603 (Fe -17.6Cr -11.2Ni -2.5Mo -1.4Mn -0.4Si -0.03C) has higher pitting corrosion resistance but lower cavitation erosion resistance than that of UNS S30400. This is because of its lower tendency for strain induced martensitic transformation and higher stacking fault energy as compared with those of UNS S30400. In order to improve its cavitation erosion resistance, surface modification of S31603 was performed by laser surface melting and laser surface alloying using a 2-kW CW Nd-YAG laser and a 3-kW CW CO2 laser. For laser surface melting, austenitic stainless steel UNS S30400, super duplex stainless steel UNS S32760 and martensitic stainless steel UNS S42000 were also investigated for comparison purpose. For laser surface alloying, alloying materials including various elements (Co, Cr, Ni, Mo, Mn, Si & C), alloys (AlSiFe & NiCrSiB), ceramics (Si3N 4, SiC, Cr3C2, TiC, CrB & Cr2O 3) and alloys-ceramics (Co-WC, Ni-WC, Ni-Al2O3, Ni-Cr2C3) were used to modify the surface of S31603. The alloyed surface was achieved first by flame spraying or pre-placing of the alloy powder on the S31603 surface and then followed by laser surface remelting. The cavitation erosion characteristics of laser surface modified specimens in 3.5% NaCl solution at 23°C were studied by means of a 20-kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 mum. In addition, their pitting corrosion behaviour was evaluated by electrochemical techniques. The microstructures, compositions, phase changes and damage mechanisms under cavitation erosion were investigated by optical microscopy, SEM, EDAX and X-ray diffractometry. Mechanical properties such as microhardness profile were also examined. The cavitation erosion resistance Re (reciprocal of the mean depth of penetration rate) of laser surface melted S31603 was found to be improved by 22% and was attributed to the existence of tensile residual stress. Improvement on the Re of S42000 was found to be 8.5 times

  8. Laser Surface Modification of H13 Die Steel using Different Laser Spot Sizes

    Science.gov (United States)

    Aqida, S. N.; Naher, S.; Brabazon, D.

    2011-05-01

    This paper presents a laser surface modification process of AISI H13 tool steel using three sizes of laser spot with an aim to achieve reduced grain size and surface roughness. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). Metallographic study and image analysis were done to measure the grain size and the modified surface roughness was measured using two-dimensional surface profilometer. From metallographic study, the smallest grain sizes measured by laser modified surface were between 0.51 μm and 2.54 μm. The minimum surface roughness, Ra, recorded was 3.0 μm. This surface roughness of the modified die steel is similar to the surface quality of cast products. The grain size correlation with hardness followed the findings correlate with Hall-Petch relationship. The potential found for increase in surface hardness represents an important method to sustain tooling life.

  9. Laser alloying of aluminium to improve surface properties - MSSA 2010

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2010-07-01

    Full Text Available and microstructure of the surface without affecting the bulk properties of the material. The process involves melting the substrate surface and injecting the powder of the alloying material into the melt pool. Process parameters such as laser power, beam spot size...

  10. Osteogenic potential of laser modified and conditioned titanium zirconium surfaces

    Directory of Open Access Journals (Sweden)

    P David Charles

    2016-01-01

    Full Text Available Statement of Problem: The osseointegration of dental implant is related to their composition and surface treatment. Titanium zirconium (TiZr has been introduced as an alternative to the commercially pure titanium and its alloys as dental implant material, which is attributed to its superior mechanical and biological properties. Surface treatments of TiZr have been introduced to enhance their osseointegration ability; however, reliable, easy to use surface modification technique has not been established. Purpose: The purpose of this study was to evaluate and compare the effect of neodymium-doped yttrium aluminum garnet (Nd-YAG laser surface treatment of TiZr implant alloy on their osteogenic potential. Materials and Methods: Twenty disc-shaped samples of 5 mm diameter and 2 mm height were milled from the TiZr alloy ingot. The polished discs were ultrasonically cleaned in distilled water. Ten samples each were randomly selected as Group A control samples and Group B consisted of Nd-YAG laser surface etched and conditioned test samples. These were evaluated for cellular response. Cellular adhesion and proliferation were quantified, and the results were statistically analyzed using nonparametric analysis. Cellular morphology was observed using electron and epiflurosence microscopy. Results: Nd-YAG laser surface modified and conditioned TiZr samples increased the osteogenic potential. Conclusion: Nd-YAG laser surface modification of TiZr, improves the cellular activity, surface roughness, and wettability, thereby increasing the osteogenic potential.

  11. Thin film surface processing by ultrashort laser pulses (USLP)

    NARCIS (Netherlands)

    Scorticati, D.; Skolski, J.Z.P.; Romer, G.R.B.E.; Huis in 't Veld, A.J.; Workum, M.J.; Theelen, M.J.; Zeman, M.

    2012-01-01

    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed

  12. Raman scattering and attenuated-total-reflection studies of surface-plasmon polaritons

    International Nuclear Information System (INIS)

    Kurosawa, K.; Pierce, R.M.; Ushioda, S.; Hemminger, J.C.

    1986-01-01

    We have made in situ measurements of attenuated total reflection (ATR) and Raman scattering from a layered structure consisting of a glass prism, a thin silver film, an MgF 2 spacer, and a liquid mixture whose refractive index is matched to that of MgF 2 . When the incident angle of the laser beam coincides with the ATR angle, the surface-plasmon polariton (SPP) of the silver film is excited resonantly and the Raman scattering intensity of the liquid shows a maximum. The same effect is observed at the frequency of the Stokes scattered light. By measuring the decrease of the Raman scattering intensity of the liquid with increase of the thickness of the MgF 2 spacer layer, we have determined the decay length (l/sub d/) of the SPP field into the liquid. The measured value of l/sub d/ = 1539 A agrees with the calculated value, 1534 A

  13. Laser machining micro-structures on diamond surface with a sub-nanosecond pulsed laser

    Science.gov (United States)

    Wu, Mingtao; Guo, Bing; Zhao, Qingliang

    2018-02-01

    Micro-structure surface on diamond material is widely used in a series of industrial and scientific applications, such as micro-electromechanical systems (MEMS), nanoelectromechanical systems (NEMS), microelectronics, textured or micro-structured diamond machining tools. The efficient machining of micro-structure on diamond surface is urgently demanded in engineering. In this paper, laser machining square micro-structure on diamond surface was studied with a sub-nanosecond pulsed laser. The influences of laser machining parameters, including the laser power, scanning speed, defocusing quantity and scanning pitch, were researched in view of the ablation depth, material removal rate and machined surface topography. Both the ablation depth and material removal rate increased with average laser power. A reduction of the growth rate of the two parameters was induced by the absorption of the laser plasma plume at high laser power. The ablation depth non-linearly decreased with the increasing of the scanning speed while the material removal rate showed an opposite tendency. The increasing of the defocusing quantity induced complex variation of the ablation depth and the material removal rate. The maximum ablation depth and material removal rate were achieved at a defocusing position. The ablation depth and material removal rate oppositely varied about the scanning pitch. A high overlap ratio was meaningful for achieving a smooth micro-structure surface topography. Laser machining with a large defocusing quantity, high laser power and small scanning pitch was helpful for acquiring the desired micro-structure which had a large depth and smooth micro-structure surface topography.

  14. Designing Pulse Laser Surface Modification of H13 Steel Using Response Surface Method

    Science.gov (United States)

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2011-01-01

    This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 μm and 150 μm. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 μm. The maximum hardness achieved was between 728 and 905 HV0.1. These findings are significant to modern development of hard coatings for wear resistant applications.

  15. Ion Production by Laser Impact on a Silver Surface

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Schou, Jørgen

    Even at moderate fluence (0.6 -2.4 J/cm2) laser impact on metals in the UV regime results in a significant number of ions emitted from the surface. Even at this low fluence the particles ejected from a surface interact with each other in a so-called laser ablation plume. The ablated particles...... are largely neutrals at low fluence, but the fraction of ions increases strongly with fluence. We have irradiated silver in a vacuum chamber (~ 10-7 mbar) with a Nd:YAG laser at a wavelength of 355 nm. The ion flow in different directions has been measured with a hemispherical array of Langmuir probes...... range considered is also a typical range for pulsed laser deposition (PLD), by which the material is collected on a suitable substrate for thin film growth. PLD has the advantage compared with other film deposition methods, that even a complicated stoichiometry, e.g. metal oxides or alloys, can...

  16. Landsat surface reflectance quality assurance extraction (version 1.7)

    Science.gov (United States)

    Jones, J.W.; Starbuck, M.J.; Jenkerson, Calli B.

    2013-01-01

    The U.S. Geological Survey (USGS) Land Remote Sensing Program is developing an operational capability to produce Climate Data Records (CDRs) and Essential Climate Variables (ECVs) from the Landsat Archive to support a wide variety of science and resource management activities from regional to global scale. The USGS Earth Resources Observation and Science (EROS) Center is charged with prototyping systems and software to generate these high-level data products. Various USGS Geographic Science Centers are charged with particular ECV algorithm development and (or) selection as well as the evaluation and application demonstration of various USGS CDRs and ECVs. Because it is a foundation for many other ECVs, the first CDR in development is the Landsat Surface Reflectance Product (LSRP). The LSRP incorporates data quality information in a bit-packed structure that is not readily accessible without postprocessing services performed by the user. This document describes two general methods of LSRP quality-data extraction for use in image processing systems. Helpful hints for the installation and use of software originally developed for manipulation of Hierarchical Data Format (HDF) produced through the National Aeronautics and Space Administration (NASA) Earth Observing System are first provided for users who wish to extract quality data into separate HDF files. Next, steps follow to incorporate these extracted data into an image processing system. Finally, an alternative example is illustrated in which the data are extracted within a particular image processing system.

  17. Laser-induced selective copper plating of polypropylene surface

    Science.gov (United States)

    Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

    2016-03-01

    Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

  18. Characterization of a Laser Surface-Treated Martensitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    S.R. Al-Sayed

    2017-05-01

    Full Text Available Laser surface treatment was carried out on AISI 416 machinable martensitic stainless steel containing 0.225 wt.% sulfur. Nd:YAG laser with a 2.2-KW continuous wave was used. The aim was to compare the physical and chemical properties achieved by this type of selective surface treatment with those achieved by the conventional treatment. Laser power of different values (700 and 1000 W with four corresponding different laser scanning speeds (0.5, 1, 2, and 3 m•min−1 was adopted to reach the optimum conditions for impact toughness, wear, and corrosion resistance for laser heat treated (LHT samples. The 0 °C impact energy of LHT samples indicated higher values compared to the conventionally heat treated (CHT samples. This was accompanied by the formation of a hard surface layer and a soft interior base metal. Microhardness was studied to determine the variation of hardness values with respect to the depth under the treated surface. The wear resistance at the surface was enhanced considerably. Microstructure examination was characterized using optical and scanning electron microscopes. The corrosion behavior of the LHT samples was also studied and its correlation with the microstructures was determined. The corrosion data was obtained in 3.5% NaCl solution at room temperature by means of a potentiodynamic polarization technique.

  19. Characterization of a Laser Surface-Treated Martensitic Stainless Steel.

    Science.gov (United States)

    Al-Sayed, S R; Hussein, A A; Nofal, A A; Hassab Elnaby, S I; Elgazzar, H

    2017-05-29

    Laser surface treatment was carried out on AISI 416 machinable martensitic stainless steel containing 0.225 wt.% sulfur. Nd:YAG laser with a 2.2-KW continuous wave was used. The aim was to compare the physical and chemical properties achieved by this type of selective surface treatment with those achieved by the conventional treatment. Laser power of different values (700 and 1000 W) with four corresponding different laser scanning speeds (0.5, 1, 2, and 3 m•min-1) was adopted to reach the optimum conditions for impact toughness, wear, and corrosion resistance for laser heat treated (LHT) samples. The 0 °C impact energy of LHT samples indicated higher values compared to the conventionally heat treated (CHT) samples. This was accompanied by the formation of a hard surface layer and a soft interior base metal. Microhardness was studied to determine the variation of hardness values with respect to the depth under the treated surface. The wear resistance at the surface was enhanced considerably. Microstructure examination was characterized using optical and scanning electron microscopes. The corrosion behavior of the LHT samples was also studied and its correlation with the microstructures was determined. The corrosion data was obtained in 3.5% NaCl solution at room temperature by means of a potentiodynamic polarization technique.

  20. Laser Surface Alloying of Aluminum for Improving Acid Corrosion Resistance

    Science.gov (United States)

    Jiru, Woldetinsay Gutu; Sankar, Mamilla Ravi; Dixit, Uday Shanker

    2018-04-01

    In the present study, laser surface alloying of aluminum with magnesium, manganese, titanium and zinc, respectively, was carried out to improve acid corrosion resistance. Laser surface alloying was conducted using 1600 and 1800 W power source using CO2 laser. Acid corrosion resistance was tested by dipping the samples in a solution of 2.5% H2SO4 for 200 h. The weight loss due to acid corrosion was reduced by 55% for AlTi, 41% for AlMg alloy, 36% for AlZn and 22% for AlMn alloy. Laser surface alloyed samples offered greater corrosion resistance than the aluminum substrate. It was observed that localized pitting corrosion was the major factor to damage the surface when exposed for a long time. The hardness after laser surface alloying was increased by a factor of 8.7, 3.4, 2.7 and 2 by alloying with Mn, Mg, Ti and Zn, respectively. After corrosion test, hardness was reduced by 51% for AlTi sample, 40% for AlMg sample, 41.4% for AlMn sample and 33% for AlZn sample.

  1. Refining femtosecond laser induced periodical surface structures with liquid assist

    International Nuclear Information System (INIS)

    Jiao, L.S.; Ng, E.Y.K.; Zheng, H.Y.

    2013-01-01

    Highlights: ► LIPSS on silicon wafer was made in air and in ethanol environment. ► Ethanol environment produce cleaner surface ripples. ► Ethanol environment decrease spatial wavelength of the LIPSS by 30%. ► More number of pulses produce smaller spatial wavelength in air. ► Number of pulses do not influence spatial wavelength in ethanol environment. - Abstract: Laser induced periodic surface structures were generated on silicon wafer using femtosecond laser. The medium used in this study is both air and ethanol. The laser process parameters such as wavelength, number of pulse, laser fluence were kept constant for both the mediums. The focus of the study is to analyze spatial wavelength. When generating surface structures with air as a medium and same process parameter of the laser, spatial wavelength results showed a 30% increase compared to ethanol. The cleanliness of the surface generated using ethanol showed considerably less debris than in air. The results observed from the above investigation showed that the medium plays a predominant role in the generation of surface structures.

  2. Laser techniques for radioactive decontamination gives metallic surfaces

    International Nuclear Information System (INIS)

    Escobar Alracon, L.; Molina, G.; Vizuet Gonzalez, J.

    1998-01-01

    In this work it presented the prototype for system decontamination at diverse component with removable superficial contamination, using the technique gives laser ablation, for the evaporation at the pollutant. It discusses the principle in the fact that system, as well as the different elements that compose it. The are presented the obtained results when irradiating with a laser a surface without radioactive contamination to verify the system operation

  3. Laser assisted fabrication of random rough surfaces for optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Brissonneau, V., E-mail: vincent.brissonneau@im2np.fr [Thales Optronique SA, Avenue Gay-Lussac, 78995 Elancourt (France); Institut Materiaux Microelectronique Nanosciences de Provence, Aix Marseille Universite, Avenue Escadrille Normandie Niemen, 13397 Marseille (France); Escoubas, L. [Institut Materiaux Microelectronique Nanosciences de Provence, Aix Marseille Universite, Avenue Escadrille Normandie Niemen, 13397 Marseille (France); Flory, F. [Institut Materiaux Microelectronique Nanosciences de Provence, Ecole Centrale Marseille, Marseille (France); Berginc, G. [Thales Optronique SA, Avenue Gay-Lussac, 78995 Elancourt (France); Maire, G.; Giovannini, H. [Institut Fresnel, Aix Marseille Universite, Avenue Escadrille Normandie Niemen, 13397 Marseille (France)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Random rough surfaces are photofabricated using an argon ion laser. Black-Right-Pointing-Pointer Speckle and surface correlation function are linked. Black-Right-Pointing-Pointer Exposure beam is modified allowing tuning the correlation. Black-Right-Pointing-Pointer Theoretical examples are presented. Black-Right-Pointing-Pointer Experimental results are compared with theoretical expectation. - Abstract: Optical surface structuring shows great interest for antireflective or scattering properties. Generally, fabricated surface structures are periodical but random surfaces that offer new degrees of freedom and possibilities by the control of their statistical properties. We propose an experimental method to create random rough surfaces on silicon by laser processing followed by etching. A photoresist is spin coated onto a silicon substrate and then exposed to the scattering of a modified laser beam. The beam modification is performed by using a micromirror matrix allowing laser beam shaping. An example of tuning is presented. An image composed of two white circles with a black background is displayed and the theoretical shape of the correlation is calculated. Experimental surfaces are elaborated and the correlation function calculated from height mapping. We finally compared the experimental and theoretical correlation functions.

  4. Laser Decontamination of Surfaces Contaminated with Cs+ Ion

    International Nuclear Information System (INIS)

    Baigalmaaa, B.; Won, H. J.; Moon, J. K.; Jung, C. H.; Lee, K. W.; Hyun, J. H.

    2008-01-01

    Laser decontamination technology has been proven to be an efficient method for a surface modification of metals and concretes contaminated with radioactive isotopes. Furthermore, the generation of a secondary waste is negligible. The radioactivity of hot cells in the DFDF (Dupic Fuel Development Facility) is presumed to be very high and the predominant radionuclide is Cs-137. A series of laser decontamination studies by a fabricated Q-switched Nd:YAG laser system were performed on stainless steel specimens artificially contaminated with Cs+ ion. Decontamination characteristics of the stainless steel were analyzed by SEM and EPMA

  5. In situ surface roughness measurement using a laser scattering method

    Science.gov (United States)

    Tay, C. J.; Wang, S. H.; Quan, C.; Shang, H. M.

    2003-03-01

    In this paper, the design and development of an optical probe for in situ measurement of surface roughness are discussed. Based on this light scattering principle, the probe which consists of a laser diode, measuring lens and a linear photodiode array, is designed to capture the scattered light from a test surface with a relatively large scattering angle ϕ (=28°). This capability increases the measuring range and enhances repeatability of the results. The coaxial arrangement that incorporates a dual-laser beam and a constant compressed air stream renders the proposed system insensitive to movement or vibration of the test surface as well as surface conditions. Tests were conducted on workpieces which were mounted on a turning machine that operates with different cutting speeds. Test specimens which underwent different machining processes and of different surface finish were also studied. The results obtained demonstrate the feasibility of surface roughness measurement using the proposed method.

  6. Variability of Surface Reflection Amplitudes of GPR Horn Antenna Depending on Distance between Antenna and Surface

    Directory of Open Access Journals (Sweden)

    Komačka Jozef

    2016-05-01

    Full Text Available The study focused on variability of surface reflections amplitudes of GPR horn antenna in relation to distance between an antenna and a surface is presented in the paper. The air-coupled antenna with the central frequency of 1 GHz was used in the investigation. Four types of surfaces (dry pavement, wet pavement, metal plate and composite layer from gypsum and wood were tested. The distance of antenna above the surfaces was changed in the range from 37.5 cm to 53.5 cm. The amplitudes of negative and positive peaks and their variability were analysed in relation to the distance of antenna above the surfaces. Moreover, the influence of changes in the peaks of negative and positive amplitudes on the total amplitudes was assessed. It was found out the amplitudes of negative peaks for all investigated surfaces were relatively consistent in the range from 40.5 cm to 48.5 cm and the moderate decline was identified in the case of amplitudes of positive peaks in the range of distances from 37.5 cm to 51.5 cm. This decline influences the tendency of total amplitudes. Based on the results of analysis it can be stated the distance of air-coupled antenna above the surface can influence the value of total amplitude and the differences depend on the type of surface.

  7. Optodynamics: dynamic aspects of laser beam-surface interaction

    International Nuclear Information System (INIS)

    Možina, J; Diaci, J

    2012-01-01

    This paper presents a synthesis of the results of our original research in the area of laser-material interaction and pulsed laser material processing with a special emphasis on the dynamic aspects of laser beam-surface interaction, which include the links between the laser material removal and the resulting material motion. In view of laser material processing, a laser beam is not only considered as a tool but also as a generator of information about the material transformation. The information is retained and conveyed by different kinds of optically induced mechanical waves. Several generation/detection schemes have been developed to extract this information, especially in the field of non-destructive material evaluation. Blast and acoustic waves, which propagate in the air surrounding the work-piece, have been studied using microphone detection as well as various setups of the laser beam deflection probe. Stress waves propagating through the work-piece have been studied using piezoelectric transducers and laser interferometers.

  8. The Effect of Non-Lambertian Surface Reflectance on Aerosol Radiative Forcing

    Energy Technology Data Exchange (ETDEWEB)

    Ricchiazzi, P.; O' Hirok, W.; Gautier, C.

    2005-03-18

    Surface reflectance is an important factor in determining the strength of aerosol radiative forcing. Previous studies of radiative forcing assumed that the reflected surface radiance is isotropic and does not depend on incident illumination angle. This Lambertian reflection model is not a very good descriptor of reflectance from real land and ocean surfaces. In this study we present computational results for the seasonal average of short and long wave aerosol radiative forcing at the top of the atmosphere and at the surface. The effect of the Lambertian assumption is found through comparison with calculations using a more detailed bi-direction reflectance distribution function (BRDF).

  9. Laser applications in materials processing

    International Nuclear Information System (INIS)

    Ready, J.F.

    1980-01-01

    The seminar focused on laser annealing of semiconductors, laser processing of semiconductor devices and formation of coatings and powders, surface modification with lasers, and specialized laser processing methods. Papers were presented on the theoretical analysis of thermal and mass transport during laser annealing, applications of scanning continuous-wave and pulsed lasers in silicon technology, laser techniques in photovoltaic applications, and the synthesis of ceramic powders from laser-heated gas-phase reactants. Other papers included: reflectance changes of metals during laser irradiation, surface-alloying using high-power continuous lasers, laser growth of silicon ribbon, and commercial laser-shock processes

  10. F2 excimer laser (157 nm) radiation modification and surface ablation of PHEMA hydrogels and the effects on bioactivity: Surface attachment and proliferation of human corneal epithelial cells

    International Nuclear Information System (INIS)

    Zainuddin; Chirila, Traian V.; Barnard, Zeke; Watson, Gregory S.; Toh, Chiong; Blakey, Idriss; Whittaker, Andrew K.; Hill, David J.T.

    2011-01-01

    Physical and chemical changes at the surface of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified by ablation with an F 2 excimer laser were investigated experimentally. An important observation was that only the outer exposed surface layers of the hydrogel were affected by the exposure to 157 nm radiation. The effect of the surface changes on the tendency of cells to adhere to the PHEMA was also investigated. A 0.5 cm 2 area of the hydrogel surfaces was exposed to laser irradiation at 157 nm to fluences of 0.8 and 4 J cm -2 . The changes in surface topography were analysed by light microscopy and atomic force microscopy, while the surface chemistry was characterized by attenuated total reflection infrared and X-ray photoelectron spectroscopies. Cell-interfacial interactions were examined based on the proliferation of human corneal limbal epithelial (HLE) cells cultured on the laser-modified hydrogels, and on the unexposed hydrogels and tissue culture plastic for comparison. It was observed that the surface topography of laser-exposed hydrogels showed rippled patterns with a surface roughness increasing at the higher exposure dose. The changes in surface chemistry were affected not only by an indirect effect of hydrogen and hydroxyl radicals, formed by water photolysis, on the PHEMA, but also by the direct action of laser radiation on PHEMA if the surface layers of the gel become depleted of water. The laser treatment led to a change in the surface characteristics, with a lower concentration of ester side-chains and the formation of new oxygenated species at the surface. The surface also became more hydrophobic. Most importantly, the surface chemistry and the newly created surface topographical features were able to improve the attachment, spreading and growth of HLE cells.

  11. The laser surface alloying of the surface layer of the plain carbon steel

    International Nuclear Information System (INIS)

    Woldan, A.; Kusinski, J.

    2003-01-01

    The paper describes the microstructure and properties (chemical composition, microhardness and the effect of tribological test of the surface laser alloyed layer with tantalum. Scanning electron microscopy examinations show structure, which consist of martensite and Ta2C carbides. Samples covered with Ta and the carbon containing binder showed after laser alloying higher hardness than in case of using silicon-containing binder. (author)

  12. Photoelectron emission from metal surfaces by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Faraggi, M. N.; Gravielle, M. S.; Silkin, V. M.

    2006-01-01

    Electron emission from metal surfaces produced by short laser pulses is studied within the framework of the distorted-wave formulation. The proposed approach, named surface-Volkov (SV) approximation, makes use of the band-structure based (BSB) model and the Volkov phase to describe the interaction of the emitted electron with the surface and the external electric field, respectively. The BSB model provides a realistic representation of the surface, based on a model potential that includes the main features of the surface band structure. The SV method is applied to evaluate the photoelectron emission from the valence band of Al(111). Angular and energy distributions are investigated for different parameters of the laser pulse, keeping in all cases the carrier frequency larger than the plasmon one

  13. Laser surface modification of Ti implants to improve osseointegration

    International Nuclear Information System (INIS)

    Marticorena, M; Corti, G; Olmedo, D; Guglielmotti, M B; Duhalde, S

    2007-01-01

    Commercially Pure Titanium foils, were irradiated using a pulsed Nd:YAG laser under ambient air, in order to produce and characterize a well controlled surface texture (roughness and waviness) that enhances osseointegration. To study the 'peri-implant' reparative process response, the laser treated Ti foils were implanted in the tibia of 10 male Wistar rats. At 14 days post-implantation, the histological analysis showed a tendency to more bone formation compared to the untreated control implants. The formation of a layer of TiN on the surface and the obtained roughness, have been demonstrated to improve bone response

  14. Surface alloying of nickel based superalloys by laser

    International Nuclear Information System (INIS)

    Rodriguez, G.P.; Garcia, I.; Damborenea, J.J. de

    1998-01-01

    Ni based superalloys present a high oxidation resistance at high temperature as well as good mechanical properties. But new technology developments force to research in this materials to improve their properties at high temperature. In this work, two Ni based superalloys (Nimonic 80A and Inconel 600) were surface alloyed with aluminium using a high power laser. SEM and EDX were used to study the microstructure of the obtained coatings. Alloyed specimens were tested at 1.273 K between 24 and 250 h. Results showed the generation of a protective and continuous coating of alumina on the laser treated specimens surface that can improve oxidation resistance. (Author) 8 refs

  15. Modeling of laser damage initiated by surface contamination

    International Nuclear Information System (INIS)

    Feit, M.D.; Rubenchik, A.M.; Faux, D.R.; Riddle, R.A.; Shapiro, A.; Eder, D.C.; Penetrante, B.M.; Milam, D.; Genin, F.Y.; Kozlowski, M.R.

    1996-11-01

    The authors are engaged in a comprehensive effort to understand and model the initiation and growth of laser damage initiated by surface contaminants. This includes, for example, the initial absorption by the contaminant, heating and plasma generation, pressure and thermal loading of the transparent substrate, and subsequent shockwave propagation, 'splashing' of molten material and possible spallation, optical propagation and scattering, and treatment of material fracture. The integration use of large radiation hydrodynamics codes, optical propagation codes and material strength codes enables a comprehensive view of the damage process The following picture of surface contaminant initiated laser damage is emerging from our simulations

  16. Virtual-stereo fringe reflection technique for specular free-form surface testing

    Science.gov (United States)

    Ma, Suodong; Li, Bo

    2016-11-01

    Due to their excellent ability to improve the performance of optical systems, free-form optics have attracted extensive interest in many fields, e.g. optical design of astronomical telescopes, laser beam expanders, spectral imagers, etc. However, compared with traditional simple ones, testing for such kind of optics is usually more complex and difficult which has been being a big barrier for the manufacture and the application of these optics. Fortunately, owing to the rapid development of electronic devices and computer vision technology, fringe reflection technique (FRT) with advantages of simple system structure, high measurement accuracy and large dynamic range is becoming a powerful tool for specular free-form surface testing. In order to obtain absolute surface shape distributions of test objects, two or more cameras are often required in the conventional FRT which makes the system structure more complex and the measurement cost much higher. Furthermore, high precision synchronization between each camera is also a troublesome issue. To overcome the aforementioned drawback, a virtual-stereo FRT for specular free-form surface testing is put forward in this paper. It is able to achieve absolute profiles with the help of only one single biprism and a camera meanwhile avoiding the problems of stereo FRT based on binocular or multi-ocular cameras. Preliminary experimental results demonstrate the feasibility of the proposed technique.

  17. Femtosecond laser surface structuring of molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Mthunzi, P. [Council for Scientific and Industrial Research (CSIR), Biophotonics Lab: National Laser Centre Pretoria, 0001 (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Itala (Italy); Sechoghela, P.; Mongwaketsi, N. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)–CNR, Piazza Leanardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa)

    2015-10-30

    Highlights: • Color change of the molybdenum thin film from shinny to violet–yellowish color after laser irradiation at various laser powers. • Formation of the molybdenum dioxide coating after laser exposure, as confirmed by the X-ray diffraction spectrometry. • Selective solar absorbing nature of the laser exposed films. • Study of the binding energies is presented in this contribution using the XPS spectrometry. - Abstract: This contribution reports on the femtosecond surface structuring of molybdenum thin coatings deposited by electron beam evaporation onto Corning glass substrates. The 1-D type periodic grating lines created by such an ablation showed that the widths of the shallow grooves followed a logarithmic dependence with the laser energy incident on the molybdenum film. The electronic valence “x” of the created oxide surface layer MoO{sub x} was found to be incident laser power dependent via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction investigations. Such a photo-induced MoO{sub x}–Mo nanocomposite exhibited effective selective solar absorption in the UV–vis–IR spectral range.

  18. Surface Analysis of the Laser Cleaned Metal Threads

    Science.gov (United States)

    Sokhan, M.; Hartog, F.; McPhail, D.

    The laser cleaning of the tarnished silver threads was carried out using Nd:YAG laser radiation at IR (1064 nm) and visible wavelengths (532 nm). The preliminary tests were made on the piece of silk with the silver embroidery with the clean and tarnished areas. FIBS and SIMS analysis were used for analysing the condition of the surface before and after laser irradiation. It was found that irradiation below 0.4 J/cm-2 and higher than 1.0 J/cm-2 fluences aggravates the process of tarnishing and leads to the yellowing effect. The results of preliminary tests were used for finding the optimum cleaning regime for the laser cleaning of the real museum artefact: "Women Riding Jacket" dated to the beginning of 18th century.

  19. Impact of initial surface parameters on the final quality of laser micro-polished surfaces

    Science.gov (United States)

    Chow, Michael; Bordatchev, Evgueni V.; Knopf, George K.

    2012-03-01

    Laser micro-polishing (LμP) is a new laser-based microfabrication technology for improving surface quality during a finishing operation and for producing parts and surfaces with near-optical surface quality. The LμP process uses low power laser energy to melt a thin layer of material on the previously machined surface. The polishing effect is achieved as the molten material in the laser-material interaction zone flows from the elevated regions to the local minimum due to surface tension. This flow of molten material then forms a thin ultra-smooth layer on the top surface. The LμP is a complex thermo-dynamic process where the melting, flow and redistribution of molten material is significantly influenced by a variety of process parameters related to the laser, the travel motions and the material. The goal of this study is to analyze the impact of initial surface parameters on the final surface quality. Ball-end micromilling was used for preparing initial surface of samples from H13 tool steel that were polished using a Q-switched Nd:YAG laser. The height and width of micromilled scallops (waviness) were identified as dominant parameter affecting the quality of the LμPed surface. By adjusting process parameters, the Ra value of a surface, having a waviness period of 33 μm and a peak-to-valley value of 5.9 μm, was reduced from 499 nm to 301 nm, improving the final surface quality by 39.7%.

  20. AFM study of the effects of laser surface remelting on the morphology of Al-Fe aerospace alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pariona, Moises Meza, E-mail: mmpariona@uepg.br [Graduate Program in Engineering and Materials Science, State University of Ponta Grossa (UEPG), Ponta Grossa 84010-919, PR (Brazil); Teleginski, Viviane; Santos, Kelly dos; Leandro Ribeiro dos Santos, Everton; Aparecida de Oliveira Camargo de Lima, Angela [Graduate Program in Engineering and Materials Science, State University of Ponta Grossa (UEPG), Ponta Grossa 84010-919, PR (Brazil); Riva, Rudimar [Department of Aerospace Science and Technology, Institute for Advanced Studies (IEAv), Sao Jose dos Campos 12227-000, SP (Brazil)

    2012-12-15

    Laser beam welding has recently been incorporated into the fabrication process of aircraft and automobile structures. Surface roughness is an important parameter of product quality that strongly affects the performance of mechanical parts, as well as production costs. This parameter influences the mechanical properties such as fatigue behavior, corrosion resistance, creep life, etc., and other functional characteristics such as friction, wear, light reflection, heat transmission, lubrification, electrical conductivity, etc. The effects of laser surface remelting (LSR) on the morphology of Al-Fe aerospace alloys were examined before and after surface treatments, using optical microscopy (OM), scanning electron microscopy (SEM), low-angle X-ray diffraction (LA-XRD), atomic force microscopy (AFM), microhardness measurements (Vickers hardness), and cyclic voltammetry. This analysis was performed on both laser-treated and untreated sanded surfaces, revealing significant differences. The LA-XRD analysis revealed the presence of alumina, simple metals and metastable intermetallic phases, which considerably improved the microhardness of laser-remelted surfaces. The morphology produced by laser surface remelting enhanced the microstructure of the Al-Fe alloys by reducing their roughness and increasing their hardness. The treated surfaces showed passivity and stability characteristics in the electrolytic medium employed in this study. - Highlights: Black-Right-Pointing-Pointer The samples laser-treated and untreated showed significant differences. Black-Right-Pointing-Pointer The La-XRD revealed the presence of alumina in Al-1.5 wt.% Fe. Black-Right-Pointing-Pointer The laser-treated reducing the roughness and increasing the hardness. Black-Right-Pointing-Pointer The laser-treated surfaces showed characteristic passive in the electrolytic medium. Black-Right-Pointing-Pointer The laser-treated is a promising technique for applications technological.

  1. UV-laser-based longitudinal illuminated diffuser (LID) incorporating diffractive and Lambertian reflectance for the disinfection of beverages

    Science.gov (United States)

    Lizotte, Todd

    2010-08-01

    A novel laser beam shaping system was designed to demonstrate the potential of using high power UV laser sources for large scale disinfection of liquids used in the production of food products, such as juices, beer, milk and other beverage types. The design incorporates a patented assembly of optical components including a diffractive beam splitting/shaping element and a faceted pyramidal or conically shaped Lambertian diffuser made from a compression molded PTFE compounds. When properly sintered to an appropriate density, as an example between 1.10 and 1.40 grams per cubic centimeter, the compressed PTFE compounds show a ~99% reflectance at wavelengths ranging from 300 nm to 1500 nm, and a ~98.5% refection of wavelengths from 250 nm to 2000 nm [1]. The unique diffuser configuration also benefits from the fact that the PTFE compounds do not degrade when exposed to ultraviolet radiation as do barium sulfate materials and silver or aluminized mirror coatings [2]. These components are contained within a hermetically sealed quartz tube. Once assembled a laser beam is directed through one end of the tube. This window takes the form of a computer generated diffractive splitter or other diffractive shaper element to split the laser beam into a series of spot beamlets, circular rings or other geometric shapes. As each of the split beamlets or rings cascade downward, they illuminate various points along the tapered PTFE cone or faceted pyramidal form. As they strike the surface they each diffuse in a Lambertian reflectance pattern creating a pseudo-uniform circumferential illuminator along the length of the quartz tube enclosing the assembly. The compact tubular structure termed Longitudinal Illuminated Diffuser (LID) provides a unique UV disinfection source that can be placed within a centrifugal reactor or a pipe based reactor chamber. This paper will review the overall design principle, key component design parameters, preliminary analytic and bench operational testing

  2. Modification of Surface Energy via Direct Laser Ablative Surface Patterning

    Science.gov (United States)

    Wohl, Christopher J., Jr. (Inventor); Belcher, Marcus A. (Inventor); Connell, John W. (Inventor); Hopkins, John W. (Inventor)

    2015-01-01

    Surface energy of a substrate is changed without the need for any template, mask, or additional coating medium applied to the substrate. At least one beam of energy directly ablates a substrate surface to form a predefined topographical pattern at the surface. Each beam of energy has a width of approximately 25 micrometers and an energy of approximately 1-500 microJoules. Features in the topographical pattern have a width of approximately 1-500 micrometers and a height of approximately 1.4-100 micrometers.

  3. Problems in laser repair welding of polished surfaces

    Directory of Open Access Journals (Sweden)

    A. Skumavc

    2014-10-01

    Full Text Available This paper presents problems in laser repair welding of the tools for injection moulding of plastics and light metals. Tools for injection moulding of the car headlamps are highly polished in order to get a desirable quality of the injected part. Different light metals, glasses, elastomers, thermoplastics and thermosetting polymers are injected into the die cavity under high pressures resulting in the surface damages of the tool. Laser welding is the only suitable repair welding technique due to the very limited sputtering during deposition of the filler metal. Overlapping of the welds results in inhomogeneous hardness of the remanufactured surface. Results have shown strong correlation between hardness and surface waviness after final polishing of the repair welded surface.

  4. Laser polishing for topography management of accelerator cavity surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Liang [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Klopf, J. Mike [College of William and Mary, Williamsburg, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Kelley, Michael J. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2015-07-20

    Improved energy efficiency and reduced cost are greatly desired for advanced particle accelerators. Progress toward both can be made by atomically-smoothing the interior surface of the niobium superconducting radiofrequency accelerator cavities at the machine's heart. Laser polishing offers a green alternative to the present aggressive chemical processes. We found parameters suitable for polishing niobium in all surface states expected for cavity production. As a result, careful measurement of the resulting surface chemistry revealed a modest thinning of the surface oxide layer, but no contamination.

  5. Reflection and diffraction of atomic de Broglie waves by evanescent laser waves. Bare-state method

    International Nuclear Information System (INIS)

    Feng, Xiaoping; Witte, N.S.; Hollenberg, C.L.; Opat, G.

    1994-01-01

    Two methods are presented for the investigation of the reflection and diffraction of atoms by gratings formed either by standing or travelling evanescent laser waves. Both methods use the bare-state rather than dressed-state picture. One method is based on the Born series, whereas the other is based on the Laplace transformation of the coupled differential equations. The two methods yield the same theoretical expressions for the reflected and diffracted atomic waves in the whole space including the interaction and the asymptotic regions. 1 ref., 1 fig

  6. Intracavity Laser Refractometry In Reflection: Development And Implementation In Biomedical Investigations

    International Nuclear Information System (INIS)

    Gonchukov, S. A.

    2010-01-01

    The Intracavity Laser Refractometry in Reflection (ILRR) method is developed for precise investigation of the processes on an interface of different media in real time. This method is very attractive for the study of biological liquids. It is based on the control of two-mode phase-anisotropic laser spectrum. In the aggregate the values of the sensitivity, time of measuring, potential parameters of investigated media of ILRR method correspond to the best results in optical refractometry. The absolute value of refractive index correlates with the course of different diseases. It can serve the objective parameter for an estimation of a level of illness processes in organism and drug efficiency. In result of the investigation of the photoresponse of the blood to low-level laser irradiation both the slow thermal effect and fast biophysical effect were discovered. The refractive index behaviour in real time allows the photoacceptors and maximum therapeutic doses on organism, cellular, and molecular levels to be determined.

  7. Measurement of stress-induced birefringence in glasses based on reflective laser feedback effect

    Science.gov (United States)

    Haisha, Niu; YanXiong, Niu; Jiyang, Li

    2017-02-01

    A glass birefringence measurement system utilizing the reflective laser feedback (RLF) effect is presented. The measurement principle is analyzed based on the equivalent cavity of a Fabry-Perot interferometer, and the experiments are conducted with a piece of quartz glass with applied extrusion force. In the feedback system, aluminum film used as a feedback mirror is affixed to the back of the sample. When the light is reflected back into the cavity, as the reinjected light is imprinted with the birefringence information in the sample, the gain and polarization states of the laser are modulated. The variation of optical power and polarization states hopping is monitored to obtain the magnitude of the stress. The system has advantages such as simplicity and low-cost with a precision of 1.9 nm. Moreover, by adjusting the position of the aluminum, large-area samples can be measured anywhere at any place.

  8. Spectrum of reflected light by self-focusing of light in a laser plasma

    International Nuclear Information System (INIS)

    Gorbunov, L.M.

    1983-01-01

    The spectrum of the radiation reflected by a laser-produced plasma is considered. In this situation, self-focusing occurs and a region of low density (caviton) is formed. It is shown that the process leads to a considerable broadening of the spectrum on the ''red'' side, and to the appearance of a line structure in the spectrum. The results can explain data for the reflected light spectrum [L. M. Gorbunov et al., FIAN Preprint No. 126 (1979)] as being due to the nonstationary self-focusing of light in a laser-produced plasma that has recently been observed [V. L. Artsimovich et al., FIAN Preprint No. 252 (1981); Sov. Phys. Doklady 27, 618 (1982)

  9. Surface texturing of sialon ceramic by femtosecond pulsed laser

    CSIR Research Space (South Africa)

    Tshabalala, Lerato C

    2017-01-01

    Full Text Available AlONSi(sub3)N(sub4) ceramic using the Ti: Sapphire Femtosecond laser system was investigated. Parametric analysis was conducted using surface drilling, unidirectional and cross-hatching machining procedures performed on the substrate at a varied power...

  10. Surface plasmon quantum cascade lasers as terahertz local oscillators

    NARCIS (Netherlands)

    Hajenius, M.; Khosropanah, P.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Barbieri, S.; Dhillon, S.; Filloux, P.; Sirtori, C.; Ritchie, D. A.; Beere, H. E.

    2008-01-01

    We characterize a heterodyne receiver based on a surface-plasmon waveguide quantum cascade laser (QCL) emitting at 2.84 THz as a local oscillator, and an NbN hot electron bolometer as a mixer. We find that the envelope of the far-field pattern of the QCL is diffraction-limited and superimposed onto

  11. Developing a more useful surface quality metric for laser optics

    Science.gov (United States)

    Turchette, Quentin; Turner, Trey

    2011-02-01

    Light scatter due to surface defects on laser resonator optics produces losses which lower system efficiency and output power. The traditional methodology for surface quality inspection involves visual comparison of a component to scratch and dig (SAD) standards under controlled lighting and viewing conditions. Unfortunately, this process is subjective and operator dependent. Also, there is no clear correlation between inspection results and the actual performance impact of the optic in a laser resonator. As a result, laser manufacturers often overspecify surface quality in order to ensure that optics will not degrade laser performance due to scatter. This can drive up component costs and lengthen lead times. Alternatively, an objective test system for measuring optical scatter from defects can be constructed with a microscope, calibrated lighting, a CCD detector and image processing software. This approach is quantitative, highly repeatable and totally operator independent. Furthermore, it is flexible, allowing the user to set threshold levels as to what will or will not constitute a defect. This paper details how this automated, quantitative type of surface quality measurement can be constructed, and shows how its results correlate against conventional loss measurement techniques such as cavity ringdown times.

  12. Vertical-cavity surface-emitting lasers for medical diagnosis

    DEFF Research Database (Denmark)

    Ansbæk, Thor

    This thesis deals with the design and fabrication of tunable Vertical-Cavity Surface-Emitting Lasers (VCSELs). The focus has been the application of tunable VCSELs in medical diagnostics, specifically OCT. VCSELs are candidates as light sources for swept-source OCT where their high sweep rate, wide...

  13. Navy Shipboard Lasers for Surface, Air, and Missile Defense: Background and Issues for Congress

    Science.gov (United States)

    2013-06-27

    fiber SSL effort is called the Tactical Laser System ( TLS ). Among DOD’s multiple efforts to develop slab SSLs for military use was the Maritime Laser...Missile Defense Congressional Research Service 11 Tactical Laser System Another Navy fiber SSL effort is the Tactical Laser System ( TLS )—a laser...and DOD have conducted development work on three principal types of lasers for potential use on Navy surface ships—fiber solid state lasers ( SSLs

  14. Laser photo-reflectance characterization of resonant nonlinear electro-refraction in thin semiconductor films

    International Nuclear Information System (INIS)

    Chism, Will; Cartwright, Jason

    2012-01-01

    Photo-reflectance (PR) measurements provide a non-contact means for the precise characterization of semiconductor electronic properties. In this paper, we investigate the use of a laser beam as the probe beam in the PR setup. In this case it is seen that the nonlinear refraction is responsible for the amplitude change of the reflected probe field, whereas the phase change is due to nonlinear absorption. The open aperture condition may then be used to eliminate the spatial phase at the detector, thereby isolating the electro-refractive contribution to the PR signal. This greatly simplifies the PR analysis and allows absolute measurements of electro-refraction in thin semiconductor films. We report the application of the laser PR technique to characterize physical strain in thin silicon on silicon-germanium films. - Highlights: ► We describe the theory of laser photoreflectance. ► Laser photoreflectance is used to independently characterize nonlinear refraction. ► We report the characterization of strain in thin strained silicon films.

  15. Laser bioengineering of glass-titanium implants surface

    Science.gov (United States)

    Lusquiños, F.; Arias-González, F.; Penide, J.; del Val, J.; Comesaña, R.; Quintero, F.; Riveiro, A.; Boutinguiza, M.; Pascual, M. J.; Durán, A.; Pou, J.

    2013-11-01

    Osseointegration is the mean challenge when surgical treatments fight against load-bearing bone diseases. Absolute bone replacement by a synthetic implant has to be completed not only from the mechanics point of view, but also from a biological approach. Suitable strength, resilience and stress distribution of titanium alloy implants are spoiled by the lack of optimal biological characteristics. The inert quality of extra low interstitial titanium alloy, which make it the most attractive metallic alloy for biomedical applications, oppose to an ideal surface with bone cell affinity, and capable to stimulate bone attachment bone growth. Diverse laser treatments have been proven as effective tools to modify surface properties, such as wettability in contact to physiological fluids, or osteoblast guided and slightly enhanced attachment. The laser surface cladding can go beyond by providing titanium alloy surfaces with osteoconduction and osteoinduction properties. In this research work, the laser radiation is used to produce bioactive glass coatings on Ti6Al4V alloy substrates. Specific silicate bioactive glass compositions has been investigated to achieve suitable surface tension and viscosity temperature behavior during processing, and to provide with the required release of bone growth gene up regulation agents in the course of resorption mediated by physiological fluids. The produced coatings and interfaces, the surface osteoconduction properties, and the chemical species release in simulated physiological fluid were characterized by scanning electron microscopy (SEM), hot stage microscopy (HSM), X-ray diffraction (XRD), X ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR).

  16. Frictional Performance Assessment of Cemented Carbide Surfaces Textured by Laser

    Science.gov (United States)

    Fang, S.; Llanes, L.; Klein, S.; Gachot, C.; Rosenkranz, A.; Bähre, D.; Mücklich, F.

    2017-10-01

    Cemented carbides are advanced engineering materials often used in industry for manufacturing cutting tools or supporting parts in tribological system. In order to improve service life, special attention has been paid to change surface conditions by means of different methods, since surface modification can be beneficial to reduce the friction between the contact surfaces as well as to avoid unintended damage. Laser surface texturing is one of the newly developed surface modification methods. It has been successfully introduced to fabricate some basic patterns on cemented carbide surfaces. In this work, Direct Laser Interference Patterning Technique (DLIP) is implemented to produce special line-like patterns on a cobalt (Co) and nickel (Ni) based cemented tungsten carbide grade. It is proven that the laser-produced patterns have high geometrical precision and quality stability. Furthermore, tribology testing using a nano-tribometer unit shows that friction is reduced by the line-like patterns, as compared to the polished one, under both lubricated and dry testing regimes, and the reduction is more pronounced in the latter case.

  17. Laser Surface Treatment and Modification of Aluminum Alloy Matrix Composites

    Science.gov (United States)

    Abbass, Muna Khethier

    2018-02-01

    The present work aimed to study the laser surface treatment and modification of Al-4.0%Cu-1.0%Mg alloy matrix composite reinforced with 10%SiC particles produced by stir casting. The specimens of the base alloy and composite were irradiated with an Nd:YAG laser of 1000 mJ, 1064 nm and 3 Hz . Dry wear test using the pin-on -disc technique at different sliding times (5-30 min) at a constant applied load and sliding speed were performed before and after laser treatment. Micro hardness and wear resistance were increased for all samples after laser hardening treatment. The improvement of these properties is explained by microstructural homogenization and grain refinement of the laser treated surface. Modification and refinement of SiC particles and grain refinement in the microstructure of the aluminum alloy matrix (α-Al) were observed by optical and SEM micrographs. The highest increase in hardness was 21.4% and 26.2% for the base alloy and composite sample respectively.

  18. Desensitization of stainless steels by laser surface heat-treatment

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, Yoshikuni; Nishimoto, Kazutoshi

    1987-11-01

    Laser heating was applied for the desensitization heat-treatment of the surface layer in the sensitized HAZ of Type 304 stainless steel. The degree of sensitization was examined by EPR technique and the 10 % oxalic acid electrolytic etch test. The CO/sub 2/ laser with maximum power of 1.5 kW was used for heat-treatment. Time-Temperature-Desensitization diagram (TTDS diagram) for sensitized Type 304 stainless steels were developed by calculation assuming the chromium diffusion control for desensitization which might occur when the chromium depleted zone was healed up due to dissolution of chromium carbide and chromium diffusion from the matrix being heated at the solution annealing temperatures. TTDS diagrams calculated agree fairly well with ones determined by corrosion tests. Laser irradiation conditions (e.g., Laser power, beam diameter and traveling velocity) required for desensitization of sensitized Type 304 stainless steels were calculated using additivity rule from the TTDS diagram calculated and theoretical thermal curve of laser heating derived from the heat conduction theory. After laser beam irradiated under an optimum condition predicted by calculation, the sensitized HAZ of Type 304 stainless steel restored complete resistance to intergranular corrosion.

  19. Detection of a Surface-Breaking Crack by Using the Surface Wave of a Laser Ultrasound

    International Nuclear Information System (INIS)

    Park, Seung-Kyu; Baik, Sung-Hoon; Jung, Hyun-Kyu; Joo, Young-Sang; Cha, Hyung-Ki; Kang, Young-June

    2006-01-01

    A laser ultrasonic system is a non-contact inspection device with a high spatial resolution and a wide-band spectrum. Also it provides absolute measurements of the moving distance and can be applied to the hard-to access locations with curved or rough surfaces like a nuclear power plant. Several laser ultrasonic techniques are applied for the detection of micro cracks in a nuclear power plant. Also, laser ultrasonic techniques are used to measure the grain size of materials and to detect cracks in railroads and aircrafts. Though the laser ultrasonic inspection system is widely applicable, it is comparatively expensive and it provides a low signal-to-noise ratio when compared to the conventional piezoelectric transducers. Many studies have been carried out to improve the system performance. One of the widely used measurement devices of a ultrasound is the Confocal Fabry-Perot Interferometer(CFPI) with a dynamic stabilizer. The dynamic stabilizer improves the stability of the CFPI by adaptively maintaining the optimum working status at the measuring time of the CFPI. In this paper, we have investigated the detection methods of the depth of a surface-breaking crack by using the surface wave of a laser ultrasound. We have fabricated a laser ultrasonic inspection system on an optical table by using a pulse laser, a CFPI with a dynamic stabilizer and a computer. The computer acquires the laser ultrasound by using a high speed A/D converter with a sampling rate of 1000 MHz. The dynamic stabilizer stabilizes the CFPI by adaptively maintaining it at an optimum status when the laser ultrasound is generated. The computer processes the ultrasonic signal in real time to extract the depth information of a surface-breaking crack. We extracted the depth information from the peak-to-valley values in the time domain and also from the center frequencies of the spectrum in the frequency domain

  20. Seismic data enhancement with Common Reflection Surface (CRS) stack method

    Energy Technology Data Exchange (ETDEWEB)

    Baykulov, M.; Brink, H.J.; Gajewski, D.; Yoon, Mi-Kyung [Hamburg Univ. (Germany). Inst. fuer Geophysik

    2008-10-23

    We present the results of partial stacking of prestack seismic reflection data based on the kinematic wavefield attributes computed during the automatic CRS stack. The resulting CRS supergathers are more regularised and have better signal to noise ratio compared to original CMP gathers. The improved data can be used in any conventional processing tool instead of the original data, providing enhanced images of better quality. The CRS supergather method is especially suited for low fold seismic reflection data. Application of the new method to synthetic and real low fold data shows a clear improvement of seismograms as well as time and depth-migrated sections. (orig.)

  1. Surface 3-D reflection seismics - implementation at the Olkiluoto site

    Energy Technology Data Exchange (ETDEWEB)

    Saksa, P.; Lehtimaeki, T.; Heikkinen, E. [Poeyry Environment Oy, Vantaa (Finland)

    2007-03-15

    Posiva Oy takes care of the final disposal of spent nuclear fuel in Finland. In year 2001 Olkiluoto was selected for the site of final disposal. Construction of the underground research facility, ONKALO, is going on at the Olkiluoto site. The aim of this work was to study the possibilities for surface 3-D seismics and to review experiences for design before field work. The physical parameters and geometric properties of the site, as well as efficient survey layout and source arrangements, were considered in this work. Reflection seismics is most used geophysical investigation method in oil exploration and earth studies in sedimentary environment. Recently method has also been applied in crystalline bedrock for ore exploration and nuclear waste disposal site investigations. The advantage of the method is high accuracy combined with large depth of investigation. The principles of seismic 2-D and 3-D soundings are well known and advanced. 3-D sounding is a straightforward expansion of 2-D line based surveying. In investigation of crystalline bedrock, the high frequency wave sources and receivers, their right use in measurements and careful processing procedure (refraction static corrections in particular) are important. Using the site parameters in 2-D numerical modeling, two cases of faulted thin layer at depths of 200, 400 and 600 meters were studied. The first case was a layer with vertical dislocation (a ramp) and the other a layer having limited width of dislocated part. Central frequencies were 100, 200, 400 and 700 Hz. Results indicate that 10 - 20 m dislocation is recognizable, but for depths greater than 600 m, over 20 meters is required. Width of the dislocated part will affect the detectability of vertical displacement. At depths of 200 m and 400 m 10 - 50 m wide parts appear as point-like scatterers, wider areas have more continuity. Dislocations larger than 20 m can be seen. From depth of 600 m over 100 m wide parts are discernible, narrower are visible

  2. Surface 3-D reflection seismics - implementation at the Olkiluoto site

    International Nuclear Information System (INIS)

    Saksa, P.; Lehtimaeki, T.; Heikkinen, E.

    2007-03-01

    Posiva Oy takes care of the final disposal of spent nuclear fuel in Finland. In year 2001 Olkiluoto was selected for the site of final disposal. Construction of the underground research facility, ONKALO, is going on at the Olkiluoto site. The aim of this work was to study the possibilities for surface 3-D seismics and to review experiences for design before field work. The physical parameters and geometric properties of the site, as well as efficient survey layout and source arrangements, were considered in this work. Reflection seismics is most used geophysical investigation method in oil exploration and earth studies in sedimentary environment. Recently method has also been applied in crystalline bedrock for ore exploration and nuclear waste disposal site investigations. The advantage of the method is high accuracy combined with large depth of investigation. The principles of seismic 2-D and 3-D soundings are well known and advanced. 3-D sounding is a straightforward expansion of 2-D line based surveying. In investigation of crystalline bedrock, the high frequency wave sources and receivers, their right use in measurements and careful processing procedure (refraction static corrections in particular) are important. Using the site parameters in 2-D numerical modeling, two cases of faulted thin layer at depths of 200, 400 and 600 meters were studied. The first case was a layer with vertical dislocation (a ramp) and the other a layer having limited width of dislocated part. Central frequencies were 100, 200, 400 and 700 Hz. Results indicate that 10 - 20 m dislocation is recognizable, but for depths greater than 600 m, over 20 meters is required. Width of the dislocated part will affect the detectability of vertical displacement. At depths of 200 m and 400 m 10 - 50 m wide parts appear as point-like scatterers, wider areas have more continuity. Dislocations larger than 20 m can be seen. From depth of 600 m over 100 m wide parts are discernible, narrower are visible

  3. Reflectance of Antarctic surfaces from multispectral radiometers: The correction of atmospheric effects

    International Nuclear Information System (INIS)

    Zibordi, G.; Maracci, G.

    1993-01-01

    Monitoring reflectance of polar icecaps has relevance in climate studies. In fact, climate changes produce variations in the morphology of ice and snow covers, which are detectable as surface reflectance change. Surface reflectance can be retrieved from remotely sensed data. However, absolute values independent of atmospheric turbidity and surface altitude can only be obtained after removing masking effects of the atmosphere. An atmospheric correction model, accounting for surface and sensor altitudes above sea level, is described and validated through data detected over Antarctic surfaces with a Barnes Modular Multispectral Radiometer having bands overlapping those of the Landsat Thematic Mapper. The model is also applied in a sensitivity analysis to investigate error induced in reflectance obtained from satellite data by indeterminacy in optical parameters of atmospheric constituents. Results show that indeterminacy in the atmospheric water vapor optical thickness is the main source of nonaccuracy in the retrieval of surface reflectance from data remotely sensed over Antarctic regions

  4. Quantum reflection of fast atoms from insulator surfaces: Eikonal description

    Energy Technology Data Exchange (ETDEWEB)

    Gravielle, M S; Miraglia, J E, E-mail: msilvia@iafe.uba.a, E-mail: miraglia@iafe.uba.a [Instituto de Astronomia y Fisica del Espacio, CONICET, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina) and Dpto. de Fisica, FCEN, Universidad de Buenos Aires (Argentina)

    2009-11-01

    Interference effects recently observed in grazing scattering of swift atoms from insulator surfaces are studied within a distorted-wave method - the surface eikonal approximation. This approach makes use of the eikonal wave function, involving axial channeled trajectories. The theory is applied to helium atoms colliding with a LiF(001) surface along low-index crystallographic directions. The roles played by the projectile polarization and the surface rumpling are investigated, finding that both effects are important for the description of the experimental projectile distributions.

  5. SURFACE MODIFICATIONS WITH LASER SYNTHESIZED Mo MODIFIED COATING

    OpenAIRE

    LU SUN; HAO CHEN; BO LIU

    2013-01-01

    Mg–Cu–Al was first used to improve the surface performance of TA15 titanium alloys by means of laser cladding technique. The synthesis of hard composite coating on TA15 titanium alloy by laser cladding of Mg–Cu–Al–B4C/Mo pre-placed powders was investigated by means of scanning electron microscope, energy dispersive spectrometer and high resolution transmission electron microscope. Experimental results indicated that such composite coating mainly consisted of TiB2, TiB, TiC, Ti3Al and AlCuMg. ...

  6. Remote Laser Cutting of CFRP: Improvements in the Cut Surface

    Science.gov (United States)

    Stock, Johannes; Zaeh, Michael F.; Conrad, Markus

    In the automotive industry carbon fibre reinforced plastics (CFRP) are considered as a future key material to reduce the weight of the vehicle. Therefore, capable production techniques are required to process this material in mass industry. E.g., state of the art methods for cutting are limited by the high tool wear or the feasible feed rate. Laser cutting processes are still under investigation. This paper presents detailed new studies on remote laser cutting of CFRP focusing on the influence of the material properties and the quality of the cut surface. By adding light absorbing soot particles to the resin of the matrix, the cutting process is improved and fewer defects emerge.

  7. Chromium surface alloying of structural steels during laser treatment

    International Nuclear Information System (INIS)

    Kurov, I.E.; Nagornykh, S.N.; Sivukhin, G.A.; Solenov, S.V.

    1987-01-01

    Results of matrix alloying from the surface layer and creation of considerably increased chromium concentration in the depth which permits to increase the efficiency of laser treatment of steels (12Kh18N10T and 38KhN3M) in the process of their further mechanical polishing, are presented. The treatment was realized by continuous CO 2 -laser at different power densities and scanning rates are presented. A model describing the creation of anomalous distributions of the alloying element in steels is plotted

  8. Laser surface texturing of polymers for biomedical applications

    Science.gov (United States)

    Riveiro, Antonio; Maçon, Anthony L. B.; del Val, Jesus; Comesaña, Rafael; Pou, Juan

    2018-02-01

    Polymers are materials widely used in biomedical science because of their biocompatibility, and good mechanical properties (which, in some cases, are similar to those of human tissues); however, these materials are, in general, chemically and biologically inert. Surface characteristics, such as topography (at the macro-, micro, and nanoscale), surface chemistry, surface energy, charge or wettability are interrelated properties, and they cooperatively influence the biological performance of materials when used for biomedical applications. They regulate the biological response at the implant/tissue interface (e.g., influencing the cell adhesion, cell orientation, cell motility, etc.). Several surface processing techniques have been explored to modulate these properties for biomedical applications. Despite their potentials, these methods have limitations that prevent their applicability. In this regard, laser-based methods, in particular laser surface texturing (LST), can be an interesting alternative. Different works have showed the potentiality of this technique to control the surface properties of biomedical polymers and enhance their biological performance; however, more research is needed to obtain the desired biological response. This work provides a general overview of the basics and applications of LST for the surface modification of polymers currently used in the clinical practice (e.g. PEEK, UHMWPE, PP, etc.). The modification of roughness, wettability, and their impact on the biological response is addressed to offer new insights on the surface modification of biomedical polymers.

  9. Wettability transition of laser textured brass surfaces inside different mediums

    Science.gov (United States)

    Yan, Huangping; Abdul Rashid, Mohamed Raiz B.; Khew, Si Ying; Li, Fengping; Hong, Minghui

    2018-01-01

    Hydrophobic surface on brass has attracted intensive attention owing to its importance in scientific research and practical applications. Laser texturing provides a simple and promising method to achieve it. Reducing wettability transition time from hydrophilicity to hydrophobicity or superhydrophobicity remains a challenge. Herein, wettability transition of brass surfaces with hybrid micro/nano-structures fabricated by laser texturing was investigated by immersing the samples inside different mediums. Scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy and surface contact angle measurement were employed to characterize surface morphology, chemical composition and wettability of the fabricated surfaces of brass samples. Wettability transition time from hydrophilicity to hydrophobicity was shortened by immersion into isopropyl alcohol for a period of 3 h as a result of the absorption and accumulation of organic substances on the textured brass surface. When the textured brass sample was immersed into sodium bicarbonate solution, flower-like structures on the sample surface played a key role in slowing down wettability transition. Moreover, it had the smallest steady state contact angle as compared to the others. This study provides a facile method to construct textured surfaces with tunable wetting behaviors and effectively extend the industrial applications of brass.

  10. Modeling of circular-grating surface-emitting lasers

    Science.gov (United States)

    Shams-Zadeh-Amiri, Ali M.

    Grating-coupled surface-emitting lasers became an area of growing interest due to their salient features. Emission from a broad area normal to the wafer surface, makes them very well suited in high power applications and two- dimensional laser arrays. These new possibilities have caused an interest in different geometries to fully develop their potential. Among them, circular-grating lasers have the additional advantage of producing a narrow beam with a circular cross section. This special feature makes them ideal for coupling to optical fibers. All existing theoretical models dealing with circular- grating lasers only consider first-order gratings, or second-order gratings, neglecting surface emission. In this thesis, the emphasis is to develop accurate models describing the laser performance by considering the radiation field. Toward this aim, and due to the importance of the radiation modes in surface-emitting structures, a theoretical study of these modes in multilayer planar structures has been done in a rigorous and systematic fashion. Problems like orthogonality of the radiation modes have been treated very accurately. We have considered the inner product of radiation modes using the distribution theory. Orthogonality of degenerate radiation modes is an important issue. We have examined its validity using the transfer matrix method. It has been shown that orthogonality of degenerate radiation modes in a very special case leads to the Brewster theorem. In addition, simple analytical formulas for the normalization of radiation modes have been derived. We have shown that radiation modes can be handled in a much easier way than has been thought before. A closed-form spectral dyadic Green's function formulation of multilayer planar structures has been developed. In this formulation, both rectangular and cylindrical structures can be treated within the same mathematical framework. The Hankel transform of some auxiliary functions defined on a circular aperture has

  11. Electron backscatter diffraction characterization of laser-induced periodic surface structures on nickel surface

    Energy Technology Data Exchange (ETDEWEB)

    Sedao, Xxx, E-mail: sedao.xxx@gmail.com [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France); Maurice, Claire [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 St-Etienne (France); Garrelie, Florence; Colombier, Jean-Philippe; Reynaud, Stéphanie [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France); Quey, Romain; Blanc, Gilles [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 St-Etienne (France); Pigeon, Florent [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France)

    2014-05-01

    Graphical abstract: -- Highlight: •Lattice rotation and its distribution in laser-induced periodic surface structures (LIPSS) and the subsurface region on a nickel substrate are revealed using electron backscatter diffraction (EBSD). -- Abstract: We report on the structural investigation of laser-induced periodic surface structures (LIPSS) generated in polycrystalline nickel target after multi-shot irradiation by femtosecond laser pulses. Electron backscatter diffraction (EBSD) is used to reveal lattice rotation caused by dislocation storage during LIPSS formation. Localized crystallographic damages in the LIPSS are detected from both surface and cross-sectional EBSD studies. A surface region (up to 200 nm) with 1–3° grain disorientation is observed in localized areas from the cross-section of the LIPSS. The distribution of the local disorientation is inhomogeneous across the LIPSS and the subsurface region.

  12. Investigation of Tree Spectral Reflectance Characteristics Using a Mobile Terrestrial Line Spectrometer and Laser Scanner

    Directory of Open Access Journals (Sweden)

    Eetu Puttonen

    2013-07-01

    Full Text Available In mobile terrestrial hyperspectral imaging, individual trees often present large variations in spectral reflectance that may impact the relevant applications, but the related studies have been seldom reported. To fill this gap, this study was dedicated to investigating the spectral reflectance characteristics of individual trees with a Sensei mobile mapping system, which comprises a Specim line spectrometer and an Ibeo Lux laser scanner. The addition of the latter unit facilitates recording the structural characteristics of the target trees synchronously, and this is beneficial for revealing the characteristics of the spatial distributions of tree spectral reflectance with variations at different levels. Then, the parts of trees with relatively low-level variations can be extracted. At the same time, since it is difficult to manipulate the whole spectrum, the traditional concept of vegetation indices (VI based on some particular spectral bands was taken into account here. Whether the assumed VIs capable of behaving consistently for the whole crown of each tree was also checked. The specific analyses were deployed based on four deciduous tree species and six kinds of VIs. The test showed that with the help of the laser scanner data, the parts of individual trees with relatively low-level variations can be located. Based on these parts, the relatively stable spectral reflectance characteristics for different tree species can be learnt.

  13. Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

    International Nuclear Information System (INIS)

    Pan, A.; Dias, A.; Gomez-Aranzadi, M.; Olaizola, S. M.; Rodriguez, A.

    2014-01-01

    The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced

  14. Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pan, A.; Dias, A.; Gomez-Aranzadi, M.; Olaizola, S. M. [CIC microGUNE, Goiru Kalea 9 Polo Innovación Garaia, 20500 Arrasate-Mondragón (Spain); CEIT-IK4 and Tecnun, University of Navarra, Manuel Lardizábal 15, 20018 San Sebastián (Spain); Rodriguez, A. [CIC microGUNE, Goiru Kalea 9 Polo Innovación Garaia, 20500 Arrasate-Mondragón (Spain)

    2014-05-07

    The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.

  15. Surface characterization of weathered wood using a laser scanning system

    International Nuclear Information System (INIS)

    Arnold, M.; Lemaster, R.L.; Dost, W.A.

    1992-01-01

    Most of the existing methods to assess the effect of weathering on wood surfaces have some drawbacks that limit their use to specific tasks. The amount of surface erosion is often used as a measure for the weathering action. The application of a laser scanning system to reproduce surface profiles and to measure weathering erosion was tested on various samples and was found to be a very useful and superior alternative to existing methods. Further improvements of the system used can be made by refinements of the calibration procedures and by more comprehensive profile analyses. (author)

  16. Facial recognition and laser surface scan: a pilot study

    DEFF Research Database (Denmark)

    Lynnerup, Niels; Clausen, Maja-Lisa; Kristoffersen, Agnethe May

    2009-01-01

    Surface scanning of the face of a suspect is presented as a way to better match the facial features with those of a perpetrator from CCTV footage. We performed a simple pilot study where we obtained facial surface scans of volunteers and then in blind trials tried to match these scans with 2D...... photographs of the faces of the volunteers. Fifteen male volunteers were surface scanned using a Polhemus FastSCAN Cobra Handheld Laser Scanner. Three photographs were taken of each volunteer's face in full frontal, profile and from above at an angle of 45 degrees and also 45 degrees laterally. Via special...

  17. Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Gregory Elijah [The Ohio State Univ., Columbus, OH (United States)

    2013-01-01

    Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic

  18. Interference effects in plasom excitation by particles reflected near a metal surface

    International Nuclear Information System (INIS)

    Denton, C.D.; Gervasoni, J.L.; Barrachina, R.O.; Arista, N.R.; Universidad Nacional de Cuyo, Mendoza

    1993-01-01

    Using the dielectric formalism and the specular reflection model, we evaluate the probability of surface and bulk plasmon excitation by particles reflected in the proximity of a metal surface. We obtain a strong oscillatory behaviour as a function of the penetration distance. (author)

  19. On the surface topography of ultrashort laser pulse treated steel surfaces

    International Nuclear Information System (INIS)

    Vincenc Obona, J.; Ocelík, V.; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in’t Veld, A.J.; De Hosson, J.Th.M.

    2011-01-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the fluence applied. It is shown that these features appear due to solid-liquid and liquid-gas transitions within surface layer irradiated by intense laser light. The observations are confronted to the theory of short-pulsed laser light-matter interactions, including interference, excitation of electrons, electron-phonon coupling as well as subsequent ablation. It is shown that the orientation of small ripples does not always depend on the direction of the polarization of laser light.

  20. Laser surface modification of boronickelized medium carbon steel

    Science.gov (United States)

    Bartkowska, Aneta; Pertek, Aleksandra; Kulka, Michał; Klimek, Leszek

    2015-11-01

    A two-step process was applied to produce the multicomponent boride layers. Boronickelizing consisted of nickel plating and diffusion boriding. Two different methods of heat treatment of boronickelized C45 steel were used: a typical through-hardening, and a laser surface modification with remelting. Microstructure and some mechanical properties of these layers were examined. Microstructural characterization was studied using optical microscope, Scanning Electron Microscope, energy-dispersive X-ray microanalysis, Electron Back-Scatter Diffraction and X-ray diffraction. The laser modification improved wear resistance, cohesion as well as low-cycle fatigue of the boronickelized layer. Compressive stresses, occurring after laser remelting, could be the reason for the advantageous mechanical behavior of the layer.

  1. A Monte Carlo reflectance model for soil surfaces with three-dimensional structure

    Science.gov (United States)

    Cooper, K. D.; Smith, J. A.

    1985-01-01

    A Monte Carlo soil reflectance model has been developed to study the effect of macroscopic surface irregularities larger than the wavelength of incident flux. The model treats incoherent multiple scattering from Lambertian facets distributed on a periodic surface. Resulting bidirectional reflectance distribution functions are non-Lambertian and compare well with experimental trends reported in the literature. Examples showing the coupling of the Monte Carlo soil model to an adding bidirectional canopy of reflectance model are also given.

  2. Influence of surface roughness on the reflective properties of snow

    International Nuclear Information System (INIS)

    Zhuravleva, Tatiana B.; Kokhanovsky, Alexander A.

    2011-01-01

    In this paper the influence of 3D effect on snow reflection function (SRF) and albedo is studied in the framework of the stochastic radiative transfer theory. In particular, the corresponding equations for the averaged intensity of reflected light are solved for the ensemble of realizations of the stochastic field κ(r), describing the distribution of 3D elements on the flat semi-infinite snow layer (SISL). The reflection from the underlying SISL is modeled using the solution of the 1D radiative transfer equation. The corresponding look-up tables were compiled beforehand and used in the simulation process. In accordance with the previous studies, it was found that the albedo of snow layer is reduced (in particular, in the infrared region), if 3D effects are taken into account. There is no such a reduction, if light absorption in snow is absent. The 3D effects may increase or decrease SRF depending on the sastrugi fraction and illumination/observation conditions.

  3. Serial number coding and decoding by laser interference direct patterning on the original product surface for anti-counterfeiting.

    Science.gov (United States)

    Park, In-Yong; Ahn, Sanghoon; Kim, Youngduk; Bae, Han-Sung; Kang, Hee-Shin; Yoo, Jason; Noh, Jiwhan

    2017-06-26

    Here, we investigate a method to distinguish the counterfeits by patterning multiple reflective type grating directly on the surface of the original product and analyze the serial number from its rotation angles of diffracted fringes. The micro-sized gratings were fabricated on the surface of the material at high speeds by illuminating the interference fringe generated by passing a high-energy pulse laser through the Fresnel biprism. In addition, analysis of the grating's diffraction fringes was performed using a continuous wave laser.

  4. Reflectivity reduction of retro-reflector installed in LHD due to plasma surface interaction

    International Nuclear Information System (INIS)

    Yoshida, N.; Ohtawa, Y.; Ebihara, A.; Akiyama, T.; Tokitani, M.; Ashikawa, N.; Kawahata, K.

    2008-10-01

    Optical reflectivity of the retro-reflector installed in LHD as the first mirror was reduced seriously by plasma wall interaction. In order to understand the mechanism of the reflectivity reduction, optical and material properties of the mirror surfaces have been examined extensively. It was found that the deposited impurity layers caused the serious reduction of the reflectivity. Formation of iron oxide, bulges structure and He bubbles are the major factors for the reflectivity reduction in the wide wave length range. (author)

  5. Modern reflective optics for material processing with high power CO/sub 2/-laser beams

    International Nuclear Information System (INIS)

    Juptner, W.P.O.; Sepold, G.; Rothe, R.R.

    1986-01-01

    The state of the art in diamond turning of parabolic mirrors allows to manufacture high quality surfaces at a reasonable low price. In this paper a report is given on mirror optics and systems which were developed with the following aims: Small losses of laser power in the system with a high efficiency of the laser beam processing system; Long lifetime of the mirrors under material processing conditions; High Standard of the optical quality; Flexibility for different applications. The requested qualities are guaranteed by the whole construction of the optics and the system. The theoretical works, the state of the art of the development and the future aspects of these laser working head systems are reported

  6. Optimized laser system for decontamination of painted surfaces

    International Nuclear Information System (INIS)

    Champonnois, F.; Lascoutouna, C.; Long, H.; Thro, P.Y.; Mauchien, P.

    2010-01-01

    Laser systems have long been seen as potentially very interesting for removing contamination from surfaces. The main expected advantages are the possibility of remote process and the absence of secondary waste. However these systems were unable to find their way to an industrial deployment due to the lack of reliability of the laser and the difficulty to satisfactory collect the (contaminated) ablated matter. In this contribution we report on a compact, reliable and efficient laser decontaminating system called ASPILASERO. It is adapted to the constraints bound to a nuclear environment. It takes advantages of the recent progress made by the fibre lasers which have now a lifetime longer than 20000 hours without maintenance. The collecting system collects all the removed matter (gases and aerosols) on nuclear grade filters. The fully automated system has been successfully tested on a vertical wall of a stopped nuclear installation. It has demonstrated an efficiency of 1 m 2 /hr which is in the same order of other classical techniques but with a much lower quantity of waste and the ability to work continuously without human intervention. Measurements performed after the laser treatment have shown that the contamination was completely removed by removing the paint and that this contamination was not re-deposited elsewhere on the wall. The system will also be used in highly contaminated hot cells to decrease the radiation and allow maintenance or refurbishing in safe working conditions. (authors)

  7. NUMERICAL SIMULATION OF Q-SWITCHED Nd: YAG LASER WITH UNSTABLE RESONATOR AND OUTPUT VARIABLE REFLECTIVITY MIRROR

    Directory of Open Access Journals (Sweden)

    I. N. Dubinkin

    2017-05-01

    Full Text Available The article deals with a method of numerical simulation of laser oscillation in the radially symmetric unstable resonator with an output variable reflectivity mirror (VRM. Research results of the VRM parameters influence on the spatial and energy properties of the laser radiation are obtained. Numerical simulation of laser oscillation in active and passive Q-switching and comparative analysis of the spatial and energy radiation characteristics is done for these modes.

  8. Two dimensional simulation of high power laser-surface interaction

    International Nuclear Information System (INIS)

    Goldman, S.R.; Wilke, M.D.; Green, R.E.L.; Johnson, R.P.; Busch, G.E.

    1998-01-01

    For laser intensities in the range of 10 8 --10 9 W/cm 2 , and pulse lengths of order 10 microsec or longer, the authors have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of their treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. The authors will present an analysis of some relatively well diagnosed experiments which have been useful in developing their modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence their simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range. This work is useful in many technical areas such as materials processing

  9. Laser method of acoustical emission control from vibrating surfaces

    Science.gov (United States)

    Motyka, Zbigniew

    2013-01-01

    For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.

  10. Improvement of the surface finish obtained by laser ablation with a Nd: YAG laser on pre-ablated tool steel

    CSIR Research Space (South Africa)

    Steyn, J

    2007-01-01

    Full Text Available . In recent years, these lasers have been used in other fields, such as laser ablation of small tools for plastics injection moulding. Laser ablation is a technology that is investigated as a method to improve the surface finish in tool steel. Different...

  11. Research on Laser Micro Polishing of SLS Technology Sintered Iron-Based Powder Surface

    OpenAIRE

    Gerda Vaitkūnaitė; Vladislav Markovič; Olegas Černašėjus

    2015-01-01

    The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS) method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treat...

  12. Preparation of surface conductive and highly reflective silvered polyimide films by surface modification and in situ self-metallization technique

    International Nuclear Information System (INIS)

    Wu Zhanpeng; Wu Dezhen; Qi Shengli; Zhang Teng; Jin Riguang

    2005-01-01

    Double surface conductive and reflective flexible silvered polyimide films have been prepared by alkali hydroxylation of polyimide film surface and incorporation of silver ions through subsequent ion exchange. Thermal curing of silver(I) polyamate precursor leads to re-cycloimidization of modified surface with concomitant silver reduction, yielding a reflective and conductive silver surface approaching that of native metal. The reflective and conductive surface evolves only when the cure temperature rises to 300 deg. C. The metallized films usually retain the essential mechanical properties of the parent films. Films were characterized by transmission electron microscopy (TEM), scanning electron microscopy and tapping mode atomic force microscopy (AFM). AFM demonstrates that the diameter of close-packed silver particles of the silver layers was about 50-150 nm. TEM shows that thickness of silver layer on the polyimide film surface is about 400-600 nm

  13. High quality broadband spatial reflections of slow Rayleigh surface acoustic waves modulated by a graded grooved surface

    KAUST Repository

    Xu, Yanlong

    2015-01-21

    We report high quality broadband spatial reflections of Rayleigh surface acoustic waves (SAWs) through a graded grooved surface. High quality means that no wave is allowed to transmit and the incident wave is nearly all reflected to the input side. The graded grooved surface is structured by drilling one dimensional array of graded grooves with increased depths on a flat surface. We investigate SAW dispersion relations, wave field distribution at several typical SAW wavelengths, and time evolution of a Gaussian pulse through the graded grooved surface. Results show that the input broadband Rayleigh SAWs can be slowed, spatially enhanced and stopped, and finally reflected to the input side. The study suggests that engraving the flat surface can be used as an efficient and economical way to manipulate Rayleigh SAWs, which has potential application in novel SAW devices such as filters, reflectors, sensors, energy harvesters, and diodes.

  14. Surface Thermometry of Energetic Materials by Laser-Induced Fluorescence

    Science.gov (United States)

    1989-09-01

    at 34 yttrium- aluminum -garnet (Dy:YAG). The simplified energy diagram of Dy:YAG is shown in Fig. 1. Absorbed laser light (at 355 nrm) can 5 excite the...the thermometric technique on a surface similar to that of an energetic material, a thermal-setting plastic supplied by Buehler, Ltd., was employed...temperature over the temperature range of interest. The rare-earth ion dysprosium (Dy) doped into a yttrium- aluminum -garnet (YAG) crystal was I determined

  15. High Power Tm3+-Doped Fiber Lasers Tuned by a Variable Reflective Output Coupler

    Directory of Open Access Journals (Sweden)

    Yulong Tang

    2008-01-01

    Full Text Available Wide wavelength tuning by a variable reflective output coupler is demonstrated in high-power double-clad Tm3+-doped silica fiber lasers diode-pumped at ∼790  nm. Varying the output coupling from 96% to 5%, the laser wavelength is tuned over a range of 106  nm from 1949 to 2055  nm. The output power exceeds 20  W over 90-nm range and the maximum output power is 32  W at 1949  nm for 51-W launched pump power, corresponding to a slope efficiency of ∼70%. Assisted with different fiber lengths, the tuning range is expanded to 240  nm from 1866 to 2107  nm with the output power larger than 10  W.

  16. Diffuse reflectance imaging for non-melanoma skin cancer detection using laser feedback interferometry

    Science.gov (United States)

    Mowla, Alireza; Taimre, Thomas; Lim, Yah L.; Bertling, Karl; Wilson, Stephen J.; Prow, Tarl W.; Soyer, H. P.; Rakić, Aleksandar D.

    2016-04-01

    We propose a compact, self-aligned, low-cost, and versatile infrared diffuse-reflectance laser imaging system using a laser feedback interferometry technique with possible applications in in vivo biological tissue imaging and skin cancer detection. We examine the proposed technique experimentally using a three-layer agar skin phantom. A cylindrical region with a scattering rate lower than that of the surrounding normal tissue was used as a model for a non-melanoma skin tumour. The same structure was implemented in a Monte Carlo computational model. The experimental results agree well with the Monte Carlo simulations validating the theoretical basis of the technique. Results prove the applicability of the proposed technique for biological tissue imaging, with the capability of depth sectioning and a penetration depth of well over 1.2 mm into the skin phantom.

  17. Temporal analysis of reflected optical signals for short pulse laser interaction with nonhomogeneous tissue phantoms

    International Nuclear Information System (INIS)

    Trivedi, Ashish; Basu, Soumyadipta; Mitra, Kunal

    2005-01-01

    The use of short pulse laser for minimally invasive detection scheme has become an indispensable tool in the technological arsenal of modern medicine and biomedical engineering. In this work, a time-resolved technique has been used to detect tumors/inhomogeneities in tissues by measuring transmitted and reflected scattered temporal optical signals when a short pulse laser source is incident on tissue phantoms. A parametric study involving different scattering and absorption coefficients of tissue phantoms and inhomogeneities, size of inhomogeneity as well as the detector position is performed. The experimental measurements are validated with a numerical solution of the transient radiative transport equation obtained by using discrete ordinates method. Thus, both simultaneous experimental and numerical studies are critical for predicting the optical properties of tissues and inhomogeneities from temporal scattered optical signal measurements

  18. Retrieving background surface reflectance of Himawari-8/AHI using BRDF modeling

    Science.gov (United States)

    Choi, Sungwon; Seo, Minji; Lee, Kyeong-sang; Han, Kyung-soo

    2017-04-01

    In these days, remote sensing is more important than past. And retrieving surface reflectance in remote sensing is also important. So there are many ways to retrieve surface reflectance by my countries with polar orbit and geostationary satellite. We studied Bidirectional Reflectance Distribution Function (BRDF) which is used to retrieve surface reflectance. In BRDF equation, we calculate surface reflectance using BRD components and angular data. BRD components are to calculate 3 of scatterings, isotropic geometric and volumetric scattering. To make Background Surface Reflectance (BSR) of Himawari-8/AHI. We used 5 bands (band1, band2, band3, band4, band5) with BRDF. And we made 5 BSR for 5 channels. For validation, we compare BSR with Top of canopy (TOC) reflectance of AHI. As a result, bias are from -0.00223 to 0.008328 and Root Mean Square Error (RMSE) are from 0.045 to 0.049. We think BSR can be used to replace TOC reflectance in remote sensing to improve weakness of TOC reflectance.

  19. Laser Sensing of Vegetation Based on Dual Spectrum Measurements of Reflection Coefficients

    Directory of Open Access Journals (Sweden)

    M. L. Belov

    2017-01-01

    Full Text Available Currently, a promising trend in remote sensing of environment is to monitor the vegetative cover: evaluate the productivity of agricultural crops; evaluate the moisture content of soils and the state of ecosystems; provide mapping the sites of bogging, desertification, drought, etc.; control the phases of vegetation of crops, etc.Development of monitoring systems for remote detection of vegetation sites being under unfavorable conditions (low or high temperature, excess or lack of water, soil salinity, disease, etc. is of relevance. Optical methods are the most effective for this task. These methods are based on the physical features of reflection spectra in the visible and near infrared spectral range for vegetation under unfavorable conditions and vegetation under normal conditions.One of the options of optoelectronic equipment for monitoring vegetation condition is laser equipment that allows remote sensing of vegetation from the aircraft and mapping of vegetation sites with abnormal (inactive periods of vegetation reflection spectra with a high degree of spatial resolution.The paper deals with development of a promising dual-spectrum method for laser remote sensing of vegetation. Using the experimentally measured reflection spectra of different vegetation types, mathematical modeling of probability for appropriate detection and false alarms to solve a problem of detecting the vegetation under unfavorable conditions (with abnormal reflection spectra is performed based on the results of dual-spectrum measurements of the reflection coefficient.In mathematical modeling, the lidar system was supposed to provide sensing at wavelengths of 0.532 μm and 0.85 μm. The noise of the measurement was supposed to be normal with zero mean value and mean-square value of 1% -10%.It is shown that the method of laser sensing of vegetation condition based on the results of dual-spectrum measurement of the reflection coefficient at wavelengths of 0.532 μm and 0

  20. Laser AMS 14C dating of rock surface accretions

    International Nuclear Information System (INIS)

    Watchman, A.; Campbell, F.

    1997-01-01

    Full text: Equipment has been purchased using a large Earth Sciences and Engineering ARC grant and installed in the Department of Anthropology and Archaeology, James Cook University. A krypton-ion laser used initially at Laval University, Quebec to demonstrate the potential of focusing light energy to induce oxidation of carbon-bearing substances has been replaced by a carbon dioxide laser. This decision was based on reducing the startup cost at James Cook University, increasing options for a wide range of output power, considerations for future applications and the cost of gas refills. A disadvantage of using the carbon dioxide laser is that non-visible light optics are needed because of the infrared output wavelength from the carbon dioxide. This has required the replacement of the glass window of the vacuum-tight micro-combustion chamber with a sodium chloride window and placing the equipment in a dehumidifier room. Laser light power experiments have so far been conducted on optimising the output from the laser and minimising the focal waist of the beam by adjusting the focusing mirrors and lenses. The aim of developing a focused laser system is to enable the dating of carbon in finely laminated rock surface accretions, but before this can be achieved a series of tests is planned to ensure that the focused laser system totally converts all the carbon-bearing substances under the beam into carbon dioxide. This is essential in order that the isotopic values representative of the carbon in the accretions is converted into carbon dioxide. Known quantities of graphite, charcoal, wood cellulose and calcium oxalate salts are being subjected to focused laser combustion or decomposition and the volumes of gas produced at different light powers are being measured. Isotopic measurements are also being conducted on the resulting gases to ensure that fractionation of carbon isotopes is not a problem. The paper will describe the arrangement of equipment and explain the

  1. Laser-induced plasma spectrometry: truly a surface analytical tool

    International Nuclear Information System (INIS)

    Vadillo, Jose M.; Laserna, J.

    2004-01-01

    For a long period, analytical applications of laser induced plasma spectrometry (LIPS) have been mainly restricted to overall and quantitative determination of elemental composition in bulk, solid samples. However, introduction of new compact and reliable solid state lasers and technological development in multidimensional intensified detectors have made possible the seeking of new analytical niches for LIPS where its analytical advantages (direct sampling from any material irrespective of its conductive status without sample preparation and with sensitivity adequate for many elements in different matrices) could be fully exploited. In this sense, the field of surface analysis could take advantage from the cited advantages taking into account in addition, the capability of LIPS for spot analysis, line scan, depth-profiling, area analysis and compositional mapping with a single instrument in air at atmospheric pressure. This review paper outlines the fundamental principles of laser-induced plasma emission relevant to sample surface studies, discusses the experimental parameters governing the spatial (lateral and in-depth) resolution in LIPS analysis and presents the applications concerning surface examination

  2. Fiber laser cleaning of metal mirror surfaces for optical diagnostic systems of the ITER

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, A. P., E-mail: APKuznetsov@mephi.ru; Alexandrova, A. S. [National Research Nuclear University MEPhI (Russian Federation); Buzhinsky, O. I. [State Research Center of the Russian Federation Troitsk Institute for Innovation and Fusion Research (Russian Federation); Gubskiy, K. L.; Kazieva, T. V.; Savchenkov, A. V. [National Research Nuclear University MEPhI (Russian Federation); Tugarinov, S. N. [State Research Center of the Russian Federation Troitsk Institute for Innovation and Fusion Research (Russian Federation)

    2015-12-15

    The results of experimental studies into efficiency of removal of films with a complex composition from metal mirrors by pulsed fiber laser irradiation are presented. It is shown that the initial reflectivity of optical elements can be restored by the selection of modes of irradiation impacting the surface with the sputtered film. Effective cleaning is performed by radiation with a power density lower than 10{sup 7} W/cm{sup 2}. The removal of contaminations at such a relatively low power density occurs in a solid phase, owing to which the thermal effect on the mirror is insignificant.

  3. Fiber laser cleaning of metal mirror surfaces for optical diagnostic systems of the ITER

    International Nuclear Information System (INIS)

    Kuznetsov, A. P.; Alexandrova, A. S.; Buzhinsky, O. I.; Gubskiy, K. L.; Kazieva, T. V.; Savchenkov, A. V.; Tugarinov, S. N.

    2015-01-01

    The results of experimental studies into efficiency of removal of films with a complex composition from metal mirrors by pulsed fiber laser irradiation are presented. It is shown that the initial reflectivity of optical elements can be restored by the selection of modes of irradiation impacting the surface with the sputtered film. Effective cleaning is performed by radiation with a power density lower than 10 7 W/cm 2 . The removal of contaminations at such a relatively low power density occurs in a solid phase, owing to which the thermal effect on the mirror is insignificant

  4. Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

    Science.gov (United States)

    Chizhevsky, V. N.

    2018-01-01

    For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

  5. STACKING ON COMMON REFLECTION SURFACE WITH MULTIPARAMETER TRAVELTIME

    Directory of Open Access Journals (Sweden)

    Montes V. Luis A.

    2006-12-01

    Full Text Available Commonly seismic images are displayed in time domain because the model in depth can be known only in well logs. To produce seismic sections, pre and post stack processing approaches use time or depth velocity models whereas the common reflection method does not, instead it requires a set of parameters established for the first layer. A set of synthetic data of an anticline model, with sources and receivers placed on a flat topography, was used to observe the performance of this method. As result, a better reflector recovering compared against conventional processing sequence was observed.
    The procedure was extended to real data, using a dataset acquired on a zone characterized by mild topography and quiet environment reflectors in the Eastern Colombia planes, observing an enhanced and a better continuity of the reflectors in the CRS stacked section.

  6. Microstructure and properties of cast iron after laser surface hardening

    Directory of Open Access Journals (Sweden)

    Stanislav

    2013-12-01

    Full Text Available Laser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance.

  7. Noninvasive assessment of articular cartilage surface damage using reflected polarized light microscopy

    Science.gov (United States)

    Huynh, Ruby N.; Nehmetallah, George; Raub, Christopher B.

    2017-06-01

    Articular surface damage occurs to cartilage during normal aging, osteoarthritis, and in trauma. A noninvasive assessment of cartilage microstructural alterations is useful for studies involving cartilage explants. This study evaluates polarized reflectance microscopy as a tool to assess surface damage to cartilage explants caused by mechanical scraping and enzymatic degradation. Adult bovine articular cartilage explants were scraped, incubated in collagenase, or underwent scrape and collagenase treatments. In an additional experiment, cartilage explants were subject to scrapes at graduated levels of severity. Polarized reflectance parameters were compared with India ink surface staining, features of histological sections, changes in explant wet weight and thickness, and chondrocyte viability. The polarized reflectance signal was sensitive to surface scrape damage and revealed individual scrape features consistent with India ink marks. Following surface treatments, the reflectance contrast parameter was elevated and correlated with image area fraction of India ink. After extensive scraping, polarized reflectance contrast and chondrocyte viability were lower than that from untreated explants. As part of this work, a mathematical model was developed and confirmed the trend in the reflectance signal due to changes in surface scattering and subsurface birefringence. These results demonstrate the effectiveness of polarized reflectance microscopy to sensitively assess surface microstructural alterations in articular cartilage explants.

  8. Patellar Skin Surface Temperature by Thermography Reflects Knee Osteoarthritis Severity

    OpenAIRE

    Anna E. Denoble; Norine Hall; Carl F. Pieper; Virginia B. Kraus

    2010-01-01

    Background: Digital infrared thermal imaging is a means of measuring the heat radiated from the skin surface. Our goal was to develop and assess the reproducibility of serial infrared measurements of the knee and to assess the association of knee temperature by region of interest with radiographic severity of knee Osteoarthritis (rOA). Methods: A total of 30 women (15 Cases with symptomatic knee OA and 15 age-matched Controls without knee pain or knee OA) participated in this study. Infrared ...

  9. Reflective Optical Chopper Used in NIST High-Power Laser Measurements

    Directory of Open Access Journals (Sweden)

    Cromer, Chris

    2008-11-01

    Full Text Available For the past ten years, NIST has used high-reflectivity, optical choppers as beamsplitters and attenuators when calibrating the absolute responsivity and response linearity of detectors used with high-power CW lasers. The chopper-based technique has several advantages over the use of wedge-shaped transparent materials (usually crystals often used as beam splitters in this type of measurement system. We describe the design, operation and calibration of these choppers. A comparison between choppers and transparent wedge beampslitters is also discussed.

  10. Unmanned aerial system nadir reflectance and MODIS nadir BRDF-adjusted surface reflectances intercompared over Greenland

    Directory of Open Access Journals (Sweden)

    J. F. Burkhart

    2017-07-01

    Full Text Available Albedo is a fundamental parameter in earth sciences, and many analyses utilize the Moderate Resolution Imaging Spectroradiometer (MODIS bidirectional reflectance distribution function (BRDF/albedo (MCD43 algorithms. While derivative albedo products have been evaluated over Greenland, we present a novel, direct comparison with nadir surface reflectance collected from an unmanned aerial system (UAS. The UAS was flown from Summit, Greenland, on 210 km transects coincident with the MODIS sensor overpass on board the Aqua and Terra satellites on 5 and 6 August 2010. Clear-sky acquisitions were available from the overpasses within 2 h of the UAS flights. The UAS was equipped with upward- and downward-looking spectrometers (300–920 nm with a spectral resolution of 10 nm, allowing for direct integration into the MODIS bands 1, 3, and 4. The data provide a unique opportunity to directly compare UAS nadir reflectance with the MODIS nadir BRDF-adjusted surface reflectance (NBAR products. The data show UAS measurements are slightly higher than the MODIS NBARs for all bands but agree within their stated uncertainties. Differences in variability are observed as expected due to different footprints of the platforms. The UAS data demonstrate potentially large sub-pixel variability of MODIS reflectance products and the potential to explore this variability using the UAS as a platform. It is also found that, even at the low elevations flown typically by a UAS, reflectance measurements may be influenced by haze if present at and/or below the flight altitude of the UAS. This impact could explain some differences between data from the two platforms and should be considered in any use of airborne platforms.

  11. Optical Estimation of the 3D Shape of a Solar Illuminated, Reflecting Satellite Surface

    Science.gov (United States)

    Antolin, J.; Yu, Z.; Prasad, S.

    2016-09-01

    The spatial distribution of the polarized component of the power reflected by a macroscopically smooth but microscopically roughened curved surface under highly directional illumination, as characterized by an appropriate bi-directional reflectance distribution function (BRDF), carries information about the three-dimensional (3D) shape of the surface. This information can be exploited to recover the surface shape locally under rather general conditions whenever power reflectance data for at least two different illumination or observation directions can be obtained. We present here two different parametric approaches for surface reconstruction, amounting to the recovery of the surface parameters that are either the global parameters of the family to which the surface is known a priori to belong or the coefficients of a low-order polynomial that can be employed to characterize a smoothly varying surface locally over the observed patch.

  12. Formation of silicon carbide by laser ablation in graphene oxide-N-methyl-2-pyrrolidone suspension on silicon surface

    Science.gov (United States)

    Jaleh, Babak; Ghasemi, Samaneh; Torkamany, Mohammad Javad; Salehzadeh, Sadegh; Maleki, Farahnaz

    2018-01-01

    Laser ablation of a silicon wafer in graphene oxide-N-methyl-2-pyrrolidone (GO-NMP) suspension was carried out with a pulsed Nd:YAG laser (pulse duration = 250 ns, wavelength = 1064 nm). The surface of silicon wafer before and after laser ablation was studied using optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results showed that the ablation of silicon surface in liquid by pulsed laser was done by the process of melt expulsion under the influence of the confined plasma-induced pressure or shock wave trapped between the silicon wafer and the liquid. The X-ray diffraction‌ (XRD) pattern of Si wafer after laser ablation showed that 4H-SiC layer is formed on its surface. The formation of the above layer was also confirmed by Raman spectroscopy, and X-ray photoelectron spectroscopy‌ (XPS), as well as EDX was utilized. The reflectance of samples decreased with increasing pulse energy. Therefore, the morphological alteration and the formation of SiC layer at high energy increase absorption intensity in the UV‌-vis regions. Theoretical calculations confirm that the formation of silicon carbide from graphene oxide and silicon wafer is considerably endothermic. Development of new methods for increasing the reflectance without causing harmful effects is still an important issue for crystalline Si solar cells. By using the method described in this paper, the optical properties of solar cells can be improved.

  13. Measuring spatial and temporal variation in surface moisture on a coastal beach with a near-infrared terrestrial laser scanner

    Science.gov (United States)

    Smit, Yvonne; Ruessink, Gerben; Brakenhoff, Laura B.; Donker, Jasper J. A.

    2018-04-01

    Wind-alone predictions of aeolian sand deposition on the most seaward coastal dune ridge often exceed measured deposition substantially. Surface moisture is a major factor limiting aeolian transport on sandy beaches, but existing measurement techniques cannot adequately characterize the spatial and temporal distribution of surface moisture content. Here, we present a new method for detecting surface moisture at high temporal and spatial resolution using a near-infrared terrestrial laser scanner (TLS), the RIEGL VZ-400. Because this TLS operates at a wavelength (1550 nm) near a water absorption band, TLS reflectance is an accurate parameter to measure surface moisture over its full range. Five days of intensive laser scanning were performed on a Dutch beach to illustrate the applicability of the TLS. Gravimetric surface moisture samples were used to calibrate the relation between reflectance and surface moisture. Results reveal a robust negative relation for the full range of possible surface moisture contents (0%-25%), with a correlation-coefficient squared of 0.85 and a root-mean-square error of 2.7%. This relation holds between 20 and 60 m from the TLS. Within this distance the TLS typically produces O (106-107) data points, which we averaged into surface moisture maps with a 1 × 1 m resolution. This grid size largely removes small reflectance disturbances induced by, for example, footprints or tire tracks, while retaining larger scale moisture trends.

  14. Nanoscale silver-assisted wet etching of crystalline silicon for anti-reflection surface textures.

    Science.gov (United States)

    Li, Rui; Wang, Shuling; Chuwongin, Santhad; Zhou, Weidong

    2013-01-01

    We report here an electro-less metal-assisted chemical etching (MacEtch) process as light management surface-texturing technique for single crystalline Si photovoltaics. Random Silver nanostructures were formed on top of the Si surface based on the thin film evaporation and annealing process. Significant reflection reduction was obtained from the fabricated Si sample, with approximately 2% reflection over a wide spectra range (300 to 1050 nm). The work demonstrates the potential of MacEtch process for anti-reflection surface texture fabrication of large area, high efficiency, and low cost thin film solar cell.

  15. Effects of surface irregularities on intensity data from laser scanning: an experimental approach.

    Directory of Open Access Journals (Sweden)

    G. Teza

    2008-06-01

    Full Text Available The results of an experiment carried out with the aim to investigate the role of surface irregularities on the intensity data provided by a terrestrial laser scanner (TLS survey are reported here. Depending on surface roughness, the interaction between an electromagnetic wave and microscopic irregularities leads to a Lambertian-like diffusive light reflection, allowing the TLS to receive the backscattered component of the signal. The described experiment consists in a series of TLS-based acquisitions of a rotating artificial target specifically conceived in order to highlight the effects on the intensity data due to surface irregularity. This target is articulated in a flat plate and in an irregular surface, whose macro-roughness has a characteristic length with the same order of the spot size. Results point out the different behavior of the plates. The intensity of the signal backscattered by the planar element decreases if the incidence angle increases, whereas the intensity of the signal backscattered by the irregular surface is almost constant if the incidence angle varies. Since the typical surfaces acquired in a geological/geophysical survey are generally irregular, these results imply that the intensity data can be easily used in order to evaluate the reflectance of the material at the considered wavelength, e.g. for pattern recognition purposes.

  16. Laser-based structural sensing and surface damage detection

    Science.gov (United States)

    Guldur, Burcu

    Damage due to age or accumulated damage from hazards on existing structures poses a worldwide problem. In order to evaluate the current status of aging, deteriorating and damaged structures, it is vital to accurately assess the present conditions. It is possible to capture the in situ condition of structures by using laser scanners that create dense three-dimensional point clouds. This research investigates the use of high resolution three-dimensional terrestrial laser scanners with image capturing abilities as tools to capture geometric range data of complex scenes for structural engineering applications. Laser scanning technology is continuously improving, with commonly available scanners now capturing over 1,000,000 texture-mapped points per second with an accuracy of ~2 mm. However, automatically extracting meaningful information from point clouds remains a challenge, and the current state-of-the-art requires significant user interaction. The first objective of this research is to use widely accepted point cloud processing steps such as registration, feature extraction, segmentation, surface fitting and object detection to divide laser scanner data into meaningful object clusters and then apply several damage detection methods to these clusters. This required establishing a process for extracting important information from raw laser-scanned data sets such as the location, orientation and size of objects in a scanned region, and location of damaged regions on a structure. For this purpose, first a methodology for processing range data to identify objects in a scene is presented and then, once the objects from model library are correctly detected and fitted into the captured point cloud, these fitted objects are compared with the as-is point cloud of the investigated object to locate defects on the structure. The algorithms are demonstrated on synthetic scenes and validated on range data collected from test specimens and test-bed bridges. The second objective of

  17. Application of YAG laser cladding to the flange seating surface

    International Nuclear Information System (INIS)

    Nakanishi, Koki; Ninomiya, Kazuyuki; Nezaki, Koji

    1999-01-01

    Stainless cladding on carbon steel is usually conducted by shielded metal arc welding (SMAW) or gas tungsten arc welding (GTAW). YAG ( Yttrium-Aluminum-Garnet) laser welding is superior to these methods of welding in the following respects : (1) The heat affected zone (HAZ) is narrower and there is less distortion. (2) YAG laser cladding has the required chemical compositions, even with possibly fewer welding layers under controlled dilution. (3) Greater welding speed. YAG laser cladding application to vessel flange seating surfaces was examined in this study and the results are discussed. The following objectives were carried out : (1) Determination of welding conditions for satisfactory cladding layers and (2) whether cladding would be adequately possible at a cornered section of a stair-like plate, assuming actual flange shape. (3) Measurement of welding distortion and heat affected zone in carbon steel. The welding conditions for producing no-crack deposit with low dilution in carbon steel were clarified and welding by which cladding at cornered section would be possible was achieved. welding distortion by YAG laser was found less than with GTAW and HAZ made by first layer welding could be tempered appropriately by second layer welding. (author)

  18. Surface plasmon resonance assisted rapid laser joining of glass

    Energy Technology Data Exchange (ETDEWEB)

    Zolotovskaya, Svetlana A.; Tang, Guang; Abdolvand, Amin, E-mail: a.abdolvand@dundee.ac.uk [School of Engineering, Physics and Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom); Wang, Zengbo [School of Electronic Engineering, Bangor University, Bangor LL57 1UT (United Kingdom)

    2014-08-25

    Rapid and strong joining of clear glass to glass containing randomly distributed embedded spherical silver nanoparticles upon nanosecond pulsed laser irradiation (∼40 ns and repetition rate of 100 kHz) at 532 nm is demonstrated. The embedded silver nanoparticles were ∼30–40 nm in diameter, contained in a thin surface layer of ∼10 μm. A joint strength of 12.5 MPa was achieved for a laser fluence of only ∼0.13 J/cm{sup 2} and scanning speed of 10 mm/s. The bonding mechanism is discussed in terms of absorption of the laser energy by nanoparticles and the transfer of the accumulated localised heat to the surrounding glass leading to the local melting and formation of a strong bond. The presented technique is scalable and overcomes a number of serious challenges for a widespread adoption of laser-assisted rapid joining of glass substrates, enabling applications in the manufacture of microelectronic devices, sensors, micro-fluidic, and medical devices.

  19. Thermal effect of laser ablation on the surface of carbon fiber reinforced plastic during laser processing

    Science.gov (United States)

    Ohkubo, Tomomasa; Sato, Yuji; Matsunaga, Ei-ichi; Tsukamoto, Masahiro

    2018-02-01

    Although laser processing is widely used for many applications, the cutting quality of carbon fiber reinforced plastic (CFRP) decreases around the heat-affected zone (HAZ) during laser processing. Carbon fibers are exposed around the HAZ, and tensile strength decreases with increasing length of the HAZ. Some theoretical studies of thermal conductions that do not consider fluid dynamics have been performed; however, theoretical considerations that include the dynamics of laser ablation are scarce. Using removed mass and depth observed from experiments, the dynamics of laser ablation of CFRP with high-temperature and high-pressure of compressive gas is simulated herein. In this calculation, the mushroom-like shape of laser ablation is qualitatively simulated compared with experiments using a high-speed camera. Considering the removal temperature of the resin and the temperature distribution at each point on the surface, the simulation results suggest that a wide area of the resin is removed when the processing depth is shallow, and a rounded kerf is generated as the processing depth increases.

  20. Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

    International Nuclear Information System (INIS)

    Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

    2014-01-01

    High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

  1. Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

    Science.gov (United States)

    Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

    2014-06-01

    High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

  2. Biomimetic surface structuring using cylindrical vector femtosecond laser beams

    Science.gov (United States)

    Skoulas, Evangelos; Manousaki, Alexandra; Fotakis, Costas; Stratakis, Emmanuel

    2017-03-01

    We report on a new, single-step and scalable method to fabricate highly ordered, multi-directional and complex surface structures that mimic the unique morphological features of certain species found in nature. Biomimetic surface structuring was realized by exploiting the unique and versatile angular profile and the electric field symmetry of cylindrical vector (CV) femtosecond (fs) laser beams. It is shown that, highly controllable, periodic structures exhibiting sizes at nano-, micro- and dual- micro/nano scales can be directly written on Ni upon line and large area scanning with radial and azimuthal polarization beams. Depending on the irradiation conditions, new complex multi-directional nanostructures, inspired by the Shark’s skin morphology, as well as superhydrophobic dual-scale structures mimicking the Lotus’ leaf water repellent properties can be attained. It is concluded that the versatility and features variations of structures formed is by far superior to those obtained via laser processing with linearly polarized beams. More important, by exploiting the capabilities offered by fs CV fields, the present technique can be further extended to fabricate even more complex and unconventional structures. We believe that our approach provides a new concept in laser materials processing, which can be further exploited for expanding the breadth and novelty of applications.

  3. Submonolayer Quantum Dots for High Speed Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Zakharov ND

    2007-01-01

    Full Text Available AbstractWe report on progress in growth and applications of submonolayer (SML quantum dots (QDs in high-speed vertical-cavity surface-emitting lasers (VCSELs. SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers. Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting lasers (VCSELs is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than 10−12has been achieved in a temperature range 25–85 °Cwithout current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission.

  4. SO2 frost - UV-visible reflectivity and Io surface coverage

    Science.gov (United States)

    Nash, D. B.; Fanale, F. P.; Nelson, R. M.

    1980-01-01

    The reflectance spectrum in the range 0.24-0.85 microns of SO2 frost is measured in light of the discovery of SO2 gas in the atmosphere of Io and the possible discovery of the frost on its surface. Frost deposits up to 1.5 mm thick were grown in vacuum at 130 K and bi-directional reflectance spectra were obtained. Typical SO2 frost is found to exhibit very low reflectivity (2-5%) at 0.30 microns, rising steeply at 0.32 microns to attain a maximum reflectivity (75-80%) at 4.0 microns and uniformly high reflectivity throughout the visible and near infrared. Comparison with the full disk spectrum of Io reveals that no more than 20% of the surface can be covered with optically thick SO2 frost. Combinations of surface materials including SO2 frost which can produce the observed spectrum are indicated.

  5. Virtual environment assessment for laser-based vision surface profiling

    Science.gov (United States)

    ElSoussi, Adnane; Al Alami, Abed ElRahman; Abu-Nabah, Bassam A.

    2015-03-01

    Oil and gas businesses have been raising the demand from original equipment manufacturers (OEMs) to implement a reliable metrology method in assessing surface profiles of welds before and after grinding. This certainly mandates the deviation from the commonly used surface measurement gauges, which are not only operator dependent, but also limited to discrete measurements along the weld. Due to its potential accuracy and speed, the use of laser-based vision surface profiling systems have been progressively rising as part of manufacturing quality control. This effort presents a virtual environment that lends itself for developing and evaluating existing laser vision sensor (LVS) calibration and measurement techniques. A combination of two known calibration techniques is implemented to deliver a calibrated LVS system. System calibration is implemented virtually and experimentally to scan simulated and 3D printed features of known profiles, respectively. Scanned data is inverted and compared with the input profiles to validate the virtual environment capability for LVS surface profiling and preliminary assess the measurement technique for weld profiling applications. Moreover, this effort brings 3D scanning capability a step closer towards robust quality control applications in a manufacturing environment.

  6. Perceived Average Orientation Reflects Effective Gist of the Surface.

    Science.gov (United States)

    Cha, Oakyoon; Chong, Sang Chul

    2018-03-01

    The human ability to represent ensemble visual information, such as average orientation and size, has been suggested as the foundation of gist perception. To effectively summarize different groups of objects into the gist of a scene, observers should form ensembles separately for different groups, even when objects have similar visual features across groups. We hypothesized that the visual system utilizes perceptual groups characterized by spatial configuration and represents separate ensembles for different groups. Therefore, participants could not integrate ensembles of different perceptual groups on a task basis. We asked participants to determine the average orientation of visual elements comprising a surface with a contour situated inside. Although participants were asked to estimate the average orientation of all the elements, they ignored orientation signals embedded in the contour. This constraint may help the visual system to keep the visual features of occluding objects separate from those of the occluded objects.

  7. On the surface topography of ultrashort laser pulse treated steel surfaces

    NARCIS (Netherlands)

    Obona, J. Vincenc; Ocelik, V.; Skolski, J. Z. P.; Mitko, V. S.; Romer, G. R. B. E.; in't Veld, A. J. Huis; De Hosson, J. Th M.; Römer, G.R.B.E.; Huis in’t Veld, A.J.

    2011-01-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the

  8. On the surface topography of ultrashort laser pulse treated steel surface

    NARCIS (Netherlands)

    Vincenc Obona, J.; Ocelik, V.; Skolski, J.Z.P.; Mitko, V.S.; Mitko, S.; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert; de Hosson, J.Th.M.

    2011-01-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the

  9. Laser surface textured titanium alloy (Ti–6Al–4V): Part 1 – Surface characterization

    Energy Technology Data Exchange (ETDEWEB)

    Pfleging, Wilhelm [Karlsruhe Institute of Technology, IAM-AWP, P.O. Box 3640, 76021 Karlsruhe (Germany); Karlsruhe Nano Micro Facility, H.-von-Helmholtz-Pl. 1, 76344 Egg.-Leopoldshafen (Germany); Kumari, Renu [Department of Metal. and Maters. Eng., I. I. T. Kharagpur, WB 721302 (India); Besser, Heino [Karlsruhe Institute of Technology, IAM-AWP, P.O. Box 3640, 76021 Karlsruhe (Germany); Scharnweber, Tim [Karlsruhe Institute of Technology, IBG-1, P.O. Box 3640, 76021 Karlsruhe (Germany); Majumdar, Jyotsna Dutta, E-mail: jyotsna@metal.iitkgp.ernet.in [Department of Metal. and Maters. Eng., I. I. T. Kharagpur, WB 721302 (India)

    2015-11-15

    Highlights: • Texturing of Ti–6Al–4V with linear and dimple patterns are developed with ArF laser. • Linear textures have width of 25 μm and are at an interval of 20 μm. • Dimple textures are equi-spaced and have a diameter of 60 μm. • Significant refinement of microstructure in textured zone as compared to substrate. • Increased wettability of the textured surface against simulated body fluid. - Abstract: In the present study, a detailed study of the characterization of laser-surface textured titanium alloy (Ti–6Al–4V) with line and dimple geometry developed by using an ArF excimer laser operating at a wavelength of 193 nm with a pulse length of 5 ns is undertaken. The characterization of the textured surface (both the top surface and cross section) is carried out by scanning electron microscopy, electron back scattered diffraction (EBSD) technique and X-ray diffraction techniques. There is refinement of microstructure along with presence of titanium oxides (rutile, anatase and few Ti{sub 2}O{sub 3} phase) in the textured surface as compared to as-received one. The area fractions of linear texture and dimple texture measured by image analysis software are 45% and 20%, respectively. The wettability is increased after laser texturing. The total surface energy is decreased due to linear (29.6 mN/m) texturing and increased due to dimple (67.6 mN/m) texturing as compared to as-received Ti–6Al–4V (37 mN/m). The effect of polar component is more in influencing the surface energy of textured surface.

  10. Laser surface textured titanium alloy (Ti–6Al–4V): Part 1 – Surface characterization

    International Nuclear Information System (INIS)

    Pfleging, Wilhelm; Kumari, Renu; Besser, Heino; Scharnweber, Tim; Majumdar, Jyotsna Dutta

    2015-01-01

    Highlights: • Texturing of Ti–6Al–4V with linear and dimple patterns are developed with ArF laser. • Linear textures have width of 25 μm and are at an interval of 20 μm. • Dimple textures are equi-spaced and have a diameter of 60 μm. • Significant refinement of microstructure in textured zone as compared to substrate. • Increased wettability of the textured surface against simulated body fluid. - Abstract: In the present study, a detailed study of the characterization of laser-surface textured titanium alloy (Ti–6Al–4V) with line and dimple geometry developed by using an ArF excimer laser operating at a wavelength of 193 nm with a pulse length of 5 ns is undertaken. The characterization of the textured surface (both the top surface and cross section) is carried out by scanning electron microscopy, electron back scattered diffraction (EBSD) technique and X-ray diffraction techniques. There is refinement of microstructure along with presence of titanium oxides (rutile, anatase and few Ti_2O_3 phase) in the textured surface as compared to as-received one. The area fractions of linear texture and dimple texture measured by image analysis software are 45% and 20%, respectively. The wettability is increased after laser texturing. The total surface energy is decreased due to linear (29.6 mN/m) texturing and increased due to dimple (67.6 mN/m) texturing as compared to as-received Ti–6Al–4V (37 mN/m). The effect of polar component is more in influencing the surface energy of textured surface.

  11. Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, W., E-mail: wyman.zhuang@dsto.defence.gov.au [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Liu, Q.; Djugum, R.; Sharp, P.K. [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Paradowska, A. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2232 (Australia)

    2014-11-30

    Highlights: • Deep surface rolling as a post-repair enhancement technology was applied to the laser cladded 7075-T651 aluminium alloy specimens that simulated corrosion damage blend-out repair. • The residual stresses induced by the deep surface rolling process were measured. • The deep surface rolling process can introduce deep and high magnitude compressive residual stresses beyond the laser clad and substrate interface. • Spectrum fatigue test showed the fatigue life was significantly increased by deep surface rolling. - Abstract: Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface.

  12. Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy

    International Nuclear Information System (INIS)

    Zhuang, W.; Liu, Q.; Djugum, R.; Sharp, P.K.; Paradowska, A.

    2014-01-01

    Highlights: • Deep surface rolling as a post-repair enhancement technology was applied to the laser cladded 7075-T651 aluminium alloy specimens that simulated corrosion damage blend-out repair. • The residual stresses induced by the deep surface rolling process were measured. • The deep surface rolling process can introduce deep and high magnitude compressive residual stresses beyond the laser clad and substrate interface. • Spectrum fatigue test showed the fatigue life was significantly increased by deep surface rolling. - Abstract: Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface

  13. Evaluation of BRDF Archetypes for Representing Surface Reflectance Anisotropy Using MODIS BRDF Data

    OpenAIRE

    Zhang, Hu; Jiao, Ziti; Dong, Yadong; Li, Xiaowen

    2015-01-01

    Bidirectional reflectance distribution function (BRDF) archetypes extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo product over the global Earth Observing System Land Validation Core Sites can be used to simplify BRDF models. The present study attempts to evaluate the representativeness of BRDF archetypes for surface reflectance anisotropy. Five-year forward-modeled MODIS multi-angular reflectance (MCD-ref) and aditional actual MODIS multi-angular observat...

  14. Surface Modifications with Laser Synthesized Mo Modified Coating

    Science.gov (United States)

    Sun, Lu; Chen, Hao; Liu, Bo

    2013-01-01

    Mg-Cu-Al was first used to improve the surface performance of TA15 titanium alloys by means of laser cladding technique. The synthesis of hard composite coating on TA15 titanium alloy by laser cladding of Mg-Cu-Al-B4C/Mo pre-placed powders was investigated by means of scanning electron microscope, energy dispersive spectrometer and high resolution transmission electron microscope. Experimental results indicated that such composite coating mainly consisted of TiB2, TiB, TiC, Ti3Al and AlCuMg. Compared with TA15 alloy substrate, an improvement of wear resistance was observed for this composite coating due to the actions of fine grain, amorphous and hard phase strengthening.

  15. Surface roughness and gloss study of prints: application of specular reflection at near infrared

    International Nuclear Information System (INIS)

    Silfsten, P; Dutta, R; Pääkkönen, P; Peiponen, K-E; Tåg, C-M; Gane, P A C

    2012-01-01

    Absolute reflectance data were measured with a spectrophotometer in the visible and near infrared (NIR) spectral range. The specular reflectance data in the NIR were used for the assessment of the surface roughness of magenta, yellow, cyan and black prints on paper. In addition, surface roughness data obtained from the prints with a mechanical diamond stylus, an optical profiling system and the spectrophotometer are compared with each other. The surface roughness obtained with the aid of the spectrophotometer data suggests a smoother surface than when measured with the diamond stylus and the optical profiling system. The gloss of the prints can be obtained from the absolute specular reflectance spectra in the spectral region of visible light. It is shown that specular reflection data at a fixed wavelength in the NIR are useful also in the interpretation of gloss in the visible spectral range, but using an unconventional grazing angle of incidence. (paper)

  16. NOAA Climate Data Record (CDR) of AVHRR Surface Reflectance, Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains gridded daily surface reflectance and brightness temperatures derived from the Advanced Very High Resolution Radiometer (AVHRR) sensors onboard...

  17. LiDAR Relative Reflectivity Surface (2011) for the St. Thomas East End Reserve, St. Thomas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 0.3x0.3 meter resolution relative seafloor reflectivity surface for the St. Thomas East End Reserve...

  18. Accounting for surface reflectance anisotropy in satellite retrievals of tropospheric NO₂

    NARCIS (Netherlands)

    Zhou, Yipin; Brunner, D.; Spurr, R.J.D.; Boersma, K.F.; Sneep, M.; Popp, C.; Buchmann, B.

    2010-01-01

    Surface reflectance is a key parameter in satellite trace gas retrievals in the UV/visible range and in particular for the retrieval of nitrogen dioxide (NO2) vertical tropospheric columns (VTCs). Current operational retrievals rely on coarse-resolution reflectance data and do not account for the

  19. Backscattered EM-wave manipulation using low cost 1-bit reflective surface at W-band

    Science.gov (United States)

    Taher Al-Nuaimi, Mustafa K.; Hong, Wei; He, Yejun

    2018-04-01

    The design of low cost 1-bit reflective (non-absorptive) surfaces for manipulation of backscattered EM-waves and radar cross section (RCS) reduction at W-band is presented in this article. The presented surface is designed based on the reflection phase cancellation principle. The unit cell used to compose the proposed surface has an obelus (division symbol of short wire and two disks above and below) like shape printed on a grounded dielectric material. Using this unit cell, surfaces that can efficiently manipulate the backscattered RCS pattern by using the proposed obelus-shaped unit cell (as ‘0’ element) and its mirrored unit cell (as ‘1’ element) in one surface with a 180°  ±  35° reflection phase difference between their reflection phases are designed. The proposed surfaces can generate various kinds of backscattered RCS patterns, such as single, three, or four lobes or even a low-level (reduced RCS) diffused reflection pattern when those two unit cells are distributed randomly across the surface aperture. For experimental characterization purposes, a 50  ×  50 mm2 surface is fabricated and measured.

  20. Nonlinear reflection of a spherically divergent N-wave from a plane surface: Optical interferometry measurements in air

    International Nuclear Information System (INIS)

    Karzova, M.; Yuldashev, P.; Khokhlova, V.; Ollivier, S.; Blanc-Benon, Ph.

    2015-01-01

    Mach stem is a well-known structure typically observed in the process of strong (acoustic Mach numbers greater than 0.4) step-shock waves reflection from a rigid boundary. However, this phenomenon has been much less studied for weak shocks in nonlinear acoustic fields where Mach numbers are in the range from 0.001 to 0.01 and pressure waveforms have more complicated waveforms than step shocks. The goal of this work was to demonstrate experimentally how nonlinear reflection occurs in air for very weak spherically divergent acoustic spark-generated pulses resembling an N-wave. Measurements of reflection patterns were performed using a Mach-Zehnder interferometer. A thin laser beam with sub-millimeter cross-section was used to obtain the time resolution of 0.4 µs, which is 6 times higher than the time resolution of the condenser microphones. Pressure waveforms were reconstructed using the inverse Abel transform applied to the phase of the signal measured by the interferometer. The Mach stem formation was observed experimentally as a result of collision of the incident and reflected shock pulses. It was shown that irregular reflection of the pulse occurred in a dynamic way and the length of the Mach stem increased linearly while the pulse propagated along the surface. Since the front shock of the spark-generated pulse was steeper than the rear shock, irregular type of reflection was observed only for the front shock of the pulse while the rear shock reflection occurred in a regular regime

  1. Nonlinear reflection of a spherically divergent N-wave from a plane surface: Optical interferometry measurements in air

    Energy Technology Data Exchange (ETDEWEB)

    Karzova, M., E-mail: masha@acs366.phys.msu.ru [Laboratoire de Mécanique des Fluides et d’Acoustique, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Yuldashev, P.; Khokhlova, V. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Ollivier, S.; Blanc-Benon, Ph. [Laboratoire de Mécanique des Fluides et d’Acoustique, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France)

    2015-10-28

    Mach stem is a well-known structure typically observed in the process of strong (acoustic Mach numbers greater than 0.4) step-shock waves reflection from a rigid boundary. However, this phenomenon has been much less studied for weak shocks in nonlinear acoustic fields where Mach numbers are in the range from 0.001 to 0.01 and pressure waveforms have more complicated waveforms than step shocks. The goal of this work was to demonstrate experimentally how nonlinear reflection occurs in air for very weak spherically divergent acoustic spark-generated pulses resembling an N-wave. Measurements of reflection patterns were performed using a Mach-Zehnder interferometer. A thin laser beam with sub-millimeter cross-section was used to obtain the time resolution of 0.4 µs, which is 6 times higher than the time resolution of the condenser microphones. Pressure waveforms were reconstructed using the inverse Abel transform applied to the phase of the signal measured by the interferometer. The Mach stem formation was observed experimentally as a result of collision of the incident and reflected shock pulses. It was shown that irregular reflection of the pulse occurred in a dynamic way and the length of the Mach stem increased linearly while the pulse propagated along the surface. Since the front shock of the spark-generated pulse was steeper than the rear shock, irregular type of reflection was observed only for the front shock of the pulse while the rear shock reflection occurred in a regular regime.

  2. Wetting and other physical characteristics of polycarbonate surface textured using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [ME Department, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Khaled, M. [CHEM Department, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Abu-Dheir, N.; Al-Aqeeli, N.; Said, S.A.M. [ME Department, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Ahmed, A.O.M. [CHEM Department, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Varanasi, K.K.; Toumi, Y.K. [Mechanical Engineering, Massachusetts Institute of Technology, Boston (United States)

    2014-11-30

    Highlights: • Laser causes micro/nano size pores and shallow fine-size cavities. • Crystallinity at surface is 18% after laser treatment increasing hydrophobicity. • Surface hydrophobicity improves after laser treatment. • Microhardness increases twofold after laser treatment process. • Residual stress is compressive and scratch hardness is 110 ± 11 MPa. • Optical transmittance reduces by 15% after laser treatment. - Abstract: Surface texturing of polycarbonate glass is carried out for improved hydrophobicity via controlled laser ablation at the surface. Optical and physical characteristics of the laser treated layer are examined using analytical tools including optical, atomic force, and scanning electron microscopes, Fourier transform infrared spectroscopy, and X-ray diffraction. Contact angle measurements are carried out to assess the hydrophobicity of the laser treated surface. Residual stress in the laser ablated layer is determined using the curvature method, and microhardnes and scratch resistance are analyzed using a micro-tribometer. Findings reveal that textured surfaces compose of micro/nano pores with fine cavities and increase the contact angle to hydrophobicity such a way that contact angles in the range of 120° are resulted. Crystallization of the laser treated surface reduces the optical transmittance by 15%, contributes to residual stress formation, and enhances the microhardness by twice the value of untreated polycarbonate surface. In addition, laser treatment improves surface scratch resistance by 40%.

  3. Patellar Skin Surface Temperature by Thermography Reflects Knee Osteoarthritis Severity

    Directory of Open Access Journals (Sweden)

    Anna E. Denoble

    2010-01-01

    Full Text Available Background Digital infrared thermal imaging is a means of measuring the heat radiated from the skin surface. Our goal was to develop and assess the reproducibility of serial infrared measurements of the knee and to assess the association of knee temperature by region of interest with radiographic severity of knee Osteoarthritis (rOA. Methods A total of 30 women (15 Cases with symptomatic knee OA and 15 age-matched Controls without knee pain or knee OA participated in this study. Infrared imaging was performed with a Meditherm Med2000™ Pro infrared camera. The reproducibility of infrared imaging of the knee was evaluated through determination of intraclass correlation coefficients (ICCs for temperature measurements from two images performed 6 months apart in Controls whose knee status was not expected to change. The average cutaneous temperature for each of five knee regions of interest was extracted using WinTes software. Knee x-rays were scored for severity of rOA based on the global Kellgren-Lawrence grading scale. Results The knee infrared thermal imaging procedure used here demonstrated long-term reproducibility with high ICCs (0.50–0.72 for the various regions of interest in Controls. Cutaneous temperature of the patella (knee cap yielded a significant correlation with severity of knee rOA (R = 0.594, P = 0.02. Conclusion The skin temperature of the patellar region correlated with x-ray severity of knee OA. This method of infrared knee imaging is reliable and as an objective measure of a sign of inflammation, temperature, indicates an interrelationship of inflammation and structural knee rOA damage.

  4. Patellar skin surface temperature by thermography reflects knee osteoarthritis severity.

    Science.gov (United States)

    Denoble, Anna E; Hall, Norine; Pieper, Carl F; Kraus, Virginia B

    2010-10-15

    Digital infrared thermal imaging is a means of measuring the heat radiated from the skin surface. Our goal was to develop and assess the reproducibility of serial infrared measurements of the knee and to assess the association of knee temperature by region of interest with radiographic severity of knee Osteoarthritis (rOA). A total of 30 women (15 Cases with symptomatic knee OA and 15 age-matched Controls without knee pain or knee OA) participated in this study. Infrared imaging was performed with a Meditherm Med2000™ Pro infrared camera. The reproducibility of infrared imaging of the knee was evaluated through determination of intraclass correlation coefficients (ICCs) for temperature measurements from two images performed 6 months apart in Controls whose knee status was not expected to change. The average cutaneous temperature for each of five knee regions of interest was extracted using WinTes software. Knee x-rays were scored for severity of rOA based on the global Kellgren-Lawrence grading scale. The knee infrared thermal imaging procedure used here demonstrated long-term reproducibility with high ICCs (0.50-0.72 for the various regions of interest) in Controls. Cutaneous temperature of the patella (knee cap) yielded a significant correlation with severity of knee rOA (R = 0.594, P = 0.02). The skin temperature of the patellar region correlated with x-ray severity of knee OA. This method of infrared knee imaging is reliable and as an objective measure of a sign of inflammation, temperature, indicates an interrelationship of inflammation and structural knee rOA damage.

  5. Calculation of Reflectance and Transmittance of Coating With Optically Rough Surfaces

    International Nuclear Information System (INIS)

    El-Depsy, A.; Shawky, A.M.

    2011-01-01

    For ideal surfaces, components of the reflected beam are related to the components of the incident beam by Fresnel reflection equation. The surfaces encountered in engineering applications deviate from ideal as a result of roughness, oxidization and contamination; hence the Radiative properties of these real surfaces differ greatly from those predicted by electromagnetic theory. In regard to problems of radiative heat transfer; the roughness of surfaces may be divided into two categories: (1) small surface irregularities such that the incident radiation cannot undergo more than a single reflection, (2) deep cavities in which the incident radiation undergoes multi-reflection. The normally incident radiation from rough surface having small irregularities is reflected partly specularly and partly diffusely [1]. Kubelka-Munk theory (K-M) [2] describes optical characteristics (e.g. reflectance, transmittance and absorbance) by a variety of light scattering media including paints, textiles and papers, and It is widely used in various industrial applications. Moder developments in radiative transfer theory (RTT) enable the derivation of (K-M) parameters from first principles [3]. Kubelka and Munk proposed a theory based on a model of two light fluxes travelling in the forward and backward directions. Subsequently a number of authors refined the theory and compared it with experimental data [4]. Several authors attempted to relate the Kubelka- Munk coefficients to the transport coefficients [5,6

  6. Retrieval and Validation of aerosol optical properties from AHI measurements: impact of surface reflectance assumption

    Science.gov (United States)

    Lim, H.; Choi, M.; Kim, J.; Go, S.; Chan, P.; Kasai, Y.

    2017-12-01

    This study attempts to retrieve the aerosol optical properties (AOPs) based on the spectral matching method, with using three visible and one near infrared channels (470, 510, 640, 860nm). This method requires the preparation of look-up table (LUT) approach based on the radiative transfer modeling. Cloud detection is one of the most important processes for guaranteed quality of AOPs. Since the AHI has several infrared channels, which are very advantageous for cloud detection, clouds can be removed by using brightness temperature difference (BTD) and spatial variability test. The Yonsei Aerosol Retrieval (YAER) algorithm is basically utilized on a dark surface, therefore a bright surface (e.g., desert, snow) should be removed first. Then we consider the characteristics of the reflectance of land and ocean surface using three visible channels. The known surface reflectivity problem in high latitude area can be solved in this algorithm by selecting appropriate channels through improving tests. On the other hand, we retrieved the AOPs by obtaining the visible surface reflectance using NIR to normalized difference vegetation index short wave infrared (NDVIswir) relationship. ESR tends to underestimate urban and cropland area, we improved the visible surface reflectance considering urban effect. In this version, ocean surface reflectance is using the new cox and munk method which considers ocean bidirectional reflectance distribution function (BRDF). Input of this method has wind speed, chlorophyll, salinity and so on. Based on validation results with the sun-photometer measurement in AErosol Robotic NETwork (AERONET), we confirm that the quality of Aerosol Optical Depth (AOD) from the YAER algorithm is comparable to the product from the Japan Aerospace Exploration Agency (JAXA) retrieval algorithm. Our future update includes a consideration of improvement land surface reflectance by hybrid approach, and non-spherical aerosols. This will improve the quality of YAER

  7. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuo; Chen, Rongzhang; Nelsen, Bryan; Chen, Kevin, E-mail: pec9@pitt.edu [Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Liu, Lei; Huang, Xi; Lu, Yongfeng [Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States)

    2016-03-15

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.

  8. Operation of a novel hot-electron vertical-cavity surface-emitting laser

    Science.gov (United States)

    Balkan, Naci; O'Brien-Davies, Angela; Thoms, A. B.; Potter, Richard J.; Poolton, Nigel; Adams, Michael J.; Masum, J.; Bek, Alpan; Serpenguzel, Ali; Aydinli, Atilla; Roberts, John S.

    1998-07-01

    The hot Electron Light Emission and Lasing in Semiconductor Heterostructures devices (HELLISH-1) is novel surface emitter consisting of a GaAs quantum well, within the depletion region, on the n side of Ga1-xAlxAs p- n junction. It utilizes hot electron transport parallel to the layers and injection of hot electron hole pairs into the quantum well through a combination of mechanisms including tunnelling, thermionic emission and diffusion of `lucky' carriers. Super Radiant HELLISH-1 is an advanced structure incorporating a lower distributed Bragg reflector (DBR). Combined with the finite reflectivity of the upper semiconductor-air interface reflectivity it defines a quasi- resonant cavity enabling emission output from the top surface with a higher spectral purity. The output power has increased by two orders of magnitude and reduced the full width at half maximum (FWHM) to 20 nm. An upper DBR added to the structure defines HELLISH-VCSEL which is currently the first operational hot electron surface emitting laser and lases at room temperature with a 1.5 nm FWHM. In this work we demonstrate and compare the operation of UB-HELLISH-1 and HELLISH-VCSEL using experimental and theoretical reflectivity spectra over an extensive temperature range.

  9. Evolution of Oxygen Deficiency Center on Fused Silica Surface Irradiated by Ultraviolet Laser and Posttreatment

    Directory of Open Access Journals (Sweden)

    Hai-Bing Lü

    2014-01-01

    Full Text Available Evolution of oxygen deficiency centers (ODCs on a fused silica surface irradiated using a 355 nm ultraviolet (UV laser beam in both vacuum and atmospheric conditions was quantitatively studied using photoluminescence and X-ray photoelectron spectroscopy. When the fusedsilica surface was exposed to the UV laser in vacuum, the laser damage threshold was decreased whereas the concentration of the ODCs was increased. For the fuse silica operated under the high power lasers, creation of ODCs on their surface resulted from the UV laser irradiation, and this is more severe in a high vacuum. The laser fluence and/or laser intensity have significant effects on the increase of the ODCs concentration. The ODCs can be effectively repaired using postoxygen plasma treatment and UV laser irradiation in an excessive oxygen environment. Results also demonstrated that the “gain” and “loss” of oxygen at the silica surface is a reversible and dynamic process.

  10. Surface Texturing of CVD Diamond Assisted by Ultrashort Laser Pulses

    Directory of Open Access Journals (Sweden)

    Daniele M. Trucchi

    2017-11-01

    Full Text Available Diamond is a wide bandgap semiconductor with excellent physical properties which allow it to operate under extreme conditions. However, the technological use of diamond was mostly conceived for the fabrication of ultraviolet, ionizing radiation and nuclear detectors, of electron emitters, and of power electronic devices. The use of nanosecond pulse excimer lasers enabled the microstructuring of diamond surfaces, and refined techniques such as controlled ablation through graphitization and etching by two-photon surface excitation are being exploited for the nanostructuring of diamond. On the other hand, ultrashort pulse lasers paved the way for a more accurate diamond microstructuring, due to reduced thermal effects, as well as an effective surface nanostructuring, based on the formation of periodic structures at the nanoscale. It resulted in drastic modifications of the optical and electronic properties of diamond, of which “black diamond” films are an example for future high-temperature solar cells as well as for advanced optoelectronic platforms. Although experiments on diamond nanostructuring started almost 20 years ago, real applications are only today under implementation.

  11. Simple laser vision sensor calibration for surface profiling applications

    Science.gov (United States)

    Abu-Nabah, Bassam A.; ElSoussi, Adnane O.; Al Alami, Abed ElRahman K.

    2016-09-01

    Due to the relatively large structures in the Oil and Gas industry, original equipment manufacturers (OEMs) have been implementing custom-designed laser vision sensor (LVS) surface profiling systems as part of quality control in their manufacturing processes. The rough manufacturing environment and the continuous movement and misalignment of these custom-designed tools adversely affect the accuracy of laser-based vision surface profiling applications. Accordingly, Oil and Gas businesses have been raising the demand from the OEMs to implement practical and robust LVS calibration techniques prior to running any visual inspections. This effort introduces an LVS calibration technique representing a simplified version of two known calibration techniques, which are commonly implemented to obtain a calibrated LVS system for surface profiling applications. Both calibration techniques are implemented virtually and experimentally to scan simulated and three-dimensional (3D) printed features of known profiles, respectively. Scanned data is transformed from the camera frame to points in the world coordinate system and compared with the input profiles to validate the introduced calibration technique capability against the more complex approach and preliminarily assess the measurement technique for weld profiling applications. Moreover, the sensitivity to stand-off distances is analyzed to illustrate the practicality of the presented technique.

  12. Laser treatment of a neodymium magnet and analysis of surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Rizwan, M.; Kassas, M.

    2016-08-01

    Laser treatment of neodymium magnet (Nd2Fe14B) surface is carried out under the high pressure nitrogen assisting gas. A thin carbon film containing 12% WC carbide particles with 400 nm sizes are formed at the surface prior to the laser treatment process. Morphological and metallurgical changes in the laser treated layer are examined using the analytical tools. The corrosion resistance of the laser treated surface is analyzed incorporating the potentiodynamic tests carried out in 0.05 M NaCl+0.1 M H2SO4 solution. The friction coefficient of the laser treated surface is measured using the micro-scratch tester. The wetting characteristics of the treated surface are assessed incorporating the sessile water drop measurements. It is found that a dense layer consisting of fine size grains and WC particles is formed in the surface region of the laser treated layer. Corrosion resistance of the surface improves significantly after the laser treatment process. Friction coefficient of laser treated surface is lower than that of the as received surface. Laser treatment results in superhydrophobic characteristics at the substrate surface. The formation of hematite and grain size variation in the treated layer slightly lowers the magnetic strength of the laser treated workpiece.

  13. Emerging applications for vertical cavity surface emitting lasers

    International Nuclear Information System (INIS)

    Harris, J S; O'sullivan, T; Sarmiento, T; Lee, M M; Vo, S

    2011-01-01

    Vertical cavity surface emitting lasers (VCSELs) emitting at 850 nm have experienced explosive growth in the past decade because of their many attractive optical features and incredibly low-cost manufacturability. This review reviews the foundations for GaAs-based VCSEL technology as well as the materials and device challenges to extend the operating wavelength to both shorter and longer wavelengths. We discuss some of the applications that are enabled by the integration of VCSELs with both active and passive semiconductor elements for telecommunications, both in vivo and in vitro biosensing, high-density optical storage and imaging at wavelengths much less than the diffraction limit of light

  14. Femtosecond laser fabrication of microspike-arrays on tungsten surface

    International Nuclear Information System (INIS)

    Sano, Tomokazu; Yanai, Masato; Ohmura, Etsuji; Nomura, Yasumitsu; Miyamoto, Isamu; Hirose, Akio; Kobayashi, Kojiro F.

    2005-01-01

    Microspike-arrays were fabricated by irradiating a femtosecond laser on a tungsten surface through a mask opening in air. The natural logarithms of the calculated intensity distributions diffracted at the edge of the mask opening were qualitatively consistent with the experimental results of the shape and arrays of microspikes fabricated. The shape and the array of microspikes depend on the intensity distribution diffracted at the edge of the mask opening. This microspike-array has the potential to be used as a source of micro emitter tips

  15. Surface modification by EUV laser beam based on capillary discharge

    Czech Academy of Sciences Publication Activity Database

    Frolov, Oleksandr; Koláček, Karel; Schmidt, Jiří; Štraus, Jaroslav; Prukner, Václav; Shukurov, A.

    -, č. 58 (2011), s. 484-487 ISSN 2010-376X. [International Conference on Fusion and Plasma Physics. Bali, Indonésie, 26.10.2011-28.10.2011] R&D Projects: GA AV ČR KAN300100702; GA MŠk LA08024; GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z20430508 Keywords : soft x-ray * EUV * laser * radiation * source * capillary * discharge * plasma * ablation * surface modification Subject RIV: BL - Plasma and Gas Discharge Physics http://www.waset.org/journals/waset/v58/v58-99.pdf

  16. Hybrid fuzzy logic control of laser surface heat treatments

    International Nuclear Information System (INIS)

    Perez, Jose Antonio; Ocana, Jose Luis; Molpeceres, Carlos

    2007-01-01

    This paper presents an advanced hybrid fuzzy logic control system for laser surface heat treatments, which allows to increase significantly the uniformity and final quality of the obtained product, reducing the rejection rate and increasing the productivity and efficiency of the treatment. Basically, the proposed hybrid control structure combines a fuzzy logic controller, with a pure integral action, both fully decoupled, improving the performances of the process with a reasonable design cost, since the system nonlinearities are fully compensated by the fuzzy component of the controller, while the integral action contributes to eliminate the steady-state error

  17. MODIS/Aqua Near Real Time (NRT) Surface Reflectance Daily L2G Global 250m SIN Grid

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS Near Real Time (NRT) Surface Reflectance products are an estimate of the surface spectral reflectance as it would be measured at ground level in the...

  18. Controllable superhydrophobic aluminum surfaces with tunable adhesion fabricated by femtosecond laser

    Science.gov (United States)

    Song, Yuxin; Wang, Cong; Dong, Xinran; Yin, Kai; Zhang, Fan; Xie, Zheng; Chu, Dongkai; Duan, Ji'an

    2018-06-01

    In this study, a facile and detailed strategy to fabricate superhydrophobic aluminum surfaces with controllable adhesion by femtosecond laser ablation is presented. The influences of key femtosecond laser processing parameters including the scanning speed, laser power and interval on the wetting properties of the laser-ablated surfaces are investigated. It is demonstrated that the adhesion between water and superhydrophobic surface can be effectively tuned from extremely low adhesion to high adhesion by adjusting laser processing parameters. At the same time, the mechanism is discussed for the changes of the wetting behaviors of the laser-ablated surfaces. These superhydrophobic surfaces with tunable adhesion have many potential applications, such as self-cleaning surface, oil-water separation, anti-icing surface and liquid transportation.

  19. Surface chemistry and growth mechanisms studies of homo epitaxial (1 0 0) GaAs by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yan Dawei; Wu Weidong; Zhang Hong; Wang Xuemin; Zhang Hongliang; Zhang Weibin; Xiong Zhengwei; Wang Yuying; Shen Changle; Peng Liping; Han Shangjun; Zhou Minjie

    2011-01-01

    In this paper, GaAs thin film has been deposited on thermally desorbed (1 0 0) GaAs substrate using laser molecular beam epitaxy. Scanning electron microscopy, in situ reflection high energy electron diffraction and in situ X-ray photoelectron spectroscopy are applied for evaluation of the surface morphology and chemistry during growth process. The results show that a high density of pits is formed on the surface of GaAs substrate after thermal treatment and the epitaxial thin film heals itself by a step flow growth, resulting in a smoother surface morphology. Moreover, it is found that the incorporation of As species into GaAs epilayer is more efficient in laser molecular beam epitaxy than conventional molecular beam epitaxy. We suggest the growth process is impacted by surface chemistry and morphology of GaAs substrate after thermal treatment and the growth mechanisms are discussed in details.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. A study of laser surface modification of polymers: A comparison in air and water

    DEFF Research Database (Denmark)

    Marla, Deepak; Andersen, Sebastian A.; Zhang, Yang

    2018-01-01

    Laser surface modification is a technique to modify polymer surfaces for various applications. In our earlier work [Physics Procedia, 83:211–217, 2016], we showed that when the laser surface modification process was carried out in water instead of air, the obtained surface characteristics were...... research. The observed images of laser modified surfaces suggest that a hemispherical hump is formed in the case of water at lower laser fluences that breakup with an increase in fluence. Such a behavior was not observed when the process was carried out in air. We explain this phenomenon by simulating...

  2. Reflection-based fibre-optic refractive index sensor using surface plasmon resonance

    Czech Academy of Sciences Publication Activity Database

    Hlubina, P.; Kadulová, M.; Ciprian, D.; Sobota, Jaroslav

    2014-01-01

    Roč. 9, August 19 (2014), 14033:1-5 ISSN 1990-2573 R&D Projects: GA MŠk(CZ) LO1212 Keywords : surface plasmon resonance * fibre-optic sensor * spectral interrogation technique * aqueous solutions of ethanol * refractive index Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.231, year: 2014

  3. Reflections

    Directory of Open Access Journals (Sweden)

    Joanne Embree

    2001-01-01

    Full Text Available Ideally, editorials are written one to two months before publication in the Journal. It was my turn to write this one. I had planned to write the first draft the evening after my clinic on Tuesday, September 11. It didn't get done that night or during the next week. Somehow, the topic that I had originally chosen just didn't seem that important anymore as I, along my friends and colleagues, reflected on the changes that the events of that day were likely to have on our lives.

  4. A comparison of reflectance properties on polymer micro-structured functional surface

    DEFF Research Database (Denmark)

    Regi, Francesco; Li, Dongya; Nielsen, Jannik Boll

    In this study, a functional micro-structure surface [1] has been developed as a combination of arrays of micro ridges. The scope of the surface is to achieve specific directional optical properties: that is, under constrained lighting, maximizing the reflectance from a certain viewing direction, ...

  5. Stimulated Brillouin scattering reflectivity in the case of a spatially smoothed laser beam interacting with an inhomogeneous plasma

    International Nuclear Information System (INIS)

    Tikhonchuk, V.T.; Mounaix, P.; Pesme, D.

    1997-01-01

    The stimulated Brillouin scattering (SBS) instability is investigated theoretically in the case of a spatially smoothed laser beam interacting with an inhomogeneous plasma in the regime of strong ion acoustic damping. The domain of parameters being considered corresponds to most of the present day experiments carried out with nanosecond laser pulses interacting with preformed plasmas: the characteristic length for convective amplification is assumed to be much shorter than the longitudinal correlation length of the laser field. The SBS reflectivity of one individual hot spot is analytically computed taking into account thermal noise emission and pump depletion within the hot spot. The SBS reflectivity of the whole beam is then obtained by summing up the individual hot spot reflectivities in accordance with their statistical distribution. copyright 1997 American Institute of Physics

  6. Tissue differentiation by diffuse reflectance spectroscopy for automated oral and maxillofacial laser surgery: ex vivo pilot study

    Science.gov (United States)

    Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Schmidt, Michael; Douplik, Alexandre

    2010-02-01

    Remote laser surgery lacks of haptic feedback during the laser ablation of tissue. Hence, there is a risk of iatrogenic damage or destruction of anatomical structures like nerves or salivary glands. Diffuse reflectance spectroscopy provides a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from seven various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the seven tissue types and computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerves and salivary glands as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating tissues as guidance for oral and maxillofacial laser surgery by means of diffuse reflectance.

  7. Darkening effect on AZ31B magnesium alloy surface induced by nanosecond pulse Nd:YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Y.C., E-mail: guan0013@e.ntu.edu.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Zhou, W. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Zheng, H.Y.; Li, Z.L. [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore)

    2013-09-01

    Permanent darkening effect was achieved on surface of AZ31B Mg alloy irradiated with nanosecond pulse Nd:YAG laser, and special attention was made to examine how surface structure as well as oxidation affect the darkening effect. Experiments were carried out to characterize morphological evolution and chemical composition of the irradiated areas by optical reflection spectrometer, Talysurf surface profiler, SEM, EDS, and XPS. The darkening effect was found to be occurred at the surface under high laser energy. Optical spectra showed that the induced darkening surface was uniform over the spectral range from 200 nm to 1100 nm. SEM and surface profiler showed that surface morphology of darkening areas consisted of large number of micron scale cauliflower-like clusters and protruding particles. EDS and XPS showed that compared to non-irradiated area, oxygen content at the darkening areas increased significantly. It was proposed a mechanism that involved trapping of light in the surface morphology and chemistry variation of irradiated areas to explain the laser-induced darkening effect on AZ31B Mg alloy.

  8. Reflective variable optical attenuators and fibre ring lasers for wavelength-division multiplexing systems

    Science.gov (United States)

    Liu, He Liang

    Wavelength division multiplexing (WDM) optical fibre system is an important enabling technology to fulfill the demands for bandwidth in the modern information age. The main objective of this project is to study novel devices with the potential to enhance the performance of WDM systems. In particular, a novel reflective variable optical attenuator (RVOA) used for dynamic gain equalization (DGE) and fibre lasers based on an entirely new type of erbium-doped fibres with ultrawide tuning range were investigated theoretically and experimentally. We proposed a new type of RVOA device which could be potentially integrated with arrayed waveguide grating (AWG) to reduce the cost of DGE substantially. Initially, fibre-based RVOAs, fabricated with optical fibre components such as fibre coupler and Faraday rotator mirror, were investigated theoretically and experimentally. Larger attenuation range up to 22 dB was realized for fibre coupler-based ROVA with a Faraday rotator mirror and its polarization-dependent loss is about 0.5 dB. Then polymeric waveguide-based RVOAs were investigated theoretically and experimentally. Using an epoxy Novolak resin as core material and an UV-cured resin (Norland's NOA61) as cladding material, a polymeric waveguide RVOA was successfully fabricated. The dynamic 15 dB attenuation range was achieved and the PDL was less than 0.2 dB. The measured insertion loss of the polymeric waveguide RVOA was too large (about 18 dB) and was mainly induced by coupling loss, material loss and poor alignment. In the second part of the study, fibre ring lasers with continuous wavelength tuning over wide wavelength range and fibre ring lasers with discrete wavelength tuning were investigated. Tunable lasers are important devices in WDM systems because they could be employed as reserved sources and therefore avoiding the need to stock large inventory of lasers to cover the ITU-wavelength grid. In this project, erbium ions doped bismuth oxide glass fibres instead of

  9. Laser surface alloying of aluminium-transition metal alloys

    Directory of Open Access Journals (Sweden)

    Almeida, A.

    1998-04-01

    Full Text Available Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM alloys. Cr and Mo are particularly interesting alloying elements to produce stable highstrength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO2 laser. This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloys, over the last years.

    En el presente trabajo se estudia la aleación superficial mediante láser de aluminio con metales de transición. El cromo y el molibdeno son particularmente interesantes porque producen aleaciones de alta resistencia y por el bajo coeficiente de difusión y solución sólida en aluminio. Para producir estas aleaciones se ha seguido un procedimiento desarrollado en dos partes. En primer lugar, el material se alea usando una baja velocidad de procesado y en segundo lugar la estructura se modifica mediante un refinamiento posterior. Este procedimiento se ha empleado en la producción de aleaciones Al-Cr, Al-Mo y Al-Nb mediante aleación con láser de CO2 de polvos de Cr, Mo o Nb en aluminio y la aleación 7175. Este trabajo es una revisión del desarrollado en el Instituto Superior Técnico de Lisboa en los últimos años.

  10. Surface contamination of the LIL optical components and their evolution after laser irradiation (1. series of experiments); La pollution surfacique de la LIL et son evolution sur un composant optique soumis a une irradiation laser (1. serie d'experiences)

    Energy Technology Data Exchange (ETDEWEB)

    Palmier, St.; Garcia, S.; Lamaignere, L.; Manac' h, P.; Rullier, J.L.; Tovena, I

    2006-07-01

    In the context of the Laser Megajoule project, a study has been carried out to observe the correlation between particle contamination at the surface of the optical components and laser irradiation. The experiments consist in placing silica samples in the Ligne d'Integration Laser (LIL) environment more precisely around the frequency conversion crystals and beam focusing area. Particle contamination at the surface samples is characterized and quantified. Then its behaviour under 1064 nm laser irradiation is observed. From the results of this first series of experiments, it appears that on irradiated silica samples treated with anti reflection coatings, surface particles or contamination can induce a surface defect. (author)

  11. Reflection of femtosecond pulses from soft X-ray free-electron laser by periodical multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ksenzov, D.; Grigorian, S.; Pietsch, U. [Faculty of Physics, University of Siegen (Germany); Hendel, S.; Bienert, F.; Sacher, M.D.; Heinzmann, U. [Faculty of Physics, University of Bielefeld (Germany)

    2009-08-15

    Recent experiments on a soft X-ray free-electron laser (FEL) source (FLASH in Hamburg) have shown that multilayers (MLs) can be used as optical elements for highly intense X-ray irradiation. An effort to find most appropriate MLs has to consider the femtosecond time structure and the particular photon energy of the FEL. In this paper we have analysed the time response of 'low absorbing' MLs (e.g. such as La/B{sub 4}C) as a function of the number of periods. Interaction of a pulse train of Gaussian shaped sub-pulses using a realistic ML grown by electron-beam evaporation technique has been analysed in the soft-X-ray range. The structural parameters of the MLs were obtained by reflectivity measurements at BESSY II and subsequent profile fittings. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  12. Injection current minimization of InAs/InGaAs quantum dot laser by optimization of its active region and reflectivity of laser cavity edges

    International Nuclear Information System (INIS)

    Korenev, V V; Savelyev, A V; Zhukov, A E; Maximov, M V

    2015-01-01

    The ways to optimize key parameters of active region and edge reflectivity of edge- emitting semiconductor quantum dot laser are provided. It is shown that in the case of optimal cavity length and sufficiently large dispersion lasing spectrum of a given width can be obtained at injection current up to an order of magnitude lower in comparison to non-optimized sample. The influence of internal loss and edge reflection is also studied in details. (paper)

  13. Injection current minimization of InAs/InGaAs quantum dot laser by optimization of its active region and reflectivity of laser cavity edges

    Science.gov (United States)

    Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Maximov, M. V.

    2015-11-01

    The ways to optimize key parameters of active region and edge reflectivity of edge- emitting semiconductor quantum dot laser are provided. It is shown that in the case of optimal cavity length and sufficiently large dispersion lasing spectrum of a given width can be obtained at injection current up to an order of magnitude lower in comparison to non-optimized sample. The influence of internal loss and edge reflection is also studied in details.

  14. Corrosion behaviour of laser surface melted magnesium alloy AZ91D

    International Nuclear Information System (INIS)

    Taltavull, C.; Torres, B.; Lopez, A.J.; Rodrigo, P.; Otero, E.; Atrens, A.; Rams, J.

    2014-01-01

    A high power diode laser (HPDL) was used to produce laser surface melting (LSM) treatments on the surface of the Mg alloy AZ91D. Different treatments with different microstructures were produced by varying the laser-beam power and laser-scanning speed. Corrosion evaluation, using hydrogen evolution and electrochemical measurements, led to a relationship between microstructure and corrosion. Most corrosion rates for LSM treated specimens were within the scatter of the as-received AZ91D, whereas some treatments gave higher corrosion rates and some of the samples had corrosion rates lower than the average of the corrosion rate for AZ91D. There were differences in corroded surface morphology. Nevertheless laser treatments introduced surface discontinuities, which masked the effect of the microstructure. Removing these surface defects decreased the corrosion rate for the laser-treated samples. - Highlights: • Corrosion behavior of AZ91D Mg alloys is intimately related with its microstructure. • Laser surface melting treatments allows surface modification of the microstructure. • Different laser parameters can achieve different microstructures. • Controlling laser parameters can produce different corrosion rates and morphologies. • Increase of surface roughness due to laser treatment is relevant to the corrosion rate

  15. Characterization of hydrogel microstructure using laser tweezers particle tracking and confocal reflection imaging

    International Nuclear Information System (INIS)

    Kotlarchyk, M A; Botvinick, E L; Putnam, A J

    2010-01-01

    Hydrogels are commonly used as extracellular matrix mimetics for applications in tissue engineering and increasingly as cell culture platforms with which to study the influence of biophysical and biochemical cues on cell function in 3D. In recent years, a significant number of studies have focused on linking substrate mechanical properties to cell function using standard methodologies to characterize the bulk mechanical properties of the hydrogel substrates. However, current understanding of the correlations between the microstructural mechanical properties of hydrogels and cell function in 3D is poor, in part because of a lack of appropriate techniques. Here we have utilized a laser tracking system, based on passive optical microrheology instrumentation, to characterize the microstructure of viscoelastic fibrin clots. Trajectories and mean square displacements were observed as bioinert PEGylated (PEG: polyethylene glycol) microspheres (1, 2 or 4.7 μm in diameter) diffused within confined pores created by the protein phase of fibrin hydrogels. Complementary confocal reflection imaging revealed microstructures comprised of a highly heterogeneous fibrin network with a wide range of pore sizes. As the protein concentration of fibrin gels was increased, our quantitative laser tracking measurements showed a corresponding decrease in particle mean square displacements with greater resolution and sensitivity than conventional imaging techniques. This platform-independent method will enable a more complete understanding of how changes in substrate mechanical properties simultaneously influence other microenvironmental parameters in 3D cultures.

  16. Higher order structure analysis of nano-materials by spectral reflectance of laser-plasma soft x-ray

    International Nuclear Information System (INIS)

    Azuma, Hirozumi; Takeichi, Akihiro; Noda, Shoji

    1995-01-01

    We have proposed a new experimental arrangement to measure spectral reflectance of nano-materials for analyzing higher order structure with laser-plasma soft x-rays. Structure modification of annealed Mo/Si multilayers and a nylon-6/clay hybrid with poor periodicity was investigated. The measurement of the spectral reflectance of soft x-rays from laser-produced plasma was found to be a useful method for the structure analysis of nano-materials, especially those of rather poor periodicity

  17. Estimates of radiance reflected towards the zenith at the surface of the sea

    Directory of Open Access Journals (Sweden)

    E. Aas

    2010-10-01

    Full Text Available Remote sensing of water colour by ship-mounted sensors represents an important tool for the validation of satellite products and the monitoring of water quality. The recorded radiance from the sea has to be corrected for the surface-reflected radiance from sun and sky in order to obtain the water-leaving radiance. Here the simple case of radiance reflected towards the zenith is studied. A set of observed sky radiance and solar irradiance data from Oslo has been used together with a Gaussian slope distribution for the sea surface in order to estimate the reflected radiance. The spectral range studied is 405–650 nm, the solar zenith angles are in the range 37°–76°, and the wind speeds are up to 10 m s−1. The analysis of the results show that the reflected radiance has to be separated into three contributions: sky radiance and sun rays reflected at the foam-free surface and irradiance reflected by whitecaps and foam. It is then demonstrated that by using four input values, namely the downward irradiance, the sky radiance from the zenith, the solar zenith angle and the wind speed, it is possible to obtain by simple expressions estimates of the reflected radiance that only differ from the former calculated values by relative errors of less than 5%. The analysis also indicates that for the spectral range studied neither the water-leaving radiance nor the surface-reflected radiance can be disregarded relative to the other one in the Case 2 waters of the Oslofjord-Skagerrak area. The results form a first step towards the study of reflected radiance in viewing angles differing from the nadir direction.

  18. More on analyzing the reflection of a laser beam by a deformed highly reflective volume Bragg grating using iteration of the beam propagation method.

    Science.gov (United States)

    Shu, Hong; Mokhov, Sergiy; Zeldovich, Boris Ya; Bass, Michael

    2009-01-01

    A further extension of the iteration method for beam propagation calculation is presented that can be applied for volume Bragg gratings (VBGs) with extremely large grating strength. A reformulation of the beam propagation formulation is presented for analyzing the reflection of a laser beam by a deformed VBG. These methods will be shown to be very accurate and efficient. A VBG with generic z-dependent distortion has been analyzed using these methods.

  19. Coupled thermo-elastic and optical performance analyses of a reflective baffle for the BepiColombo laser altimeter (BELA) receiver

    Science.gov (United States)

    Heesel, E.; Weigel, T.; Lochmatter, P.; Rugi Grond, E.

    2017-11-01

    For the BepiColombo mission, the extreme thermal environment around Mercury requires good heat shields for the instruments. The BepiColombo Laser altimeter (BELA) Receiver will be equipped with a specular reflective baffle in order to limit the solar power impact. The design uses a Stavroudis geometry with alternating elliptical and hyperbolic vanes to reflect radiation at angles >38° back into space. The thermal loads on the baffle lead to deformations, and the resulting changes in the optical performance can be modeled by ray-tracing. Conventional interfaces, such as Zernike surface fitting, fail to provide a proper import of the mechanical distortions into optical models. We have studied alternative models such as free form surface representations and compared them to a simple modeling approach with straight segments. The performance merit is presented in terms of the power rejection ratio and the absence of specular stray-light.

  20. [Effects of Nd: YAG laser irradiation on the root surfaces and adhesion of Streptococcus mutans].

    Science.gov (United States)

    Yuanhong, Li; Zhongcheng, Li; Mengqi, Luo; Daonan, Shen; Shu, Zhang; Shu, Meng

    2016-12-01

    This study aimed to evaluate the effects of treatment with different powers of Nd: YAG laser irradiation on root surfaces and Streptococcus mutans (S. mutans) adhesion. Extracted teeth because of severe periodontal disease were divided into the following four groups: control group, laser group 1, laser group 2, and laser group 3. After scaling and root planning, laser group 1, laser group 2, and laser group 3 were separately treated with Nd: YAG laser irradiation (4/6/8 W, 60 s); however, the control group did not receive the treatment. Scanning electron microscopy (SEM) was used to determine the morphology. S. mutans were cultured with root slices from each group. Colony forming unit per mL (CFU·mL⁻¹) was used to count and compare the amounts of bacteria adhesion among groups. SEM was used to observe the difference of bacteria adhesion to root surfaces between control group (scaling) and laser group 2 (6 W, 60 s), thereby indicating the different bacteria adhesions because of different treatments. Morphology alterations indicated that root surfaces in control group contain obvious smear layer, debris, and biofilm; whereas the root surfaces in laser group contain more cracks with less smear layer and debris. The bacteria counting indicated that S. mutans adhesion to laser group was weaker than that of control group (P0.05) was observed. Morphology alterations also verified that S. mutans adhesion to laser group 2 (6 W, 60 s) was weaker than that of control group (scaling). This study demonstrated that Nd: YAG laser irradiation treatment after scaling can reduce smear layer, debris, and biofilm on the root surfaces as compared with conventional scaling. The laser treatment reduces the adhesion of S. mutans as well. However, Nd: YAG laser irradiation can cause cracks on the root surfaces. In this experiment, the optimum laser power of 6 W can thoroughly remove the smear layer and debris, as well as relatively improve the control of thermal damagee.

  1. An attemp to use a pulsed CO2 laser for decontamination of radioactive metal surfaces

    OpenAIRE

    MILAN S. TRTICA; SCEPAN S. MILJANIC; NATASA N. STJEPANOVIC

    2000-01-01

    There is a growing interest in laser radioactive decontamination of metal surfaces. It offers advantages over conventional methods: improved safety, reduction of secondary waste, reduced waste volume, acceptable cost. The main mechanism of cleaning by lasers is ablation. A pulsed TEA CO2 laser was used in this work for surface cleaning in order to show that ablation of metal surfaces is possible even at relatively low pulse energies, and to suggest that it could be competitive with other lase...

  2. Iterative discrete ordinates solution of the equation for surface-reflected radiance

    Science.gov (United States)

    Radkevich, Alexander

    2017-11-01

    This paper presents a new method of numerical solution of the integral equation for the radiance reflected from an anisotropic surface. The equation relates the radiance at the surface level with BRDF and solutions of the standard radiative transfer problems for a slab with no reflection on its surfaces. It is also shown that the kernel of the equation satisfies the condition of the existence of a unique solution and the convergence of the successive approximations to that solution. The developed method features two basic steps: discretization on a 2D quadrature, and solving the resulting system of algebraic equations with successive over-relaxation method based on the Gauss-Seidel iterative process. Presented numerical examples show good coincidence between the surface-reflected radiance obtained with DISORT and the proposed method. Analysis of contributions of the direct and diffuse (but not yet reflected) parts of the downward radiance to the total solution is performed. Together, they represent a very good initial guess for the iterative process. This fact ensures fast convergence. The numerical evidence is given that the fastest convergence occurs with the relaxation parameter of 1 (no relaxation). An integral equation for BRDF is derived as inversion of the original equation. The potential of this new equation for BRDF retrievals is analyzed. The approach is found not viable as the BRDF equation appears to be an ill-posed problem, and it requires knowledge the surface-reflected radiance on the entire domain of both Sun and viewing zenith angles.

  3. Characteristics of laser textured silicon surface and effect of mud adhesion on hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [ME Department, King Fahd University of Petroleum & Minerals, Kfupm box 1913, Dhahran 31261 (Saudi Arabia); Ali, H. [ME Department, King Fahd University of Petroleum & Minerals, Kfupm box 1913, Dhahran 31261 (Saudi Arabia); Khaled, M. [CHEM Department, King Fahd University of Petroleum & Minerals, Dhahran (Saudi Arabia); Al-Aqeeli, N.; Abu-Dheir, N. [ME Department, King Fahd University of Petroleum & Minerals, Kfupm box 1913, Dhahran 31261 (Saudi Arabia); Varanasi, K.K. [Mechanical Engineering, Massachusetts Institute of Technology, Boston, MA (United States)

    2015-10-01

    Highlights: • Laser treatment increases surface microhardness and slightly lowers surface fracture toughness. • Residual stress formed is compressive and self-annealing effect of laser tracks lowers residual stress. • Nitride species lowers surface energy and adhesion work required to remove dust. • Mud residues do not have notable effect on fracture toughness and microhardness of treated surface. • Mud residues lower surface hydrophobicity. - Abstract: Laser gas assisted texturing of silicon wafer surface is carried out. Morphological and metallurgical changes in the treated layer are examined using the analytical tools. Microhardness and fracture toughness of the laser treated surface are measured using the indentation technique while residual stress formed is determined from the X-ray diffraction data. The hydrophobicity of the textured surfaces are assessed incorporating the contact angle data and compared with those of as received workpiece surfaces. Environmental dust accumulation and mud formation, due to air humidity, at the laser treated and as received workpiece surfaces are simulated and the effect of the mud residues on the properties of the laser treated surface are studied. The adhesion work due to the presence of the mud on the laser treated surface is also measured. It is found that laser textured surface composes of micro/nano poles and fibers, which in turn improves the surface hydrophobicity significantly. In addition, formation of nitride species contributes to microhardness increase and enhancement of surface hydrophobicity due to their low surface energy. The mud residues do not influence the fracture toughness and microhardness of the laser textured surface; however, they reduced the surface hydrophobicity significantly.

  4. Laser gas assisted texturing and formation of nitride and oxynitride compounds on alumina surface: Surface response to environmental dust

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Al-Sharafi, A.; Al-Aqeeli, N.

    2018-03-01

    Laser gas assisted texturing of alumina surface is carried out, and formation of nitride and oxynitride compounds in the surface vicinity is examined. The laser parameters are selected to create the surface topology consisting of micro/nano pillars with minimum defect sites including micro-cracks, voids and large size cavities. Morphological and hydrophobic characteristics of the textured surface are examined using the analytical tools. The characteristics of the environmental dust and its influence on the laser textured surface are studied while mimicking the local humid air ambient. Adhesion of the dry mud on the laser textured surface is assessed through the measurement of the tangential force, which is required to remove the dry mud from the surface. It is found that laser texturing gives rise to micro/nano pillars topology and the formation of AlN and AlON compounds in the surface vicinity. This, in turn, lowers the free energy of the textured surface and enhances the hydrophobicity of the surface. The liquid solution resulted from the dissolution of alkaline and alkaline earth metals of the dust particles in water condensate forms locally scattered liquid islands at the interface of mud and textured surface. The dried liquid solution at the interface increases the dry mud adhesion on the textured surface. Some dry mud residues remain on the textured surface after the dry mud is removed by a pressurized desalinated water jet.

  5. Measurement of integrated coefficients of ultracold neutron reflection from solid surfaces

    International Nuclear Information System (INIS)

    Golikov, V.V.; Kulagin, E.N.; Nikitenko, Yu.V.

    1985-01-01

    The method of measurement of the integrated coefficients of ultracold neutrons (UCN) reflection from solid surfaces is reported. A simple formula is suggested which expresses the integrated coefficients of UCN reflection from a given sample through the measured counting rate of the detector with and without strong absorber (polyethelene). The parameters are determined describing anisotropic and inhomogeneity properties of UCN reflection from Al, Mg, Pb, Zn, Mo, stainless steel, T and V are measured. The thickness of oxide layers is determined within the 5-10A accuracy limits from the experimental coefficients of UCN reflection from metals having on their surfaces the oxides with boundary velocity larger than that for the metal. It has been determined that the density of 5000 A layer of heavy ice freezed on aluminium is 0.83 +- 0.05 from the crystal ice density

  6. Manifestation of surface phonons in far infrared reflectivity of diamond-type semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Sanchez, F.L.; Perez-Rodriguez, F. [Instituto de Fisica, Universidad Autonoma de Puebla, Apdo. Post. J-48, Puebla, Pue. 72570 (Mexico)

    2004-11-01

    The coupling of surface phonons with light at (001) surfaces of diamond-structure crystals and its manifestation in far-infrared anisotropy spectra are theoretically studied. We apply the adiabatic bond charge model to describe short-range mechanical interactions together with long-range Coulomb forces and radiation fields, and we solve the corresponding system of coupled equations for the electromagnetic field and the lattice vibrations. We calculate far-infrared normal reflectance spectra of (001) surfaces of semi-infinite diamond-type crystals. In particular, we analyse reflectance spectra for the Si(001) (2 x 1) surface, which exhibit a resonance structure associated with the excitation of surface phonon modes. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Laser surface alloying of 316L stainless steel with Ru and Ni mixtures

    CSIR Research Space (South Africa)

    Lekala, MB

    2012-05-01

    Full Text Available an economically sound approach of modifying corrosion properties of alloys. Furthermore, since corrosion is a surface phenomenon, an equally cost-effective approach is to add these only on the surface, where protection is most required. Laser surface... powders were preplaced on the steel surface using a chemical binder. The thickness of the preplaced powder coatings could be controlled to approxi- mately 1mm. The laser surface alloying was performed with a Rofin Sinar DY044 continuous wave Nd : YAG...

  8. Effect of surface-breakdown plasma on metal drilling by pulsed CO2-laser radiation

    Science.gov (United States)

    Arutiunian, P. V.; Baranov, V. Iu.; Bobkov, I. V.; Bol'Shakov, L. A.; Dolgov, V. A.

    1988-03-01

    The effect of low-threshold surface breakdown produced by short (5-microsec) CO2-laser pulses on the metal drilling process is investigated. Data on the interaction of metals with laser pulses having the same duration but different shape are shown to be different. The effect of the ambient atmospheric pressure on the laser drilling process is investigated.

  9. Ultra short pulse laser generated surface textures for anti-ice applications in aviation

    NARCIS (Netherlands)

    Römer, G.W.; Del Cerro, D.A.; Sipkema, R.C.J.; Groenendijk, M.N.W.; Huis in 't Veld, A.J.

    2009-01-01

    By laser ablation with ultra short laser pulses in the pico- and femto-second range, well controlled dual scaled micro- and nano-scaled surface textures can be obtained. The micro-scale of the texture is mainly determined by the dimensions of the laser spot, whereas the superimposed nano-structure

  10. Developmental prosopagnosia and super-recognition: no special role for surface reflectance processing.

    Science.gov (United States)

    Russell, Richard; Chatterjee, Garga; Nakayama, Ken

    2012-01-01

    Face recognition by normal subjects depends in roughly equal proportions on shape and surface reflectance cues, while object recognition depends predominantly on shape cues. It is possible that developmental prosopagnosics are deficient not in their ability to recognize faces per se, but rather in their ability to use reflectance cues. Similarly, super-recognizers' exceptional ability with face recognition may be a result of superior surface reflectance perception and memory. We tested this possibility by administering tests of face perception and face recognition in which only shape or reflectance cues are available to developmental prosopagnosics, super-recognizers, and control subjects. Face recognition ability and the relative use of shape and pigmentation were unrelated in all the tests. Subjects who were better at using shape or reflectance cues were also better at using the other type of cue. These results do not support the proposal that variation in surface reflectance perception ability is the underlying cause of variation in face recognition ability. Instead, these findings support the idea that face recognition ability is related to neural circuits using representations that integrate shape and pigmentation information. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Assessment of biases in MODIS surface reflectance due to Lambertian approximation

    Energy Technology Data Exchange (ETDEWEB)

    Cook, Robert B [ORNL; SanthanaVannan, Suresh K [ORNL

    2010-08-01

    Using MODIS data and the AERONET-based Surface Reflectance Validation Network (ASRVN), this work studies errors of MODIS atmospheric correction caused by the Lambertian approximation. On one hand, this approximation greatly simplifies the radiative transfer model, reduces the size of the look-up tables, and makes operational algorithm faster. On the other hand, uncompensated atmospheric scattering caused by Lambertian model systematically biases the results. For example, for a typical bowl-shaped bidirectional reflectance distribution function (BRDF), the derived reflectance is underestimated at high solar or view zenith angles, where BRDF is high, and is overestimated at low zenith angles where BRDF is low. The magnitude of biases grows with the amount of scattering in the atmosphere, i.e., at shorter wavelengths and at higher aerosol concentration. The slope of regression of Lambertian surface reflectance vs. ASRVN bidirectional reflectance factor (BRF) is about 0.85 in the red and 0.6 in the green bands. This error propagates into the MODIS BRDF/albedo algorithm, slightly reducing the magnitude of overall reflectance and anisotropy of BRDF. This results in a small negative bias of spectral surface albedo. An assessment for the GSFC (Greenbelt, USA) validation site shows the albedo reduction by 0.004 in the near infrared, 0.005 in the red, and 0.008 in the green MODIS bands.

  12. Comparison of cloud optical depth and cloud mask applying BRDF model-based background surface reflectance

    Science.gov (United States)

    Kim, H. W.; Yeom, J. M.; Woo, S. H.

    2017-12-01

    Over the thin cloud region, satellite can simultaneously detect the reflectance from thin clouds and land surface. Since the mixed reflectance is not the exact cloud information, the background surface reflectance should be eliminated to accurately distinguish thin cloud such as cirrus. In the previous research, Kim et al (2017) was developed the cloud masking algorithm using the Geostationary Ocean Color Imager (GOCI), which is one of significant instruments for Communication, Ocean, and Meteorology Satellite (COMS). Although GOCI has 8 spectral channels including visible and near infra-red spectral ranges, the cloud masking has quantitatively reasonable result when comparing with MODIS cloud mask (Collection 6 MYD35). Especially, we noticed that this cloud masking algorithm is more specialized in thin cloud detections through the validation with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data. Because this cloud masking method was concentrated on eliminating background surface effects from the top-of-atmosphere (TOA) reflectance. Applying the difference between TOA reflectance and the bi-directional reflectance distribution function (BRDF) model-based background surface reflectance, cloud areas both thick cloud and thin cloud can be discriminated without infra-red channels which were mostly used for detecting clouds. Moreover, when the cloud mask result was utilized as the input data when simulating BRDF model and the optimized BRDF model-based surface reflectance was used for the optimized cloud masking, the probability of detection (POD) has higher value than POD of the original cloud mask. In this study, we examine the correlation between cloud optical depth (COD) and its cloud mask result. Cloud optical depths mostly depend on the cloud thickness, the characteristic of contents, and the size of cloud contents. COD ranges from less than 0.1 for thin clouds to over 1000 for the huge cumulus due to scattering by droplets. With

  13. Reduction of secondary electron yield for E-cloud mitigation by laser ablation surface engineering

    Energy Technology Data Exchange (ETDEWEB)

    Valizadeh, R., E-mail: reza.valizadeh@stfc.ac.uk [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Malyshev, O.B. [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Wang, S. [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Department of Physics, Loughborough University, Loughborough LE11 3TU (United Kingdom); Sian, T. [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); The Photon Science Institute, The University of Manchester, Manchester M13 9PL (United Kingdom); Cropper, M.D. [Department of Physics, Loughborough University, Loughborough LE11 3TU (United Kingdom); Sykes, N. [Micronanics Ltd., Didcot, Oxon OX11 0QX (United Kingdom)

    2017-05-15

    Highlights: • SEY below 1 can be achieved with Laser ablation surface engineering. • SEY <1 surface can be produced with different types of nanosecond lasers. • Both microstructure (groves) and nano-structures are playing a role in reducing SEY. - Abstract: Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators. In our previous publications, a low SEY < 0.9 for as-received metal surfaces modified by a nanosecond pulsed laser was reported. In this paper, the SEY of laser-treated blackened copper has been investigated as a function of different laser irradiation parameters. We explore and study the influence of micro- and nano-structures induced by laser surface treatment in air of copper samples as a function of various laser irradiation parameters such as peak power, laser wavelength (λ = 355 nm and 1064 nm), number of pulses per point (scan speed and repetition rate) and fluence, on the SEY. The surface chemical composition was determined by x-ray photoelectron spectroscopy (XPS) which revealed that heating resulted in diffusion of oxygen into the bulk and induced the transformation of CuO to sub-stoichiometric oxide. The surface topography was examined with high resolution scanning electron microscopy (HRSEM) which showed that the laser-treated surfaces are dominated by microstructure grooves and nanostructure features.

  14. Surface reflectance of Antarctic bryophytes and protection from UV and visible light

    International Nuclear Information System (INIS)

    Robinson, S.A.; Wasley, J.; Turnbull, J.

    2000-01-01

    Full text: As well as determining the amount of solar radiation available for photosynthesis, the surface reflectance and absorptance characteristics of plants are their first defence against damaging effects of solar radiation. The solar spectrum can be damaging to plants in many ways. At shorter wavelengths, UV-B (280-320 nm) radiation can cause lesions in nucleic acid and proteins. Excess levels of visible radiation (400-750) can cause photoinhibition whilst high absorbtance of longer wavelengths (>750) leads to increases in temperature that can be detrimental in some environments. The adaptation of surface reflectance properties of vascular plants to particular environments are well known in some ecosystems. For example in desert ecosystems pubescent leaf surfaces that increase reflectance are common and have been demonstrated to be important to protection from photoinhibition. The epidermal characteristics of some plants are also known to change in absorptance, due to the accumulation of specific compounds. For example flavonoids which are effective screens against UV-B radiation, increase upon exposure to UV-B radiation. In this study we surveyed the natural variability in surface reflectance in mosses growing in continental Antarctica. Antarctica is experiencing large increases in incident UV-B radiation due to reductions in concentrations of stratospheric ozone. Additionally over the summer months (November January), when moss is exposed to direct sunlight, levels of visible solar radiation are also high, increasing the likelihood of photoinhibitory damage in moss. Our aim in this study is to describe the natural variability in the surface reflectance characteristics of moss, such that we have a baseline with which to assess future changes in response to changes in global climate, and imposed experimental treatments, and also to develop hypotheses with respect to how mosses have adapted to the cold and arid antarctic environment. Variability in surface

  15. Influence of Aerosols And Surface Reflectance On NO2 Retrieval Over China From 2005 to 2015

    Science.gov (United States)

    Liu, M.; Lin, J.

    2016-12-01

    Satellite observation is a powerful way to analysis annual and seasonal variations of nitrogen dioxide (NO2). However, much retrieval of vertical column densities (VCDs) of normally do not explicitly account for aerosol optical effects and surface reflectance anisotropy that vary with space and time. In traditional retrieval, aerosols' effects are often considered as cloud. However, China has complicated aerosols type and aerosol loading. Their optical properties may be very different from the cloud. Furthermore, China has undergone big changes in land use type in recent 10 years. Traditional climatology surface reflectance data may not have representation. In order to study spatial-temporal variation of and influences of these two factors on variations and trends, we use an improved retrieval method of VCDs over China, called the POMINO, based on measurements from the Ozone Monitoring Instrument (OMI), and we compare the results of without aerosol, without surface reflectance treatments and without both to the original POMINO product from 2005 to 2015. Furthermore, we will study correspondent spatial-temporal variations of aerosols, represented by MODIS aerosol optical depth (AOD) data and CALIOP extinction data; surface reflectance, represented by MODIS bidirectional reflectance distribution function (BRDF) data.

  16. The final status of a metal surface after multipulse laser irradiation in an ambient gas

    International Nuclear Information System (INIS)

    Boulmer Leborgne, C.; Hermann, J.; Dubreuil, B.

    1993-11-01

    We have investigated the role of the ambient gas nature and pressure, and the influence of the laser pulse total duration and temporal shape in the coupling of the incident laser light of λ = 10.6μm wavelength to a metallic surface at intermediate laser intensities of 10 7 - 10 8 W/cm 2 . A plasma is accompanying then the action of the laser pulse. It is acting as an active moderator among laser beam and target thus determining the final status of the contact surface. (author). 11 refs, 6 figs

  17. Laser generation of nanostructures on the surface and in the bulk of solids

    International Nuclear Information System (INIS)

    Bityurin, N M

    2010-01-01

    This paper considers nanostructuring of solid surfaces by nano-optical techniques, primarily by laser particle nanolithography. Threshold processes are examined that can be used for laser structuring of solid surfaces, with particular attention to laser swelling of materials. Fundamental spatial resolution issues in three-dimensional (3D) laser nanostructuring are analysed with application to laser nanopolymerisation and 3D optical information recording. The formation of nanostructures in the bulk of solids due to their structural instability under irradiation is exemplified by photoinduced formation of nanocomposites. (photonics and nanotechnology)

  18. Multiple Reflections and Fresnel Absorption of Gaussian Laser Beam in an Actual 3D Keyhole during Deep-Penetration Laser Welding

    Directory of Open Access Journals (Sweden)

    Xiangzhong Jin

    2012-01-01

    Full Text Available In deep penetration laser welding, a keyhole is formed in the material. Based on an experimentally obtained bending keyhole from low- and medium-speed laser penetration welding of glass, the keyhole profiles in both the symmetric plane are determined by polynomial fitting. Then, a 3D bending keyhole is reconstructed under the assumption of circular cross-section of the keyhole at each keyhole depth. In this paper, the behavior of focused Gaussian laser beam in the keyhole is analyzed by tracing a ray of light using Gaussian optics theory, the Fresnel absorption and multiple reflections in the keyhole are systematically studied, and the laser intensities absorbed on the keyhole walls are calculated. Finally, the formation mechanism of the keyhole is deduced.

  19. LASER INDUCED SELECTIVE ACTIVATION UTILIZING AUTO-CATALYTIC ELECTROLESS PLATING ON POLYMER SURFACE

    DEFF Research Database (Denmark)

    Zhang, Yang; Nielsen, Jakob Skov; Tang, Peter Torben

    2009-01-01

    . Characterization of the deposited copper layer was used to select and improve laser parameters. Several types of polymers with different melting points were used as substrate. Using the above mentioned laser treatment, standard grades of thermoplastic materials such as ABS, SAN, PE, PC and others have been......This paper presents a new method for selective micro metallization of polymers induced by laser. An Nd: YAG laser was employed to draw patterns on polymer surfaces using a special set-up. After subsequent activation and auto-catalytic electroless plating, copper only deposited on the laser tracks....... Induced by the laser, porous and rough structures are formed on the surface, which favours the palladium attachment during the activation step prior to the metallization. Laser focus detection, scanning electron microscopy (SEM) and other instruments were used to analyze the topography of the laser track...

  20. Research on Laser Micro Polishing of SLS Technology Sintered Iron-Based Powder Surface

    Directory of Open Access Journals (Sweden)

    Gerda Vaitkūnaitė

    2015-03-01

    Full Text Available The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treated and untreated areas of the material has been made.

  1. A new laser reflectance system capable of measuring changing cross-sectional area of soft tissues during tensile testing.

    Science.gov (United States)

    Pokhai, Gabriel G; Oliver, Michele L; Gordon, Karen D

    2009-09-01

    Determination of the biomechanical properties of soft tissues such as tendons and ligaments is dependent on the accurate measurement of their cross-sectional area (CSA). Measurement methods, which involve contact with the specimen, are problematic because soft tissues are easily deformed. Noncontact measurement methods are preferable in this regard, but may experience difficulty in dealing with the complex cross-sectional shapes and glistening surfaces seen in soft tissues. Additionally, existing CSA measurement systems are separated from the materials testing machine, resulting in the inability to measure CSA during testing. Furthermore, CSA measurements are usually made in a different orientation, and with a different preload, prior to testing. To overcome these problems, a noncontact laser reflectance system (LRS) was developed. Designed to fit in an Instron 8872 servohydraulic test machine, the system measures CSA by orbiting a laser transducer in a circular path around a soft tissue specimen held by tissue clamps. CSA measurements can be conducted before and during tensile testing. The system was validated using machined metallic specimens of various shapes and sizes, as well as different sizes of bovine tendons. The metallic specimens could be measured to within 4% accuracy, and the tendons to within an average error of 4.3%. Statistical analyses showed no significant differences between the measurements of the LRS and those of the casting method, an established measurement technique. The LRS was successfully used to measure the changing CSA of bovine tendons during uniaxial tensile testing. The LRS developed in this work represents a simple, quick, and accurate way of reconstructing complex cross-sectional profiles and calculating cross-sectional areas. In addition, the LRS represents the first system capable of automatically measuring changing CSA of soft tissues during tensile testing, facilitating the calculation of more accurate biomechanical properties.

  2. Laser cleaning of the contaminations on the surface of tire mould

    Science.gov (United States)

    Ye, Yayun; Jia, Baoshen; Chen, Jing; Jiang, Yilan; Tang, Hongping; Wang, Haijun; Luan, Xiaoyu; Liao, Wei; Zhang, Chuanchao; Yao, Caizhen

    2017-07-01

    During the manufacturing of tires, surface pollutants on tire mould will lead to the production of unqualified tires. Tire moulds need to be regularly cleaned. Laser cleaning is recognized as a non-destructive, effective, precise and environmental friendly method. In this paper, laser cleaning was used to remove contaminants on tire mould surface. First, laser induced damage experiments were performed. The results showed that the roughness and hardness of the cast steel sample surface seldom changed under the energy range of 140.1-580.2 mJ laser irradiation 1 pulse and the energy range of 44.7-168.9 mJ laser irradiation 100 pulses. In the laser cleaning experiments, the cleaning thresholds and the optimal cleaning parameters were obtained. Results indicated that laser cleaning was safe and effective for tire mould contamination removal.

  3. Graded Reflectivity Mirror for the Solid State Heat Capacity Laser Final Report CRADA No. TC-2085-04

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Davis, J. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-09-27

    This was a collaborative effort between The Regents of the University of California, Lawrence Livermore National Laboratory (LLNL) and the Boeing Company, to develop a Graded Reflectivity Mirror (GRM) to achieve improved near field fill and higher brightness in the far field output of LLNL’s Solid State Heat Capacity Laser (SSHCL).

  4. Holographic cinematography of time-varying reflecting and time-varying phase objects using a Nd:YAG laser

    Science.gov (United States)

    Decker, A. J.

    1982-01-01

    The use of a Nd:YAG laser to record holographic motion pictures of time-varying reflecting objects and time-varying phase objects is discussed. Sample frames from both types of holographic motion pictures are presented. The holographic system discussed is intended for three-dimensional flow visualization of the time-varying flows that occur in jet-engine components.

  5. Surface plasmon quantum cascade lasers as terahertz local oscillators.

    Science.gov (United States)

    Hajenius, M; Khosropanah, P; Hovenier, J N; Gao, J R; Klapwijk, T M; Barbieri, S; Dhillon, S; Filloux, P; Sirtori, C; Ritchie, D A; Beere, H E

    2008-02-15

    We characterize a heterodyne receiver based on a surface-plasmon waveguide quantum cascade laser (QCL) emitting at 2.84 THz as a local oscillator, and an NbN hot electron bolometer as a mixer. We find that the envelope of the far-field pattern of the QCL is diffraction-limited and superimposed onto interference fringes, which are similar to those found in narrow double-metal waveguide QCLs. Compared to the latter, a more directional beam allows for better coupling of the radiation power to the mixer. We obtain a receiver noise temperature of 1050 K when the mixer is at 2 K, which, to our knowledge, is the highest sensitivity reported at frequencies beyond 2.5 THz.

  6. Gain-Enhanced On-Chip Antenna Utilizing Artificial Magnetic Conductor Reflecting Surface at 94 GHz

    KAUST Repository

    Nafe, Mahmoud

    2015-01-01

    In this work, the use of specially patterned reflecting surfaces for improving on- chip antenna performance is investigated. By using a periodic metallic surface on top of a grounded substrate, the structure can mimic the behavior of a perfect mag- netic conductor, hence called Artificial Magnetic Conductor (AMC) surface. Unlike conventional ground plane reflecting surfaces, AMC surfaces generally enhance the radiation and impedance characteristics of close-by antennas. Based on this property, a ring-based AMC reflecting surface has been designed in the oxide layer for on-chip antennas operating at 94 GHz. Furthermore, a folded dipole antenna with its associ- ated planar feeding structures has been optimized and integrated with the developed ring-based AMC surface. The proposed design is then fabricated at KAUST clean- room facilities. Prototype characterization showed very promising results with good correlation to simulations, with the antenna exhibiting an impedance bandwidth of 10% (90-100 GHz) and peak gain of -1.4 dBi, which is the highest gain reported for on-chip antennas at this frequency band without the use of any external o↵-chip components or post-fabrication steps.

  7. Tunable natural nano-arrays : controlling surface properties and light reflectance

    International Nuclear Information System (INIS)

    Watson, J.A.; Myhra, S.; Cribb, B.W.; Hope, G.A.; Watson, G.S.

    2005-01-01

    A sudden transition or impedance mismatch from one optical medium to another can result in unwanted reflections from the surface plane. Modification of a surface by creation of a gradual change in refractive index over a significant portion of a wavelength range will result in a reduction in reflection. Multi-layered thin film coatings based on this phenomenon are widely used on a number of different surfaces (e.g. solar cells, lenses, display screens etc.) to suppress undesired reflections and/or increase light transmittance. An alternative surface modification to the multi-layered stack coating (gradient index coating) is to produce a surface with structures having a period and heights shorter than the light wavelength. These structures act like a pseudo-gradient index coating and can be described by the effective medium theory. In this study we report on nano-structures (a natural pseudo-gradient index coating) which we have found on certain species of cicada wings demonstrating their reflective effectiveness using manipulative atomic force microscopy. (author). 2 refs., 5 figs

  8. Early Evaluation of the VIIRS Calibration, Cloud Mask and Surface Reflectance Earth Data Records

    Science.gov (United States)

    Vermote, Eric; Justice, Chris; Csiszar, Ivan

    2014-01-01

    Surface reflectance is one of the key products fromVIIRS and as withMODIS, is used in developing several higherorder land products. The VIIRS Surface Reflectance (SR) Intermediate Product (IP) is based on the heritageMODIS Collection 5 product (Vermote, El Saleous, & Justice, 2002). The quality and character of surface reflectance depend on the accuracy of the VIIRS Cloud Mask (VCM), the aerosol algorithms and the adequate calibration of the sensor. The focus of this paper is the early evaluation of the VIIRS SR product in the context of the maturity of the operational processing system, the Interface Data Processing System (IDPS). After a brief introduction, the paper presents the calibration performance and the role of the surface reflectance in calibration monitoring. The analysis of the performance of the cloud mask with a focus on vegetation monitoring (no snow conditions) shows typical problems over bright surfaces and high elevation sites. Also discussed is the performance of the aerosol input used in the atmospheric correction and in particular the artifacts generated by the use of the Navy Aerosol Analysis and Prediction System. Early quantitative results of the performance of the SR product over the AERONET sites showthatwith the fewadjustments recommended, the accuracy iswithin the threshold specifications. The analysis of the adequacy of the SR product (Land PEATE adjusted version) in applications of societal benefits is then presented. We conclude with a set of recommendations to ensure consistency and continuity of the JPSS mission with the MODIS Land Climate Data Record.

  9. Coatings for laser fusion

    International Nuclear Information System (INIS)

    Lowdermilk, W.H.

    1981-01-01

    Optical coatings are used in lasers systems for fusion research to control beam propagation and reduce surface reflection losses. The performance of coatings is important in the design, reliability, energy output, and cost of the laser systems. Significant developments in coating technology are required for future lasers for fusion research and eventual power reactors

  10. Observation on Surface Change of Fragile Glass: Temperature - Time Dependence Studied by X-Ray Reflectivity

    International Nuclear Information System (INIS)

    Kikkawa, Hiroyuki; Kitahara, Amane; Takahashi, Isao

    2004-01-01

    The structural change of a fragile glass surface close to the glass transition temperature Tg is studied by using X-ray reflectivity. Measurements were performed on surfaces of maltitol, which is a typical polyalcohol fragile glass with Tg = 320K. Upon both heating and cooling, we find the following features which are also noticed in silicate glass surfaces: (i) On heating, the surface morphology indicates a variation at temperatures below Tg; (ii) A drastic increase in surface roughness occurs at a temperature about 333K on heating, which is 13K higher than Tg; (iii) During the cooling of the sample, formation of a low-density surface layer (3nm at 293K) is observed. Prior to the crystallization, nm - μm sized domains were grown at the surface, which might not be reported for other glasses

  11. [INVITED] Laser gas assisted treatment of Ti-alloy: Analysis of surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Karatas, C.

    2016-04-01

    Laser gas assisted treatment of Ti6Al4V alloy surface is carried out and nitrogen/oxygen mixture with partial pressure of PO2/PN2=1/3 is introduced during the surface treatment process. Analytical tools are used to characterize the laser treated surfaces. The fracture toughness at the surface and the residual stress in the surface region of the laser treated layer are measured. Scratch tests are carried out to determine the friction coefficient of the treated surface. It is found that closely spaced regular laser scanning tracks generates a self-annealing effect in the laser treated layer while lowering the stress levels in the treated region. Introducing high pressure gas mixture impingement at the surface results in formation of oxide and nitride species including, TiO, TiO2, TiN and TiOxNy in the surface region. A dense layer consisting of fine size grains are formed in the surface region of the laser treated layer, which enhances the microhardness at the surface. The fracture toughness reduces after the laser treatment process because of the microhardness enhancement at the surface. The residual stress formed is comprehensive, which is in the order of -350 MPa.

  12. Solar flux incident on an orbiting surface after reflection from a planet

    Science.gov (United States)

    Modest, M. F.

    1980-01-01

    Algorithms describing the solar radiation impinging on an infinitesimal surface after reflection from a gray and diffuse planet are derived. The following conditions apply: only radiation from the sunny half of the planet is taken into account; the radiation must fall on the top of the orbiting surface, and radiation must come from that part of the planet that can be seen from the orbiting body. A simple approximate formula is presented which displays excellent accuracy for all significant situations, with an error which is always less than 5% of the maximum possible reflected flux. Attention is also given to solar albedo flux on a surface directly facing the planet, the influence of solar position on albedo flux, and to solar albedo flux as a function of the surface-planet tilt angle.

  13. Effect of surface characteristics on diffuse reflection radiation at lambda=0. 40. mu. m

    Energy Technology Data Exchange (ETDEWEB)

    Takashima, T [Atmospheric Environment Service, Downsview, Ontario (Canada)

    1976-08-01

    The diffuse radiation in the upward direction at the top and at an internal level of an inhomogeneous atmosphere is computed at lambda=0.40 ..mu..m. The surface is assumed to reflect light in accordance with a hybrid mode of a diffuse and specular reflector. The objective is to estimate the effect of underlying surface characteristics in terms of the diffuse radiation field. By making use of these results, accuracy in monitoring the atmospheric aerosols would be increased for the use of remote sensing satellite techniques. Junge power law (..gamma..*=3) is adopted for the size distribution of aerosols (1963), while the data given by McClatchy et al. (1971) is used for the number density of aerosols with height distribution. It is noted from the computations that the diffuse reflection radiation is affected by the surface characteristics, even if the albedo of the surface is a fixed constant and very small.

  14. The Effects of Spherical Surface and Laser Polarization on the Photodetachment Cross Section of H−

    International Nuclear Information System (INIS)

    Haneef Muhammad; Arif Suneela; Akbar Jehan; Shamim Aneela; Shah Nasrullah; Zahir Muhammad; Ullah Hameed

    2013-01-01

    We report the combined effects of laser polarization and curvature of the spherical surface on the detached electron spectra from H − . The Theoretical imaging method is used as a tool of investigation. The photodetachment cross sections for various polarization angles, radii of curvatures and inter ion surface distances are displayed. The analysis of the spectra reveals that the laser polarization angle θ L , curvature of the surface r c and inter ion surface distance d strongly affect oscillations in the spectra. Therefore, a fine control on the laser polarization and that of curvature in the surface can be used to control oscillations in the photodetachment of negative ions. (atomic and molecular physics)

  15. IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets

    Data.gov (United States)

    National Aeronautics and Space Administration — The IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets (ILUTP2) data set contains surface range values for Antarctica and Greenland derived...

  16. Spatiotemporal closure of fractional laser-ablated channels imaged by optical coherence tomography and reflectance confocal microscopy

    DEFF Research Database (Denmark)

    Banzhaf, Christina A.; Wind, Bas S.; Mogensen, Mette

    2016-01-01

    Background and Objective Optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) offer high-resolution optical imaging of the skin, which may provide benefit in the context of laser-assisted drug delivery. We aimed to characterize postoperative healing of ablative fractional...... laser (AFXL)-induced channels and dynamics in their spatiotemporal closure using in vivo OCT and RCM techniques. Study design/Materials and Methods The inner forearm of healthy subjects (n = 6) was exposed to 10,600 nm fractional CO2 laser using 5 and 25% densities, 120 μm beam diameter, 5, 15, and 25 m......J/microbeam. Treatment sites were scanned with OCT to evaluate closure of AFXL-channels and RCM to evaluate subsequent re-epithelialization. Results OCT and RCM identified laser channels in epidermis and upper dermis as black, ablated tissue defects surrounded by characteristic hyper-and hyporeflective zones. OCT imaged...

  17. The Photosensitivity of Rhodopsin Bleaching and Light-Induced Increases of Fundus Reflectance in Mice Measured In Vivo With Scanning Laser Ophthalmoscopy

    Science.gov (United States)

    Zhang, Pengfei; Goswami, Mayank; Zawadzki, Robert J.; Pugh, Edward N.

    2016-01-01

    Purpose To quantify bleaching-induced changes in fundus reflectance in the mouse retina. Methods Light reflected from the fundus of albino (Balb/c) and pigmented (C57Bl/6J) mice was measured with a multichannel scanning laser ophthalmoscopy optical coherence tomography (SLO-OCT) optical system. Serial scanning of small retinal regions was used for bleaching rhodopsin and measuring reflectance changes. Results Serial scanning generated a saturating reflectance increase centered at 501 nm with a photosensitivity of 1.4 × 10−8 per molecule μm2 in both strains, 2-fold higher than expected were irradiance at the rod outer segment base equal to that at the retinal surface. The action spectrum of the reflectance increase corresponds to the absorption spectrum of mouse rhodopsin in situ. Spectra obtained before and after bleaching were fitted with a model of fundus reflectance, quantifying contributions from loss of rhodopsin absorption with bleaching, absorption by oxygenated hemoglobin (HbO2) in the choroid (Balb/c), and absorption by melanin (C57Bl/6J). Both mouse strains exhibited light-induced broadband reflectance changes explained as bleaching-induced reflectivity increases at photoreceptor inner segment/outer segment (IS/OS) junctions and OS tips. Conclusions The elevated photosensitivity of rhodopsin bleaching in vivo is explained by waveguide condensing of light in propagation from rod inner segment (RIS) to rod outer segment (ROS). The similar photosensitivity of rhodopsin in the two strains reveals that little light backscattered from the sclera can enter the ROS. The bleaching-induced increases in reflectance at the IS/OS junctions and OS tips resemble results previously reported in human cones, but are ascribed to rods due to their 30/1 predominance over cones in mice and to the relatively minor amount of cone M-opsin in the regions scanned. PMID:27403994

  18. Collective migration of adsorbed atoms on a solid surface in the laser radiation field

    International Nuclear Information System (INIS)

    Andreev, V V; Ignat'ev, D V; Telegin, Gennadii G

    2004-01-01

    The lateral (in the substrate plane) interaction between dipoles induced in particles adsorbed on a solid surface is studied in a comparatively weak laser radiation field with a Gaussian transverse distribution. It is shown that the particles migrate over the surface in the radial direction either outside an illuminated spot with the formation of a 'crater' or inside the spot with the formation of a 'mound'. (interaction of laser radiation with matter. laser plasma)

  19. Laser surface alloying of aluminium with WC+Co+NiCr for improved wear resistance

    CSIR Research Space (South Africa)

    Nath, S

    2012-03-01

    Full Text Available Department of Metallurgical & Materials Engineering, IIT Kharagpur, West Bengal, India 2National Laser Centre, CSIR, Pretoria, South Africa Abstract In the present study, laser surface alloying of aluminium with WC+Co+NiCr (in the ratio of 70... be used for dispersion of ceramic materials into metallic matrix and hence, form a ceramic dispersed metal matrix composite on metallic substrate [3]. The advantages of laser surface alloying include refinement of the microstructure, uniform dispersion...

  20. Near-surface 3D reflections seismic survey; Sanjigen senso hanshaho jishin tansa

    Energy Technology Data Exchange (ETDEWEB)

    Nakahigashi, H; Mitsui, H; Nakano, O; Kobayashi, T [DIA Consultants Co. Ltd., Tokyo (Japan)

    1997-05-27

    Faults are being actively investigated across Japan since the Great Hanshin-Awaji Earthquake. Discussed in this report is the application of the 3D near-surface reflection seismic survey in big cities. Data from trenching and drilling is used for the geological interpretation of the surroundings of a fault, and the reflection seismic survey is used to identify the position, etc., of the fault. In this article, when the results obtained from the experimental field are examined, it is found that the conventional 2D imaging reflection survey betrays the limit of its capability when the geological structure is complicated, that the 3D reflection seismic survey, on the contrary, is capable of high-precision imaging and, when augmented by drilling, etc., becomes capable of a more detailed interpretation, and that it also contributes effectively to the improvement of local disaster prevention in big cities. Using as the model the Tachikawa fault that runs near JR Tachikawa Station, embodiment of the 3D reflection seismic survey is reviewed. For the acquisition of data excellent in quality in a 3D reflection seismic survey conducted utilizing the roads in the sector chosen for experiment in the urban area, the shock generating points and receiving points should be positioned by taking into account the parameters in the bin arranging process so that the mid-points will be regularly distributed on the surface. 3 refs., 11 figs., 1 tab.

  1. Weighted least-square approach for simultaneous measurement of multiple reflective surfaces

    Science.gov (United States)

    Tang, Shouhong; Bills, Richard E.; Freischlad, Klaus

    2007-09-01

    Phase shifting interferometry (PSI) is a highly accurate method for measuring the nanometer-scale relative surface height of a semi-reflective test surface. PSI is effectively used in conjunction with Fizeau interferometers for optical testing, hard disk inspection, and semiconductor wafer flatness. However, commonly-used PSI algorithms are unable to produce an accurate phase measurement if more than one reflective surface is present in the Fizeau interferometer test cavity. Examples of test parts that fall into this category include lithography mask blanks and their protective pellicles, and plane parallel optical beam splitters. The plane parallel surfaces of these parts generate multiple interferograms that are superimposed in the recording plane of the Fizeau interferometer. When using wavelength shifting in PSI the phase shifting speed of each interferogram is proportional to the optical path difference (OPD) between the two reflective surfaces. The proposed method is able to differentiate each underlying interferogram from each other in an optimal manner. In this paper, we present a method for simultaneously measuring the multiple test surfaces of all underlying interferograms from these superimposed interferograms through the use of a weighted least-square fitting technique. The theoretical analysis of weighted least-square technique and the measurement results will be described in this paper.

  2. Estimation of surface absorptivity in laser surface heating process with experimental data

    International Nuclear Information System (INIS)

    Chen, H-T; Wu, X-Y

    2006-01-01

    This study applies a hybrid technique of the Laplace transform and finite-difference methods in conjunction with the least-squares method and experimental temperature data inside the test material to predict the unknown surface temperature, heat flux and absorptivity for various surface conditions in the laser surface heating process. In this study, the functional form of the surface temperature is unknown a priori and is assumed to be a function of time before performing the inverse calculation. In addition, the whole time domain is divided into several analysis sub-time intervals and then these unknown estimates on each analysis interval can be predicted. In order to show the accuracy of the present inverse method, comparisons are made among the present estimates, direct results and previous results, showing that the present estimates agree with the direct results for the simulated problem. However, the present estimates of the surface absorptivity deviate slightly from previous estimated results under the assumption of constant thermal properties. The effect of the surface conditions on the surface absorptivity and temperature is not negligible

  3. Erosion resistant anti-ice surfaces generated by ultra short laser pulses

    NARCIS (Netherlands)

    Del Cerro, D.A.; Römer, G.R.B.E.; Huis in't Veld, A.J.

    2010-01-01

    Wetting properties of a wide range of materials can be modified by accurate laser micromachining with ultra short laser pulses. Controlling the surface topography in a micro and sub-micrometer scale allows the generation of water-repellent surfaces, which remain dry and prevent ice accumulation

  4. Experimental and numerical investigation of laser forming of cylindrical surfaces with arbitrary radius of curvature

    Directory of Open Access Journals (Sweden)

    Mehdi Safari

    2016-09-01

    Full Text Available In this work, laser forming of cylindrical surfaces with arbitrary radius of curvature is investigated experimentally and numerically. For laser forming of cylindrical surfaces with arbitrary radius of curvature, a new and comprehensive method is proposed in this paper. This method contains simple linear irradiating lines and using an analytical method, required process parameters for laser forming of a cylindrical surface with a specific radius of curvature is proposed. In this method, laser output power, laser scanning speed and laser beam diameter are selected based on laser machine and process limitations. As in the laser forming of a cylindrical surface, parallel irradiating lines are needed; therefore key parameter for production of a cylindrical surface with a specific radius of curvature is the number of irradiating lines. Hence, in the proposed analytical method, the required number of irradiating lines for production of a cylindrical surface with a specific radius of curvature is suggested. Performance of the proposed method for production of cylindrical surface with a specific radius of curvature is verified with experimental tests. The results show that using proposed analytical method, cylindrical surfaces with any radius of curvature can be produced successfully.

  5. Laser surface treatment for enhanced titanium to carbon fiber-reinforced polymer adhesion

    NARCIS (Netherlands)

    Palavra, Armin; Coelho, Bruno N.; de Hosson, Jeff Th. M.; Lima, Milton S. F.; Carvalho, Sheila M.; Costa, Adilson R.

    The adhesion between carbon fiber-reinforced polymer (CFRP) and titanium parts can be improved by laser surface texturing before gluing them together. Here, a pulsed Nd:YAG laser was employed before bonding of the textured surfaces using an epoxy paste adhesive. To investigate the influence of the

  6. Mimicking lizard-like surface structures upon ultrashort laser pulse irradiation of inorganic materials

    Science.gov (United States)

    Hermens, U.; Kirner, S. V.; Emonts, C.; Comanns, P.; Skoulas, E.; Mimidis, A.; Mescheder, H.; Winands, K.; Krüger, J.; Stratakis, E.; Bonse, J.

    2017-10-01

    Inorganic materials, such as steel, were functionalized by ultrashort laser pulse irradiation (fs- to ps-range) to modify the surface's wetting behavior. The laser processing was performed by scanning the laser beam across the surface of initially polished flat sample material. A systematic experimental study of the laser processing parameters (peak fluence, scan velocity, line overlap) allowed the identification of different regimes associated with characteristic surface morphologies (laser-induced periodic surface structures, grooves, spikes, etc.). Analyses of the surface using optical as well as scanning electron microscopy revealed morphologies providing the optimum similarity to the natural skin of lizards. For mimicking skin structures of moisture-harvesting lizards towards an optimization of the surface wetting behavior, additionally a two-step laser processing strategy was established for realizing hierarchical microstructures. In this approach, micrometer-scaled capillaries (step 1) were superimposed by a laser-generated regular array of small dimples (step 2). Optical focus variation imaging measurements finally disclosed the three dimensional topography of the laser processed surfaces derived from lizard skin structures. The functionality of these surfaces was analyzed in view of wetting properties.

  7. Selective metallization of polymers using laser induced surface activation (LISA)—characterization and optimization of porous surface topography

    DEFF Research Database (Denmark)

    Zhang, Yang; Hansen, Hans Nørgaard; De Grave, Arnaud

    2011-01-01

    Laser induced selective activation (LISA) is a molded interconnected devices technique for selective metallization of polymers. On the working piece, only the laser-machined area can be metalized in the subsequent plating. The principle of the technology is introduced. Surface analysis was perfor...

  8. An efficient approach for computing the geometrical optics field reflected from a numerically specified surface

    Science.gov (United States)

    Mittra, R.; Rushdi, A.

    1979-01-01

    An approach for computing the geometrical optic fields reflected from a numerically specified surface is presented. The approach includes the step of deriving a specular point and begins with computing the reflected rays off the surface at the points where their coordinates, as well as the partial derivatives (or equivalently, the direction of the normal), are numerically specified. Then, a cluster of three adjacent rays are chosen to define a 'mean ray' and the divergence factor associated with this mean ray. Finally, the ampilitude, phase, and vector direction of the reflected field at a given observation point are derived by associating this point with the nearest mean ray and determining its position relative to such a ray.

  9. A geometrical optics polarimetric bidirectional reflectance distribution function for dielectric and metallic surfaces.

    Science.gov (United States)

    Hyde, M W; Schmidt, J D; Havrilla, M J

    2009-11-23

    A polarimetric bidirectional reflectance distribution function (pBRDF), based on geometrical optics, is presented. The pBRDF incorporates a visibility (shadowing/masking) function and a Lambertian (diffuse) component which distinguishes it from other geometrical optics pBRDFs in literature. It is shown that these additions keep the pBRDF bounded (and thus a more realistic physical model) as the angle of incidence or observation approaches grazing and better able to model the behavior of light scattered from rough, reflective surfaces. In this paper, the theoretical development of the pBRDF is shown and discussed. Simulation results of a rough, perfect reflecting surface obtained using an exact, electromagnetic solution and experimental Mueller matrix results of two, rough metallic samples are presented to validate the pBRDF.

  10. LiDAR Relative Reflectivity Surface (2011) for Coral Bay, St. John

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 0.3x0.3 meter resolution relative seafloor reflectivity surface for Coral Bay, St. John in the U.S....

  11. Classification of Clean and Dirty Pighouse Surfaces Based on Spectral Reflectance

    DEFF Research Database (Denmark)

    Blanke, Mogens; Braithwaite, Ian David; Zhang, Guo-Qiang

    2004-01-01

    of designing a vision based system to locate dirty areas and subsequently direct a cleaning robot to remove dirt. Novel results include the characterisation of the spectral reflectance of real surfaces and dirt in a pig house and the design of illumination to obtain discrimination of clean from dirty areas...

  12. LiDAR Relative Reflectivity Surface (2011) for Fish Bay, St. John

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 0.3x0.3 meter resolution relative seafloor reflectivity surface for Fish Bay, St. John in the U.S....

  13. Characterization, optical properties and laser ablation behavior of epoxy resin coatings reinforced with high reflectivity ceramic particles

    Science.gov (United States)

    Li, Wenzhi; Kong, Jing; Wu, Taotao; Gao, Lihong; Ma, Zhuang; Liu, Yanbo; Wang, Fuchi; Wei, Chenghua; Wang, Lijun

    2018-04-01

    Thermal damage induced by high power energy, especially high power laser, significantly affects the lifetime and performance of equipment. High-reflectance coating/film has attracted considerable attention due to its good performance in the damage protection. Preparing a high-reflectance coating with high reaction endothermal enthalpy will effectively consume a large amount of incident energy and in turn protect the substrate from thermal damage. In this study, a low temperature process was used to prepare coatings onto substrate with complex shape and avoid thermal effect during molding. An advanced high reflection ceramic powder, La1‑xSrxTiO3+δ , was added in the epoxy adhesive matrix to improve the reflectivity of coating. The optical properties and laser ablation behaviors of coatings with different ceramic additive ratio of La1‑xSrxTiO3+δ and modified epoxy-La1‑xSrxTiO3+δ with ammonium polyphosphate coatings were investigated, respectively. We found that the reflectivity of coatings is extremely high due to mixed high-reflection La1‑xSrxTiO3+δ particles, up to 96% at 1070 nm, which can significantly improve the laser resistance. In addition, the ammonium polyphosphate modifies the residual carbon structure of epoxy resin from discontinuous fine particles structure to continuous and porous structure, which greatly enhances the thermal-insulation property of coating. Furthermore, the laser ablation threshold is improved obviously, which is from 800 W cm‑2 to 1000 W cm‑2.

  14. Bidirectional reflectance distribution function modeling of one-dimensional rough surface in the microwave band

    International Nuclear Information System (INIS)

    Guo Li-Xin; Gou Xue-Yin; Zhang Lian-Bo

    2014-01-01

    In this study, the bidirectional reflectance distribution function (BRDF) of a one-dimensional conducting rough surface and a dielectric rough surface are calculated with different frequencies and roughness values in the microwave band by using the method of moments, and the relationship between the bistatic scattering coefficient and the BRDF of a rough surface is expressed. From the theory of the parameters of the rough surface BRDF, the parameters of the BRDF are obtained using a genetic algorithm. The BRDF of a rough surface is calculated using the obtained parameter values. Further, the fitting values and theoretical calculations of the BRDF are compared, and the optimization results are in agreement with the theoretical calculation results. Finally, a reference for BRDF modeling of a Gaussian rough surface in the microwave band is provided by the proposed method. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  15. Study on effective laser cleaning method to remove carbon layer from a gold surface

    International Nuclear Information System (INIS)

    Singh, Amol; Modi, Mohammed H; Lodha, G S; Choubey, A K; Upadhyaya, B N

    2013-01-01

    Hydrocarbon cracking and carbon contamination is a common problem in soft x-ray Synchrotron Radiation (SR) beamlines. Carbon contamination on optics is known to absorb and scatter radiation close to the C K-edge (284 eV) spectral region. The purpose of this work is to study and develop a laser cleaning method that can effectively remove the carbon contaminations without damaging the underneath gold-coated optics. The laser cleaning process is a non-contact, accurate, efficient and safe. Nd:YAG laser of 100 ns pulse duration is used for carbon cleaning. The effect of laser pulse duration, laser fluence, number of laser passes, angle of incidence and spot overlapping on the cleaning performance is studied. Cleaning effect and subsequent film quality after laser irradiation is analyzed using x-ray photoelectron spectroscopy (XPS) and soft x-ray reflectivity (SXR) techniques.

  16. Enhancing the antibacterial performance of orthopaedic implant materials by fibre laser surface engineering

    DEFF Research Database (Denmark)

    Chan, Chi-Wai; Carson, Louise; Smith, Graham C.

    2017-01-01

    to the effort on enhancing osseointegration, wear and corrosion resistance of implant materials. In this study, the effects of laser surface treatment on enhancing the antibacterial properties of commercially pure (CP) Ti (Grade 2), Ti6Al4V (Grade 5) and CoCrMo alloy implant materials were studied and compared...... for the first time. Laser surface treatment was performed by a continuous wave (CW) fibre laser with a near-infrared wavelength of 1064 nm in a nitrogen-containing environment. Staphylococcus aureus, commonly implicated in infection associated with orthopaedic implants, was used to investigate the antibacterial...... properties of the laser-treated surfaces. The surface roughness and topography of the laser-treated materials were analysed by a 2D roughness testing and by AFM. The surface morphologies before and after 24 h of bacterial cell culture were captured by SEM, and bacterial viability was determined using live...

  17. The Evaluation of Surface Integrity During Machining of Inconel 718 with Various Laser Assistance Strategies

    Directory of Open Access Journals (Sweden)

    Wojciechowski Szymon

    2017-01-01

    Full Text Available The paper is focused on the evaluation of surface integrity formed during turning of Inconel 718 with the application of various laser assistance strategies. The primary objective of the work was to determine the relations between the applied machining strategy and the obtained surface integrity, in order to select the effective cutting conditions allowing the obtainment of high surface quality. The carried out experiment included the machining of Inconel 718 in the conventional turning conditions, as well as during the continuous laser assisted machining and sequential laser assistance. The surface integrity was evaluated by the measurements of machined surface topographies, microstructures and the microhardness. Results revealed that surface integrity of Inconel 718 is strongly affected by the selected machining strategy. The significant improvement of the surface roughness formed during machining of Inconel 718, can be reached by the application of simultaneous laser heating and cutting (LAM.

  18. In vivo assessment of the structure of skin microcirculation by reflectance confocal-laser-scanning microscopy

    Science.gov (United States)

    Sugata, Keiichi; Osanai, Osamu; Kawada, Hiromitsu

    2012-02-01

    One of the major roles of the skin microcirculation is to supply oxygen and nutrition to the surrounding tissue. Regardless of the close relationship between the microcirculation and the surrounding tissue, there are few non-invasive methods that can evaluate both the microcirculation and its surrounding tissue at the same site. We visualized microcapillary plexus structures in human skin using in vivo reflectance confocal-laser-scanning microscopy (CLSM), Vivascope 3000® (Lucid Inc., USA) and Image J software (National Institutes of Health, USA) for video image processing. CLSM is a non-invasive technique that can visualize the internal structure of the skin at the cellular level. In addition to internal morphological information such as the extracellular matrix, our method reveals capillary structures up to the depth of the subpapillary plexus at the same site without the need for additional optical systems. Video images at specific depths of the inner forearm skin were recorded. By creating frame-to-frame difference images from the video images using off-line video image processing, we obtained images that emphasize the brightness depending on changes of intensity coming from the movement of blood cells. Merging images from different depths of the skin elucidates the 3-dimensional fine line-structure of the microcirculation. Overall our results show the feasibility of a non-invasive, high-resolution imaging technique to characterize the skin microcirculation and the surrounding tissue.

  19. Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry

    Science.gov (United States)

    Strömberg, Tomas; Karlsson, Hanna; Fredriksson, Ingemar; Nyström, Fredrik H.; Larsson, Marcus

    2014-05-01

    Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

  20. Radius of curvature measurement of spherical smooth surfaces by multiple-beam interferometry in reflection

    Science.gov (United States)

    Abdelsalam, D. G.; Shaalan, M. S.; Eloker, M. M.; Kim, Daesuk

    2010-06-01

    In this paper a method is presented to accurately measure the radius of curvature of different types of curved surfaces of different radii of curvatures of 38 000,18 000 and 8000 mm using multiple-beam interference fringes in reflection. The images captured by the digital detector were corrected by flat fielding method. The corrected images were analyzed and the form of the surfaces was obtained. A 3D profile for the three types of surfaces was obtained using Zernike polynomial fitting. Some sources of uncertainty in measurement were calculated by means of ray tracing simulations and the uncertainty budget was estimated within λ/40.

  1. Laser texturing of Hastelloy C276 alloy surface for improved hydrophobicity and friction coefficient

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.

    2016-03-01

    Laser treatment of Hastelloy C276 alloy is carried out under the high pressure nitrogen assisting gas environment. Morphological and metallurgical changes in the laser treated layer are examined using the analytical tools including, scanning electron and atomic force microscopes, X-ray diffraction, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. Microhardness is measured and the residual stress formed in the laser treated surface is determined from the X-ray data. The hydrophibicity of the laser treated surface is assessed using the sessile drop method. Friction coefficient of the laser treated layer is obtained incorporating the micro-tribometer. It is found that closely spaced laser canning tracks create a self-annealing effect in the laser treated layer and lowers the thermal stress levels through modifying the cooling rates at the surface. A dense structure, consisting of fine size grains, enhances the microhardness of the surface. The residual stress formed at the surface is compressive and it is in the order of -800 MPa. Laser treatment improves the surface hydrophobicity significantly because of the formation of surface texture composing of micro/nano-pillars.

  2. Mechanisms for the reflection of light atoms from crystal surfaces at kilovolt energies

    International Nuclear Information System (INIS)

    Hou, M.; Robinson, M.T.

    1978-01-01

    The computer program MARLOWE was used to investigate the backscattering of protons from the (110) surface of a nickel crystal. Grazing incidence was considered so that anisotropic effects originated mainly from the surface region. The contribution of aligned scattering was studied by comparing the results with similar calculations for an amorphous target. Energy distributions of backscattered particles were investigated for incident energies ranging from 0.1 to 5 keV. The structure of these distributions was explained by making calculations for several target thickness. Specular reflection was found to depend on the structure of the first few atomic planes only. The (110) rows in the surface plane were responsible for focusing into surface semichannels. Focusing in these semichannels was found to be the strongest under total reflection conditions (below about 1.3 keV) while the scattering intensity from surface rows increased with increasing incident energy. The orientation of the plane of incidence was found to have large influence on the relative contributions of the reflection mechanisms involved. (orig.) [de

  3. Surface topography to reflectivity mapping in two-dimensional photonic crystals designed in germanium

    Energy Technology Data Exchange (ETDEWEB)

    Husanu, M.A.; Ganea, C.P. [National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele, Ilfov (Romania); Anghel, I. [National Institute for Laser, Plasma & Radiation Physics, Atomistilor 409, 077125 Magurele (Romania); University of Bucharest, Faculty of Physics, Atomistilor 405, 077125 Magurele (Romania); Florica, C.; Rasoga, O. [National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele, Ilfov (Romania); Popescu, D.G., E-mail: dana.popescu@infim.ro [National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele, Ilfov (Romania)

    2015-11-15

    Highlights: • Laser ablation is used for drilling a periodic 2D photonic structure. • Confinement of radiation is revealed by infra-red spectromicroscopy correlated with numerical calculations. • Telecommunication range is accessible upon tuning conveniently the processing parameters. - Abstract: Light confinement in a two dimensional photonic crystal (2D PhC) with hexagonal symmetry is studied using infra-red reflectance spectromicroscopy and numerical calculations. The structure has been realized by laser ablation, using a pulsed laser (λ = 775 nm), perforating an In-doped Ge wafer and creating a lattice of holes with well-defined symmetry. Correlating the spectral signature of the photonic gaps recorded experimentally with the results obtained in the finite difference time domain and finite difference frequency domain calculations, we established the relationship between the geometric parameters of the structure (lattice constants, shape of the hole) and its efficiency in trapping and guiding the radiation in a well-defined frequency range. Besides the gap in the low energy range of transversal electric modes, a second one is identified in the telecommunication range, originating in the localization of the leaky modes within the radiation continuum. The emerging picture is of a device with promising characteristics as an alternative to Si-based technology in photonic device fabrication with special emphasize in energy storage and conversion.

  4. Critical coupling of surface plasmons in graphene attenuated total reflection geometry

    Energy Technology Data Exchange (ETDEWEB)

    Cuevas, Mauro, E-mail: cuevas@df.uba.ar [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Facultad de Ingeniería y Tecnología Informática, Universidad de Belgrano, Villanueva 1324, C1426BMJ, Buenos Aires (Argentina); Grupo de Electromagnetismo Aplicado, Departamento de Física, FCEN, Universidad de Buenos Aires and IFIBA, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires (Argentina)

    2016-12-09

    We study the optical response of an attenuated total reflection (ATR) structure in Otto configuration with graphene sheet, paying especial attention to the occurrence of total absorption. Our results show that due to excitation of surface plasmons on the graphene sheet, two different conditions of total absorption may occur. At these conditions, the energy loss of the surface plasmon by radiation is equal to its energy loss by absorption into the graphene sheet. We give necessary conditions on ATR parameters for the existence of total absorption. - Highlights: • Attenuated total reflection (ATR) structure with graphene sheet. • Surface plasmons and power matched condition. • Necessary conditions on ATR parameters for the existence of total absorption.

  5. Critical coupling of surface plasmons in graphene attenuated total reflection geometry

    International Nuclear Information System (INIS)

    Cuevas, Mauro

    2016-01-01

    We study the optical response of an attenuated total reflection (ATR) structure in Otto configuration with graphene sheet, paying especial attention to the occurrence of total absorption. Our results show that due to excitation of surface plasmons on the graphene sheet, two different conditions of total absorption may occur. At these conditions, the energy loss of the surface plasmon by radiation is equal to its energy loss by absorption into the graphene sheet. We give necessary conditions on ATR parameters for the existence of total absorption. - Highlights: • Attenuated total reflection (ATR) structure with graphene sheet. • Surface plasmons and power matched condition. • Necessary conditions on ATR parameters for the existence of total absorption.

  6. Sunlight reflection off the spacecraft with a solar sail on the surface of mars

    Science.gov (United States)

    Starinova, O. L.; Rozhkov, M. A.; Gorbunova, I. V.

    2018-05-01

    Modern technologies make it possible to fulfill many projects in the field of space exploration. One such project is the colonization of Mars and providing favorable conditions for living on it. Authors propose principles of functioning of the spacecraft with a solar sail, intended to create a thermal and light spot in a predetermined area of the Martian surface. This additional illumination can maintain and support certain climatic conditions on a small area where a Mars base could be located. This paper investigate the possibility of the spacecraft continuously reflect the sunlight off the solar sail on the small area of the Mars surface. The mathematical motion model in such condition of the solar sail's orientation is considered and used for motion simulation session. Moreover, the analysis of this motion is performed. Thus, were obtained parameters of the synchronic non-Keplerian orbit and spacecraft construction. In addition, were given recommendations for further applying satellites to reflect the sunlight on a planet's surface.

  7. Lunar surface remanent magnetic fields detected by the electron reflection method

    Science.gov (United States)

    Lin, R. P.; Anderson, K. A.; Bush, R.; Mcguire, R. E.; Mccoy, J. E.

    1976-01-01

    We present maps of the lunar surface remanent magnetic fields detected by the electron reflection method. These maps provide substantial coverage of the latitude band from 30 N southward to 30 S with a resolution of about 40 km and a sensitivity of about 0.2 gamma at the lunar surface. Regions of remanent magnetization are observed ranging in size from the resolution limit of 1.25 deg to above approximately 60 deg. The largest contiguous region fills the Big Backside Basin where it is intersected by the spacecraft orbital tracks. Preliminary analyses of the maps show that the source regions of lunar limb compressions correspond to regions of strong surface magnetism, and that there does not appear to be sharply discontinuous magnetization at the edges of maria. We also analyze the electron reflection observations to obtain information on the direction and distribution of magnetization in the Van de Graaff anomaly region.

  8. Lactoperoxidase catalyzed radioiodination of cell surface immunoglobulin: incorporated radioactivity may not reflect relative cell surface Ig density

    International Nuclear Information System (INIS)

    Wilder, R.L.; Yuen, C.C.; Mage, R.G.

    1979-01-01

    Rabbit and mouse splenic lymphocytes were radioiodinated by the lactoperoxidase technique, extracted with non-ionic detergent, immunoprecipitated with high titered rabbit anti-kappa antisera, and compared by SDS-PAGE. Mouse sIg peaks were reproducibly larger in size than rabbit sIg peaks (often greater than 10 times). Neither differences in incorporation of label into the rabbit cell surface, nor differences in average sIg density explain this result. Total TCA-precipitable radioactivity was similar in each species. Estimation of the relative amounts of sIg in the mouse and rabbit showed similar average sIg densities. Differences in detergent solubility, proteolytic lability, or antisera used also do not adequately account for this difference. Thus, these data indicate that radioactivity incorporated after lactoperoxidase catalyzed cell surface radioiodination may not reflect cell surface Ig density. Conclusions about cell surface density based upon relative incorporation of radioactivity should be confirmed by other approaches

  9. Laser driven supersonic flow over a compressible foam surface on the Nike laser

    International Nuclear Information System (INIS)

    Harding, E. C.; Drake, R. P.; Gillespie, R. S.; Visco, A.; Grosskopf, M. J.; Ditmar, J. R.; Aglitskiy, Y.; Velikovich, A. L.; Weaver, J. L.; Plewa, T.

    2010-01-01

    A laser driven millimeter-scale target was used to generate a supersonic shear layer in an attempt to create a Kelvin-Helmholtz (KH) unstable interface in a high-energy-density (HED) plasma. The KH instability is a fundamental fluid instability that remains unexplored in HED plasmas, which are relevant to the inertial confinement fusion and astrophysical environments. In the experiment presented here the Nike laser [S. P. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to create and drive Al plasma over a rippled foam surface. In response to the supersonic Al flow (Mach=2.6±1.1) shocks should form in the Al flow near the perturbations. The experimental data were used to infer the existence and location of these shocks. In addition, the interface perturbations show growth that has possible contributions from both KH and Richtmyer-Meshkov instabilities. Since compressible shear layers exhibit smaller growth, it is important to use the KH growth rate derived from the compressible dispersion relation.

  10. Probing Ultrafast Electron Dynamics at Surfaces Using Soft X-Ray Transient Reflectivity Spectroscopy

    Science.gov (United States)

    Baker, L. Robert; Husek, Jakub; Biswas, Somnath; Cirri, Anthony

    The ability to probe electron dynamics with surface sensitivity on the ultrafast time scale is critical for understanding processes such as charge separation, injection, and surface trapping that mediate efficiency in catalytic and energy conversion materials. Toward this goal, we have developed a high harmonic generation (HHG) light source for femtosecond soft x-ray reflectivity. Using this light source we investigated the ultrafast carrier dynamics at the surface of single crystalline α-Fe2O3, polycrystalline α-Fe2O3, and the mixed metal oxide, CuFeO2. We have recently demonstrated that CuFeO2 in particular is a selective catalyst for photo-electrochemical CO2 reduction to acetate; however, the role of electronic structure and charge carrier dynamics in mediating catalytic selectivity has not been well understood. Soft x-ray reflectivity measurements probe the M2,3, edges of the 3d transition metals, which provide oxidation and spin state resolution with element specificity. In addition to chemical state specificity, these measurements are also surface sensitive, and by independently simulating the contributions of the real and imaginary components of the complex refractive index, we can differentiate between surface and sub-surface contributions to the excited state spectrum. Accordingly, this work demonstrates the ability to probe ultrafast carrier dynamics in catalytic materials with element and chemical state specificity and with surface sensitivity.

  11. Effects of various polishing media and techniques on the surface finish and behavior of laser glasses

    International Nuclear Information System (INIS)

    Landingham, R.L.; Casey, A.W.; Lindahl, R.O.

    1978-01-01

    The advance of high-power laser technology is dependent on the rate of advancement in laser glass forming and surface preparation. The threshold damage of glass surfaces continues to be a weak link in the overall advancement of laser technology. Methods were developed and used in the evaluation of existing glass surface preparation techniques. Modified procedures were evaluated to reduce surface contamination and subsurface defects. Polishing rates were monitored under controlled polishing conditions (purity, pH, particle size distribution, particle concentration, etc.). Future work at LLL for this ongoing investigation is described

  12. High speed surface cleaning by a high repetition rated TEA-CO2 laser

    International Nuclear Information System (INIS)

    Tsunemi, Akira; Hirai, Ryo; Hagiwara, Kouji; Nagasaka, Keigo; Tashiro, Hideo

    1994-01-01

    We demonstrated the feasibility of high speed cleaning of solid surfaces by the laser ablation technique using a TEA-CO 2 laser. The laser pulses with the repetition rate of 1 kHz were applied to paint, rust, moss and dirt attached on the surfaces. The attachments were effectively removed without the damage of bulk surfaces by the irradiation of line-focused sequential pulses with an energy of 300 mJ/pulse. A cleaning rate reached to 17 m 2 /hour for the case of paint removal from iron surfaces. (author)

  13. Low-temperature micro-photoluminescence spectroscopy on laser-doped silicon with different surface conditions

    Science.gov (United States)

    Han, Young-Joon; Franklin, Evan; Fell, Andreas; Ernst, Marco; Nguyen, Hieu T.; Macdonald, Daniel

    2016-04-01

    Low-temperature micro-photoluminescence spectroscopy (μ-PLS) is applied to investigate shallow layers of laser-processed silicon for solar cell applications. Micron-scale measurement (with spatial resolution down to 1 μm) enables investigation of the fundamental impact of laser processing on the electronic properties of silicon as a function of position within the laser-processed region, and in particular at specific positions such as at the boundary/edge of processed and unprocessed regions. Low-temperature μ-PLS enables qualitative analysis of laser-processed regions by identifying PLS signals corresponding to both laser-induced doping and laser-induced damage. We show that the position of particular luminescence peaks can be attributed to band-gap narrowing corresponding to different levels of subsurface laser doping, which is achieved via multiple 248 nm nanosecond excimer laser pulses with fluences in the range 1.5-4 J/cm2 and using commercially available boron-rich spin-on-dopant precursor films. We demonstrate that characteristic defect PL spectra can be observed subsequent to laser doping, providing evidence of laser-induced crystal damage. The impact of laser parameters such as fluence and number of repeat pulses on laser-induced damage is also analyzed by observing the relative level of defect PL spectra and absolute luminescence intensity. Luminescence owing to laser-induced damage is observed to be considerably larger at the boundaries of laser-doped regions than at the centers, highlighting the significant role of the edges of laser-doped region on laser doping quality. Furthermore, by comparing the damage signal observed after laser processing of two different substrate surface conditions (chemically-mechanically polished and tetramethylammonium hydroxide etched), we show that wafer preparation can be an important factor impacting the quality of laser-processed silicon and solar cells.

  14. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Thresholds of surface plasma formation by the interaction of laser pulses with a metal

    Science.gov (United States)

    Borets-Pervak, I. Yu; Vorob'ev, V. S.

    1995-04-01

    An analysis is made of a model of the formation of a surface laser plasma which takes account of the heating and vaporisation of thermally insulated surface microdefects. This model is used in an interpretation of experiments in which such a plasma has been formed by irradiation of a titanium target with microsecond CO2 laser pulses. A comparison with the experimental breakdown intensities is used to calculate the average sizes of microdefects and their concentration: the results are in agreement with the published data. The dependence of the delay time of plasma formation on the total energy in a laser pulse is calculated.

  15. Evaluation of BRDF Archetypes for Representing Surface Reflectance Anisotropy Using MODIS BRDF Data

    Directory of Open Access Journals (Sweden)

    Hu Zhang

    2015-06-01

    Full Text Available Bidirectional reflectance distribution function (BRDF archetypes extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS BRDF/Albedo product over the global Earth Observing System Land Validation Core Sites can be used to simplify BRDF models. The present study attempts to evaluate the representativeness of BRDF archetypes for surface reflectance anisotropy. Five-year forward-modeled MODIS multi-angular reflectance (MCD-ref and aditional actual MODIS multi-angular observations (MCD-obs in four growing periods in 2008 over three tiles were taken as validation data. First, BRDF archetypes in the principal plane were qualitatively compared with the time-series MODIS BRDF product of randomly sampled pixels. Secondly, BRDF archetypes were used to fit MCD-ref, and the average root-mean-squared errors (RMSEs over each tile were examined for these five years. Finally, both BRDF archetypes and the MODIS BRDF were used to fit MCD-obs, and the histograms of the fit-RMSEs were compared. The consistency of the directional reflectance between the BRDF archetypes and MODIS BRDFs in nadir-view, hotspot and entire viewing hemisphere at 30° and 50° solar geometries were also examined. The results confirm that BRDF archetypes are representative of surface reflectance anisotropy for available snow-free MODIS data.

  16. Reflectivity and energy balance in pulsed-laser deposition experiments from mono- and bi-atomic targets

    International Nuclear Information System (INIS)

    Mueller, T.; Rohr, K.P.; Sinha, B. K.

    2002-01-01

    Reflectivity and complete energy balance from the planar targets of aluminum, copper, nickel, and molybdenum have been measured using a Nd: glass laser (λ=1060 nm,τ=5 ns) in the low intensity regime of laser plasma interaction as a function of focal spot size. The magnitude of partition of total incident laser energy into different channels is observed to decrease as the focal spot size increases. It is further observed that the magnitude of partition of the incident energy into these channels, in general, decreases as the atomic number increases for any given focal spot size, although, the reflectivity component of the partitioned energy increases with focal spot size for any given element. The reflectivities of copper and tungsten and their alloy were measured separately. The reflectivity from the alloy plasma was reduced by a factor of 6 compared to either element separately. This observation confirms the recent theory that in the multiion plasma the ion acoustic waves are additionally damped due to additional Joule, thermal diffusion, and viscous terms in the modified ion-fluid theory of the ion acoustic waves in a multiion species plasma

  17. Effects of different lasers and particle abrasion on surface characteristics of zirconia ceramics.

    Directory of Open Access Journals (Sweden)

    Sakineh Arami

    2014-04-01

    Full Text Available The aim of this study was to assess the surface of yttrium-stabilized tetragonal zirconia (Y-TZP after surface treatment with lasers and airborne-particle abrasion.First, 77 samples of presintered zirconia blocks measuring 10 × 10 × 2 mm were made, sintered and polished. Then, they were randomly divided into 11 groups (n=7 and received surface treatments namely, Er:YAG laser irradiation with output power of 1.5, 2 and 2.5 W, Nd:YAG laser with output power of 1.5, 2 and 2.5 W, CO2 laser with output power of 3, 4 and 5 W, AL2O3 airborne-particle abrasion (50μ and no treatment (controls. Following treatment, the parameters of surface roughness such as Ra, Rku and Rsk were evaluated using a digital profilometer and surface examination was done by SEM.According to ANOVA and Tukey's test, the mean surface roughness (Ra after Nd:YAG laser irradiation at 2 and 2.5 W was significantly higher than other groups. Roughness increased with increasing output power of Nd:YAG and CO2 lasers. Treated surfaces by Er:YAG laser and air abrasion showed similar surface roughness. SEM micrographs showed small microcracks in specimens irradiated with Nd:YAG and CO2 lasers.Nd:YAG laser created a rough surface on the zirconia ceramic with many microcracks; therefore, its use is not recommended. Air abrasion method can be used with Er:YAG laser irradiation for the treatment of zirconia ceramic.

  18. Modeling and analysis of surface roughness effects on sputtering, reflection, and sputtered particle transport

    International Nuclear Information System (INIS)

    Brooks, J.N.; Ruzic, D.N.

    1990-01-01

    The microstructure of the redeposited surface in tokamaks may affect sputtering and reflection properties and subsequent particle transport. This subject has been studied numerically using coupled models/codes for near-surface plasma particle kinetic transport (WBC code) and rough surface sputtering (fractal-TRIM). The coupled codes provide an overall Monte Carlo calculation of the sputtering cascade resulting from an initial flux of hydrogen ions. Beryllium, carbon, and tungsten surfaces are analyzed for typical high recycling, oblique magnetic field, divertor conditions. Significant variations in computed sputtering rates are found with surface roughness. Beryllium exhibits high D-T and self-sputtering coefficients for the plasma regime studied (T e = 30-75 eV). Carbon and tungsten sputtering is significantly lower. 9 refs., 6 figs., 1 tab

  19. A method for the characterization of the reflectance of anisotropic functional surfaces

    DEFF Research Database (Denmark)

    Regi, Francesco; Nielsen, J B; Li, Dongya

    2018-01-01

    The functional properties of micro-structured surfaces have gained increasing interest thanks to many applications such as wetting, adhesion, thermal and/or electrical conductivity. In this study, directional optical properties, i.e. contrast between two regions of a surface, were achieved...... reflectance of the surface for a range of design-specific view-illumination configurations was determined using a method that involves a Hirox RH-2000 digital microscope, used as a gonioreflectometer. This method allows the empirical determination of the optimum surface microstructure for maximizing contrast...... between two horizontally orthogonal views. The results show that even if the uncertainty related to the instrumentation is up to 20% in some cases, this procedure is suitable for the characterization of the surface of both metal and plastic counterpart....

  20. Multi-Criteria Analysis of Laser Cut Surface Characteristics in CO2 Laser Cutting of Stainless Steel

    Directory of Open Access Journals (Sweden)

    M. Radovanović

    2015-06-01

    Full Text Available In this paper an approach for multi-criteria analysis of laser cut surface characteristics using multi-criteria decision making (MCDM approach was presented. Laser cutting experiment was conducted based on Taguchi’s L27 experimental design by varying laser power, cutting speed, assist gas pressure and focus position at three levels. Multi-criteria analysis was performed by using the weighted aggregated sum product assessment (WASPAS method while considering burr height, drag line separation, depth of separation line, surface roughness and perpendicularity of the cut as assessment criteria. Based on conducted experimental investigation the MCDM model with 27 alternatives (laser cuts and five criteria was developed. The relative importance of criteria was determined by using pair-wise comparison matrix and geometric mean method of the analytic hierarchy process (AHP method.

  1. [A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

    Science.gov (United States)

    Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

    2015-07-01

    Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable.

  2. Multipulse nanosecond laser irradiation of silicon for the investigation of surface morphology and photoelectric properties

    Science.gov (United States)

    Sardar, Maryam; Chen, Jun; Ullah, Zaka; Jelani, Mohsan; Tabassum, Aasma; Cheng, Ju; Sun, Yuxiang; Lu, Jian

    2017-12-01

    We irradiate the single crystal boron-doped silicon (Si) with different number of laser pulses at constant fluence (7.5 J cm-2) in ambient air using Nd:YAG laser and examine its surface morphology and photoelectric properties in details. The results obtained from optical micrographs reveal the increase in heat affected zone (HAZ) and melted area of laser irradiated Si with increasing number of laser pulses. The SEM micrographs evidence the formation of various surface morphologies like laser induced periodic surface structures, crater, microcracks, clusters, cavities, pores, trapped bubbles, nucleation sites, micro-bumps, redeposited material and micro- and nano-particles on the surface of irradiated Si. The surface profilometry analysis informs that the depth of crater is increased with increase in number of incident laser pulses. The spectroscopic ellipsometry reveals that the multipulse irradiation of Si changes its optical properties (refractive index and extinction coefficient). The current-voltage (I-V) characteristic curves of laser irradiated Si show that although the multipulse laser irradiation produces considerable number of surface defects and damages, the electrical properties of Si are well sustained after the multipulse irradiation. The current findings suggest that the multipulse irradiation can be an effective way to tune the optical properties of Si for the fabrication of wide range of optoelectronic devices.

  3. A study of laser surface treatment in bonded repair of composite aircraft structures.

    Science.gov (United States)

    Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

    2018-03-01

    Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

  4. Bi-directional Reflectance of Icy Surface Analogs: A Dual Approach

    Science.gov (United States)

    Quinones, Juan Manuel; Vides, Christina; Nelson, Robert M.; Boryta, Mark; Mannat, Ken s.

    2018-01-01

    Bi-directional reflectance measurements of analogs for planetary regolith have provided insight into the surface properties of planetary satellites and small bodies. Because Aluminum Oxide (Al2O3) and water ice share a similar hexagonal crystalline structure, the former has been used in laboratory experiments to simulate the regolith of both icy and dusty planetary bodies. By measuring various sizes of well sorted size fractions of Al2O3, the reflectance phase curve and porosity of a planetary regolith can be determined. We have designed an experiment to test the laboratory measurements produced by Nelson et al. (2000). Additionally, we made reflectance measurements for other alkali-halide compounds that could be used for applications beyond astronomy and planetary science.In order to provide an independent check on the Nelson et al. data, we designed an instrument with a different configuration. While both instruments take bidirectional reflectance measurements, our instrument, the Rigid Photometric Goniometer (RPG), is fixed at a phase angle of 5° and detects the scattered light with a photomultiplier tube (PMT). The PMT current is then measured with an electrometer. Following the example of Nelson et al., we measured the bidirectional reflectance of Al2O3 particulate size fractions between 0.1sizes from 20size that provided optimal, or maximum, reflectance for each compound. Our conclusions bring confirmation and clarity to photometric sciences.

  5. The process development of laser surface modification of commercially pure titanium (Grade 2) with rhenium

    Science.gov (United States)

    Kobiela, K.; Smolina, I.; Dziedzic, R.; Szymczyk, P.; Kurzynowski, T.; Chlebus, E.

    2016-12-01

    The paper presents the results of the process development of laser surface modification of commercially pure titanium with rhenium. The criterion of the successful/optimal process is the repetitive geometry of the surface, characterized by predictable and repetitive chemical composition over its entire surface as well as special mechanical properties (hardness and wear resistance). The analysis of surface geometry concluded measurements of laser penetration depth and heat affected zone (HAZ), the width of a single track as well as width of a clad. The diode laser installed on the industrial robot carried out the laser treatment. This solution made possible the continuous supply of powder to the substrate during the process. The aim of an investigation is find out the possibility of improving the tribological characteristics of the surface due to the rhenium alloying. The verification of the surface properties (tribological) concluded geometry measurements, microstructure observation, hardness tests and evaluation of wear resistance.

  6. Improvement in Surface Characterisitcs of Polymers for Subsequent Electroless Plating Using Liquid Assisted Laser Processing

    DEFF Research Database (Denmark)

    Marla, Deepak; Zhang, Yang; Jabbaribehnam, Mirmasoud

    2016-01-01

    Metallization of polymers is a widely used process in the electronic industry that involves their surface modification as a pre-treatment step. Laser-based surface modification is one of the commonly used techniques for polymers due to its speed and precision. The process involves laser heating...... of the polymer surface to generate a rough or porous surface. Laser processing in liquid generates superior surface characteristics that result in better metal deposition. In this study, a comparison of the surface characteristics obtained by laser processing in water vis-à-vis air along with the deposition...... characteristics are presented. In addition, a numerical model based on the finite volume method is developed to predict the temperature profile during the process. Based on the model results, it is hypothesized that physical phenomena such as vapor bubble generation and plasma formation may occur in the presence...

  7. Formation of various types of nanostructures on germanium surface by nanosecond laser pulses

    Science.gov (United States)

    Mikolutskiy, S. I.; Khasaya, R. R.; Khomich, Yu V.; Yamshchikov, V. A.

    2018-03-01

    The paper describes the formation of micro- and nanostructures in different parts of irradiation zone on germanium surface by multiple action of nanosecond pulses of ArF-laser. It proposes a simple method using only one laser beam without any optional devices and masks for surface treatment. Hexa- and pentagonal cells with submicron dimensions along the surface were observed in peripheral zone of irradiation spot by atomic-force microscopy. Nanostructures in the form of bulbs with rounded peaks with lateral sizes of 40-120 nm were obtained in peripheral low-intensity region of the laser spot. Considering experimental data on material processing by nanosecond laser pulses, a classification of five main types of surface reliefs formed by nanosecond laser pulses with energy density near or slightly above ablation threshold was proposed.

  8. Effect of Q-switched Laser Surface Texturing of Titanium on Osteoblast Cell Response

    Science.gov (United States)

    Voisey, K. T.; Scotchford, C. A.; Martin, L.; Gill, H. S.

    Titanium and its alloys are important biomedical materials. It is known that the surface texture of implanted medical devices affects cell response. Control of cell response has the potential to enhance fixation of implants into bone and, in other applications, to prevent undesired cell adhesion. The potential use of a 100W Q-switched YAG laser miller (DMG Lasertec 60 HSC) for texturing titanium is investigated. A series of regular features with dimensions of the order of tens of micrometers are generated in the surface of titanium samples and the cell response to these features is determined. Characterisation of the laser milled features reveals features with a lengthscale of a few microns superposed on the larger scale structures, this is attributed to resolidification of molten droplets generated and propelled over the surface by individual laser pulses. The laser textured samples are exposed to osteoblast cells and it is seen that cells do respond to the features in the laser textured surfaces.

  9. Nd:YAG-laser-based time-domain reflectometry measurements of the intrinsic reflection signature from PMMA fiber splices

    Science.gov (United States)

    Lawson, Christopher M.; Michael, Robert R., Jr.; Dressel, Earl M.; Harmony, David W.

    1991-12-01

    Optical time domain reflectometry (OTDR) measurements have been performed on polished polymethylmethacrylate (PMMA) plastic fiber splices. After the dominant splice reflection sources due to surface roughness, inexact index matching, and fiber core misalignment were eliminated, an intrinsic OTDR signature 3 - 8 dB above the Rayleigh backscatter floor remained with all tested fibers. This minimum splice reflectivity exhibits characteristics that are consistent with sub-surface polymer damage and can be used for detection of PMMA fiber splices.

  10. Characterizing Land Surface Anisotropic Reflectance over Rugged Terrain: A Review of Concepts and Recent Developments

    Directory of Open Access Journals (Sweden)

    Jianguang Wen

    2018-02-01

    Full Text Available Rugged terrain, including mountains, hills, and some high lands are typical land surfaces around the world. As a physical parameter for characterizing the anisotropic reflectance of the land surface, the importance of the bidirectional reflectance distribution function (BRDF has been gradually recognized in the remote sensing community, and great efforts have been dedicated to build BRDF models over various terrain types. However, on rugged terrain, the topography intensely affects the shape and magnitude of the BRDF and creates challenges in modeling the BRDF. In this paper, after a brief introduction of the theoretical background of the BRDF over rugged terrain, the status of estimating land surface BRDF properties over rugged terrain is comprehensively reviewed from a historical perspective and summarized in two categories: BRDFs describing solo slopes and those describing composite slopes. The discussion focuses on land surface reflectance retrieval over mountainous areas, the difference in solo slope and composite slope BRDF models, and suggested future research to improve the accuracy of BRDFs derived with remote sensing satellites.

  11. The effect of surface texture on total reflection of neutrons and X-rays from modified interfaces

    DEFF Research Database (Denmark)

    Goldar, A.; Roser, S.J.; Hughes, A.

    2002-01-01

    X-ray and neutron scattering from macroscopically rough surfaces and interfaces is considered and a new method of analysis based on the variation of the shape of the total reflection edge in the reflectivity profile is proposed. It was shown that in the limit that the correlation length and the h......X-ray and neutron scattering from macroscopically rough surfaces and interfaces is considered and a new method of analysis based on the variation of the shape of the total reflection edge in the reflectivity profile is proposed. It was shown that in the limit that the correlation length...... and the height of the surface roughness are larger than the wavelength (at least 100 times bigger) of the incoming beam, the total reflection edge in the reflection profile becomes rounded. This technique allows direct analysis of the variation of the reflectivity pro le in terms of the structure of the surface...

  12. Retrieval of the Land Surface Reflectance for Landsat-8 and Sentinel-2 and its validation.

    Science.gov (United States)

    Roger, J. C.; Vermote, E.; Skakun, S.; Franch, B.; Holben, B. N.; Justice, C. O.

    2017-12-01

    The land surface reflectance is a fundamental climate data record at the basis of the derivation of other climate data records (Albedo, LAI/Fpar, Vegetation indices) and a key parameter in the understanding of the land-surface-climate processes. For 25 years, Vermote and al. develop atmospheric corrections methods to define a land surface reflectance product for various satellites (AVHRR, MODIS, VIIRS…). This presentation highlights the algorithms developed both for Landsant-8 and Sentinel-2. We also emphasize the validation of the "Land surface reflectance" satellite products, which is a very important step to be done. For that purpose, we compared the surface reflectance products to a reference determined by using the accurate radiative transfer code 6S and very detailed measurements of the atmosphere obtained over the AERONET network (which allows to test for a large range of aerosol characteristics); formers being important inputs for atmospheric corrections. However, the application of this method necessitates the definition of a very detailed protocol for the use of AERONET data especially as far as size distribution and absorption are concerned, so that alternative validation methods or protocols could be compared. We describe here the protocol we have been working on based on our experience with the AERONET data and its application to Landsat-8 and Sentinel-2). We also derive a detailed error budget in relation to this approach. For a mean loaded atmosphere, t550 less than 0.25, the maximum uncertainty is 0.0025 corresponding to a relative uncertainty (in the RED channels): U 0.10, and 1% rsurf > 0.04.

  13. Reduction of Friction of Metals Using Laser-Induced Periodic Surface Nanostructures

    OpenAIRE

    Zhuo Wang; Quanzhong Zhao; Chengwei Wang

    2015-01-01

    We report on the effect of femtosecond-laser-induced periodic surface structures (LIPSS) on the tribological properties of stainless steel. Uniform periodic nanostructures were produced on AISI 304L (American Iron and Steel Institute steel grade) steel surfaces using an 800-nm femtosecond laser. The spatial periods of LIPSS measured by field emission scanning electron microscopy ranged from 530 to 570 nm. The tribological properties of smooth and textured surfaces with periodic nanostructures...

  14. Controlling the porosity of a polyethersulfone membrane surface with an XeCl laser

    International Nuclear Information System (INIS)

    Pazokian, Hedieh; Mehrabadi, Adeleh H P; Mollabashi, Mahmoud; Barzin, Jalal

    2016-01-01

    Pure and polyvinyl pyrrolidone blend polyethersulfone (PES) membranes were irradiated by an XeCl laser with various numbers of pulses at different fluences to investigate the changes in the surface morphology and the porosity. The results show that the membrane pore size and distribution on the surface can be modified following irradiation dependent on the laser fluence, the number of pulses and the membrane composition. These changes are very attractive for improving the membrane surface in filtration processes and biological applications. (paper)

  15. Electron emission from insulator surfaces by ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Acuna, M; Gravielle, M S, E-mail: mario@iafe.uba.a, E-mail: msilvia@iafe.uba.a [Institutes de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)

    2009-11-01

    Photoelectron emission from insulator surfaces induced by ultra-short laser pulses is studied within a time-dependent distorted wave method. The proposed approach combines the Volkov phase, which takes into account the laser interaction, with a simple representation of the unperturbed surface states, given by the Tight-binding method. The model is applied to evaluate the photoelectron emission from a LiF(001) surface, finding effects of interference produced by the crystal lattice.

  16. Improved Main Shaft Seal Life in Gas Turbines Using Laser Surface Texturing

    Science.gov (United States)

    McNickle, Alan D.; Etsion, Izhak

    2002-10-01

    This paper presents a general overview of the improved main shaft seal life in gas turbines using laser surface texturing (LST). The contents include: 1) Laser Surface Texturing System; 2) Seal Schematic with LST applied; 3) Dynamic Rig Tests; 4) Surface Finish Definitions; 5) Wear Test Rig; 6) Dynamic Test Rig; 7) Seal Cross Section-Rig Test; and 8) Typical Test Results. This paper is in viewgraph form.

  17. Laser surface graphitization to control friction of diamond-like carbon coatings

    Science.gov (United States)

    Komlenok, Maxim S.; Kononenko, Vitaly V.; Zavedeev, Evgeny V.; Frolov, Vadim D.; Arutyunyan, Natalia R.; Chouprik, Anastasia A.; Baturin, Andrey S.; Scheibe, Hans-Joachim; Shupegin, Mikhail L.; Pimenov, Sergei M.

    2015-11-01

    To study the role of laser surface graphitization in the friction behavior of laser-patterned diamond-like carbon (DLC) films, we apply the scanning probe microscopy (SPM) in the lateral force mode (LFM) which allows to obtain simultaneously the lateral force and topography images and to determine local friction levels in laser-irradiated and original surface areas. Based on this approach in the paper, we report on (1) laser surface microstructuring of hydrogenated a-C:H and hydrogen-free ta-C films in the regime of surface graphitization using UV laser pulses of 20-ns duration and (2) correlation between the structure and friction properties of the laser-patterned DLC surface on micro/nanoscale using SPM/LFM technique. The SPM/LFM data obtained for the surface relief gratings of graphitized microstructures have evidenced lower friction forces in the laser-graphitized regions. For the hydrogenated DLC films, the reversible frictional behavior of the laser-graphitized micropatterns is found to take place during LFM imaging at different temperatures (20 and 120 °C) in ambient air. It is revealed that the lateral force distribution in the laser-graphitized areas is shifted to higher friction levels (relative to that of the unirradiated surface) at temperature 120 °C and returned back to the lower friction during the sample cooling to 20 °C, thus confirming an influence of adsorbed water layers on the nanofriction properties of laser-graphitized micropatterns on the film surface.

  18. Surface Contaminant Control Technologies to Improve Laser Damage Resistance of Optics

    Directory of Open Access Journals (Sweden)

    Xiaofeng Cheng

    2014-01-01

    Full Text Available The large high-power solid lasers, such as the National Ignition Facility (NIF of America and the Shenguang-III (SG-III laser facility of China, can output over 2.1 MJ laser pulse for the inertial confinement fusion (ICF experiments. Because of the enhancement of operating flux and the expansion of laser driver scale, the problem of contamination seriously influences their construction period and operation life. During irradiation by intense laser beams, the contaminants on the metallic surface of beam tubes can be transmitted to the optical surfaces and lead to damage of optical components. For the high-power solid-state laser facilities, contamination control focuses on the slab amplifiers, spatial filters, and final-optical assemblies. In this paper, an effective solution to control contaminations including the whole process of the laser driver is put forward to provide the safe operation of laser facilities, and the detailed technical methods of contamination control such as washing, cleanliness metrology, and cleanliness protecting are also introduced to reduce the probability of laser-induced damage of optics. The experimental results show that the cleanliness level of SG-III laser facility is much better to ensure that the laser facility can safely operate at high energy flux.

  19. Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

    Science.gov (United States)

    Kumar, Sushil; Williams, Benjamin S.; Qin, Qi; Lee, Alan W. M.; Hu, Qing; Reno, John L.

    2007-01-01

    Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

  20. Light reflection from a rough liquid surface including wind-wave effects in a scattering atmosphere

    International Nuclear Information System (INIS)

    Salinas, Santo V.; Liew, S.C.

    2007-01-01

    Visible and near-IR images of the ocean surface, taken from remote satellites, often contain important information of near-surface or sub-surface processes, which occur on, or over the ocean. Remote measurements of near surface winds, sea surface temperature and salinity, ocean color and underwater bathymetry, all, one way or another, depend on how well we understand sea surface roughness. However, in order to extract useful information from our remote measurements, we need to construct accurate models of the transfer of solar radiation inside the atmosphere as well as, its reflection from the sea surface. To approach this problem, we numerically solve the radiative transfer equation (RTE) by implementing a model for the atmosphere-ocean system. A one-dimensional atmospheric radiation model is solved via the widely known doubling and adding method and the ocean body is treated as a boundary condition to the problem. The ocean surface is modeled as a rough liquid surface which includes wind interaction and wave states, such as wave age. The model can have possible applications to the retrieval of wind and wave states, such as wave age, near a Sun glint region

  1. Biomimetic approaches to create anti-reflection glass surfaces for solar cells using self-organizing techniques

    International Nuclear Information System (INIS)

    Achtelik, J.; Sievers, W.; Lindner, J.K.N.

    2013-01-01

    Highlights: ► Nanostructured glass surfaces with theoretically near-to-zero reflectivity in the UVNIR region. ► Simple fabrication process using self-organization during reactive ion etching proposed. ► Prediction of optical reflectivity from AFM measured surface morphology. -- Abstract: Aiming to diminish the reflection losses of glass covered light harvesting devices, the optical reflectivity of nanostructured glass surfaces is studied theoretically and experimentally. The work is inspired by the nanoscale roughness of insect eyes, which is tried to be replicated on a technical glass surface. To this end, the reflectivity of glass surfaces with topographies represented by linear, parabolic and Fermi-shaped glass/air fill factor profiles is calculated for normal incidence. It is shown that using the latter ones, an almost complete suppression of reflections can be achieved. A simple, self-organization technique to create such Fermi-shaped filling factor profiles in glass experimentally is also presented

  2. Biomimetic approaches to create anti-reflection glass surfaces for solar cells using self-organizing techniques

    Energy Technology Data Exchange (ETDEWEB)

    Achtelik, J.; Sievers, W. [University of Paderborn, Department of Physics, 33098 Paderborn (Germany); Center of Optoelectronics and Photonics Paderborn CeOPP, 33098 Paderborn (Germany); Lindner, J.K.N., E-mail: lindner@physik.uni-paderborn.de [University of Paderborn, Department of Physics, 33098 Paderborn (Germany); Center of Optoelectronics and Photonics Paderborn CeOPP, 33098 Paderborn (Germany)

    2013-05-15

    Highlights: ► Nanostructured glass surfaces with theoretically near-to-zero reflectivity in the UVNIR region. ► Simple fabrication process using self-organization during reactive ion etching proposed. ► Prediction of optical reflectivity from AFM measured surface morphology. -- Abstract: Aiming to diminish the reflection losses of glass covered light harvesting devices, the optical reflectivity of nanostructured glass surfaces is studied theoretically and experimentally. The work is inspired by the nanoscale roughness of insect eyes, which is tried to be replicated on a technical glass surface. To this end, the reflectivity of glass surfaces with topographies represented by linear, parabolic and Fermi-shaped glass/air fill factor profiles is calculated for normal incidence. It is shown that using the latter ones, an almost complete suppression of reflections can be achieved. A simple, self-organization technique to create such Fermi-shaped filling factor profiles in glass experimentally is also presented.

  3. Polycarbonate surface cell's adhesion examination after Nd:YAG laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ramazani, S.A. Ahmad, E-mail: Ramazani@sharif.ir [Polymer Group, Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Mousavi, Seyyed Abbas, E-mail: Musavi@che.sharif.ir [Department of Chemistry, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Seyedjafari, Ehsan [Department of Biotechnology, University College of Science, University of Tehran (Iran, Islamic Republic of); Poursalehi, Reza [Department of Physics, University of Shahed, Tehran (Iran, Islamic Republic of); Sareh, Shohreh [Research Center of Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Silakhori, Kaveh [Laser Research Center, Atomic Energy Organization, Tehran (Iran, Islamic Republic of); Poorfatollah, Ali Akbar [Research Center of Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Shamkhali, Amir Nasser [Department of Chemistry, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2009-05-05

    Nd:YAG laser treatment was used in order to increase surface cell adhesion aspects of polycarbonate (PC) films prepared via melt process. The treatment was carried out under different wavelengths and beam diameters. ATR-FTIR and UV spectra obtained from different samples before and after laser treatment in air showed that laser irradiation has induced some chemical and physical changes in surface properties. The irradiated films were also characterized using scanning electron microscopy (SEM) and contact angle measurements. Effect of pulse numbers on the surface properties was also investigated. Cell culture test was used to evaluate cell adhesion property on the PC films before and after treatment. The results obtained from this test showed that after laser treatment, the cells were attached and proliferated extensively on the Nd:YAG laser treated films in comparison with the unmodified PC. Moreover, it was revealed that a decrease in the laser beam diameter and an increase in the irradiated pulse numbers increased surface wettability and caused a better cell attachment on the polymer surface. The obtained results also showed that a decrease in the laser beam diameter and an increase in the irradiated pulse numbers increased surface wettability and caused a better cell attachment on the polymer surface.

  4. Comparison of KrF and ArF excimer laser treatment of biopolymer surface

    Energy Technology Data Exchange (ETDEWEB)

    Michaljaničová, I. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Heitz, J.; Barb, R.A. [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Sajdl, P. [Department of Power Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic)

    2015-06-01

    Highlights: • The influence of ArF and KrF laser on biopolymer surface was determined. • ArF laser acts predominantly on biopolymer surface. • PHB roughness is increased similarly for both applied wavelengths. • Roughness of nanostructures can be precisely controlled. • ArF laser introduces nitrogen on PHB surface. - Abstract: The goal of this work was the investigation of the impact of two different excimer lasers on two biocompatible and biodegradable polymers (poly-L-lactide and poly hydroxybutyrate). Both polymers find usage in medical and pharmaceutical fields. The polymers were modified by KrF and ArF excimer lasers. Subsequently the impact on surface morphology, surface chemistry changes, and thermal properties was studied by means of confocal and AFM microscopy, FTIR and XPS spectroscopy and DSC calorimetry. Under the same conditions of laser treatment it was observed that ArF laser causes more significant changes on surface chemistry, surface morphology and pattern formation on the polymers under investigation. The data obtained in this work can be used for a wide range of possible applications, in tissue engineering or in combination with metallization in electronics, e.g. for biosensors.

  5. Development of optical surface contouring technique using laser

    Energy Technology Data Exchange (ETDEWEB)

    Baik, Sung Hoon; Kim, Min Suk; Park, Seung Kyu

    1998-12-01

    Laser contouring system capable of measuring relief profiles using a line-shaped laser beam with anisotropic magnification optics composed with two cylindrical lenses was developed. The anisotropic magnification optical system allows it to obtain higher resolution in the relief profile measurements. The image processing and 3-D display software are developed to reconstruct 3-D shape. The power supply of laser diode with adaptive current control circuit is designed. (author). 4 refs., 5 tabs., 33 figs.

  6. The normalization of surface anisotropy effects present in SEVIRI reflectances by using the MODIS BRDF method

    DEFF Research Database (Denmark)

    Proud, Simon Richard; Zhang, Qingling; Schaaf, Crystal

    2014-01-01

    A modified version of the MODerate resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) algorithm is presented for use in the angular normalization of surface reflectance data gathered by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI...... acquisition period than the comparable MODIS products while, at the same time, removing many of the angular perturbations present within the original MSG data. The NBAR data are validated against reflectance data from the MODIS instrument and in situ data gathered at a field location in Africa throughout 2008....... It is found that the MSG retrievals are stable and are of high-quality across much of the SEVIRI disk while maintaining a higher temporal resolution than the MODIS BRDF products. However, a number of circumstances are discovered whereby the BRDF model is unable to function correctly with the SEVIRI...

  7. Self-consistent approach to x-ray reflection from rough surfaces

    International Nuclear Information System (INIS)

    Feranchuk, I. D.; Feranchuk, S. I.; Ulyanenkov, A. P.

    2007-01-01

    A self-consistent analytical approach for specular x-ray reflection from interfaces with transition layers [I. D. Feranchuk et al., Phys. Rev. B 67, 235417 (2003)] based on the distorted-wave Born approximation (DWBA) is used for the description of coherent and incoherent x-ray scattering from rough surfaces and interfaces. This approach takes into account the transformation of the modeling transition layer profile at the interface, which is caused by roughness correlations. The reflection coefficients for each DWBA order are directly calculated without phenomenological assumptions on their exponential decay at large scattering angles. Various regions of scattering angles are discussed, which show qualitatively different dependence of the reflection coefficient on the scattering angle. The experimental data are analyzed using the method developed

  8. Bio-inspired water repellent surfaces produced by ultrafast laser structuring of silicon

    International Nuclear Information System (INIS)

    Barberoglou, M.; Zorba, V.; Stratakis, E.; Spanakis, E.; Tzanetakis, P.; Anastasiadis, S.H.; Fotakis, C.

    2009-01-01

    We report here an efficient method for preparing stable superhydrophobic and highly water repellent surfaces by irradiating silicon wafers with femtosecond laser pulses and subsequently coating them with chloroalkylsilane monolayers. By varying the laser pulse fluence on the surface one can successfully control its wetting properties via a systematic and reproducible variation of roughness at micro- and nano-scale, which mimics the topology of natural superhydrophobic surfaces. The self-cleaning and water repellent properties of these artificial surfaces are investigated. It is found that the processed surfaces are among the most water repellent surfaces ever reported. These results may pave the way for the implementation of laser surface microstructuring techniques for the fabrication of superhydrophobic and self-cleaning surfaces in different kinds of materials as well

  9. Antarctic Surface Reflectivity Measurements from the ANITA-3 and HiCal-1 Experiments

    Science.gov (United States)

    Gorham, P. W.; Allison, P.; Banerjee, O.; Beatty, J. J.; Belov, K.; Besson, D. Z.; Binns, W. R.; Bugaev, V.; Cao, P.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Dailey, B.; Dasgupta, P.; Deaconu, C.; Cremonesi, L.; Dowkontt, P. F.; Fox, B. D.; Gordon, J.; Hill, B.; Hupe, R.; Israel, M. H.; Jain, P.; Kowalski, J.; Lam, J.; Learned, J. G.; Liewer, K. M.; Liu, T. C.; Matsuno, S.; Miki, C.; Mottram, M.; Mulrey, K.; Nam, J.; Nichol, R. J.; Novikov, A.; Oberla, E.; Prohira, S.; Rauch, B. F.; Romero-Wolf, A.; Rotter, B.; Ratzlaff, K.; Russell, J.; Saltzberg, D.; Seckel, D.; Schoorlemmer, H.; Stafford, S.; Stockham, J.; Stockham, M.; Strutt, B.; Tatem, K.; Varner, G. S.; Vieregg, A. G.; Wissel, S. A.; Wu, F.; Young, R.

    The primary science goal of the NASA-sponsored ANITA project is measurement of ultra-high energy neutrinos and cosmic rays, observed via radio-frequency signals resulting from a neutrino or cosmic ray interaction with terrestrial matter (e.g. atmospheric or ice molecules). Accurate inference of the energies of these cosmic rays requires understanding the transmission/reflection of radio wave signals across the ice-air boundary. Satellite-based measurements of Antarctic surface reflectivity, using a co-located transmitter and receiver, have been performed more-or-less continuously for the last few decades. Our comparison of four different reflectivity surveys, at frequencies ranging from 2 to 45GHz and at near-normal incidence, yield generally consistent maps of high versus low reflectivity, as a function of location, across Antarctica. Using the Sun as an RF source, and the ANITA-3 balloon borne radio-frequency antenna array as the RF receiver, we have also measured the surface reflectivity over the interval 200-1000MHz, at elevation angles of 12-30∘. Consistent with our previous measurement using ANITA-2, we find good agreement, within systematic errors (dominated by antenna beam width uncertainties) and across Antarctica, with the expected reflectivity as prescribed by the Fresnel equations. To probe low incidence angles, inaccessible to the Antarctic Solar technique and not probed by previous satellite surveys, a novel experimental approach (“HiCal-1”) was devised. Unlike previous measurements, HiCal-ANITA constitute a bi-static transmitter-receiver pair separated by hundreds of kilometers. Data taken with HiCal, between 200 and 600MHz shows a significant departure from the Fresnel equations, constant with frequency over that band, with the deficit increasing with obliquity of incidence, which we attribute to the combined effects of possible surface roughness, surface grain effects, radar clutter and/or shadowing of the reflection zone due to Earth

  10. Microjetting from grooved surfaces in metallic samples subjected to laser driven shocks

    Science.gov (United States)

    de Rességuier, T.; Lescoute, E.; Sollier, A.; Prudhomme, G.; Mercier, P.

    2014-01-01

    When a shock wave propagating in a solid sample reflects from a free surface, geometrical effects predominantly governed by the roughness and defects of that surface may lead to the ejection of tiny jets that may breakup into high velocity, approximately micrometer-size fragments. This process referred to as microjetting is a major safety issue for engineering applications such as pyrotechnics or armour design. Thus, it has been widely studied both experimentally, under explosive and impact loading, and theoretically. In this paper, microjetting is investigated in the specific loading conditions associated to laser shocks: very short duration of pressure application, very high strain rates, small spatial scales. Material ejection from triangular grooves in the free surface of various metallic samples is studied by combining transverse optical shadowgraphy and time-resolved velocity measurements. The influences of the main parameters (groove angle, shock pressure, nature of the metal) on jet formation and ejection velocity are quantified, and the results are compared to theoretical estimates.

  11. Microjetting from grooved surfaces in metallic samples subjected to laser driven shocks

    International Nuclear Information System (INIS)

    Rességuier, T. de; Lescoute, E.; Sollier, A.; Prudhomme, G.; Mercier, P.

    2014-01-01

    When a shock wave propagating in a solid sample reflects from a free surface, geometrical effects predominantly governed by the roughness and defects of that surface may lead to the ejection of tiny jets that may breakup into high velocity, approximately micrometer-size fragments. This process referred to as microjetting is a major safety issue for engineering applications such as pyrotechnics or armour design. Thus, it has been widely studied both experimentally, under explosive and impact loading, and theoretically. In this paper, microjetting is investigated in the specific loading conditions associated to laser shocks: very short duration of pressure application, very high strain rates, small spatial scales. Material ejection from triangular grooves in the free surface of various metallic samples is studied by combining transverse optical shadowgraphy and time-resolved velocity measurements. The influences of the main parameters (groove angle, shock pressure, nature of the metal) on jet formation and ejection velocity are quantified, and the results are compared to theoretical estimates

  12. Microjetting from grooved surfaces in metallic samples subjected to laser driven shocks

    Energy Technology Data Exchange (ETDEWEB)

    Rességuier, T. de, E-mail: resseguier@ensma.fr [Institut PPRIME, UPR 3346, CNRS, ENSMA, Université de Poitiers, 1 ave. Clément Ader, 86961 Futuroscope Cedex (France); Lescoute, E.; Sollier, A.; Prudhomme, G.; Mercier, P. [CEA, DAM, DIF, 91297 Arpajon (France)

    2014-01-28

    When a shock wave propagating in a solid sample reflects from a free surface, geometrical effects predominantly governed by the roughness and defects of that surface may lead to the ejection of tiny jets that may breakup into high velocity, approximately micrometer-size fragments. This process referred to as microjetting is a major safety issue for engineering applications such as pyrotechnics or armour design. Thus, it has been widely studied both experimentally, under explosive and impact loading, and theoretically. In this paper, microjetting is investigated in the specific loading conditions associated to laser shocks: very short duration of pressure application, very high strain rates, small spatial scales. Material ejection from triangular grooves in the free surface of various metallic samples is studied by combining transverse optical shadowgraphy and time-resolved velocity measurements. The influences of the main parameters (groove angle, shock pressure, nature of the metal) on jet formation and ejection velocity are quantified, and the results are compared to theoretical estimates.

  13. An investigation of phase transformation and crystallinity in laser surface modified H13 steel

    Science.gov (United States)

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2013-03-01

    This paper presents a laser surface modification process of AISI H13 tool steel using 0.09, 0.2 and 0.4 mm size of laser spot with an aim to increase hardness properties. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). X-ray diffraction analysis (XRD) was conducted to measure crystallinity of the laser-modified surface. X-ray diffraction patterns of the samples were recorded using a Bruker D8 XRD system with Cu K α ( λ=1.5405 Å) radiation. The diffraction patterns were recorded in the 2 θ range of 20 to 80°. The hardness properties were tested at 981 mN force. The laser-modified surface exhibited reduced crystallinity compared to the un-processed samples. The presence of martensitic phase was detected in the samples processed using 0.4 mm spot size. Though there was reduced crystallinity, a high hardness was measured in the laser-modified surface. Hardness was increased more than 2.5 times compared to the as-received samples. These findings reveal the phase source of the hardening mechanism and grain composition in the laser-modified surface.

  14. Energy loss of MeV protons specularly reflected from metal surfaces

    International Nuclear Information System (INIS)

    Juaristi, J.I.; Garcia de Abajo, F.J.; Echenique, P.M.

    1996-01-01

    A parameter-free model is presented to study the energy loss of fast protons specularly reflected from metal surfaces. The contributions to the energy loss from excitation of valence-band electrons and ionization of localized target-atom electronic states are calculated separately. The former is calculated from the induced surface wake potential using linear response theory and the specular-reflection model, while the latter is calculated in the first Born approximation. The results obtained are in good agreement with available experimental data. However, the experimental qualitative trend of the energy loss as a function of the angle of incidence is obtained when the valence-band electron model is replaced by localized target atom electron states, though with a worse quantitative agreement. copyright 1996 The American Physical Society

  15. Plasmonic reflectance anisotropy spectroscopy of metal nanoparticles on a semiconductor surface

    Science.gov (United States)

    Kosobukin, V. A.; Korotchenkov, A. V.

    2016-12-01

    A theory of plasmonic differential anisotropic reflection of light from nanoparticles located near the interface between media is developed. The model of a monolayer consisting of identical ellipsoidal metal particles occupying sites of a rectangular lattice is investigated. Effective plasmonic polarizabilities of nanoparticles in the layer are calculated self-consistently using the Green's function technique in the quasipoint dipole approximation. The local-field effect caused by anisotropic dipole plasmons of particles in the layer and their image dipoles is taken into account. The lately observed resonant reflectance anisotropy spectra of indium nanoclusters on InAs surface are explained by the difference between frequencies of plasmons with the orthogonal polarizations in the surface plane. The difference between the plasmon frequencies is attributed to anisotropy of the particles shape or/and the layer structure; the signs of frequency difference for the two types of anisotropy being different.

  16. Development of laser surface cladding through energy transmission over optical fiber

    International Nuclear Information System (INIS)

    Hirano, Kenji; Morishige, Norio; Irisawa, Toshio

    1990-01-01

    Much attention has recently been paid to laser cladding techniques as an approach in controlling the composition and structure of the metal surface. If YAG laser is used as the cladding method, the flexibility of laser cladding process increases extremely because YAG laser beam is transmitted through an optical fiber, and enabling cladding on pipes installed in actual plants. So experiments on YAG laser cladding through energy transmission over an optical fiber were performed to prevent stress corrosion cracking in austenitic stainless steel pipes. In order to build a cladding layer, mixed metal powder were pre-placed on the inner surface of the pipe using organic binder and the pre-placed powder beds were melted with YAG laser beam transmitted using an optical fiber. This paper introduces the method of building a cladding layer on pipes in actual nuclear plants. (author)

  17. Glazed ceramic roof tiles: influence of surface features in the solar reflectance index

    International Nuclear Information System (INIS)

    Bortoli, Leitcia Silva de; Stapait, Camila Cristina; Marinoski, Deivis Luis; Fredel, Marcio Celso; Schabbach, Luciana M.

    2016-01-01

    In this study the influence of surface features of ceramic roof tiles in the solar reflectance index were evaluated. Two glazed ceramic roof tiles (type stoneware) with the same color (ivory) but with different appearance (matte and brilliant) were the focus of the analysis. The Solar Reflectance Index (SRI) of the roofs tiles were determined by the solar reflectance values (UV-VIS-NIR) and emittance, measured in laboratory. The samples showed SRI> 39 in accordance with LEED certification criteria (Leadership in Energy and Environmental Design), contributing to minimizing the Heat Island Effects. Although the matte roof tile shows a slightly higher SRI value (82) than the brilliant one (78), the results for the variables that composes the SRI value (reflectance and emittance) were very similar. Analysis of XRD, SEM and EDS performed on the surfaces of the two roofs indicated for the matte glaze the presence of microcrystals (with barium and zinc) that can contribute to the slightly highest value of SRI. The roughness (optical interferometer white light) and the brightness (brightness meter) of the samples were also measured. (author)

  18. Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Primo, Gastón A.; Alvarez Igarzabal, Cecilia I. [IMBIV (CONICET), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Edificio de Ciencias II, Ciudad Universitaria, Córdoba X5000HUA (Argentina); Pino, Gustavo A.; Ferrero, Juan C. [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina); Rossa, Maximiliano, E-mail: mrossa@fcq.unc.edu.ar [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina)

    2016-04-30

    Graphical abstract: - Highlights: • Laser-induced surface modification of crosslinked hydrophilic co-polymers by ns pulses. • Formation of ablation craters observed under most of the single-pulse experimental conditions. • UV laser foaming of dried hydrogel samples resulting from single- and multiple-pulse experiments. • Threshold values of the incident laser fluence reported for the observed surface modifications. • Lower threshold fluences for acrylate-based, compared to acrylamide-based hydrogels. - Abstract: This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

  19. Anomalous Quasiparticle Reflection from the Surface of a ^{3}He-^{4}He Dilute Solution.

    Science.gov (United States)

    Ikegami, Hiroki; Kim, Kitak; Sato, Daisuke; Kono, Kimitoshi; Choi, Hyoungsoon; Monarkha, Yuriy P

    2017-11-10

    A free surface of a dilute ^{3}He-^{4}He liquid mixture is a unique system where two Fermi liquids with distinct dimensions coexist: a three-dimensional (3D) ^{3}He Fermi liquid in the bulk and a two-dimensional (2D) ^{3}He Fermi liquid at the surface. To investigate a novel effect generated by the interaction between the two Fermi liquids, the mobility of a Wigner crystal of electrons formed on the free surface of the mixture is studied. An anomalous enhancement of the mobility, compared with the case where the 3D and 2D systems do not interact with each other, is observed. The enhancement is explained by the nontrivial reflection of 3D quasiparticles from the surface covered with the 2D ^{3}He system.

  20. Absorption and reflectivity of the lithium niobate surface masked with a graphene layer

    Directory of Open Access Journals (Sweden)

    O. Salas

    2017-01-01

    Full Text Available We performed simulations of the interaction of a graphene layer with the surface of lithium niobate utilizing density functional theory and molecular dynamics at 300K and atmospheric pressure. We found that the graphene layer is physisorbed on the lithium niobate surface with an adsorption energy of -0.8205 eV/(carbon-atom. Subsequently, the energy band structure, the optical absorption and reflectivity of the new system were calculated. We found important changes in these physical properties with respect to the corresponding ones of a graphene layer and of a lithium niobate crystal.